Stories tagged theropods

Apr
16
2011

For some reason paleontology news this week seems to cover the whole sensory gamut. First off, there’s a new discovery in China of a Mesozoic mammal named Liaoconodon hui that adds more transitional evidence regarding the evolution of the reptilian lower jaw into the middle ear bones found in mammals. The research was done by paleontologists from the American Museum of Natural History and the Chinese Academy of Sciences.

The guys over at Witmer Lab write about being involved in a study of the evolution of olfaction from small theropod dinosaurs to modern birds. The olfactory bulb is the part of the brain that detects odor, and it seems some modern birds inherited a pretty good sense of smell from their dinosaurian ancestors. Here's some video about it from the Witmer Lab site.

In the seeing department Jennifer Viegas over at Discovery News has a slide show presentation (with text) about a new study appearing in Science that suggests some dinosaurs and other prehistoric reptiles were nocturnal. The study is based on the sceleral ring and larger eye sockets found in the fossil remains of some prehistoric animals. Larry Witmer also mentions the subject on his blog (it’s located below the olfaction post).

Touch and taste – the last two senses - are covered in a new study of lice evolution at the University of Illinois-Urbana, and with the discovery of a new, toothy dinosaur in New Mexico.

Kevin Johnson, an ornithologist at the UI-Urbana, proposes that since lice seem to specialize in the way they annoy their host animals, it’s likely that lice that cause today’s birds to nit-pick, scratch and preen, are descended from lice that pestered feathered dinosaurs. You can read about Johnson’s research here.

Ghost Ranch, New Mexico: The red beds here have produced fossils of a new early carnivorous dinosaur.
Ghost Ranch, New Mexico: The red beds here have produced fossils of a new early carnivorous dinosaur.Courtesy Mark Ryan
Lastly, Daemonosaurus chauliodus ("evil spirit reptile with outstanding teeth") is a new carnivorous dinosaur species found recently at Ghost Ranch in New Mexico. The buck-toothed theropod more-than-likely feasted on all the other creatures it shared its environment with 200 million years ago during the Triassic (yes, I know I’m probably stretching the taste sensory categorization here but I needed something). The discovery of Daemonosaurus in a block of Coelophysis remains is important because it alters scientific thought on the early history of carnivorous dinosaurs. The study was led by vertebrate paleontologist Hans-Dieter Sues of the Smithsonian and appears in the journal Proceedings of the Royal Society B. You can also read about it at Dinosaur Tracking.

Dec
14
2009

Tawa hallae: Illustration of the newly discovered theropod dinosaur
Tawa hallae: Illustration of the newly discovered theropod dinosaurCourtesy Jorge Gonzalez
A new dinosaur found in New Mexico is changing how scientists view the early beginnings of the ruling reptiles. Tawa hallae was a small, carnivorous theropod measuring about 6-13 feet in length that hunted its prey during the late Triassic period not long after dinosaurs first appeared about 230 million years ago. Theropods are a group of mostly carnivorous dinosaurs that include the popular Tyrannosaurus rex. Until now, the record of Triassic theropods in North America has been somewhat lacking. But Tawa is helping change that.

Several high-quality specimens of T. hallae were uncovered, along with the remains of two other early meat-eaters in the spectacularly colorful strata around Ghost Ranch, an area near the town of Abiquiu in northern New Mexico. T, hallae's type specimen – that is the fossil that defines the species – was a nearly complete skeleton of a juvenile. The new study appeared in this month in the journal Science.

Digging out Tawa hallae at Ghost Ranch, NM: Sterling Nesbitt (left) and Michelle Stocker at work in the Hayden Quarry.
Digging out Tawa hallae at Ghost Ranch, NM: Sterling Nesbitt (left) and Michelle Stocker at work in the Hayden Quarry.Courtesy Randall Irmis, University of Utah
The bones Tawa hallae display similar features found in later dinosaurs (including birds) such as hip structure, hollow bones, and space for air sacs in some vertebrae. But it also contains characteristics found in other early carnivores, such as Herrerasaurus, another Triassic period biped. Herrerasaurus remains have been found in Triassic rocks in South America, alongside the earliest known remains of the two other dinosaur forms: sauropodomorphs (long-necked herbivores such as Diplodocus), and ornithiscians (beaked herbivores such as Stegosaurus). Considered by some paleontologists as one of the earliest dinosaurs. Herrerasaurus displays some theropod features but is missing traits found in others, leading some scientists to speculate whether it was a theropod at all, or even a dinosaur. But according to Sterling Nesbitt, a paleontologist and the study's lead author from the University of Texas in Austin, Tawa hallae has answered some of those questions.

