Fishes, Biodiversity of 463 The Bowfin The Bowfin, Amia calva, is the only living member of its genus, family, and order The Bowfin has the abbreviate heterocercal tail and spiral valve intestine of the gars but also has teleost-like biconcave vertebrae as well as cycloid scales, a relatively light scale type also possessed by many teleosts The Bowfin’s head is exceptionally bony and the throat is covered by a distinctive large bone, the gular plate Bowfin swim slowly forwards or backwards by passing undulations back and forth along their long dorsal fin Bowfin occur throughout much of eastern North America in backwater, often swampy areas; they also have a highly vascularized gas bladder which functions as a lung They are relatively large and robust (to m and kg) and predatory on anything that moves Bowfin males guard the young vigorously until they are relatively large (10 cm) Teleosts The division Teleostei (‘‘perfect bone’’) contains most living fishes Teleosts are not only taxonomically diverse but also ecologically diverse, occupying every aquatic habitat type and niche imaginable The 27,000 living teleostean species are placed in 4278 genera, 448 families, and 40 orders This incredible diversity is generally organized into four taxonomic subdivisions that reflect patterns of evolution that date back to the Mesozoic These four main subdivisions are the osteoglossomorphs (bonytongues), elopomorphs (eels and tarpon), otocephalans (herrings and minnow relatives), and the euteleosts, with the latter group containing the vast majority of modern bony fishes Class Actinopterygii Subclass Neopterygii Division Teleostei Subdivision Osteoglossomorpha Order Hiodontiformes: family, species, mooneyes Order Osteoglossiformes: families, 218 species, including bonytongues, African knifefishes, and elephantfishes Osteoglossomorphs derive their name ‘‘bonytongue’’ from the teeth on their tongue that forms part of their bite These freshwater fishes occur on all major continents except Europe The hiodontiforms comprise two species, the Mooneye and Goldeye, both of which occur in major river systems of northern North America The osteoglossiforms are much more diverse The Asian Arowana or Golden Dragonfish, Scleropages formosus, has been depleted in the wild due to overcollecting and is now protected under Appendix I of the Convention on International Trade in Endangered Species (Figure 10) The Arapaima of South America is one of the world’s largest freshwater fishes, reaching a length of 2.5 m The African mormyrid elephantfishes produce and detect weak electric fields, have large cerebellums, and have a brain size: body weight ratio comparable to that of humans Subdivision Elopomorpha Order Elopiformes: families, species, ladyfishes and tarpons Order Albuliformes: families, 30 species, including bonefishes and spiny eels Order Anguilliformes: 15 families, 738 species, including freshwater, moray, cutthroat, and conger eels Order Saccopharyngiformes: families, 28 species, including swallower and gulper eels Figure 10 The Asian Arowana or Golden Dragonfish (Scleropages formosus, Osteoglossidae), an internationally protected species Desirable color varieties have sold for as much as $5000 Photo by Marcel Burkhard, Wikimedia Commons, http://en.wikipedia.org/wiki/ Image:Arowanacele4.jpgfile Elopomorphs all have ribbon-shaped leptocephalus (‘‘pointed head’’) larvae The Atlantic Tarpon is a highly prized gamefish that reaches a length of 2.5 m and a mass of 150 kg Albuliform bonefishes are also popular gamefishes that occupy sandy flats in shallow tropical waters, The 15 families of anguilliform ‘‘true’’ or freshwater eels are distinguished from the approximately 45 other families of ‘‘eel-like’’ fishes that have independently evolved an elongate body Anguillid eels are catadromous, spawning at sea but spending most of their lives in fresh water Muraenid moray eels and their relatives are marine, tropical and warm-temperate, predatory species Synaphobranchid cutthroat eels include an endoparasitic species, the Snubnose Parasitic Eel, which has been found in the heart of a mako shark The saccopharyngiform deepsea gulper and swallower eels have giant mouths but lack many head bones, scales, and fins found in most other fishes Subdivision Otocephala Superorder Clupeomorpha Order Clupeiformes: families, 364 species, including anchovies and herrings Clupeomorphs are small, schooling, silvery, pelagic marine and occasionally freshwater feeders on zooplankton and phytoplankton Herrings, round herrings, shads, alewives, sprats, sardines, pilchards, and menhadens are extremely important commercial species Anchovies range in size from a 2cm Brazilian species to a piscivorous, riverine, 37-cm New Guinea anchovy The largest clupeids are the Indo–Pacific chirocentrid wolf herrings, which reach a length of m and have fang-like jaw teeth Anadromous shads, Alewife, and herrings occasionally establish landlocked populations in rivers, lakes, and reservoirs Superorder Ostariophysi Order Gonorhynchiformes: families, 37 species, including milkfish Order Cypriniformes: families, 3268 species, including minnows, barbs, algae eaters, suckers, and loaches Order Characiformes: 18 families, 1674 species, including freshwater hatchetfishes, tetras, and characins Order Siluriformes: 36 families, 2867 species, including North American freshwater, airbreathing, electric,