Description and Classification

Pelecanimimus was a relatively small and lightly built dinosaur, measuring about 2 to 2.5 meters (6.5 to 8 feet) in length and weighing an estimated 15 to 25 kilograms (33 to 55 pounds). Like other ornithomimosaurs, often called “ostrich-mimic” dinosaurs, it had a slender body, a long neck, long legs adapted for running, and a long tail for balance. Its head was small and elongated, with a particularly long and pointed snout.

One of the most unusual features of Pelecanimimus was its teeth. Unlike most later ornithomimosaurs, such as Struthiomimus or Gallimimus, which were toothless, Pelecanimimus possessed a very large number of small teeth – around 220 in total. These teeth were tiny, unserrated (lacking saw-like edges), and present in both the upper and lower jaws. The type specimen of Pelecanimimus is also famous for its exceptional preservation, which includes impressions of soft tissues. These include the gular pouch under its throat and a small, fleshy or keratinous crest on the back of its head. The skin impressions indicate it had smooth, unscaled skin, at least in the areas preserved.

Pelecanimimus is classified as a basal (early or primitive) member of the Ornithomimosauria. This group includes dinosaurs known for their bird-like features and likely fast running abilities. The presence of teeth in Pelecanimimus is a primitive trait, suggesting it represents an early stage in ornithomimosaur evolution before the group became predominantly toothless. It shares some features with another early ornithomimosaur, Harpymimus, which also retained teeth, though fewer than Pelecanimimus.

Distinguishing Features

Pelecanimimus can be distinguished by several unique characteristics:

• An exceptionally high number of tiny teeth (approximately 220), which is unique among ornithomimosaurs.
• The preserved impression of a gular pouch (throat pouch) located beneath its lower jaw, similar to that seen in pelicans.
• Evidence of a small, soft-tissue crest on the back of its head.
• Relatively short hands for an ornithomimosaur, with the three fingers being of similar length. Unlike many theropods, its metacarpals (hand bones) were not fused.
• It is one of the earliest and most complete ornithomimosaurs discovered, providing key information about the group’s early anatomy.

Paleoenvironment and Diet

The fossils of Pelecanimimus were found at the Las Hoyas site in Spain. During the Early Cretaceous, this area was a subtropical wetland environment, characterized by shallow lakes, ponds, and abundant vegetation. The ecosystem supported a diverse array of life, including various fish, crustaceans (like shrimp), insects, amphibians, lizards, crocodiles, pterosaurs, and other dinosaurs, such as the iguanodontian Mantellisaurus and the small theropod Concavenator.

The diet of Pelecanimimus is a subject of scientific interest. Its numerous small, unserrated teeth were not suited for tearing flesh from large prey. Instead, they might have been used to grip small, slippery animals. The gular pouch could have been used to temporarily store food. It is hypothesized that Pelecanimimus may have waded in the shallow waters of its habitat, using its long snout and many teeth to catch small fish, crustaceans, or insects, perhaps by filter-feeding or scooping them up. Its diet was likely omnivorous, including small animals and possibly some plant matter. The sharp, slender claws on its hands might also have been used to help capture small prey or manipulate food items.

Significance and Ongoing Research

Pelecanimimus is a very significant dinosaur discovery for several reasons. As one of the earliest known ornithomimosaurs, it provides crucial evidence about the initial stages of evolution within this group, particularly the transition from toothed ancestors to the toothless condition seen in later members. The exceptional preservation of soft tissues, such as the gular pouch and skin crest, is extremely rare in the fossil record and offers a unique glimpse into the life appearance and potential behavior of these animals. The gular pouch was the first such structure to be definitively identified in a non-avian theropod dinosaur.

Ongoing research on Pelecanimimus continues to focus on understanding its anatomy and lifestyle more thoroughly. Scientists study the preserved soft tissues to learn more about their structure and function. Detailed comparisons with other early ornithomimosaurs help to refine its evolutionary relationships within the dinosaur family tree. Researchers are also interested in its specific feeding mechanisms and how its unique dental structure and gular pouch were used in the rich wetland ecosystem of Las Hoyas. The study of Pelecanimimus helps paleontologists piece together the diversity and ecological roles of dinosaurs in the Early Cretaceous period.