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Moeritherium

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Moeritherium
Temporal range: Late Eocene, 37–35 Ma
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Skeleton of Moeritherium at the National Museum of Nature and Science, Tokyo, Japan
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Family: †Moeritheriidae
C.W. Andrews, 1906
Genus: †Moeritherium
C.W. Andrews, 1901
Type species
Moeritherium lyonsi
Andrews, 1901
Species

Moeritherium ("the beast from Lake Moeris") is an extinct genus of basal proboscideans from the Eocene of North and West Africa. The first specimen was discovered in strata from the Fayum fossil deposits of Egypt. It was named in 1901 by Charles William Andrews, who suggested that it was an early proboscidean, perhaps ancestral to mastodons. Six additional species have been named, though only three (M. lyonsi, M. gracile, and M. chehbeurameuri), are currently considered valid.

Taxonomy

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Map of the Fayum area of Egypt

Early history

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The type species of Moeritherium, M. lyonsi, was discovered in strata belonging to the Qasr el Sagha Formation in the Fayum fossil deposits of Egypt.[1] The type specimen (CGM C.10000) consists of an almost complete mandible.[2][3] It was described in 1901 by Charles William Andrews, who proposed two hypotheses for its phylogenetic position: either Moeritherium was part of the obsolete order Amblypoda, or it was an early proboscidean, perhaps "a generalised forerunner of the Mastodon type". In any case, he regarded it as an ungulate.[2]

Additional species

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In 1902, after conducting a more thorough examination of specimens collected by himself and his colleague, Hugh John Llewellyn Beadnell, he named a second species from the Qasr el Sagha, M. gracile; a third was recognised in the same paper, though he did not provide a name, and referred to it simply as M. sp. The two species were distinguished from M. lyonsi by a more gracile build and a larger body size respectively.[4] The lack of material overlap has made it difficult to determine how M. gracile actually relates to M. lyonsi, as their holotypes consist of different skull elements; the type specimen of the former (CGM C.10003) is a palate with no associated lower teeth. Regardless, they are treated as belonging to the same genus, and are likely separate.[3] Two years later, a fourth taxon, M. trigodon, was described, also by Andrews, based on remains recovered from the "fluvio-marine beds"[5][6] (equivalent to the Jebel Qatrani Formation)[7] around the lake Birket-el-Qurun.[6] In 1955, over half a century after the genus' initial naming, Sri Lankan artist and palaeontologist Paulus Edward Pieris Deraniyagala named two additional species, P. latidens and P. pharaonensis, based on isolated mandibular fragments.[8]

In 1911, German zoologist Max Schlosser divided M. lyonsi into two species: M. lyonsi, restricted to the Qasr el Sagha Formation, and M. andrewsi, restricted to the Jebel Qatrani.[9] This classification, however, has been rejected. In 1971, German zoologist Heinz Tobien opted to synonymise the entire genus with M. lyonsi,[10] though he chose to altogether disregard, Deraniyagala's species, likely as they were poorly diagnostic.[3] In 2006, Cyrile Delmer et al. published a paper describing a new Moeritherium species, M. chehbeurameuri, from Bir El Ater, Algeria. In their paper, they treated most of the above species (with the exception of M. latidens and M. pharaonensis) as valid. While the paper was not intended as a systematic revision, they chose to treat at the very least three species as valid: the type species M. lyonsi, M. gracile, and M. chehbeaurameuri.[3]

Classification

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Henry Fairfield Osborn, in 1921, divided Proboscidea into four suborders or superfamilies: Moeritherioidea, Deinotherioidea, Mastodontoidea, and Elephantoidea.[11] In a 1988 paper discussing the systematics of proboscideans, Pascal Tassy abandoned this system and neglected to provide any superfamily-rank clades. Erecting the suborder Elephantiformes, Tassy placed Moeritherium outside it, alongside Barytherium, Numidotherium, and the Deinotheriidae. He considered Moeritherium among the most basal proboscideans, with Numidotherium being the most basal and Barytherium being only slightly less basal than that.[12] In a 2021 paper describing a new genus (Dagbatitherium tassyi) Lionel Hautier et al. ran a phylogenetic analysis which recovered Moeritherium as sister to a clade including deinotheres and elephantiforms.[13]

A cladogram of Proboscidea based on the phylogenetic analysis of Hautier et al. 2021 is below:[13]

Proboscidea

Description

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Size comparison of Moeritherium lysoni compared to a human

Moeritherium was a fairly small, very elongate taxon. It was smaller than most later proboscideans. The species M. lyonsi has an estimated body length of 230 cm (7.5 ft). At the shoulder, this species measured only 70 cm (2.3 ft), and it had a body mass of 235 kg (518 lb).[14]

Skull

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The shape of the skull suggests that, while Moeritherium did not have an elephant-like trunk, it may have had a broad flexible upper lip like a tapir's for grasping aquatic vegetation. The second incisor teeth formed small tusks, although these would have looked more like the teeth of a hippo than a modern elephant.[15][16]

