Sergio Alex Kugland de Azevedo

A new dinosaur (Theropoda, Spinosauridae) from the Cretaceous (Cenomanian) Alcântara Formation, Cajual Island, Brazil

A new spinosaurid taxon, Oxalaia quilombensis gen. et sp. nov., is described based on the anterior part of a snout and a fragment of a maxilla. These specimens were collected at the Laje do Coringa site, Late Cretaceous (Cenomanian) of the São Luis Basin. Unlike Cristatusaurus and Suchomimus, Oxalaia quilombensis lacks serrations on the teeth. The new species differs from Angaturama limai by having the anterior part of the premaxillae more expanded and by lacking a sagittal premaxillary crest. It further differs from Spinosaurus cf. S. aegyptiacus and the Algerian spinosaurid by the rounder shape of the terminal expansion. Furthermore, xalaia quilobensis has one functional tooth followed by two replacement teeth, a feature not previously observed in theropods. Oxalaia quilombensis appears to be more closely related to the spinosaurids found in North Africa than to the Brazilian members of this clade and thus further increases the diversity of these enigmatic predatory dinosaurs in this country.

ARE EXTANT PODOCNEMIDID TURTLES RELICTS OF A WIDESPREAD CRETACEOUS ANCESTOR

Abstract We re-analyzed the most recent morphological data matrix for Pleurodira with inclusion of the Upper Cretaceous Brazilian pleurodiran turtle, Bauruemys elegans (Suárez, 1969), as new Operational Taxonomic Unit. An exhaustive search based on 50 characters for 11 taxa was performed to asses the phylogenetic relationships within the Pelomedusoides and a single most parsimonious tree of 64 steps was found. This new phylogenetic hypothesis places B. elegans as a basal form of Podocnemididae and is used to found a new biogeographic model for the Pelomedusoides. The biogeographical approach was performed with direct analysis of vicariance, using historical sequence of vicariance and phylogenetic information to construct an event-based model. Thus, inspection of distributions maps of Pelomedusoides and the phylogenetic arrangement proposed here were used to correlate cladogenesis and vicariance events during Cretaceous. Current biogeographic hypotheses suggest that living Pelomedusoides distribution and relationships could be the result of large-scale extinctions with extant taxa being relicts of a widespread group. The examination of relationships within Pelomedusoides allows the association of vicariance events of Gondwana fragmentation during the Cretaceous with the isolation of pelomedusoid lineages. We identified three vicariant events: the separation of northern Pelomedusoides and southern Chelidae (node of divergence of Chelidae); the isolation of Africa from Gondwana (node of divergence of Hamadachelys); and the separation of South America and India/Madagascar (node of divergence of Podocnemididnae and Erymnochelyinae). Extant Podocnemidinae (restricted to north South America) would derivate from a south South American source. Its ancestor would have had an autochthons development in South America, expanding its distribution northwards. The presence of Erymnochelyinae in Madagascar would be explained by the migration of a South American ancestor via Antarctica.

New Information about Pelomedusoides (Testudines: Pleurodira) from the Cretaceous of Brazil

Brazilian turtle remains date from the Cretaceous and have been recovered from in 11 different basins. Two of these are of particular importance because of the richness of species and specimens: Araripe (Early Cretaceous) and Bauru (Late Cretaceous). Here we present information based on new material that adds to our understanding of the diversity of turtles from Araripe Basin and provides a basis for discussion of the taxonomic status of some species from Bauru Basin. A new specimen from the Araripe Basin that is from the Crato Formation, although generically indeterminate is proposed to be the oldest representative of the clade Podocnemidera. This allocation would extend the stratigraphic range of the Podocnemidera to the Aptian/Albian, matching that of its sister group, the Pelomedusera. New specimens from the Bauru Basin allow a better understanding of the morphology of the shell in Roxochelys and an assessment and interpretation of diagnostic features used to distinguish Bauru Basin endemic forms. Our preliminary examination of this material leads us to conclude that the diversity described in this basin is overestimated. As consequence, we argue that Bauru Basin includes only two well diagnosed species of turtles: Roxochelys wanderleyi and Bauruemys elegans.

