Tarjadia is an extinct genus of erpetosuchid pseudosuchian, distantly related to modern crocodilians. It is known from a single species, T. ruthae, first described in 1998 from the Middle Triassic Chañares Formation in Argentina. Partial remains have been found from deposits that are Anisian-Ladinian in age. Long known mostly from osteoderms, vertebrae, and fragments of the skull, specimens described in 2017 provided much more anatomical details and showed that it was a fairly large predator. Tarjadia predates known species of aetosaurs and phytosaurs, two Late Triassic groups of crurotarsans with heavy plating, making it one of the first heavily armored archosaurs. Prior to 2017, most studies placed it outside Archosauria as a member of Doswelliidae, a family of heavily armored and crocodile-like archosauriforms. The 2017 specimens instead show that it belonged to the Erpetosuchidae. Etymology The genus name Tarjadia is derived from Sierra de los Tarjados, the closest mountain range to the outcrops of the Los Chañares Formation where remains have been found. The type species T. ruthae was named in honor of Ruth Romer, wife of the American paleontologist Alfred Romer, who led a Harvard expedition to Los Chañares in 1964 and 1965. Ruth went with Alfred on the expedition and was the first woman to work in the locality. History The first remains of Tarjadia from the Chañares Formation were mentioned by Alfred Romer in 1971. He recognized two types of osteoderms from the formation, which he tentatively attributed to the rauisuchian Luperosuchus because of their large size and similar appearance to scutes of other rauisuchians. In 1990, more complete osteoderms were found from the formation, as well as associated vertebrae. Three years later, in Romer's collections at Harvard University, remains of a skull were found in association with an osteoderm that was similar to the ones described in 1971 and 1990. This allowed Tarjadia to be erected as a new genus, distinct from Luperosuchus. Specimens The initial 1998 description of Tarjadia ruthae listed several specimens: PULR (Museo de Paleontologia at Universidad de La Rioja) 603 (holotype): six complete osteoderms, three osteoderm fragments, and at least six fragmentary vertebrae. MCZ 9319: A fragmentary skull roof and braincase, a fragment of the lower jaw, and an osteoderm fragment. MCZ 4076: four osteoderms. In 2016, Ezcurra considered MCZ 4077 (a partial femur and osteoderm fragments), which had previously been referred to Luperosuchus and even used in a study of the