Eugeneodontida

Not to be confused with Eugeneodontidae.
Eugeneodontida
Temporal range: 330.9–247.2 Ma Early Carboniferous (Serpukhovian) to Early Triassic (Olenekian)
Helicoprion davisii
Edestus heinrichi
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Holocephali
Order: †Eugeneodontida
Zangerl, 1981
Synonyms
  • Eugeneodontiformes[1]
Helicoprion bessonovi, teeth at the front of the lower jaw (reversed for more natural position)
Restoration of Romerodus (Caseodontidae)

The Eugeneodontida, sometimes also called Eugeneodontiformes, is an extinct and poorly known order of cartilaginous fishes. They possessed "tooth-whorls" on the symphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lacked pelvic fins and anal fins.[2] The palatoquadrate was either fused to the skull or reduced. Now determined to be within the Holocephali, their closest living relatives are chimaeras.[3] The eugeneodonts are named after paleontologist Eugene S. Richardson, Jr.[4] The group first appeared in the fossil record during the late Mississippian (Serpukhovian).[5] The youngest eugeneodonts are known from the Early Triassic.[6] The geologically youngest fossils of the group are known from the Sulphur Mountain Formation (western Canada), Vardebukta Formation (Svalbard, Norway) and Wordie Creek Formation (Greenland).

Members of the Eugeneodontida are further classified into different families, the most well-preserved members that have been discovered are commonly placed within the families Helicoprionidae ("spiral saws"), and Edestidae ("those which devour"), the former containing the genera Helicoprion, Sarcoprion, and Parahelicoprion, and the latter containing the genera Edestus, Lestrodus, and Metaxyacanthus. All eugeneodonts are thought to have been obligate carnivores, with each genus having specialized feeding behaviors, territory ranges, and specific prey.

Among the eugeneodonts, some members of the superfamily Edestoidea are probably the largest marine animals of their time, with the Late Carboniferous Edestus estimated to reach about or exceeding 6.7 metres (22 ft) in length,[7][8] with some Early Permian Helicoprion suggested to be over 7.6 metres (25 ft) long by some estimates[9] (though the body length estimates for both genera are somewhat speculative due to both only being known from skull material[7][8][9]).

  1. ^ Cite error: The named reference paleodb was invoked but never defined (see the help page).
  2. ^ 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: 171–182. doi:10.1111/j.1463-6395.2008.00353.x. ISSN 0001-7272.
  3. ^ Cite error: The named reference Tapanila_2013 was invoked but never defined (see the help page).
  4. ^ Zangerl, R. (1981). Handbook of Paleoichthyology. Volume 3A. Chondrichthyes I. Paleozoic Elasmobranchi. Stuttgart: Gustav Fischer Verlag. ISBN 978-3-89937-045-4.
  5. ^ Hodnett, John-Paul M.; Elliott, David K. (December 2018). "Carboniferous chondrichthyan assemblages from the Surprise Canyon and Watahomigi formations (latest Mississippian–Early Pennsylvanian) of the western Grand Canyon, Northern Arizona". Journal of Paleontology. 92 (S77): 1–33. doi:10.1017/jpa.2018.72. ISSN 0022-3360.
  6. ^ Scheyer, Torsten M.; Romano, Carlo; Jenks, Jim; Bucher, Hugo (19 March 2014). "Early Triassic Marine Biotic Recovery: The Predators' Perspective". PLOS ONE. 9 (3): e88987. Bibcode:2014PLoSO...988987S. doi:10.1371/journal.pone.0088987. PMC 3960099. PMID 24647136.
  7. ^ a b Tapanila, Leif; Pruitt, Jesse (2019-09-04). "Redefining species concepts for the Pennsylvanian scissor tooth shark, Edestus". PLOS ONE. 14 (9): e0220958. Bibcode:2019PLoSO..1420958T. doi:10.1371/journal.pone.0220958. ISSN 1932-6203. PMC 6726245. PMID 31483800.
  8. ^ a b Engelman, Russell K. (2023). "A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira)". Diversity. 15 (3): 318. doi:10.3390/d15030318. ISSN 1424-2818.
  9. ^ a b 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 1932-8494. PMID 30536888.