Replying to Learn About Dinosaurs!!!

1. Do you believe that some dinosaurs were endothermic? Provide at least five examples of data to support your view. What kind of evidence would provide a definitive test of this idea?

1. haversian bone structure : the outer layer of bones are full of tiny holes for blood vessels, typical on mammals and birds.
2. Complex, four chambered heart is evidence of a great aerobic scope, suggesting activity, and therefore suggesting endothermism
3. Birds are direct descendants of theropods, therefore suggesting that theropods were endothermic.
4. Dinosaurs may be gigantothermic, but this trait does not necessarily characterize the smaller dinosaurs, or even the juvenile larger dinosaurs. Because juveniles of larger species still need to be able to escape danger to survive to adulthood, it is unlikely that they would be ectotherms if the theropods were endotherms.
5. Bodies that appear to be adapted for fast running suggest endothermic metabolisms.

If we were able to analyze living dinosaurs, we would be able to have definitive evidence of this idea.

2. Describe the range of movement or locomotor styles present within and among the various major groups of dinosaurs. For example, which are quadrupedal and which are bipedal? Which groups likely included the fastest dinosaurs and which the slowest? What is the evidence to support your views? Think about both body fossils and trace fossils.

Sauropods were gargantuan quadrupedal dinosaurs. It is likely that they were the slowest moving of the dinosaurs, because of their enormous size. Trace fossils suggest slow paced movement. Ankylosauria and Stegosauria were smaller quadrupedal animals, both built very stout. This suggests that they were both slower moving animals as well. Ceratopsians are mainly quadrupedal, however the bone structure of some species suggest that some might have possibly been bipedal. Ornithopods are a diverse group of mid-sized and smaller dinosaurs. Early ornithopods were smaller and bipedal, suggesting a fairly speedy animal. As the lineage continued, the ornithopods became progressively bigger, with larger front limbs, allowing them to be quadrupedal, and likely slower. Pachycephalosauria were smaller dinosaurs, and bipedal, with a strong, faster build. Theropods were likely the fastest group. All theropods walk bipedally, and are built to be strong and to chase down prey to kill it.


3. Describe at least five groups of non-dinosaurian vertebrates that coexisted with dinosaurs. What unique features allowed them to coexist with dinosaurs? Provide evidence to support your conclusions.

1. Mammals
Small size and the possibility of a nocturnal lifestyle kept them out of the sight of dinosaur predators.

2. Therapsids
A sprawled posture may have prevented them from competing with dinosaurs, as all large forms dies off at the end of the Triassic
3. Crocodiles
The move into the water may have been linked to their move to the water, as there would be no competition between them and dinosaurs.
4. Pleisiosauria
The fact that they lived and found their prey in the water is allowed them to coexist with dinosaurs, because they didn’t have to compete with them
5. Pterosaurs
Many are thought to have filled the niches of today’s birds, which kept them out of the way of dinosaurs, so they didn’t have to compete with them


4. What are the major ideas put forth to explain the functions of horns and frills in ceratopsid (horned) dinosaurs? Which explanations do you regard as most accurate and why? Provide evidence to support your conclusions.

There have been a number of ideas put forth to explain the large horns and frills that can be found on ceratopsids. The three main reasons are for defense/combat, thermal regulation, and sexual appeal. The horns on the nose of these dinosaurs could be used to fight other ceratopsids or predators. They could possibly thrash their head back and forth in an attempt to stab the enemy. Also, the large frill would make the dinosaur look much larger than it really was. The frills were very thin which leads experts to think they may have been used as thermoregulation and to collect heat rather than to stop a predator. And with many unexplained features on dinos and other animals sex appeal is always a factor.