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Not to be confused with Parahelicampodus or Paredestus.
Gasmasque/sandbox2
Temporal range: Early Permian (Asselian-Artinskian),
~298.9-283.5 Ma
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: †Eugeneodontida
Family: †Helicoprionidae
Genus: †Parahelicoprion
Karpinsky, 1924
Type species
Helicoprion clerci
Karpinsky, 1916
Species
  • P. clerci Karpinsky, 1916
  • P. mariosuarezi Merino-Rodo & Janvier, 1986
Synonyms
  • Helicoprion? (Karpinsky, 1899)
  • Physonemus? (Agassiz, 1843)

Parahelicoprion (meaning "near coiled saw" or "near Helicoprion") is an extinct genus of shark-like cartilaginous fish known from the early Permian Artinskian Beds of the Ural Mountains of Russia and the Copacabana Formation of Bolivia. Members of the genus possessed a row of large, serrated tooth crowns on the midline of the lower jaw, known as a tooth whorl. The characteristics of this whorl are unique to fishes of the order Eugeneodontida, and more specifically the family Helicoprionidae, to which Parahelicoprion belongs. The genus name refers to the presumed relation with Helicoprion ('coiled saw'), another eugeneodont from the Ural Mountains which bore a similar symphyseal tooth arrangement. Two species of Parahelicoprion are assigned; the Russian P. clerci and the Bolivian P. mariosuarezi.

The holotype of Parahelicoprion clerci is poorly preserved, consisting of only six partial tooth crowns. That of the Bolivian P. mariosuarezi similarly consists of only nine partial crowns, all but one of which are missing their outer edges. Estimates of the extent of the complete whorl, body size, and ecology of Parahelicoprion are highly speculative as a result of its incomplete fossils, although it is assumed to have been very large, predatory, and pelagic. When first described, P. clerci was considered a member of the related genus Helicoprion, although its initial describer, Alexander Karpinsky, later separated it into its own genus. It has since been suggested that this genus may indeed represent a junior synonym of Helicoprion or a paraphyletic, non-diagnostic taxon.

Discovery and naming

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The location of Krasnoufimsk (red), where the holotype of P. clerci was discovered

The type specimen of Parahelicoprion, first described in 1916, was initially named as Helicoprion clerci by influential Russian geologist Alexander Karpinsky. This specimen was found in the Ural Mountains region of Russia,[1][2] in strata dated to the Artinskian stage of the Cisuralian epoch (early Permian).[3][4] Karpinsky himself reassigned this specimen to its own genus in 1924,[5] although he had already informally referred to it as Parahelicoprion in a publication two years prior.[6] The species name honors Onisime Jegorovič Klerk, who at the time was the president of the Ural Naturalist's Society. The type specimen of the species was found near the town of Krasnoufimsk,[2][7] and a cast of this material was subsequently displayed at the Krasnoufimsk Museum.[8]

A second species, Parahelicoprion mariosuarezi, was described and tentatively assigned to the genus in 1986. This species is based on a single specimen (designated no. 6097, YPFB) discovered in the Bolivian Copacabana Formation and dated to the Asselian stage of the early Permian.[9][10] The holotype, a three-dimensional partial tooth whorl,[10] was found preserved in a layer of calcarious red sandstone. The species is named in honor of Dr. Mario Suarez-Riglos,[9] and the type specimen is currently housed in the collection of the Noel Kempff Mercado Natural History Museum.[11]

The genus derives its name from the Greek prefix -para, meaning "near" or "beside" and from the name of the related Helicoprion,[12][6] itself meaning "coiled saw'" or "spiral saw".[13][14] In scientific nomenclature, -para is often used to denote similarity or relation.[15][16]

Description

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Highly speculative life reconstruction of Parahelicoprion clerci, which conforms to that of P. mariosuarezi featured in Phillipe Janvier's Early Vertebrates (1996)

Both Parahelicoprion species are extremely incompletely known.[9][17] The only material which has been assigned confidently to the genus consist of fragments of the lower symphyseal tooth whorl, which significantly limits available information.[18][8] Large, forward-arching fin spines under the ichthyodorulite form-genus Physonemus have been associated with Parahelicoprion and related eugeneodonts,[3][19] with the specific species P. grandis suggested to correspond to Parahelicoprion.[19][20] These sickle-like spines are now believed by most researchers to represent the copulatory organs of symmoriiform fishes,[4][21][22] and members of the Eugeneodontida are widely assumed to have lacked fin spines.[4][23]

