Crocodiles

Crocodilia, the third major group of reptiles, which includes three living families. One of these, the Alligatoridae, has in it the familiar American alligator, its close relative the Chinese alligator and the various tropical American caimans. The second family is the Crocodylidae, the true crocodiles, dwarf crocodiles and the false gavial. The third, the Gavialidae, has a single living representative, the slim-jawed, fish-eating gavial of southern Asia.

Crocodilia are in some respects the most advanced of reptiles. They share with higher vertebrates a four-chambered heart. This makes possible a more efficient circulation than other reptiles have, because in the usual reptilian three-chambered heart there is some mixing of newly oxygenated blood from the lungs with the de-oxygenated blood just in from the tissues of the body. Another advanced feature of crocodilians is a partition between the cavities of the chest and abdomen that suggests the diaphragm of mammals. In crocodilians the cloacal opening is a longitudinal slit as in turtles, instead of being transverse as in lizards and snakes.

Full-grown crocodilians range in size from between three and four feet, in the ease of the Congo dwarf crocodile and the dwarf caiman, to top lengths of about 23 feet in the Orinoco crocodiles. The biggest American alligator ever measured was slightly over 19 feet long. How long crocodilians live is not certain, although they have long been thought of as practically indestructible creatures that live forever. In the rare places in which man does not kill them long before that they probably do reach ages of 50 years or more. They appear to mature at an age of six or seven years.

Crocodilians have one of the few well-developed voices among reptiles. In its timbre and impact on the surroundings, the voice of the American alligator must be considered one of the great animal voices of the world.

Go To Page: 1

Articles in this Topic    Discussions in this Topic