Eritherium
Eritherium is an extinct genus of early Proboscidea found in the Ouled Abdoun basin, 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 is now in the Musée d'histoire naturelle - Guimet in Lyon and includes an upper jaw and three molars ). 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, 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 manatees, but their teeth are more specialised. The dentition of the mandible that was reconstructed made up the complete sequence of the original teeth of mammals: with three incisors, one canine, four premolars 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. Between these bumps were approaches for forming transverse strips on the first two molars and on the rearmost molar, which is typical in lophodont teeth. The premolars had only one or two 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 Proboscidea, although it remains unassigned to any family within this order. Fitting with its great age, Eritherium is basal to all other primitive proboscideans which together form one of the most complete evolutionary sequences of early mammalian radiations following the K/T extinction event. Cladistic analyses suggest that the closest relatives of the proboscid lineage are the manatees and Desmostylia. Together with Embrithopoda and the hyraxes 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: