Ichthyosaurs Essay

The ichthyosaurs, commonly known as the fish-lizards, were a very unique species that inhabited the oceans of our planet some 250 million years ago. Exactly what are the ichthyosaurs? These are creatures that evolved from a land species into dominate sea carnivores. Many have speculated on exactly what type of land creature the ichthyosaurs originally evolved from. Scientist believe that its origins are definitely reptile and belonged to a group called Diapsida, which includes lizards, dinosaurs, and crocodiles (Motani, 2000). The first fossils of the ichthyosaurs were discovered in the early1800s. However, after the discovery of the dinosaur, much of the interest in the sea creatures faded away and would have to wait almost two centuries …show more content…
In relation to the body size, the fish-shaped ichthyosaurs had the largest eyes of any animal ever known (Motani, 2000). The largest eye ever measured was 264 mm across. Scientist have calculated the size of the eyes by the measuring the sclerotic ring, the bone that is embedded in their eyes and used to help the eye keep its shape (Motani, 2000). The eyes were extremely useful to the ichthyosaurs allowing them to track and catch prey in the depths of the ocean where there is very little to no light. Scientists have used the sclerotic ring to roughly calculate the minimum f-number of the eye. The lower the f-number the brighter the image. Conclusions have been made that ichthyosaurs had a minimum f-number of 0.9 giving the species extremely good eyesight in the depths of the ocean (Motani, 2000). Put in comparison, a human has an f-number of about 2.1 and some nocturnal animals can be closer to 0.9, the same as the ichthyosaurs. This would have allowed the ichthyosaurs to see at depths of up to 500 meters or more. This adaptation of the animal made it very effective in finding enough food to sustain itself in the open