A reevaluation of the basal turtle Indochelys spatulata from the Early–Middle Jurassic (Toarcian–Aalenian) of India, with descriptions of new material

BACKGROUND: Indochelys spatulata is an extinct turtle from the Early to Middle Jurassic Kota Formation of the Pranhita–Godavari Gondwana basin, India. The holotype and previously only known specimen is a partially eroded shell that had been collected near Kota village, north of Sironcha, in Maharashtra State. Phylogenetic analyses have consistently suggested placement at the base of the clade Mesochelydia. METHODS: We here figure and describe the holotype of Indochelys spatulata and two new specimens, which were collected from the Kota Formation near Kistapur village, Telengana State, about 60 km NW from the type locality. We furthermore explore the relationships of this fossil turtle by updating its scoring based on all available material in the most recent analysis of basal turtle relationships. RESULTS: The revision of the holotype of Indochelys spatulata provides minor adjustments to the morphology of this specimen, in particular recognition of a transverse break across the carapace, presence of only eight neurals, of which the eight is octagonal, and presence of a pathological element located between neurals VII and VIII. The new material provides new anatomical insights, in particular presence of a broad cervical, a vertebral V that inserts deeply into vertebral IV, narrow pleurals within increasingly short posteromedial contacts with the vertebrals towards the posterior, at least three pairs of musk duct foramina, and numerous insights into the morphology of the girdles and stylopodium. In combination, all material allows affirming the validity of Indochelys spatulata with confidence. The phylogenetic analysis affirms the placement of Indochelys spatulata as a basal mesochelydian, but cannot resolve its relationships relative to the roughly coeval Condorchelys antiqua and Kayentachelys aprix.