Adriana M. Albino

EXCEPTIONALLY PRESERVED SKELETONS OF THE CRETACEOUS SNAKE DINILYSIA PATAGONICA WOODWARD, 1901

For over one hundred years the Upper Cretaceous snake Dinilysia patagonica has been known from only the holotype skull and associated vertebrae (Smith-Woodward, 1901; Estes et al., 1970; Frazetta, 1970; Hecht, 1982; Rage and Albino, 1989; Albino, 1996). Recent fieldwork near Neuquen, Argentina, has produced a large number of exceptionally well-preserved skulls and skeletons of Dinilysia that preserve osteological features missing in the holotype. This new information is timely as recent studies of snake phylogeny have relied upon incomplete descriptions of Dinilysia (Caldwell, 1999; Scanlon and Lee, 2000; Tchernov et al., 2000). Our study of the new fossils indicates that Dinilysia was a large-bodied snake with an aniliid/ xenopeltid-like middle-ear osteology, and an anguimorph-like hypapophyseal/intercentrum anatomy. These new data will certainly impact future studies of snake phylogeny. We provide the first diagnosis of Dinilysia patagonica Smith-Woodward, 1901, along with a preliminary description of the new material, followed by discussion of two important osteological features (i.e., postorbital vs. jugal, absence of a crista circumfenestralis). The holotype and all new specimens of Dinilysia described here were found at three localities in or near Neuquén, Neuquén Province, Argentina. The fossil-producing units are redto white-weathering, coarse-grained sandstones assigned to the Bajo de la Carpa Member, Rio Colorado Formation (?Coniacian, Upper Cretaceous; Caldwell and Albino, 2001). The holotype specimen (Smith-Woodward, 1901; Estes et al., 1970) and two fragmentary skulls were found at Boca del Sapo, just north of Neuquén. Another fragmentary skull, assigned here to Dinilysia, was collected in the 1980s from outcrops just north of the Universidad Nacional del Comahue in Neuquén. The most recent collection of excellent skulls and articulated postcranial skeletons is from outcrops of the Rı́o Colorado Formation exposed at the ‘‘Tripailao Farm Locality.’’ These sections are located on the south side of the Rio Negro approximately 8.5 km to the west of the bridge at Paso Córdoba, or approximately 23 km to the southeast of Neuquén on the south side of the river (Caldwell and Albino, 2001). Institutional Abbreviations MACN, Museo Argentino de Ciencias Naturales ‘‘Bernardino Rivadavia,’’ Buenos Aires, Argentina; MLP, Museo de La Plata, La Plata, Argentina; MPCA-PV, Museo de la Ciudad de Cipoletti, Cipoletti, Rı́o Negro Province, Argentina; MUCP, Museo de Geologı́a y Paleontologı́a, Universidad Nacional del Comahue, Neuquén, Argentina. SYSTEMATIC PALEONTOLOGY

Tooth socket histology in the Cretaceous snake Dinilysia, with a review of amniote dental attachment tissues

Abstract The dental attachment site histology and gross morphology of Dinilysia patagonica, a Cretaceous terrestrial snake, is examined in a thin section through the tissue-filled mesial-distal region between tooth positions of a left maxilla, and other partial tooth-bearing bones with teeth. We observed compact zonal bone and cancellous bone forming the maxilla, and alveolar bone (a woven-fibered bone) lining the tooth socket and filling the region between tooth positions. The discovery of alveolar bone in D. patagonica is significant because alveolar bone was found previously in only one other group of squamates, mosasaurs (extinct large marine lizards), and other amniotes with a thecodont tooth-attachment anatomy (archosaurs, mammals). The presence of alveolar bone in D. patagonica, associated with the recent finding of alveolar bone and other tissues associated with thecodonty (alveolar bone, cement, periodontal ligament) in mosasaurs, suggest that these tissues might be broadly distributed among squamates. Dinilysia patagonica is inferred to have a hinged tooth-attachment type, based on the tooth socket morphology and relationship between preserved teeth and the tooth-bearing bone.

