More Examples of Exceptional Preservation in Fossil Reptiles
How could structures this delicate survive the ravages of tens or hundreds of millions of years?
A video posted by Reuters shows the “‘oldest in world’ fossilized blood vessels.” Found by Polish scientists, this fossil reptile appears to have original traces of proteins—including the amino acids of collagen—in rock said to be 240 million years old. It clearly shows traces of blood vessels and their “molecular remnants” in bones found during an excavation. “Researchers were soon able to show that there was organic matter from prehistoric animals present in the bone,” including “fragments of amino acids that are typical components of collagen.” This was apparently “among other proteins” detected. This new claim is much older in the evolutionary time scale than the previous record, which they cite as 80 million years. “The latest discovery goes back 3 times further,” the video concludes.
Impressions of chromatophores in fossil snake skin have allowed paleontologists to infer the color of a snake found fossilized in Spain. The particular chromatophores have the shape of carotenoids that would have endowed the snake, said to be 10 million years old, with a pale green color. “The findings suggest that the animal had a pale belly and a green back and sides, with brown–black and yellow–green blotches — possibly a form of camouflage,” Nature News says. The chromatophores are apparently mineralized, not original tissue. Still, the preservation is so exceptional, the researchers say in their paper in Current Biology that they cannot rule out some original material present:
Certain pigments, including melanins, pteridines, and carotenoids, are known to have an affinity for metal cations. Elevated levels of sulfur in the dermal chromatophores and collagen fibers may reflect the presence of sulfur-bearing moieties in the original tissue structures or the incorporation of sulfur (in the form of sulfate) into the replacement phosphate during mineralization. There is no evidence, however, for partitioning of trace elements among the various chromatophores in the fossil snake skin (Figure 3). This may reflect concentrations below detection limits (<100 ppm) or overprinting of the original trace element chemistry during the mineralization process. The fossil chromatophores are therefore interpreted on the basis of their size, geometry, and, in some examples, internal structure compared with those in extant reptiles.
Before this, colors were inferred from the presence of melanosomes that contain the dark pigment melanin. This was the first time that chromatophores containing carotenoids have been detected in a fossil. The search should accelerate for more, the scientists say:
Our discovery confirms that direct evidence for diverse coloration mechanisms can be preserved in fossils via an alternative taphonomic pathway, namely replication of tissues in authigenic minerals, and that the high fidelity of preservation allows original coloration to be reconstructed. The various factors that control phosphatization of soft tissues are known, and fossil examples of phosphatized skin are not uncommon; importantly, they have been reported from various taxa and fossil localities, suggesting that our discovery has broad applications in the fossil record. Our discovery should prompt a search for other examples and is likely to be the first example of a recurrent phenomenon. Integuments replicated in calcium phosphate are obvious targets for further attempts to reconstruct color patterns derived from melanin and, critically, other pigments and structural coloration mechanisms across diverse vertebrate groups.
The discovery raises a question. After decades and centuries of looking at fossils, why was this not found before now? Were paleontologists not looking?
Ironically, Current Biology simultaneously published a book review written by Rick Shine, lamenting the fact that most human beings only know about reptiles and amphibians through mythology. The book by Marty Crump recounts various myths about these animals. Science is so much better, Shine thinks, as he lobs some sarcastic aspersions at those he considers anti-science:
Most human beings in the world ‘know’ about reptiles and amphibians through myth, not science. Even in developed countries, the general public is woefully ignorant of reptiles and amphibians (and of evolution, and ecology, and physics, and chemistry, and…). Indeed, many of Crump’s fables come from Louisiana or Essex, not Islamabad or Palembang. Of the teeming millions of humans on the planet, few have access to a scientific education. And even of those that do, folk beliefs often trump schoolbooks as a source of trusted information (and I use the word ‘trump’ advisedly).
How ironic it would be, indeed, if future scientists look back on the Darwinian explanation for reptiles, and the long ages of their emergence by unguided processes, as a regrettable myth.
He who laughs last laughs best. If you think that complex specified information in reptile and amphibian genes and body types show evidence of intelligent causes instead of “stuff happens,” you should be having some roaring guffaws right now.