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Mammalian Petrosal from Upper Jurassic Morrison Formation of Fruita, Colorado

Ben Creisler

A new paper:

Elijah M. Hughes, John R. Wible, Michelle Spaulding and Zhe-Xi Luo (2015)
Mammalian Petrosal from the Upper Jurassic Morrison Formation of
Fruita, Colorado.
Annals of Carnegie Museum 83(1):1-17
doi: http://dx.doi.org/10.2992/007.083.0101

A partial petrosal from the Upper Jurassic Morrison Formation of the
Fruita Paleontological Area of western Colorado preserving the pars
cochlearis and part of the pars canalicularis is described. The
endocast of the inner ear showing the cochlea, vestibule, lateral
semicircular canal, and the terminal ends of the anterior and
posterior semicircular canals is reconstructed from µCT scans. This
specimen is only the fourth petrosal known from the Morrison
Formation. Mammals known from Fruita include Fruitafossor windsheffeli
Luo and Wible, 2005, the triconodontid Priacodon fruitaensis Rasmussen
and Callison, 1981, the plagiaulacoid multituberculate Glirodon
grandis Engelmann and Callison, 1999, and unnamed spalacotheriids and
dryolestoids. The partial petrosal and its endocast share significant
features with dryolestoids from the Upper Jurassic of Guimarota,
Portugal, including a separate fenestra cochleae and cochlear
canaliculus, and a cochlea that is coiled more than 200°. In light of
these similarities, the Fruita petrosal is assigned to Dryolestoidea.