ON PNEUMATIC STRUCTURES IN VERTEBRAE OF A DICRAEOSAURID DINOSAUR (SAUROPODA, DIPLODOCOIDEA) FROM THE MULICHINCO FORMATION (VALANGINIAN, LOWER CRETACEOUS), NEUQUÉN BASIN, ARGENTINA

WINDHOLZ, G.J.; CORIA, R.A.; ZURRIAGUZ V.L.

Corrientes

Congreso; XXXII Jornadas Argentinas de Paleontología de Vertebrados; 2018

Asociación Paleontológica Argentina

Dicraeosauridae is a family of small to medium-size sauropod dinosaurs that includes the genera Dicraeosaurus (Janensch, 1914), Amargasaurus (Salgado and Bonaparte, 1991), Brachytrachelopan (Rauhut et al., 2005), Amargatitanis (Apesteguía, 2007), Suuwassea (Harris and Dodson, 2004), and possibly Dyslocosaurus (McIntosh et al., 1992) and Dystrophaeus (Cope, 1877). Traditionally, it has been argued that the dicraeosaurid postcraneal skeleton represents a reduction of the pneumaticity compared with other Diplodocoidea. In fact two isolated and fragmentary cervical vertebrae of Dicraeosaurus sp. had been examined by using computed tomography (CT scanning), in which procamerate pneumatization type was recognized. Here we report preliminary results obtained from CT scanning vertebral elements of a new dicraeosaurid taxon from Patagonia. We have recognized the first record of camerate internal structure type in the dicraeosaurid cervical vertebrae (MLL-Pv-004 and MLL-Pv-002), represented by lateral pneumatic foramina that open into a large camera that occupiesmost of the centrum. Also, CT scanned images in both dorsal (MLL-Pv-005) and caudal (MLL-Pv-016) vertebrae show acamerate pattern, lacking fossae invading the respective centra. The cervical vertebrae of diplodocids such as Apatosaurusand Diplodocus are polycamerate, whereas the dorsal vertebrae of the rebbachisaurid Katepensaurus are camellate. Also, in the rebbachisaurid Tataouinea the caudal vertebrae and appendicular skeleton are invaded by pneumatic structures. In summary, we provide the first record of camerate internal structure type in dicraeosaurid cervical vertebrae, and confirmthe relative reduction of pneumaticity in dicraeosaurid dorsal and caudal vertebrae with respect to other diplodocoid taxa.