![]() ![]() Fishes are active feeders, rather than sessile, suspension feeders. The jawed fishes evolved later and are extraordinarily diverse today. Jawless fishes-the present day hagfishes and lampreys-have a distinct cranium and complex sense organs including eyes, distinguishing them from the invertebrate chordates. Fishes were the earliest vertebrates, and jawless fishes were the earliest of these. Modern fishes include an estimated 31,000 species. (credit a: modification of work by Dave Pape credit b: modification of work by Brian Gratwicke credit c: modification of work by “cuatrok77″/Flickr) Fishes Figure 15.36: Examples of critically endangered vertebrate species include (a) the Siberian tiger (Panthera tigris altaica), (b) the Panamanian golden frog (Atelopus zeteki), and (c) the Philippine eagle (Pithecophaga jefferyi). A great deal is known about the anatomy of the dinosaurs, given the preservation of their skeletal elements in the fossil record. ![]() They were the dominant terrestrial animals for 150 million years, until they died out near the end of the Cretaceous period in a mass extinction. The best-known extinct vertebrates are the dinosaurs, a unique group of reptiles, reaching sizes not seen before or since in terrestrial animals. The vertebrate species now living represent only a small portion of the vertebrates that have existed. ![]() More than 62,000 vertebrate species have been identified. Vertebrates are among the most recognizable organisms of the animal kingdom ( Figure 15.36).
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