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Sauropod Dinosaur Tracks with Skin and Foot-Pad Impressions from the Upper Jurassic Morrison Formation



An interesting article in the last issue of Palaios

BRIAN F. PLATT and STEPHEN T. HASIOTIS. 2006. Newly Discovered Sauropod Dinosaur
Tracks with Skin and Foot-Pad Impressions from the Upper Jurassic Morrison
Formation, Bighorn Basin, Wyoming, U.S.A.  PALAIOS, 21(3), 249-261

A recently discovered dinosaur tracksite from the Upper Jurassic Morrison
Formation, Bighorn Basin, Wyoming, contains abundant sauropod tracks that
exhibit varying degrees of preservation. Most of these tracks appear as
indistinct bulges on the bottoms of sandstone beds, but several are well
preserved and show foot-pad and skin impressions. Three track morphotypes are
recognized: a sauropod pes print, a Brontopodus-like manus print, and a
diplodocid manus print. The Brontopodus-like manus print most likely represents
the footprint of a brachiosaur. This morphotype also contains evidence of
phalangeal nodes?the first reported for a sauropod manus. The diplodocid
manus print is unique because it contains impressions of a substantial ungual
on digit I and a heel pad. A partial sauropod track cast also contains an
impression of interlocking, polygonal scales. This is only the second known
North American sauropod footprint that contains skin impressions.

The spectrum of preservational quality of the tracks and associated trace
fossils is used to infer the relative moisture content of the original
substrate. Moisture content of the original substrate is estimated to have been
moist to borderline saturated. Observations of the tracks at the study areas
also are used to establish a list of features that can be used to distinguish
deep vertebrate tracks from load casts resulting from gravity-induced
soft-sediment deformation.

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Jose Ignacio Ruiz-Omeñaca
Museo del Jurásico de Asturias (MUJA)
E-33328 Colunga, Spain

www.museojurasicoasturias.com
www.aragosaurus.com