A possible chelonian egg from the Brazilian late cretaceous

This paper describes a possible fossil egg proceeding from the Bauru Group, Late Cretaceous of Paraná Basin, Brazil. External morphology, dimensions, texture and shell ornamentation examined under electron microscopy show close resemblance to the Recent podocnemidid chelonian eggs. Association with bony material in the outcrop suggests that it is related to a species of Podocnemis. Computerized tomography reveals a high density outer region corresponding to the shell component layers, and successive layers with decreasing density towards the nucleus. An area of high density in the central region may represent remains of an embryo.

Pelvic and hind limb musculature of Staurikosaurus pricei (Dinosauria: Saurischia)

The study of pelvic and hind limb bones and muscles in basal dinosaurs is important for understanding the early evolution of bipedal locomotion in the group. The use of data from both extant and extinct taxa placed into a phylogenetic context allowed to make well-supported inferences concerning most of the hind limb musculature of the basal saurischian Staurikosaurus pricei Colbert, 1970 (Santa Maria Formation, Late Triassic of Rio Grande do Sul, Brazil). Two large concavities in the lateral surface of the ilium represent the origin of the muscles iliotrochantericus caudalis plus iliofemoralis externus (in the anterior concavity) and iliofibularis (in the posterior concavity). Muscle ambiens has only one head and originates from the pubic tubercle. The origin of puboischiofemoralis internus 1 possibly corresponds to a fossa in the ventral margin of the pré-acetabular iliac process. This could represent an intermediate stage prior to the origin of a true pré-acetabular fossa. Muscles caudofemorales longus et brevis were likely well developed, and Staurikosaurus is unique in bearing a posteriorly projected surface for the origin of caudofemoralis brevis.

Recovering missing data: estimating position and size of caudal vertebrae in Staurikosaurus pricei Colbert, 1970

Missing data is a common problem in paleontology. It makes it difficult to reconstruct extinct taxa accurately and restrains the inclusion of some taxa on comparative and biomechanical studies. Particularly, estimating the position of vertebrae on incomplete series is often non-empirical and does not allow precise estimation of missing parts. In this work we present a method for calculating the position of preserved middle sequences of caudal vertebrae in the saurischian dinosaur Staurikosaurus pricei, based on the length and height of preserved anterior and posterior caudal vertebral centra. Regression equations were used to estimate these dimensions for middle vertebrae and, consequently, to assess the position of the preserved middle sequences. It also allowed estimating these dimensions for non-preserved vertebrae. Results indicate that the preserved caudal vertebrae of Staurikosaurus may correspond to positions 1-3, 5, 7, 14-19/15-20, 24-25/25-26, and 29-47, and that at least 25 vertebrae had transverse processes. Total length of the tail was estimated in 134 cm and total body length was 220-225 cm.

A brief note on the paleofauna of "Tartaruguito site", Adamantina Formation, Bauru Group, Brazil

Universidade Federal do Rio de Janeiro (UFRJ) Museu Nacional Departamento de Geologia e Paleontologia

Biomechanical comments about Triassic dinosaurs from Brazil

Triassic dinosaurs of Brazil are found in Santa Maria and Caturrita formations, Rio Grande do Sul state, Brazil. There are three species known from the Santa Maria Formation (Staurikosaurus pricei, Saturnalia tupiniquim and Pampadromaeus barberenai), and two from Caturrita Formation (Guaibasaurus candelariensis and Unaysaurus tolentinoi). These dinosaur materials are, for the most part, well preserved and allow for descriptions of musculature and biomechanical studies. The lateral rotation of the Saturnalia femur is corroborated through calculations of muscle moment arms. The enhanced supracetabular crest of Saturnalia, Guaibasaurus, Staurikosaurus, Herrerasaurus ischigualastensis, Efraasia minor and Chormogisaurus novasi suggests that basal dinosaurs may have maintained an inclination of the trunk at least 20o on the horizontal axis. The pectoral girdle articulation of basal sauropodomorphs (Saturnalia and Unaysaurus) was established using a new method, the Clavicular Ring, and the scapular blade remains near 60o on the horizontal axis. This is a plesiomorphic condition among sauropodomorphs and is also seen in the articulated plateosauridae Seitaad ruessi. The Brazilian basal dinosaurs were lightweight with a body mass estimated around 18.5 kg for Staurikosaurus, 6.5 kg for Saturnalia, and 17 kg for Guaibasaurus. Pampadromaeus probably weighed 2.5 kg, but measures of its femur are necessary to confirm this hypothesis. The Triassic dinosaurs from Brazil were diversified but shared some functional aspects that were important in an evolutionary context.