Eberhard Frey

The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia

While the crocodyliform lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms—members of Eusuchia—do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98–95 Myr ago; Albian–Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms—a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.

IRRITATOR CHALLENGERI , A SPINOSAURID (DINOSAURIA: THEROPODA) FROM THE LOWER CRETACEOUS OF BRAZIL

Abstract The holotype of Irritator challengeri Martill et al., 1996 from the Romualdo Member of the Santana Formation (Lower Cretaceous) in northeastern Brazil represents the most complete skull of a spinosaurid known to date. The now fully prepared specimen provides much new information on the cranial structure in these enigmatic predatory dinosaurs. The skull is remarkably narrow, especially in the region of the elongated snout. The maxillae are in broad contact along the midline, forming an extensive secondary bony palate. The maxillary teeth have straight or slightly recurved, conical crowns, with thin, fluted enamel and distinct but smooth carinae. As in Baryonyx walkeri, the anterior and ventral processes of the lacrimal meet at a more acute angle than in most non-avian theropod dinosaurs. The braincase is short anteroposteriorly but deep dorsoventrally, extending ventrally far below the occipital condyle. Irritator challengeri most closely resembles Spinosaurus aegyptiacus in the structure of its teeth, but more extensive comparisons between the two taxa are currently impossible due to the limited amount of cranial material known for the latter.

New specimens of Pterosauria (Reptilia) with soft parts with implications for pterosaurian anatomy and locomotion

Abstract New specimens of pterosaurs with soft-part preservation from the Solnhofen Lithographic Limestone (S Germany) and the Crato Formation (northeastern Brazil) yield hitherto unknown and unexpected details of pterosaur anatomy: the presence and internal anatomy of softtissue crests, the internal anatomy of the brachiopatagium, including a blood vessel system and structural details of foot and hand. Some consequences for pterosaurian flight, thermoregulation and aspects of evolution are discussed.

A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil

The skull of a new, and highly unusual crested dinosaur with an elongate rostrum is the first dinosaur to be named from the Santana Formation of NE Brazil. Irritator challengeri gen. et sp. nov was most likely a maniraptoran dinosaur, but its affinities to other maniraptorans remain to be established. Unique features for Irritator include the pattern of tooth replacement, a highly reduced supratemporal fenestra, extreme lateral compression of the rostrum and a saggital crest comprised of the frontal and parietal bones. Irritator was most probably a piscivore. A land link between South America and the dinosaurian faunal province of North America and Asia is indicated, probably via Africa.

Ecology, Systematics and Biogeographical Relationships of Dinosaurs, Including a New Theropod, from the Santana Formation (?Albian, Early Cretaceous) of Brazil

Although rare, dinosaurs are well preserved in calcareous nodules of the Santana Formation (Early Cretaceous, ?Albian) of the Araripe Basin, in northeastern Brazil. So far, including only a spinosauroid and three coelurosaurs, the dinosaur fauna appears depauperate. High theropod diversity in assemblages where other dinosaurs are rare or absent is not unique to the Santana Formation. It is seen also in several other assemblages, including Solnhofen and the Maevarano Formation of Madagascar. We consider several factors, including the occurrence of intraguild predation, the possibility that small theropods could subsist in marginal environments, and reliance on coastal resources, that may have been responsible for this apparent ecological imbalance. A new coelurosaur from the Santana Formation, here formally named Mirischia asymmetrica, is shown to be distinct from Santanaraptor placidus [Kellner, A.W.A. (1999) “Short note on a new dinosaur (Theropoda, Coelurosauria) from the Santana Formation (Romualdo Member, Albian) northeastern Brazil”, Boletim do Museu Nacional, Nova Serie, Rio de Janeiro, Brasil 49, 1–8]. Other theropods from the Santana Formation are briefly reviewed. Mirischia is a compsognathid, more similar to the European Compsognathus than to the Asian Sinosauropteryx.

A new crested ornithocheirid from the Lower Cretaceous of northeastern Brazil and the unusual death of an unusual pterosaur

Abstract An exceptionally well-preserved cranium and mandible of a new species of pterodactyloid pterosaur from the Nova Olinda Member of the Crato Formation (Aptian, Early Cretaceious) of the Araripe Basin, northeastern Brazil, is described. The new taxon is characterized by the presence of a caudally directed parietal crest similar to that seen in pteranodontids, but is referred to the Ornithocheiridae of the Ornithocheiroidea. The specimen is referred to a new genus within the Ornithocheiridae, as it lacks the diagnostic rostral crest and instead possesses this parietal crest oriented. A lanceolate leaf with frayed distal end wedged between the mandibular rami suggests the cause of death for the specimen.

A new species of tapejarid pterosaur with soft-tissue head crest

Abstract Two specimens of a tapejarid pterosaur (Pterodactyloidea, Tapejaridae) are described as representing a new species. Both specimens show evidence for soft tissues preserved in association with a sagittal bony cranial crest. Both specimens are from the Nova Olinda Member Konservat Lagerstätte of the Crato Formation of the Araripe Basin, northeastern Brazil. They represent the second tapejarid species from this formation. Comparisons are made with other crested pterosaurs and comments on the utility and aerodynamics of pterosaurian head crests are made.

The Extent of the Pterosaur Flight Membrane

The shape and extent of the membranous brachioptagium in pterosaurs remains a controversial topic for those attempting to determine the aerodynamic performance of the first vertebrate fliers. Various arguments in favour of the trailing edge terminating against either the torso or hip, the femur, the ankle, or different locations for various taxa, has resulted in several published reconstructions. Uncertainty over the correct model is detrimental to both aerodynamic and palaeoecological studies that are forced to simultaneously consider multiple and highly variable configurations for individual taxa. A review of relevant pterosaur specimens with preserved soft tissues or impressions of the wing membrane, however, strongly suggests that the trailing edge of the wing extended down to the lower leg or ankle in all specimens where the brachiopatagium is completely preserved. This configuration is seen across a phylogenetically broad range of pterosaurs and is thus likely to have been universally present throughout the Pterosauria. Support for opposing hypotheses where the trailing edge terminates against the body, hip, or knee are based on several specimens where the wing membrane is either incomplete or has undergone post-mortem contraction. An ankle attachment does not rule out a high aspect ratio wing as the curvature of the trailing edge and the ratio of the fore to hind limbs also play a major role in determining the final shape of the membrane.

Reconstruction of the bracing system of the trunk and tail in hyposaurine dyrosaurids (Crocodylomorpha; Mesoeucrocodylia)

ABSTRACT The axial skeleton of hyposaurine dyrosaurids differs significantly from that of extant crocodylians, most notably in the height of the neural spines, the vertically oriented thoracic ribs and osteoderms that lack external keels. This indicates a different configuration of the epaxial musculature for hyposaurine dyrosaurids compared with extant crocodylians and possibly all other fossil species. In the trunk, m. transversospinalis tendons formed a tendinal lattice. M. tendinoarticularis and m. longissimus dorsi were divided into high, medially open myoseptal cones. M. iliocostalis of hyposaurine dyrosaurids was larger than in extant crocodylians and braced the arcade of the vertebral column during locomotion. The trunk bracing-system of hyposaurine dyrosaurids is referred to as a Hyposaurus-type bracing system, and is modeled as a segmented, hydraulically stabilized string-and-bow-construction, with the single segments consisting of inverse T-beams. The trunk bracing-system and osteoderm morphology of hyposaurine dyrosaurids indicate that the vertebral column could not be sufficiently stabilized against dorsoventral shear loads, and possibly transverse shear loads. As a consequence, the high walk and gallop could only be performed by individuals with low body mass. In the tail, the enormously elongated neural spines indicate a large cross section of the epaxial musculature, which facilitated the effective use of aquatic locomotor modes like axial and hybrid swimming.

Reinterpretation of a Chilean pterosaur and the occurrence of Dsungaripteridae in South America

A fragmentary specimen of pterosaur originally assigned to the genus Pterodaustro Bonaparte, 1970 is reassessed. The presence of a sagittal dorsal cranial crest on a fragment of nasopre- orbital arcade with linear vertical trabeculae and the occurrence of alveolar protuberances on the os dentale indicate the new specimen has similarities with crested pterodactyloid pterosaurs of the family Ctenochasmatidae, and with members of the Dsungaripteridae. The presence of alveolar protuber- ances allows us to assign the specimen to the Dsungaripteridae. It forms the basis of a new genus and species, Domeykodactylus ceciliae.