Pulaosaurus qinglong

Pulaosaurus qinglong is a small-bodied, basal neornithischian dinosaur from the Early Cretaceous (Aptian) of northeastern China. It was discovered in the Yixian Formation of Liaoning Province and described in 2024. The genus name derives from “Pulao” (蒲牢), a dragon-like creature in Chinese mythology known for its loud voice, alluding to the dinosaur’s phylogenetic proximity to other small herbivorous ornithischians. The species name refers to Qinglong Manchu Autonomous County, the area where the fossil was found.

This taxon contributes to the growing diversity of Early Cretaceous neornithischians in East Asia and provides new insights into the anatomy, ontogeny, and early evolutionary history of small-bodied ornithischians in the Jehol Biota.

Geographic Coordinates

Fossil locality: Dawangzhangzi, Qinglong County, Hebei Province, China

Physical Characteristics

The holotype of Pulaosaurus qinglong (IVPP V30936) is a nearly complete, articulated skeleton of a juvenile individual, preserved in right lateral view. It includes:

• Nearly complete skull (length: 82 mm / 3.2 in)
• 21 presacral vertebrae
• Three sacrals
• 29 caudal vertebrae
• Complete pelvic girdle
• Partial pectoral girdle
• Both Forelimbs and hindlimbs with pes and manus

The total preserved body length is 722 mm (28.4 inches), with a trunk length of ~300 mm (11.8 inches). The high orbital-to-skull length ratio (43%) and open neurocentral sutures indicate that the individual was not fully mature. Based on comparisons with similarly proportioned taxa such as Jeholosaurus shangyuanensis and Changchunsaurus parvus, the estimated mass of this individual is 1.5–2.0 kilograms (3.3–4.4 lbs).

The animal had a lightly built skeleton, with long hind limbs, a slender tail, and gracile limbs.

Distinctive features include:

• Subtriangular orbit occupying nearly half the skull length
• Straight, elongate dorsal neural spines
• Shallowly concave preacetabular process of the ilium
• Tibia longer than femur, indicating a cursorial (running-adapted) posture
• Delicate digits with hoof-like unguals

If adult individuals reached greater size (as hypothesized), the species may have exceeded 1 meter (3.3 ft) in total length and approached 3.5–4.0 kg (7.7–8.8 lbs), although no mature specimens are currently known.

Size Estimation

The preserved total body length of the holotype is 722 mm (28.4 inches), measured from the tip of the snout to the posterior end of the last visible caudal vertebra. Based on comparison with Jeholosaurus shangyuanensis and Changchunsaurus parvus—both well-known Early Cretaceous neornithischians with similar body proportions—a juvenile Pulaosaurus of this size likely weighed between 1.5 and 2.0 kg (3.3–4.4 lbs).

This estimate is based on:

• The complete skeletal length of 72.2 cm
• Limb and torso proportions nearly identical to Jeholosaurus (which has a known adult length of ~1.27 m)
• A juvenile ontogenetic stage, inferred from open neurocentral sutures and high orbital ratio

Importantly, the specimen represents a juvenile individual, and thus these values do not reflect the maximum adult size. Extrapolating conservatively, a fully grown adult Pulaosaurus could have reached ~1.0–1.2 meters (3.3–3.9 feet) in total length and ~3.5–4.0 kg (7.7–8.8 lbs) in body mass, although no confirmed adult material has been discovered to validate this.

Until more specimens are recovered, the current size estimate should be regarded as representative of a juvenile, not the full species range.

Diet and Feeding Habits

Pulaosaurus qinglong was a herbivore, as inferred from its dentition and skull morphology. The dentary teeth have a prominent primary ridge and small marginal denticles, suitable for cropping and processing fibrous plant material. The narrow snout and large orbit suggest it relied on sight while foraging, and its small size implies feeding close to the ground.

The premaxilla likely bore beak-like structures or keratinous coverings, aiding in plant cropping. Its dentition shows some heterodonty, with premaxillary and posterior maxillary teeth differing slightly in morphology.

Habitat and Distribution

Pulaosaurus lived in the Early Cretaceous Yixian Formation, dated to the Aptian stage (~125–120 million years ago). This region was part of the Jehol Biota, a highly diverse ecosystem of northeastern China dominated by volcanic landscapes, lakes, and temperate forests.

Contemporary fauna included:

• Small theropods (Sinornithosaurus, Mei)
• Basal ceratopsians (Liaoceratops)
• Early birds (Confuciusornis)
• Mammaliaforms (Repenomamus)
• Pterosaurs, amphibians, and insects

The fossil was found in lacustrine sediments with abundant tuffaceous ash, suggesting a semi-aquatic or forest-edge habitat near shallow freshwater lakes or floodplains.

Behavior and Social Structure

As a small-bodied neornithischian, Pulaosaurus was likely fast and agile, avoiding predators through speed rather than defense. Its long legs and low body mass support the interpretation of a cursorial animal. The large orbits suggest acute vision, which may have aided in foraging or predator detection.

Due to its juvenile status, it is unknown whether Pulaosaurus was solitary or social. However, small herbivorous dinosaurs in similar ecological niches often show signs of group living or gregariousness, especially in juvenile cohorts.

Discovery and Research

The holotype was recovered from the Dawangzhangzi locality of Qinglong County, Hebei Province, within the Yixian Formation. It was collected by a team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and described by Yu et al. in 2024.

Phylogenetic analysis places Pulaosaurus within Neornithischia, but outside Cerapoda (i.e., not within Marginocephalia or Ornithopoda proper). It is more derived than Changchunsaurus but less so than Jeholosaurus, with unique pelvic and cranial traits. The authors also discuss the possibility of peramorphic traits evolving independently in different East Asian neornithischians during the Early Cretaceous.

Significance and Notable Facts

• One of the most complete small-bodied neornithischians from the Jehol Biota
• Represents a juvenile individual, rare in the fossil record with this degree of articulation
• Provides new information on pelvic, vertebral, and cranial variation among basal ornithischians
• Named after a mythological creature known for sound, metaphorically “giving voice” to a previously unknown lineage
• Expands the diversity and evolutionary complexity of Early Cretaceous neornithischians in Asia

Conclusion

Pulaosaurus qinglong is a valuable addition to the Early Cretaceous record of East Asia, representing a gracile, fast-moving, herbivorous dinosaur from the rich paleoecosystem of the Yixian Formation. Though currently only known from a juvenile individual, its morphology, completeness, and phylogenetic position offer important insights into the evolution of small-bodied ornithischians and the structure of Jehol terrestrial communities. Future discoveries may uncover adult specimens and clarify the full range of variation within the species.