Fossil Shows Pre-Dino Reptile Giving Birth

A birth that took place long before the first dinosaurs emerged can be seen now, thanks to a newly unearthed fossil.

The fossil, discovered in China and described in PLOS ONE, freezes in time the moment that an Ichthyosaur gave birth 248 million years ago.

To give you an idea of how long ago that was, the first dinosaurs emerged some 18 million years after this birthing event.

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Ichthyosaurs evolved from terrestrial reptiles and moved to the water. This particular individual and her offspring belonged to the genus Chaohusaurus, the earliest known Mesozoic marine reptile.

"The study reports the oldest vertebrate fossil to capture the ‘moment' of live-birth, with a baby emerging from the pelvis of its mother," said author Ryosuke Motani, of the University of California at Davis, in a press release. "The 248-million-year old fossil of an ichthyosaur suggests that live-bearing evolved on land and not in the sea."

He and his colleagues suspect live birth began on land because the infants were coming out head first, a posture associated with land-dwelling animal births.

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In addition to showing the earliest live birth of an ancient marine reptile, the specimen is also thought to contain the oldest known fossil embryos of Mesozoic marine reptiles.

This mom and her babies are obviously long gone. At least one ichthyosaur species, however, survived until the Early Cretaceous, about 90 million years ago. While it's long gone too, it shows how successful these animals - as a group - were during their lengthy time on our planet.

Photo: Ryosuke Motani, doi:10.1371/journal.pone.0088640

As paleontologists increasingly unearth evidence of feathers in prehistoric fossils, our conceptions of what dinosaurs looked like when they roamed the earth has gradually evolved.

Instead of the reptilian appearance we all recognize from childhood toys and films like Jurassic Park, many dinosaurs in fact more closely resembled birds, kind of like this recently discovered little guy, Eosinopteryx brevipenna, a flightless theropod dinosaur that roamed China during the Middle/Late Jurassic period.

Archaeopteryx, also known as Urvogel, the German word for "original bird" or "first bird," was first discovered in 1860 and later fossils of this species presented some of the earliest evidence of flight in these prehistoric animals.

An intermediate creature that was not quite dinosaur but not exactly a bird either when it lived 150 million years ago, Archaeopteryx had teeth, a long tail, and wings capable of flight with claws at the end for grabbing prey.

A century after the discovery of Archaeopteryx, paleobiologists increasingly found anatomical connections between birds and dinosaurs. In the 1970s, artists began to portray dinosaurs with feathers based on accumulating evidence.

Megapnosaurus, shown here, was another species with whom researchers began early to identify with feathers. A lightweight animal that could reach up to 10 feet in length and roamed Jurassic Zimbabwe, Megapnosaurus, also known as Syntarsus, traveled in packs and preyed on small reptiles and fish.

Many of the fossils unearthed that provided evidence of feathers had deteriotated over the eons they remained buried. It wasn't until 2010 that researchers identified color pigments in feathers from dinosaurs and early birds.

Sinosauropteryx, illustrated here, was a theropod dinosaur that had "simple bristles -- precursors of feathers -- in alternate orange and white rings down its tail," according to a description of the study's findings.

Given that so many feathered dinosaurs were in fact flightless, the purpose of the feathers has been a subject of debate. Some dinosaurs may have evolved feathers for social signaling; others had plumage to provide insulation.

In the cases of some dinosaurs, such as the two oviraptors, herbivores related to T. rex that lived during the Cretaceous period, researchers believe the feathers were used for mating displays, similar to modern-day peacocks and turkeys.

You might be fooled into thinking the animals in this illustration are something between a murder of crows and a band of blue jays. In fact they are Microraptors that lives more than 130 million years ago.

These four-winged, plumed dinosaurs were no larger than modern-day pigeons and sported iridescent tail feathers.

Researchers believe the shimmering plumage was likely used in mating and other social interactions.

Like the diversity among birds today, not all feathered dinosaurs were lightweight, agile animals. A massive tyrannosaur that lived in China until about 65 million years ago, Yutyrannus huali, meaning "beautiful feathered tyrant," grew up to 30 feet long and could weigh more than 3,000 pounds.

This titanic tyrannosaur, as it was described, significantly increases the size range for feathered dinosaurs.

In a stunning find published in the journal Science in 2011, paleontologists uncovered dinosaur feather preserved in amber that dated back some 79 million years ago.

This discovery provided scientists a new window into the evolution of feathers in terms of structure in the evolutionary timeline from dinosaurs to birds. Even shades of color remained well preserved in the amber.