Genus: Cyrtlatherium FREEMAN, 1979
Etymology: Cyrtia, Anglo-Saxon proper name, root of “Kirtlingon” and Greek, therion, “beast, mammal”: Kirtlington mammal.
= Simpsonodon KERMACK, LEES, LEES, & MUSSETT, 1987
Etymology: In honor of the late Professor George Gaylord Simpson for his outstanding contributions to the study of Mesozoic Mammals, Simpson and Greek, odon, "tooth."

Species: canei FREEMAN, 1979
Etymology:

Holotype: FM/K 11

Locality: Old Cement Works Quarry, (Washford Quarry), Kirtlington, Ordnance Survey Grid Reference SP 495200, Oxfordshire County, England, Southern United Kingdom.

Horizon: Kirtlington Mammal bed, near base of the Forest Marble.

Biostratigraphy: Oppelia aspidioides Zone.

Age: Upper Bathonian Stage, upper middle Dogger Epoch, Middle Jurassic.

Material: Right lower molar.

Referred material:

FM/K 38: Right lower molar.

= Simpsonodon oxfordensis KERMACK, LEES, LEES, & MUSSETT, 1987
Etymology: Refers to the County from which the type specimen was found.

Holotype: University Collage, London-Department of Zoology-specimen number J. 100

Locality: Old Cement Works Quarry, (Washford Quarry), Kirtlington, Ordnance Survey Grid Reference SP 495200, Oxfordshire County, England, Southern United Kingdom.

Horizon: Kirtlington Mammal bed, near base of the Forest Marble.

Biostratigraphy: Oppelia aspidioides Zone.

Age: Upper Bathonian Stage, upper middle Dogger Epoch, Middle Jurassic.

Material: Fragment of right ramus of lower jaw with 3 postcanine teeth.

Paratypes:

J. 229, J. 232, J. 251, J. 462, J. 682: Lower molariform teeth.

J. 147, J. 227, J.249, J.747, J. 783: Upper Molariform teeth.

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Species: spendens (KUHNE, 1968)
Etymology:

Holotype:

Locality:

Horizon:

Biostratigraphy:

Age:

Material:

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Species: sibiricus emend AVERIANOV, LOPATIN, KRASNOLUTSKII & IVANTSOV, 2010
= Simpsonodon sibiricus AVERIANOV, LOPATIN, KRASNOLUTSKII & IVANTSOV, 2010
Etymology: In reference to Siberia, where the specimens were found.

Holotype: PIN 5087/5

Locality: Berezovsk Quarry, 2 km south of Nikol'skoe village, Sharypovo District, Krasnoyarsk Territory, Siberia, Asian Russia.

Horizon: Upper part of the Itat Formation.

Biostratigraphy:

Age: Bathonian Stage, upper middle Dogger Epoch, Middle Jurassic.

Material: A left dentary fragment with three last molariform teeth, the alveolus for a more anterior tooth, and the base of the coronoid process.