Vertebrata (Fish, Sharks, Rays, Amphibians, Reptiles, Mammals, Birds)

Subphylum Vertebrata (Jawless Fishes, Bony Fishes, Sharks and Rays, Amphibians, Reptiles, Mammals, and Birds)

Wikipedia Entry

Approximate Number of Species:  57, 674

Largest: The blue whale,  Balaenoptera musculus, reaches a weight of 209 tons (190,000 kg)

Blue whale : Photo by Gunnsteinlye via Flikr

Smallest:  The fish, Paedocypris progenetica,  reaches lengths of only 0.31 inches (7.9 mm)

Paedocypris photo by M. Kottelat, Raffles Museum of Biodiversity Research, National University of Singapore

References:

Brusca RC & Brusca GJ (2003) Invertebrates (Sinauer Associates, Inc., Publishers, Sunderland, MA) 2nd Ed.

Smith FA, et al. (2003) Body mass of late Quaternary mammals. Ecology 84:3403.

Kottelate M, Britz R, Hui TH, & Witte K-E (2006) Paedocypris, a new genus of Southeast Asian cyprinid fish with a remarkable sexual dimoprhism, comprises the world’s smallest vertebrate. Proceedings of the Royal Society B 273:895-899.