Implications of the Dinosaur Heart Discovery
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The article from Science News, “Telltale Dino Heart Hints at Warm Blood”, by Tina Hesman and the Journal article it was based on from Science, ”Cardiovascular Evidence for an Intermediate or Higher Metabolic Rate in an Ornithischian Dinosaur”, by Paul Fisher and others both offer a new perspective on the topic to be discussed, however there are some key differences between the two articles. How the two articles differ will be discussed later on in the paper. Both of the articles discuss the finding of a heart in a dinosaur that when studied challenges a common belief about dinosaurs hearts.
Now here is some background information on the dinosaur that is causing this stir because of its heart. The dinosaur is a Thescelosaurus, which means wonderful lizard. The average length of the Thescelosaurus is three to four meters, nine to twelve feet, long with an average weight of three-hundred kilograms, or about six hundred and sixty two pounds. They lived from the Campanian age to Maastrichtian age which are the later stages of the Cretaceous period. Another distinguishing physical feature of Willo is the bird-hips that the dinosaur has instead of the lizard hip. They have primarily been found in Alberta, Saskatchewan, Colorado, Montana, South Dakota, and Wyoming. As far as their remains are concerned there is one complete skeleton, eight partial skeletons, elements, and teeth (Dinosauricon).
Dinosaurs are often compared to and resemble modern day reptiles. Scientists will study how these modern day reptiles behave, look, act, and move to draw conclusions on how the dinosaurs would behave, look, act, and move. They also look at the intern make-up of the modern reptiles to predict how the dinosaurs internal make up would be. However, a recent discovery in South Dakota is stirring up some controversy (Hesman). While Mike Hammer was walking around a ranch in South Dakota he stumbled across a “big-eyed” dinosaur that he now refers to as Willo. The thing that caught his eye was the chest cavity of the dinosaur, upon further investigation he found a rock that was preserved in the curve of the dinosaur’s ribs, he was convinced that this rock was once a heart. Hammer then went on to take the dinosaur fossil in for a medical X-ray scan, this X-ray showed evidence that could change how we think about dinosaurs.
This fossil heart was built more like a birds and mammals heart that that of a reptile heart. Like a bird or mammal, this heart probably had four chambers with a single aorta. An aorta is a large artery that carries blood to the body (Hesman). This is unique because, with the exception of the crocodile, modern reptiles have a three-chambered heart with a single ventricle with a pair of aortas arising from the ventricle. So, mammals, birds, and this dinosaur have a single aorta where as “(A)ll modern reptiles have paired systemic aortas (Fisher)” that distribute blood to the body. In living reptiles, oxygenated blood from the lungs and deoxygenated blood from the rest of the body end up mixing together, thus reducing the amount oxygen content of the blood. Whereas, in birds and mammals the single aorta and two separated ventricles ensures that only completely oxygenated blood is distributed to the body (Fisher). With This setup, it is easy to tell that hearts with one aorta are more efficient at delivering oxygen to the body. These more efficient hearts could support a more active animal and that dinosaurs would have higher metabolic rates (Hesman).
Talked about in Science News article but not even mentioned in the journal article from Science was the possibility that this heart could help prove, or at least provide some evidence that dinosaurs were actually warm blooded, not the “cold blooded killers” they are often thought to be. The higher metabolic rates that a more efficient, single aorta heart, could produce is stated as being a prerequisite for being warm-blooded.
Even though this fossil heart is remarkably well preserved, the fossil has lost some components that would support this theory that the dinosaur only had one aorta. A pulmonary vessel, the vessel that carries blood to the lungs, is obviously missing. With its absence there is a possibility Willo had a second aorta. However, the aorta is much “heartier” and therefore is more likely to be able to survive in fossil form (Hesman). Where the pulmonary vessel will sometimes collapse once the animal dies, and this would lead to it disintegrating much easier (Fisher).
This find has the researchers who found and have dealt with the heart fossil to urge other fossil hunters to look for traces of internal organs before an excavation goes under way. “In the old days, this would have just been [regarded as] a hard rock in the way, and I would have destroyed it,” said hammer. This means that researchers, fossil hunters, and excavators may have been throwing away some of the best parts and best indicators to how dinosaurs worked internally. If researchers were always aware of the possibility that internal organs might be preserved and responsibly went about fossil findings that way, it is only imaginable to think of all the information and data that science would have on the anatomy of dinosaurs that is currently either an educated guess or just totally up in the air (Hesman).
In conclusion, I feel that discovery of a dinosaur, the Thescelosaurus, with a heart that possibly only has one aorta, instead of the usually mandatory two aortas for reptiles is quite remarkable and also very important. Both the article from Science News and the article from the journal Science, agree that the lack of a second aorta puts into question the metabolic rate for the dinosaur or for that matter for all different types of dinosaurs that may also only have one aorta. The only thing that I question is why the article and not the journal made the conclusion that because of the increased metabolic rate due to the heart with one aorta the dinosaur would have possibly been warm blooded. This would be, especially from what I know, an enormous discovery for the dinosaur community. If the roles were reversed, the journal had the possibility of the dinosaur being warm blooded and the article failed to mention it I would be more likely to believe it. At the end of the article the author clearly state that an evolutionary change like this could be caused by high blood pressure not metabolic rate. I also found the article in Science News much more reader friendly. The journal article was defiantly written for readers with scientific backgrounds. I found myself struggling not only on the scientific terms that have to deal with the dinosaurs, but also the medical jargon that was used to describe the heart and its functions. I found these two articles very informative and also very interesting.
Fisher, Paul. 2000. Cardiovascular Evidence for an Intermediate of Higher Metabolic
Rate in an Ornithischian Dinosaur. Science, v.288, p503-505.
Hesman, Tina. 2000. Telltale Dino Heart Hints at Warm Blood. Science News,
v. 157, p260.