Obscure by name: solving the enigma of Chelytherium obscurum, the first described Triassic turtle

The material historically referred to Chelytherium obscurum is exceptional for a number of reasons. It is the first described Triassic turtle, the oldest testudinate among the British palaeontological collections, and it is one of the oldest testudinates in the world. Nevertheless, after its establishment in 1863, the taxon remained in a taxonomic limbo and was eventually almost forgotten. However, the recent reconsideration of proterochersid turtles, with improved understanding of their anatomy, allows reassessment of Chelytherium obscurum as a member of the Proterochersidae, subjectively synonymous with Proterochersis robusta. Despite nomenclatural priority, in accordance with the suggestions of previous authors, the name Proterochersis robusta is endorsed to be upheld.