Trachelosaurus

Trachelosaurus is an extinct genus of lizard-like early archosauromorph reptiles in the family Trachelosauridae.^[1] It was originally described as a dinosaur^[2] until it was redescribed as a "protorosaur" reptile by Robert L. Carroll in 1988.^[3] The type species, T. fischeri, was described by F. Broili & E. Fischer in 1917^[2] based on remains found in the Solling Formation (Buntsandstein), Bernburg, Germany.^[4] A 2024 redescription identified Trachelosaurus as a long-necked and presumably aquatic reptile closely related to Dinocephalosaurus from the Guanling Formation of China.^[5]

Size compared to a human

Trachelosaurus Temporal range: Early Triassic, 247–242 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype specimen
Reconstructed skeleton of the holotype
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Family:	†Trachelosauridae
Genus:	†Trachelosaurus Broili & Fischer, 1917
Species:	†T. fischeri
Binomial name
†Trachelosaurus fischeri Broili & Fischer, 1917

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:^[5]

Tanysauria	Jesairosaurus Trachelosauridae Austronaga Pectodens Fuyuansaurus Trachelosaurus Gracilicollum Dinocephalosaurus Tanystropheidae Augustaburiania Luxisaurus Macrocnemus bassanii Macrocnemus fuyuanensis Macrocnemus obristi UFRGS-PV-492-T Amotosaurus Langobardisaurus Raibliania Tanystropheus spp. Sclerostropheus Ozimek Tanytrachelos