Megistotherium

Megistotherium is an extinct genus of hyainailourid hyaenodonts from paraphyletic subfamily Hyainailourinae that lived in Africa.[3][4][5][6]

Megistotherium
Temporal range: early Miocene
Comparison of various Early to Middle Miocene hyaenodonts, including the hyainailurids Hyainailouros sulzeri (top) and Megistotherium osteothlastes (center), and teratodontid Dissopsalis pyroclasticus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: †Hyaenodonta
Family: †Hyainailouridae
Subfamily: †Hyainailourinae
Genus: †Megistotherium
Savage, 1973[1]
Type species
†Megistotherium osteothlastes
Savage, 1973
Synonyms
synonyms of species:
  • M. osteothlastes:
    • Hyainailouros osteothlastes (Morales & Pickford, 2017)[2]

Etymology

The name of this genus comes from Ancient Greek μέγιστον (mégiston) 'greatest' and from Ancient Greek θήριον (thēríon) 'beast'.[1]

The name of species Megistotherium osteothlastes comes from Ancient Greek ὀστέον (ostéon) 'bone' and from Ancient Greek θλᾰστός (thlastos) 'crushed' or 'bruised' (with -es being an agent noun: 'bone-crusher').[1]

Description

Megistotherium osteothlastes is the only known species from this genus, and it was a large hyainailourid that lived during the early Miocene. Its remains have been found in the Ngorora and Muruyur Formations of Kenya, Egypt,[7] Namibia, Uganda[8] and Libya. Named by Robert Savage in 1973,[1] Megistotherium is one of the largest known hyaenodonts. Like the other hyaenodonts, it had an enormous skull relative to its body; up to 66.4 cm (2 ft 2.1 in) in length[1] and a body mass estimated at 500 kg (1,100 lb).[9] The carnassial teeth of Megistotherium (like those of other hyaenodonts) were the upper first molars, and overlapped with their lower molar counterparts like scissors to form a formidable and powerful shearing action.

Paleoecology

The land that is now the Sahara desert was much more fertile in the Miocene. A considerable amount of it was grassland and rainfall was plentiful. Lakes and ponds provided water for large fauna, which provided Megistotherium and other predators with an ample supply of prey. Large hyaenodontids like this one could have originally evolved as specialized predators or scavengers of large African herbivores.[10] Gomphothere bones have been found with its fossils, indicating that Megistotherium may have hunted them for food.

Classification and phylogeny

Taxonomic history

The family Hyainailouridae comprised a diverse group of hyaenodont predators that were most successful during the Eocene before being possibly ecologically displaced by the order Carnivora during the late Oligocene. Megistotherium emerged in the Miocene towards the end of the hyaenodonts' flourishing; it was a part of a radiation of African hyaenodontids that occurred at that time. Hyainailouros sulzeri is very closely related to Megistotherium, extremely similar in size, structure and ratios - with a long tail, short limbs and robust body.[11] Other authorities[12][7][8] have suggested that Megistotherium is actually a junior synonym of Hyainailouros sulzeri, which is known by an almost complete skeleton, among other remains, and has been found in Europe, Asia and Namibia,[13] and therefore comes from the same localities.

Phylogeny

The phylogenetic relationships of genus Megistotherium are shown in the following cladogram:[14][15][16][17][18]

 †Hyaenodonta 

†Eoproviverra

†Boualitomidae

†Arfiidae

†Limnocyonidae

†Sinopidae

†Hyaenodontoidea

†Gazinocyon

†Pyrocyon

†Galecyon

 †Afro‑Arabian clade 

†Parvavorodon

†Indohyaenodontidae

†Glibzegdouia

†Koholiidae

†Tritemnodon

†Teratodontidae

†Apterodontinae

†Maocyon

 †Maocyon/Orienspterodon clade

†Orienspterodon

†Hyainailourinae

†Hemipsalodon

 ? 

†Ischnognathus

 †Akhnatenavus clade

†Akhnatenavus

†"Pterodon" sp. (BC 15’08)

†Hyainailourinae sp. (UON 84-359)

†Hyainailourinae sp. C (DPC 9243 & DPC 10315)

†Hyainailourinae sp. D (DPC 6545)

†Kerberos

†"Pterodon" syrtos

 †Pterodon clade

†Pterodontina

†Hyainailourinae sp. A (DPC 6555)

†"Pterodon" africanus

†Parapterodon

†"Pterodon" sp. (DPC 5036)

†"Pterodon" phiomensis

†Hyainailourini

†Paroxyaenini

†Falcatodon

†Sectisodon

†Exiguodon

†Isohyaenodon zadoki

†Isohyaenodon  (†Isohyaenodontina)

†Isohyaenodon andrewsi

†Sivapterodon

†Hyainailouros bugtiensis

†Hyainailouros napakensis

†Hyainailouros

†Hyainailouros sulzeri

†Hyainailourinae sp. (GSN AD 100’96)

†Simbakubwa

†Metapterodontini

†Mlanyama

†Leakitheriini

 †Megistotherium 

†Megistotherium osteothlastes

†Pakakali

†Prionogalidae

 †Hyainailouridae
†Lahimia clade
†Arfia clade
†Galecyon clade
†Indohyaenodon clade
†Tritemnodon clade

