Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), I: faunal composition, biogeographic relationships, and sampling

ABSTRACT

The vertebrate fauna of the Cloverly Formation has been studied for more than 75 years, but remains poorly sampled and incompletely understood. We undertook an extensive survey of the formation that resulted in the discovery of several new, highly productive vertebrate microfossil bonebeds (VMBs). Comprehensive sampling of these and other sites has nearly doubled the known vertebrate diversity of the Cloverly Formation. In addition to the comparatively well-known dinosaurs, this augmented faunal list includes hybodontoid sharks, numerous bony fishes, three lissamphibian lineages, lizards, multiple crocodylians, and several new mammal occurrences. The known Cloverly vertebrate fauna now more closely resembles those of other late Early Cretaceous formations in North America, indicating broad similarities across wide geographic areas at this time. In addition, this work underscores the important role VMBs can play in areas previously studied primarily through surface prospecting and quarrying, especially for assessing paleoecology and species diversity.

ACKNOWLEDGMENTS

We are very grateful for the extensive efforts of S. Jabo and P. Kroehler (Smithsonian Institution) during several years of fieldwork and fossil preparation for this project. R. Lockwood and J. Swaddle provided important guidance to M.P.J.O. during an earlier phase of this project. F. Grady picked most of the fossil materials from the matrix; M. Brett-Surman and M. Florence helped with specimen cataloguing and databasing; S. Whittaker supervised SEM work; M. Fox and C. Norris provided access to the YPM collections. Numerous others provided important assistance, including E. Duneman, C. Gruet, M. Gruet, J. Guibord, R. Hill, A. Massagli, S. McIntyre, J. Mitchell, S. Moran, C. Peredo, and J. Velez-Juarbe as well as M. Coffey, P. Lopez, and R. Horace-Middleton under the collaborative supervision of G. Wesley-Hunt (Montgomery College). We thank C. Manuel, R. Manuel, and E. Kvale for their invaluable advice, support, and hospitality. This work was supported by the Smithsonian Institution through a Walcott Grant and two Small Grants to M.T.C., as well as the NMNH Equipment Fund. Finally, we thank D. Brinkman and S. Sweetman for their detailed, insightful reviews that led to several significant improvements in this paper.

Handling editor: Paul Barrett