Astrophocaudia (AS-troh-foh-KAW-dee-uh; “Star Seal Tail”) is a genus of titanosauriform sauropod dinosaur that lived during the Early Cretaceous period, about 112 million years ago, in what is now Texas, USA. The name refers to the somewhat star-shaped appearance of its tail chevrons (bones on the underside of the tail vertebrae) and an early, mistaken idea that some of its bones belonged to a seal (“phoca”). Fossils of Astrophocaudia were discovered in the Paluxy Formation of the Trinity Group. The genus was officially named in 2012, though the fossils were known for many years prior.

Description and Classification

Astrophocaudia was a large, four-legged herbivore with a long neck and a long tail, typical of sauropod dinosaurs. Estimates based on the incomplete fossil material suggest it could have reached lengths of around 15 to 18 meters (approximately 50 to 60 feet) and weighed many tons. The known fossils include vertebrae from the back and tail, ribs, and chevron bones.

Astrophocaudia belongs to the group Sauropoda, specifically within the clade Titanosauriformes. This means it was related to the giant titanosaurs that became widespread later in the Cretaceous period. Its classification places it as a somphospondylan, a group characterized by spongy bone tissue in their vertebrae. It helps bridge a gap in our understanding of how titanosaurs evolved from earlier sauropods. It is considered more closely related to dinosaurs like Sauroposeidon than to earlier North American sauropods like Brachiosaurus.

Distinguishing Features

Astrophocaudia is identified by a unique combination of features found in its vertebrae, particularly those of the tail:

• The tail vertebrae (caudal vertebrae) are strongly procoelous, meaning they are concave on the front surface and convex on the back surface, allowing for flexible tail movement. This is a common feature in titanosaurs.
• The chevron bones from the middle to the end of the tail have a somewhat star-like shape when viewed from the front or back. This is due to well-developed projections of bone.
• The neural spines (the bony projections sticking up from the vertebrae) on the anterior (front) part of the tail are relatively tall.
• Internal bone structure of the vertebrae shows a camellate, or highly chambered, texture, which would have helped to lighten the skeleton without sacrificing strength.

Paleoenvironment and Diet

Astrophocaudia lived in what is now Texas during the Early Cretaceous. The Paluxy Formation, where its fossils were found, represents a coastal plain environment with rivers, floodplains, and possibly deltas. The climate was likely warm and humid, supporting a rich ecosystem. This ancient environment was home to a variety of other dinosaurs. Astrophocaudia would have shared its habitat with the large predatory theropod Acrocanthosaurus, the ornithopod Tenontosaurus, and armored dinosaurs like Sauropelta. Other sauropods like Pleurocoelus (now considered a dubious name by some, with material potentially belonging to Astrophocaudia or similar animals) were also present in the region.

As a sauropod, Astrophocaudia was an herbivore. Its long neck would have allowed it to browse on vegetation at various heights, likely feeding on conifers, cycads, and ferns, which were common plants during the Early Cretaceous period.

Significance and Ongoing Research

Astrophocaudia is significant because it adds to our knowledge of sauropod diversity in North America during the Early Cretaceous, a time when the types of sauropods on the continent were changing. It provides clues about the early evolution and spread of titanosauriform sauropods, the group that would later include some of the largest land animals ever to live. The study of Astrophocaudia helps paleontologists understand the transition from earlier Jurassic sauropod faunas to the later Cretaceous ones.

Ongoing research relies on the discovery of more complete fossil material to better understand Astrophocaudia’s full anatomy, size, and relationships to other sauropods. Continued study of the Trinity Group fossils also helps create a more detailed picture of the ancient ecosystems of Early Cretaceous Texas and the interactions between different dinosaur species. Its classification and exact position within the sauropod family tree are subjects of ongoing study as new analytical methods and fossil discoveries emerge.