Live Vertebrates

The majority of the extant vertebrates are the jawed vertebrates, or gnathostomes, but lampreys are jawless vertebrates. However, in Late Silurian or Early Devonian times, about 420 to 400 million years ago, the situation was reverse, and the majority of the vertebrate species were jawless fishes (the "ostracoderms", presumably more closely related to the gnathostomes than to lampreys). The decline of the jawless vertebrates and the subsequent rise of the gnathostomes took place about 380 million years ago.

Although not the most numerous group of animals in either number of individuals or in number of taxa, the vertebrates are an endlessly fascinating group of animals. Vertebrates are interesting partly because we are intimately familiar with them, but also because we ARE them. Our species, Homo sapiens, is included within the Vertebrata.

• Birds - Birds are bipedal, warm-blooded, oviparous vertebrate animals characterized primarily by feathers, forelimbs modified as wings, and hollow bones.
  
  
• Amphibians - Amphibians (class Amphibia) are a taxon of animals that include all tetrapods, four-legged vertebrates, that do not have amniotic eggs.
  
  
• Fish - A fish is a water-dwelling vertebrate with gills. Most are cold-blooded. There are over 29,000 species of fish, making them the most diverse group of vertebrates.
  
  
• Reptiles - Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane. Today they are represented by four surviving orders:

1. Crocodilia (crocodiles, caimans and alligators): 23 species
2. Rhynchocephalia (tuataras from New Zealand): 2 species
3. Squamata (lizards, snakes and amphisbaenids): 7,600 species
4. Testudines (turtles): approximately 300 species