Trachelosaurus

Trachelosaurus is an extinct genus of lizard-like early archosauromorph reptiles in the family Trachelosauridae. It was originally described as a dinosaur until it was redescribed as a "protorosaur" reptile by Robert L. Carroll in 1988. The type species, T. fischeri, was described by F. Broili & E. Fischer in 1917 based on remains found in the Solling Formation (Buntsandstein), Bernburg, Germany. A 2024 redescription identified Trachelosaurus as a long-necked and presumably aquatic reptile closely related to Dinocephalosaurus from the Guanling Formation of China.

Classification
In their 2024 redescription of Trachelosaurus, Spiekman and colleagues recovered it in a clade with the Chinese Dinocephalosaurus in a clade previously named Dinocephalosauridae in 2021. However, the principle of priority instructs that the name Trachelosauridae, which was first erected as a monotypic clade for Trachelosaurus, should be used instead. The results of their phylogenetic analyses are shown in the cladogram below: