Discovery Of Elephants' Oldest Known Relative

The beginnings of the radiation (diversification) of the modern mammals (placental orders) remain poorly known because of fossil gaps, and especially in some key Southern continents such as Africa. Emmanuel Gheerbrant, researcher at the CNRS ⁽²⁾, reports⁽³⁾ the discovery of one of the oldest known modern ungulates in Paleocene beds from Morocco. Dated to about 60 millions years ago, this fossil mammal belongs to a new species called Eritherium azzouzorum. It comes from the same Ouled Abdoun phosphate basin which yielded Phosphatherium escuilliei ⁽⁴⁾, which was until the Eritherium's discovery the oldest and most primitive proboscidean found. This is the oldest known African ungulate (called paenungulates), and among them the oldest known member of the elephant order (proboscideans) ⁽⁵⁾.

Eritherium azzouzorum is small (4 to 5 kg) and extraordinarily primitive. It exemplifies the emergence of a modern order of ungulates at a very primitive stage, which is illustrated by a likeness among proboscideans within primitive groups such as some condylarths ⁽⁶⁾ (louisinines, extinct) and non-paenungulate afrotherians (elephant shrews, Eocene to Present). Its primitiveness indicates  the rapid evolution of the proboscideans at the Paleocene-Eocene ⁽⁷⁾ transition (e.g., with increasing size), and the rapid radiation of the African ungulates after the Cretaceous-Tertiary crisis (65 millions years ago), probably in relation to the colonization of the herbivorous African free niches.

Eritherium is a new major find, and one of the oldest known calibration point of the phylogeny of the placental orders. It is especially important for the fine tuning of the placental molecular trees.

(1) UMR 7207 (MNHN/CNRS/Université Pierre et Marie Curie), Center for Research on Paleobiodiversity and Paleoenvironments ; .fr.

(2) Centre National de la Recherche Scientifique

(3) Paleontological research Agreement MNHN-OCP-Ministry of Energy and Mines (Rabat)-University Cadi Ayyad (Marrakech)-University Chouaib Doukkali (El Jadida).

(4) 55 millions years discovered in 1996 by the same team

(5) The elephant order or Proboscidea includes only 3 living species, but it has a very long and rich evolutionary history which is illustrated by 180 fossil species.

(6) Archaic ungulates which evolved at the end of the Cretaceous and the beginning of the Tertiary, and which includes the stem groups of the modern ungulates, as well as many extinct herbivorous lineages.

(7) The transition between Paleocene and Eocene occurred approximately 55 millions years ago.