Late Permian nautiloids from Baghuk Mountain (Central Iran)

Late Permian nautiloids from Baghuk Mountain (Central Iran) Dieter KORN 1,* & Vachik HAIRAPETIAN 2,* 1 Museum für Naturkunde, Leibniz Institut for Research on Evolution and Biodiversity, Invalidenstraße 43, 10115 Berlin, Germany. 2 Department of Geology, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran. * Corresponding authors: dieter[email protected], [email protected] Abstract. The Wuchiapingian to Changhsingian (Late Permian) Hambast Formation of sections at Baghuk Mountain and Shahreza (Central Iran) has yielded diverse nautiloid assemblages from the early Wuchiapingian Araxoceras beds (nine species), the early Wuchiapingian Prototoceras beds (one species), the late Wuchiapingian Vedioceras beds (twelve species) and the late Changhsingian Paratirolites beds (two species). These species belong to 14 genera, six of which are new: Lutonautilus gen. nov., Epitainoceras gen. nov., Ocunautilus gen. nov. in Ocunautilidae fam. nov., Aifinautilus gen. nov., Baghuknautilus gen. nov. and Shahrezanautilus gen. nov. A total of 24 species are described, all of which are new: Serometacoceras pentagonum sp. nov., Lutonautilus cratus gen. et sp. nov., Lutonautilus elachus gen. et sp. nov., Lutonautilus cymus gen. et sp. nov., Tainoceras hystatum sp. nov., Epitainoceras lutense gen. et sp. nov., Foordiceras eicosacanthum sp. nov., Foordiceras decacanthum sp. nov., Foordiceras ascetum sp. nov., Tardunautilus aperimos sp. nov., Domatoceras myloide sp. nov., Domatoceras canonium sp. nov., Domatoceras ocomphalum sp. nov., Ocunautilus diplodocus gen. et sp. nov., Ocunautilus coelodesmus gen. et sp. nov., Ocunautilus tachytrephus gen. et sp. nov., Aifinautilus icanus gen. et sp. nov., Azarinautilus phorminx sp. nov., Liroceras leptum sp. nov., Paraliroceras macrogaster sp. nov., Permonautilus adelphidus sp. nov., Baghuknautilus aplomorphus gen. et sp. nov., Shahrezanautilus weyeri gen. et sp. nov. and Shahrezanautilus ghaderii gen. et sp. nov. This nautiloid assemblage is remarkable for its high endemism. Although many genera known from the Transcaucasian region are represented, there is no correspondence at the species level. Keywords. Nautiloidea, Nautilida, Permian, Iran, morphology. Korn D. & Hairapetian V. 2025. Late Permian nautiloids from Baghuk Mountain (Central Iran). European Journal of Taxonomy 1019: 1–76. https://doi.org/10.5852/ejt.1019.3071 Introduction The faunal transition during the severe mass extinction event at the transition of the Palaeozoic into the Mesozoic is one of the major topics in the study of the evolutionary history of the biosphere, but nautiloids have so far played only a minor role in these studies. This under-representation of nautiloids may be due to the rather patchy state of knowledge; compared to other groups of fossil organisms, 1 European Journal of Taxonomy 1019: 1–76 https://doi.org/10.5852/ejt.2025.1019.3071 europeanjournaloftaxonomy.eu ISSN 2118-9773 2025 · Korn D. & Hairapetian V. This work is licensed under a Creative Commons Attribution License (CC BY 4.0) Received: 25 September 2024 • Accepted: 7 April 2025 • Published: 24 September 2025 Topic editor: Marie-Béatrice Forel • Desk editor: Kristiaan Hoedemakers Monograph urn:lsid:zoobank.org:pub:E24EBF4A-9FE2-47E4-A656-E1698F88BB41 nautiloids have rarely been monographically described and have therefore had little to contribute to the investigation of the largest mass extinction in the Phanerozoic. It has been shown in recent years that the discovery of new Carboniferous and Permian nautiloid assemblages has led to a significant increase in species numbers (Barskov et al. 2014; Niko & Mapes 2016a; Leonova & Shchedukhin 2020; Miao et al. 2021; Korn & Bockwinkel 2022; Korn et al. 2022; Korn & Klug 2023). Almost every new nautiloid assemblage has yielded predominantly new, previously unknown species. These recent studies have also shown that a stricter application of morphometric methods and more precise stratigraphic assignment can provide a much better insight into the evolutionary history of nautiloids. These studies have also led to improved insights into questions of ontogenetic development, intraspecific variation, and stratigraphic and geographic range. Late Permian coiled ammonoids were occasionally described in pioneering studies from various regions such as Saxony (Geinitz 1841), England (King 1850) and the Dolomites (Mojsisovics 1869; Stache 1877), but more diverse assemblages were known from only a few regions. Those from the former Armenian part of the Transcaucasus were the first ever described (Abich 1878; von Arthaber 1900), followed by the Salt Range in Pakistan (Waagen 1879) and South China (Kayser 1883). These pioneering studies have been complemented in a larger number of subsequent publications for the Transcaucasus (Shimansky 1965; Teichert & Kummel 1973), the Salt Range (Reed 1931, 1944), the Dolomites (Merla 1930; Prinoth & Posenato 2007) and South China (Zhao et al. 1978; Liang 1984; Zheng 1984; Miao et al. 2021). These studies have significantly improved our knowledge of nautiloids before the mass extinction at the Permian-Triassic boundary. An overview of their morphological range and morphospace occupation has already been obtained (Korn et al. 2020). It was not until the 1970s that Late Permian nautiloids from the territory of Iran became known. Teichert & Kummel (1973) described a number of taxa, mostly in open nomenclature, from around Julfa (NW Iran) and Taraz et al. (1981) listed some nautiloids from the Permian–Triassic boundary sections near Abadeh (central Iran). New finds in the Julfa area allowed Korn & Ghaderi (2025) to carry out a Fig. 1. Geographic position of Permian–Triassic boundary sections, including Baghuk Mountain, in Central Iran (from Korn et al. 2021b). European Journal of Taxonomy 1019: 1–76 (2025) 2 monographic study; 30 species from the Wuchiapingian and Changhsingian intervals were described in that monograph, 24 of them new. Here, we present a monographic description of the coiled nautiloids from the Wuchiapingian and Changhsingian formations of Baghuk Mountain. This monograph complements the previously published monograph on the fish remains (Hampe et al. 2013) and the monograph on the Changhsingian ammonoids (Korn et al. 2021a). In a parallel attempt, the coiled nautiloids from the Julfa region are described in another monograph (Korn & Ghaderi 2025). Material and methods A total of 55 nautilid specimens were studied. All but one of the specimens described here are from the Baghuk Mountain area 140 km SSE of Esfahan and 50 km NNW of Abadeh (Fig. 1). The individual sections of Baghuk Mountain have been described by Korn et al. (2021b) and Heuer et al. (2022). All the material comes from the Hambast Formation, which spans almost the entire Wuchiapingian and Changhsingian stages (Taraz et al. 1981). The majority of the specimens were collected from float material below the outcrops. However, all of the specimens described here can be assigned without doubt to a member of the Hambast Formation on the basis of their lithology. Four members were distinguished from bottom to top (Fig. 2): (1) Araxoceras beds (early Wuchiapingian): dark grey micritic nodular limestone (25 specimens). • Domatoceras myloide sp. nov. – 4 specimens • Ocunautilus diplodocus gen. et sp. nov. – 3 specimens Fig. 2. Stratigraphical positions of the Late Permian nautiloid taxa from Baghuk Mountain and Shahreza. Arax = Araxoceras beds; Prot = Prototoceras beds; Vedi = Vedioceras beds; Para = Paratirolites beds. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 3 • Ocunautilus coelodesmus gen. et sp. nov. – 3 specimens • Ocunautilus tachytrephus gen. et sp. nov. – 1 specimen • Aifinautilus icanus gen. et sp. nov. – 5 specimens • Serometacoceras pentagonum sp. nov. – 1 specimen • Epitainoceras lutense gen. et sp. nov. – 2 specimens • Paraliroceras macrogaster sp. nov. – 2 specimens • Permonautilus adelphidus sp. nov. – 4 specimens (2) Prototoceras beds (early Wuchiapingian): light grey platy limestone with numerous pyrite crystals (one specimen). • Tardunautilus aperimos sp. nov. – 1 specimen (3) Vedioceras beds (late Wuchiapingian): pink or light red nodular limestone (26 specimens). • Domatoceras canonium sp. nov. – 5 specimens • Domatoceras ocomphalum sp. nov. – 1 specimen • Foordiceras eicosacanthum sp. nov. – 2 specimens • Foordiceras decacanthum sp. nov. – 1 specimen • Foordiceras ascetum sp. nov. – 1 specimen • Lutonautilus cratus gen. et sp. nov. – 4 specimens • Lutonautilus elachus gen. et sp. nov. – 2 specimens • Lutonautilus cymus gen. et sp. nov. – 3 specimens • Liroceras leptum sp. nov. – 3 specimens • Baghuknautilus aplomorphus gen. et sp. nov. – 2 specimens • Shahrezanautilus weyeri gen. et sp. nov. – 1 specimen • Shahrezanautilus ghaderii gen. et sp. nov. – 1 specimen (4) Paratirolites beds (late Changhsingian): red-grey to grey-violet nodular limestone (three specimens). • Azarinautilus phorminx sp. nov. – 1 specimen • Tainoceras hystatum sp. nov. – 2 specimens Taxonomic concept For the order Nautilida in current understanding, several partially conflicting concepts of systematics have been published and modified over the decades. While Flower & Kummel (1950) and Kummel (1953, 1964) took a more conservative approach, Shimansky (1962a, 1962b, 1965, 1967) proposed a Fig. 3. Conch and suture line parameters used in the taxonomic descriptions. A. Conch parameters. B. Descriptive terms of whorl profiles. C. Suture line terminology. European Journal of Taxonomy 1019: 1–76 (2025) 4 much more detailed scheme. Dzik (1984) discussed the phylogeny and its implications for the systematic scheme in great detail and drew a much more complex evolutionary history of the coiled nautiloids. In a revision of the Carboniferous and Permian coiled nautiloids by Korn (2025), a new systematic scheme was presented. This scheme is largely based on the phylogenetic considerations of Ruzhencev & Shimansky (1954) as well as Dzik (1984) and is largely based, with some modifications, on the systematic scheme of Shimansky (1967, 1979). This also means that it differs from the often used scheme of the Treatise on Invertebrate Paleontology (Kummel 1964). The description of the specimens follows the terminology of conch, ornament and suture line proposed by Korn (2010) and Klug et al. (2015) for the characterisation of ammonoids (Fig. 3). The terminology of conch geometry used here largely corresponds to that proposed by Teichert (1964). The only differences concern the following terms: umbilical angle or shoulder (= umbilical margin) and umbilical area (= umbilical width in our descriptions). Photography technique The photographs for this monograph were taken using Reflectance Transformation Imaging (RTI) techniques with the Broncolor Scope D50 dome to create surface models without previously whitening the specimens. Processing of the images was performed using the Truvis Authentica Creator program. The exported images were processed in Adobe Photoshop. Abbreviations used in the species descriptions ah = apertural height CLI = chamber length index (in degrees) dm = conch diameter IZR = imprint zone rate uw = umbilical width WER = whorl expansion rate wh = whorl height ww = whorl width Abbreviation of the repository MB.C. = Cephalopod collection of the Museum für Naturkunde, Berlin Results Class Cephalopoda Cuvier, 1795 Subclass Nautiloidea Agassiz, 1847 Order Nautilida Agassiz, 1847 Diagnosis Exogastrically curved or coiled nautiloids with a conch shape ranging from gyroconic or cyrtoconic to more or less tightly coiled. Shell surface smooth or sculptured with a variety of elements (ribs, nodes, spines, longitudinal ridges or lines). Septa simply domed in most species, with the shape of the whorl profile producing suture lines with variable lobes and saddles. Variations in septal shape with inflexions producing deep lobes in some genera. Septal necks short and straight, rarely slightly widened. Connecting rings cylindrical or beaded. Siphuncular or cameral deposits absent. Juvenile conch with cup-shaped initial chamber and narrow siphuncle. Morphological evolution includes the degree of coiling, the shape and size of the juvenile and adult conch and the suture line (after Shimansky 1962b; emended). KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 5 Included suborders Nautilina Agassiz, 1847 (Jurassic to Recent); Solenochilina Flower, 1950 (Carboniferous to Permian); Liroceratina Flower, 1955 (Carboniferous to Jurassic); Rutoceratina Shimansky, 1957 (Devonian); Tainoceratina Shimansky, 1957 (Carboniferous to Triassic); Temnocheilina Flower, 1963 (Devonian to Permian); Domatoceratina Korn, 2025 (Carboniferous to Triassic). Suborder Domatoceratina Korn, 2025 Diagnosis Suborder of the order Nautilida, in which a ventrolateral shoulder and an umbilical margin are formed early in ontogeny. Conch usually discoidal, subinvolute to evolute. Juvenile whorl