Peter M. Galton

ANATOMY AND SYSTEMATICS OF THE PROSAUROPOD DINOSAUR THECODONTOSAURUS ANTIQUUS FROM THE UPPER TRIASSIC OF SOUTHWEST ENGLAND

Abstract Re-examination of the surviving specimens of Thecodontosaurus antiquus indicates that this plesiomorphic sauropodomorph can be diagnosed on the basis of elongate basipterygoid processes, a relatively short dentary, and a squared posterior process of the ilium. Although much of the original topotype material found in the 1830s in Bristol, England, has now been lost, some 245 specimens remain. These indicate a small, gracile prosauropod, up to 2.5 m in length, distinguished primarily on the absence of derived characters seen in other prosauropods. Although attempts were formerly made to subdivide the Bristol specimens into several dinosaurian, and other, taxa, most appear to pertain to the prosauropod Thecodontosaurus antiquus. The specimens do indicate a clear separation into two morphs, a gracile and a robust form, presumably evidence of sexual dimorphism. A juvenile Thecodontosaurus sp. from South Wales may belong to the same species. A cladistic analysis indicates that Prosauropoda is probably a clade, rather than a series of outgroups to Sauropoda, but support for this conclusion is weak. Echoing other recent cladistic analyses, stronger support is found for the existence of a clade Sauropodomorpha, made up from Prosauropoda + Sauropoda, for the clade Sauropoda itself, and for the clade Eusauropoda within Sauropoda.

Dryosaurus, a hypsilophodontid dinosaur from the upper jurassic of north America and Africa postcranial skeleton

KurzfassungEs wird eine vollständig illustrierte Beschreibung der postcranialen Anatomie des zur Familie der Hypsilophodontidae gestellten OrnithischiersDryosaurus altus (Marsh 1878) aus der nord-amerikanischen Morrison-Formation gegeben, der vermutlich artgleich mitDysalotosaurus lettowvorbecki (Virchow 1919) aus dem Kimmeridigium der ostafrikanischen Tendaguru-Formation ist. (Janensch 1950 und Huene 1956 hatten die beiden damais unterschiedenen Gattungen der Familie der Camptosauridae zu-geordnet. Galton hat schon 1977Dysalotosaurus mitDryosaurus synonymisiert.) Der genaue anatomische Vergleich der beiden Arten läßt nur geringe, im Bereich der Variabilität liegende Unterschiede erkennen. Es ist der im Rahmen der Wirbeltierpaläontologie bisher sicherste Nachweis spezifischer Übereinstimmung, der auf eine Landverbindung zwischen dem nördlichen Laurasia und dem südlichen Gondwana zu Beginn des oberen Oberjuras schließen läßt. Sie wird auf dem Wege über das heutige Mittel - und über Süd - Amerika vermutet.AbstractA well illustrated description is provided of the postcranial anatomy of the hypsilopho-dontid dinosaurDryosaurus altus (Marsh) (Reptilia: Ornithopoda) from the Upper Jurassic of western U.S.A. Detailed comparisons with all elements of the postcranial skeleton ofDryosaurus lettowvorbecki (Virchow) from the Upper Jurassic of Tanzania, East Africa show that these two species are very similar and border on being conspecific. This close similarity provides important evidence for the existence of a land connection between northern Laurasia and southern Gondwana sometime during the early Late Jurassic.

Triassic-Jurassic Tetrapod Extinctions: Are They Real?

Terrestrial vertebrate fossils show that part of the Newark supergroup of the eastern United States, all of the Glen Canyon group of the southwestern United States, and the Upper Stormberg group of southern Africa are Early Jurassic. This new correlation demonstrates that the supposed widespread tetrapod extinction at the Triassic-Jurassic boundary is an artifact of spurious correlation.

