Tengrisaurus

History and description

Tengrisaurus starkovi was described in 2017 based on three caudal vertebrae: the holotype ZIN PH 7/13, an anterior vertebra, ZIN PH 14/13, another anterior vertebra, and ZIN PH 8/13, a middle vertebra. A 2021 reassessment referred an additional anterior caudal vertebra, BM 38/7120, and another caudal, ZIN PH 32/13, to the species. In 2025, the first non-caudal element, a posterior cervical vertebra (ZIN PH 31/13), was described and referred to T. starkovi based on similarities to the closely related Dongbeititan. The genus is characterized by strongly procoelous anterior and middle caudal vertebrae with well-developed pre-epipophyses, highly pneumatic neural spines, and solid centra.

Classification

In the 2017 description, Tengrisaurus was recovered as a lithostrotian titanosaur diverging between Rapetosaurus and Trigonosaurus near Saltasauridae. A 2018 study on Volgatitan found similar results, placing Tengrisaurus within a lithostrotian lineage containing Saltasauridae. The 2021 reassessment instead recovered Tengrisaurus as more closely allied with lognkosaurs and Colossosauria, diverging after Epachthosaurus as the sister taxon to Colossosauria.

In 2025, incorporating the cervical vertebra, Tengrisaurus was again recovered diverging after Epachthosaurus, as the sister taxon to a clade formed by Rinconsauria and Lognkosauria within a broadly defined Colossosauria (all titanosaurs closer to Patagotitan than Saltasaurus). Dongbeititan, though anatomically very similar and possibly the closest relative, was recovered outside Titanosauria, likely due to limited available information.