PDM - Metazoan phylogeny and diversification
Metazoan diversification produces new species whose phenotypes diverge at various rates. This diversification in space and time, influenced by environmental factors, including habitat distribution (itself determined partly by paleogeographic changes; see figure below), produces faunas that are more or less distinct and sometimes endemic, and whose composition reflects both the evolutionary and paleobiogeographic history. The team « Metazoan phylogeny and diversification » works on these phenomena through four projects. It includes several vertebrate paleontologists, as well as a few working on mollusks or arthropods.
The research of the PDM team members is developed around 4 themes:
Coordinators: Emmanuel Gheerbrant, Sevket Sen
The "Old World" project studies the origin and evolution of the Old World fauna before, during, and after closure of the Tethys. This project emphasizes field work to produce new data on the metazoan fossil record (morphological descriptions, phylogenetic analyses, etc.), especially on continental vertebrate evolution in their paleoenvironmental and paleogeographic context, through stratigraphic, geodynamic, and sedimentological studies. The studied sites cover most of the Old World, including Arabo-African, European, and Indian provinces. A sub-project concerns the peri-Tethysian roots of the Old World fauna. It studies the great continental endemism centers (biodiversity, evolutionary radiations, paleoenvironments) that composed the peri-Tethysian provinces, such as Africa (excluding Madagascar) and India and the faunal relationships that had become established before closure of the Tethys. A second sub-project studies faunal exchanges, extinctions and evolutionary radiations that followed the collision between Africa and Eurasia about 22 Ma and, to a lesser extent, between India and Eurasia.
Coordinator: Michel Laurin
The second project, "Timing of taxononic and phenotypic diversification", aims at developing new paleontological dating methods for taxa. These methods will rest on detailed stratigraphic data from the fossil record and on the phylogeny of the relevant taxa. These methods will then be used to better date the metazoan tree, with emphasis on mammals (because our group includes several paleomammalogists), but also on other vertebrates, mollusks, and arthropods. This project features biomathematics and computer science components, and will include molecular dating, in both cases through external collaborations. It rests on our established expertise in phylogenetics based on phenotypic characters (the only ones available on long-extinct taxa), which are documented through the morphological data that we produce, partly on fossils that we collect in the field.
Coordinators: Guillaume Billet, Jérémie Bardin and Isabelle Rouget
Having robust phylogenies is essential to many studies of evolutionary biology. However, methods and data used for phylogenetic reconstruction are diverse and their results and interpretations may strongly differ. Whereas molecular data are usually favored for studies on extant taxa, morphological data are critical for reconstructing the phylogenetic relationships of many fossil groups. Yet, morphological variation embrace many aspects that may reveal hard to deal with and to model realistically and adequately for phylogenetic analyses: integration/modularity, ontogeny, polymorphism, multivariate and continuous variation, etc. In order to strengthen and improve phylogenetic inferences made for fossil taxa, this project aims at enhancing analyses of these complex aspects of morphological data with the use of statistical and morphometrical toolkits.
This project gathers researchers from the team wishing to improve their analyses of morphological variation with an aim to reconstruct phylogenies. It will allow implementing novel and common solutions to analog problems in various taxonomic groups. It will take advantage of the team’s solid experience in morphological phylogenetics and its very diverse taxonomic expertise.
Coordinator: Jorge Cubo
The independent acquisitions of mammalian and avian endothemy are major events in vertebrate evolution. These acquisitions are correlated to a large array of anatomical and physiological changes such as the presence of a complete heart partition and a high systemic arterial pressure allowing the efficient elimination of nitrogen compounds produced by a high metabolic rate linked to heat production. The presence of a isolating fur in therapsids, of turbinate bones in Eutherodontia, of a high ∂18Oapatite in dinosaurs inhabiting high paleolatitudes and of a fibrolamellar complex in archosauriforms have been used to infer the presence of endothermy. The aim of this project is to constrain the geological age and the phylogenetic frame of the multiple acquisitions of endothermy in tetrapods.
Quantitative paleohistological methods have been recently developed to infer bone growth rates and resting metabolic rates of extinct tetrapods. Coupled to modern phylogenetic comparative methods such as the Phylogenetic Eigenvector Maps, these paleohistological analyses suggest that endothermy has been acquired independently by Neotherapsida and by the last common ancestor of Prolacerta and birds. Using this approach to analyze a comprehensive sample of extinct tetrapods may shed light on the possible endothermic state of ichthyosaurs and plesiosaurs (as suggested by geochemical data) and will allow testing hypothesis on the evolution of thermometabolism in tetrapods.
Tenured and tenure-track scientists: Ronan Allain (MC MNHN), Véronique Barriel (MC MNHN), Olivier Béthoux (MC MNHN), Guillaume Billet (PR MNHN), Jorge Cubo (PR SU), Emmanuel Gheerbrant (DR CNRS), Nour-Eddine Jalil (PR MNHN), Isabelle Kruta (MC SU), Michel Laurin (DR CNRS), Grégoire Métais (CR CNRS), Isabelle Rouget (PR MNHN).
Béthoux O et al. 2011. At last, a Pennsylvanian stem-stonefly (Plecoptera) discovered. BMC Evolutionary Biology 11: 248.
Cecca F, Rouget I. 2006. Anagenetic evolution of the early Tithonian ammonite genus Semiformiceras tested with cladistic analysis. Palaeontology 49: 1069–1080.
Gheerbrant, E. 2010. Primitive African ungulates ("Condylarthra" and Paenungulata), pp. 563-571. In L. Werdelin, and W. J. Sanders (Eds): Cenozoic Mammals of Africa, The University of California Press, Berkeley, Los Angeles, London.
Gheerbrant, E., and Rage, J.-C. (2006). Paleobiogeography of Africa: How distinct from Gondwana and Laurasia? Palaeogeography, Palaeoclimatology, Palaeoecology 241, 224-246.
Laloy F, Rage J-C, Evans SE, Boistel R, Lenoir N, Laurin M. 2013. A re-interpretation of the Eocene anuran Thaumastosaurus based on microCT examination of a 'mummified' specimen. PLoS ONE 8: 1–11.