Eritherium is an extinct genus of early Proboscidea found in the Ouled Abdoun basin (early Thanetian age), Morocco. It lived about 60 million years ago. It was first named by Emmanuel Gheerbrant in 2009 and the type species is Eritherium azzouzorum. Eritherium is the oldest, smallest and most primitive known elephant relative.
Description
The
holotype (specimen number MNHN PM69) is now in the Musée d'histoire naturelle - Guimet in
Lyon and includes an
maxilla (with approaches of the
zygomatic bone and two
maxillary nerve, each of the two posterior
premolars (P3 and 4) and three
molars (M1-3)). The piece is about 6 inches long, 5 inches wide and just over 3 inches high. In addition, the fossils include 15 more objects including the skull bones (frontal and nasal bones), lower jaw fragments and teeth and the upper and lower jaw.
It was about 20 cm tall at the shoulder and weighed about 5–6 kg.
Generally, Eritherium shared similarities in the structure of their teeth with other Paenungulata such as the extinct Embrithopoda or early representatives of the , but their teeth are more specialised. The dentition of the mandible that was reconstructed (from two left fragments) made up the complete sequence of the original teeth of mammals: with three , one canine tooth, four and three molars. The tooth row was closed and had no diastema between the canine tooth on the front and back teeth. This primitive mammalian dentition is unique among Proboscideans.
The molars were generally bunodont (i.e. with small Tooth enamel cusps on the occlusal surface-bearing structure). Between these bumps were approaches for forming transverse strips on the first two molars and on the rearmost molar, which is typical in lophodont. The premolars had only one (lower jaw) or two (in the maxilla) cusps. The first incisor is relatively large and asymmetric and already showed signs of reduction. These facts link Eritherium with other early Proboscideans. Another primitive characteristic is the short symphysis of the mandible.
The reconstruction of the upper portion of the skull showed that the eye socket was relatively far forward in the skull. Most other early Paenungulata had an orbit significantly shifted to the rear position of the skull.
Systematics
Eritherium is the oldest known representative of the
Proboscidean, although it remains unassigned to any family within this order.
Fitting with its great age,
Eritherium is basal to all other primitive proboscideans (including
Phosphatherium,
Numidotherium,
Moeritherium and
Daouitherium) which together form one of the most complete evolutionary sequences of early mammalian radiations following the K/T extinction event.
suggest that the closest relatives of the proboscid lineage are the manatees (
Sirenia) and
Desmostylia. Together with
Embrithopoda and the hyraxes (
Hyracoidea) they form the group
Paenungulata. The great age and location of
Eritherium support the hypothesis that paenungulates originated in Africa and diversified rapidly in the Paleocene.
Eritherium in cladogram after Tabuce et al., 2019:[Rodolphe Tabuce, Raphaël Sarr, Sylvain Adnet, Renaud Lebrun, Fabrice Lihoreau, Jeremy E. Martin, Bernard Sambou, Mustapha Thiam und Lionel Hautier: Filling a gap in the proboscidean fossil record: a new genus from the Lutetian of Senegal. Journal of Paleontology, 2019, ]
History of discovery
The findings of
Eritherium come from
Sidi Chennane, quarry in
Ouled Abdoun phosphate basin in Morocco.
These are 10 to 20 km south of
Grand Daoui, where in 1996 (
Phosphatherium) and 2002 (
Daouitherium) two early proboscideans were described. The
Eritherium fossils were found in the "lower bone bed" of the phosphate layer. Other fossils from this layer include earliest evidence of the carnivorous
Hyaenodontidae, and a diverse assortment of
elasmobranchs (sharks and rays). This places the findings in a geological time ranging from 61.1 to 57.8 million years ago. The genus was named by Emmanuel Gheerbrant (2009). The name
Eritherium comes from the Greek words "eρυ" (eri: old) and "θηρίον" (therion: animal), while the species name
azzouzorum honors the residents of the village of Ouled Azzouz, near where most of the fossils were discovered.
