Jean Le Loeuff

The earliest known sauropod dinosaur

Sauropods were a very successful group of dinosaurs during the Jurassic and Cretaceous periods, but their earlier history is poorly known. Until now, the earliest reported sauropod bones were from the Early Jurassic, and the only tentative evidence of earlier sauropods was in the form of controversial footprints. Here we report the discovery of an incomplete sauropod skeleton from the Late Triassic period of Thailand, which provides the firstxa0osteological evidence of pre-Jurassic sauropods. This dinosaur is markedly different from prosauropods and substantiates theoretical predictions that there was a fairly long period of sauropod evolution during the Triassic.

Late Maastrichtian continental vertebrates from southwestern France: correlation with marine fauna

Abstract The Cassagnau locality (Marignac-Laspeyres, Haute-Garonne department) has yielded the richest vertebrate assemblage of Late Maastrichtian age in western Europe. Numerous bones can be referred to various fishes, amphibians, chelonians, squamates, crocodiles, dinosaurs and birds, some of which constitute the first Late Maastrichtian occurrences in Europe (a large varanoid lizard, a longirostrine crocodile, an enantiornithine bird) or in Southern France (a titanosaurid dinosaur). The latter discovery shows that at least five dinosaur families were represented in the Late Maastrichtian of western Europe. As for other localities of the French Petites Pyrenees, the age of the Cassagnau locality can be directly constrained by biostratigraphical and biochronological evidence based on associated marine and continental microfauna and microflora; therefore, the assemblages from these localities can be considered as reference assemblages for the continental Late Maastrichtian localities of Southern Europe, the age of which has been much disputed.

Late Cretaceous non-marine vertebrates from southern France: A review of recent finds

Abstract During the last few years, systematic prospections and excavations in the non-marine Campanian andMaastrichtian of southern France, from Provence in the East to the valley of the Garonne in the West, have considerably increased our knowledge of the continental vertebrates (fishes, amphibians, turtles, squamates, crocodilians, pterosaurs, dinosaurs, birds and mammals) from that time interval. A succession of faunal assemblages, corresponding to the Early Campanian, the Late Campanian/Early Maastrichtian and the Late Maastrichtian, can now be recognised, with a marked change in the dinosaur fauna during the Maastrichtian, but no clear evidence of decline during the last million years of the Cretaceous. The biogeographical complexity of the Late Cretaceous vertebrate assemblages from southwestern Europe is underlined.

An Early Cretaceous vertebrate assemblage from the Cabao Formation of NW Libya

Fossil vertebrates from the Cabao Formation discovered in the area of Nalut in northwestern Libya include the hybodont shark Priohybodus , the crocodilian Sarcosuchus , an abelisaurid, a baryonichine spinosaurid and a large sauropod with spatulate teeth. The Cabao Formation may be Hauterivian to Barremian in age, although an earlier Berriasian to Valanginian age cannot be excluded. Its dinosaur assemblage is reminiscent of that of the El Rhaz and Tiouraren formations of Niger and strongly differs from both the Cenomanian assemblages of Morocco and Egypt and the Late Aptian to Albian fauna of Tunisia. Fossil vertebrates may be an important tool to establish the stratigraphical framework of the poorly dated Early Cretaceous continental deposits of Africa.

The first giant dinosaurs: a large sauropod from the Late Triassic of Thailand

Abstract Newly discovered sauropod material from the Upper Triassic of northeastern Thailand reveals that some of the earliest sauropods had already reached a very large size. A 1 m long humerus is within the size range of large Jurassic sauropods such as Camarasaurus and suggests an animal reaching a length of 12 to 15xa0m. It took sauropodomorph dinosaurs some 20 million years to produce giant forms, a rapid size increase when compared with that observed in the evolution of other dinosaurs, such as ornithischians. To cite this article: E.xa0Buffetaut etxa0al., C.xa0R. Palevol 1 (2002) 103–109.

Modified Laminar Bone in Ampelosaurus atacis and Other Titanosaurs (Sauropoda): Implications for Life History and Physiology

