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Dinosaur digestive aids.

Dinosaur digestive aids

Paleontologists rarely find hard evidence concerning the internal organs of extinct animals because fossilization usually does not preserve soft tissue. But an excavation in New Mexico of the largest known dinosaur has unearthed unusual clues about this animal's digestive tract.

David D. Gillette and his colleagues have discovered about 180 small stones buried right next to the skeleton of a seismosaurus, a 140- to 160-foot-long diplodocid dinosaur that they have been excavating for five years. Most of the smooth, rounded stones are the size of a plum, although their diameters range from a small as a dime to as large as a grapefruit. Gillette, Utah's state paleontologist, identifies the rocks as gastroliths -- so called "stomach stones" that certain animals hold within their digestive tract to grind food.

Paleontologists often treat report of gastroliths skeptically because rivers can produce very similar stones. But the seismosaurus skeleton lies in a sandstone that contains no other rocks or pebbles aside from the ones found next to the bones. The researchers even uncovered some stones buried within the seismosaurus' rib cage. The stones were arranged in two distinct clusters: one smaller group near the pelvic region, and a larger assemblage near the base of the neck. The region between these groups contained no stones.

The placement of the stones indicates seismosaurus had a crop and a gizzard, somewhat similar to the organs in many modern birds, suggests Gillette. He says it therefore appears that as the dinosaur swallowed, its diet of plant material would pass from the crop - where gastroliths ground it - to a gastrolith-free stomach where digestive enzymes attacked the food, then into the gizzard for more grinding, and finally into the intestines.

The one grapefruit-sized gastrolith puzzles Gillette because all the other rocks have far smaller diameters. He speculates that ingestion of the huge stone may explain the death of this seismosaurus, which otherwise appeared healthy.
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Title Annotation:gastroliths or 'stomach stones'
Author:Monastersky, Richard
Publication:Science News
Date:Oct 20, 1990
Previous Article:Reining in a galloping Triceratops.
Next Article:Bound for the sun, by Jove.

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