{"id":37948,"date":"2019-02-21T09:01:08","date_gmt":"2019-02-21T14:01:08","guid":{"rendered":"http:\/\/naturalsciences.org\/calendar\/?post_type=news&p=37948"},"modified":"2019-02-21T09:58:34","modified_gmt":"2019-02-21T14:58:34","slug":"new-species-of-tiny-tyrannosaur-foreshadows-rise-of-t-rex","status":"publish","type":"news","link":"https:\/\/naturalsciences.org\/calendar\/news\/new-species-of-tiny-tyrannosaur-foreshadows-rise-of-t-rex\/","title":{"rendered":"New Species of Tiny Tyrannosaur Foreshadows Rise of T. rex"},"content":{"rendered":"

\"Moros<\/a>Illustration: Jorge Gonzalez. Click for full-sized image.
\n<\/span><\/p>\n

EMBARGOED UNTIL FEB. 21, 2019 AT 9:00 A.M. EST<\/strong><\/p>\n

A newly discovered, diminutive \u2013 by T. rex<\/em> standards \u2013 relative of the tyrant king of dinosaurs reveals crucial new information about when and how T. rex<\/em> came to rule the North American roost.<\/p>\n

Meet Moros intrepidus<\/em>, a small tyrannosaur who lived about 96 million years ago in the lush, deltaic environment of what is now Utah during the Cretaceous Period. The tyrannosaur, whose name means \u201charbinger of doom,\u201d is the oldest Cretaceous tyrannosaur species yet discovered in North America, narrowing a 70-million-year gap in the fossil record of tyrant dinosaurs on the continent.<\/p>\n

\u201cWith a lethal combination of bone-crunching bite forces, stereoscopic vision, rapid growth rates, and colossal size, tyrant dinosaurs reigned uncontested for 15 million years leading up to the end-Cretaceous extinction \u2013 but it wasn\u2019t always that way,\u201d says Lindsay Zanno, paleontologist at North Carolina State University, head of paleontology at the North Carolina Museum of Sciences and lead author of a paper describing the research. \u201cEarly in their evolution, tyrannosaurs hunted in the shadows of archaic lineages such as allosaurs that were already established at the top of the food chain.\u201d<\/p>\n

Medium-sized, primitive tyrannosaurs have been found in North America dating from the Jurassic (around 150 million years ago). By the Cretaceous \u2013 around 81 million years ago \u2013 North American tyrannosaurs had become the enormous, iconic apex predators we know and love. The fossil record between these time periods has been a blank slate, preventing scientists from piecing together the story behind the ascent of tyrannosaurs in North America. \u201cWhen and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time,\u201d says Zanno. \u201cThe only way to attack this problem was to get out there and find more data on these rare animals.\u201d<\/p>\n

That\u2019s exactly what Zanno and her team did. A decade spent hunting for dinosaur remains within rocks deposited at the dawn of the Late Cretaceous finally yielded teeth and a hind limb from the new tyrannosaur. In fact, the lower leg bones of Moros<\/em> were discovered in the same area where Zanno had previously found Siats meekerorum<\/em>, a giant meat-eating carcharodontosaur that lived during the same period. Moros<\/em> is tiny by comparison \u2013 standing only three or four feet tall at the hip, about the size of a modern mule deer. Zanno estimates that the Moros<\/em> was over seven years old when it died, and that it was nearly full-grown.<\/p>\n

But don\u2019t let the size fool you. \u201cMoros<\/em> was lightweight and exceptionally fast,\u201d Zanno says. \u201cThese adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day.<\/p>\n

\u201cAlthough the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous,\u201d Zanno says. \u201cWe now know it took them less than 15 million years to rise to power.\u201d<\/p>\n

The bones of Moros<\/em> also revealed the origin of T.<\/em> rex<\/em>\u2019s lineage on the North American continent. When the scientists placed Moros<\/em> within the family tree of tyrannosaurs they discovered that its closest relatives were from Asia. \u201cT<\/em>. rex<\/em> and its famous contemporaries such as Triceratops<\/em> may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior,\u201d Zanno says. \u201cMoros<\/em> signals the establishment of the iconic Late Cretaceous ecosystems of North America.\u201d<\/p>\n

The research appears in Communications Biology<\/em>, and was supported in part by Canyonlands Natural History Association. Lecturer Terry Gates, postdoctoral research scholar Aurore Canoville and graduate student Haviv Avrahami from NC State, as well as the Field Museum\u2019s Peter Makovicky and Ryan Tucker from Stellenbosch University, contributed to the work.<\/p>\n

Note to editors<\/strong>: An abstract follows.<\/p>\n