The postcranial anatomy of eugeneodonts has been suggested to vary little between genera,[23] indicating that, like their smaller relatives, both species of Parahelicoprion possessed long, fusiform bodies with lunate caudal fins, and that they lacked pelvic, anal, and second dorsal fins.[9][23] In his 1996 textbook Early Vertebrates, researcher Philippe Janvier reconstructs P. mariosuarezi (which he contributed to describing) with a proportionally very small, short tooth whorl situated at the tip of a pointed, greatly elongated pair of jaws.[24] This anatomy is also suggested in the animal's initial description, and is assumed based on the partial skull of Sarcoprion edax and the well-preserved fossils of the related caseodontoids.[9][23] Some subsequent authors have assumed the preserved whorl of Parahelicoprion in fact represents a small fragment of a helical whorl indistinguishable from that of Helicoprion.[3][25]

Parahelicoprion clerci

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Teeth of P. clerci illustrated in lateral (3) and anterior cross section (4) views, alongside those of several related eugeneodonts. Shaded areas represent the root

In P. clerci, the known crowns are lined with deep serrations along the anterior edge and crenulations along the sloping, blade-like posterior edge.[6][9][23] The outer tips of the crowns are tall and pointed, and angle towards the anterior of the mouth.[23] The holotype whorl consists of six partial tooth crowns (although Karpinsky illustrates only three)[1][9] and a partial root.[8] The posterior edges of the tooth crowns are described as thinner than the anterior edges and being adapted for cutting. No lateral dentition is known in any specimens of this species.[6] The form of the most complete whorl fragment observed in Parahelicoprion clerci has been compared to that of the potential close relative Sarcoprion by various authors,[4][8][23] although paleontologist Svend Erik Bendix-Almgreen insists that the material of the former is too poorly known for such comparisons to be confidently made.[8]

Parahelicoprion mariosuarezi

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The known whorl of P. mariosuarezi is described as larger than the type species.[9][13] In P. mariosuarezi deep serrations are apparently absent across most of the crown, but several large, pointed denticles do protrude along the lingual (lower) edges of the third to ninth tooth crowns. This species also preserves a single denticle-bearing parasymphyseal tooth along the edge of the whorl, a tooth type which are not known from P. clerci. The holotype of P. mariosuarezi shows the smallest crown was positioned anteriorly, at the very front of the preserved portion of the whorl, and was significantly smaller than the next crown in the sequence.[4][9] This is suggested to indicate that the whorl was short and did not form a helical spiral. In its initial description it is speculated that the holotype whorl of P. mariosuarezi is nearly complete, meaning that the whorl, which as preserved possesses nine tooth crowns,[9] bore far fewer crowns than Helicoprion, which may had between 135-180.[14][26][27] The outer cutting edges of the tooth crowns in P. mariosuarezi are thought to have conformed in shape and orientation to those of the type species.[9]

Classification

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When first named by Karpinsky, Parahelicoprion was considered a member of the family Edestidae, which at that time also included genera such as Helicoprion and Agassizodus.[6] While the relation and classification of edestid and helicoprionid fishes was variable throughout the 20th century,[23][8][28] Parahelicoprion is today considered to be a member of the family Helicoprionidae within the monophyletic order Eugeneodontida (alternately spelled Eugeneodontiformes). The helicoprionids (described as agassizodontids by some authors) are defined by possessing tooth whorls with forward angled, blade-like tooth crowns and, in many genera, tooth roots which are completely fused. Members of the group also possessed a laterally positioned pavement of flattened crushing teeth, although these have not been confidently identified in either species of Parahelicoprion. Other aspects of the group's jaws and skull are only rarely preserved, and nothing is known of their postcranial anatomy.[23][4] Conclusions about the relations of both species of Parahelicoprion are based solely on the characteristics of the highly fragmentary dentition.

