This learn node features a tiny dinosaur with big canine teeth that the Natural History Museum reports shows for the first time how one of the earliest dinosaurs grew into an adult. The webpage explains:
The turkey-sized reptile called Heterodontosaurus lived around 190 million years ago in the Early Jurassic period and had an unusual combination of molar-like and canine teeth.
Reptiles usually have small same-sized teeth along the length of their mouth but Heterodontosaurus had 2 fang-like canines at the front.
The image posted here is from a video narrated by Dr. Richard Butler, a dinosaur expert at the museum and featured on the page linked above.
For nodes of related learning: An excellent overview article about Anatomy and Physiology of the Reptile Mouth is provided at PetEducation.com. For time frames for the dinosaurs, the big picture can be seen in the Chart of Geological Ages at Connexions.
The image for this learn node is a chameleon from an animation in the terrific tutorial Optics for Teens created and hosted online by the Optical Society of America. If a look through the tutorial makes you curious to learn more about optics, a full Optics course is offered by MIT Open Courseware (tree illustration from Lec# 3). If your interest is roused to know more about chameleons the report of scientists developing computer models for learning about chameleon habitats in Madagascar is offered here by the American Museum of Natural History. And you can learn a lot more about these amazing lizards at the San Diego Zoo’s Chameleon page. There the optical mastery of chameleons is described:
The chameleon’s eyes are the most distinctive among the reptiles. Each eye has a scaly lid shaped like a cone, with only a small, round opening in the middle for the pupil. The chameleon can rotate and focus its eyes separately to look at two different objects at the same time! This gives it a full 360-degree view around its body. When the chameleon sees prey, both eyes can focus in the same direction to get a clearer view.
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