23August2017

Sharp-toothed fossil links old and new dinosaurs

New dinosaur species is a missing link. The surprising discovery of a fossil of a sharp–toothed beast that lurked in what is now the western U.S. more than 200 million years ago is filling a gap in dinosaur evolution.

Sharp-toothed fossil. It was T. rex ancestor. The dinosaur in question, Daemonosaurus chauliodus, dates back to the end of the Triassic Period, approximately 205 million years ago.

The short snout and slanting front teeth of the find — Daemonosaurus chauliodus — had never before been seen in a Triassic era dinosaur, said Hans–Dieter Sues of the Smithsonian’s National Museum of Natural History. Sues and colleagues report the discovery in Wednesday’s edition of the British journal Proceedings of the Royal Society B.

Daemonosaurus was discovered at Ghost Ranch, N.M., a well–known fossil site famous for the thousands of fossilized skeletons found there, notably the small dinosaur Coelophysis. Ghost Ranch was more recently the home of artist Georgia O’Keeffe, who was known to visit the archaeological digs under way there, Sues noted.

Sharp-toothed fossil: This artist rendering provided by Jeffrey Martz shows a Daemonosaurus chauliodus and its size relative to an modern American quarter. The species name chauliodus is derived from the Greek word for 'buck-toothed' and refers to the species’ big slanted front teeth. Jeffrey Martz/APDescription. The illustration seen left compares the head and neck with a quarter. It has a short snout and enormous front teeth.

Having found only the head (skull) and neck of sharp–toothed Daemonosaurus, the researchers aren’t sure of its exact size but they speculate it would have been near that of a tall dog. Its name is from the Greek words “daimon” meaning evil spirit and “sauros” meaning lizard or reptile. Chauliodus is derived from the Greek word for “buck–toothed” and refers to the species’ big slanted front teeth.

Thus, its name means “the evil spirit reptile with outstanding teeth” suggests the dinosaur lineage that included the mighty T. rex experimented with its skull shape more than thought, researchers said.

This dog-sized, ferocious-looking critter is called Daemonosaurus chauliodus, which means something along the lines of “buck-toothed evil lizard,” says Hans-Dieter Sues. The name alludes to legends of evil spirits at Ghost Ranch in New Mexico, where the remains of this species were discovered, and to the large, serrated front teeth found in its upper jaw.

“The huge front teeth of Daemonosaurus would have been useful for seizing and killing prey,” Sues told LiveScience. Moreover, its short, deep snout “suggests powerful biting.”

Based off the size of this skull and the bodily proportions of other early dinosaurs, “I would estimate an overall length of 5 feet, as most of these animals have really long tails, and Daemonosaurus would have stood as tall as a large dog,” Sues said.

The findings reveal that theropods experimented with a variety of skull shapes early in their evolution, attaining considerable diversity during the Late Triassic. This likely helped coexisting species fit into a variety of niches and compete for different prey.

“It looks to be a mean character,” commented paleontologist Paul Sereno of the University of Chicago, who was not part of the research team. “I can’t wait to see if they get any more of the skeleton.”

This fits in quite nicely between the dinosaur groups, Sereno said, even though its face is unlike anything that would have been expected in these early dinosaurs, which tended to have more elongated snouts.

Link. Sues, curator of vertebrate paleontology at the museum, said the discovery helps fill the evolutionary gap between the dinosaurs that lived in what is now Argentina and Brazil about 230 million years ago and the later theropods like the famous Tyrannosaurus rex.

The dinosaur in question, Daemonosaurus chauliodus, dates back to the end of the Triassic Period, approximately 205 million years ago. This makes it an early member of the theropods, or “beast-footed” dinosaurs, the lineage later comprising all the carnivores, including Tyrannosaurus rex.

However, based on the nearly complete skull and some vertebrae and ribs that were discovered in New Mexico, Daemonosaurus was more likely a dead end than a missing link to theropods that came after it. Its short, deep snout and unusual teeth make it quite different from contemporary long-snouted, smaller-toothed neotheropods, the ancestors of giants such as T. rex.

Features of the skull and neck of Daemonosaurus indicate it was intermediate between the earliest known predatory dinosaurs from South America and more advanced theropods,” said Sues. “One such feature is the presence of cavities on some of the neck vertebrae related to the structure of the respiratory system.”

This dinosaur provides a link between what paleontologists consider “early” and “later” dinosaurs. There’s a gap in the fossil record between the oldest known dinosaurs, which walked or ran on their hind legs about 230 million years ago in Argentina and Brazil, and other predatory dinosaurs that lived much later. Daemonosaurus chauliodus helps fill in a blank in dinosaur history.

This newly discovered species lived about 205 million years ago, and probably preyed on other dinosaurs and other small animals, Sues said. At that time, what is now the American Southwest was located close to the equator, so it was warm and monsoon-like with heavy seasonal precipitation. This dinosaur was probably active during the day, although its large eyes suggest it could have seen at night as well.

How did it go extinct? It may have fallen victim to an extinction event that occurred about 200 million years ago. As the continents were separating, there was a large zone of volcanic activity. Enormous quantities of lava was released, doing “horrible things to the atmosphere.” Most dinosaurs made it through (that is, until an asteroid struck around 65 million years ago), but perhaps not this one.

Dinosaur land. The environment in which Daemonosaurus lived was very warm, with seasonal rainfalls. Sues noted “there was a smorgasbord of other vertebrates” at the site on which this predator could have fed.

“At Ghost Ranch, most of the fossils belonged to the more advanced neotheropod Coelophysis [a small carnivorous dinosaur], but there were also fossil remains of numerous other reptiles, including at least two large non-dinosaurian predators, and a variety of fishes,” he explained. “The flora, which we know from other occurrences of comparable age, would have consisted of conifers, ferns, and horsetails.”

Daemonosauruswas discovered when a large block of mudstone containing numerous remains of Coelophysis was loaned by the Carnegie Museum of Natural History to the State Museum of Pennsylvania.

Model dinosaur. The formative steps of theropod evolution are still poorly understood. The oldest known theropods date back about 230 million years ago in Argentina and Brazil.

Daemonosaurusnow stands as an early example in the lineage, with a skeletal structure intermediate between the first known dinosaurs and later theropods.

“The next step will be further comparisons of Daemonosaurus with other Triassic dinosaurs, especially new fossils found during the last few years,” Sues said.

Still more to come?
This find shows there is still much to be learned about the early evolution of dinosaurs. “The continued exploration of even well–studied regions like the American Southwest will still yield remarkable new fossil finds,” Sues said.

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