New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico Museum of Natural History (NMMNH) locality 1336 ( SE1/4, NW1/4, NW1/4, sec. 24, T13N, R1W, Sandoval County) near San Felipe Mesa ("Sky Village") produces a prolific assemblage of fossil selachians and reptiles. This locality was discovered by J. Lindsay and is in a 0.3-m-thick, trough crossbedded sandstone that is grayish orange to pale yellowish orange, very find to coarse grained, subangular to subrounded, quartzose and calcite cemented with abundant inoceramid shell fragments. This bed is in a thick sequence of, calcareous shaIe of the upper part of the Mulatto Tongue of the Mancos Shale and thus is of early Santonian age. We interpret this locality to be an offshore bar. The vertebrate assemblage includes teeth of Ptychodus mortoni, Scapanorhynchus raphiodon, Squalicorax sp., cf. Cretoxyrhina sp. and a rhinobatoid plus indeterminate plesiosaur teeth and turtle bone fragments. This fauna differs markedly from contemporaneous marine vertebrate assemblages found in shoreline sandstones in being less diverse and by being dominated by Ptychodus and plesiosaur teeth. We believe these differences are due primarily to environmental factors but cannot rule out possible taphonomic factors influencing faunal composition as well.