Plesiotypotherium

Plesiotypotherium Temporal range: Middle-Late Miocene ~13–6 Ma PreꞒ Ꞓ O S D C P T J K Pg N .
Skull of Plesiotypotherium
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Notoungulata
Family:	†Mesotheriidae
Subfamily:	†Mesotheriinae
Genus:	†Plesiotypotherium Villarroel, 1974
Type species
†Plesiotypotherium achirense Villarroel, 1974
Species
P. achirense (Villarroel, 1974 P. casirense (Cerdeño et al, 2012) P. majus (Villarroel, 1974) P. minus (Croft, 2007)

Plesiotypotherium is an extinct genus of Notoungulate, belonging to the suborder Typotheria. It lived from the Middle to the Late Miocene, and its fossilized remains were discovered in South America.

Description

This animal was somewhat similar to modern wombats, but was slightly larger-sized. Plesiotypotherium, like its relatives Trachytherus and Mesotherium, was characterized by a postcranial skeleton suited for burrowing. Its scapula was characterized by a distally located suprascapular fossa; the deltoid crest was well developed. The humerus of Plesiotypotherium was slightly thinner than in Trachytherus, and had a characteristic perforation in the olecranon fossa. The entepicondyle, ectepicondyle and supracondylar crest were well developed. The ulna was characterized by a well developed olecranon, while in the proximal area of the radius a sesamoid bone was articulated with the main bone; the distal part of the radius had particular grooves for the tendons of the extensor muscle. The hand was strong; the carpal bones, the metacarpals and the phalanges were particularly strong. The pelvic area of Plesiotypotherium was characterized by its five vertebrae firmly fused with each other. The transverse processes of the penultimate vertebra were fused solidly with the ischium. The talus had a characteristic asymmetrical trochlear keel; the lateral keel was much wider than the middle one and evocative of those of ground sloths.

The skull was characterized by its large anterior incisors, separated from the posterior teeth by a large diastema; in the species Plesiotypotherium casirense, there was a bony process in the lacrimal bone, and a large infraorbital foramen.

Classification

Plesiotypotherium is a derived member of the family Mesotheriidae, a family of notoungulates whose representatives, while superficially similar to rodents, could reach relatively large sizes.

Plesiotypotherium was first described in 1974 by Villarroel, based on well-preserved fossils found near the location Achiri, in Bolivia, dated from the Middle to Late Miocene. The type species is Plesiotypotherium achirense, and Villarroel described also P. majus, from the same locality and horizon. More recent findings from the locality Chasira, also in Bolivia, were attributed to the new species p. casirense

Palbiology

Studies carried out on the postcranial skeleton of Plesiotypotherium have permitted to determine that it was adapted for burrowing into the ground, perhaps to unearth its alimentation, potentially composed of roots and tubers.^[1][2]

A skeleton belonging to Plesiotypotherium achirense showed numerous pathologies preserved in its bones and dentition. The skeleton shows the bilateral absence of permanent hypselodont molars, as well than the exostosis of several leg bones. The first pathology can be linked with the loss of the two first molars on both sides of the jaws, potentially due to long-lasting periodontal diseases ; other pathologies, notably in the skull, and possibly linked with the previous pathology, led to the overgrowth of the two first upper molars on both sides of the skull, and to the abnormal development of the masticatory muscles insertion. Other pathologies can be found in the postcranial skeleton, such as several bone growths in several areas over the articular surfaces of the leg bones, from the scapula to the distal phalanges. These pathologies may have limited the individual movements and its locomotion. Given its numerous pathologies, one could assume that this individual may have been an easy prey ; however, its long term survival suggests a low predatory pressure, a hypothesis congruent with the virtual absence of carnivorous vertebrates in the fossil record of the Achiri area, where its fossils were discovered. It is likely that Plesiotypotherium achirense lived in groups, like numerous extant herbivorous ungulates.^[3]

References

• Villarroel C (1974) Les mésothérinés (Notoungulata, Mammalia) du Pliocène de Bolivie et leurs rapports avec ceux d'Argentine. Ann Paléontol 60:245-281
• Y. Oiso. 1991. New land mammal locality of middle Miocene (Colloncuran) age from Nazareno, southern Bolivia. Fósiles y Facies de Bolivia - Vol. 1 Vertebrados (Revista Ténica de YPFB) 12(3-4):653-672
• E. Cerdeño, B. Vera, G. I. Schmidt, F. Pujos, and B. M. Quispe. 2012. An almost complete skeleton of a new Mesotheriidae (Notoungulata) from the Late Miocene of Casira, Bolivia. Journal of Systematic Palaeontology 10(2):341-360

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Genera of South American native ungulates

• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Superorder: Laurasiatheria

Xenungulata, Pyrotheria, Astrapotheria, and other minor groups
†Kollpaniidae? Andinodus Molinodus Pucanodus Simoclaenus Tiuclaenus †Didolodontidae Didolodus Enneoconus Ernestokokenia Escribania? Lamegoia Paulogervaisia Raulvaccia Ricardocifellia Saltaodus Umayodus †Xenungulata †Carodniidae Carodnia Etayoa Notoetayoa Rodcania †Pyrotheria †Colombitheriidae Colombitherium Proticia †Pyrotheriidae Baguatherium Berracotherium Carolozittelia Griphodon Propyrotherium Pyrotherium †Astrapotheria Eoastrapostylops †Trigonostylopidae Shecenia Tetragonostylops Trigonostylops †Astrapotheriidae Antarctodon Astrapodon Comahuetherium Liarthrus Maddenia Parastrapotherium †Albertogaudryinae Albertogaudrya Astraponotus †Astrapotheriinae Astrapothericulus Astrapotherium Scaglia †Uruguaytheriinae Granastrapotherium Hilarcotherium Uruguaytherium Xenastrapotherium

