Synopsis of Tucumcari Shale, Mesa Rica Sandstone, and Pajarito Shale paleontology, Cretaceous of east-central New Mexico
— Barry S. Kues, Spencer G. Lucas, Kenneth K. Kietzke, and Niall J. Mateer

Early Cretaceous fossils from east-central New Mexico were among the first to be collected (by members of the 1849 Marcy and 1853 Whipple expeditions) and studied scientifically (Marcou, 1855b, 1858; Hall, 1856) from New Mexico (Kues, 1985a). Despite this early start, and a bitter 40-year controversy arising from Marcou's belief in their Jurassic age (Kues, 1985b), the Early Cretaceous biotas of east-central New Mexico are still incompletely known. Most of the taxa reported from this interval are from the Tucumcari Shale, which is securely placed in the upper Albian on the basis of biostratigraphic correlation with units in Texas and Kansas (Scott, 1970a; Brand and Mattox, 1972; Scott and Taylor, 1977). The overlying Mesa Rica Sandstone and Pajarito Shale are sparsely fossiliferous, and their exact ages have not been established—they may be late Albian and/or early Cenomanian (late Early or early Late Cretaceous) in age.

Since the time when the Early Cretaceous age of the Tucumcari Shale fauna was firmly established (Cummins, 1892; Hill, 1895), few studies of this fauna have been published aside from citations of taxonomic names (e.g., Darton, 1928; Dobrovolny et al., 1946; Brand and Mattox, 1972). However, Stanton (1947) described several molluscs from the Tucumcari, including two new species of gastropods, and Scott (1974) described a number of marine paleocommunities in the Tucumcari Shale and interpreted the paleoecology of the fauna. The macrofauna has not been systematically described, although many of the species that occur in the Tucumcari Shale have been described from equivalent units in Kansas (Scott, 1970b). A profuse microfauna (foraminiferans and ostracodes) is known to be present in the Tucumcari (Brooks, 1959; Kietzke, 1985).

In this paper, we summarize the nature of the Tucumcari, Mesa Rica and Pajarito biotas, illustrate some characteristic invertebrate species and provide an annotated catalog to the taxa reported from these formations. Two of us (BSK, KK) have relocated the site at Pyramid Mountain where, in 1853, Jules Marcou made the first paleontological collections from the unit now called the Tucumcari Shale (Kues, 1985b; Kues and Kietzke, 1985), and illustrations of fossils from this important but long-forgotten locality, including topotypes of Texigryphaea tucumcarii, are included. Most illustrated specimens are reposited in the University of New Mexico Department of Geology paleontology collection
and bear UNM catalog numbers.,