Paleontologists have discovered the first dinosaur fossil that has ever been uncovered in the state of Washington, dating back about 80 million years.
The fossil is a partial left femur of a theropod dinosaur, the group of two-legged, carnivorous dinosaurs that includes Velociraptor, Tyrannosaurus rex and modern birds.
It was collected by a Burke Museum research team along the shores of Sucia Island State Park in the San Juan Islands.
Researchers discovered the fossil while collecting ammonite fossils (a creature with a spiral shell) from a marine rock area known as the Cedar District Formation.
They first noticed a small section of exposed bone on the surface of the rocks, then returned with a team of paleontologists to help excavate the fossil.
The fossil is 16.7 inches long and 8.7 inches wide. Because the fossil is incomplete, paleontologists are not able to identify the exact family or species it belonged to.
Christian Sidor, the museum's curator of vertebrate paleontology and colleagues compared the fossil to other museums' specimens and were able to calculate that the complete femur would have been more than 3 feet long - slightly smaller than a T rex femur.
The fossil is from the Late Cretaceous period and is approximately 80 million years old.
"This specimen, though fragmentary, gives us insight into what the West Coast was like 80 million years ago, plus it gets Washington into the dinosaur club," said University of Washington graduate student Brandon Peecook.
Fossilised prehistoric clams were also found inside the hollow part of the bone, which indicates the dinosaur fossilised in marine rock.
These additional fossils are a rare occurrence and provide scientists with a snapshot of other lifeforms that were present where the dinosaur fossilised.
Dinosaurs are found in rocks from the time periods in which they lived (240-66 million years ago). Washington was mostly underwater during this period, so the state has very little exposed rock of the right age.
Because dinosaurs were land animals, it is very unusual to find dinosaur fossils in marine rocks - making this fossil a rare and lucky discovery, researchers said.
The finding was published in the journal PLOS ONE.
