A mummified fossil of common species of hadrosaur was found recently in South Dakota that showed that this particular hadrosaur had a rooster-like fleshy comb on its head. Many hadrosaurs have exotic extensions of their cranial bones but this evidence that even the “boring” hadrosaurs had fleshy projections suggests that the hadrosaurs were an even more flamboyant group than previously recognized.
In an article “Dinosaur mummy’s fleshy head crest” (Ella Davies in BBC Nature) describing this dinosaur “mummy” fossil the following explanation for the remarkable preservation of this dinosaur:
Experts suggest that when an animal was instantly buried in certain sediments, decay was slowed down through a lack of oxygen and soft tissues were mineralized.
This process is called permineralization and is also responsible for the formation of petrified wood. Skin impressions and other soft tissue preservation are considered rare but are not unknown. In fact, skin impressions may be quite common but the bones are usually targeted and the mineralized material around the bones is far more difficult to examine and thus is often lost in preparation.
Instant burial is the key to soft tissue preservation
Not exactly a shocking revelation but one worth thinking about for a moment. Dinosaur bones come in many forms but most are found as just partial skeletons or only a few random pieces such as a jaw bone here and a femur there. Many bones have marks on them from scavenging. The picture formed from these bones is one of dinosaurs that have died naturally or otherwise and their bodies scavenged. For the majority of dinosaurs the flesh will have been picked off the bones or possibly decayed leaving the naked bones. If those bones get buried within a short period of time they may eventually get mineralized into the fossils we find today. But there are some bones that are found as part of complete or nearly complete skeletons. These dinosaurs may also have died and their flesh decayed prior to burial but is not likely to happen.
More rarely, a dinosaur might be buried right at the point of death in which case all the soft tissues will be preserved to some extent. In most cases this burial will be shallow and oxygenated ground water and microorganisms will lead to a rapid decay of tissues resulting in a mixing of the rotting flesh and its biomolecules with the sandy matrix. Eventually the entire sand matrix that encased the dinosaur will become rock but the impression of the fleshy tissues will not be discernible and only the bones being more resistant to decay may be preserved. However, under the right conditions (low oxygen, fast burial etc..) the flesh will remain intact long enough that the matrix around the animal will set before that decay can happen leaving the impression of where that tissue had been. This is really how bones are also preserved. Typically they are more resistant to decay and thus last long enough for minerals to slowly replace the organic components of the bone. Under conditions of quick burial in low oxygen environments, the same mineralization process can happen with soft tissues.
So what we see is that the dinosaur fossil record is consistent with a world that has experienced a diversity of preservation conditions. Some bones are found as mixed up pines of bones in river bed sediments like I observed on the dinosaur trail near Moab UT (see A tour of the dinosaur trail of Mill Canyon near Moab UT). Others are found as complete skeletons apparently buried in large sandstorms. Some are found in sinkholes and others are preserved via quick asphyxiation and burial in volcanic ash. Others appear to have drowned and been covered by flood sediments.
Soft tissue preservation is a challenge for young earth creationists.
If you come from a young earth creationist’s (YECs) background or are even just vaguely familiar with creationism then you will think I have my statement backwards. Haven’t we all been told by a multitude of creationists’ speakers that any evidence of soft tissues, cells or biomolecules in the fossil record should be scored as evidence for a recent creation. I’m going to cheat for now and not explain why I don’t think this is the case but see some brief remarks I have made in recent posts if you are interested (The mosquito that produced more than a little buzz and Young earth creationism and ancient DNA).
Rather, what struck me about this rooster-like comb on this hadrosaur is that its existence is more of curse than a blessing for YEC apologists. How can that be? Well, where I convinced that a global flood 4 to 6 thousand years ago were responsible for all the dinosaur fossils, then I should EXPECT to find soft tissues preserved to some extent as the norm rather than the exception to the rule. Why? Because the special conditions that are required for preservation of soft tissues like those found in this hadrosaur are just the kind that should have been produced by a global flood. Combine those conditions with its having happened only a few thousand years ago and you have to ask, why don’t we find skin impressions, remains of feathers, and other impressions of large organs (like these combs) and gobs of biomolecules throughout the dinosaur fossil record?
What I am saying is that if you asked a priori what you would expect to see in the fossil record had a flood destroyed all living flesh from the face of the earth in a short period of time and deposited all those organisms in what we call the geological record? I would expect to find a majority or at least a significant number of dinosaurs to be represented as complete skeletons. I would not expect to find rampant evidence of scavenging and given the fast burial I would expect to find the impressions of many parts of their bodies not just their bones since they would have been covered with their flesh intact. Since this happened not long ago I would expect to find very abundant biomolecules, possibly even intact DNA in the material around the bones, and especially in the bones, even if cells themselves were no longer present.
As I pointed out before this is not what we find in the fossil record. We find some but not much evidence of biomolecules and few cases of soft tissue preservation even if be only the impression of where soft tissues once laid. Just look at mammoths and mastodons from the fossil record. Some of these have abundant cells, DNA, hair and sometimes cellular tissues preserved. If these biomolecules could survive for 4000 years then why shouldn’t animals killed in Noah’s flood just a few hundred years earlier not also be expected to be preserved in a similar fashion?