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Trigonostylopoidea (disused)

Mammalia

Taxonomy
Trigonostylopoidea was named by Simpson (1934).

It was assigned to Astrapotheria by Simpson (1934); to Ungulata by Simpson (1967); and to Meridiungulata by McKenna (1975).

Synonymy list
YearName and author
1934Trigonostylopoidea Simpson
1967Trigonostylopoidea Simpson
1975Trigonostylopoidea McKenna p. 43

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RankNameAuthor
kingdomAnimalia()
—Bilateria
—EubilateriaAx 1987
—Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
—Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
—Tetrapoda
—Reptiliomorpha
—Anthracosauria
subclassAmphibiosauriaKuhn 1967
—Cotylosauria()
—Amniota
RankNameAuthor
subclassSynapsida
—Therapsida()
infraorderCynodontia()
—Mammaliamorpha
—Mammaliaformes
classMammalia
—Theriamorpha(Rowe 1993)
—Theriiformes()
—Trechnotheria
—Cladotheria
—Zatheria
subclassTribosphenida()
subclassTheria
—Eutheria()
—Meridiungulata
suborderTrigonostylopoidea
suborderTrigonostylopoidea

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Subor. †Trigonostylopoidea Simpson 1934
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Diagnosis
ReferenceDiagnosis
G. G. Simpson 1934xtinct South American ungulates of very isolated and doubtful position,butperhapsrelatedtotheAstrapotheria. Twopairsofone-lobedlower incisors. P1 present(vestigial)orabsent,PT-iIpresent. Tuskssomewhatlikethose oftrueastrapotheres,butalwaysrooted,relativelylow-crowned,andsmaller. Cheek teethbrachyodont. Uppermolarsusuallytriangular,metaconefoldpresentbutmay be very weak, protoloph continuous but feeble, hypocone rudimentary and excluded fromtrigon,notruemetaloph,nocrista,trigonbasinclosed,broad,shallow. Lower molars imperfectly lophiodont, anterior wing of trigonid poorly developed and short,endingatmidline,notalonidpillar. Infraorbitalforamenmultiple. Palate withposteriormedianprocess. Choanaedividedbybonypartition. Sagittalcrest verylongandpowerful,temporalcrestslittledeveloped. Auditoryregionbroadly expandedandwellexposed. Auditorynotchbroadandopen,post-tympanicprocess practicallyabsent. Tympanicnearlyhorizontal,attachedsuturally,thickandscale- like, not inflated, with deep notch beneath meatus and round carotid evagination on innerside. Mastoidexposedonocciput. Condylarforamenfarfromcondyleand opening into pit or gap between tympanic and basioccipital.