Phylogenetic position of Sinotamias and the early evolution of Marmotini (Rodentia, Sciuridae, Xerinae)

Abstract

ABSTRACTReexamination of Sciurotamias gromovi from the upper Miocene of Ukraine stimulated revision of Sinotamias, a problematic Neogene sciurid of uncertain affinities and previously documented only from the middle–upper Miocene of Asia. A reanalysis of the Ukrainian material and other morphologically similar taxa shows Sinotamias to be a member of the xerine tribe Marmotini. Sciurotamias gromovi and Tamias atsali are shown to be members of Sinotamias. Tamias anatoliensis from the upper Miocene of Turkey is a junior subjective synonym of Sinotamias primitivus. Sinotamias minutus and Sinotamias maximus are excluded from the genus. The latter species is referred to Kherem. Prospermophilus is synonymized with Sinotamias. Phylogenetic analysis of 23 xerine genera using 66 craniodental characters places Sinotamias among the basal Marmotina as a sister group to the living members of the subtribe. The species of the genus are united by obliquely striated lower incisors, posteriorly expanded metaconules of M1–2, and posteriorly tapered ectolophid of m1–2. The late Oligocene–early Miocene Asian genus Plesiosciurus, previously classified in the sciurid subfamily Sciurinae, is instead a member of the Marmotini and is recovered as the sister taxon to Miospermophilus and Sinotamias. The genera Ammospermophilus, Cynomys, Marmota, Miospermophilus, Paenemarmota, Plesiosciurus, Sinotamias, and Spermophilus s.l. form a monophyletic subtribe Marmotina, supported by the absence of the mesoconid in m1–3. Miospermophilus is identified as the basal-most member of this group of genera, suggesting a Nearctic origin for the Marmotina. Sinotamias, considered to be a descendant of Plesiosciurus, appears to have originated in Asia and entered Europe around 8.5 Ma.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Sinitsa, M. V. 2018. Phylogenetic position of Sinotamias and the early evolution of Marmotini (Rodentia, Sciuridae, Xerinae). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1419251.