Aged roughly 79.5 million years, Thanatotheristes degrootorum sits near the base of the tyrannosaurs’ ascent to ecological domination. The...
“I tried to be really meticulous with identifying features that made it unique,” says Voris, who is now a Ph.D. student at the University of Calgary. “It’s interesting to have the opportunity to name a new species—and I’m hoping it isn’t all downhill from here.”
When tyrannosaurs first arose some 165 million years ago, they weren’t the tyrants that eventually reigned over the Cretaceous period in Asia and North America. Some were downright tiny—no bigger than five feet tall—and hunted in the shadows of the age’s more massive carnivores, including the bus-size allosauroids and the large-clawed megalosauroids.
About 80 million years ago, these other predators faded away, giving tyrannosaurs a chance to rise to the top of the food chain and grow into giants. By 66 million years ago right before its extinction, the infamous T. rex grew up to 40 feet long and weighed more than nine tons. But Thanatotheristes, unveiled in Cretaceous Research on January 23, doesn’t seem to have been as large or as hulking as T. rex, underscoring the diversity at the top of this period’s food chain. (Learn more about the world’s biggest T. rex yet found.)
“It seems like tyrannosaurs had a dynamic evolutionary history,” University of Edinburgh paleontologist Steve Brusatte, who wasn’t involved with the study, says in an email. “They weren't all monstrous superpredators like T. rex, but there were many little subgroups that had their own domains and their own distinctive body types.”
Hunting the reaper
Tyrannosaurs were probably rare in life and even rarer as fossils. Regardless, filling in the group’s evolutionary picture from bony remains is a challenging task. Their plant-eating peers evolved a striking variety of large neck frills and head crests that helped the animals spot their species, rivals, and potential mates. But tyrannosaurs lacked these billboards.
It’s hard to tell when new species arrive in the fossil record, says College of Charleston paleontologist Scott Persons, who was not part of the study team. “You get into this real nitty-gritty. You have to really fine-tune your taxonomic observations.”
23 STUNNING PICTURES OF DINOSAURS
Picture of a preserved Tyrannosaurus rex skull on display at Berlin's Natural History Museum.
Picture of a Psittacosaurus fossil with long bristle-like structures on the proximal part of tail.
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This nearly whole, deep-black skull belongs to the most complete specimen of Tyrannosaurus rex on display in Europe, an individual nicknamed Tristan Otto. With 170 of its 300-odd bones… Read More
PHOTOGRAPHY BY GERD LUDWIG
A closeup shows the spine and tail bristles on an incredibly well-preserved fossil of the herbivorous dinosaur Psittacosaurus mongoliensis, on display at the Senckenberg Museum in… Read More
PHOTOGRAPHY BY ROBERT CLARK
Sinosauropteryx prima, from China’s northeastern province of Liaoning, was found in 1996 and is recognized as the first known feathered dinosaur. The discovery of downy plumage – seen here as dark fuzz surrounding the fossil – shook the foundations of paleontology; many dinosaur experts were already convinced that birds descended from dinosaurs, but here was the feathery proof turned to stone. More than 50 other species of dinosaur have been found with impressions or other evidence of feathers in the past few decades.
PHOTOGRAPHY BY O. LOUIS MAZZATENTA
The fossil deposits of Liaoning, China, not only preserve dinosaurs, but also early birds, such as these delicate and beautiful specimens of the 120- to 125-million-year-old species Confuciusornis sanctus. This bird – noted for its two long, ribbon-like tail feathers – is one of the most commonly discovered animals in the Yixian and Jiufotang formations of the early Cretaceous, with many hundreds of specimens now in Chinese museums. This means researchers can ask questions about variation within the population, an unusual opportunity in a fossil species.
PHOTOGRAPHY BY O. LOUIS MAZZATENTA
At about 200 million years old, the dainty carnivore Coelophysis bauri was one of the earliest dinosaurs to live in the U.S. Southwest. This late Triassic species, which is the state fossil of New Mexico, reached up to 9.8 feet in length but weighed just 33 to 44 pounds. This specimen has its head twisted back over its spine in what is known as the “death pose” – a common position for fossilized dinosaurs that is possibly caused by the contraction of muscles and ligament after death.
