Gracilisuchus

Gracilisuchus (meaning "slender crocodile") is an extinct genus of tiny pseudosuchian (a group which includes the ancestors of crocodilians) from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972. A four-month expedition spanning 1964 and 1965 in the Ischigualasto-Villa Unión Basin of La Rioja Province, Argentina was conducted by Alfred Romer and his colleagues, who consisted of researchers from the Museum of Comparative Zoology (MCZ) at Harvard University. While the first two months of the expedition were unfruitful, excavations near the Chañares River and the Gualo River, soon uncovered specimens belonging to a wide variety of tetrapod groups. Among these was the skeleton of a small suchian archosaur, discovered about north of the Chañares River. The skeleton was stored at the La Plata Museum (MLP), which had supported the expedition, under the specimen number MLP 64-XI-14-11. The specimen has since been transferred to the Museum of Paleontology at the National University of La Rioja (PULR), where it bears the specimen number PULR 08. This specimen, which would become the holotype of Gracilisuchus, consists of a partial skull, an incomplete vertebral column, parts of the scapula and humerus, gastralia, and several associated osteoderms. Several other specimens are mixed in with these remains on the same slab. A vertebral series ("Series A"), originally identified as the tail of Gracilisuchus, has been reassigned to Tropidosuchus. Another series of cervical vertebrae ("Series B") underwent a similar reassignment. A scapula and coracoid overlapping the holotype's limb bones likely belongs to a second Gracilisuchus. There are three ilia, none of which belong to the holotype; one belongs to a specimen of Lagosuchus, another to Tropidosuchus. A right hindlimb and a left femur and tibia have been assigned to Tropidosuchus, and another one has been assigned to Lagosuchus.