Juan I. Canale

New carnivorous dinosaur from the Late Cretaceous of NW Patagonia and the evolution of abelisaurid theropods

A nearly complete skeleton of the new abelisaurid Skorpiovenator bustingorryi is reported here. The holotype was found in Late Cenomanian–Early Turonian outcrops of NW Patagonia, Argentina. This new taxon is deeply nested within a new clade of South American abelisaurids, named Brachyrostra. Within brachyrostrans, the skull shortening and hyperossification of the skull roof appear to be correlated with a progressive enclosure of the orbit, a set of features possibly related to shock-absorbing capabilities. Moreover, the development of horn-like structures and differential cranial thickening appear to be convergently acquired within Abelisauridae. Based on the similarities between Skorpiovenator and carcharodontosaurid tooth morphology, we suggest that isolated teeth originally referred as post-Cenomanian Carcharodontosauridae most probably belong to abelisaurids.

A bizarre Cretaceous theropod dinosaur from Patagonia and the evolution of Gondwanan dromaeosaurids

Fossils of a predatory dinosaur provide novel information about the evolution of unenlagiines, a poorly known group of dromaeosaurid theropods from Gondwana. The new dinosaur is the largest dromaeosaurid yet discovered in the Southern Hemisphere and depicts bizarre cranial and postcranial features. Its long and low snout bears numerous, small-sized conical teeth, a condition resembling spinosaurid theropods. Its short forearms depart from the characteristically long-armed condition of all dromaeosaurids and their close avian relatives. The new discovery amplifies the range of morphological disparity among unenlagiines, demonstrating that by the end of the Cretaceous this clade included large, short-armed forms alongside crow-sized, long-armed, possibly flying representatives. The new dinosaur is the youngest record of dromaeosaurids from Gondwana and represents a previously unrecognized lineage of large predators in Late Cretaceous dinosaur faunas mainly dominated by abelisaurid theropods.

A diplodocid sauropod survivor from the early cretaceous of South America.

Diplodocids are by far the most emblematic sauropod dinosaurs. They are part of Diplodocoidea, a vast clade whose other members are well-known from Jurassic and Cretaceous strata in Africa, Europe, North and South America. However, Diplodocids were never certainly recognized from the Cretaceous or in any other southern land mass besides Africa. Here we report a new sauropod, Leikupal laticauda gen. et sp. nov., from the early Lower Cretaceous (Bajada Colorada Formation) of Neuquén Province, Patagonia, Argentina. This taxon differs from any other sauropod by the presence of anterior caudal transverse process extremely developed with lateroventral expansions reinforced by robust dorsal and ventral bars, very robust centroprezygapophyseal lamina in anterior caudal vertebra and paired pneumatic fossae on the postzygapophyses in anterior-most caudal vertebra. The phylogenetic analyses support its position not only within Diplodocidae but also as a member of Diplodocinae, clustering together with the African form Tornieria, pushing the origin of Diplodocoidea to the Middle Jurassic or even earlier. The new discovery represents the first record of a diplodocid for South America and the stratigraphically youngest record of this clade anywhere.

Sauropod haemal arches: morphotypes, new classification and phylogenetic aspects

Sauropod haemal arches are caudal bony structures that have been traditionally incorporated into two different types observed in different anatomical views: Y-shaped (anterior view) and forked (lateral view). This research proposes a classification combining information observed in anterior and lateral views. Four types of ‘Y-shaped’ and six types of ‘V-shaped’ chevrons were recognised. Complete chevron series in some eusauropods allows the comparison of topological equivalent structures along the tail and also among taxa. A basal titanosaur from Argentina exhibits mid-caudal chevron morphology in which more than one cranial and caudal process is present, arising from the distal blades as well as from the proximal rami, a condition not seen before in a sauropod dinosaur. The morphological variability seen in sauropod chevrons along the tail is in close relationship with the development and distribution of muscle. caudofemoralis longus, as seen in extant crocodiles and as previously proposed for non-avian theropods and for caudal centra and transverse processes of sauropod dinosaurs. Two new characters related to middle chevrons are proposed here, in which the transitional morphology is described.

Osteology and phylogenetic relationships of Tyrannotitan chubutensis Novas, de Valais, Vickers-Rich and Rich, 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina

The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid theropods. The carcharodontosaurids recorded in the Albian–Cenomanian of Gondwana are the youngest and most derived members of this clade. Tyrannotitan chubutensis, from the Cerro Castaño Member of Cerro Barcino Formation (Albian; Chubut Group), Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of Tyrannotitan chubutensis together with a new diagnosis of the species. The new information results in a better understanding of this taxon and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of Giganotosaurus is reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini.

THE YOUNGEST RECORD OF THE CRETACEOUS SNAKE GENUS DINILYSIA (SQUAMATA, SERPENTES)

Abstract We report the youngest record of the Cretaceous snake Dinilysia, from the Late Cretaceous (Campanian) Anacleto Formation (Campanian) of Neuquén province, Argentina. The specimen consists on twenty four articulated mid-posterior trunk vertebrae with the base of their respective ribs. The specimen is refered to Dinilysia on the basis of several morphological features, including a triangular shape of the vertebral body, straight posterior border of the neural arch, large craniocaudal extension of the neural spine, absence of parazygantral foramen, and arqual ridges. This represents the youngest record of the genus Dinilysia, thus extending its biochron up to the Campanian age.

