Extant species of Muridae occupy a wide array of habitats and have diverse dietary habits. Consequently, their dental microwear patterns represent a potential clue to better understand the paleoecology of their extinct relatives, which are abundant in many Old World Neogene localities. In this study, dental microwear is investigated for specimens of 17 extant species of murine and deomyine rodents in order to test the reliability of this method and infer dietary preferences on the fossil species Saïdomys afarensis. This extinct form comes from a mid-Pliocene site (AL 327) located at the Hadar Formation (Ethiopia) known to have delivered many hominid specimens of Australopithecus afarensis. A significant correlation between microwear patterns and diet is detected. Thus, grass, fruit, and insect eaters display, respectively, high amounts of fine scratches, wide scratches, and large pits. Moreover, some aspects of the paleoecology of S. afarensis, including feeding habits, could be assessed in regard to its dental microwear pattern. Indeed, it probably had feeding habits similar to that of living grass eaters. These results concur with the presence of open to woodland areas covered by an herbaceous vegetal layer, including monocotyledons, in the vicinity of this mid-Pliocene locality.

No abstract

African mole-rats are fossorial rodents that consist of five chisel-tooth digging genera (Heterocephalus, Heliophobius, Georychus, Fukomys, and Cryptomys) and one scratch digger (Bathyergus). They are characterized by striking physiological, morphological, and behavioral adaptations intimately related to their subterranean life. The influence of their mode of life in shaping the cranial morphology has yet to be evaluated in comparison to other Ctenohystrica, especially fossorial genera, which include the subterranean genera Spalacopus and Ctenomys. In our study, we seek to determine to what extent subterranean life affects the morphofunctional properties of the skull among fossorial ctenohystricans. 3D geometric morphometric analyses were performed on 277 skulls, encompassing 63 genera of Ctenohystrica, and complemented by biomechanical studies. African mole-rats and other subterranean Ctenohystrica, especially chisel-tooth diggers, have a short snout, a wide cranium with enlarged zygomatic arches, and a strongly hystricognathous mandible. Even if convergences are also manifest between most fossorial Ctenohystrica, subterranean rodents departed from the main ctenohystrican allometric trends in having a skull shape less sizedependent, but under stronger directional selection with intense digging activity as a major constraint. African mole-rats, notably chisel-tooth diggers, show important mechanical advantage for the temporalis muscles favoring higher forces at the bite point, while mechanical advantage of the superficial masseter muscles is lower compared to other Ctenohystrica. If subterranean species can be clearly discriminated based on their skull morphology, the intrinsic mosaic of anatomical characters of each genus (e.g., skull, teeth, and muscles) can be only understood in the light of their ecology and evolutionary history.

nvasions and anthropogenic disturbances challenge species with rapid environmental changes. Understanding how organisms respond to these changes is of major concern for the future of biodiversity. The house mouse on a Sub-Antarctic island (Guillou Island, Kerguelen Archipelago) had to face such challenges twice: first when invading the island two centuries ago; and nowadays when coping with an in-depth remodeling of its habitat due to a cohort of anthropogenic changes. Morphometric and biomechanical results show that the initial invasion triggered the evolution of a jaw shape adapted to the local food resources. Contemporary changes are also associated to changes in jaw morphology, but are not directly functionally relevant. Here, a complex response integrating feeding behaviour, investment in feeding structure, and degree of mineralization, may provide the mice with a better tool to benefit of wider resources utilization and/or better cope with intra-specific competition in a changing habitat. These Sub-Antarctic mice exemplify that success of invasive species rely on the capacity of facing rapidly varying environments through integrated, multi-faceted responses involving behaviour to morphology through life-history traits