profile circular. Adult whorl profile subquadrate or inverted trapezoidal with a distinct ventrolateral shoulder and a distinct umbilical margin in the early species, showing modifications during evolution including a concave venter in some derived species. Dorsal whorl zone always present, but usually very small except for some derived species. Juvenile sculpture sometimes with radial ribs on the flank; adult sculpture is usually lacking except for elongate ventrolateral tubercles in derived species. Septa simply domed in most of the species; with septal inflexion and corrugated septa in some lineages. Suture line usually depending on the whorl profile, usually with shallow lobes and low saddles; with distinct lobes in some derived lineages (from Korn 2025). Included superfamilies Grypoceratoidea Hyatt, 1900 (Carboniferous to Triassic); Permoceratoidea Miller & Collinson, 1953 (Permian); Subclymenioidea Shimansky, 1962 (Carboniferous). Remarks A detailed discussion of the Domatoceratina has been given by Korn (2025). Superfamily Grypoceratoidea Hyatt, 1900 Diagnosis Superfamily of the suborder Domatoceratina with a discoidal, subinvolute to evolute conch. Whorl profile usually inverted trapezoidal with a distinct ventrolateral shoulder and a distinct umbilical margin. Derived species show a variation of modifications including a concave venter, a skid-like ventrolateral shoulder and an angular umbilical margin. Whorl overlap extremely small to moderate. Sculpture in most species lacking, in some species with short lateral ribs or ventrolateral nodes. Septa simply domed; suture line strongly dependent on the whorl profile, usually with broadly rounded lobes and narrowly rounded or subangular saddles (from Korn 2025). Included families Grypoceratidae Hyatt, 1900; Domatoceratidae Miller & Youngquist, 1949; Ocunautilidae fam. nov. Remarks A discussion of the Grypoceratoidea has been given by Korn (2025). Family Domatoceratidae Miller & Youngquist, 1949 Diagnosis Family of the superfamily Grypoceratoidea with a thinly to thickly discoidal, subinvolute to evolute conch. Whorl profile in the adult stage usually compressed subquadrate or inverted trapezoidal. Umbilical European Journal of Taxonomy 1019: 1–76 (2025) 6 margin distinct or sharp; ventrolateral shoulder nearly rectangular to broadly rounded, rarely skid-like. Ornament consisting of fine growth lines; some species have tubercles on the ventrolateral shoulder. Suture line always with rounded but distinct external, lateral and internal lobes separated by a narrowly rounded or subacute saddles; without annular process (from Korn 2025). Included genera Pselioceras Hyatt, 1884 (Permian); Titanoceras Hyatt, 1884 (Carboniferous); Domatoceras Hyatt, 1891 (Carboniferous to Permian); Pseudometacoceras Miller, Dunbar & Condra, 1933 [synonym of Domatoceras Hyatt, 1891]; Paradomatoceras Delépine, 1937 (Carboniferous); Plummeroceras Kummel, 1953 (Permian); Neodomatoceras Ruzhencev & Shimansky, 1954 (Permian); Neostenopoceras Zhao, Liang & Zheng, 1978 (Permian); Parapenascoceras Ruzhencev & Shimansky, 1954 (Permian); Parastenopoceras Ruzhencev & Shimansky, 1954 (Permian); Penascoceras Ruzhencev & Shimansky, 1954 (Permian); Permodomatoceras Ruzhencev & Shimansky, 1954 (Permian); Stenodomatoceras Ruzhencev & Shimansky, 1954 (Permian); Virgaloceras Schindewolf, 1954 (Permian); Neostenopoceras Zhao, Liang & Zheng, 1978 (Permian); Shatoceras Leonova & Shchedukhin, 2020 (Permian); Omorphoceras Leonova & Shchedukhin, 2023 (Permian); Fididomatoceras Korn & Ghaderi, 2025 (Permian). Remarks A detailed discussion of the Domatoceratidae has been given by Korn (2025). Genus Domatoceras Hyatt, 1891 Type species Domatoceras umbilicatum Hyatt, 1891; original designation. Diagnosis Genus of the family Domatoceratidae with a subinvolute to evolute conch. High to extremely high coiling rate; whorl profile usually weakly compressed. Venter flattened or weakly concave, flanks usually flattened and slightly convergent; umbilical margin rounded or angular. Without sculpture except for small ventrolateral tubercles in some species. Suture line with small and shallow external lobe and broadly rounded lateral lobe; without annular process. Included Carboniferous species North America (Meek & Worthen 1865; Worthen & Meek 1875; Gurley 1883; Hyatt 1891; Miller & Owen 1934; Sturgeon & Miller 1948; Tucker 1976; Tucker & Mapes 1978; Sturgeon et al. 1982; Niko & Mapes 2016b; Niko et al. 2022): Nautilus Lasallensis Meek & Worthen, 1865, Kasimovian, Illinois; Nautilus (Discites) highlandensis Worthen in Worthen & Meek, 1875, Moscovian, Ohio; Discites Toddanus Gurley, 1883, Kasimovian, Missouri; Domatoceras umbilicatum Hyatt, 1891, Moscovian, Kansas; Domatoceras williamsi Miller & Owen, 1934, Moscovian, Ohio; Domatoceras obsoletum Sturgeon, 1946, Moscovian, Ohio; Domatoceras shepherdi Sturgeon, 1948, Moscovian, Ohio; Domatoceras wortheni Tucker, 1976, Kasimovian, Illinois; Domatoceras texanum Tucker & Mapes, 1978, Kasimovian, Texas; Domatoceras oreskovichi Sturgeon, Windle, Mapes & Hoare, 1982, Moscovian, Ohio; Domatoceras collinsvillense Niko & Mapes, 2016, Moscovian, Oklahoma; Domatoceras tuckeri Niko, Mapes & Seuss, 2022, Kasimovian, Texas. South China (Ruan & Zhou 1987): Domatoceras quadratum Ruan & Zhou, 1987, Bashkirian, Ningxia. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 7 West Russia (Tzwetaev 1888, 1898; Shimansky 1967): Nautilus podolskensis Tzwetaev, 1888, Moscovian, Moscow Basin; Nautilus mosquensis Tzwetaev, 1898, Moscovian, Moscow Basin; Domatoceras (Domatoceras) magister Shimansky, 1967, Moscovian, Moscow Basin. Included Permian species Urals (Leonova & Shchedukhin 2020): Domatoceras bashkiricum Leonova & Shchedukhin, 2020, Asselian or Sakmarian, South Urals; Domatoceras sterlitamakense Leonova & Shchedukhin, 2020, Asselian or Sakmarian, South Urals. Transcaucasia and Iran (Abich 1878; Shimansky 1965; this paper): Nautilus parallelus Abich, 1878, Wuchiapingian, Azerbaijan; Nautilus convergens Abich, 1878, Wuchiapingian, Azerbaijan; Domatoceras gracile Shimansky, 1965, Wuchiapingian, Azerbaijan; Domatoceras atypicum Shimansky, 1965, Wuchiapingian, Azerbaijan; Domatoceras multituberculatum Korn & Ghaderi, 2025, Wuchiapingian, NW Iran; Domatoceras canonium sp. nov., Wuchiapingian, Central Iran; Domatoceras ocomphalum sp. nov., Wuchiapingian, Central Iran; Domatoceras myloide sp. nov., Wuchiapingian, Central Iran. South China (Zhao et al. 1978): Domatoceras guangxiense Zhao, Liang & Zheng, 1978, Changhsingian, Guangxi. Japan (Ehiro & Takizawa 1989): Domatoceras ogatsuense Ehiro & Takizawa, 1989, Wuchiapingian, Kitakami Massif. Remarks The species of the genus Domatoceras have a very similar conch morphology from the Moscovian to the Changhsingian, suggesting a very conservative evolutionary lineage. Shimansky (1967) also included some Serpukhovian species in Domatoceras, but these differ from the typical representatives of the genus in that they have a wider conch and lack a subangular or angular ventrolateral shoulder. These stratigraphically older species may belong to Epidomatoceras Turner, 1954. The similarity in the morphology of the conchs, the virtual absence of sculptural elements and the fact that the suture line depends essentially on the shape of the whorl profile make it difficult to distinguish the species within Domatoceras. Another difficulty is that the species of the genus occur in two phases: the first phase extends from the Moscovian to the Asselian–Sakmarian boundary, and the second phase extends from the Wuchiapingian to the Changhsingian. It should be noted, however, that of the Late Permian species, about ten are known from the Wuchiapingian and only one from the Changhsingian. Apparently, no species are known from the long interval between the Sakmarian and the Capitanian. Some species from the Kungurian and Roadian, which were placed under Domatoceras by Miller & Unklesbay (1942) and Miller & Youngquist (1949), have been assigned to other genera such as Penascoceras by Ruzhencev & Shimansky (1954). Domatoceras myloide sp. nov. urn:lsid:zoobank.org:act:78A31C35-C06A-4B4C-9A86-137219AC51C5 Fig. 4; Table 1 Diagnosis Species of Domatoceras with thinly discoidal, subevolute conch (ww/dm ~ 0.35; uw/dm ~ 0.35), weakly compressed whorl profile (ww/wh ~ 0.90) and very high coiling rate (WER ~ 2.45) at a conch diameter of 70 mm. Whorl profile with weakly flattened venter, rounded ventrolateral shoulder, flattened and nearly parallel flanks, subangular umbilical margin and steep and flat umbilical wall. Whorl overlap very small. Without sculpture. Suture line with a small and very shallow external lobe and a much larger and deeper, broadly rounded lateral lobe. European Journal of Taxonomy 1019: 1–76 (2025) 8 Etymology From the Greek ‘μυλοειδής’ = ‘millstone-shaped’; because of the conch shape. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 4; MB.C.32101. Paratypes IRAN – Esfahan Province • 3 specimens; same data as for holotype; 2010; Korn et al. leg.; MB.C.32102 to MB.C.32104. Description Holotype MB.C.32101 is a fully chambered internal mould specimen with a conch diameter of 72 mm, which allows the study of one whorl (Fig. 4B). The conch is thinly discoidal and subevolute (ww/ dm = 0.35; uw/dm = 0.34) with an extremely high coiling rate (WER = 2.47); the whorl profile is weakly compressed (ww/wh = 0.90) with a weakly flattened venter, a rounded ventrolateral shoulder, flattened Fig. 4. Domatoceras myloide sp. nov., holotype MB.C.32101 (Korn et al. 2011 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Dorsal, lateral and ventral views. C. Suture line at dm = 68.5 mm, ww = 22.5 mm, wh = 26.5 mm. Scale bar units = 1 mm. Table 1. Conch dimensions (in mm) and ratios of Domatoceras myloide sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32101 72.1 25.0 27.8 24.6 26.2 0.35 0.90 0.34 2.47 0.06 MB.C.32101 47.2 17.3 19.2 16.0 18.2 0.37 0.90 0.34 2.65 0.05 MB.C.32102 56.3 20.2 21.5 20.5 20.5 0.36 0.94 0.36 2.47 0.05 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 9 Remarks Ocunautilus gen. nov. can hardly be confused with any other genus of Late Permian nautilids because of its very characteristic conch shape. The rather sharp umbilical margin, the flattened and rapidly converging flanks, the angular, skid-like ventrolateral shoulder and the more or less clearly concave venter allow a clear separation. Pseudotitanoceras is similar to Ocunautilus, but this genus is distinguished by the presence of tubercles on the ventrolateral shoulder. Shimansky (1965) mentioned that among his P. armeniacum material there were also specimens without ventrolateral tubercles. Perhaps these do belong to Ocunautilus rather than Pseudotitanoceras. Ocunautilus diplodocus gen. et sp. nov. urn:lsid:zoobank.org:act:46279074-DA8A-42D6-B45C-8C639250C01A Fig. 8; Table 4 Diagnosis Species of Ocunautilus gen. nov. with thinly discoidal, subinvolute conch (ww/dm ~ 0.42; uw/dm ~ 0.20), weakly compressed whorl profile (ww/wh ~ 0.85) and extremely high coiling rate (WER ~ 2.95) at a conch diameter of 100 mm. Whorl profile inverted trapezoidal with deeply concave venter, angular ventrolateral shoulder, flattened and weakly convergent flanks, angular umbilical margin and steep and weakly concave umbilical wall. Whorl overlap small (IZR ~ 0.12). Without sculpture. Suture line with a very deep, rounded V-shaped external lobe, an angular ventrolateral saddle, a shallow and broadly rounded lateral lobe and a very small umbilical lobe. Etymology From the Greek ‘διπλόος’ = ‘double’ and ‘ὀξύς’ = ‘sharp’; because of the double-keeled venter. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2013; Korn et al. leg.; illustrated in Fig. 8; MB.C.32110. Paratypes IRAN – Esfahan Province • 2 specimens; same data as for holotype; 2010; Korn et al. leg.; MB.C.32111, MB.C.32112. Description Holotype MB.C.32110 is a fragment showing slightly more than a quarter whorl of the phragmocone and a poorly preserved piece of the penultimate whorl (Fig. 8A). The fragment has a maximum whorl height of 51 mm; from this, a diameter of 105 mm can be reconstructed. On the basis of this calculated diameter, the conch parameters can be determined. The conch is thinly discoidal and subinvolute (ww/ dm ~ 0.42; uw/dm ~ 0.21) with an extremely high coiling rate (WER ~ 2.96). The whorl profile is weakly compressed (ww/wh = 0.87) with a deeply concave venter that is bordered by a sharp, skid-like ventrolateral shoulder; the flanks are flattened and convergent. Most conspicuous is the angular umbilical margin, which borders the weakly concave, incurved umbilical wall (Fig. 8B). The whorl overlap is small (IZR = 0.14). The specimen does not show any sculpture. The suture line is strongly influenced by the outline of the whorl profile; it is characteristic because of the narrow and deep, V-shaped external lobe, which is separated from the broadly rounded lateral lobe by a subangular ventrolateral saddle (Fig. 8C). The last quarter volution of the phragmocone consists of seven chambers (CLI = 13); there occurs weak septal approximation toward the aperture. European Journal of Taxonomy 1019: 1–76 (2025) 16 Remarks Ocunautilus diplodocus gen. et sp. nov. differs from the other two species O. coelodesmus gen. et sp. nov. and O. tachytrephus gen. et sp. nov. from Baghuk Mountain by the much more deeply concave venter; accordingly, the external lobe of O. diplodocus is also much deeper and narrower. Fig. 8. Ocunautilus diplodocus gen. et sp. nov., holotype MB.C.32110 (Korn et al. 2013 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Ventral and lateral views. B. Reconstruction of apertural view. C. Suture line at ww = 42.5 mm, wh = 46.0 mm. Scale bar units = 1 mm. Table 4. Conch dimensions (in mm) and ratios of Ocunautilus diplodocus gen. et sp. nov.; reconstructed values in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32110 105.0 44.5 50.9 22.5 44.0 0.42 0.87 0.21 2.96 0.14 MB.C.32111 84.0 32.2 38.2 23.3 34.4 0.38 0.84 0.28 2.87 0.10 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 17 Ocunautilus coelodesmus gen. et sp. nov. urn:lsid:zoobank.org:act:FC07FF9A-4B9C-4162-8BFD-9B43A2E3052C Fig. 9; Table 5 Diagnosis Species of Ocunautilus gen. nov. with thickly discoidal, subinvolute conch (ww/dm ~ 0.55; uw/dm ~ 0.25), weakly depressed whorl profile (ww/wh ~ 1.10) and extraordinarily high coiling rate (WER ~ 3.40) at a conch diameter of 60 mm. Whorl profile inverted trapezoidal with moderately concave venter, subangular ventrolateral shoulder, flattened and strongly convergent flanks, angular umbilical margin and steep and flat umbilical wall. Whorl overlap small (IZR ~ 0.08). Without sculpture, but juvenile conch with weak, backwardly directed ribs on the inner flank, ending in low and blunt nodes on the midflank. Suture line with a rather deep, rounded V-shaped external lobe, an angular ventrolateral saddle, a shallow and broadly rounded lateral lobe and a very small umbilical lobe. Etymology From the Greek ‘κόιλος’ = ‘hollow’ and ‘δεσμός’ = ‘band, brace’; because of the shape of the venter. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 9; MB.C.32113. Paratypes IRAN – Esfahan Province • 1 specimen; same data as for holotype; MB.C.32114. Description Holotype MB.C.32113 is an incomplete, almost fully chambered specimen with a conch diameter of 57 mm (Fig. 9B). It is preserved as an internal mould, but shows some shell remains. The conch is, at a conch diameter of 57 mm, thickly discoidal and subinvolute (ww/dm = 0.55; uw/dm = 0.23) with an extraordinarily high coiling rate (WER = 3.38). There occurs an ontogenetic decrease of the coiling rate; Fig. 9. Ocunautilus coelodesmus gen. et sp. nov., holotype MB.C.32113 (Korn et al. 2011 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Lateral and ventral views. C. Suture line at dm = 37.0 mm, ww = 22.2 mm, wh = 19.6 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 18 at a conch diameter of 37.5 mm, it has even a value of 3.70. The whorl profile is weakly depressed (ww/ wh = 1.12) with a weakly concave venter that is bordered by a sharp ventrolateral shoulder; the flanks are nearly flat and strongly convergent. The umbilical margin is subangular and the umbilical wall is steep and flat (Fig. 9A). The whorl overlap is small (IZR = 0.08). The few preserved shell remains of the holotype show no ornamentation or sculpture. The internal mould, however, has very small tubercles on the angular ventrolateral shoulder in the preadult stage up to a diameter of about 35 mm. The flanks bear very shallow, from the umbilical margin backwardly directed ribs, which strengthen in the middle of the flank to form very low, broad conical nodes. The suture line is dependent on the cross-sectional shape of the whorl; it has a rather deep, rounded V-shaped external lobe, an angular saddle on the ventrolateral shoulder and a broadly rounded lateral lobe (Fig. 9C). The last quarter volution of the phragmocone has about seven chambers (CLI = 13). Remarks Ocunautilus coelodesmus gen. et sp. nov. occupies an intermediate position between O. diplodocus gen. et sp. nov. and O. tachytrephus gen. et sp. nov. as far as the concavity of the venter is concerned; in O. diplodocus the venter is much more deeply concave and in O. tachytrephus it is nearly flat. Ocunautilus coelodesmus gen. et sp. nov. has very similar conch proportions to O. tachytrephus, but differs in the concave umbilical wall, which is weakly convex in O. tachytrephus. Ocunautilus tachytrephus gen. et sp. nov. urn:lsid:zoobank.org:act:3C21BF76-5C82-4F5E-B39F-43499C76950D Fig. 10; Table 6 Diagnosis Species of Ocunautilus gen. nov. with thickly discoidal, subinvolute conch (ww/dm ~ 0.50; uw/dm ~ 0.25), weakly depressed whorl profile (ww/wh ~ 1.10) and extraordinarily high coiling rate (WER ~ 3.35) at a conch diameter of 80 mm. Whorl profile inverted trapezoidal with weakly concave venter, angular ventrolateral shoulder, flattened and weakly convergent flanks, angular umbilical margin and steep and weakly convex, flattened umbilical wall. Whorl overlap very small (IZR ~ 0.04). Without sculpture, but first whorl with low, blunt nodes on the ventrolateral shoulder. Suture line with a very shallow external lobe, a subangular ventrolateral saddle, a shallow and broadly rounded lateral lobe and a very small umbilical lobe. Etymology From the Greek ‘ταχύς’ = ‘rapid’ and ‘τρέφω’ = ‘enlarge’; because of the high coiling rate. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 10; MB.C.32115. Table 5. Conch dimensions (in mm) and ratios of Ocunautilus coelodesmus gen. et sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32113 57.0 31.5 28.2 12.9 26.0 0.55 1.12 0.23 3.38 0.08 MB.C.32113 37.5 21.3 19.4 9.5 18.0 0.57 1.10 0.25 3.70 0.07 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 19 Description Holotype MB.C.32115 is a fully chambered, partially corroded specimen with a conch diameter of 85 mm (Fig. 10A). It has slightly more than two volutions; the first volution has a diameter of about 24 mm and an umbilical foramen of about 4 mm diameter. The conch is, at a conch diameter of 85 mm, thickly discoidal and subinvolute (ww/dm = 0.51; uw/dm = 0.24) with an extraordinarily high coiling rate (WER = 3.35). Measurements from a position half a volution before result in similar ratios of conch geometry, but there occurs an ontogenetic decrease of the coiling rate; at a conch diameter of 48 mm, it has a value of about 3.50. The whorl profile is weakly depressed (ww/wh = 1.08) with a very weakly concave venter that is bordered by a sharp ventrolateral shoulder; the flanks are nearly flat and convergent. The umbilical margin is angular and the umbilical wall is steep and weakly convex. The whorl overlap is very small (IZR = 0.04). The specimen shows that the venter is still convex at a conch diameter of 24 mm, although it is already slightly flattened; the venter is completely applanate at a conch diameter of 48 mm (Fig. 10B). The conch is largely free of sculpture and ornament. On the first half of the last volution, the ventrolateral shoulder bears very low and blunt conical nodes. The suture line extends with a broadly rounded external lobe, a subangular ventrolateral saddle, a shallow lateral lobe and a very small umbilical lobe (Fig. 10C). Remarks Ocunautilus tachytrephus gen. et sp. nov. differs from the other two species O. diplodocus gen. et sp. nov. and O. coelodesmus gen. et sp. nov. from Baghuk Mountain in the shape of the umbilical wall (convex in O. tachytrephus, but concave in the other species) and in the only weakly developed concavity of the venter. Ocunautilus tachytrephus has similar conch proportions as O. coelodesmus, but shows a flattening Fig. 10. Ocunautilus tachytrephus gen. et sp. nov., holotype MB.C.32115 (Korn et al. 2011 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Lateral and dorsal views. B. Reconstruction of apertural view. C. Suture line at ww = 23.5 mm, wh = 22.4 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 20 of the venter only at a larger conch diameter. This flattening occurs at about 35 mm in O. tachytrephus, but already at about 20 mm in O. coelodesmus. Pseudotitanoceras armeniacus (Abich, 1878) has similar conch proportions, but differs from O. tachytrephus gen. et sp. nov. by a distinctly concave venter as well as the presence of tubercles on the ventrolateral shoulder and umbilical margin. Some of the specimens without tubercles mentioned by Shimansky (1965) may belong to O. coelodesmus gen. et sp. nov. Genus Aifinautilus gen. nov. urn:lsid:zoobank.org:act:C251419E-4EF4-4D59-BBAA-FEEA876287CC New genus B – Korn 2025: 43. — Korn & Ghaderi 2025: 30. Type species Aifinautilus icanus gen. et sp. nov. Diagnosis Genus of the family Ocunautilidae fam. nov. with a subinvolute conch. High coiling rate; whorl profile rounded rectangular, weakly depressed with concave venter. Without sculpture. Suture line with shallow external lobe and broadly rounded lateral lobe; without annular process. Etymology From the Greek ‘αἴφνης’ = ‘suddenly, unexpected’; because of the unexpected conch form of a Permian nautiloid. Included species NW Iran (Korn & Ghaderi 2025): Aifinautilus hebes Korn & Ghaderi, 2025, Wuchiapingian. Central Iran (this paper): Aifinautilus icanus gen. et sp. nov., Wuchiapingian. Remarks Aifinautilus gen. nov. is difficult to confuse with any other genus of Palaeozoic nautiloids because of its peculiar conch morphology with the box-shaped whorl profile, the concave venter, the skid-like ventrolateral shoulder, parallel flanks and flattened umbilical wall. Ocunautilus gen. nov. differs from Aifinautilus by its clearly convergent flanks, resulting in a much narrower venter; it has an angular ventrolateral shoulder and an angular umbilical margin. Pseudotitanoceras also has convergent flanks and is characterised by a row of nodes on the ventrolateral shoulder and sometimes also at the umbilical margin (Shimansky 1965: 163). The conch of Aifinautilus gen. nov. is very similar to that of some species of the Triassic genus Germanonautilus Mojsisovics, 1902 (e.g., Mojsisovics 1902; Dzik 1984; Sobolev 1989). The main difference between the two genera is the presence of an annular lobe in Germanonautilus, which is absent in Aifinautilus. The siphuncle has a more dorsal position in Germanonautilus. Table 6. Conch dimensions (in mm) and ratios of Ocunautilus tachytrephus gen. et sp. nov.; reconstructed values in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32115 85.0 43.5 40.1 20.8 38.6 0.51 1.08 0.24 3.35 0.04 MB.C.32115 48.4 25.4 23.4 12.4 22.5 0.52 1.09 0.26 3.49 0.04 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 21 The Late Carboniferous genus Titanoceras has a superficially similar conch shape with a concave venter and almost parallel flanks. However, the conch of Titanoceras has almost non-overlapping whorls and the sculpture is characterised by ventrolateral tubercles. Shimansky (1965: 163) has already suggested that the Late Carboniferous (Titanoceras) and Late Permian forms (Pseudotitanoceras) belong to two independent, homoeomorphic evolutionary lineages and that both arose from Domatoceras. Aifinautilus icanus gen. et sp. nov. urn:lsid:zoobank.org:act:8E2C5B5B-1C6B-4492-8D76-89F957B1DCC1 Figs 11–13; Table 7 Diagnosis Species of Aifinautilus gen. nov. with thickly discoidal, subinvolute conch (ww/dm ~ 0.50; uw/dm ~ 0.25), weakly depressed whorl profile (ww/wh ~ 1.10) and very high coiling rate (WER ~ 2.30) at a conch diameter of 110 mm. Whorl profile with weakly concave venter, rounded ventrolateral shoulder, weakly convergent flanks, rounded umbilical wall, weakly concave umbilical wall and moderately deep imprint zone (IZR ~ 0.25). Without sculpture. Suture line with a very shallow external lobe and a very shallow lateral lobe. Fig. 11. Aifinautilus icanus gen. et sp. nov., holotype MB.C.32116 (Korn et al. 2010 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain, ventral and lateral views. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 22 Etymology From the Greek ‘ἱκανός‘ = ‘competent’; because of the robust conch. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2010; Korn et al. leg.; illustrated in Figs 11–12; MB.C.32116. Paratypes IRAN – Esfahan Province • 1 specimen; same data as for holotype; 2011; Korn et al. leg.; illustrated in Fig. 13; MB.C.32117 • 3 specimens; same data as for holotype; 2011; Korn et al. leg.; MB.C.32118 to MB.C.32120. Fig. 12. Aifinautilus icanus gen. et sp. nov., holotype MB.C.32116 (Korn et al. 2010 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Dorsal view. B. Reconstruction of apertural view. C. Suture line at dm = 105 mm, ww = 53 mm, wh = 47 mm. Scale bar units = 1 mm. