Systematics of major fish groups IV

Three classes of bony fish

  1. Origin of the bony fishes
    1. Teleostomi
    2. Three classes; synapomorphies include
      1. 3 semicirc canals and otoliths
      2. neural and hemal arches
      3. ossified operculum
      4. branchiostegal rays
  2. Class Acanthodii (fig. 11.6, also inside front cover. Note mistake in illustration alignment)
    1. Evolutionary history
      1. Earliest fossil jawed fishes
      2. appeared in upper Silurian
      3. very diverse in Devonian,
      4. remained until Permian
    2. Synapomorphies
      1. stout spines assoc. with paired and medial fins
    3. Where?
      1. mostly marine
      2. streamlined body, reduced armor, fin placement: more pelagic
  3. 'Osteichthyes'
    1. This is group usually referred to as bony fishes
    2. Important synapomorphies
        1. fins supported by dermal bone rays, lepidotrichia
        2. gas bladder/lung (originally, ventral outpocket of esophagus)
    3. Unranked because paraphyletic
  4. Class Sarcopterygii
    1. Evolutionary history
      1. Originated in Devonian (400 mya)
      2. Highest diversity of aquatic forms in late Paleo, and Mesozoic
    2. Synapomorphies
      1. Lobed fins, bony leg-like supports (fig. 11.10)
      2. cosmine in bones and scales
  5. Subclass Coelacanthimorpha (hollow spine)
    1. Evolutionary history
      1. first fossils in mid-Devonian
      2. not known after Cretaceous
      3. except the living Latimeria chalumnae, discovered in 1938 (box 13.2)
    2. synapomorphies
      1. bony case to vert spines and fin rays
      2. 3 lobed tail
      3. intracranial joint, between frontals and parietal; anterior part can be pulled ventrally in biting.
  6. Subclass Dipnoi, lungfishes (fig. 11.8)
    1. History
      1. evolved in lower Devonian, marine waters
      2. diversification in freshwaters
    2. synapomorphies
      1. solid braincase, unlike coelacanths
      2. Functional lungs,
      3. no premax or maxilla
      4. tooth plates
    3. when living lungfishes first found, thought to be reptiles, amphibians, even though fossil lungfishes known and viewed as fish
    4. two orders: (fig. 13.8; don't need names)
      1. one is Australian
        1. facultative airbreather, lung hydrostatic, doesn’t tolerate dessication
      2. other is African and S. American
        1. obligate airbreathers
        2. African estivates
      3. evolutionary relationships parallel order of break from Gondwanaland (draw)
  7. SubC Osteolepimorphi ('bone scales'; fig. 11.9)
    1. History
      1. originated at same time as dipnoans
      2. considered closest relative, sister group, to tetrapods (subC tetrapoda)
  8. Class Actinopterygii (ray-finned fishes)
    1. Evolutionary history
      1. Complete remains in mid- and late Devonian
      2. Radiation in late Paleozoic, as ostracoderms, placoderms, acanthodii diminish
    2. Synapomorphies
      1. fins with lepidotrichia, which originate from scales
      2. fins moved via body musculature, supported by internal girdles (contrasted by lobes of paired fins in sarcops)
      3. 2-lobed heterocercal tail
      4. no cosmine
      5. scales covered in ganoin
    3. Evolutionary progression in group (fig. 11.11)
      1. Theme is greater degree of adaptation to complex environments
      2. jaws
        1. shorter mouth
        2. many changes related to greater expandability and protrusibility
      3. scales
        1. elimination of layers, including ganoin
        2. lighter, more flexible
      4. fins
        1. more flexible, mobile
        2. development of homocercal tail
      5. swim bladder
        1. greater elaboration as buoyancy regulator
        2. frees fins for maneuvers
    4. Subclass Chondrostei: cartilaginous bony fishes (fig. 11.13)
      1. As drawn, paraphyletic
      2. Order Polypteriformes: Bichirs
        1. Systematics v. unclear (note discrepancy between cladogram on inside cover and fig. 11.13)
          1. bizarre fins
            1. dorsal fin made up of finlets
            2. lobed pectoral but different from all others
          2. some features like lungfish
            1. Larvae have external gills
            2. adults have lungs with ventral connnection
        2. African freshwater
      3. Order Acipenseriformes: Sturgeons and paddlefish
        1. difficult to identify synapomorphies; extant forms different from original members
          1. e.g. cartilaginous skeleton, but originally bony
        2. heterocercal tail; spiral valve; ganoid scales
        3. Some extinct groups in this order known from Triassic
        4. sturgeon: (slide)

          5. largest fw fish,

          make caviar,

          CT endangered species, Acipenser brevirostrum, only 800 indivs. in state

        5. paddlefish: 2 species, filter feeders. Miss River and Yangtze, China (slide)

 

Slides

C Actinopterygii, SubC Chondrostei, O Acipenseriformes, Fam. Acipenseridae: Acipenser medirostris, green sturgeon

C Actinopterygii, SubC Chondrostei, O Acipenseriformes, Fam. Polyodontidae: Polyodon spathula, paddlefish