PHOTOGRAPHY BY NOREBERT WU/ MINDEN PICTURES
These eggs belonged to sauropods, giant long-necked dinosaurs that grew to be the largest land animals that ever lived. While sauropod eggs have been found across the world, from Spain and France to Argentina and the United States, these particular specimens still embedded in rock hail from China. Dinosaur eggs are usually found in groups and would have been laid in depressions in the ground. They come in a variety of shapes and sizes, depending on the species, but sauropod eggs are typically round and about the size of a grapefruit.
PHOTOGRAPHY BY SCENICS & SCIENCE/ALAMY
A skull of the late Jurassic predatory dinosaur Allosaurus fragilis remains encased in rock in the Quarry Exhibit Hall of the Dinosaur National Monument in Jensen, Utah. The apex carnivore of its time, Allosaurus terrorized the western United States about 150 to 155 million years ago.
PHOTOGRAPHY BY BRECK P. KENT/ ANIMALS ANIMALS/ EARTH SCENES
Protoceratops andrewsi, an early relative of the horned dinosaur Triceratops, is seen on display at CosmoCaixa Barcelona as part of an exhibit of dinosaurs from Mongolia’s Gobi desert… Read More
PHOTOGRAPHY BY XAVIER FORES - JOANA RONCERO/ALAMY
Exhibition workers put the finishing touches on an anatomically precise, life-size reconstruction of a Spinosaurus aegypticus skeleton created from digital models of the fossil bones. The 50-foot-long model went on display at the National Geographic Museum in Washington, D.C., in September 2014 as the centerpiece of the “Spinosaurus: Lost Giant of the Cretaceous” exhibition.
PHOTOGRAPHY BY MIKE HETTWER
This closeup shows the formidable teeth and jaws of a female Tyrannosaurus rex known as ‘Trix,” which is on display at the Natural History Museum of Leiden in the Netherlands. Excavated in 2013 in Montana by museum scientists, the fossil skeleton is more than 80 percent complete, ranking it among the top T. rex specimens in the world.
PHOTOGRAPHY BY DEAN MOUHTAROPOULOS/GETTY
This picture shows armored plates on the spectacularly complete fossil of an ankylosaur named Borealopelta markmitchelli; the lighter bands represent more flexible tissue between… Read More
PHOTOGRAPHY BY ROBERT CLARK
This unusual skull comes from a relative of Triceratops named Kosmoceratops richardsoni. This rhino-size ceratopsian dinosaur lived on the late Cretaceous landmass of Laramidia, which is today the western part of North America. Kosmoceratops means “ornamented horned face,” and the species has 15 horns and frills on its skull, which were likely used to attract mates or battle rivals rather than defend against predators.
PHOTOGRAPHY BY CORY RICHARDS
Two sets of footprints at the Moenkopi Dinosaur Tracks in Arizona were likely left by a mother and a young Dilophosaurus wetherilli about 193 million years ago – an evocative record of dinosaur behavior from the early Jurassic period. These narrow, three-toed footprints are typical of carnivorous theropod dinosaurs.
PHOTOGRAPHY BY CARVER MOSTARDI/ ALAMY
As winds and rain pound surface layers of sediment, they slowly expose any dinosaur fossils encased within, which are made of more hardy material. Here, a two-foot-long section of the tail of a duck-billed hadrosaur emerges from sandstone. Some of the world’s best fossil-hunting locales are badlands, where surface sediments are rapidly eroded by weathering.
PHOTOGRAPHY BY CORY RICHARDS
This cast of Triceratops horridus resides at the Royal Tyrell Museum in Alberta, Canada. Triceratops was the first known horned dinosaur, or ceratopsian, described in 1889. More than 80 other species of ceratopsians have now been described, the vast majority from western North America, and new finds are revealed every year.
PHOTOGRAPHY BY ALL CANADA PHOTOS/ ALAMY
A close-up shows the tail region of the early Cretaceous Chinese dinosaur, Sinornithosaurus millenii. This feathered dromaeosaur relative of Velociraptor had ossified tendons in its tail anchored by its vertebrae or backbones. These narrow bony rods stiffened the tail, improving balance and aiding maneuverability for this fleet-footed, predatory species.