Contrary to their reptilian ancestors, which had numerous dental generations, mammals are known to usually develop only two generations of teeth. However, a few mammal species have acquired the ability to continuously replace their dentition by the constant addition of supernumerary teeth moving secondarily toward the front of the jaw. The resulting treadmill-like replacement is thus horizontal, and differs completely from the vertical dental succession of other mammals and their extinct relatives. Despite the developmental implications and prospects regarding the origin of supernumerary teeth, this striking innovation remains poorly documented. Here we report another case of continuous dental replacement in an African rodent, Heliophobius argenteocinereus , which combines this dental system with the progressive eruption of high-crowned teeth. The escalator-like mechanism of Heliophobius constitutes an original adaptation to hyper-chisel tooth digging involving high dental wear. Comparisons between Heliophobius and the few mammals that convergently acquired continuous dental replacement reveal that shared inherited traits, including dental mesial drift, delayed eruption, and supernumerary molars, comprise essential prerequisites to setting up this dental mechanism. Interestingly, these dental traits are present to a lesser extent in humans but are absent in mouse, the usual biological model. Consequently, Heliophobius represents a suitable model to investigate the molecular processes leading to the development of supernumerary teeth in mammals, and the accurate description of these processes could be a significant advance for further applications in humans, such as the regeneration of dental tissues.

Recent fossil discoveries have demonstrated that Africa and Asia were epicentres for the origin and/or early diversification of the major living primate lineages, including both anthropoids (monkeys, apes and humans) and crown strepsirhine primates (lemurs, lorises and galagos). Competing hypotheses favouring either an African or Asian origin for anthropoids rank among the most hotly contested issues in paleoprimatology. The Afrocentric model for anthropoid origins rests heavily on the .45 Myr old fossil Algeripithecus minutus from Algeria, which is widely acknowledged to be one of the oldest known anthropoids. However, the phylogenetic position of Algeripithecus with respect to other primates has been tenuous because of the highly fragmentary fossils that have documented this primate until now. Recently recovered and more nearly complete fossils of Algeripithecus and contemporaneous relatives reveal that they are not anthropoids. New data support the idea that Algeripithecus and its sister genus Azibius are the earliest offshoots of an AfroArabian strepsirhine clade that embraces extant toothcombed primates and their fossil relatives. Azibius exhibits anatomical evidence for nocturnality. Algeripithecus has a long, thin and forwardly inclined lower canine alveolus, a feature that is entirely compatible with the long and procumbent lower canine included in the toothcomb of crown strepsirhines. These results strengthen an ancient African origin for crown strepsirhines and, in turn, strongly challenge the role of Africa as the ancestral homeland for anthropoids.

Investigating life history traits in mammals is crucial to understand their survival in changing environments. However, these parameters are hard to estimate in a macroevolutionary context. Here we show that the use of dental ontogenetic parameters can provide clues to better understand the adaptive nature of phenotypic traits in extinct species such as South American notoungulates. This recently extinct order of mammals evolved in a context of important geological, climatic, and environmental variations. Interestingly, notoungulates were mostly herbivorous and acquired highcrowned teeth very early in their evolutionary history. We focused on the variations in crown height, dental eruption pattern, and associated body mass of 69 notoungulate taxa, placed in their phylogenetic and geological contexts. We showed that notoungulates evolved higher crowns several times between 45 and 20 Ma, independently of the variation in body mass. Interestingly, the independent acquisitions of ever-growing teeth were systematically accompanied by eruption of molars faster than permanent premolars. These repeated associations of dental innovations have never been documented for other mammals and raise questions on their significance and causal relationships. We suggest that these correlated changes could originate from ontogenetic adjustments favored by structural constraints, and may indicate accelerated life histories. Complementarily, these more durable and efficient dentitions could be selected to cope with important ingestions of abrasive particles in the context of intensified volcanism and increasing aridity. This study demonstrates that assessing both life history and ecological traits allows a better knowledge of the specializations of extinct mammals that evolved under strong environmental constraints. dental ontogeny | hypsodonty | abrasion | notoungulates | South America

In paleontology, many changes affecting morphology, such as tooth shape in mammals, are interpreted as ecological adaptations that reflect important selective events. Despite continuing studies, the identification of the genetic bases and key ecological drivers of specific mammalian dental morphologies remains elusive. Here we focus on the genetic and functional bases of stephanodonty, a pattern characterized by longitudinal crests on molars that arose in parallel during the diversification of murine rodents. We find that overexpression of Eda or Edar is sufficient to produce the longitudinal crests defining stephanodonty in transgenic laboratory mice. Whereas our dental microwear analyses show that stephanodonty likely represents an adaptation to highly fibrous diet, the initial and parallel appearance of stephanodonty may have been facilitated by developmental processes, without being necessarily under positive selection. This study demonstrates how combining development and function can help to evaluate adaptive scenarios in the evolution of new morphologies.