MAPPING AND EXCAVATING A MID-CRETACEOUS CROCODILE (ARCHOSAURIA: GONIOPHOLIDAE) AT A LARGE URBAN DIG: THE ARLINGTON ARCHOSAUR SITE, NORTH CENTRAL TEXAS

The Arlington Archosaur Site (AAS) located in Arlington, Tarrant County, TX is a productive fossil site that has produced the remains of a variety of Cretaceous vertebrates. The vertebrate fossils represented range from dinosauria, crocodilian, and chelonian to elasmobranch and dipnoan, with crocodilian and chelonian being most common. The site is located within the Mid–Cretaceous Woodbine Formation (Cenomanian; 95 Mya). The paleoenvironment of the Woodbine at the AAS is a coastal delta plain consisting of fine grained sediments (mudstone), rich with organic material, which overlies a peat bed. During the 2009 summer field season, a large (~7 m) Cretaceous crocodile (goniopholidae) was excavated from the basal peat bed in a hectic one week period. Due to the urban location of the site and its accessibility to the general public, an emergency excavation was organized in an unusual manner using the online social networking site, Facebook. Utilizing the AAS Facebook group, a volunteer field team was assembled within 24 hours to assist in the excavation of the crocodile. The excavation ran for 7 days, up to 24 hours a day, in what is now known as “Crocorama”. The site was mapped using Cartesian coordinates in a 5m x 2.5m grid system. Each fossil was located and drawn in on the grid prior to removal from the field. Each fossil was wrapped and stored for transport with coordinates recorded on the package as well as on the site map content page. As the site expanded, more grids were developed by extending the coordinate system. The grid coordinates were marked with a GPS and later digitized. Within the one week excavation more than 60 vertebrate elements of a large Cretaceous crocodile were recovered from the site as well as several elements of an unidentified chelonian. The crocodilian elements recovered included; osteoderms, vertebrae, a humerus, a radius, phalanges, a dentary, a premaxilla and maxilla, a quadrate and teeth. Currently the only known crocodile from the Woodbine Formation is Woodbinesuchus (Lee, 1997); the AAS “Crocorama” fossils may represent a new species.