By Anastasia Christakou
The first four-legged fossil snake ever found is forcing scientists to rethink how snakes evolved from lizards.
Although it has four legs, Tetrapodophis amplectus has other features that clearly mark it as a snake, says Nick Longrich, a palaeontologist at the University of Bath, UK, and one of the authors of a paper describing the animal in Science1.
The creature’s limbs were probably not used for locomotion, the researchers say, but rather for grasping prey, or perhaps for holding on to mating partners. Such speculation inspired the snake’s name, which loosely translates as ‘four-legged hugging snake’.
Scientists have long argued over whether snakes evolved from land or marine animals. Tetrapodophis lacks adaptations for marine life, such as a tail useful for swimming. But its skull and body proportions are consistent with adaptations for burrowing. Longrich says that the finding unequivocally shows that snakes originated in the Southern Hemisphere and strongly supports a terrestrial origin.
The new species, a cousin of the Triceratops, was formally named for its regal appearance—the skull bears a bony frill decorated with a series of pentagon-shaped plates, like spikes on a crown. Compared to Triceratops, the dinosaur also possesses a taller nose horn and two “comically small” horns over its eyes. As such, the researchers have nicknamed the creature Hellboy. No matter what you call it, though, the 70-million-year-old fossil represents an unexpected case of evolutionary convergence among horned dinosaurs, and it hints at the potential for more fossil wonders waiting to be unearthed.
Since its discovery in 1860, Archaeopteryx was widely considered to be the earliest known bird. But in 2009 a team of scientists decided it was more dinosaurlike than avian. Because of its reptilian metabolism and growth rate (slower than that of a bird), the transitional species should be removed from the bird family tree, the scientists said.
Now the discovery of a pheasant-size fossil — one that researchers say dates back even earlier than the 150-million-year-old Archaeopteryx — has prompted a re-examination of the entire lineage. According to an international team of scientists led by the Royal Belgian Institute of Natural Sciences, Archaeopteryx should indeed be considered an early bird.
“We decided to start the analysis from zero,” said Pascal Godefroit, a paleontologist with the Royal Belgian Institute and lead author of the new report, which appears in Nature. “And we decided that the traditional view is the best one. Archaeopteryx is a primitive bird.”
The newly discovered fossil, which a farmer pulled from a shale bed in Liaoning Province in northeastern China, reveals a chickenlike creature that lived 160 million years ago, making it the oldest known creature within the avian lineage. Researchers have named it Aurornis, which means “dawn bird.”
A Canadian-led group of paleontologists is getting a detailed look at how baby dinosaurs developed inside their eggs, by examining an ancient fossil bed full of embryos.
During the Late Jurassic, about 190 million years ago, huge, long-necked plant-eating dinosaurs called Lufengosaurus gathered together at the site in China’s Yunnan province to lay clutches of softball-sized eggs, year after year.
An excavation of the site led by Robert Reisz at the University of Toronto Mississauga has yielded crushed eggshells —the oldest dinosaur eggshells ever found — and 200 tiny bones from at least 20 Lufengosaurus embryos, including some that amazingly still appeared to have some protein attached to them, the researchers reported in the journal Nature this week.
Reisz said it appears that Lufengosaurus chose a nesting site close to a river, probably because the sediments there were moist, and some years the nesting site flooded, smothering the embryos. At the time of the dinosaurs, the area had a tropical climate and was likely prone to monsoons during the wet season.
The flooding likely occurred at slightly different times each year over a number of years.
“The eggs were caught at different stages of development,” Reisz said in an interview. “That’s what makes this project really exciting.”