Antoine Louchart

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.

Asa issie, aramis and the origin of Australopithecus

The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies. Australopithecus species differ markedly from extant African apes and candidate ancestral hominids such as Ardipithecus, Orrorin and Sahelanthropus. The earliest described Australopithecus species is Au. anamensis, the probable chronospecies ancestor of Au. afarensis. Here we describe newly discovered fossils from the Middle Awash study area that extend the known Au. anamensis range into northeastern Ethiopia. The new fossils are from chronometrically controlled stratigraphic sequences and date to about 4.1–4.2 million years ago. They include diagnostic craniodental remains, the largest hominid canine yet recovered, and the earliest Australopithecus femur. These new fossils are sampled from a woodland context. Temporal and anatomical intermediacy between Ar. ramidus and Au. afarensis suggest a relatively rapid shift from Ardipithecus to Australopithecus in this region of Africa, involving either replacement or accelerated phyletic evolution.

Taphonomic, Avian, and Small-Vertebrate Indicators of Ardipithecus ramidus Habitat

Thousands of vertebrate specimens were systematically collected from the stratigraphic interval containing Ardipithecus ramidus. The carcasses of larger mammals were heavily ravaged by carnivores. Nearly 10,000 small-mammal remains appear to be derived primarily from decomposed owl pellets. The rich avifauna includes at least 29 species, mostly nonaquatic forms. Modern analogs of the most abundant birds and of a variety of rodents are associated with mesic woodland environments distant from large water bodies. These findings support inferences from associated geological, isotopic, invertebrate, and large-vertebrate assemblages. The combined results suggest that Ar. ramidus occupied a wooded Pliocene habitat.

Hummingbird with modern feathering: an exceptionally well-preserved Oligocene fossil from southern France.

Hummingbirds (Trochilidae) today have an exclusively New World distribution, but their pre-Pleistocene fossil record comes from Europe only. In this study, we describe an exceptionally preserved fossil hummingbird from the early Oligocene of southeastern France. The specimen is articulated, with a completely preserved beak and feathering. Osteological characters allow to identify it as Eurotrochilus sp. This genus is a stem group representative of Trochilidae and was recently described from the early Oligocene of southern Germany. The new fossil reveals that these European Trochilidae were remarkably modern in size, skeletal proportions and the shape of the wing, tail and beak and hyoid bones. These features confirm the early acquisition of the abilities of hovering and nectarivory in hummingbirds, probably before the Oligocene. In several morphological characteristics, they resemble members of the ‘true hummingbirds’ (subfamily Trochilinae) and differ from hermits (Phaethornithinae). These features, which include a short and square tail and a moderately long, almost straight beak, appear to be primitive within the family Trochilidae.

Fossil birds of the Kibish Formation

The Kibish Formation has yielded a small collection of bird fossils, which are identified here as belonging to five species in four different families: Pelecanidae (pelicans), Anhingidae (darters), Ardeidae (herons) and Phasianidae (gamefowl). Two species of pelicans are identified: Pelecanus cf. P. onocrotalus, and P. aff. P. rufescens. The darter is referrable to Anhinga melanogaster. The heron is identifiable as Ardea sp., and the gamefowl as Numidinae indet. (guineafowl). Pelecanus cf. P. onocrotalus is represented by, among other remains, a well-preserved partial skull. Four of the birds are thus referrable to extant taxa that provide some paleoenvironmental clues for Member I of the Kibish Formation. The two species of pelican, the darter, and the heron indicate the presence of local freshwater bodies, a lake or a slow river, supporting resources of fish. The guineafowl is poorly informative ecologically, but probably excludes the notion that the local terrestrial landscape was treeless.

Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the "last" toothed birds

BackgroundThe dentitions of extinct organisms can provide pivotal information regarding their phylogenetic position, as well as paleobiology, diet, development, and growth. Extant birds are edentulous (toothless), but their closest relatives among stem birds, the Cretaceous Hesperornithiformes and Ichthyornithiformes, retained teeth. Despite their significant phylogenetic position immediately outside the avian crown group, the dentitions of these taxa have never been studied in detail. To obtain new insight into the biology of these ‘last’ toothed birds, we use cutting-edge visualisation techniques to describe their dentitions at unprecedented levels of detail, in particular propagation phase contrast x-ray synchrotron microtomography at high-resolution.ResultsAmong other characteristics of tooth shape, growth, attachment, implantation, replacement, and dental tissue microstructures, revealed by these analyses, we find that tooth morphology and ornamentation differ greatly between the Hesperornithiformes and Ichthyornithiformes. We also highlight the first Old World, and youngest record of the major Mesozoic clade Ichthyornithiformes. Both taxa exhibit extremely thin and simple enamel. The extension rate of Hesperornis tooth dentine appears relatively high compared to non-avian dinosaurs. Root attachment is found for the first time to be fully thecodont via gomphosis in both taxa, but in Hesperornis secondary evolution led to teeth implantation in a groove, at least locally without a periodontal ligament. Dental replacement is shown to be lingual via a resorption pit in the root, in both taxa.ConclusionsOur results allow comparison with other archosaurs and also mammals, with implications regarding dental character evolution across amniotes. Some dental features of the ‘last’ toothed birds can be interpreted as functional adaptations related to diet and mode of predation, while others appear to be products of their peculiar phylogenetic heritage. The autapomorphic Hesperornis groove might have favoured firmer root attachment. These observations highlight complexity in the evolutionary history of tooth reduction in the avian lineage and also clarify alleged avian dental characteristics in the frame of a long-standing debate on bird origins. Finally, new hypotheses emerge that will possibly be tested by further analyses of avian teeth, for instance regarding dental replacement rates, or simplification and thinning of enamel throughout the course of early avian evolution.

