Eritherium

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Eritherium
Temporal range: Selandian, 60  Ma
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Eritherium azzouzorum 54.JPG
Jaw of Eritherium azzouzorum
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Genus: Eritherium
Gheerbrant, 2009
Species:
E. azzouzorum
Binomial name
Eritherium azzouzorum
Gheerbrant, 2009

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.

Contents

Description

The holotype (specimen number MNHN PM69) is now in the Musée d'histoire naturelle - Guimet in Lyon and includes an upper jaw (with approaches of the zygomatic bone and two maxillary branches, 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. [1] It was about 20 cm tall at the shoulder and weighed about 5–6 kg. [2]

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 (from two left fragments) 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 (i.e. with small 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 teeth. 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 Proboscidea, although it remains unassigned to any family within this order. [1] 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. [1] Cladistic analyses 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. [1]

Eritherium in cladogram after Tabuce et al., 2019: [3]

  Proboscidea  

History of discovery

The findings of Eritherium come from Sidi Chennane, quarry in Ouled Abdoun phosphate basin in Morocco. [1] 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. [1]

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<span class="mw-page-title-main">Proboscidea</span> Order of elephant-like mammals

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<span class="mw-page-title-main">Desmostylia</span> Extinct order of mammals

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Dagbatitherium is an extinct genus of proboscideans. So far a single molar from the phosphate basins of Togo in West Africa has been found. The fossil dates to the Middle Eocene, around 47 million years ago. A striking feature of the tooth are the three pairs of cusps oriented transversely to the longitudinal axis of the tooth. This feature is found in more derived proboscideans, which are grouped in the Elephantiformes. For its age, Dagbatitherium is the earliest member of Elephantiformes to date. Furthermore, it is characterized by a low tooth crown and a humped occlusal pattern. The genus was described in 2021.

Taowu is an extinct genus of machairodonts, a type of saber-toothed cat. It lived during the Early Pleistocene about 2.5 million years ago in East Asia. So far, only one skull is known, found in northern China. Based on this, a relatively small representative of the saber-toothed cats can be reconstructed, which only reached the size of a present-day leopard. In its dentition characteristics, it mediates between phylogenetic older forms such as Amphimachairodus and younger members such as Homotherium. The genus was scientifically described in 2022, but the find material was recovered as early as the 1930s.

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Hadrogeneios is an extinct genus of afrotherian mammal recovered from the Khouribga Phosphates of the Ouled Abdoun Basin dating from the Selandian to the Thanetian. Only the type species H. phosphaticus is known for this genus, with the material being of dental and jaw specimens. The placement of Hadrogeneios recovered it to be the most basal stem-paenungulate, the clade that includes elephants, sea cows, and hyraxes. Despite this Hadrogeneios was a contemporary of more derived members of the group such as Abdounodus, Ocepeia, and the early proboscideans Eritherium, Phosphatherium, and Daouitherium.

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References

  1. 1 2 3 4 5 6 Emmanuel Gheerbrant (2009). "Paleocene emergence of elephant relatives and the rapid radiation of African ungulates". Proceedings of the National Academy of Sciences of the United States of America. 106 (26): 10717–10721. Bibcode:2009PNAS..10610717G. doi: 10.1073/pnas.0900251106 . PMC   2705600 . PMID   19549873.
  2. Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi: 10.4202/app.00136.2014 .
  3. 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, doi:10.1017/jpa.2019.98