Description and Classification

Like other sauropods, Pleurocoelus would have had a long neck, a long tail, a relatively small head, and a bulky body supported by four strong, pillar-like legs. It was a plant-eating dinosaur. Most fossils identified as Pleurocoelus come from young or smaller individuals, making it difficult to determine its maximum adult size. It is generally thought to have been a medium-sized sauropod for its time, perhaps reaching lengths of 9 to 18 meters (30 to 60 feet), though this is an estimate.

Pleurocoelus is classified as a member of the Sauropoda, and more specifically, within the group Macronaria. Macronarians are a large group of sauropods that includes famous giants like Brachiosaurus and Argentinosaurus. The exact position of Pleurocoelus within Macronaria is uncertain due to the fragmentary fossils. It is often discussed in relation to Astrodon johnstoni, another sauropod from the same time and region (Maryland). Astrodon was named earlier, based on teeth, and some paleontologists believe that Pleurocoelus might actually be the same dinosaur as Astrodon. If this is true, the name Astrodon would take priority.

Distinguishing Features

Because Pleurocoelus is considered a doubtful name by many, defining its unique features is challenging. However, based on the fossils historically assigned to it, some characteristics include:

• Large hollow spaces (pleurocoels) on the sides of its back and neck vertebrae, which is the feature its name comes from.
• Teeth that were somewhat spoon-shaped or peg-like, suitable for stripping leaves from plants.
• The juvenile specimens on which the genus was largely based show typical sauropod limb bone proportions for young animals.

Paleoenvironment and Diet

Fossils linked to Pleurocoelus are found in rock formations like the Arundel Clay in Maryland and the Trinity Group (including the Paluxy and Twin Mountains Formations) in Texas. During the Early Cretaceous, these areas were warm and humid, with environments like river floodplains, forests, and coastal plains. Pleurocoelus would have shared its world with other dinosaurs. In Texas, this included the large meat-eating dinosaur Acrocanthosaurus and the plant-eating ornithopod Tenontosaurus. In Maryland, it lived alongside other dinosaurs known from the Arundel Formation.

As a herbivore, Pleurocoelus would have eaten plants. Its long neck would have allowed it to browse on leaves and branches high up in trees, possibly consuming conifers, cycads, and ferns, which were common plants during that time.

Significance and Ongoing Research

Pleurocoelus played an important role in the early history of dinosaur discovery in North America. The material identified as Pleurocoelus, particularly that from Maryland (which is often linked with Astrodon), helped paleontologists understand the kinds of dinosaurs that lived on the continent during the Early Cretaceous. Astrodon johnstoni, which might be the same animal as Pleurocoelus, is honored as the official state dinosaur of Maryland.

The main focus of ongoing research regarding Pleurocoelus is to clarify its identity and its relationship to other sauropods, especially Astrodon. Because the original fossils are limited, it is difficult to definitively assign new fossil finds to Pleurocoelus. Famous sauropod trackways in Texas, like those at Dinosaur Valley State Park in Glen Rose, were once attributed to Pleurocoelus, but are now thought by many to have been made by larger sauropods such as Sauroposeidon. Studying these fossils and trackways helps scientists piece together a more accurate picture of sauropod diversity and behavior in Early Cretaceous North America.