Labocania

Labocania
Clade	Dinosauria
Order	Saurischia
Suborder	Theropoda
Family	Tyrannosauridae
Subfamily	Tyrannosaurinae
Tribe	Teratophoneini
Type Species	Labocania anomala

Labocania is a genus of tyrannosaurid theropod dinosaur from Baja California, Mexico, which lived 73 million years ago, in the Campanian stage of the late Cretaceous Period. The type species is L. anomala.

Discovery and Naming

In the summer of 1970, the National Geographic Society & the Los Angeles County Museum of Natural History organised a joint paleontological expedition, led by geologist William J. Morris, to the Arroyo del Rosario in Baja California. While prospecting, volunteer Harley James Garbani discovered the skeleton of a theropod north of Punta Baja near Cerro Rayado. Garbani excavated the site in 1970 and 1971. The type species, Labocania anomala, was described and named by Ralph Molnar in 1974. The generic name references the La Bocana Roja Formation, named after la Bocana Roja, "the red estuary". The specific name means "anomalous" in Latin, in reference to the distinctive build.

The holotype, LACM 20877, was found in a layer of the La Bocana Roja Formation, dating from the late Campanian, about 73 million years old. It consists of a very fragmentary skeleton with skull elements, including a right quadrate, a left frontal, a piece of the left maxilla, a fragment of the dentarium, a chevron, the upper parts of both ischia, the middle shaft of the right pubis, most of the second right metatarsal, a pedal phalanx and several loose teeth. The elements were not articulated, dispersed over a surface of about two square metres, and strongly weathered. The remains were mixed with the ribs of Hadrosauroidea.

Description

Though its exact size is hard to establish, Labocania was probably a medium-sized carnivore, about 6 meters (20 ft) long. Gregory S. Paul estimated its length at seven metres, its weight at 1.5 tonnes in 2010. The cranial elements are very robust, and the frontals in particular are strongly thickened. The teeth of the maxilla are gradually recurving and rather flat; those of the premaxilla do not have a D-shaped cross-section.

Classification

Because Labocania is based on fragmentary material, its affinities were uncertain. Molnar noted certain similarities between Labocania and tyrannosaurids, especially in the form of the ischium which features a low triangular obturator process and a circular lateral scar on the upper end, but he did not assign Labocania to any family, placing it as "Theropoda incertae sedis". Molnar especially compared Labocania with Indosaurus and "Chilantaisaurus" maortuensis, later made the separate genus Shaochilong. Labocania was considered as a possible tyrannosauroid in the 2004 review of the group by Thomas R. Holtz, Jr., who, however, pointed out that the similarities with the Tyrannosauridae were shared with the Coelurosauria in general — no tyrannosauroid synapomorphies were present — and that Labocania also showed some abelisaurid traits such as the thick frontals and a reclining quadrate. On the other hand, the L-shaped chevron and the flattened outer side of the second metatarsal indicated a position in the Tetanurae.

A 2024 study has named a second species of Labocania, which is much less fragmentary and gives a much better placement of the genus. The new species, L. aguillonae, was described with a partial femur, metatarsal, and other fragments across the body. The morphology of the specimen solidifies the genus's classification as a tyrannosaurine tyrannosaurid in the tribe Teratophoneini. The current closest genera to Labocania is Teratophoneus, Dynamoterror, and Lythronax. Interestingly, the phylogeny places Nanotyrannus as a non-tyrannosaurine tyrannosaurid, despite it commonly being accepted as a junior synonym of Tyrannosaurus. Alioramini, a tribe usually put within Tyrannosaurinae, was placed outside of Tyrannosauridae as a sister taxon. Results of the phylogenetic analysis are shown below:

	Alioramini Tyrannosauridae Nanotyrannus Albertosaurinae Tyrannosaurinae Asiatyrannus Daspletosaurini Lythronax Nanuqsaurus Tyrannosaurini Tyrannosaurus Tarbosaurus Zhuchengtyrannus Teratophoneini Dynamoterror Teratophoneus Aguja Formation tyrannosaurine Bistahieversor Two Medicine Formation tyrannosaurine Labocania anomala Labocania aguillonae

Paleocology

L. anomala

Alexornis, a species of bird that coexisted with L. anomala. Art by Luxquine.

The type species Labocania anomala was found in the La Bocana Roja Formation, which dates back to the Late Cretaceous, although the exact date is unclear(Possibly as old as the Cenomanian). The enantiornithine Alexornis and indeterminate hadrosaurids(including an indeterminate lambeosaurine) would have lived with L. anomala.

L. aguillonae

A Labocania aguillonae roars at a chasmosaurine while a group of Tlatolophus flee in the background. Illustrated by Andrey Atuchin.

The bones of L. aguillonae were discovered in the Campanian rocks of the Cerro del Pueblo Formaton, whose strata date from 72.7 to 73.6 million years ago. Indeterminate ankylosaurian, ankylosaurid, and nodosaurid remains suggest members of those clades coexisted with L. aguillonae, as well as some indeterminate ceratopsids. Coahuilaceratops fossils were thought to be from the Cerro del Pueblo Formation, until a 2024 stratigraphic reassessment proved them to be from the Cerro Huerta Formation, although there are still indeterminate chasmosaurine fossils from the Cerro del Peublo Formation.

Hadrosaurs such as the parasaurolophin Tlatolophus and the kritosaurin Coahuilasaurus also coexisted with L. aguillonae. The tyrannosaurine also lived alongside an indeterminate thescelosaurid. Indeterminate dromaeosaurid, troodontid, tyrannosaurid, ornithomimid, and caenagnathid genera also likely lived in the Cerro del Pueblo Formation around the time of L. aguillonae. L. aguillonae also lived with a large deinocheirid ornithomimosaur, Paraxenisaurus.

Gallery

Labocania by cisiopurple