Those Bones Keep Looking Younger and Younger

On August 9, 2010, PloS One published a paper by Johan Lindgren and his colleagues, and it discusses the fossilized remains of a mosasaur that belongs to genus Platecarpus. The fossil is exceptional because it is largely intact, the bones are well-articulated, and it contains soft tissue.

Of course, soft tissue in dinosaur fossils is not new. As I mentioned in a previous post, Mary Schweitzer and her colleagues stunned the world in 2005 by discovering soft tissue in a Tyrannosaurus rex femur that is supposed to be 65 million years old. Some scientists tried to discredit the claim, but it held up under scrutiny. In addition, other fossils that are supposedly millions of years old have been found to contain soft tissue.

So why am I blogging about this particular find of soft tissue in a fossil that is supposedly about 80 million years old? Because the details found in the soft tissue are quite remarkable.

The soft tissue to which I refer is described by the authors as “purplish matter,” and they conclude that it is composed of remnants from the mosasaur’s retina, which is the delicate, multilayered, membrane that lines the inner eye and houses the necessary tissues for sensing light and relaying what is sensed to the optic nerve. How do they come to this conclusion?

First, they make it clear that this soft tissue could not have been produced by bacteria. If you read my previous post about Mary Schweitzer’s find, you will recall that scientists who didn’t want to believe that a 65-million-year-old fossil could contain soft tissue tried to claim it was actually a biofilm made by bacteria. Well, the authors nip that dodge in the bud by stating quite clearly that the remains:

…are embedded inside the fossilized tissues (probably representing their in situ position) rather than forming a superficial coating, as would be expected had they instead been part of a microbial biofilm.

Second, the main reason the authors think the soft tissue comes from the retina of the mosasaur is that it contains small bodies that have all the characteristics of retinal melanosomes. What are retinal melanosomes? They are organelles found in cells that make up part of the retina. Their job is to hold a pigment called melanin, which absorbs light. The melanosomes don’t help the retina detect light; instead, they protect the retina from certain dangerous chemical reactions that can occur when there is a lot of light (which is focused on the retina) and oxygen (which is found in the capillaries that nourish the retina’s cells).

Not only do these meolanosome-like bodies appear right where they should appear if the soft tissue is, indeed, from the mosasaur’s retina, but they don’t appear in other parts of the body. According to the authors:

Moreover, melanosome-like microstructures were not found in any other part of the mosasaur examined under scanning electron microspectroscopy (SEM), including scales, visceral traces, intestinal content, surrounding matrix, and the film that defines the former body outline.

So the case seems pretty strong. These authors have found what appears to be the remains of retinal tissue in a fossil that is supposed to be 80 million years old. As I mentioned in my previous post, laboratory studies seem to indicate that soft tissue decays in a matter of 50 weeks or so, and it was thought that proteins would break down after only 30,000 years, unless special circumstances were present. However, here we have complex cellular organelles in a fossil that is supposed to be about 80 million years old. The very fact that these organelles are present indicate that this fossil isn’t anywhere close to 80 million years old. Instead, given that melanosomes contain proteins, the fossil is probably less than 30,000 years old.

As I have said before, it is a wonderful time to be a young-earth creationist!