"Tawa pulls Herrerasaurus into the theropod lineage, so that means all three lineages are present in South America pretty much as soon as dinosaurs evolved," said Nesbitt. "Without Tawa, you can guess at that, but Tawa helps shore up that argument."

The remains of two other distinct theropods were also found in the same quarry at Ghost Ranch. One displayed characteristics that made it closely related to Coelophysis (found elsewhere at Ghost Ranch), and the other to Herrerasaurus - indicating the lines diverged before the unified landmass Pangaea split apart into separate continents.

“When we analyzed the evolutionary relationships of these dinosaurs, we discovered that they were only distantly related, and that each species had close relatives in South America,” said Randall Irmis of the University of Utah. “This implies that each carnivorous dinosaur species descended from a separate lineage before arriving in [the part of Pangea that is now] North America, instead of all evolving from a local ancestor.” Irmis co-authored the study, and also works at the Utah Museum of Natural History.

Oddly, no sauropodomorph or ornithischian remains from the Triassic Period have ever been found in North America. Scientists admit that's somewhat perplexing but think it's possible they migrated through the area when it was still part of Pangaea. But thanks to Tawa hallae the evolution of the theropod line is becoming clearer.

"Tawa gives us an unprecedented window into early dinosaur evolution, solidifying the relationships of early dinosaurs, revealing how they spread across the globe, and providing new insights into the evolution of their characteristics," Nesbitt said.

Ghost Ranch, New Mexico: The spectacular rock formations at Ghost Ranch display strata from all three geological periods of the Mesozoic era and have proven rich in Triassic-aged fossils.
Ghost Ranch, New Mexico: The spectacular rock formations at Ghost Ranch display strata from all three geological periods of the Mesozoic era and have proven rich in Triassic-aged fossils.Courtesy Mark Ryan
The remains of Tawa hallae were found at Ghost Ranch in northern New Mexico about 65 miles north of Santa Fe, the same area where the spectacular Coelophysis remains were discovered in the late 1940s. Both species were found in the Chinle formation (pronounced chin lee), although Tawa’s fossils were found lower in the strata, in the older Petrified Forest member of the formation. The rich bone bed was first discovered in 2004 by amateurs on a week-long paleontology seminar sponsored by the Ruth Hall Museum at Ghost Ranch. Tawa hallae was named for the Hopi word for sun god, and in honor of Ruth Hall, the museum’s founder.

LINKS
National Science Foundation press release
Science Codex story
Science Frontline story

Dec
17
2007

The carcharodontosaurus: It died shortly after attempting to pronounce its own name.
The carcharodontosaurus: It died shortly after attempting to pronounce its own name.Courtesy ArthurWeasley
They (The Man) have just unveiled a newly discovered (or at least newly named) giant meat-eating dinosaur.

The Carcharodontosaurus iguidenis was a therapod, a two-legged meat-eater as big (or maybe bigger) than the t. rex. Its head wasn’t quite as robust as the tyrannosaurs’, though, and its teeth were more knife-like, instead of the thick spear point teeth of the t. rex.

The carcharodontosaurus was found in Niger, and it dates to the late Cretaceous. The Cretaceous is probably my favorite period in the Mesozoic anyway (mostly because it was the only one to have flowers), but North Africa in the Cretaceous is something particularly remarkable. It would have been warm and wet (like a mangrove swamp, maybe) and it was filthy with some of the coolest dinosaurs. There were three huge meat-eater species (two of which, the carcharodontosaurus and the spinosaurus were at least as large as the tyrannosaurus rex) living in the same area at the same time, alongside some of the biggest dinosaurs ever to live, the titanosaurs. Titanosaurs were a family of four-legged, long necked and long tailed dinosaurs, and some of them probably weighed in around 100 tons (maybe a little less, maybe a lot more, depending on who you believe).

It would be like, I don’t know, if Kodiak bears, Bengal tigers, African lions, and elephants all lived in the same neighborhood. But way, way bigger (if you think about it, one big titanosaur weighed as much as a small herd of elephants). Man, it would almost be worth getting stepped on and then eaten, just to see what it was like in person.