The fossilised remains of a gigantic 10m-long predatory shark have been unearthed in Kansas, US. 美国堪萨斯州发现一具10米长的巨大食肉鲨鱼的骨骼化石。
A nurse shark may be similar in shape but not size to the prehistoric fossil Scientists dug up a gigantic jawbone（颚骨） , teeth and scales（鳞屑） belonging to the shark which lived 89 million years ago.
The bottom-dwelling（住处） predator had huge tooth plates, which it likely used to crush large shelled animals such as giant clams（蛤蚌） .
Palaeontologists already knew about the shark, but the new specimen suggests it was far bigger than previously thought.
The scientists who made the discovery, published in the journal Cretaceous Research, last week also released details of other newly discovered giant plankton（浮游生物） -eating fish that swam in prehistoric（陈旧的，史前的） seas for more than 100 million years.
But this new fish, called Ptychodus mortoni, is both bigger and more fierce, having a taste for flesh rather than plankton.
It may even have been the largest shellfish（甲壳类动物） -eating animal ever to have roamed the Earth.
Dr Kenshu Shimada of DePaul university in Chicago, Illinois, US found the fossilized remains of the shark in rocks known as the Fort Hays Limestone in Kansas.
"Kansas back then was smack in the middle of an inland sea known as the Western Interior Seaway that extended in a north-south direction across North America," says Dr Shimada.
Along with a piece of jaw, Dr Shimada and colleagues uncovered a piece of jaw, teeth and scales.
"Although it represents a fraction of the entire body of the shark, the jaw fragment is gigantic. The estimated jaw length was almost 1m long, and that would suggest that the shark was likely at least 10m in length," says Dr Shimada.
Due to the lack of a complete skeleton, it is difficult to gauge（估计，测量） the physical appearance of the shark.
But Dr Shimada suspects it had a body shaped much like that of a modern nurse shark (Ginglymostoma cirratum护士鲨), with a broad rounded head and stout body.