Helicoprion bessonowi (left) and Sarcoprion edax (right), both of which are considered close relatives of Parahelicoprion. Specimens on display at the Moscow Paleontological Museum

In a 1924 publication, Karpinsky suggested that P. clerci may represent a directly intermediate, transitional form between the "primitive" genus Campodus and the more derived Helicoprion,[20] a conclusion agreed with by Nielsen (1952).[29] Svend Erik Bendix-Almgreem, in a 1976 publication, suggested that Parahelicoprion may have been related to a proposed radiation of whorl toothed cartilaginous fish unrelated to the helicoprionids and edestids. This lineage was proposed to also consist of Erikodus, Fadenia, and Sarcoprion,[8][23] with P. clerci considered a possible member due to similarities with the latter taxon.[8] Rainer Zangerl (1981) considered Parahelicoprion to be the sister taxon to Campyloprion in his morphological analysis of all (then known) members of the newly proposed order Eugeneodontida.[23] Following Zangerl's analysis, authors Dagmar Merino-Rodo and Phillipe Janvier concluded that the genus lacks any defining derived characteristics, which puts its validity and status as a monophyletic group into question and complicates the matter of assigning new species.[9] In a 2018 publication, paleobotanist Serge Naugholnykh proposes that P. clerci specimens simply represent especially large individuals of Helicoprion and that the two genera are synonymous,[3][25] although subsequent papers have continued to recognize Parahelicoprion as a valid genus of helicoprionid eugeneodont containing two species.[17][30][31]

Paleobiology and paleoecology

[edit]

Habitat and ecology

[edit]
A map of Earth as it appeared during the Cisuralian epoch

Parahelicoprion was a carnivore which inhabited marine environments.[9][10][32] It has been suggested to have been the apex predator of its ecosystem,[3] with the blade-like serrated tooth whorl being adapted for cutting prey.[6][9][13] While multiple feeding styles are thought to have been present among different genera of edestoids,[26][30] it has been hypothesized that many members of the Helicoprionidae were molluscivorous and fed primarily on ammonoid and coleoid cephalopods.[26][33]

The teeth of Artiodus prominens, a euselachian stem-group shark known from the Arta Beds of Krasnoufimsk[7]

The Artinskian deposits of Krasnoufimsk, or the Arta Beds, were deposited in a shallow sea basin between the Boreal and Tethys oceans. These fossil beds are made up of the lower (older) Divjinskian or Divya Formation and the upper (younger) Sarginskian Formation, and are composed predominantly of marls and limestones.[3][7][34] During the early Permian, reef habitats made up of bryozoans and rugose corals were present, which were inhabited by a diverse assemblage of trilobites,[7] goniatite and nautiloid cephalopods,[34] and fishes.[3] In addition to Parahelicoprion clerci, the Divya Formation yields a huge variety of chondrichthyan fossils, including the remains of euselachian sharks, hybodonts, symmoriiformes, petalodonts and cochliodonts.[7] The morphologically similar helicoprionid Helicoprion bessonowi is also known from numerous tooth whorls collected in the Divya Formation.[3][7]

The Copacabana Formation represented a shallow marine habitat, somewhat older than the Arta Beds and dated to the boundary between the Carboniferous and the Permian. Of the formation's two strata which preserve fish fossils, Parahelicoprion is known only from the upper (younger) layer, while the majority of observed species come from a slightly older layer below it. Among these species, actinopterygians (ray-finned fish) and holocephalans have been identified. The known fossils of holocephalans include remains of the large petalodont similar to Megactenopetalus as well as tooth-plates of cartilaginous fishes similar to Lagarodus or Helodus, both believed to be bottom dwelling, durophageous fishes. Teeth and scales belonging to bony fish in the family Platysomidae are also known, and isolated teeth suggest that cladodont sharks (Identified by Merino-Rodo and Janvier as Cladodus) were also present in the environment.[3][32] The teeth of jawless, fish-like vertebrates called conodonts are abundant, and it is from these index fossils that the age of the formation has been determined. Marine invertebrates have also been found at the site, and include bivalves, brachiopods, trilobites, crinoids and bryozoans. While lower fish-bearing strata of the Copacabana Formation are believed to represent a diverse benthic reef community, Merino-Rodo and Janvier suggest that the sandstones which compose the upper fish-bearing layer and which preserve the whorl of Parahelicoprion may have formed in an even shallower, intertidal habitat, and that the type of P. mariosuarezi represents an animal killed in a stranding.[9] In spite of the difference in time and proposed habitat, Janvier has subsequently described and illustrated the aforementioned species coexisting.[24]

Estimated length

[edit]