Snakes from the Paleocene and Eocene of Patagonia (Argentina): Paleoecology and coevolution with mammals

Snakes from the Paleocene (? Madtsoia sp.) and Eocene (? Madtsoia sp., ? Boa sp., Chubutophis grandis gen. et sp. nov., Boinae indet.) of Patagonia, Argentina, are reviewed. The Late Cretaceous and Early Tertiary records are analysed and compared. The conclusions are: (1) The Dinilysiidae do not reach the Tertiary. (2) The Boidae seem to have had a basic diversification in Gondwana during the Cretaceous. (3) The snakes from the Late Paleocene were larger than those of the Late Cretaceous, probably due to the more varied and abundant mammals of larger size providing their most frequent prey. (4) During the Early Eocene a greater ecological diversity of snake faunas is present. It probably represents the existence of environmental “patches”; or “pulses”; in subtropical general areas and the existence of a more varied mammalian fauna. (5) As conclusion, during the Early Tertiary of Patagonia the snakes were the most important predators together with ziphodont crocodiles, phorusrhacoid birds and borhyaenid ma...

Snakes from the Cerro Azul Formation (Upper Miocene), Central Argentina, with a review of fossil viperids from South America

Abstract South America contains a diverse Miocene snake record. Heretofore, the most significant assemblages were from the early and middle Miocene of Patagonia and Colombia. Colubroid vertebrae assignable to the ‘Colubridae’ and Viperidae are here reported from the upper Miocene Cerro Azul Formation at Caleufú, in La Pampa province, central Argentina. The viperid fossil is the oldest record of the family in South America and, together with molecular evidence, it supports the hypothesis of viperids first entering South America prior to the closure of the Isthmus of Panamá. South American viperid specimens also have been recognized from the Pliocene (aff. Bothrops) and Pleistocene of Buenos Aires province, Argentina. The presence of Bothrops during the early–middle Pleistocene near La Plata city suggests that during more humid intervals this genus had a wider distribution than at present. A previous report of a viperid from the late Pleistocene of Bolivia cannot be corroborated.

Palaeoenvironment and palaeoecology of three Cretaceous snakes: Pachyophis, Pachyrhachis, and Dinilysia

The palaeoecology of three Late Cretaceous snakes is evaluated. Pachyophis woodwardi Nopcsa, 1923 and Pachyrhachis problematicus Haas, 1979, are Cenomanian in age and are found in carbonate rocks deposited in marine inter-reef basin environments of the European and African Tethys Sea. Dinilysia patagonica Woodward, 1901, Coniacian in age, is considered closely allied to living anilioid snakes, and is found in clastic rocks deposited in a terrestrial inter-dune basin environment in northern Patagonia, Argentina. All three snakes are known from well preserved and articulated specimens found in sediments where detailed sedimentological and taphonomic analyses are possible. Pachyophis and Pachyrhachis were laterally compressed, have pachyostotic ribs and vertebrae, and small, narrow heads. These two snakes are interpreted as aquatic predators living in and around the margins of reef mounds on a shallow water carbonate platform. Dinilysia was a large bodied snake with a relatively large head, and is interpreted here as a terrestrial predator that lived in a dry, interdune basin environment dominated by aeolian sedimentation. Sedimentary units preserve ichnological evidence of burrowing insects and rooting plants.

An Overview of the South American Fossil Squamates

The evolution of squamates in South America is the result of the complex geological and paleoclimatic history of this part of the world. The incomplete and episodic fossil record allows us to know only a small part of this evolution. Most Mesozoic squamate remains come from the Patagonian region, but remarkable specimens have also been recovered from Brazil. Both major squamate clades (Iguania and Scleroglossa) are present in the South American Mesozoic. Remains of Mesozoic snakes are common and diverse in Cretaceous deposits, including some of the most primitive terrestrial forms. Paleogene and Neogene squamate remains have been recognized from Argentina, Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. Paleogene lizard record appears to be scarce in comparison to that of the Mesozoic, whereas snakes show an important Paleogene diversity. At least two extant boid snakes appeared during this epoch (Boa and Corallus). The South American Miocene included some extant genera of Iguania, Teiidae, and Boidae but extinct genera were also present. “Colubrids” appeared at the early Miocene, whereas the first viperid is known from the late Miocene. Most of the Paleogene and early Neogene squamate families and genera have been recognized outside their current range of distribution following favorable climatic conditions for ectothermic vertebrates. During the latest Miocene and Pliocene few extant squamate taxa are found to occur outside their present distribution. The earliest amphisbaenian of South America is known from the Pliocene. Most Pleistocene and Holocene squamate remains are assigned to living genera, and some extant species were recognized. Anat Rec, 297:349–368, 2014.

