An article published in the journal “Nature Ecology & Evolution” reports the identification of a new species of tyrannosauroid that lived about 92 million years ago, in the Mid-Cretaceous period. A team of researchers led by Sterling Nesbitt of Virginia Tech named this species Suskityrannus hazelae completing a work begun in 1997, when the first fossils were discovered but weren’t identified at the time. It was a carnivore but with its height of less than one meter it was much smaller than its far more famous distant cousin, the T.rex.
Tyrannosauroids (Tyrannosauroidea) are a family of carnivorous dinosaurs that emerged in the Jurassic period with species that diversified until the end of the Cretaceous period, when the great mass extinction that wiped out all non-avian dinosaurs occured. There are discussions about how many species had plumage and include the most famous one, Tyrannosaurus rex.
In 1997 paleontologist Robert Denton discovered fossil dinosaur bones in the area of the Zumi River basin in New Mexico, but at the time he couldn’t identify the species. The following year, during a digging led by paleontologist Douglas Wolfe, the then 16-year-old Sterling Nesbitt discovered more fossil bones belonging to another more complete specimen but still insufficient for its identification. Nesbitt became a paleontologist as well and in 2006 began new studies on the bones discovered in the previous decade but only now has an answer arrived with the conclusion that they belong to a previously unknown species that was named Suskityrannus hazelae.
The two known specimens of Suskityrannus hazelae had a height of less than one meter (3′) and a length of almost 3 meters (9′) with an estimated weight of 20 to 40 kg (45 to 90 lbs). Bone analysis indicates that one of the specimens was at least 3 years old when it died. This dinosaur was much smaller than the T.rex and had more slender skull and feet than its more famous cousin. The two specimens’ arms weren’t found so there are no certainties about their characteristics but parts of their hand claws were found and they suggest that this animal had small arms as well. Its small size indicates that it hunted small animals even if it’s not clear which ones.
Suskityrannus hazelae is interesting among other things because it offers clues about the evolution of tyrannosaurs in the period immediately preceding the one in which the largest species such as T.rex emerged. It could be a key species to understand the evolution from the small Jurassic species to the larger ones that emerged during the Cretaceous.
The identification of Suskityrannus hazelae came more than twenty years after the discovery of the fossils taking advantage of a lot of knowledge on tyrannosauroids accumulated during this time. Curiously, it arrived a few weeks after the announcement of the identification of another tyrannosauroid, Moros intrepidus. It also represents an important moment in Sterling Nesbitt’s personal history as he was motivated by that discovery: over the years he conducted other research such as the one on Teleocrater Rhadinus but kept on being interested in the bones discovered when he was a teenager and finally identified them.