Dinosaur Guts Preserved In Fossil Remains Of Previously Unknown Species Show Extraordinary Details

Surprisingly well-preserved fossil muscle fibers, intestines and other tissues have been found along with the bony parts of a juvenile dinosaur, according to scientists.

Originally uncovered in the 1980s by a private collector, the young dinosaur is so well preserved in fossil form that it “shows details of soft anatomy never seen previously in any dinosaur,” paleontologists Cristiano Dal Sasso and Marco Signore report Thursday in the journal Nature.

The remains are thought to be 113 million years old, and came from an unknown species related to the gigantic meat eater Tyrannosaurus rex, the Italian team reports. It was small, about 2 feet long, but would probably have grown to 6 feet in length if it had survived into maturity.

A few remains of dinosaur soft parts have been found in the past, but the Italian team says their small dinosaur reveals an extraordinary amount of detail, including the sizes and positions of organs. And, they say, there is no hint that the animal had feathers.

“A unique, striking feature of the specimen is the preservation of soft parts. Muscles are present,” with individual muscle fibers visible under magnification, the team reports. Also present are the intestine, “positioned farther forward than it is generally thought to be,” plus the colon.

“The gut is surprisingly short and deep … suggesting a high absorption rate for nutrients,” they write. There are also traces of tissue that may be parts of the trachea, and perhaps remains of the liver.

The two Italian researchers - from the Natural History Museum in Milan and the University of Naples - say the dinosaur fossil came from Benevento Province in an area of southern Italy already known for its beautifully preserved fossil fish. The dinosaur’s remains are almost complete, except for part of the legs and much of its tail, the team reports.

Dal Sasso and Signore named the specimen Scipionyx samniticus. It was found lying “on its left side in nearly perfect anatomical articulation.” It was well-preserved because when the animal died it was in a shallow, oxygen-poor lagoon, where deposits eventually turned into limestone. It is the first dinosaur fossil discovered in Italy.

“It’s a fabulous find,” said paleontologist Paul Sereno at the University of Chicago.

“This kind of detail is very, very rare.”

Sereno, who recently announced discovery of a T. rex specimen in Africa, said of the Italian find: “One of the really neat things about this one is that it doesn’t preserve the skin very well. But it has the best intestinal trace I’ve ever seen. That can give you some idea of how it was processing its food.”