<i>Wabanbara ringtailensis</i>—a new chelid turtle (Pleurodira: Chelidae) from mid-Miocene deposits of the Riversleigh World Heritage Area in Australia

The mid-Miocene Ringtail Site of the Riversleigh World Heritage Area in Waanyi country, northwestern Queensland, Australia is a particularly productive locality for chelid turtle fossils. Recently, an almost complete chelid skull was recovered from Ringtail Site. This skull is large and shows a combination of features not found in Australian short-necked chelids: an elongate basisphenoid; large orbits; narrow triturating surface; prominent lateral and posterior emarginations; posteriorly tilted <i>cavum tympani</i>; posteriorly extended squamosal; shallow palate; and a long, broad and ventrally flattened trochlear process. The Ringtail Site skull also differs from Australian long-necked chelids in lacking contact between the quadrate and basisphenoid, possessing unfused frontals, a moderately high temporal arch, and a flattened skull. Aspects of skull morphology suggest that the Ringtail Site chelid was an aquatic omnivore that actively searched for food in open water, and may have employed gape-suction feeding. We designate the Ringtail Site chelid as a new genus and species, and phylogenetically distinct from all modern Australian chelid genera as an early diverging member of the radiation. The Ringtail Site chelid could be closely related to the Australian Miocene taxon <i>Birlimarr gaffneyi—</i>the only other extinct Australian chelid species described from relatively complete skull material. <i>Arthur White [[e-mail]], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW, Australia, 2052; Anna Gillespie* [[e-mail]], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW, Australia, 2052; Suzanne Hand [[e-mail]], Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, NSW, Australia, 2052.</i>澳大利亚昆士兰州西北部瓦尼族（Waanyi）领地内的里弗斯利（Riversleigh）世界遗产地的中中新世环尾遗址（Ringtail Site），是澳龟科（Chelidae）龟类化石的高产位点。近期，科研人员从环尾遗址出土了一具近乎完整的澳龟科头骨。该头骨体型硕大，兼具一系列澳大利亚短颈澳龟类所不具备的特征：延长的基蝶骨（basisphenoid）、宽大的眼眶（orbits）、狭窄的咀嚼面（triturating surface）、显著的侧缘与后缘切迹、向后倾斜的鼓室腔（cavum tympani）、向后延伸的鳞状骨（squamosal）、较浅的腭部（palate），以及修长、宽阔且腹侧扁平的滑车突（trochlear process）。 该环尾遗址头骨还与澳大利亚长颈澳龟类存在差异：其方骨（quadrate）与基蝶骨无接触，额骨（frontals）未愈合，颞弓（temporal arch）高度中等，头骨整体扁平。头骨形态的多项特征表明，这只环尾遗址澳龟为水生杂食性动物，会在开阔水域主动搜寻食物，或可采用张口抽吸的摄食策略。 我们将该环尾遗址澳龟定为一新属新种，其系统发育位置独立于所有现生澳大利亚澳龟属类群，属于澳龟类辐射演化的早期分支成员。该环尾遗址澳龟可能与澳大利亚中新世类群*Birlimarr gaffneyi*亲缘关系较近——后者是目前仅有的另一种以相对完整头骨材料记述的已灭绝澳大利亚澳龟物种。 Arthur White [[e-mail]]，澳大利亚新南威尔士大学生物、地球与环境科学学院地球与可持续发展科学研究中心，新南威尔士州，澳大利亚，2052；Anna Gillespie* [[e-mail]]，同上；Suzanne Hand [[e-mail]]，澳大利亚新南威尔士大学生物、地球与环境科学学院地球与可持续发展科学研究中心，新南威尔士州，澳大利亚，2052。