Brachytrachelopan

Brachytrachelopan is a genus of short-necked sauropod dinosaur from the Late Jurassic (Oxfordian to Tithonian) of Argentina. The holotype and only known specimen (Museo Paleontológico Egidio Feruglio MPEF-PV 1716) was collected from an erosional exposure of fluvial sandstone within the Cañadón Calcáreo Formation on a hill approximately north-northeast of Cerro Cóndor, Chubut Province, in west-central Argentina, South America. Though very incomplete, the skeletal elements recovered were found in articulation and include eight cervical, twelve dorsal, and three sacral vertebrae, as well as proximal portions of the posterior cervical ribs and all the dorsal ribs, the distal end of the left femur, the proximal end of the left tibia, and the right ilium. Much of the specimen was probably lost to erosion many years before its discovery. The type species is Brachytrachelopan mesai. The specific name honours Daniel Mesa, a local shepherd who discovered the specimen while searching for lost sheep. The genus name translates as "short-necked Pan", Pan being the god of the shepherds.

== Description == thumb|left|Life restoration of Brachytrachelopan mesai thumb|left|Size comparison of the Dicraeosauridae members. Brachytrachelopan is orange. This taxon's very short neck (approximately 40% shorter than other dicraeosaurids and the shortest of any known sauropod) is evidence that this lineage specialized to fill an ecological niche not exploited by other members of this infraorder. Small for a sauropod, Brachytrachelopan measured in length and in body mass. Rauhut et al. (2005, 670) note that the high degree of fusion present between the preserved neural arches and their respective centra, as well as fusion between the sacral centra, sacral neural arches, and sacral neural spines is evidence that the holotype does not represent a juvenile animal. Hence, the small body size is not a relic of ontogeny.