THE MONCURE MICROVERTEBRATE FAUNA (UPPER TRIASSIC: NORIAN), COLON CROSS-STRUCTURE/SANFORD SUB-BASIN, NORTH CAROLINA, USA

We report a diverse fish- and tetrapod microvertebrate fauna from Newark Supergroup strata in the Sanford sub-basin obtained with traditional screenwashing techniques supplemented by heavy liquid separation methods. The fossiliferous locality (NCPALEO 1904) is near Moncure, NC at the eastern edge of the Sanford sub-basin near the cross-structure separating it from the Durham sub-basin. The strata exposed at NCPALEO 1904 consist of ~ 33 m of "red-bed" siliciclastics, principally mudstone with thin (<1.5 m thick) lenses of siltstone and sandstone. These strata have been mapped as the Sanford Fm but are proximal fan facies laterally equivalent to more distal Cumnock Fm strata elsewhere in the basin. The fossils occur in a lens of purplish gray, pedogenically modified siltstone, ~19 m above the base of local exposure. The fauna appears time-averaged, and is exceptionally diverse taxonomically, preserving at least a dozen taxa identified at the family level or lower as well as numerous specimens that probably represent other, less-well-known taxa. Fossils of actinopterygian osteichthyans dominate the assemblage, including redfieldiid and semionotid scales as well as skull- and tooth-bearing bone fragments not identifiable to lower taxonomic levels. The first dipnoan (lungfish) teeth from the Newark Supergroup come from this locality and are minute (~3-8 mm long) and tentatively referred to the cf. Arganodus, which is normally at least twice as large in linear dimensions. Amniotes are best represented by teeth, but also include vertebrae and a relatively large number of limb elements. Larger (cm-scale) macrovertebrate fossils are teeth of phytosaurs, rauisuchians, and other archosauriforms. These records include the first teeth of the crurotarsan Revueltosaurus reported from outside Arizona and New Mexico. Smaller microvertebrates include records of several indeterminate reptiles, multiple archosauriforms, a possible sphenodont, and at least two synapsids, including teeth referred to Traversodontidae indet. and, tentatively aff. Microconodon sp. This diversity, coupled with the new records reported here (cf. Arganodus, Revueltosaurus sp.) demonstrates the value of microvertebrate studies generally, and screenwashing in particular, to maximize knowledge of vertebrate paleobiodiversity.