May 15, 2013
Abused Ichthyosaur Fossil Deepens Mystery Of Dolphin-Like Dinos
Brett Smith for redOrbit.com - Your Universe Online
A fossil previously used as a stepping stone for mules has deepened the mystery surrounding the evolution of ichthyosaurs, dolphin-like marine reptiles that were contemporaries of the dinosaurs.
According to a newly published report in the journal“¯Biology Letters,“¯an analysis of the fossil, dubbed Malawania anachronus, has suggested that ichthyosaurs survived well into the Cretaceous period and did not go extinct 66 million years before in the Early Jurassic as previously thought.
"They ranged in size from less than one to over 20 meters in length,” said lead author Valentin Fischer from the University of Liege in Belgium. “All gave birth to live young at sea, and some were fast-swimming, deep-diving animals with enormous eyeballs and a so-called warm-blooded physiology.”
The analysis also revealed that ichthyosaurs from the Cretaceous weren´t very different than their Early Jurassic ancestors — an unusual amount of continuity for a reptile that had previously shown evidence of a rapid evolution.
"Malawania's discovery is similar to that of the coelacanth in the 1930s: it represents an animal that seems 'out of time' for its age,” Fischer explained. “This 'living fossil' of its time demonstrates the existence of a lineage that we had never even imagined.”
“Maybe the existence of such Jurassic-style ichthyosaurs in the Cretaceous has been missed because they always lived in the Middle-East, a region that has previously yielded only a single, very fragmentary ichthyosaur fossil,” he added.
The new ichthyosaur fossil was discovered in the Kurdistan region of Iraq during the 1950s by British petroleum geologists.
"The fossil — a well-preserved partial skeleton that consists of much of the front half of the animal — wasn't exactly being treated with the respect it deserves,” said co-author Darren Naish of the University of Southampton.
“Preserved within a large, flat slab of rock, it was being used as a stepping stone on a mule track. Luckily, the geologists realized its potential importance and took it back to the UK, where it remains today.”
Archeologists began studying the fossil in the 1970s, led by ichthyosaur expert Robert Appleby who was with University College, Cardiff.
"Robert Appleby recognized that the specimen was significant, but unfortunately died before resolving the precise age of the fossil, which he realized was critical," said co-author Jeff Liston of National Museums Scotland. "So continuation of the study fell to a new generation of researchers."
In the new study, researchers noted that“¯Malawania anachronous — Latin for 'out of time swimmer´ — represent a remarkable amount of evolutionary stability for a marine reptile.
By analyzing microscopic spores and pollen preserved in the same rock as the fossil and other archeological evidence, the team was able to trace the evolutionary history of Cretaceous ichthyosaurs, including ichthyosaur groups that appeared during the intermediate time periods of the Triassic and Jurassic time periods.
The researchers concluded that the final extinction of the ichthyosaurs occurred about 95 million years ago, long before the extinction event that marked the end of the Cretaceous and the reign of the dinosaurs.