An article published in the journal “National Science Review” reports evidence of the identification of proteins, chromosomes and DNA markers in the fossil cartilage of a Hypacrosaurus stebingeri nestling, a dinosaur belonging to the hadrosaur family dating back to around 75 million years ago, in the Cretaceous period. A team of researchers led by Alida Bailleul of the Institute of Vertebrate Paleontology and Paleoanthropology, China, used chemicals that bind to DNA in living cells on fossil bone fragments resulting in a fluorescence indicating that they bonded to the original molecules and not to external contaminants. Jurassic Park remains science fiction because the fragments found may have undergone various alterations but any trace of cell structures, proteins and chromosomes could offer new information on these dinosaurs.
Hadrosaurs were the so-called duck-billed dinosaurs because of the particular shape of their snout. The genus Hypacrosaurus was identified in 1913 with the species Hypacrosaurus altispinus, but in 1994 a second species was identified, named Hypacrosaurus stebingeri, of which in the 1980s they discovered in the Two Medicine Formation in Montana, USA, fossils that include several stages of growth, from the egg to the adult specimen.
The nestling specimens of Hypacrosaurus stebingeri (bottom photo of a specimen ©Ghedo) had skull bones not yet fused, but some of them had cartilage plates that fused later. Observations of exceptionally preserved microscopic structures that resembled the types of cells found only in cartilage prompted Alida Bailleul, when she was still studying for her doctorate, to conduct more in-depth examinations that began in 2010, assuming that the conservation of cellular structures could extend to molecular level.
Specific stains, as in coloring chemicals, that react with the collagen of the type present in the cartilages reacted with the skull part of Hypacrosaurus stebingeri which contained cartilage tissues but not with the surrounding bone part. Other similar tests were performed using substances that bind to DNA fragments, which reacted with isolated cartilage cells, confirming the idea that some DNA fragments could remain in the cells.
Cell structures had previously been identified in dinosaur bones and certain biomolecular markers were discovered in fossil organisms, but they were traces of protein remains. In this case, the researchers went further by identifying molecular structures at the level of proteins and DNA fragments.
The top image (Courtesy Bailleul et al. All rights reserved) shows some images of the results compared to emu cells. (A, B, E) cells of the type known as chondrocytes indicated by green arrows. Subsequently, Hypacrosaurus stebingeri cells were isolated as single (A) and double (B) cells. The comparison between chondrocytes of Hypacrosaurus stebingeri (C) and of emu (F) with a stain that reacts to DNA. Chondrocytes of Hypacrosaurus stebingeri (D) and emu (G) show a similar bond exposed to the same stains.
These results raise the question of DNA fossilization. Normally, DNA degrades over time and after a few million years no traces remain. However, the cartilage structures may have protected the DNA of Hypacrosaurus stebingeri because they’re not porous like bones and in a calcified fossil cartilage the cells could have been trapped and isolated while also retaining fragments of complex molecules such as proteins and DNA.
Even in the best conditions, alterations may have occurred and DNA probably got fragmented. However, each complex molecule identified can provide new information on these dinosaurs. Basically, we didn’t come close to a the sequencing of dinosaur DNA with the possibility of having a Jurassic Park, but sophisticated tests on some particularly well preserved fossils could be very useful to paleontologists.