Litopterna
†Litopterna †Protolipternidae Asmithwoodwardia Miguelsoria Protolipterna †Amilnedwardsiidae Amilnedwardsia Ernestohaeckelia Rutimeyeria †Sparnotheriodontidae Notiolofos Phoradiadius Sparnotheriodon Victorlemoinea †Indaleciidae Adiantoides Indalecia †Notonychopidae Notonychops Requisia †Lopholipterna †Adianthidae Adianthus Proadiantus Proectocion? Proheptaconus Thadanius Tricoelodus †Macraucheniidae Polymorphis †Cramaucheniinae Caliphrium Coniopternium Cramauchenia Llullataruca Phoenixauchenia Pternoconius Theosodon †Macraucheniinae Cullinia Huayqueriana Macrauchenia Macraucheniopsis Micrauchenia Oxyodontherium Paranauchenia Promacrauchenia Scalabrinitherium Windhausenia Xenorhinotherium †Proterotheriidae Mesolicaphrium Neodolodus Olisanophus Promylophis Pseudobrachytherium †Anisolambdinae Anisolambda Eolicaphrium Guilielmofloweria Heteroglyphis Lambdaconops Paranisolambda Protheosodon †Proterotheriinae Anisolophus Brachytherium Diadiaphorus Diplasiotherium Eoauchenia Epecuenia Epitherium Lambdaconus Neobrachytherium Neolicaphrium Paramacrauchenia Picturotherium Prolicaphrium Proterotherium Tetramerorhinus Thoatheriopsis Thoatherium Uruguayodon Villarroelia †Megadolodinae Bounodus Megadolodus Uncertain placement Kyraodus Proacrodon Salladolodus Xesmodon Wainka

Notoungulata
incertae sedis Acoelodus Archaeogaia Carolodarwinia Perutherium †Notioprogonia Satshatemnus Seudenius †Henricosborniidae Henricosbornia Nanolophodon Othnielmarshia Peripantostylops Simpsonotus †Notostylopidae Boreastylops Chilestylops Edvardotrouessartia Homalostylops Notostylops Otrhonia Parastylops †Toxodontia †Homalodotheriidae Asmodeus Chasicotherium Homalodotherium Trigonolophodon †Isotemnidae Anisotemnus Coelostylodon Distylophorus Hedralophus Isotemnus Lophocoelus Pampatemnus Periphragnis Pleurocoelodon Pleurostylodon Rhyphodon Thomashuxleya †Eutoxodontia †Leontiniidae Anayatherium Ancylocoelus Colpodon Coquenia Elmerriggsia Gualta Henricofilholia Huilatherium Leontinia Martinmiguelia Purperia? Scarrittia Taubatherium Termastherium †Notohippidae Acoelohyrax Argyrohippus Deuterotherium? Edvardocopeia Eomorphippus Eurygenium Mendozahippus Moqueguahippus Morphippus Nesohippus Notohippus Pampahippus Pascualihippus Patagonhippus Perhippidion Plexotemnus Puelia Purperia? Rhynchippus Rosendo Stilhippus Teushentherium Trimerostephanos †Toxodontidae †Nesodontinae Adinotherium Nesodon Proadinotherium †Toxodontinae Abothrodon Andinotoxodon Calchaquitherium Ceratoxodon Charruatoxodon Dinotoxodon Eutomodus Falcontoxodon Gyrinodon Haplodontherium Hemixotodon Hoffstetterius Hyperoxotodon Mesenodon Mesotoxodon Minitoxodon Mixotoxodon Neoadinotherium Neotoxodon Nesodonopsis Nonotherium Ocnerotherium Palyeidodon Paratrigodon Pericotoxodon Piauhytherium Pisanodon Plesiotoxodon Posnanskytherium Prototrigodon Stenotephanos Stereotoxodon Toxodon Toxodontherium Trigodon Trigodonops Xotodon †Typotheria Campanorco Griphotherion †Archaeopithecidae Archaeopithecus Teratopithecus †Oldfieldthomasiidae Allalmeia Brachystephanus Camargomendesia Colbertia Dolichostylodon Itaboraitherium Kibenikhoria Maxschlosseria Oldfieldthomasia Paginula Suniodon Tsamnichoria Ultrapithecus Xenostephanus †Interatheriidae Antofagastia Ignigena Johnbell Munizia Punapithecus †Interatheriinae Archaeophylus Argyrohyrax Boleatherium Brucemacfaddenia Caenophilus Choichephilum Cochilius Eopachyrucos Federicoanaya Interatherium Juchuysillu Miocochilius Neoicochilus Patriarchus Proargyrohyrax Progaleopithecus Protypotherium Santiagorothia †Notopithecinae Antepithecus Guilielmoscottia Notopithecus Transpithecus †Mesotheriidae Fiandraia? Trachytherus †Mesotheriinae Altitypotherium Caraguatypotherium Eotypotherium Eutypotherium Hypsitherium Mesotherium Microtypotherium Plesiotypotherium Pseudotypotherium Rusconitherium Typotheriopsis †Archaeohyracidae Archaeohyrax Archaeotypotherium Bryanpattersonia Eohyrax Pascualhyrax Protarchaeohyrax Pseudhyrax Punahyrax †Hegetotheriidae †Hegetotheriinae Ethegotherium Hegetotheriopsis Hegetotherium Hemihegetotherium Prohegetotherium Pseudohegetotherium Sallatherium †Pachyrukhinae Medistylus Propachyrucos Prosotherium Tremacyllus †Pachyrukhini Pachyrukhos Paedotherium Tremacyllus