Parahelicoprion Explained

Parahelicoprion is an extinct genus of shark-like eugeneodontid holocephalids from the Permian of the Ural Mountains (Russia) and Copacabana Formation, Bolivia.[1] The genus name, from "nearly coiled saw" in Greek, directly refers to Helicoprion, a related holocephalid that shares similar traits to it, including the helical whorl of teeth.

The holotype of Parahelicoprion is based on a poorly preserved material,[1] so its size estimates along with those of some other large eugeneodonts are highly subjective due to their fragmentary fossil remains that cannot provide an empirical basis.[2] While Karpinsky separated the type species from the genus Helicoprion,[3] it has been recently suggested that this genus does represent a junior synonym of Helicoprion.[4]

Description

One of the primary qualities that separate Parahelicoprion from Helicoprion is the shape, thickness, and angle of the tooth whorl. Its teeth protrude outwards not like a tightly coiled saw, but instead a curved arrangement of cutting blades indicating it relied less on crushing slow-moving invertebrates and catching cephalopods, or other small mollusk prey, but inflicting traumatic damage against more durable, faster prey.[5] Their teeth grew at a much slower pace than those of other whorl-tooth sharks, resulting in a depreciated spiral, growing only half of the teeth a Helicoprion would grow in its lifetime. The tooth spiral also was able to indicate the age of the eugeneodontidans in question.[6]

Paleobiology

Parahelicoprion is thought to have been a nektonic carnivore that probably preyed upon a variety of different species, using its blade-like teeth to cut at exposed flesh like a hatchet or wedge.[7]

Notes and References

  1. Chondrichthyan and actinopterygian remains from theLower Permian Copacabana Formation of Bolivia . Merino-Rodo, Dagmar. Geobios . 1986 . 19 . 4 . 479–493 . 10.1016/S0016-6995(86)80005-5. 1986Geobi..19..479M. etal.
  2. Maisey . John G. . Bronson . Allison W. . Williams . Robert R. . McKinzie . Mark . 2017-05-04 . A Pennsylvanian 'supershark' from Texas . Journal of Vertebrate Paleontology . en . 37 . 3 . e1325369 . 10.1080/02724634.2017.1325369 . 2017JVPal..37E5369M . 134127771 . 0272-4634.
  3. Karpinsky. A.P.. 1924. Helicoprion (Parahelicoprion n.g.) clerci. Zapiski Ural'skogo Obshchestva Estestvoispytatelei. 34. 1–10.
  4. Naugolnykh. S.V.. 2018. Artinskian (Early Permian) Sea Basin and Its Biota (Krasnoufimsk, Cis-Urals). Stratigraphy and Geological Correlation. 26. 7 . 734–754. 10.1134/S0869593818070080. 2018SGC....26..734N . 135304766 .
  5. http://dinonews.net/forum/paleoactus.php?msg=168926 Parahelicoprion and Agassizodontidea
  6. Brad Matsen and Ray Troll (October 25, 2012). "Planet Ocean: A Story of Life, the Sea, and Dancing to the Fossil Record".
  7. Web site: Fossilworks: Parahelicoprion.