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We report a new small podocnemidid, Gestemys powelli gen. et sp. nov., based on one nearly complete skull, lower jaw, two shells, and remains of the appendicular skeleton belonging to two specimens from the Eocene Geste Formation of the San Antonio de la Cobres Basin, Salta Province, north-western Argentina. As in other podocnemidid genera, Gestemys exhibits a fully developed and medially extensive cavum pterygoidei, an incisura columellae auris enclosing the stapes and Eustachian tube, and lacks an exoccipital quadrate contact. Gestemys powelli bears a huge foramen palatinum posterius and a short pterygoid flange that does not reach the basisphenoid suture, exposing the cavum pterygoid. Phylogenetic analyses place Gestemys powelli as a member of Podocnemididae more closely related to Erymnochelyinae than Podocnemidinae. In regards to the palaeoenvironmental settings of the Palaeogene formations (Maíz Gordo and Geste) of north-western Argentina, at least two features differentiate the palaeoenvironment where G. powelli was recovered and those of other podocnemidid turtles from the Maíz Gordo Formation: 1) G. powelli was found in situ with very little re-working; and 2) in contrast to the muddy rocks indicating the marginal lacustrine setting and humid climate of the Maíz Gordo Formation, G. powelli is associated with a coarse-grained floodplain setting and a dry, temperate climate. Such differences highlight the contrasting environmental dynamics in which podocnemidid turtles lived during the Palaeogene. [ABSTRACT FROM AUTHOR]

A new basal mesoeucrocodylian, Lorosuchus nodosus gen. et sp. nov., from the Palaeocene of north-western Argentina is presented here. The new taxon is diagnosed by the presence of external nares facing dorsally, completely septated, and retracted posteriorly, elevated narial rim, sagittal crest on the anteromedial margins of both premaxillae, dorsal crests and protuberances on the anterior half of the rostrum, and anterior-most three maxillary teeth with emarginated alveolar margins. This taxon is most parsimoniously interpreted as a bizarre and highly autapomorphic basal member of Sebecidae, a position supported (amongst other characters) by the elongated bar-like pterygoid flanges, a laterally opened notch and fossa in the pterygoids located posterolaterally to the choanal opening (parachoanal fossa), base of postorbital process of jugal directed dorsally, and palatal parts of the premaxillae meeting posteriorly to the incisive foramen. Lorosuchus nodosus also shares with basal neosuchians a suite of derived characters that are interpreted as convergently acquired and possibly related to their semiaquatic lifestyle. The phylogenetic analysis used for testing the phylogenetic affinities of L. nodosus depicts Sebecidae as the sister group of Baurusuchidae, forming a monophyletic Sebecosuchia that is deeply nested within Notosuchia. Alternative phylogenetic placements of Sebecidae, such as the recently proposed affinities with peirosaurids, were also evaluated within the context of the present data matrix and found to be only marginally suboptimal. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S7-S36. [ABSTRACT FROM AUTHOR]