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Last update : 27.01.2013



« Révision du genre Democricetodon (Mammalia, Rodentia, Cricetinae) et dynamique des faunes de rongeurs du Néogène d'Europe occidentale : évolution, paléobiodiversité et paléobiogéographie »
«Revision of the genus Democricetodon (Mammalia, Rodentia, Cricetinae) and neogene rodent faunas dynamic in western Europe  : evolution, paleobiodiversity and paleobiogéography»


Defended at the University "Claude Bernard" Lyon 1 - 06-17-2003

Institute "PaléoEnvironnements et PaléobioSphère" - UMR 5125 PEPS


Serge LEGENDRE PhD superviser Dr. CNRS researcher Institute "Paleoenvironment & Paleobiosphere" UMR CNRS 5125 - University Lyon I
Pierre MEIN PhD superviser Dr. lecturer  Institute "Paleoenvironment & Paleobiosphere" UMR CNRS 5125 - University Lyon I
Jean-Pierre AGUILAR reviewer Dr. CNRS researcher Institute of Evolutionary Sciences UMR CNRS 5554 - Univ. Montpellier II
Jordi AGUSTI reviewer Professor Institute de Paleoecologia Humana - University of Tarragona
Gilles ESCARGUEL Dr. lecturer Institute "Paleoenvironment & Paleobiosphere" UMR CNRS 5125 - University Lyon I
Christophe LECUYER president of the jury Dr. CNRS researcher Institute "Paleoenvironment & Paleobiosphere" UMR CNRS 5125 - University Lyon I
Sevket SEN Dr. CNRS researcher Institute "Paléobiodiversité: Histoire et dynamique" UMR CNRS 5143 - MNHN

During  the  Miocene  (-25 to -5My) in Europe,  climatic  changes imply  modifications in rodent communities (Mammalia), especially in Cricetids. A systematic revision of the genus Democricetodon  allows to propose a phylogeny,  using  an  extant population of Oryzomys as a model of morphological variability.
A  molars  contour study, using a Fourrier analysis,  from  three different lineages of the genus Megacricetodon in three different European regions shows non-synchronous evolution  accelerations.
Both  genera  emphasize the geographic and  climatic  impacts  on rodent faunas dynamics. Rodent species distribution shows that a new biogeographic  pattern  takes  place  along  a  North-South environmental  gradient, replacing the previous East-West  trend. This  study also evidences that changes at regional scale act  to regulate diversity at the European continental scale.
[List of localities used and references]
[Link to the Ph.D dissertation]

Post-doctoral works


Post-doctoral project "Biogeography of rodent communities in the Oligocene of Western Europe"

The project was to study the evolution of rodent faunas in South German Early Oligocene fossil localities in order to better understand the impact of environmental variation and new invasive species on fossil rodent communities.
The project was granted by the DAAD (Deutscher Akademischer Austausch Dienst ), and carried out at  the « Department für Geo- und Umwelt-wissenshaften, Section Paläontologie », University Ludwig-Maximilians of Munich

Throughout the Oligocene, Southern Germany presents a continuous and important fossil record propitious to answer this question. Since the first descriptions of fissure fillings (Dehm, 1935, 1937), several studies were made on South German fossil rodents: Pseudosciuridae (Schmidt-Kittler, 1971, 1979), Theridomyidae (Schmidt-Kittler & Vianey-Liaud, 1987; Gad, 1992), Cricetidae (Dienemann, 1987) and less recently Eomyidae (Fahlbusch, 1970, 1975). This project was also the opportunity to carry out a systematic study of Eomyid rodents (Mammalia, Rodentia, Eomyidae) in these localities and to compare the fossil material with other Early Oligocene European localities (Maridet et al. 2010).

EHM, R. 1935. Über tertiäre SpaltenFüllungen im Fränkischen und Schwäbischen Jura. Verlag der Bayerischen Akademie der Wissenschaften, 29:1-96.
EHM, R. 1937. Neue tertiäre Spaltenfüllungen im sudlichen Fränkischen Jura. Sonder-Abdruck aus dem Zentralblatt für Mineralogie etc., 9B:349-369
IENEMANN, A. 1987. Die Gattungen Eucricetodon und Pseudocricetodon (Rodentia, Mammalia) aus dem Oligozän Süddeutschlands. Verlag der Bayerischen Akademie der Wissenschaften, 165 :1-171.
AHLBUSCH, V. 1970. Populationsverschiebungen bei tertiären nagetieren, eine studie an oligozänen unt miozänen Eomyidae europas. Verlag der bayerischen Akademie der Wissenschaften, 145:7-136.
AHLBUSCH, V. 1975. Die Eomyiden (Rodentia, Mammalia) der Oberen Süßwasser-Molasse Bayerns. Mitteilungen der Bayerischen Staatssammlung für Paläontologie und histotische Geologie, 15:63-90.
AD, J. 1992. Biometrische Untersuchungen zur Evolution von Theridomys und Blainvillimys (Rodentia, Theridomorpha) des europäischen Alttertiärs mit Hilfe grafischer Datenverarbeitung. Mainzer Geowissenschaftliche Mitteilungen, 21 :71-144.
ARIDET O., HUGUENEY M. & HEISSIG K. 2010. New data about the diversity of Early Oligocene eomyids (Mammalia, Rodentia) in Western Europe. Geodiversitas 32 (2): 221-254.
CHMIDT-KITTLER, N., M. VIANEY-LIAUD. 1987. Morphometric analysis and evolution of the dental pattern of the genus Issiodoromys (Theridomyidae, Rodentia) of the European Oligocene as key to its evolution. Koninklijke Nederlandse Akademie van Wetenschappen, B 90(3):281-306.



