REVISION SHOWING THAT DINOSAURS WERE WARM-BLOODED ANIMALS

Dinosaurs are said to be the very large animals that have ever existed. According to the dinosaur fossils they were dated about 230 million years ago. Madagascar is situated on the South East side of Africa and this is were the oldest dinosaur fossil was discovered. The first dinosaurs that were found were slightly built and their height was about 3 to 3.5 metres long. They imposed very different diets, some were carnivores, herbivores, omnivores and others were insectivores.

There has been a great debate going on about whether dinosaurs were warm-blooded or cold-blood. Scientists have conflicting opinions on this matter. "Paleoanthropologists think that all dinosaurs were warm-blooded as modern mammals and birds because they have the same metabolic rate. Other scientists think that the biggest dinosaurs could have warm bodies because of their large body size. Generally if all the animals were examined at a proper time they will all appear to be warm blooded because their internal bodies are the same.

The mechanism by which the body temperature is maintained is more important. This can be explained simply by using two terms which are ectothermic and endothermic. Ectothermic animals rely on heat from the outside environment to maintain their body temperature while endothermic animals use the heat generated from inside their own bodies by the metabolic process, they are composed of bodies with a higher metabolic rate.Once it was believed that all dinosaurs were cold blooded but now much evidence proves that at least some were warm blooded. All creatures whether warm-or cold-blooded use the same biochemical processes, enzymes and substrate to produce energy. All chemical reactions involved have a particular optimal temperature"(1).
There is no definite answer about whether dinosaurs are warm- or cold- blooded but in the 1970s scientists began to look at some evidence showing that dinosaurs were maybe warm-blooded. Recent studies are showing that dinosaurs were neither warm-blooded like mammals nor cold-blooded like reptiles but in between.

The isotope of their bones shows that they are warm-blooded. Warm-blooded animals grow more quickly than cold blooded ones. "Dinosaurs grew very fast; this was proved by Jack Horner through the bones of a tiny baby dinosaur found in hadrosaur nests. The bones show that baby dinosaurs reach a considerable size while still in the nest. Additional evidence about the growth was found in the microscopic structure of the bones where it was observed that dinosaur bones are rich in the passage ways called Halversian canals which transport nutrient-laden blood to the cells that lay down new bones"(2). This conflict will never end because recent studies also show that the heart of a herbivore dinosaur was studied and it consisted of four chambers instead of three which is common in a warm-blooded animal.

If dinosaurs were warm-blooded then their lives would be more like mammals than reptiles, because reptiles like snakes and lizards spend most of their time moving from one place to another looking for a more warmer area just as they do during winter when they hibernate.

Reference

1. Feduccia, A. 1974. Dinosaurs and Archaeopteryx [Internet] 2006 May 10; 09:05 UTC [Cited 2006 May 10] Available From:
http://www.isgs.uiuc.edu/dinos/de_4/5c51d90.htm

2. Bakker, R. 1972. Anatomical and Ecological Evidence of Endothermy in Dinosaurs [Internet] 2006 May 10; 10:15 UTC [Cited 2006 May 10] Available From:
http://www.dinoruss.com/de_4/5c51d90.htm

Dianah Nangammbi
Cilla CSIR
P.O Box 395
Pretoria
0001
Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/