Vertebral pneumaticity among cervico-dorsal transition of non-Eusauropoda Sauropodomorpha

APALDETTI, C.; MARTINEZ, R.N.; POL, D

Congreso; RCAPA; 2018

Pneumatic structures among presacral vertebrae are present in the dorsal series of non-Sauropoda Sauropodomorpha (e.g., Eucnemesaurus, Aardonyx) and in the cervico-dorsal transition of Gravisauria and more derived Eusauropoda. Recently were known two non-eusauropod sauropodomorphs (the lessemsaurids Lessemsaurus and Ingentia) with pneumatic struc- tures among their cervico-dorsal vertebral transition, which represent the earliest sauropodomorphs with pneumatic cer- vical vertebrae and/or cervico-dorsal transition. Here we present a new Sauropodiformes specimen (PVSJ 908) from the Late Triassic Quebrada del Barro Formation (Marayes-El Carrizal basin, Northwestern Argentina) with novel pneumatic structures in its cervico-dorsal vertebrae. This new pneumatic pattern includes the presence of deep fossae with internal subfossae (= internal chambers) on the pre and postzygapophyseal centrodiapophyseal fossa (prcdf and pocdf) on the posterior cervical (C9-10) and anterior dorsal (D1-5) vertebrae, which are unambiguously identified as pneumatic in origin. The presence of invasive pneumatic complex ?fossae within fossae? observed among lessemsaurids and in the new sauropodiform (PVSJ 908) show a new pattern of pneumatization in an unprecedented region (i.e., prcdf) throughout the presacral region, and an improved pneumatic system among the cervico-dorsal transition that evolved well before the origin of Eusauropoda. Because only cervical and abdominal air sacs and lungs are able to produce pneumatic diverticula that invade the vertebrae, the presence of a sophisticated pneumatic complex on the neck of these taxa suggests that a cervical air sac system, and hence an improved avian-style respiratory system, were well developed already at the base of Sauropoda.