Echinochimaera

Name: Echinochimaera ‭(‬Spiny chimaera‭)‬.
Phonetic: Ek-in-o-ky-me-rah.
Named By: Richard Lund‭ ‬-‭ ‬1977.
Classification: Chordata,‭ ‬Chondrichthyes,‭ ‬Holocephali,‭ ‬Chimaeriformes.
Species: E.‭ ‬meltoni‭ (‬type‭)‬,‭ ‬E.‭ ‬snyderi.
Diet: Uncertain.
Size: E.‭ ‬meltoni males up to‭ ‬15‭ ‬centimetres long,‭ ‬females‭ ‬7‭ ‬centimetres.‭ ‬E.‭ ‬snyderi only known from juveniles at the time of writing,‭ ‬but analysis suggests slightly larger than E.‭ ‬meltoni when fully grown.
Known locations: USA,‭ ‬Montana.
Time period: Serpukhovian of the Carboniferous.
Fossil representation: Numerous individuals including juvenile specimens.

       Though only small,‭ ‬Echinochimaera is still a very interesting fish that is known to have swum in the waters of what is now Montana during the Carboniferous.‭ ‬Echinochimaera had a deep round body that was propelled by a relatively thin tail which ended in a small caudal fin.‭ ‬This indicates that Echinochimaera was not a very fast swimmer,‭ ‬and as such may have cruised along in slower waters.‭ ‬Sexual dimorphism seen in the type species is quite extreme with males of E.‭ ‬meltoni growing to just over double the size of the females.‭ ‬At the time of writing E.‭ ‬snyderi is only known from juveniles,‭ ‬but comparison to similarly aged juveniles of E.‭ ‬meltoni suggest that E.‭ ‬snyderi would have been the larger species when fully grown.
       Strong spines supported the fins,‭ ‬and while these may have provided support for them when brushing past submerged debris,‭ ‬as well as provided some defence against predators,‭ ‬they may have also served a display function.‭ ‬Indeed the males of E.‭ ‬meltoni had a differently shaped dorsal fin to the females,‭ ‬with the main spike being larger and pointing forwards.‭ ‬Males also had four pairs of spines on top of their heads whereas females only had one pair.

Further reading
-‭ ‬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.‭ ‬-‭ ‬Richard Lund‭ ‬-‭ ‬1990.



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