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Model of a dinosaur egg. Dinosaur reproduction shows correlation with archosaur physiology, with newborns hatching from eggs that were laid in nests. [1] [2] Dinosaurs did not nurture their offspring as mammals typically do, and because dinosaurs did not nurse, it is likely that most dinosaurs were capable of surviving on their own after hatching. [3]
In dinosaurs, the anatomy of the braincase is conservative, but for this reason can be used to infer relationships of a group when other skeletal features underwent changes so profound that their origins can no longer be traced. The braincase may also allow for reconstructing the brain and inner ear, with inferences on senses and intelligence. [20]
Dinosaur fossils are not limited to bones, but also include imprints or mineralized remains of skin coverings, organs, and other tissues. Of these, skin coverings based on keratin proteins are most easily preserved because of their cross-linked, hydrophobic molecular structure. [72]
Regardless of the object's identity, it may have little relevance to dinosaurs' internal anatomy and metabolic rate. Both modern crocodilians and birds, the closest living relatives of dinosaurs, have four-chambered hearts, although modified in crocodilians, and so dinosaurs probably had them as well. However such hearts are not necessarily ...
Most elongated eggs were laid by theropods and have an avian-like eggshell, whereas the spherical eggs typically represent non-theropod dinosaurs. [13] Diagram of a two-layered eggshell. Fossil dinosaur eggshells, like modern bird and reptile eggshells, are made up of calcium carbonate crystal units.
The UK's biggest ever dinosaur trackway site has been discovered in a quarry in Oxfordshire. About 200 huge footprints, which were made 166 million years ago, criss-cross the limestone floor.
The hemipenis is the intromittent organ of Squamata, [4] which is the second largest order of vertebrates with over 9,000 species distributed around the world. They differ from the intromittent organs of most other amniotes such as mammals, archosaurs and turtles that have a single genital tubercle, as squamates have the paired genitalia remaining separate. [5]
A microbiologist is proposing the idea that the reign of dinosaurs forced mammals to speed up their reproductive cycle, eliminating key longevity genes. Historic Dinosaur Dominance May Cause ...