Jean Dejax

A new hominid from the Upper Miocene of Chad, Central Africa

The search for the earliest fossil evidence of the human lineage has been concentrated in East Africa. Here we report the discovery of six hominid specimens from Chad, central Africa, 2,500 km from the East African Rift Valley. The fossils include a nearly complete cranium and fragmentary lower jaws. The associated fauna suggest the fossils are between 6 and 7 million years old. The fossils display a unique mosaic of primitive and derived characters, and constitute a new genus and species of hominid. The distance from the Rift Valley, and the great antiquity of the fossils, suggest that the earliest members of the hominid clade were more widely distributed than has been thought, and that the divergence between the human and chimpanzee lineages was earlier than indicated by most molecular studies.

Un gisement sparnacien exceptionnel à plantes, arthropodes et vertébrés (Éocène basal, MP7): Le Quesnoy (Oise, France)

A new fossil locality is reported from the argiles a lignite du Soisonnais (Early Ypresian, MP7) of the Oise region (France). After the preliminary survey of the flora and the vertebrate and arthropod faunas, we propose a reconstruction of a fluvio-lacustrine palaeoenvironment with a forest, under a warm and wet seasonal climate. This site is outstanding because of the richness, diversity and the state of preservation of the fossils. The present discovery opens a unique window on terrestrial life during the Earliest Eocene.

Vertebrate fossils from Cameroon, West Africa

ABSTRACT Fossil vertebrates discovered in 1986 from Cameroon, West Africa, occur in three different areas in the northern part of the country. Cretaceous rocks northeast of Garoua, in the Babouri-Figuil Basin, yield complete Lepidotes skeletons. Southeast of Garoua, Cretaceous rocks of the Mayo Rey Basin, near Koum, are more clearly terrestrial and contain diverse vertebrates. The Hama Koussou Basin, just north of Garoua, produces fragmentary Lepidotes and dinosaurs. Weathered from a veneer of Pleistocene sediment overlying the latter deposit, the well fossilized remains of Equus, Phacochoerus, and a bovid were recovered.

Un nouveau genre de dinosaure sauropode de la formation des Grès supérieurs (Aptien-Albien) du Laos

The partly-articulated postcranial remains of two sauropod skeletons recently found in Tang Vay (Savannakhet Province, Laos) are assigned to the species Tangvayosaurus hoffeti (nov. gen., nov. sp.). The derived characters present in the new material confirm the presence of titanosaurs in South East Asia at the end of the Early Cretaceous, but are not consistent with its placement within Titanosaurus genus as first done by Hoffet in 1942. All of the material relative to this species is therefore referred to a new genus: Tangvayosaurus. Tangvayosaurus and the Thai genus Phuwiangosaurus have strong affinities and are considered as primitive titanosaurs.

Extraction du pollen inclus dans l'ambre [Sparnacien du Quesnoy (Oise), bassin de Paris] : vers une nouvelle spécialité de la paléo-palynologie

Some amber fragments from Le Quesnoy (Oise) yield pollen, confined in this fossil resin. An extraction method has been devised in order to observe it under light and scanning electron microscopes. This method consists of a partial dissolution of the amber by organic solvents, which softens it and enables dissection of the fragments. The extracted pollen appears to be in an excellent state of preservation. The three-dimensional shape of the pollen grains is well preserved and their cell contents are still present. Thus, this method opens numerous study fields of this peculiar palynoflora. The diagnoses of the morphographic taxa observed, as well as their botanical relationships with modern taxa, can be re-examined. Other developments are explored, such as the study of the cell contents.Abstract Some amber fragments from Le Quesnoy (Oise) yield pollen, confined in this fossil resin. An extraction method has been devised in order to observe it under light and scanning electron microscopes. This method consists of a partial dissolution of the amber by organic solvents, which softens it and enables dissection of the fragments. The extracted pollen appears to be in an excellent state of preservation. The three-dimensional shape of the pollen grains is well preserved and their cell contents are still present. Thus, this method opens numerous study fields of this peculiar palynoflora. The diagnoses of the morphographic taxa observed, as well as their botanical relationships with modern taxa, can be re-examined. Other developments are explored, such as the study of the cell contents.

Le contenu cellulaire du pollen fossilisé dans l'ambre, préservé à l'état organique

The cell contents are still present inside almost every fossil pollen grain embedded in amber of two different origins (Lower Eocene amber from Paris Basin, Tertiary Baltic amber): they are here described after the observation of numerous extracted grains. Some structures are identified, among which probably the nucleus. Because of their confining in this very peculiar fossilization medium, the cell contents were not permineralized but remained somewhat close to the original organic condition, hence offering a field of research about fossil intracellular structure and palaeo-biochemistry, some organic molecules remaining potentially preserved.