|Diagram showing known remains|
Zanno et al., 2019
Zanno et al., 2019
Moros is a genus of tyrannosauroid theropod that lived during the Late Cretaceous period in what is now Utah, United States. It contains a single species, M. intrepidus. Moros represents the earliest known diagnostic tyrannosauroid material from the Cretaceous of North America by a margin of about 15 million years.
Discovery and naming
Moros was first discovered at the Stormy Theropod site located in Emery County in the U.S. state of Utah. Palaeontologists had been researching the area for ten years when in 2013 limb bones were seen jutting out of a hillside by Lindsay Zanno, prompting the excavation. The bones were described as a new species in February, 2019.
In 2019, the type species Moros intrepidus was named and described by Lindsay E. Zanno, Ryan T. Tucker, Aurore Canoville, Haviv M. Avrahami, Terry A. Gates and Peter J. Makovicky. The generic name is derived from the Greek Moros (an embodiment of impending doom), in reference to the establishment of the tyrannosauroid lineage in North America. The specific name is the Latin word intrepidus ("intrepid"), referring to the hypothesized dispersal of tyrannosauroids throughout North America following Moros.
The holotype, NCSM 33392, was found in the lower Mussentuchit Member of the Cedar Mountain Formation dating from the Cenomanian. The layer has a maximimum age of 96.4 million years. The holotype consists of a right hindlimb. It contains the thighbone, the shinbone, the second and fourth metatarsal and the third and fourth phalanx of the fourth toe. LAGs (Lines of arrested growth) indicate that it represents a subadult individual of six or seven years old, nearing its maximum size. Additionally, two premaxillary teeth were referred to the species, specimens NCSM 33393 and NCSM 33276.
Moros was a small-bodied, cursorial tyrannosauroid with an estimated weight of about 78 kg (172 lb). The foot bones of Moros were extremely slender, with metatarsal proportions found to be more similar to ornithomimids than to other Late Cretaceous tyrannosauroids.
In their phylogenetic analyses, Zanno and colleagues in 2019 recovered Moros as a basal pantyrannosaurian alongside Asian taxa from the middle of the Cretaceous such as Xiongguanlong and Timurlengia. This phylogenetic affinity with Asian basal tyrannosauroids suggests that Moros was part of a transcontinental exchange between the biotas of Asia and North America during the mid-Cretaceous that is well-documented in other taxa.
- Zanno, Lindsay E.; Tucker, Ryan T.; Canoville, Aurore; Avrahami, Haviv M.; Gates, Terry A.; Makovicky, Peter J. (February 2019). "Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record". Communications Biology. 2 (1): 64. doi:10.1038/s42003-019-0308-7. ISSN 2399-3642. PMC 6385174. PMID 30820466.
- Johnson, Anna (February 21, 2019). "New dinosaur T. rex relative Moros intrepidus discovered". News Observer. Retrieved February 22, 2019.
- Greshko, Michael (February 21, 2019). "New tiny tyrannosaur helps show how T. rex got big". National Geographic. Retrieved February 22, 2019.