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.

No abstract

Extinct organisms provide crucial information about the origin and time of origination of extant groups. The importance of morphological phylogenetics for rigorously dating the tree of life is now widely recognized and has been revitalized by methodological developments such as the application of tip-dating Bayesian approaches. Traditionally, molecular clocks have been node calibrated. However, node-calibrations are often unsatisfactory because they do not allow the fossil age to inform about phylogenetic hypothesis. The introduction of tipcalibrations allow fossil species to be included alongside their living relatives, and the absence of molecular sequence data for these taxa remedied by supplementing the sequence alignments for living taxa with phenotype character matrices for both living and fossil taxa.So, only phylogenetic analyses that take into account morphological characters can incorporate both fossil and extant species. Herein we present an unprecedented morphological dataset for a vast group of glirid rodents, to which different phylogenetic methodologies have been applied. We have compared the tree topologies resulting from 2 traditional parsimony and Bayesian phylogenetic approaches and calculate stratigraphic congruence indices for each. Bayesian tip-dated clock methods seem to outperform parsimony with our dataset. The strict consensus tree recovered by tip-dating invalidates the classic classification and allow to propose dates for the divergence and origin of the different clades.

Owing to an editorial oversight, the sentence in the second column of page 150 that reads 'Lower c and the lower and upper premolars each have three pulp canals and two roots' is in error. Instead, it should read 'Lower and upper premolars each have three pulp canals and two roots'.