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 23 Description Holotype MB.C.32116 is an almost complete, but partially corroded specimen with a conch diameter of 114 mm (Figs 11, 12A). It is largely chambered; only a small part of the specimen belongs to the body chamber. The conch is, at a conch diameter of 114 mm, thickly discoidal and subinvolute (ww/ dm = 0.48; uw/dm = 0.24) with a very high coiling rate (WER = 2.31) and moderately wide whorl overlap (IZR = 0.23). The whorl profile is weakly depressed (ww/wh = 1.09) with a slightly concave venter that is bordered by a rounded ventrolateral shoulder; the flanks are broadly convex and weakly convergent. The umbilical margin is narrowly rounded and the umbilical wall is steep and weakly incurved. The last whorl shows a modification in the profile. At the beginning it is inverted trapezoidal with fairly convergent flanks and a subangular ventrolateral shoulder (Fig. 12B). The specimen does not show any traces of sculpture. The length of the phragmocone chambers shows considerable changes during the last volution. The first quarter of this whorl consists of six chambers (CLI = 15); considerable septal crowding at the end of the phragmocone causes the number to increase to about 12 (CLI = 7.5). Especially the last six septa are very closely spaced. The suture line shows a shallow and broadly rounded external lobe, a narrowly rounded ventrolateral saddle, a shallow lateral lobe twice as deep than the external lobe and a very small umbilical lobe (Fig. 12C). Paratype MB.C.32117 is an incomplete, fully chambered specimen with a conch diameter of 63 mm (Fig. 13B). It corresponds largely to the holotype in its conch proportions and also shows a weakly concave umbilical wall, almost parallel flanks, a rounded but pronounced ventrolateral shoulder and a weakly concave venter (Fig. 13A). The suture line has a shallow external lobe, a narrowly rounded ventrolateral saddle and a broadly rounded lateral lobe that is twice as deep as the external lobe (Fig. 13C). Remarks Specimens of Aifinautilus icanus gen. et sp. nov. can hardly be confused with any other species of Baghuk Mountain. Species of the genus Ocunautilus gen. nov. show similarities in conch shape, but there are some easily recognisable differences. In A. icanus, the flanks are almost parallel, while in the species of Ocunautilus they are distinctly convergent. Another distinguishing criterion is the coiling rate, which is considerably lower in A. icanus (WER ~ 2.25) than in Ocunautilus (WER mostly over 3.00). Fig. 13. Aifinautilus icanus gen. et sp. nov., paratype MB.C.32117 (Korn et al. 2011 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Lateral and ventral views. C. Suture line at ww = 26.5 mm, wh = 25.5 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 24 There are great similarities of A. icanus gen. et sp. nov. to species of the Triassic genus Germanonautilus. For example, A. icanus shows very close agreement in conch morphology with G. bidorsatus (Schlotheim, 1820), as was shown by Dzik (1984: 166, text-fig. 64). However, Germanonautilus differs from Aifinautilus gen. nov. by the presence of an annular lobe. Genus Azarinautilus Korn & Ghaderi, 2025 Type species Azarinautilus nahidae Korn & Ghaderi, 2025; original designation. Diagnosis Genus of the family Ocunautilidae fam. nov. with a rather small, subinvolute or subevolute conch; whorl profile lyriform, venter moderately to deeply concave and bordered by raised keels, umbilical margin broadly rounded or subangular. Sculpture with conical nodes or shallow ribs in the midflank area. Suture line with narrow, rounded external lobe and broadly rounded lateral lobe (from Korn & Ghaderi 2025). Included species NW Iran (Korn & Ghaderi 2025): Azarinautilus nahidae Korn & Ghaderi 2025, Wuchiapingian. Central Iran (this paper): Azarinautilus phorminx sp. nov., Changhsingian. Remarks Azarinautilus has an isolated position within the family Domatoceratidae because of its conch shape and sculpture. A comparably distinctly concave venter has apparently not been described from any other genus of the family; however, species of Fididomatoceras show a flat or slightly concave venter bordered laterally by low ridges. Azarinautilus phorminx sp. nov. urn:lsid:zoobank.org:act:91FE758E-E2BC-45B0-BE73-90A885833281 Fig. 14; Table 8 Diagnosis Species of Azarinautilus with thickly discoidal, subevolute conch (ww/dm ~ 0.40; uw/dm ~ 0.32), equidimensional whorl profile (ww/wh ~ 1.00) and very high coiling rate (WER ~ 2.30) at a conch diameter of 45 mm. Whorl profile rounded lyriform with strongly convergent, broadly convex flanks; venter moderately concave, umbilical margin subangular. Whorl overlap small (IZR ~ 0.15). Sculpture with short ribs in the midflank area. Suture line with a very shallow external lobe and a very shallow lateral lobe. Etymology From the Greek ‘φόρμιγξ’ = the ancient Greek lyre; because of the whorl profile. Table 7. Conch dimensions (in mm) and ratios of Aifinautilus icanus sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32116 114.0 55.2 50.5 27.0 39.0 0.48 1.09 0.24 2.31 0.23 MB.C.32116 75.0 40.3 38.3 18.6 – 0.54 1.05 0.25 – – MB.C.32119 79.2 38.0 34.5 22.1 – 0.48 1.10 0.28 – – MB.C.32117 63.0 31.0 27.4 16.6 20.6 0.49 1.13 0.26 2.21 0.25 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 25 Paratype IRAN – Esfahan Province • 1 specimen; same data as for holotype; 2011; Korn et al. leg.; illustrated in Fig. 16D–F; MB.C.32123. Description Holotype MB.C.30223 is an incomplete internal mould with a conch diameter of 57 mm; it is fully chambered (Fig. 16B). The conch width had to be reconstructed; it appears that the conch is thickly discoidal and subevolute (ww/dm ~ 0.48; uw/dm = 0.47) with a moderately high coiling rate (WER = 1.81). The whorl profile is moderately depressed (ww/wh ~ 1.80) and rounded trapezoidal with a flatly rounded venter and a broadly rounded ventrolateral shoulder. The divergent flanks are slightly flattened; an Fig. 16. Foordiceras eicosacanthum sp. nov. from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Holotype MB.C.30223 (Korn et al. 2013 Coll.), reconstruction of apertural view. B. The same specimen, lateral and ventral views. C. The same specimen, suture line at wh = 17.2 mm. D. Paratype MB.C.32123 (Korn et al. 2011 Coll.), reconstruction of apertural view. E. The same specimen, lateral view. F. The same specimen, suture line at dm = 50.0 mm, ww = 22.0 mm, wh = 15.0 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 32 umbilical margin is not present (Fig. 16A). The sculpture consists of low conical ventrolateral nodes, of which there are 10 on half a volution. They are entirely confined to the ventrolateral shoulder and the outer flank and are as wide as their interspaces. The suture line shows a very wide, very shallow external lobe and a very shallow lateral lobe (Fig. 16C). The septa are rather short in the last quarter volution of the phragmocone has about eight chambers (CLI = 11); in the penultimate volution, there are only six chambers on a quarter whorl (CLI = 15). Paratype MB.C.32123 is a partially corroded specimen with a conch diameter of 68 mm (Fig. 16E). One whorl between a conch diameter of 20 and 37 mm is rather well-preserved and allows the study of the conch geometry and sculpture. In both features as well as in the suture line (Fig. 16F) the paratype agrees well with the holotype. The number of chambers remains the same in the last volution; in both last half volutions the phragmocone has 15 chambers each (CLI = 12). The third last half volution has 12 chambers (CLI = 15). Remarks Foordiceras eicosacanthum sp. nov. differs from F. decacanthum sp. nov. and F. ascetum sp. nov. in the rather small and more numerous ventrolateral nodes, of which there are ten on half a volution, while there are only five very coarse nodes on half a volution in the other two species. Furthermore, F. eicosacanthum has a more strongly depressed whorl profile (ww/wh ~ 1.75) than F. decacanthum (ww/ wh ~ 1.25) and F. ascetum (ww/wh ~ 1.00). Foordiceras decacanthum sp. nov. urn:lsid:zoobank.org:act:FEB57A12-32B4-461B-968A-0037BCC865E6 Fig. 17; Table 11 Metacoceras sp. – Korn et al. 2021: text-fig. 17b. Diagnosis Species of Foordiceras with thinly discoidal, subevolute conch (ww/dm ~ 0.40; uw/dm ~ 0.44), weakly depressed whorl profile (ww/wh ~ 1.25) and high coiling rate (WER ~ 2.10) at a conch diameter of 60 mm. Whorl profile trapezoidal with divergent, convex flanks; venter flattened, umbilical margin incipient. Sculpture with about 10 very coarse, blunt ventrolateral ribs per volution. Suture line with a very shallow external lobe and a very shallow, broadly rounded lateral lobe. Etymology From the Greek ‘δέκα’ = ‘ten’ and ‘ἄκανθα’ = ‘thorn, spine’; because of the ten ventrolateral nodes per volution. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2010; Korn et al. leg.; illustrated in Fig. 17; MB.C.30224. Table 10. Conch dimensions (in mm) and ratios of Foordiceras eicosacanthum sp. nov. from Baghuk Mountain; reconstructed value in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32123 61.3 28.0 16.2 29.0 15.6 0.46 1.73 0.47 1.80 0.04 MB.C.30223 56.5 27.2 15.1 26.8 14.5 0.48 1.80 0.47 1.81 0.04 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 33 Description Holotype MB.C.30224 is an incomplete, but rather well-preserved internal mould with a diameter of 62 mm (Fig. 17B). The conch is thinly discoidal and subevolute (ww/dm = 0.41; uw/dm = 0.44) with a high coiling rate (WER = 2.08); the whorl profile is weakly depressed (ww/wh = 1.27) and rounded trapezoidal with a flatly rounded venter and a broadly rounded ventrolateral shoulder. The divergent flanks are convex; a rudimentary umbilical margin is developed (Fig. 17A). The sculpture consists of about 10 very large, but low ventrolateral nodes per volution; these nodes have a rounded conical shape and continue as very low ribs on the flank. They are much wider than the spaces between them. These ribs are considerably more prominent on the penultimate whorl, at a conch diameter of about 25 mm, than on the last whorl. The suture line shows a very shallow external lobe and a very shallow lateral lobe (Fig. 17C). The last half volution of the phragmocone has about 12 chambers (CLI = 15). Remarks Foordiceras decacanthum sp. nov. differs from F. eicosacanthum sp. nov., which possesses a similar conch geometry, in the number and formation of the ventrolateral nodes. Foordiceras decacanthum has only five very coarse nodes on half a whorl, whereas F. eicosacanthum has ten much smaller nodes. Foordiceras decacanthum has a very similar sculpture to F. ascetum sp. nov., but shows a depressed whorl profile (ww/wh ~ 1.25), whereas in F. ascetum this is almost equidimensional (ww/wh ~ 1.00). Another criterion to separate F. decacanthum from the rather similar F. ascetum is in the width of the nodes; in F. decacanthum they are wider than the interspaces, while they are only half as wide as their interspaces in F. ascetum. Fig. 17. Foordiceras decacanthum sp. nov., holotype MB.C.30224 (Korn et al. 2010 Coll.) from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Dorsal, lateral and ventral views. C. Suture line at wh = 10.8 mm. Scale bar units = 1 mm. Table 11. Conch dimensions (in mm) and ratios of Foordiceras decacanthum sp. nov. from Baghuk Mountain. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.30224 61.9 25.1 19.7 27.5 19.0 0.41 1.27 0.44 2.08 0.04 European Journal of Taxonomy 1019: 1–76 (2025) 34 Foordiceras decacanthum sp. nov. differs from the superficially similar F. goliathus, which also possesses very coarse ventrolateral nodes, in the much wider umbilicus. The uw/dm ratio is about 0.45 in F. decacanthum, but only around 0.30 in F. goliathus. Foordiceras ascetum sp. nov. urn:lsid:zoobank.org:act:B448394B-F0E2-42D2-9EFA-FA09D8C8E1A7 Fig. 18; Table 12 Diagnosis Species of Foordiceras with thinly discoidal, subevolute conch (ww/dm ~ 0.33; uw/dm ~ 0.43), nearly equidimensional whorl profile (ww/wh ~ 1.00) and high coiling rate (WER ~ 2.20) at a conch diameter of 60 mm. Whorl profile trapezoidal with weakly divergent, flattened flanks; venter flattened, umbilical margin incipient. Sculpture with about 10 coarse, blunt ventrolateral ribs per volution. Suture line with a very shallow external lobe and a very shallow, broadly rounded lateral lobe. Etymology From the Greek ‘ἀσκητός’ = ‘decorated’; because of the sculpture. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 18; MB.C.32124. Fig. 18. Foordiceras ascetum sp. nov., holotype MB.C.32124 (Korn et al. 2011 Coll.) from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Lateral view. C. Suture line at dm = 61.4 mm, wh = 19.6 mm. Scale bar units = 1 mm. