Systematics and phylogeny of middle Miocene Cervidae (Mammalia) from Mae Moh Basin (Thailand) and a paleoenvironmental estimate using enamel isotopy of sympatric herbivore species

<div><p>ABSTRACT</p><p>The primitive deer (subfamily Lagomerycinae) <i>Lagomeryx</i> and <i>Stephanocemas</i> are characterized primarily by their palmate antlers. Two lagomerycines, <i>Lagomeryx manai</i>, sp. nov., and <i>Stephanocemas rucha</i>, are described for the first time from Q and K coal layers of the late middle Miocene (13.4–13.2 Ma) Mae Moh Basin in northern Thailand. A species-level phylogeny of the <i>Ligeromeryx</i>-<i>Lagomeryx</i> clade, based on cranial appendages, reconstructs <i>Lagomeryx manai</i>, n. sp., as a derived species of <i>Lagomeryx</i>, sister group of <i>Lagomeryx complicidens</i>. This study suggests that the large species of <i>Lagomeryx</i> are restricted geographically to Asia and dispersed to Southeast Asia at the latest during late middle Miocene, where they are represented by <i>Lagomeryx manai</i>, n. sp. The paleoenvironmental studies of five Mae Moh mammalian taxa, a cervid (<i>Lagomeryx manai</i>, n. sp.), an indeterminate bovid, a suid (<i>Conohyus thailandicus</i>), a rhinoceros (<i>Gaindatherium</i> sp.), and a proboscidean (<i>Stegolophodon</i> sp.), investigated with stable carbon and oxygen isotope analyses of tooth enamel, indicate that the Mae Moh mammals inhabited a wide range of habitats from woodlands to grasslands in a C3-plant-dominated environment. The new species of <i>Lagomeryx</i> seems to have been living in an open environment, contrary to its European relatives. The serial isotopic samples also support that Mae Moh herbivores probably lived in a low-seasonal climate during the late middle Miocene of northern Thailand.</p> <p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="" target="_blank"></a></p> </div>