Digging dinosaur bones is, of course, fun. It’s the identification of dinosaur bones that can be perplexing and often frustrating.
If one is lucky enough to find an articulated dinosaur, the ID is easy as the bones are in their proper places. Finding bones in a bone bed - in which many bones of different dinosaur species are found together - makes identification much more difficult. Finding only a partial bone further increases the degree of difficulty. So, how do you go about properly identify those initial UDO’s or “unidentified dinosaur objects”?
Reference books and images on the Internet are great places to begin. Unfortunately, you’re looking at only two-dimensional images, and this may not be good enough for a proper identification.
One of the best resources is networking with paleontologists who are willing to examine photos and share their wisdom. They often have access to large collections and have seen thousands of bones up close and personal, giving them a keen eye for evaluating certain diagnostic features that may be the determining factors. Here are two recent cases that show how good working relationships can solve problematic IDs:
UDO #1: This bone from the digsite remained unidentified for a number of years. It has an interesting shape and very large ‘sutures’ along one side that mimic a saw blade. Initial thoughts were that it was either a skull part (possible the top of skull) or derived from the sacral (pelvic) region of a Sauropod dinosaur. After several paleontologists reviewed numerous photos of the specimen, initial IDs ranged from skull element to plesiosaurus ischium to turtle shell remnant.
But, one of the paleontologists had made the effort to look at bones in his collections. Eventually, a consensus was reached it was a portion of a sacral rib from a Camarasaurus. Now, if other similar bones are found, ID will be much simpler.
UDO #2: This challenging bone has not yet been conclusively identified - but we’re getting closer. It's a tibia (lower leg bone) that does not match anything excavated or seen at the digsite todate. A paleontologist visiting the digsite came up with the tentative ID of Elaphrosaurus. (We even wrote a blog article about it in 2012.) But, we suspected that this identification was a bit of a stretch. After all, Elaphrosaurus is extremely rare and the possibility of finding its bones at the site is iffy.
Photos of the bone were sent recently to another paleontologist and his analysis yielded the very creative and informative comparative diagram you see here. In this diagram, our mystery tibia (#1 in the chart) has been put in shape-related context with other similar bones from Jurassic Period dinosaurs. (Bones are not shown not to-size.)
Although the ID is still tentative, this bone is now believed to be from the small, Jurassic Theropod dinosaur, Coelurus. What makes it even more interesting is that this bone is apparently one of the most complete tibia from this species, and therefore scientifically significant.
Eventually, this specimen may find a home in a museum where it will be studied and offer additional clues to Coelurus osteology.
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Proper Identification of Dinosaur Bones 
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