Felipe L. Pinheiro

New information on the pterosaur Tupandactylus imperator, with comments on the relationships of Tapejaridae

A new specimen of Tupandactylus imperator, comprising an incomplete skull with associated lower jaw, is described. The material is the best preserved specimen of this species known so far and provides new information on the anatomy of this pterodactyloid pterosaur, especially with respect to the morphology of the lower jaw, the first one formally described for the species. Also, the new specimen shows an extensive preservation of soft tissues such as the soft-tissue component of the headcrest, ramphoteca associated with the premaxillae and lower jaw, as well as probable pycnofibres. A phylogenetic analysis was performed in order to test the relationships of the taxon within Tapejaridae. The results of the analysis support Tapejaridae, as well as monophyly of Tapejarinae and Thalassodrominae.

An exceptional fossil skull from South America and the origins of the archosauriform radiation

Birds, dinosaurs, crocodilians, pterosaurs and their close relatives form the highly diverse clade Archosauriformes. Archosauriforms have a deep evolutionary history, originating in the late Permian, prior to the end-Permian mass extinction, and radiating in the Triassic to dominate Mesozoic ecosystems. However, the origins of this clade and its extraordinarily successful body plan remain obscure. Here, we describe an exceptionally preserved fossil skull from the Lower Triassic of Brazil, representing a new species, Teyujagua paradoxa, transitional in morphology between archosauriforms and more primitive reptiles. This skull reveals for the first time the mosaic assembly of key features of the archosauriform skull, including the antorbital and mandibular fenestrae, serrated teeth, and closed lower temporal bar. Phylogenetic analysis recovers Teyujagua as the sister taxon to Archosauriformes, and is congruent with a two-phase model of early archosauriform evolution, in response to two mass extinctions occurring at the end of the Guadalupian and the Permian.

Anhanguera taxonomy revisited: is our understanding of Santana Group pterosaur diversity biased by poor biological and stratigraphic control?

Background Anhanguerids comprise an important clade of pterosaurs, mostly known from dozens of three-dimensionally preserved specimens recovered from the Lower Cretaceous Romualdo Formation (northeastern Brazil). They are remarkably diverse in this sedimentary unit, with eight named species, six of them belonging to the genus Anhanguera. However, such diversity is likely overestimated, as these species have been historically diagnosed based on subtle differences, mainly based on the shape and position of the cranial crest. In spite of that, recently discovered pterosaur taxa represented by large numbers of individuals, including juveniles and adults, as well as presumed males and females, have crests of sizes and shapes that are either ontogenetically variable or sexually dimorphic. Methods We describe in detail the skull of one of the most complete specimens referred to Anhanguera, AMNH 22555, and use it as a case study to review the diversity of anhanguerids from the Romualdo Formation. In order to accomplish that, a geometric morphometric analysis was performed to assess size-dependent characters with respect to the premaxillary crest in the 12 most complete skulls bearing crests that are referred in, or related to, this clade, almost all of them analyzed first hand. Results Geometric morphometric regression of shape on centroid size was highly statistically significant (p = 0.0091) and showed that allometry accounts for 25.7% of total shape variation between skulls of different centroid sizes. Premaxillary crests are both taller and anteroposteriorly longer in larger skulls, a feature consistent with ontogenetic growth. A new diagnosis is proposed for Anhanguera, including traits that are nowadays known to be widespread within the genus, as well as ontogenetic changes. AMNH 22555 cannot be referred to “Anhanguera santanae” and, in fact, “Anhanguera santanae”, “Anhanguera araripensis”, and “Anhanguera robustus” are here considered nomina dubia. Discussion Historically, minor differences in crest morphology have been used in the definition of new anhanguerid species. Nowadays, this practice resulted in a considerable difficulty in referring well-preserved skulls into known taxa. When several specimens are analyzed, morphologies previously believed to be disparate are, in fact, separated by a continuum, and are thus better explained as individual or temporal variations. Stratigraphically controlled excavations on the Romualdo Formation have showed evidence for faunal turnover regarding fish communities. It is thus possible that some of the pterosaurs from this unit were not coeval, and might even represent anagenetic morphotypes. Unfortunately, amateur collecting of Romualdo Formation fossils, aimed especially at commerce, resulted in the lack of stratigraphic data of virtually all its pterosaurs and precludes testing of these further hypotheses.