Post-doctoral project "Biogeography and small mammals communities evolution in China form the Late Oligocene onward: focus on the Junggar basin (Xinjiang)"
The project starting in November 2007

During the Neogene (-25 to -3My), important climatic changes are known in Asia, especially due to the rising of the Himalayan range. The uplift of the Himalayan range since the Oligocene and its constant elevation during the Miocene (Spicer et al. 2003) are known to affect the asian environments (Wang et al. 1999) and the global climate (Kutzbach et al. 1989; Raymo & Ruddiman 1992). Since the late Oligocene and during the Early Miocene, the global climatic change and the uplift of the Himalayan range are known to induce an aridification of the environments in northern regions in China, such as evidenced by sedimentary deposits (Guo et al. 2002; Höck et al. 1999). The Neogene fossil record in the Junggar Basin (Xinjiang, NW China) provides a good record allowing to follow the evolution of mammalian communities (Bi 1999; Bi et al. 1999; Meng et al. 2006; Wu 1988; Wu et al. 2004; Wu et al. 2006), in a context of changing environments linked to the Asiatic climatic changes.

Both a detailed systematic study of the fossil small mammals and a statistic study of the diversity distribution undertaken within the IVPP paleomammaligy team (Xinjiang project) will lead to a better understanding of the mechanisms that link the structure of regional mammalian communities and the climatic context.

I, S.-D. 1999. Metexallerix from the Early Miocene of North Junggar Basin, Xinjiang Uygur autonomous region, China.Vertebrata PalAsiatica 37(2): 140-155.
BI, S.-D., WU, W.-Y., YE, J., MENG. J. 1999. Erinaceidae from the Middle Miocene of North Junggar Basin, Xinjiang Uygur autonomous region, China. In: Y. Wang. and T. Deng. (Editors), Proceedings of the Seventh Annual Meeting of the Chinese Society of Vertebrate Paleontology.China Ocean Press, Beijing : 157-165pp.
GUO, Z.-T., HAO, Q.-Z., WU, H.-B. QIAO, Y.-S., ZHU, R.-X., PENG, S.-Z., WEI, J.-J., YUAN, B.-Y., LIU, T.-S., 2002. Onset of Asian desertification by 22Myr ago infered from loess deposits in China. Nature, 416: 159-163.
HÖCK V, DAXNER-HÖCK G., SCHMID H.P., BADAMGARAV D., FRANK W., FURTMÜLLER G., MONTAG O., BARSBOLD R., KHAND Y., SODOV  J. 1999. Oligocene-Miocene sediments, fossils and basalts from the Valley of Lakes (Central Mongolia)- An integrated study. Mitteilungen der Österreichischen Geologischen Gesellschaft 90(1997): 83-125.
KUTZBACH, J.E., GUETTER, P.J., RUDDIMAN, W.F. & PRELL, W.L. 1989. The sensitivity of climate to late Cenozoic uplift in southern Asia and American west: Numerical experiment. Journal of Geophysic Research, 94: 18393-18407.
MENG, J., YE, J., Wu, W.-Y., YUE, L., NI, X.-J. 2006. A recommended boundary stratotype section for Xiejian stage from the Northern Junggar basin: implications to related bio-chronostratigraphy and environmental changes. Vertebrata PalAsiatica 44(3):205-236.
RAYMO, M.E., RUDDIMAN, W.F. 1992. Tectonic forcing of late Cenozoic climate change. Nature 359: 117-122.
SPICER, R.A., HARRIS, N.B.W., WIDDOWSON, M., HERMAN, A.B., 2003. Constant elevation of southern Tibet over the past 15 million years. Nature, 421: 622-624.
WU, W.-Y. 1988. The first discovery of Middle Miocene Rodents from the Northern Junggar Bsain, China. Vertebrata PalAsiatica 26(4): 250-264.
WU, W.-Y., MENG, J., YE, J., NI, X.-J. 2006. The first find of Eomyids (Rodentia) from the Late Oligocene-Early Miocene of the Northern Junggar Bsain, China. Beiträge zur Paläontologie 30: 469-479.
WU, W.-Y., MENG, J., YE, J., NI, X.-J. 2004. Propalaeocastor (Rodentia, Mammalia) from the Early Oligocene of Burqin Basin, Xinjiang. American Museum Novitates 3461: 1-16.