Emended diagnosis and phylogenetic relationships of the Upper Cretaceous fossil snake Najash rionegrina Apesteguía and Zaher, 2006

ABSTRACT The fossil snake Najash rionegrina, from the Cenomanian—Turonian (Upper Cretaceous) of Argentina, is reinterpreted after examination of the type and referred material. The current diagnosis is emended in the light of important considerations that cast doubt on the attribution of type and referred specimens (a braincase, a quadrate, and two dentary/lower jaw fragments) used to systematize this taxon. Alternative interpretations of the anatomy of the sacrum and hind limbs are proposed. Following the reevaluation of the anatomy of the type specimen and the removal from this taxon of the above-mentioned referred material, the phylogenetic position of N. rionegrina was tested in a series of maximum parsimony analyses that included all groups of extant snakes, all best-known fossil snakes (i.e., Pachyrhachis, Haasiophis, Eupodophis, Madtsoiidae, and Dinilysia), and alternative outgroups. Regardless of the outgroup used to polarize the character-state transformations, our phylogenetic analyses found no support for the hypothesis that Najash rionegrina occupies a position as the most basal snake. Depending on the outgroup, Najash is placed (1) in a position basal to all living snakes, but more derived than other fossil forms (most notably Pachyrhachis, Eupodophis, and Haasiophis); or (2) as the most basal representative of a clade of fossil snakes that is the sister group of living snakes; or (3) as the most basal representative of a clade of fossil snakes that is located between the Scolecophidia and the Alethinophidia. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Reappraisal of the south American Miocene snakes of the genus Colombophis, with description of a new species

A redescription of the extinct snake genus Colombophis is presented, on the basis of new specimens from the late Miocene of southwestern Brazilian Amazonia, and those previously reported for the middle Miocene of Colombia and Venezuela. The reappraisal of Colombophis allows the recognition of a new species, C. spinosus sp. nov. The revised diagnosis of the genus is based on the midtrunk vertebrae, distinct from those of other snakes mainly in the features of the neural arch, position and shape of the neural spine, inclination of the zygapophyses, shape of the centrum, and development of the haemal keel. The affinities of Colombophis with “Anilioidea” are still unresolved; it is distinguished from all known extinct and extant “anilioids” due to its great vertebral size and the frequent presence of paracotylar foramina. The posterior paired apophyses of the haemal keel in some vertebrae, and the high neural spine of C. spinosus also contrast significantly with the “anilioid” genera, making the allocation of the genus into this probably paraphyletic group not well supported. Here, we recognized Colombophis as a basal alethinophidian of uncertain relationships.

The oldest Brazilian Snakes from the Cenomanian (Early Late Cretaceous)

South American Mesozoic snake diversity is mostly represented by genera from the Cenomanian (Najash), Santonian— Campanian (Dinilysia), and Campanian—Maastrichtian (Alamitophis, Patagoniophis, Rionegrophis, and Australophis) of Patagonia, Argentina. In this paper, we describe a new snake genus and species, Seismophis septentrionalis, from the Cenomanian (early Late Cretaceous) of the Alcântara Formation, Maranhão, northeastern Brazil. The new snake comprises a posteriormost trunk vertebra and possibly a poorly preserved midtrunk vertebra. Both vertebrae share small size, zygosphene moderately thick with a rectilinear roof, absence of paracotylar foramina, presence of parazygantral foramina, and strongly marked parasagittal ridges of the neural arch. The new snake is here considered of uncertain systematic affinities, but probably close to the limbed snake Najash rionegrina. Although the material is very fragmentary and the systematic assignment is still unresolved, this snake represents the oldest, as well as probably the most primitive snake from Brazil.

New Records of Squamates from the Upper Miocene of South America

Abstract The Cerro Azul Formation of Argentina has yielded one of the highest diversities of squamate reptiles for the upper Miocene of South America including tupinambine teiids (Tupinambis sp.), “colubrids,” and viperids. Here, we describe new remains of Tupinambis sp. and “Colubridae” from this Formation as well as the first records of teiine teiids and boid snakes. The teiine represents the oldest record of this subfamily in South America. The squamate assemblage of the Cerro Azul Formation is consistent with the mammalian fauna in supporting the interpretation of a Chacoan-type palaeoenvironment for the upper Miocene of Central Argentina.