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 35 Description Holotype MB.C.32124 is an internal mould with a diameter of 86 mm, but the last portion is poorly preserved (Fig. 18B). The conch is, at 62 mm diameter, thinly discoidal and subevolute (ww/dm = 0.33; uw/dm = 0.43) with a high coiling rate (WER = 2.21). The whorl profile is weakly compressed (ww/ wh = 0.98) and rounded trapezoidal with a nearly flat venter and a broadly rounded ventrolateral shoulder. The weakly divergent flanks are flattened; an umbilical margin is only barely visible (Fig. 18A). The sculpture has five prominent conical nodes per half volution in the outer area of the flank; these nodes show a low extension on the flank towards the umbilicus. The nodes are narrower than their interspaces. The suture line shows shallow, broadly rounded lobes on venter and flanks (Fig. 18C). The last half volution of the phragmocone has about 16 chambers (CLI = 11). Remarks Foordiceras ascetum sp. nov. differs from F. eicosacanthum sp. nov. and F. decacanthum sp. nov. in the nearly equidimensional whorl profile (ww/wh = 1.00), which is depressed in the other two species (ww/ wh = 1.75 in F. eicosacanthum and = 1.25 in F. decacanthum). Another criterion to separate F. ascetum from the rather similar F. decacanthum is in the width of the nodes; in F. ascetum they are only half as wide as their interspaces, while they are wider than the interspaces in F. decacanthum. Genus Tardunautilus Korn & Ghaderi, 2025 Diagnosis Genus of the family Foordiceratidae with evolute conch; whorl profile rounded triangular or rounded trapezoidal, depressed with broadly rounded venter. Sculpture with one or two rows of conical ribs near the ventrolateral shoulder. Suture line with very shallow external lobe and broadly rounded lateral lobe; without annular process (from Korn & Ghaderi 2025). Type species Tardunautilus nimius Korn & Ghaderi, 2025; by original designation. Included species NW Iran (Korn & Ghaderi 2025): Tardunautilus nimius Korn & Ghaderi, 2025, Wuchiapingian; Tardunautilus minor Korn & Ghaderi, 2025, Wuchiapingian. Central Iran (this paper): Tardunautilus aperimos sp. nov., Wuchiapingian. Remarks The new genus can be easily distinguished from all other genera in the assemblage from Baghuk Mountain because of its combination of a conch shape with a wide umbilicus, a rounded triangular or rounded trapezoidal whorl profile and a sculpture consisting of conical nodes. A genus with a similar morphology is Pseudotemnocheilus, but this is mostly known from much smaller specimens of about 40–60 mm in diameter. These smaller specimens have a much narrower umbilicus (uw/dm ~ 0.40) compared to Tardunautilus (uw/dm ~ 0.47) and a less depressed whorl profile (ww/wh ~ 1.30) than Tardunautilus (ww/wh ~ 1.40–1.80). The coiling rate is much lower in Tardunautilus (WER below 2.00) when compared to Pseudotemnocheilus (WER greater than 2.25). Table 12. Conch dimensions (in mm) and ratios of Foordiceras ascetum sp. nov. from Baghuk Mountain. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32124 61.6 20.5 21 26.5 20.2 0.33 0.98 0.43 2.21 0.04 European Journal of Taxonomy 1019: 1–76 (2025) 36 Tardunautilus aperimos sp. nov. urn:lsid:zoobank.org:act:E08EF718-C2F6-44E2-9D15-A879DA51D394 Fig. 19; Table 13 Diagnosis Species of Tardunautilus with thinly discoidal, evolute conch (ww/dm ~ 0.35; uw/dm ~ 0.50), weakly depressed whorl profile (ww/wh ~ 1.50) and low coiling rate (WER ~ 1.70) at a conch diameter of 60 mm. Whorl profile rounded trapezoidal with flattened venter, rounded ventrolateral shoulder, strongly divergent flanks and very small imprint zone. Sculpture with 20 conical nodes on the outer flank per volution. Suture line with a very shallow external lobe and a very shallow lateral lobe. Etymology From the Greek ‘ἀπό’ = ‘from’ and ‘ἐρῆμος’ = ‘desert’; because of the origin of the material. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Prototoceras beds (early Wuchiapingian); 2012; Korn et al. leg.; illustrated in Fig. 19; MB.C.32125. Description Holotype MB.C.32125 is an internal mould with a conch diameter of 58 mm; it is nearly fully chambered (Fig. 19B). The conch is thinly discoidal and evolute (ww/dm = 0.37; uw/dm = 0.53) with a low coiling rate (WER = 1.70); the whorl profile is weakly depressed (ww/wh = 1.49) and rounded trapezoidal with a flattened venter, a rounded ventrolateral shoulder and strongly convex and divergent flanks (Fig. 19A). The specimen shows a whorl that only slightly embraces the preceding; the umbilical seam has a position on the venter of the preceding whorl. The sculpture consists of 20 blunt conical nodes in ventrolateral position. These nodes are slightly narrower than their interspaces. The suture line shows very shallow, broadly rounded lobes on the venter and the flank (Fig. 19C). Fig. 19. Tardunautilus aperimos sp. nov., holotype MB.C.32125 (Korn et al. 2012 Coll.) from the Prototoceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Dorsal and lateral views. C. Suture line at dm = 43.8 mm, ww = 23.8 mm, wh = 18.0 mm. Scale bar units = 1 mm. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 37 Remarks Tardunautilus aperimos sp. nov. differs from the similar species T. minor of Julfa in the lower number of ventrolateral nodes (20 per whorl, but about 25 in T. minor) and the wider umbilicus (uw/dm ~ 0.53 in T. aperimos, but only ~ 0.47 in T. minor) at comparable conch diameters. Tardunautilus nimius from Julfa differs in the broader whorls and the double row of ventrolateral nodes. Family Pleuronautilidae Hyatt, 1900 Diagnosis Family of the superfamily Pleuronautiloidea with a commonly subquadrate or weakly depressed whorl profile; venter ranging from convex to weakly concave, ventrolateral shoulder and umbilical margin often pronounced, flanks usually weakly convergent. Sculpture with numerous ribs on the flank, sometimes with conical tubercles and more rarely with spiral ridges. An annular process is present in the advanced species (from Korn 2025). Included genera Lutonautilus gen. nov. (Permian); Pleuronautilus Mojsisovics, 1882 (Triassic); Phloioceras Hyatt, 1884 (Triassic); Anoploceras Hyatt, 1900 (Triassic); Encoiloceras Hyatt, 1900 (Triassic); Enoploceras Hyatt, 1900 (Triassic); Holconautilus Mojsisovics, 1902 (Triassic); Trachynautilus Mojsisovics, 1902 (Triassic); Sibyllonautilus Diener, 1915 (Triassic); Phaedrysmocheilus Shimansky & Erlanger, 1955 (Triassic); Arctonautilus Sobolev, 1989 (Triassic); Grumantoceras Sobolev, 1989 (Triassic). Remarks A detailed discussion of the Pleuronautilidae and families with similar morphology has been given by Korn (2025). Genus Lutonautilus gen. nov. urn:lsid:zoobank.org:act:6CCC6ECD-ED65-4A11-83AC-666B45EFC1C0 New genus C – Korn 2025: 57. — Korn & Ghaderi 2025: 7, 61, 63, fig. 33. Type species Lutonautilus cratus gen. et sp. nov. Diagnosis Genus of the family Pleuronautilidae with subevolute conch; whorl profile inverted trapezoidal, weakly depressed or equidimensional with broadly rounded venter, parallel or weakly convergent flanks, rounded umbilical margin and convex or flattened umbilical wall. Sculpture with ribs on the flanks, without nodes or tubercles. Suture line with very shallow external lobe and broadly rounded lateral lobe; without annular process. Etymology Named after the Lut desert (Central Iran), at which margin Baghuk Mountain is located. Table 13. Conch dimensions (in mm) and ratios of Tardunautilus aperimos sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32125 57.9 21.5 14.4 30.5 13.5 0.37 1.49 0.53 1.70 0.06 MB.C.32125 44.5 17.1 11.4 21.8 – 0.38 1.50 0.49 – – European Journal of Taxonomy 1019: 1–76 (2025) 38 Included species Central Iran (this paper): Lutonautilus cratus gen. et sp. nov., Wuchiapingian; Lutonautilus elachus gen. et sp. nov., Wuchiapingian; Lutonautilus cymus gen. et sp. nov., Wuchiapingian. Remarks Lutonautilus gen. nov. is newly introduced here for Permian species with a conch shape and sculpture similar to some Triassic species of Pleuronautilus, such as P. mosis Mojsisovics, 1882. The main difference, however, is that Lutonautilus does not possess the annular lobe that is present in Pleuronautilus. Lutonautilus gen. nov. occurs with morphologically similar species in the sections of central Iran and probably also in the Transcaucasian region. But it is also possible that the genus occurs in other regions such as the Salt Range of Pakistan; however, this can only be clarified by revising the corresponding assemblages. Lutonautilus cratus gen. et sp. nov. urn:lsid:zoobank.org:act:FA260A86-6965-469D-96FE-D7D6B45B5F8A Fig. 20; Table 14 New genus, new species – Korn 2025: 58, fig. 29. Diagnosis Species of Lutonautilus gen. nov. with thinly discoidal, subinvolute conch (ww/dm = 0.35–0.40; uw/ dm = 0.35–0.40), nearly equidimensional whorl profile (ww/wh = 0.95–1.05) and high to very high coiling rate (WER = 2.20–2.35) at a conch diameter of 60–80 mm. Whorl profile with gently convergent flanks; venter broadly rounded, flanks slightly flattened, umbilical margin rounded, umbilical wall flattened. Sculpture with about 25 blunt lateral ribs per volution; they begin on the outer umbilical wall and are strengthened on the ventrolateral shoulder to form elongate nodes. Suture line with a shallow external lobe and a shallow, broadly rounded lateral lobe. Etymology From the Greek ‘κρατύς’ = ‘strong’; because of the rather robust conch and sculpture. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 20A–D; MB.C.32126. Paratypes IRAN – Esfahan Province • 1 specimen; same data as for holotype; 2010; Korn et al. leg.; illustrated in Fig. 20E–F; MB.C.32127 • 2 specimens; same data as for holotype; 2010; Korn et al. leg.; MB.C.32128, MB.C.32129. Description Holotype MB.C.32126 is a rather complete, but somewhat corroded specimen with a conch diameter of 88 mm (Fig. 20A, D). It is almost completely chambered and only a little more than a quarter of the last whorl belongs to the body chamber. The conch is thinly discoidal and subevolute (ww/dm = 0.33; uw/dm = 0.38) with a high coiling rate (WER = 2.17). The whorl profile is almost square-shaped (ww/ wh = 0.95) and shows a flatly rounded venter and a broadly rounded ventrolateral shoulder. The flanks are slightly flattened and slowly convergent; the umbilical margin is continuously rounded and the KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 39 Fig. 20. Lutonautilus cratus gen. et sp. nov. from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Holotype MB.C.32126 (Korn et al. 2011 Coll.), left side lateral and dorsal views. B. The same specimen, reconstruction of apertural view. C. The same specimen, suture line at dm = 76.2 mm, ww = 27.0 mm, wh = 29.2 mm. D. The same specimen, right side lateral view. E. Paratype MB.C.32127 (Korn et al. 2010 Coll.), reconstruction of apertural view. F. The same specimen, lateral view. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 40 umbilical wall is steep (Fig. 20B). The sculpture consists of about 25 blunt ribs on the flank; the ribs and their interspaces have almost the same width. These ribs already begin in the outer area of the umbilical wall and from there, they follow a weakly backwardly directed course; they extend across the flank with a broad and shallow sinus and are strengthened to form radially elongated nodes in the area of the ventrolateral shoulder. There they suddenly weaken and diminish; no ribs are visible on the venter. The suture line shows a very shallow external lobe and a broadly rounded lateral lobe (Fig. 20C). The last half whorl of the phragmocone has about 12 chambers (CLI = 15). Paratype MB.C.32127 is a fragment of a specimen with a conch diameter of 76 mm (Fig. 20F). The conch geometry is largely the same as in the holotype, but the paratype has a slightly more compressed whorl profile (ww/wh = 0.93) and a higher coiling rate (WER = 2.35). The sculpture is better preserved than in the holotype; it shows 16 rather sharp ribs on the last half volution; these ribs start on the umbilical wall and thin out at the ventrolateral shoulder. The ribs are somewhat narrower than their interspaces; they extend across the flank with a shallow sinus. Remarks Lutonautilus cratus gen. et sp. nov. differs from the co-occurring L. elachus gen. et sp. nov. in the slenderer whorl profile (ww/wh = 0.95–1.05 in L. cratus but ~ 1.15 in L. elachus), the stronger convergent flanks (nearly parallel in L. elachus) and the wider umbilicus (uw/dm = 0.35–0.40 in L. cratus, but only ~ 0.30 in L. elachus). Furthermore, the ribs begin in the outer area of the umbilical wall in L. cratus, but at the umbilical margin in L. elachus. Lutonautilus cratus gen. et sp. nov. differs from L. cymus gen. et sp. nov. in the shape of the ribs, which in L. cratus are almost straight on the flanks, while they extend with a concave arch in L. cymus. The ribs of L. cratus are coarse in the midflank area, while they are weakly developed in the middle of the flank in L. cymus and strengthened and forming nodes on the outer and inner flanks. Lutonautilus elachus gen. et sp. nov. urn:lsid:zoobank.org:act:7AC16980-96B5-465E-A223-3295CE49F01E Fig. 21; Table 15 Pleuronautilus sp. – Korn et al. 2021: text-fig. 17c. Diagnosis Species of Lutonautilus gen. nov. with thickly discoidal, subevolute conch (ww/dm ~ 0.45; uw/dm ~ 0.32), weakly depressed whorl profile (ww/wh ~ 1.15) and very high coiling rate (WER ~ 2.50) at a conch diameter