Two new macraucheniids (Mammalia: Litopterna) from the late middle Miocene (Laventan South American Land Mammal Age) of Quebrada Honda, Bolivia

<p>We describe two new macraucheniid litopterns from the late middle Miocene (ca. 13 Ma) Quebrada Honda Fauna of southern Bolivia. The holotype of ‘<i>Theosodon</i>’ <i>arozquetai</i>, sp. nov., is a partial cranium preserving RI2–M3 and LP1–M3, elements of the hind limb, and two metapodials. An upper cheek tooth series is also referred to this species. The holotype of <i>Llullataruca shockeyi</i>, gen. et sp. nov., is a mandible preserving nearly the entire lower dentition. A dentary, several upper teeth, and a variety of postcranial elements are also referred to this species. Two specimens from the slightly older locality of Cerdas, Bolivia, are assigned to <i>L.</i> cf. <i>shockeyi</i>. A phylogenetic analysis recovers ‘<i>T.</i>’ <i>arozquetai</i> as sister to <i>Theosodon</i> spp., and we provisionally refer it to that genus pending its revision. <i>Llullataruca shockeyi</i> forms a polytomy with three late Oligocene–early Miocene ‘cramaucheniines’ and the later-diverging macraucheniids. The body mass of ‘<i>T.</i>’ <i>arozquetai</i> is estimated at 80.8–116.2 kg, slightly smaller than early Miocene <i>T. garretorum</i>. <i>Llullataruca shockeyi</i> is among the smallest known macraucheniids based on dental dimensions and is estimated at 35.3–54.6 kg. <i>Theosodon' arozquetai</i> and <i>L. shockeyi</i> are the first well-characterized macraucheniids from the middle Miocene, and the latter species demonstrates that relatively early-diverging lineages persisted at least 7 million years longer in tropical latitudes than they did in Patagonia.</p> <p>http://zoobank.org/urn:lsid:zoobank.org:pub:D26BB67B-D8E1-4D36-9552-4391874CF69C</p> <p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a></p> <p>Citation for this article: McGrath, A. J., F. Anaya, and D. A. Croft. 2018. Two new macraucheniids (Mammalia: Litopterna) from the late middle Miocene (Laventan South American Land Mammal Age) of Quebrada Honda, Bolivia. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1461632.