Temporal range: Upper Mississippian, 318.1–328.3 Ma
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. The paddle-like tails indicate that E. meltoni was likely not a predator nor a fast swimmer.
E. meltoni was first described by Richard Lund, an Adelphi University palaeontologist, in 1977. 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. Males also had four pairs of spikes which may have been used to defend against predators and to identify the fish as male.
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.
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- 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. Retrieved 26-09-09. Check date values in:
- "Fossil Fishes of Bear Gulch - Echinochimaera meltoni". 2006-02-01. Archived from the original on 2012-02-12. Retrieved 2015-12-09.
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- "Fossil Fishes of Bear Gulch - Echinochimaera snyderi". Retrieved 2009-09-26.