Microvertebrates Paleontology

The Moncure microvertebrate locality in the Cumnock Formation, Sanford sub-basin, North Carolina, dramatically increases the known Late Triassic age vertebrate assemblage from the Deep River Basin. The ,50,000 recovered microvertebrate fossils include osteichthyans, amphibians, and numerous lepidosauromorph, archosauriform, and synapsid amniotes. Actinopterygian fossils consist of thousands of scales, teeth, skull, and lower jaw fragments, principally of redfieldiids and semionotids. Non-tetrapod sarcopterygians include the dipnoan Arganodus sp., the first record of lungfish in the Newark Supergroup. Temnospondyls are comparatively rare but the preserved centra, teeth, and skull fragments probably represent small (juvenile) metoposaurids. Two fragmentary teeth are assigned to the unusual reptile Colognathus obscurus (Case). Poorly preserved but intriguing records include
acrodont and pleurodont jaw fragments tentatively assigned to lepidosaurs. Among the archosauriform teeth is a taxon distinct from R. callenderi that we assign to Revueltosaurus olseni new combination, a morphotype best assigned to cf. Galtonia, the first Newark Supergroup record of Crosbysaurus sp., and several other archosauriform tooth morphotypes, as well as grooved teeth assigned to the recently named species Uatchitodon schneideri. Synapsids represented by molariform teeth include both ‘‘traversodontids’’ assigned to aff. Boreogomphodon and the ‘‘dromatheriid’’ Microconodon. These records are biogeographically important, with many new records for the Cumnock Formation and/or the Newark Supergroup. In particular, Colognathus, Crosbysaurus, and Uatchitodon are known from basins of Adamanian age in the southwestern U.S.A. These new records include microvertebrate
taxa more typical of non-Newark basins (abundant archosauriforms, temnospondyls, lungfish) as well as more
typical Newark osteichthyans and synapsid-rich faunal elements.

The Paleogene Order Taeniodonta Cope, 1876—peculiar heavy-bodied mammals, some with ever-growing cheek teeth—are grouped with the Late Cretaceous eutherian CimolestesMarsh, 1889, along with a host of other taxa in a superordinal group, the Cimolesta. Taeniodonts were thought to have arisen from Cimolestes indirectly, through Paleocene ProcerberusSloan and Van Valen, 1965. The recently described Paleocene AlveugenaEberle, 1999, until now known only from the upper dentition, has been put forth as a transitional form between cimolestids and taeniodonts on phylogenetic and biostratigraphic grounds. An older taeniodont, the Late Cretaceous SchowalteriaFox and Naylor, 2003, has since been described, complicating taeniodont origins. We describe here a lower jaw that we refer to Alveugena from the lower part of the Ludlow Member of the Fort Union Formation in North Dakota. The lower jaw comes from strata of early Early Paleocene age (Puercan 1 North American Land Mammal Age) 8.5 m above a Cretaceous-Paleogene boundary, identified using palynological criteria. A cladistic analysis is here presented using new data on Schowalteria and Alveugena, added to that of Cimolestes, Procerberus formicarumSloan and Van Valen, 1965, P. grandisMiddleton and Dewar, 2004, and Onychodectes. This analysis revealed Alveugena as the sister taxon of the taeniodonts but with a closer relationship to Cimolestes than Procerberus, suggesting that taeniodonts evolved from a Cimolestes-like ancestor. We discuss the age relations of early taeniodonts and related taxa and propose a scenario of ancestor-descendent relations that minimizes, but does not eliminate, implied stratigraphic gaps.

The Rhaetian (latest Triassic) is best known for its basal bone bed, but there are numerous other bone- rich horizons in the succession. Boreholes taken around the M4–M5 motorway junction in SW England provide measured sections with multiple Rhaetian bone beds. The microvertebrate samples in the various bone beds differ through time in their composition and in average specimen size. The onset of the Rhaetian transgression accumulated organic debris to form a fossiliferous layer high in biodiversity at the base of the Westbury Formation. The bone bed at the top of the Westbury Formation represents a community with lower biodiversity. The bone beds differ in their faunas: chondrichthyan teeth are dominant in the basal bone bed, but actinopterygians dominate the higher bone bed. These differences
could be taphonomic, but are more likely evidence for ecological-evolutionary changes. Further, a change from larger to smaller specimen sizes up-sequence allows rejection of an earlier idea that the
successive bone beds represented multiple reworkings of older bone beds.

