Giant 'Star Lizard': Newly Identified Sauropod Unearthed as the Largest and Last of Its Kind in Argentina

Scientists have recognized a recently discovered sauropod species, the largest in its family and among the last survivors. Initially found in 2012, Sidersaura marae fossils required multiple years of excavation in Argentina's Neuquén Province.

The study, titled "The last of the oldies: a basal rebbachisaurid (Sauropoda, Diplodocoidea) from the early Late Cretaceous (Cenomanian-Turonian) of Patagonia, Argentina" published in Historical Biology, details the process of recovering parts from four individual dinosaurs.

'Star Lizard': Unraveling Late Cretaceous Mysteries in the Muddy River Vicinity

Researchers found the dinosaur fossils in the muddy vicinity of a river where the recently discovered sauropods likely met their end. While scavengers and water displaced some bones, many were preserved. Remarkably, one of the newfound sauropods lay alongside the giant meat-eating dinosaur, Meraxes gigas, unveiled in 2022, while the remaining three were found 65 feet away.

Dating back to 93 million to 96 million years ago, during the late Cretaceous period, Sidersaura marae's fossils capture the era's final chapter before a catastrophic asteroid strike wiped out non-avian dinosaurs. These sauropods, weighing up to 16.5 tons and measuring 65 feet in length, defy the typical size range of rebbachisaurid sauropods, sparking inquiries into their unusual growth.

Lead author Lucas Nicolás Lerzo, a doctoral student at Maimónides University in Argentina, sees this discovery as a gateway to exploring how these creatures achieved such immense sizes.

Sidersaura marae earned its name from the distinct star-like shape of its haemal arches, and bony structures in the tail. The term "Sidersaura" combines "sider," derived from the Latin word for star, with the Greek word "saura," denoting "lizard" or "reptile."

In their investigation, Lerzo and his team explored the evolutionary ties between S. marae and other rebbachisaurids. Notably, the study highlighted S. marae's closer kinship with earlier members of the group from the early Cretaceous, rather than its late Cretaceous counterparts.

This discovery offers fresh insights into the evolution of the rebbachisaurid family, particularly during the period leading to their extinction around 90 million years ago, making S. marae one of the final members of this ancient lineage.

Star Lizard Characteristics

Studying multiple specimens and their anatomical overlaps facilitated the correlation and enhanced understanding of the distinctive features of the recently discovered sauropod dinosaur.

Notably, this dinosaur stands out due to the unique star-shaped configuration of its hemal arches, setting it apart from its counterparts. Additionally, Sidersaura marae exhibits robust skull bones, a departure from the characteristics observed in its closest relatives within the rebbachisaurid family.

Moreover, S. marae belongs to Rebbachisauridae, a sauropod family with unique duck-like faces and distinctive teeth. These herbivores thrived on ground-level vegetation and disappeared 90 million years ago in an extinction event. These species are known from fragmented fossils across continents, featuring tooth batteries similar to hadrosaurs and ceratopsians.

Further differentiation is evident in the skull's frontoparietal foramen, a feature absent in other rebbachisaurids. This particular trait aligns S. marae more closely with dicraeosaurids, a sauropod family known for neck and back spines. The identification of an early species during the Cenomanian-Turonian period, close to the extinction phase of the group, suggests a more intricate evolutionary history for Rebbachisauridae than previously assumed.

Dr. Lerzo, a paleontologist at Fundación Azara - Universidad Maimónides and CONICET, delved into studying these bones in 2017, uncovering distinct features setting S. marae apart, particularly its robust hind limbs, likely evolved to support its massive weight.