The dodo was not so slim: leg dimensions and scaling to body mass.

Recently Angst et al. (2011) proposed a new mean bodymass estimate for the dodo (Raphus cucullatus), ofMauritius Island, 10.2 kg, which is at the lower end ofprevious estimated intervals such as Kitcheners (1993). Wequestion both their methods and results and propose arevised estimated interval.Angst et al. (2011) used the lengths of the hindlimb threelong bones and regression equations, based on a sample ofliving birds, between these lengths and body mass (Zefferet al. 2003). But contra Angst et al. (2011), tibiotarsus andtarsometatarsus lengths cannot be used to estimate bodymass. This is because different bird species of the sameweight can show considerable differences in the lengths ofthese two bones, hence in leg length, across families andorders, generally in adaptation to particular locomotoryhabits (terrestriality, running, perching, aeriality, swimming,wading …), mode of predation (e.g. ornithophagy) andothers, with particular causes in insular contexts (e.g.Campbell and Marcus 1992; Zeffer et al. 2003; Louchart2005 and references therein). This is visible in the relativelylow R

Structure and Growth Pattern of Pseudoteeth in Pelagornis mauretanicus (Aves, Odontopterygiformes, Pelagornithidae)

The extinct Odontopterygiformes are the sole birds known to possess strong and sharp bony pseudoteeth, the shape and location of which are closely mimetic of real teeth. The structure of the pseudoteeth is investigated here in a late Pliocene/early Pleistocene species, Pelagornis mauretanicus, using X-ray microtomography and thin sections. The results are interpreted with regard to the pseudotooth mode of growth, and have implications concerning aspects of Pelagornis ecology. The larger pseudoteeth are hollow and approximately cone-shaped, and the smaller ones are rostro-caudally constricted. The walls of pseudoteeth are composed of bone tissue of the fibro-lamellar type, which is intensively remodeled by Haversian substitution. The jaw bones display the same structure as the pseudoteeth, but their vascular canals are oriented parallel to the long axis of the bones, whereas they are perpendicular to this direction in the pseudoteeth. There is no hiatus or evidence of a fusion between the pseudoteeth and the jaw bones. Two possible models for pseudotooth growth are derived from the histological data. The most plausible model is that pseudotooth growth began after the completion of jaw bone growth, as a simple local protraction of periosteal osteogenic activity. Pseudotooth development thus occurred relatively late during ontogeny. The highly vascularized structure and the relative abundance of parallel-fibered bone tissue in the pseudoteeth suggest poor mechanical capabilities. The pseudoteeth were most likely covered and protected by the hardened, keratinized rhamphotheca in the adult during life. The late development of the pseudoteeth would involve a similarly late and/or partial hardening of the rhamphotheca, as displayed by extant Anseriformes, Apterygiformes and some Charadriiformes. This would add support to the hypothesis of a close phylogenetic relationship between Odontopterygiformes and Anseriformes. The late maturation of the Pelagornis feeding apparatus, and hence the delayed capability for efficient prey catching, suggests that Pelagornis was altricial.

L'avifaune de Dursunlu, Turquie, Pléistocène inférieur: climat, environnement et biogéographie

Abstract The Lower Pleistocene site of Dursunlu, southern Anatolia, provided a rich, mainly aquatic avifauna, with a majority of extant forms. These indicate an open, steppic environment and a Mediterranean climate, both similar to those of todays Anatolia. This region partially allowed—like all the Mediterranean Basin—northern species (not trans-Saharian migrants) to retire southwards during glaciations, while keeping the Mediterranean species (mainly sedentary).

Biogeographic and paleoenvironmental implications of a new woodpecker species (Aves, Picidae) from the early Pliocene of South Africa

ABSTRACT A fragmentary coracoid as well as isolated ulnae, carpometacarpi, and tarsometatarsi from the Varswater Formation at Langebaanweg, South Africa (early Pliocene), can be assigned to a new genus and species of true woodpecker (Picidae, Picinae), Australopicus nelsonmandelai, gen. et sp. nov. The new taxon is the first documented pre-Pleistocene record of woodpeckers from the entire African continent and it is clearly distinct from the three extant lineages of Picinae that are endemic to sub-Saharan Africa, i.e., Campethera-Geocolaptes, Dendropicos, and Dendrocopos obsoletus. Our phylogenetic analysis shows that the new taxon forms a clade with the extant woodpecker genera Celeus and Dryocopus, which do not occur in Africa, but in the Americas and Eurasia. The new taxon represents a previously unknown fourth lineage of African woodpeckers of Eurasian origin that probably became isolated on the African continent as a result of environmental changes during the Miocene. Evidence for an arboreal true woodpecker in the fossil record strongly supports previous hypotheses regarding the presence of riverine forests at Langebaanweg during the early Pliocene.