"Long before it's in the papers"
January 27, 2015


Seal-like beast gave rise to dinosaur-era sea monsters, study says

Nov. 5, 2014
Courtesy of UC Davis
and World Science staff

Artist's concept of how the animal may have looked like in life. (Credit Stefano Broccoli/U. of Milan)

Re­search­ers say they have found a fossil of a seal-like an­i­mal that rep­re­sents an an­ces­tral form of gi­ant sea rep­tiles that prowled dur­ing the di­no­saur era.

The full-blown mon­sters, called ichthyosaurs, lived around 200 mil­lion to 250 mil­lion years ago, the so-called Tri­as­sic pe­ri­od. They were be­lieved to have evolved out of land-dwelling an­i­mals, but a “miss­ing link” ty­ing them to such crea­tures was mis­sing.

The new fos­sil is said to fill that gap by dis­play­ing am­phib­i­ous, or both land-and-sea-dwell­ing, ca­pa­bil­i­ties.

“We have this fos­sil show­ing the tran­si­tion,” said Ryosuke Motani of Uni­vers­ity of Cal­i­for­nia, Da­vis, who with col­leagues found the fos­sil in Chi­na’s An­hui Prov­ince.

Courtesy Ryosuke Motani/UC Davis

An es­ti­mat­ed 248 mil­lion years old, it is about 1.5 feet (46 cm) long. The find­ings are de­scribed in a pa­per in the jour­nal Na­ture on­line Nov. 5

Un­like ichthyosaurs fully adapted to sea life, Motani said, this one had un­usu­ally large, flex­i­ble flip­pers that likely al­lowed for seal-like move­ment on land. It had flex­i­ble wrists, es­sen­tial for ground crawl­ing. 

Most ichthyosaurs have long, beak-like snouts, but the am­phib­i­ous fos­sil shows a nose as short as that of land rep­tiles, he added.

Its body al­so con­tains thicker bones than oth­er ichthyosaurs, he added, in keep­ing with the idea that most ma­rine rep­tiles who tran­si­tioned from land first be­came heav­i­er in or­der to over­come rough coast­al waves be­fore en­ter­ing deep sea.

The study’s im­plica­t­ions go be­yond ev­o­lu­tion­ary the­o­ry, Motani said. This an­i­mal lived about 4 mil­lion years af­ter the worst mass ex­tinc­tion in Earth’s his­to­ry, 252 mil­lion years ago. Sci­en­tists have won­dered how long it took for an­i­mals and plants to re­cov­er af­ter such de­struc­tion, par­tic­u­larly since the ex­tinc­tion was as­so­ci­at­ed with glob­al warm­ing.

“This was anal­o­gous to what might hap­pen if the world gets warm­er and warm­er,” Motani said. “How long did it take be­fore the globe was good enough for preda­tors like this to re­ap­pear? In that world, many things be­came ex­tinct, but it started some­thing new. These rep­tiles came out dur­ing this re­cov­ery.”

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Researchers are reporting the discovery a seal-like animal that represents an ancestral form of the sea reptiles that prowled during the dinosaur era. The full-blown monsters, called ichthyosaurs, lived around 200 million to 250 million years ago, the so-called Triassic period. They were believed to have evolved out of land-dwelling animals, but a “missing link” tying them to such creatures was missing. The new fossil is said to fill that gap by displaying amphibious, or land-and-sea-dwelling, capabilities. “We have this fossil showing the transition,” said Ryosuke Motani of University of California, Davis, who colleagues discovered the fossil in China’s Anhui Province. An estimated 248 million years old, the seal-like beast measures roughly 1.5 feet long. The findings are described in a paper published in the journal Nature online Nov. 5 Unlike ichthyosaurs fully adapted to sea life, Motani said, this one had unusually large, flexible flippers that likely allowed for seal-like movement on land. It had flexible wrists, essential for ground crawling. Most ichthyosaurs have long, beak-like snouts, but the amphibious fossil shows a nose as short as that of land reptiles, he added. Its body also contains thicker bones than other ichthyosaurs, he added, in keeping with the idea that most marine reptiles who transitioned from land first became heavier in order to overcome rough coastal waves before entering deep sea. The study’s implications go beyond evolutionary theory, Motani said. This animal lived about 4 million years after the worst mass extinction in Earth’s history, 252 million years ago. Scientists have wondered how long it took for animals and plants to recover after such destruction, particularly since the extinction was associated with global warming. “This was analogous to what might happen if the world gets warmer and warmer,” Motani said. “How long did it take before the globe was good enough for predators like this to reappear? In that world, many things became extinct, but it started something new. These reptiles came out during this recovery.”