Invertebrate paleontology of the Bursum Formation type section (latest Pennsylvanian), Socorro County, New Mexico
— Barry S. Kues

The type section of the Bursum Formation (traditionally of earliest Permian age but latest Pennsylvanian by a recent proposed relocation of the boundary) in eastern Socorro County, NM, contains a moderately diverse megafauna (33 taxa identifiable at least to generic level) and the "algal biscuit" Ottonosia, all of which are described here. Although some fossils from the Bursum elsewhere in central New Mexico were studied long before the formation name was coined in 1946, this study adds numerous taxa to those previously known from the formation. Marine invertebrate assemblages occur in beds about 7, 49, 67, and 80m above the base of the 85-m-thick Bursum type section, and each assemblage is distinctive in its taxonomic composition. The basal assemblage consists mainly of hematized bivalve shells, chiefly Septimyalina, representing a wave concentrated nearshore assemblage. The next highest assemblage is dominated by moderately diverse brachiopod taxa, especially the large productoid Reticulatia, which lived in a shallow, open-shelf, probably offshore environment. The third assemblage contains the highest number of species, mainly brachiopods and bivalves in approximately equal abundance, and probably lived in shallow, open-shelf but nearer shore environments. The highest assemblage, near the top of the Bursum, contains bivalves and gastropods almost exclusively, with stenohaline groups absent, and may have lived in a lagoon subject to fluctuating salinity. in general, the fauna of the Bursum type section is not greatly different from underlying Virgilian faunas in New Mexico.