I've always taken the importance of fossils as complete forms for granted, especially as evolutionary proof. Two questions in this regard:

1. First, how does a fossil expert take cracked, fossilized remains deformed under immense pressures and put them in the right places?
2. How certain are fossil experts that the configurations are correct?


Hi, Dave.  Excellent questions.  If we had really good answers, then palaeontology would be a lot easier.

First of all, each newly discovered fossil is interpreted in the light of what we know about living animals.  When we're dealing with animals pretty similar to what's alive today, things are easier: for example, a bone from a sabre-tooth cat should have enough similarities to the same bone in modern cats that a good mammalogist can identify it pretty easily.  With older groups, comparisons to modern animals are less useful, but still have a role to play: for example, there are similarities between the vertebrae of sauropod dinosaurs and modern birds -- even though some sauropods had individual vertebrae longer than nearly all birds' whole necks!

Second, each newly discovered fossil is interpreted in the light of all the other fossils already known.  This means that the occasional very complete specimen is valuable as a sort of "Rosetta Stone" for interpreting related fossils.  Until something like that is available, all guesses are open to error, and all kinds of mistakes do get made.  To pick a couple of famous examples, the dinosaur Iguanodon was first reconstructed as a heavy rhinoceros-like quadruped with a nose-horn, rather than as the occasionally bipedal dinosaur with thumb-spikes that we are familiar with today; and the long-necked sea reptile Elasmosaurus was originally put together with its head at the wrong end!

Even now, we make plenty of mistakes.  To pick a recent example, the vertebra from which the dinosaur "Ultrasauros" was named was first thought to be from the shoulder region of a brachiosaurid sauropod.  Restudy showed it to be from lower back region of a completely different kind of sauropod.

So the answer to your second question, "how certain are fossil experts that the configurations are correct?" is often "not very".  But thankfully there are exceptions such as the very complete T. rex skeleton "Sue" where we can be very, very confident.

Finally, I should say that these problems are much less acute with smaller animals than with the giant sauropod dinosaurs that I like to work on.  It's not that unusual to find whole skeletons of little lizards, fish and suchlike.  But in general, the bigger the animal, the worse the chancer of finding all of it.

Last edited by Mike Taylor (3rd Mar 2007 00:18:03)