Pliocene large-mammal assemblages from northern Chad: sampling and ecological structure

Numerous Pliocene large-mammal assemblages have been discovered in Chad over the last decade. They offer a unique opportunity to understand the settings in which important chapters of Hominid evolution took place in Central Africa. However, it is crucial to first investigate both sampling and taxonomic homogeneity for these Chadian assemblages because they occur over large sectors in a sandy desert that offers virtually no stratigraphic section. Using cluster analysis and ordination techniques, we show that the three Pliocene sectors from Chad are homogeneous and adequate sampling units. Previous stable isotope analyses on these assemblages have indicated that the environment became richer in C(4) plants between approximately 5.3 and 3.5-3 Ma. To test whether this environmental change has affected the structure of palaeo-communities, we assigned body mass, trophic and locomotor eco-variables to mammal species from the three sectors. Statistical analysis shows that the overall ecological structure of the assemblages is not linked with the opening of the plant cover, and eco-variables show no temporal trend from the oldest sector to the youngest. For example, there is no significant change in the relative diversity of grazing and browsing taxa, although mixed feeders are less diversified in the youngest sector than in the preceding one. This pattern apparently does not result from potential biases such as methodological artefacts or taphonomic imprint. Instead, it seems that local heterogeneous environmental factors have played a major role in shaping the ecological spectrum of Chadian mammal palaeo-communities during the Pliocene.     

The earliest modern mongoose (Carnivora, Herpestidae) from Africa (late Miocene of Chad)

We report on the earliest modern mongooses of Africa, from the late Miocene (ca. 7 Ma) of the hominid locality TM 266, Toros-Menalla, Chad. The material is based on fragmentary dentitions of three individuals. The main diagnostic feature of the Chadian species is the great development of the shear in the carnassials, which distinguishes the Chadian specimens from all extant herpestids except Herpestes and Galerella. In comparison with most extinct and extant Herpestes, the species from Toros-Menalla differs by a markedly smaller size and, depending on the species, relatively more elongated carnassials, more transversely elongated M1 and more reduced p4. On the basis of a great morphological similarity and the absence of significant differences, we assign our material to Galerella sanguinea; the Chadian finding therefore represents the earliest appearance of an extant species of Herpestidae. This record ties the first appearance of the genus to a minimum age of ca. 7 Ma, which is consistent with the estimated divergence date of 11.4 Ma known from the literature for the species of Galerella.     

The oldest African fox (Vulpes riffautae n. sp., Canidae, Carnivora) recovered in late Miocene deposits of the Djurab desert, Chad

We report on the oldest fox (Canidae) ever found in Africa. It is dated to 7 Ma based on the degree of evolution of the whole fauna. It belongs to a new species. Its overall size and some morphological characteristics distinguish the Chadian specimen from all the other foxes. The presence of Vulpes and of the genus Eucyon in slightly younger African locality, as well as in southwestern Europe in the late Miocene, may indicate that canids migrated in Europe from Africa through a trans-Mediterranean route.     

The mammal assemblage of the hominid site TM266 (Late Miocene, Chad Basin): ecological structure and paleoenvironmental implications

Characterizing the paleoenvironmental context of the first hominids is a key issue for understanding their behavioral and morphological evolution. The present study aims at reconstructing the paleoenvironment of the TM266 vertebrate assemblage (Toros-Menalla, Northern Chad) that yielded the earliest known hominid Sahelanthropus tchadensis (7 Ma). For the first time, a quantitative analysis is carried out on the fossil mammal assemblage associated with that hominid. Two complementary approaches were applied: (1) the analysis of the relative abundances of taxa and their habitat preferences; and (2) the study of the distribution of taxa within three meaningful ecovariables: locomotion, feeding preferences, and body mass. The resulting taxonomic and paleoecological structures are used to reconstruct the diversity and the relative extent of the habitats in that part of northern Chad seven million years ago. The paleoenvironment was composed of open areas with dry and humid grasslands, prevailing over wooded habitats. Water was also widely available as freshwater bodies and certainly swamps. It appears that the high habitat diversity of the landscape is a common feature among paleoenvironments associated with early hominids.     

The first fossil fungus gardens of Isoptera: oldest evidence of symbiotic termite fungiculture (Miocene, Chad basin)

Higher termites of the subfamily Macrotermitinae (fungus-growing termites) are known to build fungus gardens where a symbiotic fungus (Termitomyces sp.) is cultivated. The fungus grows on a substrate called fungus comb, a structure built with the termites’ own faeces. Here we present the first fossil fungus combs ever found in the world. They were extracted from 7-million-year-old continental sandstone (Chad basin). Fossilized fungus combs have an ovoid morphology with a more or less flattened concave base and a characteristic general alveolar aspect. Under lens, they display a typical millimetre-scale pelletal structure. The latter, as well as the general shape and alveolar aspect, are similar to the morphology of fungus combs from extant fungus-growing termites.     

Design of Polyhydroxyalkanoate (PHA) Microbeads with Tunable Functional Properties and High Biodegradability in Seawater

Journal of Polymers and the Environment - Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) were used to prepare microbeads, with diameter ranging from...