ABSTRACT

Eighteen years of collecting and analysis of over 1,000 of Maryland's Lower Cretaceous (Potomac Group, Patuxent Formation, Aptian Age) reptile and mammal footprints and trackways, along with vertebrate body fossils, invertebrate fossils, and plant fossils, has yielded surprising and important insight about a broad spectrum of life about 110 million years ago. A huge dinosaur-dominated deltaic floodplain in a semi-tropical environment is here shown to have supported a minimum of around thirty dinosaur species coexisting along with a vast array of other fauna, including unexpectedly large mammals, as well anticipated small varieties.

Footprint and body fossil evidences reveal that the area was a nesting ground for a broad range of fauna, including diverse dinosaurs and pterosaurs (known popularly as pterodactyl).

Surprisingly, footprint and feeding trace evidences suggest that among flight-capable fauna, pterosaurs largely outnumbered birds. Along with pterosaur footprints of widely varying size, and suggesting at least three basic footprint shapes, we find the largest imprint (made by a front foot) yet described from anywhere. Feeding traces of pterosaurs of correspondingly huge size further suggest flying reptiles that were possibly at or very near the very upper limit of pterosaur body-weight and wingspan. Those Washington, D.C. metropolitan area discoveries suggest that the pterosaur size-evolution clock should perhaps be reset because it had been thought the largest pterosaurs did not appear until Upper Cretaceous time.

Broader insights, resulting from examination of fossilized plant materials, invertebrate traces, and insect evidences provide an even more comprehensive perspective on Lower Cretaceous life in Maryland.