of 50 mm. Whorl profile with nearly parallel flanks; venter flattened, flanks slightly flattened, umbilical margin narrowly rounded, umbilical wall flat. Sculpture with about 20 blunt lateral ribs per volution. Suture line with a shallow external lobe and a shallow, broadly rounded lateral lobe. Table 14. Conch dimensions (in mm) and ratios of Lutonautilus cratus gen. et sp. nov. from Baghuk Mountain; estimated values in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32126 87.6 29.0 30.5 33.2 28.1 0.33 0.95 0.38 2.17 0.08 MB.C.32128 80.5 30.4 30.0 30.0 28.0 0.38 1.01 0.37 2.35 0.07 MB.C.32127 76.1 26.7 28.6 28.1 26.5 0.35 0.93 0.37 2.35 0.07 MB.C.32129 61.6 24.3 22.4 24.4 21.2 0.39 1.08 0.40 2.32 0.05 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 41 - Formation of lateral ribs: lateral ribs do not occur in many of the North American species, but are present in species from other regions (T. debile, T. admonens). - Formation of the umbilical nodes: umbilical sculptural elements are present in some species; they range from being small tubercles (T. clydense) to large conical nodes (T. schellbachi). The list of mostly bipolar character pairs shows numerous theoretical possible combinations; however, covariation is very common and some of the characters often appear simultaneously. Tainoceras hystatum sp. nov. urn:lsid:zoobank.org:act:BE14C8AB-8E7D-4D26-B1BA-64AFA2B52E70 Fig. 23; Table 17 Diagnosis Species of Tainoceras with thinly discoidal, evolute conch (ww/dm ~ 0.44; uw/dm ~ 0.32), weakly depressed whorl profile (ww/wh ~ 1.05) and extremely high coiling rate (WER ~ 2.55) at a conch diameter of 40 mm. Whorl profile octagonal with shallow longitudinal ventral groove. Sculpture with two rows of tubercles on the ventrolateral shoulder and one row on the umbilical margin. Suture line undulating with very shallow lobes and low saddles. Etymology From the Greek ‘ὕστατος’ = ‘latest’; because the species is the stratigraphically latest of the nautiloids from Baghuk Mountain. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain section H; Hambast Formation, Paratirolites beds (late Changhsingian), 0.40 m below top; 2013; Korn et al. leg.; illustrated in Fig. 23; MB.C.32134. Paratype IRAN – Esfahan Province • 1 specimen; same data as for holotype; 2011; Korn et al. leg.; MB.C.32135. Description Holotype MB.C.32134 is a somewhat corroded specimen with a conch diameter of 40 mm (Fig. 23A). It is fairly well preserved only on its left side as an internal mould. The specimen is completely chambered. Fig. 23. Tainoceras hystatum sp. nov., holotype MB.C.32134 (Korn et al. 2013 Coll.) from the Paratirolites beds of the Hambast Formation at Baghuk Mountain. A. Lateral and dorsal views. B. Reconstruction of apertural view. C. Suture line at dm = 32.1 mm, ww = 18.2 mm, wh = 12.3 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 48 The conch is thinly discoidal and subevolute (ww/dm = 0.43; uw/dm = 0.33) with an extremely high coiling rate (WER = 2.55). The whorl profile is generally octagonal and slightly depressed (ww/wh = 1.09). It has a flattened venter with a shallow longitudinal depression; the ventrolateral shoulder is subangular and the flanks are almost flat and parallel. The umbilical margin is prominent and the umbilical wall is oblique and flat. The areas between the angular margins of the whorl profile are flattened (Fig. 23B). The sculpture consists of three rows of tubercles, one on the umbilical margin, one on the ventrolateral shoulder and one delimiting the midventral longitudinal groove. The first and the last ones are only very weakly developed; the middle one is much stronger and consists of blunt conical nodes. They are connected to the tubercles on the umbilical wall by very low ribs. The suture line is strongly dependent on the whorl profile; it has shallow lobes at the flattened areas and low saddles at the pronounced margins (Fig. 23C). Remarks Tainoceras hystatum sp. nov. shows a morphology of conch and sculpture that can be described as conservative. Even some of the Late Carboniferous species, such as the type species T. quadrangulum, show an octagonal shape of the whorl profile with two rows of tubercles each adjacent to the median longitudinal groove. However, T. quadrangulum has coarser ventrolateral nodes and a narrower umbilicus (uw/dm < 0.30) than T. hystatum (uw/dm > 0.30). Tainoceras hystatum sp. nov. differs by its wider umbilicus and particularly by the parallel flanks, which are either convergent or divergent in many other species of the genus Tainoceras. Another distinguishing feature is the shape of the tubercles, which are much smaller in T. hystatum than in most other species. Genus Epitainoceras gen. nov. urn:lsid:zoobank.org:act:4F3AA6AC-9211-4B03-A581-9676BE734DAA New genus D – Korn 2025: 61. — Korn & Ghaderi 2025: 64, 72, 74. Type species Epitainoceras lutense gen. et sp. nov. Diagnosis Genus of the family Tainoceratidae with subinvolute or subevolute conch; whorl profile depressed and polygonal with a shallow or broad midventral longitudinal groove. Umbilical margin pronounced and narrowly rounded, flanks convergent. Sculpture with one row of nodes on the ventrolateral shoulder. Suture line strongly depending on the shape of the whorl profile, with rounded V-shaped external lobe and broadly rounded lateral lobe. Etymology From the Greek ‘ἐπί’ = ‘on, above’; referring to the late occurrence of this tainoceratid genus. Included species Transcaucasia (Abich 1878): Nautilus dorso plicatus Abich, 1878, Wuchiapingian, Azerbaijan. Central Iran (this paper): Epitainoceras lutense gen. et sp. nov., Wuchiapingian. Table 17. Conch dimensions (in mm) and ratios of Tainoceras hystatum sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32134 41.2 17.7 16.2 13.6 15.4 0.43 1.09 0.33 2.55 0.05 MB.C.32135 29.5 11.5 11.0 9.2 – 0.39 1.05 0.31 – – KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 49 Remarks Epitainoceras gen. nov. is a genus with a morphology similar to some species of Tainoceras, but with a much weaker sculpture. In contrast to Tainoceras, which has at least two rows of nodes or tubercles in the ventrolateral region and sometimes another row of nodes on the inner flank, Epitainoceras has only one row of nodes, located immediately adjacent to the median longitudinal groove on each side. With a simplification of the sculpture, the new genus may be derived from Tainoceras. Corotainoceras also shows simplification of the sculpture, but differs from Epitainoceras in the absence of ventrolateral nodes and the presence of very coarse dorsolateral nodes. Epitainoceras lutense gen. et sp. nov. urn:lsid:zoobank.org:act:5A1405B2-C14D-4533-8089-A1C3435EBC18 Fig. 24; Table 18 Diagnosis Species of Epitainoceras gen. nov. with thickly discoidal, subinvolute conch (ww/dm ~ 0.55; uw/dm ~ 0.25) and weakly depressed whorl profile (ww/wh ~ 1.35) and very high coiling rate (WER ~ 2.35) at a conch diameter of 70 mm. Whorl profile polygonal with convergent flanks; venter tectiform with broad longitudinal midventral groove, flanks flattened, umbilical margin narrowly rounded. Sculpture with about 15 coarse ventrolateral, transversely elongated nodes per volution. Suture line with a small, rounded V-shaped external lobe, a broadly rounded, very shallow lateral lobe and a very shallow umbilical lobe. Etymology Named after the Lut desert (Central Iran), at which margin Baghuk Mountain is located. Fig. 24. Epitainoceras lutense gen. et sp. nov., holotype MB.C.32136 (Korn et al. 2011 Coll.) from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Lateral and ventral views. C. Suture line at dm = 63.6 mm, wh = 28.2 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 50 Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Araxoceras beds (early Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 24; MB.C.32136. Paratype IRAN – Esfahan Province • 1 specimen; same data as for holotype; MB.C.32137. Description Holotype MB.C.32136 is a corroded phragmocone specimen with a diameter of 75 mm (Fig. 24B). It allows the conch form, sculpture and suture line to be studied, but some conch dimensions can only be estimated. The conch is thickly discoidal and subinvolute (ww/dm ~ 0.55; uw/dm ~ 0.25) with a very high coiling rate (WER ~ 2.35). The whorl profile is slightly depressed (ww/wh ~ 1.35) and widest at the narrowly rounded umbilical margin. The venter possesses a moderately wide median groove; the ventrolateral shoulder is flattened and oblique, the flanks are weakly flattened and convergent and the umbilical margin is narrowly rounded (Fig. 24A). Because of partial corrosion of the specimen, the sculpture cannot be examined in detail. It consists of two rows of nodes arranged on each side of the ventrolateral shoulder. The ventral row has nodes that are elongated in a lateral direction to form short ribs; the dorsal row consists of much weaker, circular nodes. The suture line of the holotype has a shallow, broadly V-shaped external lobe, a low and broadly rounded, slightly asymmetric ventrolateral saddle, a shallow and very wide lateral lobe and a very shallow and small lobe on the umbilical wall (Fig. 24C). The last half volution has 15 phragmocone chambers (CLI = 12). Remarks Epitainoceras lutense gen. et sp. nov. is similar to the Transcaucasian species E. dorsoplicatum comb. nov., but differs in having a much wider midventral groove and significantly larger ventral nodes. These nodes are laterally elongated in E. lutense, whereas they are simply conical in E. dorsoplicatum. Suborder Liroceratina Flower, 1955 Diagnosis Suborder of the order Nautilida, in which an umbilical margin is formed early in ontogeny; advanced species may regress this character. Conch usually pachyconic and rarely discoidal or globular, subinvolute to involute. Juvenile whorl profile circular. Adult whorl profile usually circular or depressed oval without distinct ventrolateral shoulder in the phylogenetically early species, showing modifications during evolution (inverted trapezoidal with convergent flanks and flattened venter). Dorsal whorl zone always present, small to moderately deep. Juvenile sculpture with spiral lines that may be restricted to the umbilical area in the phylogenetically early species; adult sculpture usually lacking except for spiral lines in some species. Septa simply domed in the early species; with dorsal inflexion in advanced species Table 18. Conch dimensions (in mm) and ratios of Epitainoceras lutense gen. et sp. nov. from Baghuk Mountain; reconstructed dimensions and ratios in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32136 74.6 41.6 30.2 17.8 26.0 0.56 1.38 0.24 2.36 0.14 MB.C.32137 73.0 38.5 29.0 20.5 25.5 0.53 1.33 0.28 2.36 0.12 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 51 and with corrugated septa in two derived clades. Suture line depending on the whorl profile, usually with shallow lobes and low saddles; with distinct lobes in two clades (from Korn 2025). Included superfamilies Liroceratoidea Hyatt, 1900 (Carboniferous to Triassic); Ephippioceratoidea Miller & Youngquist, 1949 (Carboniferous to Permian); Clydonautiloidea Hyatt, 1900 (Triassic to Jurassic). Remarks A discussion of the suborder Liroceratina has been given by Korn (2025). Superfamily Liroceratoidea Hyatt, 1900 Diagnosis Superfamily of the suborder Liroceratina with a pachyconic and rarely discoidal or globular, subinvolute to involute conch. Whorl profile usually circular or depressed oval without distinct ventrolateral shoulder; in some species with a pronounced but rounded ventrolateral shoulder. Dorsal whorl zone usually small to moderately deep. Juvenile sculpture in the early species with spiral lines that may be restricted to the umbilical area; derived species are often smooth. Suture line very simple, almost straight across flanks and venter (from Korn 2025). Included families Liroceratidae Miller & Youngquist, 1949 (Carboniferous to Triassic); Coloceratidae Hyatt, 1893 [homonym, synonym of Liroceratidae Miller & Youngquist, 1949]; Paranautilidae Kummel in Flower & Kummel, 1950 (Triassic); Permonautilidae Barskov & Shilovsky, 2014 (Permian); Planetoceratidae Korn, 2025 (Carboniferous); Julfanautilidae Korn & Ghaderi, 2025 (Permian). Remarks A discussion of the superfamily Liroceratoidea has been given by Korn (2025). Family Liroceratidae Miller & Youngquist, 1949 Diagnosis Family of the superfamily Liroceratoidea with a usually pachyconic or globular, subinvolute to subevolute conch. Whorl profile in the adult stage usually more or less strongly depressed; flanks and venter form a continuous arch in the early species, the venter can be flattened or concave in advanced species. Umbilical margin rounded; umbilical wall usually convex. Ornament usually consisting of fine growth lines; spiral lines occur in some genera. Septum simple in shape, concavely domed; suture line very simple, almost straight across flanks and venter or with small lobes and saddles (from Korn 2025). Included