Barrosasaurus

Barrosasaurus casamiquelai was a Late Cretaceous Patagonian titanosaur known from three dorsal vertebrae. Few bones survive, but they come from one horizon, represent different regions of the back and preserve comparable anatomy. The genus is recognised by neural-arch laminae, not an estimated size.

Quick facts

Discovery at Sierra Barrosa

Leonardo Salgado and Rodolfo Coria named the genus in 2009. The holotype, MCF-PVPH-447, is held at the Carmen Funes Museum in Plaza Huincul. It consists of three large incomplete vertebrae interpreted as approximately the third, the seventh or eighth, and the ninth or tenth dorsals.

The bones were found together in one horizon of reddish fluvial sandstone at Sierra Barrosa in Neuquén Province. The rocks belong to the Anacleto Formation and date to the early Campanian stage of the Late Cretaceous. The genus name records Sierra Barrosa, while the species honours Argentine researcher Rodolfo Casamiquela.

Vertebrae as an anatomical identity card

Sauropod neural arches and their tall spines are braced by systems of thin bony plates called laminae. Their positions change along the back, so the authors first estimated where each fossil belonged by comparing it with more complete titanosaur vertebral series.

The anterior vertebra bears strong sheets linking the neural spine with the front articular processes. Paired spinodiapophyseal laminae occur on the two posterior bones, with the anterior branch stronger than the posterior one. On the rearmost vertebra that branch divides again. An unusually long portion of neural spine rises above the lateral wing-like processes. This combination, rather than size by itself, separated the holotype from other known titanosaurs.

Systematic position

The original description securely assigned Barrosasaurus to Titanosauria. Three vertebrae do not preserve enough characters to test every narrower branch, so a particular family or closest relative should not be presented as settled. Laminae may also vary both along one animal’s back and through growth.

Patagonia contains many other sauropods, but geographic proximity does not establish identity or ancestry. Barrosasaurus is not simply a juvenile of a larger named genus, and similarity to a distant titanosaur cannot override the diagnostic bones and geological age.

What three bones cannot reveal

The vertebrae are large, but no complete spine or limb bones are known. Total length and body mass have therefore not been measured. Even the positions of the three vertebrae are given as ranges, while the neck, tail and trunk proportions in a life restoration necessarily borrow the general titanosaur plan.

Teeth, jaws and gut contents are absent. Herbivory follows from sauropod relationships, but particular plants and feeding height cannot be identified. No skin, osteoderms, eggs or trackway can presently be connected with the genus.

The Anacleto environment

Red sandstones record a terrestrial river system. The broader Anacleto Formation preserves dinosaurs, crocodyliforms and turtles, while Auca Mahuevo is famous for titanosaur eggs. Those eggs cannot be assigned to Barrosasaurus unless embryos preserve anatomical features diagnostic of the genus.

The three vertebrae remain valuable evidence for early Campanian titanosaur diversity. They show how a small sample can be informative when it comes from a clear geological context and carries features that can be compared across the skeletons of related animals. Nullotitan illustrates a better-limbed but still incomplete Patagonian titanosaur. Both profiles show why “large” is not a precise body measurement.

Evidence, inference and reconstruction