Background Long bone histology of the most derived Sauropoda, the Titanosauria suggests that titanosaurian long bone histology differs from the uniform bone histology of basal Sauropoda. Here we describe the long bone histology of the titanosaur Ampelosaurus atacis and compare it to that of basal neosauropods and other titanosaurs to clarify if a special titanosaur bone histology exists. Methodology/Principal Findings Ampelosaurus retains the laminar vascular organization of basal Sauropoda, but throughout most of cortical growth, the scaffolding of the fibrolamellar bone, which usually is laid down as matrix of woven bone, is laid down as parallel-fibered or lamellar bone matrix instead. The remodeling process by secondary osteons is very extensive and overruns the periosteal bone deposition before skeletal maturity is reached. Thus, no EFS is identifiable. Compared to the atypical bone histology of Ampelosaurus, the large titanosaur Alamosaurus shows typical laminar fibrolamellar bone. The titanosaurs Phuwiangosaurus, Lirainosaurus, and Magyarosaurus, although differing in certain features, all show this same low amount or absence of woven bone from the scaffolding of the fibrolamellar bone, indicating a clear reduction in growth rate resulting in a higher bone tissue organization. To describe the peculiar primary cortical bone tissue of Phuwiangosaurus, Ampelosaurus, Lirainosaurus, and Magyarosaurus, we here introduce a new term, “modified laminar bone” (MLB). Conclusions/Significance Importantly, MLB is as yet not known from extant animals. At least in Lirainosaurus and Magyarosaurus the reduction of growth rate indicated by MLB is coupled with a drastic body size reduction and maybe also a reduction in metabolic rate, interpreted as a result of dwarfing on the European islands during the Late Cretaceous. Phuwiangosaurus and Ampelosaurus both show a similar reduction in growth rate but not in body size, possibly indicating also a reduced metabolic rate. The large titanosaur Alamosaurus, on the other hand, retained the plesiomorphic bone histology of basal neosauropods.

Minute theropod eggs and embryo from the Lower Cretaceous of Thailand and the dinosaur-bird transition

We report on very small fossil eggs from the Lower Cretaceous of Thailand, one of them containing a theropod embryo, which display a remarkable mosaic of characters. While the surficial ornamentation is typical of non-avian saurischian dinosaurs, the three-layered prismatic structure of the eggshell is currently known only in extant and fossil eggs associated with birds. These eggs, about the size of a goldfinchs, mirror at the reproductive level the retention of small body size that was paramount in the transition from non-avian theropods to birds. The egg-layer may have been a small feathered theropod similar to those recently found in China.

Romanian late cretaceous dinosaurs: Big dwarfs or small giants?

It has been argued that the Late Cretaceous dinosaurs from Transylvania were affected by dwarfism as a consequence of their evolution in an insular habit. However, several bones from Nopcsas collections housed in London and Budapest shows that some Transylvanian saltasaurids reached lengths of 10–15xa0m. These multi-ton animals can hardly be considered as dwarfs, even by dinosaurian standards. It is suggested here that taphonomical biases, possibly linked to the existence of age-classed communities among sauropod populations, explain why the vast majority of recovered bones are of young individuals.It has been argued that the Late Cretaceous dinosaurs from Transylvania were affected by dwarfism as a consequence of their evolution in an insular habit. However, several bones from Nopcsas collections housed in London and Budapest shows that some Transylvanian saltasaurids reached lengths of 10–15 m. These multi-ton animals can hardly be considered as dwarfs, even by dinosaurian standards. It is suggested here that taphonomical biases, possibly linked to the existence of age-classed communities among sauropod populations, explain why the vast majority of recovered bones are of young individuals.

The first sinamiid fish (Holostei: Halecomorpha) from Southeast Asia (Early Cretaceous of Thailand)

Abstract †Siamamia naga, gen. et sp. nov, is described on the basis of three partly articulated skulls and a collection of isolated ossifications from a continental Early Cretaceous Formation of northeastern Thailand. The new taxon is a †sinamiid halecomorph as demonstrated by the median parietal and other cranial characters. †Sinamiidae is hitherto known by two genera occurring in Early Cretaceous freshwater deposits in China. Although a complete revision of all species within the family is necessary, the Thai material shows characters justifying a new genus. It is the first †sinamiid found outside eastern Asia (South and North Chinese blocks, plus small Central Asian terranes), thus validating the close paleogeographical affinities between mainland Asia and SE Asia in the Early Cretaceous. A preliminary phylogenetic assessment of the new taxon with the data matrix of Grande and Bemis (1998) with the addition of data for †Siamamia and †Tomognathus provides a strict consensus tree similar to the phylogenetic hypothesis of Halecomorphi proposed by these authors, except the basal-most amiids which show a lower resolution in our hypothesis. The †Sinamiidae appear as a monophyletic clade, but the four taxa included in the analysis form a polytomy.

A Jurassic amber deposit in Southern Thailand

Published reports of amber predating the Aptian are rare and mention only amber pieces the size of millimetric marbles. Mid Cretaceous amber records, however, show a dramatic increase in number as well as in the size of the pieces, a phenomenon which is still poorly understood. The discovery of the first Jurassic deposit with comparatively large centimetric sized pieces of amber, in southern Thailand, is significant. Taphonomy and palaeobotany indicate a dense forest surrounding a coastal lake dominated by the resin-producing Agathoxylon tree. Since the palaeoecology of other amber-producing Jurassic and Cretaceous deposits is very similar a new hypothesis needs to be sought to explain the mid Cretaceous amber boom. It is suggested here that it was the result of a geological or taphonomic bias because coastal lacustrine environments are much better preserved after the Aptian on a worldwide scale.