New Mexico Geological Society Annual Spring Meeting — Abstracts

Fossils of Cretaceous feathers are extremely rare, especially from clastic sediments. Here we report on a partial pennaceous feather collected from the lower Campanian Point Lookout Sandstone of northwestern New Mexico (New Mexico Museum of Natural History locality L7468). The feather is from a laterally discontinuous shale at the top of the Point Lookout Sandstone, a basal marine shoreline facies deposited during the R-4 regressive cycle. The shale contains cylindrical invertebrate burrows including Ophiomorpha, abundant plant fragments of conifers and angiosperms, and a sparse invertebrate fauna including the inarticulate brachiopod Lingula and the pelecypods Caryocorbula and Nucula. The flora and fauna of the shale unit suggest deposition in a quiet pond, probably on a delta-plain mud flat, that was close enough to the shoreline to receive marine water and allow influx of sparse marine invertebrates, but also rendered brackish by fresh-water runoff.

The partial pennaceous feather, University of New Mexico (UNM) 14742, is preserved on a bedding plane as either a carbonized trace or an autolithification. The feather is missing the basal barbs and the base of the rachis and calamus and has a preserved length of 12.6 mm and a maximum width of 6.2 mm. It possesses numerous barbs that are arrayed in symmetrical vanes. About three barbs per millimeter occur on each side of the rachis and the bases of 25 barbs are preserved within each vane. Nine barbules per millimeter were counted along the distal side of one of the barbs on the left vane. The vanes decrease in width toward a rounded tip. Both vanes show gaps that indicate the barbs normally interlocked and so possessed differentiated distal and proximal barbules. Based on this morphology, UNM 14742 is a closed pennaceous feather (Stage IV) and a contour feather and can be referred to Maniraptora, a group that includes true birds and coelurosaur dinosaurs. It probably represents a bird.