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Big Indian Rock phytosaur (Triassic of the United States)

Where: San Juan County, Utah (38.2° N, 109.2° W: paleocoordinates 16.8° N, 48.5° W)

• coordinate stated in text

• small collection-level geographic resolution

When: Wingate Sandstone Formation (Glen Canyon Group), Rhaetian (205.6 - 201.6 Ma)

• Wingate traditionally identified as Early Jurassic in age; however, Lucas et al. (2011: Palaeo3 302: 194-205) have argued that the lower part of the Wingate, including this locality, is latest Triassic in age.

•The phytosaur fossils occur 1.4 m above the base of a 2.1-m-thick interval of trough-crossbedded sandstone and intrabasinal conglomerate that is the basal unit of the Wingate Sandstone. This 2.1-m-thick interval has a sharp, basal, scoured contact where sandstone with rip-ups of siltstone rests on Rock Point siltstone

• bed-level stratigraphic resolution

Environment/lithology: fluvial; intraclastic sandstone and conglomerate

• A 0.2 to O.3-m-thick bed of sandstone and conglomerate contains the phytosaur fossils. Clasts in the conglomerate are grayish red muddy siltstone

•rip-ups and phytosaur bones.

Size class: macrofossils

Preservation: mold/impression

Collection methods: Original skull has mostly weathered away; a rubber peel taken from the surviving natural mold is in the collections of the Museum of Northern Arizona

Primary reference: S. G. Lucas, A. B. Heckert, J. W. Estep and O. J. Anderson. 1997. Stratigraphy of the Upper Triassic Chinle Group, Four Corners Region. New Mexico Geological Society Guidebook 48:81-107 [R. Butler/R. Butler] more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 137230: authorized by Richard Butler, entered by Richard Butler on 12.12.2012

Creative Commons license: CC BY (attribution)