Vertebrates, Gray, 1821

Hunt, A. P. & Lucas, S. G., 1992, Stratigraphy, paleontology and age of the Fruitland and Kirtland Formations (upper Cretaceous), San Juan Basin, New Mexico, New Mexico Geological Society, New Mexico Geological Society 43 rd Annual Fall Field Conference Guidebook, pp. 217-239 : 225

Vertebrates

Introduction

The vertebrate faunas of the Fruitland and Kirtland Formations rep ­ resent the largest and most diverse Late Cretaceous faunas of the southern Western Interior and have a long history of collection and study ( Hunt et al., 1992). Three vertebrate faunas can be discriminated within the Fruitland and Kirtland Formations; (1) Fruitland Formation ( Table 5); (2) Hunter Wash Member, Farmington Member and De-na-zin members of the Kirtland Formation ( Table 6); and (3) Naashoibito Member of the Kirtland Formation ( Table 7). These faunas form a sequence of decreasing diversity. This is in part due to the fact that the majority of microvertebrate sites are in the Fruitland Formation. Microvertebrate localities account for all the mammalian and amphibian fossils from these strata. It is unfortunate that some recent authors (e. g., Weishampel, 1990) continue to list the fauna of the Kirtland as a whole despite the long realization that two faunas of demonstrably different ages are present in this formation (e. g., Lehman, 1981; Lucas, 1981; Lucas et al .. 1987).

Microvertebrates

Virtually all fish, amphibian and reptiles, apart from turtles and dinosaurs, are represented by disarticulated microvertebrate specimens. The taxonomy of these specimens is, by necessity, largely typological, but they are comparable with contemporaneous faunas in the Western Interior (e.g., Estes, 1964; Sahni, 1972; Bryant, 1989).