Labocania aguillonae

Labocania aguillonae is a newly described species of tyrannosaurid theropod from the Late Campanian (approximately 73.6–72.5 million years ago) of the Cerro del Pueblo Formation in Coahuila, Mexico. This discovery reveals important insights into the diversity of southern Laramidian tyrannosaurs, a clade that was distinct from their northern relatives. The genus Labocania was first established based on the species Labocania anomala, but L. aguillonae represents a newly recognized species that shares close affinities with other southern tyrannosaurs.

Physical Characteristics

The holotype specimen of Labocania aguillonae (CPC 2974) is highly fragmentary but includes key elements of the skull, vertebrae, and limb bones. Based on the holotype it was a medium-sized tyrannosaur, with an estimated body length of 6.3 meters (20.7 f) based on comparisons with closely related species, but a partial dentary (CPC 3077) comes from a much larger animal than the holotype, so  Labocania aguillonae probably could reach up to 9.5 m (31.2 ft). The skull of the holotype is approximately 77.5 centimeters (30.5 inches) in length, suggesting a relatively smaller tyrannosaur compared to the likes of Tyrannosaurus rex. Nevertheless, in the case of the CPC 3077 individual, the skull was certainly larger.

The frontal bones are short and broad, typical of tyrannosaurids, and exhibit distinct features such as a strongly convex anterior margin and a triangular postorbital process. These features are autapomorphies (unique traits) of L. aguillonae.

The lacrimal bone, which forms part of the eye socket, has a strongly convex anteroventral margin, and the orbit (eye socket) is circular, a characteristic shared with Bistahieversor and Labocania anomala. The teeth of L. aguillonae exhibit a unique figure-eight cross-section at the base, with deep grooves extending up the labial and lingual surfaces, another autapomorphic feature.

Diet and Feeding Habits

Like other tyrannosaurids, Labocania aguillonae was a carnivorous predator. Its robust skull, powerful jaws, and large teeth suggest it was capable of hunting medium to large herbivorous dinosaurs that inhabited the same region. The grooves and figure-eight shape of its teeth may have helped with gripping and tearing flesh, enabling L. aguillonae to process larger prey effectively.

Habitat and Distribution

Labocania aguillonae lived in the coastal plains of what is now northeastern Mexico during the Late Campanian. The Cerro del Pueblo Formation, where its fossils were discovered, represents a low-lying deltaic environment that periodically experienced marine incursions, creating a landscape of coastal marshes, estuaries, and floodplains. This region supported a diverse ecosystem, with both terrestrial and aquatic species, including various herbivorous dinosaurs, fish, and invertebrates.

Behavior and Social Structure

As with other tyrannosaurs, Labocania aguillonae likely exhibited solitary or loosely social hunting behavior. Its powerful build and robust forelimbs suggest it was an apex predator, though it may have faced competition from other theropods in the area. The fossil evidence for social behavior in L. aguillonae is lacking, but its size and role as a top predator likely reduced the need for cooperative hunting strategies.

Discovery and Research

The holotype specimen (CPC 2974) was discovered in the Cerro del Pueblo Formation in Coahuila, Mexico, and described by Rivera-Sylva and Longrich in 2024. The fossil remains consist of a partial skeleton, including parts of the skull, vertebral column, limbs, and teeth. The discovery of L. aguillonae highlights the growing recognition of southern Laramidia as a hotspot for tyrannosaur diversity, revealing a distinct tribe of southern tyrannosaurs, known as Teratophoneini, which includes Labocania anomala, Bistahieversor, and Teratophoneus.

Significance and Interesting Facts

The discovery of Labocania aguillonae is significant because it adds to the understanding of tyrannosaur endemism in Laramidia. While northern Laramidia was dominated by albertosaurines and daspletosaurins, southern Laramidia was home to a unique clade of tyrannosaurs, including Labocania. This regional diversity challenges the notion that apex predators like tyrannosaurs had large geographic ranges and suggests that there was far greater diversity among these predators than previously recognized.