Fossil musk turtles (Kinosternidae, <i>Sternotherus</i>) from the late Miocene–early Pliocene (Hemphillian) of Tennessee and Florida

ABSTRACTThe oldest fossil musk turtles, genus <i>Sternotherus</i>, are reported from the Hemphillian of eastern Tennessee and central Florida. <i>Sternotherus palaeodorus</i>, n. sp., is known from five partial shells discovered at the late Miocene–early Pliocene (7–4.5 Ma; late Hemphillian) Gray Fossil Site in Washington County, Tennessee. <i>Sternotherus palaeodorus</i> possesses an enlarged intergular scute, wide first vertebral scute that overlaps peripheral set 1, posteriorly extensive hypoplastron to peripheral 7 contact, and a posteriorly situated inguinal musk duct pore (characteristics more typically seen in <i>Kinosternon</i>). A cladistic analysis recovered <i>S. palaeodorus</i> within crown group <i>Sternotherus</i> in the strict consensus and on the stem of <i>Sternotherus</i> in the majority rule consensus. <i>Sternotherus bonevalleyensis</i>, n. sp., from the Palmetto Fauna (5.5–5 Ma; late Hemphillian) of central Florida was perhaps contemporaneous with <i>S. palaeodorus</i> and is known only from isolated shell fragments. It is morphologically most similar to the <i>Sternotherus minor</i> complex and <i>Sternotherus depressus</i>. Subsequent Blancan fossils from the Suwannee River of Florida represent aff. <i>S. minor peltifer</i>. Additionally, a fragmentary left hyoplastron of cf. <i>Sternotherus</i> from Haile 19A, Alachua County, Florida, could be the oldest record for the genus (ca. 9–8.5 Ma; early Hemphillian). These accounts reveal that <i>Sternotherus</i> was diverse and moderately well distributed geographically by its first known fossil occurrences and support previous hypotheses that the <i>Sternotherus minor</i> complex evolved in the Gulf coastal plain and dispersed throughout that region since at least the latest Miocene–earliest Pliocene. http://zoobank.org/urn:lsid:zoobank.org:pub:A1B8586C-0FCB-4B5E-B0B3-BD2D55B1ADC8SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP