David M. Martill

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.

Dinosaurs and other fossil vertebrates from fluvial deposits in the Lower Cretaceous of southern Tunisia

Remains of dinosaurs and other vertebrates (sharks, bony fishes, coelacanths, turtles, crocodilians, pterosaurs) are reported from the Chenini Formation of the Tataouine region in southern Tunisia. The Formation is part of the ‘continental intercalaire’, a succession of continental deposits of Early to Late Cretaceous age distributed over the whole of North Africa and the Sahara. It consists of bar and channel deposits of broad rivers that flowed NNW from the mid-Sahara region towards the southern shore of Tethys. Dinosaur-bearing units in the ‘continental intercalaire’ have been dated to the Hauterivian to Cenomanian, and the Chenini Formation is possibly Albian in age. Dinosaur fossils include abundant teeth of the theropods Carcharodontosaurus and Spinosaurus, as well as postcranial elements of theropods and a medium-sized sauropod. A tooth of an ornithocheirid is the first report of a pterosaur from the region. The dinosaur bones and teeth were transported some distance and deposited in a channel lag, associated with less damaged locally derived material such as fern fronds, coprolites, fish teeth and scales, and crocodilian scutes.

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.

Semiaquatic adaptations in a giant predatory dinosaur

Mysterious dinosaur a swimmer? Dinosaurs are often appreciated for their size and oddity. In this regard, the North African carnivorous theropod Spinosaurus, with its huge dorsal sail and a body larger than Tyrannosaurus rex, has long stood out. This species also stands out because of its history. The unfortunate loss of the type specimen during World War II left much of what we know about Spinosaurus to be divined through speculation and reconstruction. Ibrahim et al. now describe new fossils of this unusual species. They conclude it was, at least partly, aquatic, a first for dinosaurs. Science, this issue p. 1613 New fossils of the sail-finned predatory dinosaur Spinosaurus reveal that it lived in and near water. We describe adaptations for a semiaquatic lifestyle in the dinosaur Spinosaurus aegyptiacus. These adaptations include retraction of the fleshy nostrils to a position near the mid-region of the skull and an elongate neck and trunk that shift the center of body mass anterior to the knee joint. Unlike terrestrial theropods, the pelvic girdle is downsized, the hindlimbs are short, and all of the limb bones are solid without an open medullary cavity, for buoyancy control in water. The short, robust femur with hypertrophied flexor attachment and the low, flat-bottomed pedal claws are consistent with aquatic foot-propelled locomotion. Surface striations and bone microstructure suggest that the dorsal “sail” may have been enveloped in skin that functioned primarily for display on land and in water.

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.

Positive Allometry and the Prehistory of Sexual Selection

The function of the exaggerated structures that adorn many fossil vertebrates remains largely unresolved. One recurrent hypothesis is that these elaborated traits had a role in thermoregulation. This orthodoxy persists despite the observation that traits exaggerated to the point of impracticality in extant organisms are almost invariably sexually selected. We use allometric scaling to investigate the role of sexual selection and thermoregulation in the evolution of exaggerated traits of the crested pterosaur Pteranodon longiceps and the sail‐backed eupelycosaurs Dimetrodon and Edaphosaurus. The extraordinarily steep positive allometry of the head crest of Pteranodon rules out all of the current hypotheses for this trait’s main function other than sexual signaling. We also find interspecific patterns of allometry and sexual dimorphism in the sails of Dimetrodon and patterns of elaboration in Edaphosaurus consistent with a sexually selected function. Furthermore, small ancestral, sail‐backed pelycosaurs would have been too small to need adaptations to thermoregulation. Our results question the popular view that the elaborated structures of these fossil species evolved as thermoregulatory organs and provide evidence in support of the hypothesis that Pteranodon crests and eupelycosaur sails are among the earliest and most extreme examples of elaborate sexual signals in the evolution of terrestrial vertebrates.

Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia

Beginning with Bucklands 1824 description of Megalosaurus, the Geological Society of London played a leading role during the 19th century discovery of dinosaurs in Britain. Here we review the societys role and assess the current knowledge of saurischian dinosaurs in the country. Of Britains 108 dinosaur species (excluding nomina nuda and objective synonyms), 32% have been named in the pages of Society publications. Britain has a rich and diverse dinosaur record ranging from the Rhaetian to the Cenomanian, and includes a surprising taxonomic diversity. Alleged Lower and Middle Triassic dinosaurs from Britain are suspect or erroneous. Sauropodomorphs represent all of the major clades and several have their earliest global appearances in the British record (Diplodocoidea, Rebbachisauridae and Titanosauria), implying that this region was biogeographically important for this group. The British theropod record is diverse, and includes the earliest spinosaurids, carcharodontosaurids and coelurosaurs. Although some specimens are represented by near-complete skeletons, much material is fragmentary and indeterminate, and c. 54% of British dinosaur taxa are considered nomina dubia. In part this high number results from the genesis of dinosaur science in Britain and the corresponding obsolescence of supposedly diagnostic characters.

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.

The Lower Oxford Clay: production and preservation of organic matter in the Callovian (Jurassic) of central England

Abstract The Lower Oxford Clay of the English Midlands is a thermally immature, organic-rich mudrock with a rich and well preserved invertebrate and vertebrate fauna. Biological productivity in the water column was high, as inferred from abundant cephalopods and the presence of large predatory marine reptiles and giant plankton-feeding fish. The sea floor was never anoxic but remained mostly dysoxic, resulting in a dysaerobic benthic biofacies. The ‘soupy’ substrate was inhabited by deposit-feeding bivalves, as well as gastropods and arthropods. The skeletons of large vertebrates at times provided ‘islands’ for the attachment of sessile benthos. Aragonite is well preserved, allowing isotopic palaeotemperature estimates of around 15°C for the bottom waters. Abundant pyrite formed within and beneath a shallow zone of bioturbation. At certain horizons early diagenetic concretions formed, preserving the original, pelletal, sediment texture, and three-dimensional fossils. Net sediment accumulation rates were extremely slow, around 1 to 15 mm of compacted sediment per 1000 years; sedimentation must have been episodic. Some diastems are represented by shell-beds, but others are cryptic. Nutrient supply is thought to be mainly from a well vegetated, swampy hinterland. Variations in bottom water oxygenation, sedimentation rate and substrate consistency can be inferred from the subtle facies variations within the Lower Oxford Clay, and controlled the accumulation of organic matter.