Science - crocodiles

Mar

2013

2:24pm, EDT

Massive extinction fueled the rise of crocodiles

Michael Alfaro

Scientists want to know how the lineage of modern crocodiles and alligators survived the massive extinction between the Triassic and Jurassic eras.

By Tia Ghose
LiveScience

A massive extinction between the Triassic and Jurassic eras paved the way for the rise of the crocodiles, new research suggests.

The researchers, who detailed their work Tuesday in the journal Biology Letters, found that although nearly all the crocodilelike archosaurs, known as pseudosuchia, died off about 201 million years ago, the one lineage that survived soon diversified to occupy land and sea. The lineage included the ancestors of all modern crocodiles and alligators.

"Even though almost all the lineages except for one was extinct, the remaining survivors still did well in terms of morphology and body plans and the whole morphological diversity," said study co-author Olja Toljagic, an evolutionary biology researcher who was at the Ludwig Maximilian University of Munich at the time of the study.

Understanding the traits that allowed certain lineages to thrive could one day help paleontologists untangle one of the greatest mysteries: how dinosaurs survived the extinction unscathed and took over Earth. [Mysterious Earth: 50 Amazing Facts]

Dinosaur counterparts
During the Triassic period, two lines of archosaurs lived in the same environment, which included dinosaurs, and the pseudosuchians, a large group of crocodilelike creatures that had short necks, long snouts and massive skulls.

But around 201 million years ago, volcanic activity or a meteor killed off half the known species on Earth. Just one lineage of pseudosuchians, called the crocodylomorphs, survived. That branch would ultimately give rise to modern-day crocodiles and alligators.

Crocodile line
In order to find out what happened to the pseudosuchians during the mass extinction, Toljagic and her colleague Richard Butler analyzed previous research data on pseudosuchians' skull characteristics, which could provide details about species diversity.

After doing a systematic analysis, the team found that the single surviving branch not only survived the extinction, but showed great diversity within a few million years after the extinction. These diversified crocodilelike creatures fanned out into different environments -- such as swamps, rivers and oceans -- during the Triassic period.

Ecological opportunity
The findings suggest that the extinction allowed crocodiles to flourish, said Stephen Brusatte, a paleontologist at the University of Edinburgh, who was not involved in the study.

"That extinction seems to have had a major effect by knocking off many species and then giving new species a chance," Brusatte told LiveScience.

The next step is to try to piece together a similarly detailed picture for dinosaurs around the same time in order to understand how dinosaurs survived the extinction, he said.

Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience @livescience, Facebook and Google+. Original article on LiveScience.com.

Feb

2013

1:01pm, EST

Rare baby crocs released into wild

Alex McWilliam/WCS

Members of the Village Crocodile Conservation Group prepare to release three of the nineteen Siamese crocodiles.

By LiveScience staff

Nineteen baby Siamese crocodiles are being let loose in the wetlands of Laos, the Wildlife Conservation Society (WCS) announced this week. The effort gives a boost to the critically endangered species, which is thought to include just 250 individuals in the wild.

The rare reptiles' eggs had been incubated at the Laos Zoo after being recovered during wildlife surveys in the wetlands of Savannakhet Province, and they hatched in the summer of 2011.

The baby crocs are being let go near the same spot where they were found, but they will stay in a "soft release" pen for several months. There they will get used to their surroundings and receive supplementary food and protection from community members, according to the WCS. Rising water levels at the start of the rainy season will eventually let the crocodiles swim away on their own, but they will be monitored occasionally by conservationists.

Siamese crocodiles grow up to 10 feet (3 meters) in length, but right now, these toothy creatures of the Laos Zoo measure only about 27 inches (70 cm). The crocs have never been known to attack humans, according to the conservation agency Fauna & Flora International. Classified as critically endangered by the International Union for Conservation of Nature, the Siamese crocodile population has been cut down by overhunting and habitat loss across much of its former range through Southeast Asia and parts of Indonesia.

The release effort was organized by the WCS's Laos branch as part of a community-based program to recover the local Siamese crocodile population and restore the associated wetlands, with a focus on incentives that improve local livelihoods.

"We are extremely pleased with the success of this collaborative program and believe it is an important step in contributing to the conservation of the species by involving local communities in long-term wetland management," Alex McWilliam, a WCS conservation biologist, said in a statement. "The head starting component of this integrated WCS program represents a significant contribution to the conservation of this magnificent animal in the wild."

Follow LiveScience on Twitter@livescience. We're also onFacebook &Google+.