Suskityrannus hazelae represents a significant find, offering new insight into the lineage of Tyrannosaurus rex. This dinosaur, named “coyote tyrant,” provides a window into a previously murky period of tyrannosaur evolution. Its discovery helps scientists piece together the evolutionary journey of these iconic predators, revealing how their characteristic features developed.
Discovery and Appearance
The discovery of Suskityrannus hazelae began with expeditions in the 1990s to the Zuni Basin in western New Mexico. Two partial skeletons were unearthed, with one specimen found in 1998 by then 16-year-old Sterling Nesbitt, a volunteer assisting paleontologist Doug Wolfe. The formal scientific description was published in 2019, nearly two decades after its initial discovery.
This ancient creature was relatively small compared to its famous descendant, measuring about 9 feet (2.7 meters) long and standing around 3 feet (0.9 meters) tall at the hip. Its estimated weight ranged from 45 to 90 pounds (20 to 41 kilograms), making it roughly the size of a modern horse. Suskityrannus hazelae possessed a more slender skull and foot compared to later, larger tyrannosaurs like Tyrannosaurus rex. It was a bipedal theropod, and its teeth suggest a carnivorous diet.
Evolutionary Significance
Suskityrannus hazelae fills a gap in the fossil record of tyrannosauroid evolution. Prior to its discovery, fossil evidence for tyrannosaurs was scarce in the mid-Cretaceous, making it difficult to trace their development from smaller, earlier forms to the massive predators of the Late Cretaceous. This species lived approximately 92 million years ago during the Turonian age of the Late Cretaceous.
This dinosaur serves as a transitional form, linking smaller tyrannosauroids found in North America and China with the much larger tyrannosaurids that dominated ecosystems until the extinction event that ended the age of non-avian dinosaurs. Its physical characteristics, such as its relatively slender build and skull, offer clues about how features like powerful bites and reduced forelimbs evolved over time. The study of Suskityrannus hazelae indicates that tyrannosaurs grew larger after other large predators disappeared, rather than overthrowing them.
Habitat and Lifestyle
Suskityrannus hazelae inhabited the ancient landscapes of southern Laramidia, now western North America. The fossils were recovered from the Moreno Hill Formation in the Zuni Basin of New Mexico, a region that experienced tectonic shifts and volcanic activity. The paleoclimate was humid, suggesting an environment with lush vegetation, possibly including swampy or forested areas.
As a predatory theropod, Suskityrannus hazelae likely hunted smaller animals within its ecosystem. Its teeth suggest a carnivorous diet, similar to its larger tyrannosaur relatives. Other dinosaurs known from the Moreno Hill Formation include the ceratopsian Zuniceratops and the theropod Nothronychus, along with various turtles and crocodyliforms, providing a glimpse into the diverse community Suskityrannus hazelae shared its habitat with.