Agustín Scanferla

A New Snake Skull from the Paleocene of Bolivia Sheds Light on the Evolution of Macrostomatans

Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

Ancient DNA from the extinct South American giant glyptodont Doedicurus sp. (Xenarthra: Glyptodontidae) reveals that glyptodonts evolved from Eocene armadillos

Glyptodonts were giant (some of them up to ~2400 kg), heavily armoured relatives of living armadillos, which became extinct during the Late Pleistocene/early Holocene alongside much of the South American megafauna. Although glyptodonts were an important component of Cenozoic South American faunas, their early evolution and phylogenetic affinities within the order Cingulata (armoured New World placental mammals) remain controversial. In this study, we used hybridization enrichment and high‐throughput sequencing to obtain a partial mitochondrial genome from Doedicurus sp., the largest (1.5 m tall, and 4 m long) and one of the last surviving glyptodonts. Our molecular phylogenetic analyses revealed that glyptodonts fall within the diversity of living armadillos. Reanalysis of morphological data using a molecular ‘backbone constraint’ revealed several morphological characters that supported a close relationship between glyptodonts and the tiny extant fairy armadillos (Chlamyphorinae). This is surprising as these taxa are among the most derived cingulates: glyptodonts were generally large‐bodied and heavily armoured, while the fairy armadillos are tiny (~9–17 cm) and adapted for burrowing. Calibration of our phylogeny with the first appearance of glyptodonts in the Eocene resulted in a more precise timeline for xenarthran evolution. The osteological novelties of glyptodonts and their specialization for grazing appear to have evolved rapidly during the Late Eocene to Early Miocene, coincident with global temperature decreases and a shift from wet closed forest towards drier open woodland and grassland across much of South America. This environmental change may have driven the evolution of glyptodonts, culminating in the bizarre giant forms of the Pleistocene.

NUEVOS APORTES AL CONOCIMIENTO DE LA HERPETOFAUNA DE LA FORMACIÓN CERRO AZUL (MIOCENO SUPERIOR), PROVINCIA DE LA PAMPA, ARGENTINA

Se describen nuevos materiales fosiles de anfibios y reptiles hallados en sedimentos referidos a la Formacion Cerro Azul (Mioceno Superior), procedentes de numerosas localidades de la provincia de La Pampa, Argentina. Los nuevos registros se basan en un resto craneano de anuro asignado al generoCeratophrys, restos de caparazon de tortugas terrestres del generoChelonoidis, vertebras asignables al lagarto de la familia TeiidaeTupinambis, y una vertebra troncal de serpiente comparable al genero de colubroideos actualesPhilodryas. Tanto los registros terciarios previos de generos actuales de anfibios y reptiles en America del Sur, como asi tambien la asociacion recuperada en el Mioceno Superior de La Pampa sugieren que la mayoria de los generos que componen la herpetofauna Neotropical estaban presentes en el Mioceno, patron similar al observado en otras regiones del mundo.

Cranial anatomy of an Eocene notoungulate mammal from northwestern Argentina with special reference on the ear region

Abstract A detailed anatomical analysis is here presented focused on a notoungulate skull recovered from sediments of the lower part of the Quebrada de los Colorados Formation (LC I; late middle Eocene), cropping out in Salta Province, Argentina. The material was identified as a Toxodontia, although it does not exhibit information useful enough for its generic or even familiar assignment. The description was mainly focused on the basicranium and the auditory region (especially the petrosal and auditory ossicles) given the better preservation of these parts in the specimen. Additionally, a phylogenetic analysis was conducted based on previous studies dealing with a wide sample of South American Native Ungulates. This specimen exhibits some traits traditionally mentioned for the suborder Toxodontia, such as the horizontal bullar septum, and others recently regarded as synapomorphies of Notoungulata, including the lateral location of the tensor tympani fossa and the expanded medial margin of the petrosal. However, it also shows some unexpected features for that suborder of notoungulates, such as the presence of a strongly curved promontorium. The study of this skull increases our knowledge of the auditory anatomy of Eocene Toxodontia and yields a good opportunity to test current phylogenetic hypothesis, mostly based on Neogene representatives.

A vertebrate assemblage of Las Curtiembres Formation (Upper Cretaceous) of northwestern Argentina

We describe an association of fossil vertebrates from the Morales Member of the Las Curtiembres Formation (Campanian) near Puente Morales, Salta Province, NW Argentina. The fossils include teleostean fishes, pipid frogs, pleurodiran turtles, mesoeucrocodylians, non-avian theropod dinosaurs, and enantiornithine birds. The vertebrate record is dominated by freshwater taxa. With the exception of pipid frogs, all taxa here de- scribed constitute new records for this sedimentary unit. Among them, the turtles are reported for the first time in the Cretaceous of northwestern Argentina (Salta Group). Additionally, the recently published small enantiorni- thine Intiornis inexpectatus enlarges the diversity of cretaceous birds from South America. Despite the fragmen- tary nature of the specimens, the information provided by this Late Cretaceous assemblage sheds new light on the composition of the continental vertebrate fauna in a paleontologically poorly known region of South America.

A new Andinichthyidae catfish (Ostariophysi, Siluriformes) from the Paleogene of northwestern Argentina

ABSTRACT The clade Andinichthyidae includes three poorly known genera of extinct catfishes from Upper Cretaceous-Paleogene beds of Bolivia. These taxa are of uncertain phylogenetic position, and their anatomy is far from being well known. The aim of the present contribution is to describe a new genus and species of andinichthyid catfish. The new taxon is represented by several cranial and postcranial bones collected in Eocene beds from northwestern Argentina. The new taxon constitutes the first nominate andinichthyid outside Bolivia, as well as the youngest record for the family. On the basis of the new specimens, the phylogenetic position and paleobiogeography of andinictyids is briefly discussed.