Georges Demathieu

Problems in discrimination of tridactyl dinosaur footprints, exemplified by the Hettangian trackways, the causses, France

Numerous tridactyl dinosaur footprints have been discovered in the Lower Jurassic (Hettangian) of the Causses, France. They exhibit the usual Grallator‐like morphology in which differences seem to be more a result of normal intraspecific variability than of inherent differences between skeletons. However, such subjective conclusions beg an analytical confirmation, which was the principal objective of this study. For more reliable shape determinations, typical specimens from well‐preserved footprint ichnofaunas of the Connecticut Valley (USA) were used. Statistical methods are necessary to verify the homogeneity of such footprint populations. Determinations of the variability, confidence interval for the mean, and ratios between length characters are particularly important in reducing the influence of the size of each print. By this method, the ichnospecies Anomoepus intermedius, Eubrontes giganteus, and Grallator sillimani are statistically distinct; the equally distinct new ichnospecies from Saint‐Leons ...

A new approach to the discrimination of chirotherioid ichnospecies by means of multivariate statistics. Triassic eastern border of the French Massif Central

Abstract Rotated principal components analysis is used to clarify the morphology and taxonomy of Chirotheriod footprints. It reveals that the best characteristic for separating out the footprints is a combination of increasing size of the prints and increasing spread of the digits. Reasonably coherent neighbourhoods of the traditionally recognised species are displayed by the component scores. The resulting ordination of the species reflects an evolutionary trend through the Triassic.

Enigmatic ichnites in the middle triassic of Southern Spain

In southern Spain, within the Chiclana de Segura Formation of red detrital fades, enigmatic structures were found whose origins are discussed here. Each structure is composed of the union of elongated traces, two laterals and a shorter central one. All are concave epireliefs at the top of a sandstone bed whose age is assumed to be Ladinian (Triassic). The sediments formed within a fluvial environment. We describe these imprints, their structures and measurements, and discuss their orientations and associations. The traces probably have an organic origin, and are most likely tracks made by a vertebrate, possibly an archosaur, although no osseous remains have been found to confirm this interpretation.