In a retrieval once thought unattainable, scientists have recovered and identified proteins in a bone of a well-preserved Tyrannosaurus rex that lived and died and was fossilized 68 million years ago.

The scientists say the success, with advanced research techniques, opens the door for the first time to the exploration of molecular-level relationships of ancient, extinct animals, instead of just relying on their skeletal remains.

Dinosaur fossil hunters are planning nine expeditions this summer to search wide and deep for more specimens as promising candidates for similar tests. A few large dinosaur bones already in laboratories may be examined for surviving traces of organic matter.

The earliest previously identified ancient proteins were from mammoths that died about 300,000 years ago. The oldest confirmed samples of DNA, a more direct bearer of information of molecular evolution, but more degradable, have come from Neanderthals that lived 30,000 to 50,000 years ago. The extraction of DNA would be necessary for studies in dinosaur genetics and for cloning experiments.