Reseach project "Radiation and dispersion of Eurasian myomorph rodents linked to the Paleogene climatic changes"
The project starting in July 2010  (NSFC project)

Today, rodents are the most diversified order of mammals, bearing more the half the known mammalian species. Among rodents, the suborder Myomorpha is especially well diversified in
Eurasia and represents more than a third of the world rodent species richness. The first record of Myomorph rodents is known in the Middle Eocene of China, where both families Cricetidae and Dipodidae have been discovered. However, the process of their radiation and successful diversification in Eurasia during the Paleogene is still poorly understood. In the last decade, new discoveries of Myomorph rodents in the Eocene and Oligocene of China have raised new questions about their origin and the impact of the climatic context on their diversity dynamic. This project proposes to tackle these questions by undertaking a phylogenetic and biogeographic analysis of the Paleogene myomorph rodents at Eurasian scale. The project will especially focus on the Eocene/Oligocene boundary which is a major climatic event that occurred at global scale (35 Ma) and induced a deep change in the terrestrial vertebrate faunas. This event was the greatest faunal extinctions known since the Cretaceous/Tertiary transition, 30 Ma before. In Europe, this fundamental change among faunas is related in part to the immigration of new species coming from
Asia, triggered by this dramatic climatic event. In order to tackle the question of the impact of climatic changes on myomorph rodents’ evolutionary history a comparison needs to be undertaken between different Eurasian key-areas in order to follow the changes in their distribution and diversity across Eurasia. For this reason, this project is based on international collaborations and includes the comparison and the description of new specimens from different regions of Eurasia:. Yunnan and Xinjiang provinces in China (In collaboration with: Meng Jin AMNH New York; Ni Xijun and Wu Wenyu, IVPP Beijing), central Mongolia (in collaboration with: Gudrun Daxner-Hock, NHM Vienna), Western Europe (in collaboration with: Marguerite Hugueney, University of Lyon) and Romania (in collaboration with Vlad Codrea, Univeristy of Cluj).



Post-doctoral project "Evolution and biodiversity of Oligo/Miocene Mongolian rodents "
The project starting in April 2012  (Lise-Meitner-Programm M1375)

The Oligocene/Miocene transition (c. 23 Ma) is a critical period in the evolutionary history of Eurasian mammals. Indeed most of Palaeogene groups of mammals disappear at the end of the Oligocene or along the course of the Early Miocene and are progressively replaced by the modern groups of mammals that compose the extant biodiversity. The climatic changes that encompass the Oligocene/Miocene transition might play a major role on the diversification and dispersal processes of modern mammal across Eurasia. The project aims at better understanding the impact of climatic and environmental changes on the diversity and evolution of rodents around the Oligocene-Miocene transition. This problem is actually two-folded because before addressing mammalian evolutionary issues, it is necessary to better characterize the evolution of terrestrial environments. To tackle these questions the study of the fossil material from the Palaeogene/Neogene sequence from the Valley of Lakes in Central Mongolia will be the base of integrated geological, palaeoecological and palaeoenvironmental studies in order to answer this problematic. The project will be carried out following three main approaches: (1) a detailed study and description of the fossil specimens associated with cladistic analyses in order to interpret the phylogenetic relationships of the Mongolian species with other Eurasian species, (2) palaeoenvironmentals reconstruction based on geological, palaeoecological and geochemical analyses, and (3) quantification of the palaeobiodiversity of Mongolian assemblages and other regions in order to follow its evolution, especially through the Oligocene/Miocene transition.
This research project will be carried out in the scope of the project "Impact of Oligo-Miocene climate changes on Mongolian mammals" (FWF-Project: P-23061-N19), lead by Gudrun Daxner-Höck and the teams of the Natural History Museum of Vienna. All the members of the team of the Natural History Museum of Vienna plus international collaborators gathered for the FWF-Project are specialists of various disciplines in geology, palaeontology and geochemistry giving the opportunity to develop the integrated multidisciplinary project.

Paleobiogeography of Eurasian Neogene small mammals

A database on Neogene small mammals of Europe was initiated during my PhD. This database has been used to carry out a synthetic biogeographic study (on Glires) in Europe between the Late Oligocene and the mid Pliocene (Maridet et al. in press). The purpose of this study was to assess the impact of environmental changes over species distribution, and thus to identify the environmental parameters (Climatic or geographic) that influence biodiversity evolution. This study has evidenced that the climatic parameters are predominant to influence the distribution of glires diversity. Finally he extant endemic situation in Europe appears to be rooted long before the beginning of the first glaciations.

The continuation of this study is now to extend the database to the Asian fossil record in order to undertake a broad scale study of diversity ditribution that will bring a better understanding of diversity exchanges between Europe and Asia throughout the Neogene.

Macroecological approach on fossil record

The general purpose of these studies on small mammals is to better understand the relationships between many aspects of diversity and the environmental context.
To do so, recent studies have been carried out at broad time and spatial scales, in order to observe long-term changes on paleobiodiversity. They have been carried out at a regional resolution, considering regional faunas as good proxies for metacommunities. Both the inner dynamic of metacommunities and the exchanges between metacommunities are studied at deep time resolution.
With this approach the fossil record is expected to provide clues that will lead to a better understanding of the relationships between the structure of metacommunities and all the environmental parameters.

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