Ecology

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Isotopic analysis suggests that Moertherium was amphibious/semiaquatic and probably consumed freshwater plants.[17]

References

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  1. ^ Matsumoto, Hikoshichiro; Andrews, Charles William (1923). "A contribution to the knowledge of Moeritherium. Bulletin of the AMNH ; v. 48, article 4". Bulletin of the American Museum of Natural History.
  2. ^ a b Andrews, Charles William (1901). "II.—Preliminary Note on some Recently Discovered Extinct Vertebrates from Egypt. (Part I.)". Geological Magazine. 8 (9): 400–409. doi:10.1017/S0016756800179282. ISSN 1469-5081.
  3. ^ a b c d Delmer, Cyrille; Mahboubi, Mohamed; Tabuce, Rodolphe; Tassy, Pascal (2006). "A New Species of Moeritherium (proboscidea, Mammalia) from the Eocene of Algeria: New Perspectives on the Ancestral Morphotype of the Genus". Palaeontology. 49 (2): 421–434. doi:10.1111/j.1475-4983.2006.00548.x. ISSN 1475-4983.
  4. ^ Andrews, Charles William (1902). "II.—Preliminary Note on some Recently Discovered Extinct Vertebrates from Egypt. (Part III.)". Geological Magazine. 9 (7): 291–295. doi:10.1017/S0016756800181178. ISSN 1469-5081.
  5. ^ Matsumoto, H. 1922. Revision of Palæomastodon and Mœritherium. Palæomastodon intermedius, and Phiomia osborni, new species. American Museum Novitates. Number 51, November 21.
  6. ^ a b Andrews, Charles William (1904). "Further notes on the mammals of the Eocene of Egypt (Part I)". Geological Magazine, Decade V, New Series. 1: 109–115.
  7. ^ Badawy, Hanan S. (2018-03-01). "Termite nests, rhizoliths and pedotypes of the Oligocene fluviomarine rock sequence in northern Egypt: Proxies for Tethyan tropical palaeoclimates". Palaeogeography, Palaeoclimatology, Palaeoecology. 492: 161–176. doi:10.1016/j.palaeo.2017.12.021. ISSN 0031-0182.
  8. ^ Deraniyagala, Paulus Edward Pieris (1955). "Some extinct elephants, their relatives and the two living species". Ceylon National Publications, Colombo.
  9. ^ Schlosser, Max (1911). "Beiträge zur Kenntnis der oligozänen Landsäugetiere aus dem Fayum, Ägypten". Beiträge zur Paläontologie und Geologie Österreich-Ungarns. 24: 1–167.
  10. ^ Tobien, Heinz (1971). "Moeritherium, Palaeomastodon, Phiomia aus dem Paläeogen Nordafrikas und die Abstammung der Mastodonten (Proboscidea, Mammalia)". Mitteilungen aus dem Geologischen Institut der Technischen Universität, 10, 141–163. 10: 141–163.
  11. ^ Osborn, Henry Fairfield (1936). "Proboscidea. Vol. 1: Moeritherioidea, Deinotherioidea, Mastodontoidea". Amer. Mus. Press, New York.
  12. ^ Tassy, Pascal (1988). "THE CLASSIFICATION OF PROBOSCIDEA: HOW MANY CLADISTIC CLASSIFICATIONS?". Cladistics. 4 (1): 43–57. doi:10.1111/j.1096-0031.1988.tb00467.x. ISSN 0748-3007.
  13. ^ a b Hautier, Lionel; Tabuce, Rodolphe; Mourlam, Mickaël J.; Kassegne, Koffi Evenyon; Amoudji, Yawovi Zikpi; Orliac, Maëva; Quillévéré, Frédéric; Charruault, Anne-Lise; Johnson, Ampah Kodjo Christophe; Guinot, Guillaume (2021-10-13). "New Middle Eocene proboscidean from Togo illuminates the early evolution of the elephantiform-like dental pattern". Proceedings of the Royal Society B: Biological Sciences. 288 (1960). doi:10.1098/rspb.2021.1439. ISSN 0962-8452. PMC 8511763. PMID 34641726.
  14. ^ Larramendi, A. (2016). "Shoulder height, body mass and shape of proboscideans" (PDF). Acta Palaeontologica Polonica. 61. doi:10.4202/app.00136.2014.
  15. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 238. ISBN 978-1-84028-152-1.
  16. ^ Savage, RJG; Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. p. 147. ISBN 978-0-8160-1194-0.
  17. ^ Liu, Alexander G. S. C.; Seiffert, Erik R.; Simons, Elwyn L. (2008-04-15). "Stable isotope evidence for an amphibious phase in early proboscidean evolution". Proceedings of the National Academy of Sciences. 105 (15): 5786–5791. Bibcode:2008PNAS..105.5786L. doi:10.1073/pnas.0800884105. ISSN 0027-8424. PMC 2311368. PMID 18413605.
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