Echinochimaera

Echinochimaera is an extinct genus of fish, it was assigned to the order chimaera by Jack Sepkoski in 2002.[1] The genus' name derives from the Greek εχινό (echino) meaning spiny, and chimaera.

Echinochimaera
Temporal range: Upper Mississippian, 318.1–328.3 Ma
↓
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Chondrichthyes
Subclass:
Holocephali
Order:
Chimaeriformes
Family:
Echinochimaeridae
Genus:
Echinochimaera

Lund, 1977[1]
Species

†Echinochimaera meltoni[2] †Echinochimaera snyderi[2]

Species

The two known Echinochimaera species lived in the Upper Mississippian (Serpukhovian).[3] Fossils of the species were found in the Bear Gulch Limestone in Montana, United States.

Both species have rounded bodies and paddle-like tails as well as large pectoral fins, two dorsal fins and a jaw fused to the braincase.[4] The paddle-like tails indicate that E. meltoni was likely not a predator nor a fast swimmer.[5][6]

Echinochimaera meltoni

E. meltoni was first described by Richard Lund, an Adelphi University palaeontologist,[7] in 1977.[1][3] The fossils found of E. meltoni have shown a great deal of sexual dimorphism, males being found to have a maximum 150mm body length while the maximum body length found in females was only 70mm (juveniles were 13-20mm). In general, the females only grew to about half the size of the males.[5] Males also had four pairs of spikes which may have been used to defend against predators and to identify the fish as male.[6]

There was a relative abundance of immature male fossils found, and that together with the significant sexual dimorphism indicate there was extreme sexual selection among the species.[5]

Echinochimaera snyderi

E. snyderi was described, like E. meltoni, by Richard Lund. It was described in 1988 based on juvenile specimens, all with a body length under 90mm. E. snyderi differs from E. meltoni in fin detail as well as jaw shape and teeth near the front edge of the face rather than a tooth plate, in mature specimens later found its mature size was found to be larger than E. meltoni.[8]

References
  1. "The Paleobiology Database". Retrieved 2009-09-25.
  2. "The Taxonomican: Genus Echinochimaera". Retrieved 2009-09-25.
  3. "University of Montana Paleontology Center". 2007-11-01. Retrieved 2009-09-26.
  4. "Search for Ancient Sharks". Discovery Education. Archived from the original on 2009-12-10. Retrieved 2009-10-11.
  5. Lund, Richard (1990). "Chondrichthyan life history styles as revealed by the 320 million years old Mississippian of Montana". Environmental Biology of Fishes. Springer Netherlands. 27 (1): 1–19. doi:10.1007/BF00004900. ISSN 1573-5133.
  6. "Fossil Fishes of Bear Gulch - Echinochimaera meltoni". 2006-02-01. Archived from the original on 2012-02-12. Retrieved 2015-12-09.
  7. "Bear Gulch - About Richard Lund". 2006-11-16. Archived from the original on 2010-01-08. Retrieved 2009-09-27.
  8. "Fossil Fishes of Bear Gulch - Echinochimaera snyderi". Archived from the original on 2010-07-29. Retrieved 2009-09-26.
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