Fabrosauridae, the basal family of ornithischian dinosaurs (Reptilia: Ornithopoda)

In fabrosaurids the upper jaw is flat and the lower jaw is slender so the ’cheek’ teeth are marginal and not inset as is the case in all other ornithischian dinosaurs. The ’cheek’ teeth of fabrosaurids have anteroposteriorly expanded crowns but lack wear surfaces formed by tooth to tooth contact. Two genera are recognized from the Triassic-Jurassic boundary of Lesotho with good material previously referred toFabrosaurus as a new genus that represents the most conservative ornithopod described to date. The anatomy ofNanosaurus (Upper Jurassic, U.S.A.) andEchinodon (Jurassic-Cretaceous boundary, England) is redescribed; in both genera the tooth bearing bone of the lower jaw is deepened posteriorly and inEchinodon there is a true canine tooth in the upper jaw.ZusammenfassungBei den Fabrosauridae ist der Oberkiefer flach und der Unterkiefer schlank gebaut, so daß die »Backenzähne« randlich stehen und nicht wie bei allen anderen Ornithischiern eingelassen sind. Die »Backenzähne« haben in der Längsrichtung gestreckte Kronen, aber keine durch Zahnkontakt gebildete Abkauflächen. Das von der Trias-Jura-Grenze in Lesotho (= Basutoland) bisher alsFabrosaurus beschriebene Material umfaßt eine weitere Gattung(Lesothosaurus n. gen.), welche den altertümlichsten bisher bekannten Ornithopoden darstellt. Die Anatomie vonNanosaurus (Oberjura U.S.A.) undEchinodon (Jura-Kreide-Grenze, England) wird neu beschrieben. Der zahntragende Unterkieferknochen beider Gattungen ist rückwärts eingetieft, während sich im Oberkiefer vonEchinodon außerdem ein richtiger Eckzahn findet.

Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America

The extremes of dinosaur body size have long fascinated scientists. The smallest (<1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.

Braincase of Enaliornis, an Early Cretaceous bird from England

ABSTRACT The braincase of the Early Cretaceous bird Enaliornis is indicative of a primitive avian brain with a relatively large medulla oblongata, a small cerebellum, small cerebral hemispheres broadly separated from the labyrinth, and a strong basilordotic bend of the whole brain, the latter being characteristic of an airencephalic skull. The reduction of the dorsal pneumatic recess, the large size of the auricular fossa, and possibly the lack of interfoliar ridges on the roof of the cerebellar fossa suggest diving habits and thus support the association of the braincases with the type tarsometatarsus of Enaliornis. The braincase of Enaliornis is most similar to those of Hesperornis, Phaethon, Diomedeidae and Fregata. Most of the similarities to these taxa are primitive for birds.

Were non-avian theropod dinosaurs able to swim? Supportive evidence from an Early Cretaceous trackway, Cameros Basin (La Rioja, Spain)

A fundamental question remaining unanswered in dinosaur behavior is whether they had the ability to swim. We report the discovery of an exceptional swimming dinosaur trackway, with 12 consecutive footprints, in lacustrine nearshore sediment from the Early Cretaceous Cameros Basin, La Rioja, Spain. The singular morphology of these footprints strongly suggests a fl oating animal clawing the sediment as it swam. Diagnostic traits of theropod dinosaur footprints are identifi able in these peculiar elongated S-shaped ichnites. Paleoenvironmental reconstruction indicates an upper shoreface setting with a maximum water depth of ~3 m, substantiating the swimming hypothesis. Ichnological analysis of the trackway shows that this theropod used a pelvic paddle motion, similar to that of modern bipeds, and swam with amplifi ed asymmetrical walking movements to maintain direction into a leftward water current. After recent hints of swimming dinosaurs, this new evidence persuasively demonstrates that some non-avian theropod dinosaurs were swimmers.

OnStaurikosaums pricei, an early saurischian dinosaur from the Triassic of Brazil, with notes on the Herrerasauridae and Poposauridae

