An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina
Authors:
Apesteguía et al
Abstract:
Background
Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit.
Methodology/ Principal Findings
A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton.
Conclusions/ Significance
Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.
pop sci write up.
A New Carcharodontosauria (Theropoda) from the Early Cretaceous of Guangxi, Southern China
Authors:
Mo et al
Abstract:
A new large-bodied theropod dinosaur, Datanglong guangxiensis gen. et sp. nov., was recovered from the Lower Cretaceous Xinlong Formation of the Datang Basin, Guangxi. It is unique in several features including: posteriormost dorsal vertebra with teardrop-shaped pneumatic foramen confined by enlarged pcdl, acpl and the centrum; posteriormost dorsal with well-developed, horizontal prpl; posteriormost dorsal with a parapophysis projecting more laterally than the diapophysis; brevis fossa shallow with short, ridge-like medial blade; and iliac pubic peduncle with posteroventrally expanded margin. Cladistic analysis supports the idea that this new taxon Datanglong guangxiensis is a primitive member of the Carcharodontosauria in possessing two unambiguous synapomorphies: large external pneumatic foramina and internal spaces present in the lateral surface of ilium, and a peg-and-socket ischiac articulation with the ilium. The presence of the new taxon from Guangxi further confirms that Carcharodontosauria were cosmopolitan large-bodied predators during the Early-mid Cretaceous.
A large-bodied theropod (Tetanurae: Carcharodontosauria) from the Mirambel Formation (Barremian) of Spain
Authors:
Gasca et al
Abstract:
We describe an isolated distal femur of a large-sized theropod dinosaur from the Mirambel Formation, Teruel province, Spain. It comes from the Ladruñán-3 fossil locality, which represents a sandstone channel deposit that is early Barremian (Early Cretaceous) in age. This femur can be identified as belonging to an undetermined stem carcharodontosaurid allosauroid. The distal outline is similar to that of the basal carcharodontosaurid Acrocanthosaurus, which bears a ridge for the cruciate ligaments in the flexor groove and a deep but narrow extensor groove. This new carcharodontosaurid remnant extends the presence of this large-bodied theropod lineage in the Iberian Peninsula back to the early Barremian. The coexistence of carcharodontosaurids, ceratosaurians and spinosaurids in the Barremian of the Iberian Peninsula echoes the clade composition of large-bodied predator dinosaurs characteristic of other Early Cretaceous faunas in Gondwana. This suggests that Early Cretaceous Iberian ecosystems were as diverse as other Barremian European assemblages, with carcharodontosaurids being exclusive to Iberia.
Osteology and phylogenetic relationships of Tyrannotitan chubutensis Novas, de Valais, Vickers-Rich and Rich, 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina
Authors:
Canale et al
Abstract:
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.