While the known tooth crowns of the genus are considered to be among the largest of the eugeneodonts; believed to be up to 15 cm (6 in) in height when complete,[35] estimates of Parahelicoprion's total body size have been described as "controversial".[36] Paleoichthyologist Richard Lund is quoted as saying, in Doug Perrine's 1999 book Sharks and Rays, that Parahelicoprion "... might have been over 30 meters (100 ft) in lengths - perhaps the largest fish of all time", a claim apparently made based on extrapolating size from the preserved section of the whorl.[35] A similar estimate was provided by author and illustrator Richard Ellis in his 2003 book Aquagenesis: The Origin and Evolution of Life in the Sea. Ellis states that, in spite of the poor quality of the known material "... unless it (Parahelicoprion) was an animal with a gigantic head or outlandishly oversized teeth, it had to have been a monster, at least 100 feet long and maybe more." This conclusion was reached based on comparisons between the height of the teeth in Carcharocles megalodon, which the teeth of Parahelicoprion are said to exceed in size.[13] Length estimates for eugeneodont fishes in excess of 11 meters (36 ft) have not been published in academic, peer-reviewed literature.[36]

Oleg Lebedev, a researcher from the Palaeontological Institute of the Russian Academy of Sciences, estimated in a 2009 publication that the largest specimens of the closely related (and potentially synonymous) Helicoprion bessonowi may have been between 5-8 meters (16-26 ft) in total body length; a measurement based on assumptions about its head-to-whorl proportions in comparison to the related caseodonts.[36][26] A later study proposed a most plausible total length of up to 7 meters (23 ft) for Helicoprion and its relatives.[36] Due to the fragmentary nature of its material, it has been considered unreasonable by some researchers to give precise total length estimates for Helicoprion, Parahelicoprion, or any other members of edestoidea.[18][36] Though its exact maximum size is not known, both species of Parahelicoprion were likely among the largest animals of their respective environments,[3][9] and they and other edestoids likely represented the some of the largest fishes of the Paleozoic era.[37][38][39]

Extinction

[edit]

The latest known occurrence of the genus is the Artinskian stage of the Permian,[7] and it is assumed to have been extinct by the end of the Cisuralian epoch.[31] This may have been due to climatic changes associated with the late Paleozoic ice ages, although the scarcity of available information on the animal's size and niche makes such conclusions tenuous.[36] Alongside Parahelicoprion, many cartilaginous fish genera of the Divya Formation disappear from the fossil record at the close of the Artinskian stage.[7]

