and Hunt to differentiate R. gregorii and R. bermani, is ignored in the analysis. Paleoecology The Chinle Group, where a large portion of Redondasaurus skulls have been found, is composed of fluvial and lacustrine sediments. Accumulations of fossils in the Chinle Formation can be found in floodplains, bogs, ponds, and fluvial channels. Additional paleontological and sedimentary evidence support the hypothesis that the climate of the Chinle was strongly influenced by high levels of precipitation. Redondasaurus has been collected five times in New Mexico and once in Utah, USA. Specifically, they have been found in the Rock Point Formation (part of Chinle Group), Travesser Formation, and Redonda Formation in New Mexico. The Chinle group is particularly important to paleontologists interested in aetosaurs, as it has been critical in establishing their biochronology in the Late Triassic. Redondasaurus has also been found in the Wingate Sandstone Formation in Utah. The following collections are according to location and date of discovery. New Mexico, USA 1) Upper Travesser Formation - Union County, New Mexico • Age: Norian (221.5 - 205.6 million years ago) • Collected by: D.E. Savage • Date of collection: 1939 • Environment/lithology: "soft purple-maroon shale" 2) Chinle Formation - Rio Arriba County, New Mexico • Age: Rhaetian (205.6 - 201.6 million years ago) • Collected by: E.H. Colbert and J.T. Gregory. • Date of collection: 1947 • Environment/lithology: "bioturbated siltsone" 3) Redonda Formation - Quay County, New Mexico • Age: Norian (221.5 - 205.6 million years ago) • Collected by: P. Murry, A. Hunt, and S. Lucas • Date of collection: 1981, 1986-87 • Environment/lithology: "floodplain", red siltstone 4) Redonda Formation - Quay County, New Mexico • Age: Norian (221.5 - 205.6 million years ago) • Collected by: P. Murry • Date of collection: 1989 • Environment/lithology: "terrestrial", green-grey siltstone and red claystone 5) Redonda Formation - Quay County, New Mexico • Age: Norian (221.5 - 205.6 million years ago) • Collected by: P. Sealey • Date of collection: 2001 • Environment/lithology: "channel lag", conglomerate and bentonitic mudstone Utah, USA 1) Wingate Sandstone Formation - San Juan County, Utah • Age: Rhaetian (205.6 - 201.6 million years ago) • Collected by: not given • Date of collection: not given • Environment/lithology: "fluvial", intraclastic sandstone and conglomerate Redondasaurus is important because it serves as an index species for the Apachean Land Vertebrate Faunachron (LVF). Indeed, it is considered a true index fossil because