GASTROLITHS PRESERVED ON A BASAL SAUROPODOMORPHA FROM THE RHAETIAN-HETTANGIAN QUEBRADA DEL PUMA FORMATION (MARAYES-EL CARRIZAL BASIN) SAN JUAN PROVINCE, ARGENTINA

APALDETTI, CECILIA; MARTINEZ, RICARDO NESTOR

Trelew

Jornada; Jornadas Argentina de Paleontología; 2022

MEF

Gastroliths (stomach stones) are hard object within the digestive tract of many vertebrate animals that help to grind food in gastric digestion. The presence of a hypothetical avian-style gastric mill has been reported but also questioned among herbivorous sauropodomorph dinosaurs. The PVSJ 1108 is a partially preserved articulated sauropodomorph skeleton found in the Rhaetian-Hettangian Quebrada del Puma Formation (Marayes-El Carrizal Basin, southeastern San Juan Province). It preserves articulated antero-mid dorsal vertebrae, dorsal ribs, left humerus, radius, ulna and almost complete manus. Additionally, PVSJ 1108 preserves a claster of approximately forty small and medium size (2 to 5cm) stones in the abdominal region. The stones are sub-rounded with polished surface, surrounding by ribs and dorsal vertebrae. The fine-grained sediments containing the specimen are devoid of similar clasts. On the basis of sedimentological and taphonomical evidences, further the large size and number of stones, the claster accumulated in the abdominal cavity is identified here as a group of gastroliths. Considering the size of the preserved postcranial elements, the relation between the assumed masticatory apparatus size and the size of the stones preserved in the abdominal region, it suggests that they were ingested as a result of lithophagy behavior, rather than accidental swallowing. Gastroliths have been occasionally reported in non-avian dinosaurs and this represents the second record among basal forms of Sauropodomorpha, together to Massospondylus from South Africa. Furthermore, it is the first record of gastroliths among non-sauropod sauropodomorphs outside South Africa, providing new information on the biology and evolutionary history of Sauropodomorpha during early Mesozoic of Pangea.