The anatomy of the saurischian dinosaurStaurikosaums pricei Colbert from the Santa Maria Formation (Middle or Upper Triassic) of Rio do Sul, Brazil is redescribed.Staurikosaurus has 9 (or possibly 10) short cervicals, 15 dorsals and 2 sacral vertebrae, a modified brachyiliac pelvic girdle and an elongate hindlimb with the tibia longer than the femur.The new family Staurikosauridae is erected, the Herrerasauridae is redefined, and both families are considered to be Saurischia incertae sedis. The distal part of the “femur” ofPoposaurus gracilis Mehl (Upper Triassic, North America) is the ventral part of the pubes with a footed distal end but, because some members of the Poposauridae have an imperforate acetabulum, this family is transferred from the Saurischia (Theropoda, Carnosauria) to the Thecodontia (Pseudosuchia).ZusammenfassungDie Anatomie des SaurischiersStaurikosaurus pricei Colbert aus der mittel- oder obertriassischen Santa-Maria-Formation von Rio do Sul in Brasilien wird neu beschrieben: 9 oder 10 kurze Halswirbel, 15 Rücken- und zwei Sakralwirbel, modifiziertes Becken mit kurzem Ilium, lange Hinterextremitäten, Tibia länger als Femur. Begründung von Staurikosauridae nova fam., genauere Definition der Herrerasauridae. Beide Familien sind Saurisdiia incertae sedis. Der distale Teil des »Femurs« vonPoposaurus gracilis Mehl (Obere Trias, Nordamerika) ist der ventrale Teil des distalen Pubis-Endes. Wegen des imperforaten Acetabulums einiger Vertreter der Poposauridae wird diese Familie nicht mehr wie bisher den Saurisdiia (Theropoda, Carnosauria), sondern den Thecodontia (Pseudosuchia) zugerechnet.

Juveniles of the stegosaurian dinosaur Stegosaurus from the Upper Jurassic of North America

ABSTRACT Two partial skeletons of juvenile individuals of Stegosaurus with estimated body lengths of about 1.5 m (5 ft) and 2.6 m (8.5 ft) are described from the Morrison Formation (Upper Jurassic) of Utah and Wyoming. These juveniles differ from adults in the absence of fusion in composite bones (sacrum, scapulocoracoid, tibia–fibula–astragalus–calcaneum), the smoothness of the surface of the bones, the smaller size of ridges for muscular attachment, a proportionally more slender and elongate scapula, the relatively small size of the olecranon process of the ulna and the head of the femur, and the possible absence of dermal plates (but tail spines were present). Apart from the ratios of the length of the femur to those of the humerus and ilium, and the form of the scapula, ilium and fibula, the bones of juvenile individuals of Stegosaurus are very similar to those of juvenile individuals of the stegosaur Kentrosaurus (Upper Jurassic, East Africa). A probable sexual dimorphism in the sacrum with either fo...

On the anatomy and relationships ofEfraasia diagnostica (Huene) n. gen., a prosauropod dinosaur (Reptilia: Saurischia) from the Upper Triassic of Germany

Palaeosaurus (?) diagnosticusHuene from the Stubensandstone (Upper Triassic, Norian) of Nordwürttemberg, Germany is made the type species of a new genus of prosauropod dinosaurEfraasia, which is referred to the family Anchisauridae. The anatomy ofEfraasia diagnostica is conservative and it was an ideal ancestor for the later and more specializedAnchisaurus polyzelus of North America. The slenderness of the manus and pes ofEfraasia andAnchisaurus is matched amongst prosauropods only by the feet ofGyposaurus capensis andThecodontosaurus antiquus. Staurikosaurus priceiColbert from the Upper Triassic of Brazil is probably a very primitive theropod dinosaur.ZusammenfassungPalaeosaurus (?) diagnosticusHuene aus dem Stubensandstein (Obere Trias, Norium) von Nordwürttemberg wird zur Typusart der neuen Prosauropoden-GattungEfraasia erhoben, die der Familie Anchisauridae zugeordnet wird. Die Anatomie vonEfraasia diagnostica zeigt altertümliche Züge und weist die Art als idealen Vorfahren des jüngeren und stärker spezialisiertenAnchisaurus polyzelus von Nordamerika aus. Der schwache Knochenbau von Hand und Fuß vonEfraasia läßt sich unter den Prosauropoden nur mit dem Fußskelett vonGyposaurus capensis undThecodontosaurus antiquus vergleichen.Staurikosaurus priceiColbert aus der Obertrias Brasiliens ist wahrscheinlich ein sehr primitiver Theropode.