Nanosaurus was an Ornithischian dinosaur named by paleontologist Othniel C. Marsh in 1877. It may be a juvenile Tyrannosaurus rex . The only known skull has been CAT-scanned by Bakker. He thinks that Nanotyrannus is an adult, but many other paleontologists, like Thomas Carr disagree, and think the Nanotyrannus is a juvenile T. rex. This plant-eating dinosaur lived during the Cretaceous period .
Nares are the openings in the skull for the nostrils.
Some life forms survive and reproduce because they are better suited to environmental pressures, ensuring that their genes are perpetuated in the gene pool. The shell is divided into chambers. The nautiloid head has well-developed eyes and tentacles that can grasp prey. They were most abundant during the Paleozoic Era, roughly 400 million years ago. Some Nautiloids evolved into Ammonoids.