PHOTOGRAPHY BY O. LOUIS MAZZATENTA
A set of dinosaur tracks crosses the Valley of the Dinosaurs in Sousa, northeastern Brazil. While fossilized dinosaur bones tell us about the anatomy of these long-extinct animals, so-called ichnofossils such as footprints, teeth marks, nest scrapes, and coprolites (dung) give us important clues to the behavior and lives of ancient species.
PHOTOGRAPHY BY PULSAR IMAGES/ ALAMY
This skull of the dinosaur Velociraptor mongoliensis comes from the early Cretaceous formations in Mongolia’s Gobi desert. Made famous by the 1993 movie Jurassic Park, these dromaeosaurs were much smaller in real life than what’s been depicted in the film and its sequels, reaching just 1.6 feet high and likely weighing little more than about 33 pounds.
PHOTOGRAPHY BY PHIL DEGGINGER/ CARNEGIE MUSEUM/ ALAMY
The name of this species, Mei long, comes from the Chinese for “soundly sleeping dragon,” reflecting the fact that this remarkable fossil captures a rare and peaceful moment of dinosaur behavior. Seen here from underneath, this troodontid is tucked up in the roosting position familiar from modern birds, with its head nestled under its forearm. The folded-up feet and legs run right-left in this image, with the tail wrapped across the top.
PHOTOGRAPHY BY O. LOUIS MAZZATENTA
Stitched together from a number of images, this panorama shows the massive reconstruction of a titanosaur sauropod installed at the American Museum of Natural History in New York in… Read More
PHOTOGRAPHY BY XINHUA/ ALAMY
A detail shows the feet and claws of a near-complete specimen of Tyrannosaurus rex dubbed Tristan Otto, which is on display at the Museum für Naturkunde in Berlin, Germany. In life these claw bones would have been covered with keratin sheaths, akin to the claws of a cat, but much larger and capable of inflicting far more significant damage.
PHOTOGRAPHY BY MEHMET KAMAN/ANADOLU AGENCY/GETTY
This cast of the extravagantly crested duck-billed hadrosaur Parasaurolophus walkeri is on display at the Senckenberg Museum in Frankfurt, Germany. The nasal passages and forehead of this species extend to the rear of its head, forming a six-foot-long hollow, bony crest. This is thought to have been used as a resonance chamber, akin to a wind instrument such as a trombone or trumpet, likely allowing the species to produce loud calls that carried over great distances.
PHOTOGRAPHY BY HINRICH BAESEMANN/ DPA PICTURE ALLIANCE ARCHIVE/ ALAMY
This highly ornamented dinosaur, featured on the December 2007 cover of National Geographic magazine, was originally described as a new species called Dracorex hogwartsia, or… Read More
PHOTOGRAPHY BY IRA BLOCK
Every scrap of tyrannosaur bone holds vital clues—even those found by chance, such as the Thanatotheristes remains. John and Sandra De Groot stumbled on the bones in 2010, as their family walked along the shoreline of southern Alberta’s Bow River. The pair contacted the Royal Tyrrell Museum, which sent paleontologists to collect the fossils and search for more. To honor the family, Voris’ team gave Thanatotheristes the species name degrootorum.
“They’ve been an invaluable resource,” Voris says of the De Groots. “It just shows, you don’t have to be a paleontologist to help out in paleontology.”
Nearly a decade after the fossils were cleaned, catalogued, and stored, Voris and his colleagues began putting the paleo-puzzle together. The team focused on the jawbones, which had uniquely prominent ridges that hinted at long-lost facial structures. The animal’s cheekbone also had an oval shape in cross-section, unlike other closely related tyrannosaurids.
DINOSAURS 101
Over a thousand dinosaur species once roamed the Earth. Learn which ones were the largest and the smallest, what dinosaurs ate and how they behaved, as well as surprising facts about their extinction.
Yet in other ways, Thanatotheristes was similar to its relatives, which by all accounts weren’t friendly creatures. Tyrannosaurs’ snouts are often crisscrossed with the marks of long-ago scuffles with other dinosaurs—including other tyrannosaurs. Thanatotheristes is no exception. A whitish scar, stretching four inches long, snakes along its right upper jaw. “It’s a Scarface,” Persons says.
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https://www.nationalgeographic.com/science/2020/02/new-reaper-of-death-tyrannosaur-discovered-canada/
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