We document here a new taxon of sphenodontian, Whitakersaurus bermani gen. et sp. nov., that is also the most complete sphenodontian fossil from the Upper Triassic Chinle Group in the south-western USA and the first Chinle sphenodontian represented by more than a single fragmentary dentulous element. The holotype was recovered during preparation of block C-8-82 from the famous Coelophysis (Whitaker) quarry at Ghost Ranch, New Mexico, and is the most complete small vertebrate recovered from the quarry. Detailed lithostratigraphy and geologic mapping demonstrate that the Whitaker quarry is in the Rock Point Formation of the Chinle Group, so Whitakersaurus is the first sphenodontian reported from this unit. Records of the phytosaur Redondasaurus at the quarry and elsewhere in the Chinle Group demonstrate that the quarry, and thus Whitakersaurus, is of Apachean (late Norian-Rhaetian) age. The sphenodontian specimen consists of incomplete left and right dentaries, a partial left? maxilla?, and impressions of a probable palatal element, all of which preserve multiple teeth. Whitakersaurus is distinct from other sphenodontians in possessing a unique combination of the following features: marginal dentition pleurodont anteriorly and posteriorly acrodont; pronounced heterodonty in dentary, with as many as 15 smaller, peglike teeth anteriorly and several larger, posterior teeth that are conical and striated; faint radial ornamentation of posterior tooth crowns; presence of c. 19 dentary teeth; and absence of a distinct flange on posterior teeth. Numerous other details distinguish it from both more primitive and more derived taxa. Whitakersaurus, therefore, helps to document further mosaic evolution and an extensive diversification event of sphenodontians during Triassic time. Although sphenodontian taxa are relatively easily recognized, widely distributed, and common small-or microvertebrate fossils, the long stratigraphic ranges of taxa known from multiple specimens hinders their utility as index fossils with which to correlate strata across Pangaea.

Se denuncia a Ulyses Pardiñas como perpetrador de varios tipos de fraudes científicos realizados en su tesis doctoral y en varios artículos respecto de la fauna, estratigrafía y cronología de Cueva Tixi. En este artículo se describen las pruebas de esos fraudes.

The Neotropical frog genus Leptodactylus is one of the most taxonomically diverse of all neobatrachian anurans. Despite the genus being highly diversified and widely distributed today, the fossil record is scanty and restricted to the Quaternary of the Neotropics. Here, we report and describe a new record of total group Leptodactylus from the Chapadmalalan (early Pliocene) of the South American Pampas. We evaluate both qualitative and quantitative characters and discuss the taxonomic value of body size in the context of living Leptodactylus. A number of features of the fossil elements suggests an affinity with the living species of the L. latrans species group and, particularly, with L. latrans. However, the lack of resolution of Leptodactylus interrelationships and, thus, the lack of osteological synapomorphies of the species groups and species within the genus conspire to force allocation of the fossils to crown Leptodactylus until they are studied in a rigorous phylogenetic context. In any case, the new material constitutes the oldest record of total group Leptodactylus and extends their stratigraphic range back to the early Pliocene.

We document here a new taxon of sphenodontian, Whitakersaurus bermani gen. et sp. nov., that is also the most complete sphenodontian fossil from the Upper Triassic Chinle Group in the south-western USA and the first Chinle sphenodontian represented by more than a single fragmentary dentulous element. The holotype was recovered during preparation of block C-8-82 from the famous Coelophysis (Whitaker) quarry at Ghost Ranch, New Mexico, and is the most complete small vertebrate recovered from the quarry. Detailed lithostratigraphy and geo- logic mapping demonstrate that the Whitaker quarry is in the Rock Point Formation of the Chinle Group, so Whitakersaurus is the first sphenodontian reported from this unit. Records of the phytosaur Redondasaurus at the quarry and elsewhere in the Chinle Group demonstrate that the quarry, and thus Whitakersaurus, is of Apachean (late Norian–Rhaetian) age. The sphenodontian specimen consists of incomplete left and right dentaries, a partial left? maxilla?, and impressions of a probable palatal element, all of which preserve multiple teeth. Whitakersaurus is distinct from other sphenodontians in possessing a unique combination of the following features: marginal dentition pleurodont anteriorly and posteriorly acrodont; pronounced heterodonty in dentary, with as many as 15 smaller, peg- like teeth anteriorly and several larger, posterior teeth that are conical and striated; faint radial ornamentation of posterior tooth crowns; presence of c. 19 dentary teeth; and absence of a distinct flange on posterior teeth. Numerous other details distinguish it from both more primitive and more derived taxa. Whitakersaurus, therefore, helps to document further mosaic evolution and an extensive diversification event of sphenodontians during Triassic time. Although sphenodontian taxa are relatively easily recognized, widely distributed, and common small- or microvertebrate fossils, the long stratigraphic ranges of taxa known from multiple specimens hinders their utility as index fossils with which to correlate strata across Pangaea.

Key words: Upper Triassic, Sphenodontia, Chinle Group, New Mexico, Ghost Ranch.