Seen here is a model-based reconstruction of life in the ancient ocean during the Mississippian. This is a public exhibit at the Museum of the Rockies in Bozeman, Montana.
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These odd looking fish are Echinochimaera, which are fossil holocephalians known only from estuarine deposits of the Late Mississippian-aged Bear Gulch Lagerstätte in Montana.
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From museum signage:
This spiny chimaera is related to modern chimaeras and ratfish. Antler-like scales and large fins were used to attract females and impress other males.
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Classification: Animalia, Chordata, Vertebrata, Chondrichthyes, Holocephali, Chimaeriformes, Echinochimaeridae
Stratigraphy: Bear Gulch Limestone Member, Heath Formation, Upper Mississippian
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See:
www.flickr.com/photos/jsjgeology/33784748875
and
en.wikipedia.org/wiki/Echinochimaera