Changes in vertebral laminae across the cervicodorsal transition of a well-preserved rebbachisaurid (Dinosauria, Sauropoda) from the Cenomanian of Patagonia, Argentina

ALEJANDRO HALUZA,1 JUAN I. CANALE,1,2 ALEJANDRO OTERO,*,2,3 LEANDRO M. PÉREZ,2,4 and CARLOS A. SCANFERLA2,5; 1Museo Municipal “Ernesto Bachmann,” Dr. Natali s/n, Villa El Chocón, Neuquén, Argentina, jujuyaspis@yahoo. com; juanignaciocanale@yahoo.com.ar; 2Consejo Nacional de Investigaciones Cientı́ficas y Técnicas; 3Departamento Cientı́fico Paleontologı́a de Vertebrados, Museo de La Plata, Paseo del Bosque s/n (1900), La Plata, Buenos Aires, Argentina, alexandros.otero@gmail.com; 4Cátedra de Rocas Sedimentarias, Facultad de Ciencias Naturales y Museo (UNLP), Av. 60 y 122 s/n, La Plata, Buenos Aires, Argentina, pilosaperez@gmail.com; 5Museo Argentino de Ciencias Naturales “Bernardino Rivadavia,” Av. Angel Gallardo 470, 1405, Buenos Aires, Argentina, agustin scanferla@yahoo.com.ar

Cranial endocast of the carcharodontosaurid theropod Giganotosaurus carolinii Coria & Salgado, 1995

A complete endocast of Giganotosaurus carolinii CORIA & SALGADO, 1995 was made in latex after removing mechanically the sediment filling of the cerebral cavity of the braincase, thereby allowing the description of the endocranial anatomy of the specimen. The endocast was compared with the other few known natural or artificial theropod endocasts, including the two species of the African allosauroid species Carcharodontosaurus saharicus and C. idiguensis. As in Carcharodontosaurus, the olfactory bulbs in Giganotosaurus are aligned with the forebrain, the midbrain is posteroventrally inclined and the hindbrain is parallel but ventral to the forebrain, showing similarly angled cephalic and pontine flexures. The cranial nerves and blood vessels have a similar disposition as in Carcharodontosaurus saharicus. However, in Giganotosaurus there is only one branch for cranial nerve XII, and cranial nerve XI has a separate internal opening from the vagus foramen (metotic foramen). In C. saharicus, there is a separate opening as well, but it is anterior in position and was probably utilized by cranial nerve IX. The length of the endocast of Giganotosaurus, including the olfactory bulbs, is approximately 19 % longer than the endocast in Carcharodontosaurus saharicus.

Cranial ontogenetic variation in Mapusaurus roseae (Dinosauria: Theropoda) and the probable role of heterochrony in carcharodontosaurid evolution

The carcharodontosaurid theropod Mapusaurus roseae (Cenomanian of Neuquén Province, Argentina) is represented by at least seven disarticulated individuals from a monospecific bonebed, all of different sizes and presumably different stages of maturity. We report a series of anatomical differences between repeated skull bones of Mapusaurus, which we interpret as produced by peramorphic heterochronic processes. The materials analyzed include maxillae, lacrimals, dentaries, and isolated teeth. Most of the differences were recorded in the maxilla, the most noticeable change being the reduction of the pneumaticity. We found that some of the synapomorphic characters of derived carcharodontosaurids appear to be the result of peramorphic heterochronies, as in the strongly ornamented facial bones, and the single opening in the anteroventral corner of the antorbital fossa in the maxilla.KurzfassungDer carcharodontosauride Theropode Mapusaurus rosae (aus dem Cenoman der Provinz Neuquén, Argentinien) ist durch mindestens 7 disartkulierte Individuen verschiedener Größe und vermutlich unterschiedlicher ontogenetischer Stadien aus einem monospezifischen Bonebed repräsentiert. Wir beschreiben eine Reihe anatomischer Unterschiede zwischen mehrfach vorkommenden Schädelknochen von Mapusaurus, die wir als Ergebnis peramorphischer Heterochronie-Prozesse interpretieren. Die untersuchten Elemente umfassen Maxillae, Lacrimale, Dentale und isolierte Zähne. Die größten Änderungen finden sich im Maxillare, wobei besonders die Reduktion der Pneumatisierung auffällt. Wir stellen fest, dass einige der apomorphen Merkmale fortschrittlicher Carcharodontosauriden auf Heterochronie zurückzuführen sind, darunter die stark ornamentierten Schädelknochen und das Vorhandensein nur einer Öffnung im anteroventralen Teil der Fossa antorbitalis im Maxillare.

New rebbachisaurid cranial remains (Sauropoda, Diplodocoidea) from the Cretaceous of Patagonia, Argentina, and the first endocranial description for a South American representative of the clade

ABSTRACT Here we report new rebbachisaurid material (MMCh-PV 71) recovered from the Candeleros Formation (Cenomanian) of northwest Patagonia, Argentina. The cranial remains consist of a partial braincase and a right quadrate. Fractures in the braincase exposed the endocranial cavity, allowing the first study of the brain and inner ear morphologies of a South American rebbachisaurid. The braincase and cranial endocast both exhibit traits similar to those observed in the Cretaceous rebbachisaurs Nigersaurus from Africa and Limaysaurus from Argentina, although in terms of osteology, the South American taxa are highly similar. The endocast of MMCh-PV 71 is more similar to that of Nigersaurus than to those of Diplodocus and Camarasaurus, suggesting some probable rebbachisaurid features such as the noteworthy presence of the flocculus. The overall morphology of the quadrate shows similarities with Limaysaurus and Nigersaurus. However, differences such as the broader posterior fossa and the shape and orientation of the head and the pterygoid process indicate that the new specimen could represent a distinct taxon.