Browsing by Author "Kool, Lesley."
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Item Chubutemys, a new eucryptodiran turtle from the early Cretaceous of Argentina, and the relationships of the Meiolaniidae ; American Museum novitates, no. 3599(New York, NY : American Museum of Natural History, 2007) Gaffney, Eugene S.; Rich, Thomas H. V.; Rich, Pat Vickers.; Constantine, Andrew Eric, 1965-; Vacca, Raul.; Kool, Lesley.Chubutemys copelloi is the oldest nonmarine cryptodire from South America represented by a skull. The skull and associated postcranial fragments are from the Aptian Cerro CostaŠno Member of the Cerro Barcino Formation of Chubut, Argentina. Chubutemys has a processus trochlearis oticum, showing that it is a cryptodire, and an enclosed canalis caroticus internus extending to the posterior margin of the pterygoid, showing that it is a eucryptodire. The skull of Chubutemys is similar to that of other primitive eucryptodires, particularly Dracochelys, but also to Hangaiemys, Judithemys, Sinemys, and Ordosemys. Chubutemys differs from all these, however, in possessing a solidly roofed skull, formed by long, wide parietals, rather than a posterior emargination. Chubutemys also differs from these taxa in having no cheek emargination. A phylogenetic analysis using PAUP* analyzed 104 parsimony-informative characters resolving into one most parsimonious cladogram of 224 steps, a consistency index of 0.55, and a retention index of 0.74. The phylogenetic analysis weakly joins Chubutemys and meiolaniids on the basis of the prefrontal-postorbital contact. Chubutemys also has a fully roofed skull and slitlike posterior opening of the foramen caroticum laterale (foramen posterius canalis caroticus laterale), features to be expected in a meiolaniid sister taxon. Chubutemys provides further evidence that meiolaniids are related to 'basal' eucryptodires ('sinemydids/macrobaenids'), that is, eucryptodires outside the living Cryptodira, the Polycryptodira. The basicranial morphology of meiolaniids, with an intrapterygoid slit, rather than being a unique feature of the group is instead a modified state of the primitive eucryptodire condition, as seen in such forms as Chubutemys, Dracochelys, Ordosemys, and Sinemys. The intrapterygoid slit of meiolaniids is homologous with the pterygoid flange associated with the foramen caroticum laterale (foramen posterius canalis caroticus laterale of Sukhanov) in non-Polycryptodiran eucryptodires like Ordosemys. Chubutemys shows that nonmarine eucryptodires were present in South America in the Cretaceous, as they were in North America, central Asia, and Australia.Item Otwayemys, a new cryptodiran turtle from the early Cretaceous of Australia. American Museum novitates ; no. 3233(New York, NY : American Museum of Natural History, 1998) Gaffney, Eugene S.; Kool, Lesley.; Brinkman, Donald B.; Rich, Thomas H. V.; Rich, Pat Vickers."The Early Cretaceous Eumeralla Formation, Otway Group, of Cape Otway, Victoria, Australia, has yielded remains of a new genus of eucryptodiran turtle, Otwayemys cunicularius, n. gen., n. sp. Otwayemys is based primarily on shell material, but unassociated skull elements, cervical and caudal vertebrae, and limb elements from the type locality are attributed to this taxon. Otwayemys cunicularius is characterized by a carapace with an emarginate nuchal area, wide vertebral scales, and a smooth shell texture; and by a plastron with wide epiplastra, small extragular scales (scale set 2), gular scales (scale set 1) extending onto entoplastron, a small and narrow entoplastron, a large hyoplastron/hypoplastron fontanelle, and an inguinal buttress terminating on the sixth peripheral. The shell of Otwayemys is most similar to Xinjiangchelys from the Jurassic of China; both have broad epiplastra, plastral buttresses not extending onto costals, a long first thoracic rib, no inclination to the first thoracic centrum, and no mesoplastra; all these characters are primitive for the Eucryptodira. Otwayemys is advanced over Xinjiangchelys in having formed vertebral articulations in the neck. Biconvex eighth and biconcave fifth (?) cervicals in Otwayemys are characters found in the Early Cretaceous Ordosemys of central Asia. Otwayemys differs from Chelycarapookus, also from the Early Cretaceous of Victoria, in being 20% larger and having a large plastral fontanelle, a smooth surface texture, and a wide posterior plastral lobe. Otwayemys belongs in the Centrocryptodira, eucryptodires with formed vertebral articulations. A parsimony analysis of 18 taxa using 40 characters (of which only 20 are known for Otwayemys) produces 12 equally parsimonious trees. A consensus tree shows Otwayemys and Meiolaniidae in an unresolved trichotomy with Polycryptodira (consisting primarily of the living cryptodires) plus Sinemydidae"--P. [1].