The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA
The last comprehensive review of the fossil vertebrates from the Miocene of Calvert Cliffs was published more than 100 years ago. This volume is a collection of papers that updates some of the geological features of Calvert Cliffs and provides reviews of the fossil biota that include representatives from the following taxonomic groups: chondrichthyans (chimaeras, shark, skates, and rays), actinopterygians (ray-finned fishes), crocodilians (crocodiles), and sirenians (sea cows). Peter Vogt, Ralph E. Eshelman, and Stephen J. Godfrey document how the 20–40 m [65–130 ft] high Calvert Cliffs along the western shore of the Chesapeake Bay continue to yield insights into 18–8 mya (Miocene) geology, marine and terrestrial vertebrate fauna, and the origin and evolution of Chesapeake Bay and Calvert Cliffs up to the present. These exposures rank high among the best-known fossiliferous deposits of any age. Bretton W. Kent describes the cartilaginous fish (the chondrichthyan) fauna, consisting of 54 species—3 chimaeras (ratfishes), 39 sharks, and 12 skates and rays—a fauna rich in large macrophagous sharks and large neritic rays. In an addendum to Kent’s chapter, he and David J. Ward describe a new species of giant thresher shark with serrated teeth. Giorgio Carnevale and Stephen J. Godfrey present an account of the 38 actinopterygian taxa known from osteological remains and a diverse otolith assemblage of at least 55 taxa. These actinopterygians show an affinity for well-oxygenated muddy and sandy substrates dominated primarily by shallow-water species characteristic of the inner shelf and secondarily by epipelagic taxa. Robert E. Weems details the crocodilians referable to the tomistomine Thecachampsa. The closest living relative is Tomistoma schlegelii, the false gharial of Southeast Asia. Two species are present: Thecachampsa sericodon and T. antiquus. These tomistomines are found in shallow marine coastal deposits, indicating that they inhabited coastal waters. Daryl P. Domning reports that fossils of the Miocene marine fauna include rare sirenians of the family Dugongidae. Three taxa are known: the halitheriine dugongid Metaxytherium crataegense, the dugongine dugongid Nanosiren sp., and another dugongine, aff. Corystosiren. The St. Marys Formation contains remains that may be referable to Metaxytherium floridanum, but confirmation awaits the discovery of more complete specimens.
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