A. laaroussii, including the holotype and unpublished post crania, is housed at the Muséum National d'Histoire Naturelle in Paris, France. A. madagaskarensis Initial discoveries In 1997 through to 1999, fossils of a new archosauromorph were discovered by an international expedition in southwestern Madagascar and were recovered over the following decade. The fossils were found in a single bone bed, referred to as M-28, that was only tens of centimetres thick across a 100 metre stretch of outcrop exposed as an uplifted river terrace not far from the east bank of the Malio River, just outside of the Isalo National Park, north-west of the town of Ranohira and to the east of Sakahara. The locality was from the base of the Middle–Late Triassic Makay Formation, also referred to as Isalo II, a part of the Isalo "Group" in the Morondava Basin. Previously, the formation had been believed to be Early to Middle Jurassic in age, although the earlier discovery of the rhynchosaur Isalorhynchus had revised that estimate to the Middle Triassic. The tetrapod fossils recovered in the 1997–99 expedition confirmed the Isalo II was Triassic in age, but instead suggested a younger Carnian age. The age of the formation has also been correlated to the Santacruzodon Assemblage Zone (AZ) from the Santa Maria Formation in South America based on the shared genera of traversodontid cynodonts, with a similar late Ladinian or early Carnian age. The Santacruzodon AZ has been more reliably dated through radioisotope U—Pb dating, suggesting a maximum depositional age of 237 ±1.5 million years in the early Carnian. The bone bed contained material from almost "a dozen" individuals of varying ages and size, all from a single species. The material was very well preserved, generally preserving the three-dimensional shape of the bones with very little crushing or distortion in some of the specimens. Based on the state of preservation, some of the bones were believed to have been buried rapidly while others were exposed for longer on the surface, where they were weathered, cracked and possibly trampled on before burial. As with A. laaroussii, the teeth and jaws were the first material to be recovered and described from the bone bed. These were initially mistaken to belong two different species based on the difference in tooth shape in the upper and lower jaws, but one of them was recognised as closely resembling A. laaroussii, sharing a keel on the