Genus: Mesenosaurus EFREMOV, 1940
= Mesonosaurus IVAKHENKO & KURZANOV, 1979 (sic)
Etymology:

Species: romeri EFREMOV, 1940
Etymology: In honor of Alfred S. Romer.

Holotype: PIN 158/1

Locality: Kimja River, an affluent of the Mezen River, Archangel Province, European Russia.

Horizon:

Biostratigraphy: Zone III.

Age: Lower Part of the Kazanian Substage, Wodian-lower Capitanian Stage, Guadelupian Stage, Lower Zechstein Epoch, Early Late Permian.

Material: Skull.

Old skull reconstruction.The skull is dorsally/ventrally crushed.

 

New reconsturction

 

Referred material:

IVAKHENKO, 1991

Numbers: Not given: 20 specimens, skulls, and skeletons.

REISZ, 1997

Mezen River basin of northern Russia. REISZ is conisdered to be a pelycosaur similar to Mycterosaurus.

REISZ & BERMAN, 2001

PIN 3586/8a: Partial skull of a large individual.

PIN 3706/11, 3706/15: Partial skulls of juveniles.

SGU 1-4V/1558: Partial skull similar in size to holotype.

IVAKHNENKO, 2008b

Locality: Glyadnaya Shchel’ya locality, Mezenskii District, Arkhangelsk Region, European Russia.

Horizon: Krasnoshchel’ya Formation, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material: Not given.

 

Locality: Ust’Peza (Ust-Pyoza), Arkhangelsk Region, Mezenskii (Mezen) District, Arkhangel'sk Region, Russia.

Horizon: Biarmin Series, Urzhumina Stage, Urzhumian Horizon, Upper Kimzha beds.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Numbers: Not given:

 

Locality: Peza-1 (Pyoza-1), Peza River, right tributary of Mezen' River, Arkhangelska Region, Mezenskii (Mezen) District, European Russia.

Horizon: Biarmian Series, Upper Kimzha beds, Urzhumian Stage, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Lopingian Subepoch, upper Zechstein Epoch, Late Permian.

Material:

Numbers: Not given:

 

Locality: Ust’-Nyafta settlement, right tributary of Mezen' River, Peza River, Arkhangel'sk Region, European Russia.

Horizon: Leshukonsk Member, Krasnoschelsk Formation, Biarmian Series, Upper Kimzha beds, Urzhumian Stage, Upper Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Upper Guadelupian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Numbers: Not given:

 

Locality: Ust-Vashka Locality, Leshukonskii District, Arkhangelsk Region, European Russia.

Horizon: Krasnoshchel’ya Formation, Biarmian Series, Urzhumian Stage, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Numbers: Not given:

 

Locality: Nyisagora locality, 4543/n, on the Mezen River, near the juction with the Vashka River, Leshukonskii District, Arkhangelsk Region, European Russia.

Horizon: Biarmian Series, Urzhumian Stage, Urzhumian Horizon, Zone II.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Earliest early Tatarian Age, Guadelupian Stage, Middle Zeichstein Epoch, Middle Permian.

Material:

Numbers: Not given:

 

Locality: Belukur’e locality, Mezenskii District, Arkhangelsk Region, European Russia.

Horizon: Biarmian Series, Krasnoshchel’ya Formation, Urzhumian Stage, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Numbers: Not given:

 

Locality: Kosmogorodsko'e Locality, Mezenskii District, Arkhangelsk Region, European Russia.

Horizon: Biarmian Series, Urzhumian Stage, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Number: Not given:

 

Locality: Dorogaya Gora Locality, Mezenskii District, Arkhangelsk Region, European Russia.

Horizon: Biarmian Series, Urzhumian Stage, Urzhumian Horizon.

Biostratigraphy: Mezen Faunal Assemblage.

Age: Lower Tatarian Age, Capitanian Stage, Middle Zechstein Epoch, Late Middle Permian.

Material:

Number: Not given:

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Species: efremovi MAHO, GEE & REISZ, 2019
Etymology: In honor of the famous Russian palaeontologist Ivan Efremov, who erected the genus, and is recognised as one of the leaders in the field in his country.

Holotype: OMNH 73209

Locality: Fort Sill, OMNH Locality V51, Dolese Brothers limestone quarry at Richards Spur, Fissure Fills, just west of U.S. Highways 62 & 281, 10.5 miles south of Apache, 6 miles north of Fort Sill, SW 1/2, Sec. 31, T4N, R11W, Comanche County, Oklahoma.

Horizon: Wellington Formation (Garber Formation), Summer Group, Arbuckle limestone, (Probably equivalent to the Arroyo Formation of Texas).

Biostratigraphy:

Age: Leonardian Stage, Lower Rotliegendes Epoch, Early Permian.

Material: Nearly complete skull and mandible.

Refrred material:

OMNH 73500: A nearly complte skull and mandibles.

OMNH 73208: Nearl comlete skull and left mandible.