Jul 4, 2017

An Enormous Crocodile with T. rex Teeth Was a Top Jurassic Predator

An artistic depiction of Razanandrongobe sakalavae scavenging on a sauropod carcass during the Middle Jurassic epoch in Madagascar. Unlike extant crocodilians, this terrestrial predator had a deep skull and walked on erect limbs.
The Jurassic period is often called the Age of the Ruling Reptiles, and for good reason. In the seas, aquatic reptiles such as the dolphin-like Stenopterygius were plentiful. In the air, flying reptiles known as pterosaurs searched for prey. On land, huge dinosaurs like Stegosaurus and meat-hungry Ceratosaurus had a commanding presence.

An important new addition to the list of ruling reptiles is Razanandrongobe sakalavae, or Razana for short. This gigantic crocodile, described in the journal PeerJ, was at the top of the Middle Jurassic food chain 164­–167 million years ago, and provides evidence that some crocodiles could take on even the fiercest dinosaur predators.

First known from a few teeth found a decade ago, Razana is now better understood due to recent analysis of additional cranial remains.

“We began with a couple of isolated teeth and ended up bringing back to life a one-ton terrifying bone crusher,” lead author Cristiano Dal Sasso of the Natural History Museum of Milan said.

He and colleagues Giovanni Pasini, Guillaume Fleury, and Simone Maganuco pieced together Razana based on fossils that include deep, massive jaw bones topped with large serrated teeth. The teeth were similar in size and shape to those of Tyrannosaurus rex, which is estimated to have exerted one of the largest bite forces among all terrestrial animals. At some 40 feet in length, T. rex was also an extremely large carnivore in its Late Cretaceous environment.

Paleontologists Cristiano Dal Sasso (left) and Simone Maganuco (right) standing next to the jaws of “Razana” at the Natural History Museum of Milan.
Razana, which lived close to 100 million years before T. rex, was 23 feet long. But it weighed an estimated 2,205 pounds and had erect legs, as opposed to the very low-to-the-ground limbs of modern alligators, crocodiles, and their relatives.

Its teeth and other remains suggest that Razana fed on hard tissues, such as bones and tendons. As a result, the researchers believe it could successfully bite into almost any animal — alive or dead.

“Razana was probably an opportunistic animal, just like hyenas and lions,” Dal Sasso said, adding that it was “not a very fast runner, but it was an ambush predator and a scavenger” that “could probably swim, just for crossing the nearby rivers, but it was built to walk on dry land.”

Its turf was a site now called the Mahajanga Basin of northwest Madagascar. Locals call the area the Sakalava region, so Razana’s full name means “giant lizard ancestor from the Sakalava region.”

Comparison between the estimated body size of the giant notosuchian crocodyliform Razanandrongobe sakalavae (nicknamed “Razana”) and a human.
The authors mention that this area is known for its “peculiar” collection of fossils representing everything from large marine reptiles called plesiosaurs to towering plant-eating dinosaurs known as sauropods.

“Madagascar was already separating from Africa, but was still connected to India, Australia and Antarctica,” Maganuco said.

Now an island nation, Madagascar remains known for its unique plant and animal life, often found nowhere else on Earth. Rare lemurs, for example, are native to Madagascar, which is also home to exotic orchids. Even crocodiles still thrive in Madagascar, with one infamous population of Nile crocodiles dwelling in caves.

Razana is long gone, but it holds a noteworthy place on the crocodile family tree. The scientists believe Razana was the largest and oldest “notosuchian,” predating other known forms of these animals by 42 million years. The term refers to certain early crocodilians and their extinct relatives. Previously, notosuchians were thought to appear in the Cretaceous, but Razana extends their dominance to the Jurassic.

While today’s crocodilians somewhat resemble Razana, much has changed due to evolution over millions of years.

“Modern crocs are well adapted to a semiaquatic lifestyle,” Maganuco said. “Their flattened skull with raised eyes is made for hunting in water.”

Paleo-artistic restoration of the head of Razanandrongobe sakalavae.
He continued that these animals today are incredible survivors, from an evolutionary standpoint. Their forerunners, such as Razana, were likely in direct competition with some of the most legendary predatory dinosaurs of all time. Some of these sturdy reptiles even managed to survive the end-Cretaceous extinction event that wiped out all dinosaurs, except for certain birds.

“The last fully terrestrial crocs lived up to the Middle Miocene about 15 million years ago, ruling the earth together with Cenozoic mammals and terror birds,” Maganuco said.

Terror birds, which could grow up to 12 feet tall, were flightless birds with ultra-sharp hooked beaks. Like Razana, they rose to the top of their food chain.

Read more at Discovery News

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