The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA – Volume 3: Elephants, Land Mammals, and Seals

<jats:p>&lt;p dir="ltr"&gt;In this third volume in the series on the Miocene vertebrate fauna from Calvert Cliffs, Maryland, USA, the three chapters detail the historical record and taxonomy of Miocene elephants, all other known land mammals, and seals. Chapter 1 examines the remains of Miocene elephants (Gomphotheriidae). The earliest record of a gomphothere from the Chesapeake Group was a molar collected near Governor Run, Calvert County. Other gomphothere molars scattered throughout the area extend up through the Miocene Choptank, St. Marys, and Eastover Formations. There are at least four taxa (probably five) of Gomphotheriidae from the Chesapeake Group: &lt;i&gt;Gomphotherium calvertense&lt;/i&gt;; a new genus and species from the Choptank Formation; aff. &lt;i&gt;Stenobelodon floridanus&lt;/i&gt;; an unidentified Gomphotheriidae; and, tentatively, &lt;i&gt;Rhynchotherium&lt;/i&gt;. Chapter 2 reviews the hundreds of fossils of terrestrial mammals collected from the Mid-Atlantic Coastal Plain deposits of the Chesapeake Group. Most of these isolated remains originated from marine deposits of the Calvert and St. Marys Formations. The fauna represents a diverse and, in some instances, unusual assemblage ranging from the late early Miocene through to the early Pliocene. It illustrates a shift in terrestrial faunas from an open marine shelf environment bordered by a drier prairie and patchy forest to a more closed coastal marine and estuarine environment bordered by a humid and forested environment. Chapter 3 provides a review of the earless seals (Phocidae). Five extinct phocids have been recognized based on differences in their limb bones: the monachines &lt;i&gt;Magnotherium johnsii&lt;/i&gt;, &lt;i&gt;Terranectes magnus&lt;/i&gt;, and &lt;i&gt;Terranectes parvus&lt;/i&gt; and the phocines &lt;i&gt;Leptophoca amphiatlantica&lt;/i&gt; and &lt;i&gt;Leptophoca lenis &lt;/i&gt;(later grouped into &lt;i&gt;Leptophoca proxima&lt;/i&gt;). Unfortunately, long bones are not a sufficient basis on which to name new taxa, and consequently, recent research on variation in appendicular bones of Phocidae resulted in the validity of &lt;i&gt;M. johnsii&lt;/i&gt; and both &lt;i&gt;Terranectes&lt;/i&gt; species being questioned. However, one unnamed species of Monachinae is recognized from the Miocene of the Chesapeake Group. &lt;i&gt;Leptophoca proxima&lt;/i&gt; includes two distinct morphotypes of humeri, warranting separating &lt;i&gt;L. lenis&lt;/i&gt; from specimens of &lt;i&gt;L. proxima&lt;/i&gt;. Accordingly, at least two phocine species are present in the Miocene strata of the Chesapeake Group, with a total of three morphotypes of Phocidae.&lt;/p&gt;</jats:p>