On a New Stereospondylomorph Temnospondyl from the Middle—Late Permian of Southern Brazil

A new temnospondyl is described from the Middle—Upper Permian sequence of the Paraná Basin (Rio do Rasto Formation) in southern Brazil. The material consists of disarticulated cranial and postcranial elements, preserved in association. The cranial elements include part of the orbital region of the skull roof, the basicranium, a number of endocranial elements, stapes and a right hemimandible. The postcranial elements include vertebrae, ribs, pectoral girdle elements, a right femur and a cluster of scales. The new species displays a rhinesuchid pattern, which is similar to the South African rhinesuchids from the Upper Permian Beaufort Group of the Karoo Basin, but differs from them by the presence of a robust and elongated epipterygoid with a blade-like anterior process in addition to elongated and deeper muscular pockets on the parasphenoid, which allow the assignment of this specimen to a new species. However, the phylogenetic analysis grouped the material described herein and Australerpeton cosgriffi inside Stereospondylomorpha, in a transitional position between the Laurasian assemblages and South African temnospondyls. This result supports a connection between the Brazilian and Eastern European Permian fauna and provides important data for future biostratigraphic studies.

A peculiar bonebed reinforces gregarious behaviour for the Triassic dicynodont Dinodontosaurus

ABSTRACT The discovery and study of bonebeds can provide unique information on the biology of extinct animals. Here we interpret the taphonomic history of a monotypic bonebed composed by several individuals attributable to the dicynodont Dinodontosaurus sp. collected in a classic locality from the Dinodontosaurus Assemblage Zone (Middle Triassic of Brazil). Following the estimation of the minimal number of individuals, we analyzed several biostratinomic processes, such as transport and fragmentation. The assemblage is composed of at least six individuals, all of which are juveniles (although of different sizes), packed in close association and displaying different articulation levels, which indicates a moderate time of subaerial exposure before burial. The dispersion is comprised of bone elements of different Voorhies Groups, indicating the absence of hydraulic selection by transport and a short distance from the death site. The hypothesis of trampling is not discarded, as some bones show pre-burial cracks and fractures. The association of juveniles suggests that factors like insufficient nutrition, abandonment, and diseases could be the cause of death. The monotypic nature of the assemblage, when analyzed together with its possible taphonomic history, allows us to infer gregarious behaviour in Dinodontosaurus.

Isolated archosauriform teeth from the Upper Triassic Candelária Sequence (Hyperodapedon Assemblage Zone, Southern Brazil)

We describe isolated teeth found in the locality “Sítio Piveta” (Hyperodapedon Assemblage Zone, Candelaria Sequence, Upper Triassic of the Paraná Basin). The material consists of five specimens, here classified into three different morphotypes. The morphotype I is characterized by pronounced elongation, rounded base and symmetry between lingual and labial surfaces. The morphotype II presents serrated mesial and distal edges, mesial denticles decreasing in size toward the base, distal denticles present until the base and asymmetry, with a flat lingual side and rounded labial side. The morphotype III, although similar to morphotype II, has a greater inclination of the posterior carinae. The conservative dental morphology in Archosauriformes makes difficult an accurate taxonomic assignment based only on isolated teeth. However, the specimens we present are attributable to “Rauisuchia” (morphotype II and III) and, possibly, Phytosauria (morphotype I). The putative presence of a phytosaur in the Carnian Hyperodapedon Assemblage Zone would have impact in the South American distribution of the group. The taxonomic assignments proposed herein contribute to the faunal composition of the Hyperodapedon Assemblage Zone, a critical unit on the study of the Upper Triassic radiation of archosaurs.