See also

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References

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  1. ^ a b Karpinskly, A. P. (1916). "On a new species of Helicoprion (Helicoprion clerci, n. sp.)". Bulletin de l'Académie Impériale des Sciences de Saint Pétersbourg (in Russian).
  2. ^ a b "Notes". Nature. 98 (2447): 54–55. 21 September 1916 – via Biodiversity Heritage Library.
  3. ^ a b c d e f g h i j Naugolnykh, S.V. (2018). "Artinskian (Early Permian) Sea Basin and Its Biota (Krasnoufimsk, Cis-Urals)". Stratigraphy and Geological Correlation. 26 (7): 734–754. Bibcode:2018SGC....26..734N. doi:10.1134/S0869593818070080. S2CID 135304766.
  4. ^ a b c d e f Ginter, Michał; Hampe, Oliver; Duffin, Christopher J. (2010). Handbook of paleoichthyology: teeth. München: F. Pfeil. ISBN 978-3-89937-116-1.
  5. ^ Karpinsky, A.P. (1924). "Helicoprion (Parahelicoprion n.g.) clerci". Zapiski Ural'skogo Obshchestva Estestvoispytatelei. 34: 1–10.
  6. ^ a b c d e f Karpinsky, Alexander (1922). "Notes on the dental segments of Edestidae and their orientation". Bulletin of the Russian Academy of Sciences (in Russian): 379–388 – via Google Books.
  7. ^ a b c d e f g h Ivanov, Alexander; Duffin, Christopher; Naugolnykh, Serge (2017). "A new euselachian shark from the Early Permian of the Middle Urals, Russia". Acta Palaeontologica Polonica. 62. doi:10.4202/app.00347.2017. ISSN 0567-7920.
  8. ^ a b c d e f g h Bendix-Almgreen, Svend Erik (1976). "Palaeovertebrate faunas of Greenland". Geology of Greenland. doi:10.22008/GPUB/38226.
  9. ^ a b c d e f g h i j k l m n o p Merino-Rodo, Dagmar; et al. (1986). "Chondrichthyan and actinopterygian remains from the Lower Permian Copacabana Formation of Bolivia". Geobios. 19 (4): 479–493. Bibcode:1986Geobi..19..479M. doi:10.1016/S0016-6995(86)80005-5.
  10. ^ a b c "PBDB Taxon". paleobiodb.org. Retrieved 15 October 2024.
  11. ^ "Colleciones Cientificas". museonoelkempff.org. Retrieved 11 October 2024.
  12. ^ "para- | Etymology of the prefix para". etymonline.com. Retrieved 22 October 2024.
  13. ^ a b c d Ellis, Richard (2003). Aquagenesis: the origin and evolution of life in the sea. New York, N.Y: Penguin. ISBN 978-0-14-200156-1.
  14. ^ a b Eastman, C. R. (1900). "Karpinsky's genus Helicoprion: a review". The American Naturalist. 34 (403) – via JSTOR.
  15. ^ "Para Definition and Meaning". Merriam-Webster. Retrieved 23 October 2024.
  16. ^ Mutter, Raoul J.; Neuman, Andrew G. (2008). "New eugeneodontid sharks from the Lower Triassic Sulphur Mountain Formation of Western Canada". Geological Society, London, Special Publications. 295 (1): 9–41. doi:10.1144/SP295.3. ISSN 0305-8719.
  17. ^ a b Sansom, Ivan J. (2024-01-24). "Supplementary material from "The skeletal completeness of the Palaeozoic chondrichthyan fossil record"". Royal Society Open Science. doi:10.6084/m9.figshare.c.7041560.v1.
  18. ^ a b Maisey, John G.; Bronson, Allison W.; Williams, Robert R.; McKinzie, Mark (2017-05-04). "A Pennsylvanian 'supershark' from Texas". Journal of Vertebrate Paleontology. 37 (3): e1325369. doi:10.1080/02724634.2017.1325369. ISSN 0272-4634.
  19. ^ a b Baird, Donald (1957). "A Physonemus Spine from the Pennsylvanian of West Virginia". Journal of Paleontology. 31 (5): 1011–1018 – via JSTOR.
  20. ^ a b Karpinsky, Alexander (1924). "Sur une nouvelle troouvaille de restes de Parahelicoprion et sur relations de ce genre avec Campodus (On a New Find of Remains of Parahelicoprion and on the Relations of This Genus with Campodus)". Soc. Geol. Belg. Livre Jubilaire (in Russian): 125–137.
  21. ^ Lund, Richard (1986-03-07). "On Damocles serratus , nov. gen. et sp. (Elasmobranchii: Cladodontida) from the Upper Mississippian Bear Gulch Limestone of Montana". Journal of Vertebrate Paleontology. 6 (1): 12–19. doi:10.1080/02724634.1986.10011594. ISSN 0272-4634.
  22. ^ Maisey, John G. (2009-03-12). "The spine-brush complex in symmoriiform sharks (Chondrichthyes; Symmoriiformes), with comments on dorsal fin modularity". Journal of Vertebrate Paleontology. 29 (1): 14–24. doi:10.1671/039.029.0130. ISSN 0272-4634.
