Cretaceous and Paleogene mammals from Africa and Eurasia : origin, initial radiation and paleobiogeographical history of extant placental orders and primitive eutherians.
My research deals mainly with the early history of the placental mammals in the Arabo-African Province when the continent was insular, i.e., before the closure of the Tethys, in several respects: systematics, phylogeny, biostratigraphy and macroevolution (especially by the Cretaceous-Tertiary and Paleocene-Eocene transitions), paleoecology, and paleobiogeography.
Isolated Africa, ca. 100-24 Ma
The origin of the African placental colonization (phylogeny and paleobiogeography, geodynamic context) is a major, still unresolved question. The initial radiation of endemic African placentals, including ungulates (tubulidentates, hyracoids, embrithopods, proboscideans, sirenians), "creodonts" (hyaenodontids), primates (strepsirhines and simiiforms), macroscelideans and insectivores (tenrecoideans), is also one of the most important questions in contemporaneous mammalian paleontology.
I am also interested in the paleobiogeographical history of the Cretaceous-Paleogene mammals from the European province, with questions such as :
1) the relationships between West and East European faunas ;
2) the North - South European provincialism ;
3) faunal exchanges between Europe and Asia (trans-Ouralian dispersals), and between Europe and North America ;
4) trans-Tethyan faunal interchanges between Europe and Africa (see below).
Key-European mammal localities which are investigated in this regard are those of Lano (Spain; Gheerbrant & Astibia 1999), Tricouté (France, Gheerbrant et al. 1997a), Archingeay (France, Vullo et al. 2009), Campo (Spain, Gheerbrant et al. 1997b), Jibou (Romania ; Gheerbrant et al. 1999), and Le Quesnoy (France; Nel et al. 1999, Gheerbrant et al. 2005a).
|Mammals from Jibou & Rona, Late Paleocene of Transylvania, Romania (Gheerbrant et al. 1999)|
Louisinidae Paschatherium sp.
Cimolestidae, Aboletylestes sp.
My main working tools in this research are the comparative anatomy of dental and cranial fossil mammalian material, and the phylogenetic study (character analysis, cladistic analysis). I am especially interested in the morpho-functional approach of the mammalian dentition and paleodiets of early placentals.
The study is based on our rich MNHN collections, and also on field works in order to get new fossil data. The discovery of new Cretaceous and Paleogene fossil remains of mammals in Africa is especially one of the major challenges of the paleontology and phylogeny of the African placentals.
The Ouled Abdoun Basin (Morocco) has yielded the oldest African ungulates, including the first known representatives of the elephant order, the proboscideans (Gheerbrant et al. 1996, 1998, 2002, 2005b, 2009).
Sidi Chennane quarries, Ouled Abdoun, Morocco
The Ouled Abdoun mammals are of primary significance to test the recent molecular phylogenetical hypotheses, especially the controverted superclade Afrotheria and the better supported Paenungulata (see Gheerbrant et al. 2005c).
Late Cretaceous and Paleocene mammals from Europe are also very poorly known and are also central in my field research. I am especially involved in the study of the mammal faunas from the late Paleocene of Transylvania (Jibou) and from the early Eocene of France (Le Quesnoy) which provide new data for the knowledge of mammal evolution at PE transition in Europe. My current field research focuses also on Campano-Maastrichtian sites from North (Tricouté) and South Pyrenees (Lano).
My systematic and phylogenetic work focuse on the primitive eutherian taxa such as "cimolestans", paleoryctids, pantolestans, palaeanodonts, "condylarths" and on the origin of the modern major placental lineages from these stem groups. Examples of current studies include the European "zhelestids" and "hyopsodontids" ("condylarths"), the early European lipotyphlans, the African condylarth stem groups (Ouled Abdoun), the primitive African hyaenodontid "creodonts", the earliest known representative of extant paenungulate orders, and the Paleogene African primates (e.g., oligopithecids from Oman).
The latest work on the Ouled Abdoun mammals provides new significant data (e.g, Boualitomus, and Lahimia) for an African origin of the Hyaenodontidae and its order "Creodonta" (Gheerbrant et al. 2006, Solé et al. 2009). We also recently published the monographic study of Phosphatherium (Gheerbrant et al. 2005b), including the skull reconstruction of this very primitive proboscidean, and an extended cladistic analysis of early proboscideans and other lophodont ungulates. This work suggests an old (at least Paleocene) African root for the elephant order (Proboscidea), and it supports a single clade for the African ungulates, the Paenungulata. This is evidenced by recent discovery and description of the archaic proboscidean Eritherium azzouzorum from the Paleocene of Sidi Chennane quarries ; Eritherium suggests moreover a recent and rapid paenungulate radiation after the Cretaceous-Tertiary boundary.
Early Ypresian of Sidi Daoui, Ouled Abdoun basin, Morocco
The locality where was discovered the skull of
Phosphatherium escuilliei Skull
Phosphatherium escuilliei, reconstruction of the head
In the course of my Habilitation thesis, I made the review of the paleobiogeographical history (e.g., endemism phases and trans-Tethyan dispersal phases) of the African Paleogene mammals (Gheerbrant 2001). In collaboration with J.C. Rage (UMR 7207, Paris), we have extended the review to the paleobiogeography of the whole vertebrate fauna of the Cretaceous and Paleogene of Africa (Gheerbrant & Rage 2006). It especially shows that Africa had a more complex paleobiogeographical history than the classical one seen in the context of the dual world of Laurasia versus Gondwana. This is illustrated by very early and repeated trans-Tethyan faunal exchanges with Laurasia, poor relationships with other Gondwanan continents since the opening of the South Atlantic, and marked endemic evolution (leading to major Tertiary endemic placental radiations), possibly as soon as the Early Cretaceous. It is shown that Africa took very early the main features of its currents biogeographical pattern, probably since the mid-Cretaceous (isolation from Gondwana + interchanges with Laurasia by way of the Mediterranean Sill).
My analysis of the paleobiogeographical history of African Paleogene mammals is based on an overview of the current phylogenetic hypotheses of the main African taxa and on a first data base of the known Paleogene fossil record of Africa.