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Marine reptile palaeoecology of Sundance Formation (Jurassic) in Wyoming
From: Ben Creisler
A new online paper:
Judy A. Massare, William R. Wahl, Mike Ross and Melissa V. Connely (2013)
Palaeoecology of the marine reptiles of the Redwater Shale Member of
the Sundance Formation (Jurassic) of central Wyoming, USA.
Geological Magazine (advance online publication)
The Redwater Shale Member (Oxfordian) of the Sundance Formation was
deposited in the foreland basin of the Cordillera during the last and
largest marine transgression of the Jurassic in North America. One
ichthyosaur (Ophthalmosaurus natans), two cryptocleidoid plesiosaurs
(Tatenectes laramiensis, Pantosaurus striatus) and one pliosauromorph
(Megalneusaurus rex) are known from the Redwater Shale Member.
Ichthyosaurs are much more abundant than plesiosaurs, making up almost
60% of the fauna. No actinopterygian fish have been found, although
four species have been identified from the lower Sundance Formation.
At least one hybodont shark and one neoselachian are known from rare
isolated teeth. The main food source for the marine reptiles was
belemnoids, as indicated by preserved gut contents for all four
species. In comparison, the better known and slightly older
Peterborough Member of the Oxford Clay Formation of England, has a
much higher taxonomic and ecological diversity, especially in the
plesiosaurs, marine crocodiles, and fish. The lower diversity in the
Redwater Shale Member probably reflects a much lower primary
productivity in the Sundance Sea, as well as restricted migration from
the open ocean to the north.