See also

References
  1. Savage, R. J. G. (1973). "Megistotherium, gigantic hyaenodont from Miocene of Gebel Zelten, Libya". Bulletin of the British Museum (Natural History), Geology. 22 (7): 483–511. doi:10.5962/p.150151.
  2. Jorge Morales; Martin Pickford (2017). "New hyaenodonts (Ferae, Mammalia) from the Early Miocene of Napak (Uganda), Koru (Kenya) and Grillental (Namibia)" (PDF). Fossil Imprint. 73 (3–4): 332–359. doi:10.2478/if-2017-0019. S2CID 31350436.
  3. McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals Above the Species Level. New York: Columbia University Press. ISBN 978-0-231-11012-9. Retrieved 16 March 2015.
  4. Morales, Jorge; Pickford, M.; Salesa, Manuel J. (2008). "Creodonta and Carnivora from the Early Miocene of the Northern Sperrgebiet, Namibia". Memoir of the Geological Survey of Namibia. 20: 291–310.
  5. Solé, F.; Lhuillier, J.; Adaci, M.; Bensalah, M.; Mahboubi, M.; Tabuce, R. (2013). "The hyaenodontidans from the Gour Lazib area (?Early Eocene, Algeria): implications concerning the systematics and the origin of the Hyainailourinae and Teratodontinae". Journal of Systematic Palaeontology. 12 (3): 303–322. doi:10.1080/14772019.2013.795196. S2CID 84475034.
  6. Matthew R. Borths; Nancy J. Stevens (2017). "The first hyaenodont from the late Oligocene Nsungwe Formation of Tanzania: Paleoecological insights into the Paleogene-Neogene carnivore transition". PLOS ONE. 12 (10): e0185301. Bibcode:2017PLoSO..1285301B. doi:10.1371/journal.pone.0185301. PMC 5636082. PMID 29020030.
  7. Morlo, M., Miller, E.R., and El-Barkooky, A.N. 2007. Creodonta and Carnivora from Wadi Moghra, Egypt. Journal of Vertebrate Paleontology 27: 145–159. doi:10.1671/0272-4634(2007)27[145:CACFWM2.0.CO;2]
  8. Morales, J. and M. Pickford. (2008). "Creodonts and carnivores from the Middle Miocene Muruyur Formation at Kipsaraman and Cheparawa, Baringo District, Kenya." Comptes Rendus Palevol 7 (8): 487-497
  9. Sorkin, B. (2008-04-10). "A biomechanical constraint on body mass in terrestrial mammalian predators". Lethaia. 41 (4): 333–347. doi:10.1111/j.1502-3931.2007.00091.x.
  10. Rasmussen, D. Tab; Tilden, Christopher D.; Simons, Elwyn L. (May 1989). "New specimens of the giant creodont Megistotherium (Hyaenodontidae) from Moghara, Egypt". Journal of Mammalogy. 70 (2): 442–447. doi:10.2307/1381539. JSTOR 1381539.
  11. Ginsburg, L. (1980.) "Hyainailouros sulzeri, mammifère créodonte du Miocène d’Europe." Ann. Paléont., 66, 19-73
  12. Morales, J. and Pickford, M. (2005.) "Carnivores from the Middle Miocene Ngorora Formation (13-12 Ma) Kenya." Estudios Geol., 61, 271-284
  13. J. Morales, M. Pickford, S. Fraile, M. J. Salesa and D. Soria (2003.) "Creodonta and Carnivora from Arrisdrift, early Middle Miocene of southern Namibia" Mem. Geol. Surv. Namibia 19 177–194.
  14. Borths, Matthew R.; Stevens, Nancy J. (2017). "Deciduous dentition and dental eruption of Hyainailouroidea (Hyaenodonta, "Creodonta," Placentalia, Mammalia)". Palaeontologia Electronica. 20 (3): 55A. doi:10.26879/776.
  15. Matthew R. Borths; Nancy J. Stevens (2019). "Simbakubwa kutokaafrika, gen. et sp. nov. (Hyainailourinae, Hyaenodonta, 'Creodonta,' Mammalia), a gigantic carnivore from the earliest Miocene of Kenya". Journal of Vertebrate Paleontology. 39 (1): e1570222. Bibcode:2019JVPal..39E0222B. doi:10.1080/02724634.2019.1570222. S2CID 145972918.
  16. Floréal Solé; Bernard Marandat; Fabrice Lihoreau (2020). "The hyaenodonts (Mammalia) from the French locality of Aumelas (Hérault), with possible new representatives from the late Ypresian". Geodiversitas. 42 (13): 185–214. doi:10.5252/geodiversitas2020v42a13. S2CID 219585388.
  17. Solé, F.; Morlo, M.; Schaal, T.; Lehmann, T. (2021). "New hyaenodonts (Mammalia) from the late Ypresian locality of Prémontré (France) support a radiation of the hyaenodonts in Europe already at the end of the early Eocene". Geobios. 66–67: 119–141. Bibcode:2021Geobi..66..119S. doi:10.1016/j.geobios.2021.02.004. S2CID 234848856.
  18. Averianov, Alexander; Obraztsova, Ekaterina; Danilov, Igor; Jin, Jian-Hua (2023). "A new hypercarnivorous hyaenodont from the Eocene of South China". Frontiers in Ecology and Evolution. 11. doi:10.3389/fevo.2023.1076819. ISSN 2296-701X.
  • Domning, D. P. (1978.) "Sirenia." Evolution of African Mammals. pp. 573–581.
  • Egi, Naoko (2001.) "Body Mass Estimates in Extinct Mammals from Limb Bone Dimensions: the Case of North American Hyaenodontids." Palaeontology. Vol. 44, Issue 3, Page 497.
  • Leakey, L. S. B. and R. J. G. Savage (Editors) (1976.) "Fossil Vertebrates of Africa." Academic Press Inc., U.S. ISBN 0-12-440404-9.
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