genera Solenoceras Hyatt, 1884 (homonym of Solenoceras Conrad, 1860, objective synonym of Coelogasteroceras); Coelogasteroceras Hyatt, 1893 (Carboniferous to Permian); Coloceras Hyatt, 1893 [homonym of Coloceras Taschenberg, 1882, synonym of Liroceras Teichert, 1940]; Stearoceras Hyatt, 1893 (Carboniferous to Permian); Peripetoceras Hyatt, 1894 (Carboniferous to Permian); Potoceras Hyatt, 1894 (Carboniferous); Nannoceras Hyatt, 1894 (nomen nullum, synonym of Peripetoceras); Conradiceras Cossmann, 1900 (objective synonym of Coelogasteroceras); Liroceras Teichert, 1940 (Carboniferous to Permian); Condraoceras Miller, Lane & Unklesbay, 1947 (Carboniferous European Journal of Taxonomy 1019: 1–76 (2025) 52 to Permian); Periptoceras Chao, 1954 (nomen nullum, synonym of Peripetoceras); Hemiliroceras Ruzhencev & Shimansky, 1954 (Carboniferous to Permian); Bistrialites Turner, 1954 (Carboniferous); Pseudophacoceras Turner, 1966 (Carboniferous); Neobistrialites Tucker, Mapes & Aronoff, 1978 (Carboniferous); Jianoceras Ma, 1997 (Permian); Nemdoceras Barskov & Shilovsky, 2014 (Permian); Paraliroceras Barskov & Shilovsky, 2014 (Permian); Tatianautilus Barskov & Shilovsky, 2014 (Permian); Leniceras Leonova & Shchedukhin, 2020 (Permian); Shikhanonautilus Leonova & Shchedukhin, 2020 (Permian); Thyoceras Leonova & Shchedukhin, 2020 (Permian); Celeroliroceras Korn & Ghaderi, 2025 (Permian); Perunautilus Crick & Sobolev, 1994 (Triassic); Tomponautilus Sobolev, 1989 (Triassic). Remarks A discussion of the family Liroceratidae has been given by Korn (2025). Genus Liroceras Teichert, 1940 Type species Coloceras liratum Girty, 1911; original designation. Diagnosis Genus of the family Liroceratidae with pachyconic to globular, involute or subinvolute conch; umbilicus closed by a plug in some species. The first whorl is 10–20 mm in diameter with a very small umbilical foramen; the conch is rapidly increasing in height with a high coiling rate (WER usually higher than 2.50). Whorls weakly embracing, their profile ranges from reniform to nearly circular. Juvenile conch with longitudinal ridges or lines; adult ornament with growth lines with a fairly deep ventral sinus and spiral lines in some species. Septa without inflexions, slightly concave. Suture line simple, nearly straight with a shallow, broadly rounded internal lobe. The siphuncle has a position between the centre of the septum and the venter (after Gordon 1965; Shimansky 1967). Included Carboniferous species North America (Shumard & Swallow 1858; Miller & Gurley 1897; Girty 1911; Miller et al. 1933; Newell 1936; Unklesbay 1962; Gordon 1965): Nautilus Missouriensis Swallow, 1858, Bashkirian, Missouri; Solenochilus henryvillense Miller & Gurley, 1897, Viséan, Indiana; Coloceras liratum Girty, 1911, Moscovian, Oklahoma; Coloceras liratum var. obsoletum Girty, 1911, Moscovian, Oklahoma; Coloceras greenei Miller, Dunbar & Condra, 1933, Kasimovian, Oklahoma; Coloceras milleri Newell, 1936, Kasimovian, Kansas; Coloceras reticulatum Miller & Owen, 1937, Kasimovian, Oklahoma; Liroceras patulum Unklesbay, 1962, Bashkirian, Arkansas; Liroceras bicostatum Gordon, 1965, Serpukhovian, Arkansas. British Isles (Foord 1891; Hind 1910; Turner 1954; Ramsbottom & Moore 1961): Coelonautilus Derbiensis Foord, 1891, Viséan, Derbyshire; Coelonautilus Derbiensis var. globulare Foord, 1891, Viséan, Isle of Man; Solenocheilus globosus Hind, 1910, Bashkirian, Lancashire; Liroceras lunense Turner, 1954, Serpukhovian, Yorkshire; Liroceras leitrimense Ramsbottom & Moore, 1961, Viséan, Ireland. Central Europe (Trenkner 1868; Hyatt 1894; Miller et al. 1933; Schmidt 1951): Nautilus grundensis Trenkner, 1868, Viséan, Harz Mountains; Coloceras globatum Hyatt, 1894, Viséan, Belgium; Coloceras hyatti Miller, Dunbar & Condra, 1933, Viséan, Belgium; Liroceras occlusor Schmidt, 1951, Viséan, Harz Mountains; Liroceras schaelkense Schmidt, 1951, Viséan, Rhenish Mountains. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 53 North Africa (Korn & Klug 2023): Liroceras karaouii Korn & Klug, 2023, Viséan, Anti-Atlas; Liroceras vermis Korn & Klug, 2023, Serpukhovian, Anti-Atlas. Western Russia (Eichwald 1857; Shimansky 1967): Nautilus excentricus Eichwald, 1857, Serpukhovian, Western Russia; Liroceras fornicatum Shimansky, 1967, Serpukhovian, Western Russia; Liroceras devjatovense Shimansky, 1967, Moscovian, Moscow Basin. Urals (Shimansky 1967): Liroceras praelunense Shimansky, 1967, Viséan, North Urals; Liroceras ruzhencevi Shimansky, 1967, Serpukhovian, South Urals. North China (Ruan & Zhou 1987): Liroceras reniforme Ruan & Zhou, 1987, Bashkirian, Ningxia. Included Permian species North America (Hyatt 1893): Coloceras globulare Hyatt, 1893, Artinskian, Texas. Central and Southern Europe (Gemmellaro 1889; Prinoth & Posenato 2007): Endolobus salomonensis Gemmellaro, 1889, Wordian, Sicily; Liroceras gardenense Prinoth & Posenato, 2007, Changhsingian, Dolomites. Western Russia, Urals (Yakovlev 1899; Kruglov 1928; Barskov et al. 2014; Leonova & Shchedukhin 2020): Asymptoceras korulkense Yakovlev, 1899, Sakmarian, South Urals; Coloceras (?) sarvaensis Kruglov, 1928, Sakmarian (?), South Urals; Coloceras abichi var. tastubense Kruglov, 1928, Sakmarian (?), South Urals; Liroceras volgense Barskov & Shilovsky, 2014, Roadian, Western Russia; Liroceras shakhtauense Leonova & Shchedukhin, 2020, Asselian or Sakmarian, South Urals. NW Iran (Korn & Ghaderi 2025): Liroceras reticulum Korn & Ghaderi, 2025, Wuchiapingian. Central Iran (this paper): Liroceras leptum sp. nov., Wuchiapingian. Pakistan (Reed 1944): Liroceras bakhense Reed, 1944, Wuchiapingian, Salt Range. South China (Chao 1940, 1954; Xu 1977; Zhao et al. 1978; Liang 1984; Wu & Kuang 1992): Coloceras sinense Chao, 1940, Kungurian, Hunan; Peripetoceras hsueyuechiani Chao, 1954, Kungurian, Hunan; Liroceras orientale Chao, 1954, Kungurian, Hunan; Ephippioceras hunanense Chao, 1954, Kungurian, Hunan; Liroceras didmyoaurise Xu, 1977, Kungurian, Hunan; Liroceras meishanense Zhao, Liang & Zheng, 1978, Changhsingian, Zhejiang; Liroceras chenxianense Liang, 1984, Changhsingian, Hunan; Liroceras lichuanense Wu & Kuang, 1992, Changhsingian, Hubei. Indo-Pacific (Haniel 1915): Nautilus Molengraaffi Haniel, 1915, Wuchiapingian, Timor. Madagascar (Vaillant-Couturier Treat 1933): Nautilus waterloti Vaillant-Couturier Treat, 1933, Wuchiapingian. Remarks The genus Liroceras was introduced by Teichert (1940) for those Carboniferous and Permian nautiloids that were previously mostly included in the genus Coloceras Hyatt, 1893. The name Coloceras had already been used by Taschenberg (1882) as a subgenus for recent Mallophaga. Liroceras has a stratigraphic range from the Viséan to the Changhsingian and is represented by species at almost all stages of this long interval. At the same time, Liroceras is geographically widespread, both in the Carboniferous and in the Permian. Liroceras is also known from different facies areas; Early European Journal of Taxonomy 1019: 1–76 (2025) 54 Carboniferous species are known from shallower and deeper areas of the shelf. In the Late Permian, the genus was more common in the shallower areas of the sea, as suggested by the occurrences at Julfa, where it co-occurs with the morphologically similar and closely related genus Permonautilus. Liroceras leptum sp. nov. urn:lsid:zoobank.org:act:43D3AA7B-CCE4-43FD-B6A6-D9B7A27DB882 Fig. 25; Table 19 Diagnosis Species of Liroceras with thinly pachyconic, subinvolute conch (ww/dm ~ 0.68; uw/dm ~ 0.17), moderately depressed whorl profile (ww/wh ~ 1.45) and very high coiling rate (WER ~ 2.30) at a conch diameter of 40 mm. Whorl profile with broadly arched venter and flanks, broadly rounded umbilical margin, convex umbilical wall and moderately deep imprint zone (IZR ~ 0.28). Without sculpture. Suture line with very shallow and wide external, lateral and umbilical lobes. Etymology From Greek ‘λεπτός’ = ‘small, weak’; because of the rather small-sizes material. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 25; MB.C.32138. Paratypes IRAN – Esfahan Province • 2 specimens; same data as for holotype; 2010; Korn et al. leg.; MB.C.32139, MB.C.32140. Description The best-preserved specimen is the obliquely deformed small holotype MB.C.32138 with a conch diameter of 41 mm (Fig. 25B). The conch geometry can only be reconstructed. According to this, the conch is thinly pachyconic and subinvolute (ww/dm = 0.68; uw/dm = 0.17) with a very high coiling rate (WER = 2.31) and a moderately wide whorl overlap (IZR = 0.28). The whorl profile is weakly depressed (ww/wh = 1.44) with a broadly convex venter that merges continuously with the flanks the flanks. The umbilical margin is broadly rounded and the umbilical wall is convex (Fig. 25A). The suture line is Fig. 25. Liroceras leptum sp. nov., holotype MB.C.32138 (Korn et al. 2011 Coll.) from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Dorsal and lateral views. C. Suture line at dm = 25.8 mm, ww = 21.2 mm, wh = 12.8 mm. Scale bar units = 1 mm. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 55 nearly straight and shows very broad and shallow lobes on the area consisting of venter and flanks and the umbilical wall (Fig. 25C). Remarks The material of the new species does not show whether the umbilical extensions characteristic of the genus was present in the adult stage; therefore, assignment to Liroceras is not entirely certain. L. leptum sp. nov. differs from the other Late Permian species of the genus in the opened umbilicus and the slenderer conch; ww/dm ratio for a conch diameter of 40–50 mm is below a value of 0.70, but in the other species it is above 0.80. Genus Paraliroceras Barskov & Shilovsky in Barskov et al., 2014 Type species Paraliroceras kazanicum Barskov & Shilovsky in Barskov et al., 2014; original designation. Diagnosis Genus of the family Liroceratidae with pachyconic, subinvolute conch. The conch is rapidly increasing in height with a high coiling rate (WER = 2.30–2.90). Whorls moderately embracing, whorl profile reniform; umbilical margin pronounced, narrowly rounded. Adult ornament with fine growth lines with a fairly deep ventral sinus. Septa without inflexions, slightly concave. Suture line simple, nearly straight to straight with a shallow, broadly rounded internal lobe. The siphuncle has a position between the centre of the septum and the venter. Included species Western Russia (Barskov et al. 2014): Paraliroceras kazanicum Barskov & Shilovsky in Barskov et al., 2014, Roadian. Central Iran (this paper): Paraliroceras macrogaster sp. nov., Wuchiapingian. Remarks Paraliroceras is similar to Liroceras and differs mainly in the pronounced umbilical margin, which is narrowly rounded in Paraliroceras but usually broad and evenly rounded in Liroceras. The species of Paraliroceras are more widely umbilicate than most known species of Liroceras. Paraliroceras macrogaster sp. nov. urn:lsid:zoobank.org:act:0AF97520-0593-4555-9D0F-96A5FBF603A6 Fig. 26; Table 20 Diagnosis Species of Paraliroceras with thinly globular, subinvolute conch (ww/dm ~ 0.86; uw/dm ~ 0.23), moderately depressed whorl profile (ww/wh ~ 1.90) and very high coiling rate (WER ~ 2.35) at a conch diameter of 60 mm. Whorl profile with broadly arched venter and flanks, narrowly rounded umbilical Table19. Reconstructed conch dimensions (in mm) and ratios of Liroceras leptum sp. nov. from Baghuk Mountain. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32139 53.0 34.0 23.0 10.5 17.0 0.64 1.48 0.20 2.17 0.26 MB.C.32138 41.0 28.0 19.5 7.0 14.0 0.68 1.44 0.17 2.31 0.28 European Journal of Taxonomy 1019: 1–76 (2025) 56 Fig. 26. Paraliroceras macrogaster sp. nov. from the Araxoceras beds of the Hambast Formation at Baghuk Mountain. A. Holotype MB.C.32141 (Korn et al. 2011 Coll.), dorsal, lateral and ventral views. B. The same specimen, reconstruction of apertural view. C. The same specimen, suture line at dm = 54.5 mm, wh = 23.5 mm. D. Paratype MB.C.32142 (Korn et al. 2011 Coll.), ventral and lateral views. E. The same specimen, reconstruction of apertural view. F. The same specimen, suture line at dm = 40.5 mm, ww = 35.8 mm, wh = 21.6 mm. Scale bar units = 1 mm. KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 57 two genera show a much higher coiling rate (WER above 3.00) than Baghuknautilus (WER around 2.50) and a much more pronounced subangular to angular umbilical margin. Baghuknautilus gen. nov. also has similarity to the Triassic genus Paranautilus (Kummel 1953; Sobolev 1989), but this differs in the more dorsal position of the siphuncle and the presence of an annular process. In addition, most species of Paranautilus have a convex umbilical wall. Baghuknautilus aplomorphus gen. et sp. nov. urn:lsid:zoobank.org:act:0E6D1116-BB35-4615-832A-A52849FB4934 Fig. 29; Table 22 Diagnosis Species of Baghuknautilus gen. nov. with thinly discoidal, involute conch (ww/dm ~ 0.40; uw/dm ~ 0.10), weakly compressed whorl profile (ww/wh ~ 0.65) and extremely high coiling rate (WER ~ 2.55) at a conch diameter of 60 mm. Whorl profile with convex venter, convex and convergent flanks, narrowly rounded umbilical margin, a steep umbilical wall and moderately wide imprint zone (IZR ~ 0.30). Suture line with a very shallow external lobe and an asymmetric, broadly rounded lateral lobe. Etymology From the Greek ‘ἁπλόος’ = ‘simple’ and ‘μορφή’ = ‘form’; because of the rather simple conch morphology. Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 29A–C; MB.C.32146. Paratype IRAN – Esfahan Province • 1 specimen; Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 29D–E; MB.C.32147. Description Holotype MB.C.32146 is an incomplete, but on the left side rather well-preserved fully chambered specimen with a conch diameter of 83 mm (Fig. 29A). Some conch parameters can only be reconstructed. The conch is thinly discoidal and involute (ww/dm ~ 0.40; uw/dm = 0.10). The whorl profile is weakly compressed (ww/wh ~ 0.64) with a convex venter and convex, convergent flanks. The umbilical margin is narrowly rounded and the umbilical wall is steep and convex (Fig. 29B). The last volution possesses about 22 phragmocone chambers (CLI = 16.5) with an indication of crowding at the end. The siphuncle has a dorsocentral position. The suture line shows a small and very shallow lobe on venter, a broadly rounded asymmetric lateral lobe with steeper dorsal flanks and a shallow umbilical lobe (Fig. 29C). Paratype MB.C.32147 is a bilaterally corroded, fully chambered specimen with a conch diameter of 60 mm (Fig. 29E). Some conch parameters on the last half volution can only be reconstructed. The conch is thinly discoidal and involute (ww/dm = 0.42; uw/dm = 0.12) with an extremely high coiling rate (WER = 2.54) and a deep whorl overlap (IZR = 0.32). The whorl profile is moderately compressed (ww/wh = 0.76) with a convex venter and convex convergent flanks (Fig. 29D). The suture line shows a shallow, rounded lobe on venter and a broadly rounded slightly asymmetric lateral lobe with steeper dorsal flanks. European Journal of Taxonomy 1019: 1–76 (2025) 64 Fig. 29. Baghuknautilus aplomorphus gen. et sp. nov. from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Holotype MB.C.32146 (Korn et al. 2011 Coll.), lateral view. B. The same specimen, reconstruction of apertural view. C. The same specimen, suture line at dm = 72.5 mm, wh = 38.8 mm. D. Paratype MB.C.32147 (Korn et al. 2011 Coll.), reconstruction of apertural view. E. The same specimen, dorsal and lateral views. Scale bar units = 1 mm. Table 22. Conch dimensions (in mm) and ratios of Baghuknautilus aplomorphus gen. et sp. nov.; reconstructed values in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32146 83.4 33.0 51.5 8.2 – 0.40 0.64 0.10 – – MB.C.32147 60.1 25.0 33.0 7.3 22.4 0.42 0.76 0.12 2.54 0.32 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 65 Remarks Baghuknautilus aplomorphus gen. et sp. nov. differs from Shahrezanautilus ghaderii gen. et sp. nov. by the considerably slenderer conch; the ww/dm ratio is about 0.40 in B. aplomorphus but about 0.60 in S. ghaderii. The coiling rate is much lower in B. aplomorphus (WER higher about 2.50 in comparison with more than 3.00 in S. ghaderii). Genus Shahrezanautilus gen. nov. urn:lsid:zoobank.org:act:449ADF07-95B8-481E-8C4B-4114FD3DC347 New genus E – Korn 2025: 69. Type species Shahrezanautilus weyeri gen. et sp. nov. Diagnosis Genus of the family Julfanautilidae with thinly pachyconic, subinvolute conch. Conch rapidly increasing in height with an extraordinarily high coiling rate (WER higher than 3.00). Whorls weakly embracing, whorl profile weakly depressed. Venter broadly rounded, umbilical wall flat and steep. Adult ornament with extremely fine growth lines. Septa without inflexions, slightly concave. Suture line simple with a shallow external lobe and a broadly rounded lateral lobe. Etymology Named after the city of Shahreza, the type locality of the type species. Included species Central Iran (this paper): Shahrezanautilus weyeri gen. et sp. nov., Wuchiapingian; Shahrezanautilus ghaderii gen. et sp. nov., Wuchiapingian. Remarks Shahrezanautilus gen. nov. differs from Julfanautilus in the broadly rounded venter, which in Julfanautilus has a concave shape. Shahrezanautilus weyeri gen. et sp. nov. urn:lsid:zoobank.org:act:FBA54AF0-D7E6-4EBB-BBFA-2563F160A99D Fig. 30; Table 23 Diagnosis Species of Shahrezanautilus gen. nov. with a thinly pachyconic, subinvolute conch (ww/dm ~ 0.70; uw/dm ~ 0.25), weakly depressed whorl profile (ww/wh ~ 1.40) and extraordinarily high coiling rate (WER ~ 3.40) at a conch diameter of 60 mm. Whorl profile with a weakly convex venter, a pronounced ventrolateral shoulder, flatly convex and weakly convergent flanks, a subangular umbilical margin, a steep and flattened umbilical wall and a small imprint zone (IZR ~ 0.10). Suture line with a broadly rounded and shallow external lobe and a broadly rounded lateral lobe. Etymology Named after Dieter Weyer (Berlin), who collected the holotype of the new species. Type material Holotype IRAN – Esfahan Province • Shahreza; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2002; D. Weyer leg.; illustrated in Fig. 30; MB.C.32148. European Journal of Taxonomy 1019: 1–76 (2025) 66 Paratype IRAN – Esfahan Province • 1 specimen; Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; MB.C.32149. Description Holotype MB.C.32148 is an incomplete, fully chambered specimen with a phragmocone diameter of at least 75 mm (Fig. 30A). It has been preserved without remains of the shell. The conch is, at 57 mm diameter, thinly pachyconic and subinvolute (ww/dm = 0.68; uw/dm = 0.26) with and extraordinarily high coiling rate (WER = 3.38) and a small whorl overlap zone (IZR = 0.07). The whorl profile is weakly depressed (ww/wh = 1.39) with a convex venter, a slightly pronounced by rounded ventrolateral shoulder and slightly flattened convergent flanks. The umbilical margin is very distinctive and subangular; it delimitates the broad and nearly flat, almost perpendicular umbilical wall (Fig. 30B). The suture line shows a shallow and broadly rounded external lobe and a twice as wide and deep, broadly rounded lateral lobe (Fig. 30C). The last volution of the phragmocone has slightly more than 20 septa (CLI = 18) and thus some indication for terminal septal crowding. Remarks Shahrezanautilus weyeri gen. et sp. nov. differs from S. ghaderii gen. et sp. nov. in having a much wider umbilicus; the uw/dm ratio is about 0.25 in S. weyeri gen. et sp. nov. but only about 0.15 in S. ghaderii. This difference parallels a difference in the whorl overlap rate, which is only about 0.07 in S. weyeri, but 0.25 in S. ghaderii and in the coiling rate, which is higher in S. weyeri (WER ~3.40 compared to about 3.10 in S. ghaderii). Fig. 30. Shahrezanautilus weyeri gen. et sp. nov., holotype MB.C.32148 (Weyer 2002 Coll.) from the Vedioceras beds of the Hambast Formation at Shahreza. A. Ventral and lateral views. B. Reconstruction of apertural view. C. Suture line at dm = 50.2 mm, ww = 36.3 mm, wh = 26.5 mm. Scale bar units = 1 mm. Table 23. Conch dimensions (in mm) and ratios of Shahrezanautilus weyeri gen. et sp. nov. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32148 57.0 39.0 28.0 15.0 26.0 0.68 1.39 0.26 3.38 0.07 KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 67 Shahrezanautilus weyeri gen. et sp. nov. is difficult to confuse with any other Late Permian nautiloid species due to its specific morphology with a very high, flattened umbilical wall and an angular umbilical margin. The two species Julfanautilus hairapetiani Korn & Ghaderi, 2025 and especially J. ashourii Korn & Ghaderi, 2025 show a slight similarity, although they have a concave venter. Shahrezanautilus ghaderii gen. et sp. nov. urn:lsid:zoobank.org:act:8FA187E3-F00F-44DE-A0FA-32A9E26A7B37 Fig. 31; Table 24 Diagnosis Species of Shahrezanautilus gen. nov. with thinly pachyconic, involute conch (ww/dm ~ 0.62; uw/dm ~ 0.13), weakly depressed whorl profile (ww/wh ~ 1.10) and extraordinarily high coiling rate (WER ~ 3.10) at a conch diameter of 80 mm. Whorl profile with convex venter, convex and convergent flanks, a subangular umbilical margin, a steep umbilical wall and a moderately deep imprint zone (IZR ~ 0.25). Suture line with a very shallow external lobe and a weakly asymmetric, broadly rounded lateral lobe. Etymology Named after Abbas Ghaderi (Mashhad), in honour of his contribution in studying the Permian–Triassic boundary. Fig. 31. Shahrezanautilus ghaderii gen. et sp. nov., holotype MB.C.32150 (Korn et al. 2011 Coll.) from the Vedioceras beds of the Hambast Formation at Baghuk Mountain. A. Reconstruction of apertural view. B. Dorsal and lateral views. C. Suture line at dm = 48.5 mm, ww = 32.5 mm, wh = 29.5 mm. Scale bar units = 1 mm. European Journal of Taxonomy 1019: 1–76 (2025) 68 Type material Holotype IRAN – Esfahan Province • Baghuk Mountain; Hambast Formation, Vedioceras beds (late Wuchiapingian); 2011; Korn et al. leg.; illustrated in Fig. 31; MB.C.32150. Description Holotype MB.C.32150 is a largely chambered specimen with a conch diameter of 84 mm (Fig. 31B), which is heavily corroded on the last half volution. Some of the conch parameters on the last half volution can only be reconstructed. The conch is thinly pachyconic and involute (ww/dm ~ 0.62; uw/dm = 0.13) with an extraordinarily high coiling rate (WER = 3.09) and a moderately deep whorl overlap (IZR = 0.25). The whorl profile is weakly depressed (ww/wh ~ 1.08) with a convex venter, convex convergent flanks, a narrowly rounded umbilical margin and a steep umbilical wall (Fig. 31A). The suture line shows a very shallow, rounded lobe on venter and a broadly rounded, nearly symmetric lateral lobe (Fig. 31C). Remarks Shahrezanautilus ghaderii gen. et sp. nov. differs from S. weyeri gen. et sp. nov. in having a much narrower umbilicus; the uw/dm ratio is about 0.15 in S. ghaderii but about 0.25 in S. weyeri. This difference parallels a difference in the whorl overlap rate, which is about 0.25 in S. ghaderii, but only 0.07 in S. weyeri and in the coiling rate, which is lower in S. ghaderii (WER ~ 3.00 compared to about 3.40 in S. weyeri). Shahrezanautilus ghaderii gen. et sp. nov. has some similarities with Julfanautilus ashourii Korn & Ghaderi, 2025 from Julfa. Like S. ghaderii, J. apertum has a stout, involute conch (ww/dm ~ 0.65), which is more umbilicated in J. apertum (uw/dm ~ 0.25 in J. apertum, but only 0.15 in S. ghaderii). The main difference between the two species is the shape of the venter, which is convex in S. ghaderii and concave in J. apertum. Discussion The Late Permian Hambast Formation of sections at Baghuk Mountain (Central Iran) has yielded diverse nautiloid assemblages. These species belong to 14 genera, six of which are new: Lutonautilus gen. nov., Epitainoceras gen. nov., Ocunautilus gen. nov., Aifinautilus gen. nov., Baghuknautilus gen. nov. and Shahrezanautilus gen. nov. Based on new material, a total of 24 new species is described. The material comes from four stratigraphic units, in ascending order: • Araxoceras beds (early Wuchiapingian), nine species: Epitainoceras lutense gen. et sp. nov., Serometacoceras pentagonum sp. nov., Domatoceras myloide sp. nov., Ocunautilus diplodocus gen. et sp. nov., Ocunautilus coelodesmus gen. et sp. nov., Ocunautilus tachytrephus gen. et sp. nov., Aifinautilus icanus gen. et sp. nov., Paraliroceras macrogaster sp. nov. and Permonautilus adelphidus sp. nov. • Prototoceras beds (early Wuchiapingian), one species: Tardunautilus aperimos sp. nov. • Vedioceras beds (late Wuchiapingian), 12 species: Lutonautilus cratus gen. et sp. nov., Lutonautilus elachus gen. et sp. nov., Lutonautilus cymus gen. et sp. nov., Foordiceras eicosacanthum sp. nov., Foordiceras decacanthum sp. nov., Foordiceras ascetum sp. nov., Domatoceras canonium sp. nov., Table 24. Conch dimensions (in mm) and ratios of Shahrezanautilus ghaderii gen. et sp. nov.; reconstructed values in italics. Nr. dm ww wh uw ah ww/dm ww/wh uw/dm WER IZR MB.C.32150 83.5 52.0 48.0 10.5 36.0 0.62 1.08 0.13 3.09 0.25 MB.C.32150 47.5 30.5 28.5 7.5 – 0.64 1.07 0.16 – – KORN D. & HAIRAPETIAN V., Late Permian nautiloids from Baghuk Mountain (Central Iran) 69 Domatoceras ocomphalum sp. nov., Liroceras leptum sp. nov., Baghuknautilus aplomorphus gen. et sp. nov., Shahrezanautilus weyeri gen. et sp. nov. and Shahrezanautilus ghaderii gen. et sp. nov. • Paratirolites beds (late Changhsingian), two species: Tainoceras hystatum sp. nov. and Azarinautilus phorminx sp. nov. With 24 species, the assemblage from Baghuk is one of the most diverse Late Permian occurrences of coiled nautiloids. With 22 Wuchiapingian species alone, it is the second species-rich assemblage for this interval after the Transcaucasian region. Acknowledgements We are indebted to Lucyna Leda (Zamarte) and Abbas Ghaderi (Mashhad) for participating in the field trips and collecting many of the specimens described here. 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