  23. ^ a b c d e f g h i j k Zangerl, Rainer (1981). Handbook of Paleoichthyology Volume: 3A: Chondrichthyes 1 (1st ed.). Verlag Dr. Friedrich Pfeil. pp. 74–94. ISBN 978-3899370454.
  24. ^ a b Janvier, Philippe (1996). Early vertebrates. Oxford science publications. Oxford : New York: Clarendon Press ; Oxford University Press. p. 22. ISBN 978-0-19-854047-2.
  25. ^ a b Наугольных, с.в.; Наумкин, д.в. (2023). "ПАЛЕОЭКОЛОГИЯ И ПАЛЕОИХНОЛОГИЯ НИЖНЕПЕРМСКИХ ОТЛОЖЕНИЙ РАЙОНА Г. КРАСНОУФИМСК (СВЕРДЛОВСКАЯ ОБЛ.)". Горное эхо (in Russian) (4): 19–38. doi:10.7242/echo.2023.4.3. ISSN 2658-5227.
  26. ^ a b c d Lebedev, O. A. (2009). "A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function". Acta Zoologica. 90 (s1): 171–182. doi:10.1111/j.1463-6395.2008.00353.x. ISSN 0001-7272.
  27. ^ Tapanila, Leif; Pruitt, Jesse (2013). "Unraveling species concepts for the Helicoprion tooth whorl". Journal of Paleontology. 87 (6): 965–983. doi:10.1666/12-156. ISSN 0022-3360.
  28. ^ Moy-Thomas, J. A.; Miles, Roger S. (1971). Palaeozoic fishes (2d ed., extensively rev ed.). Philadelphia: Saunders. ISBN 978-0-7216-6573-3.
  29. ^ Nielsen, Egil (30 August 1952). "On new or little known Edestidae from the Permian and Triassic of East Greenland". Meddelelser om Grønland. 144: 5–55.
  30. ^ a b Lebedev, Oleg A.; Itano, Wayne M.; Johanson, Zerina; Alekseev, Alexander S.; Smith, Moya M.; Ivanov, Aleksey V.; Novikov, Igor V. (2022). "Tooth whorl structure, growth and function in a helicoprionid chondrichthyan Karpinskiprion (nom. nov.) (Eugeneodontiformes) with a revision of the family composition". Earth and Environmental Science Transactions of The Royal Society of Edinburgh. 113 (4): 337–360. doi:10.1017/S1755691022000251. ISSN 1755-6910.
  31. ^ a b Schnetz, Lisa; Dunne, Emma; Feichtinger, Iris; Butler, Richard J.; Coates, Michael I.; Sansom, Ivan J. (9 January 2024). "Data -- Rise and diversification of chondrichthyans in the Paleozoic". Dryad. doi:10.5061/dryad.zpc866tfn.
  32. ^ a b Soruco, Ramiro Suárez (1991). Fosiles y Facies de Bolivia. Revista Tecnica de YPFB. p. 390.
  33. ^ Ramsay, Jason B.; Wilga, Cheryl D.; Tapanila, Leif; Pruitt, Jesse; Pradel, Alan; Schlader, Robert; Didier, Dominique A. (2015). "Eating with a saw for a jaw: Functional morphology of the jaws and tooth‐whorl in H elicoprion davisii". Journal of Morphology. 276 (1): 47–64. doi:10.1002/jmor.20319. ISSN 0362-2525.
  34. ^ a b Mironenko, A.A.; Naugolnykh, S.V. (2022-12-19). "Lower and upper jaws of the Early Permian goniatitid ammonoids". Lethaia. 55 (4): 1–9. doi:10.18261/let.55.4.2. ISSN 0024-1164.
  35. ^ a b Perrine, Doug (15 October 2005). Sharks and Rays. Colin Baxter Photography Ltd. p. 24. ISBN 978-1841072913.
  36. ^ a b c d e f Gayford, Joel H.; Engelman, Russell K.; Sternes, Phillip C.; Itano, Wayne M.; Bazzi, Mohamad; Collareta, Alberto; Salas‐Gismondi, Rodolfo; Shimada, Kenshu (2024). "Cautionary tales on the use of proxies to estimate body size and form of extinct animals". Ecology and Evolution. 14 (9). doi:10.1002/ece3.70218. ISSN 2045-7758. PMC 11368419. PMID 39224151.
  37. ^ Tapanila, Leif; Pruitt, Jesse; Wilga, Cheryl D.; Pradel, Alan (2020). "Saws, Scissors, and Sharks: Late Paleozoic Experimentation with Symphyseal Dentition". The Anatomical Record. 303 (2): 363–376. doi:10.1002/ar.24046. ISSN 1932-8486.
  38. ^ Engelman, Russell K. (2023-02-21). "A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira)". Diversity. 15 (3). doi:10.3390/d15030318x. ISSN 1424-2818.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  39. ^ Godfrey, Steven J. (25 September 2018). "The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA". Smithsonian Contributions to Paleontology (100): 47.
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Category:Agassizodontidae Category:Prehistoric cartilaginous fish genera Category:Permian cartilaginous fish Category:Permian fish of Asia Category:Fossils of Russia Category:Prehistoric fish of South America Category:Permian Bolivia Category:Fossils of Bolivia Category:Fossil taxa described in 1916

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