An ancient marine reptile was discovered giving birth, immortalized in a remarkable fossil. Examination of the rare find is headed by Ryosuke Motani from the University of California, Davis.
The ancient Ichthyosaur lived 248 million years ago in what is now Anhui Province in China. This species is among the oldest-known marine reptiles which lived during the Mesozoic Era.
Seen in the structure of the fossil are the mother, a recently-born offspring, an unborn embryo, and the remains of another young Ichthyosaur. This may provide evidence that the practice of giving birth to live offspring was developed on the land, and not in the water.
Distant ancestors of marine reptiles lived on the land, before taking to the sea. Ichthyosaurs looked like a cross between a lizard and a dolphin, without the dorsal fin. Paleontologists are not certain what drove the animals to adapt to life in the water 250 million years ago. This period coincided with one of the greatest mass extinctions in history. Ichthyosaurs were top-level predators in the ocean, with few natural threats. The name means "fish lizard."
Live birth, or vivaparity, in reptiles has repeatedly developed and died out throughout the history of the animals. More than 100 times, reptiles switched between laying eggs and giving birth to live offspring. When reptiles first took to the oceans, the first species crawled back up onto land in order to give birth. In modern times, reptiles lay eggs as part of their reproductive cycle.
The fossil was discovered by accident, by paleontologists searching for Saurichthys fossils in China.
Montani believes one baby was stillborn, and the mother may have died from complications during childbirth of her second baby. This theory would explain the positions of the young reptiles.
Only one other fossil showing this species of creature giving birth has ever been found. The earlier find was 10 million years younger than this artifact, making this rare fossil even more valuable to scientists.
Unlike land animals, marine mammals usually give birth tail first, possibly to prevent suffocation. In this fossil, the baby being born was traveling through the birth canal head first.
"We always assumed that live-bearing in marine reptiles evolved after they invaded the sea, partly because of this difference. Now the new fossil shows that the most primitive marine reptile gave birth head first. This strongly suggests that they inherited live-bearing from their land ancestors," Motani told the BBC.
The National Geographic Society and National Science Foundation helped to fund the research. Details of the fossil are profiled in the online scientific journal, Plos One.