Fish Lec 4

living vs extinct fish ancestors

where did fish come from?

• urochordata (invertebrate): larve mobile ; adult sessile

• ceophalochordata (invertebrate): no compelx skull, neoteny (has immature features), mobile

• craniata —> vertebrata (vertebrae): has neurocranium and vertebrae

how did the evolution of fish happen

• chordate traits paved the way for fishes

  • gill slits

  • notocord

  • doral, hollow nerve cord

  • muscular, post anal tail

when did fish come to be

early cambrian

features of conodonts

• jawless fish

• cone shape teeth

• v shape muscle patter

• cartilaginous cranial skeleton

• notocord

features of ostracoderm

• jawless fish

• shell skinned (body armor)

• dermal plates (paired fins mostly absent)

• muscular pumping (pump H2O + prey)

• has neural crest (collection of stem cells)

features of placoderms

• jaw fish

• bony plates cover anterior

• heterocercal tail

• paired fins

• gnathal plates (teeth): no replacement, dermal bone worn down

• marine to freshwater

• benthic but can be open water

• has internal fertilization

features of acanthodians

• jaw fish

• “spiny sharks”: median and paired spines

• covered in scales

• salt and freshater

• active swimmers

features of chondrichthyans

• jaw fish

• calcified cartilage skeleton (tile like)

• types

  • cladoselachimorpha: cladodont teeth (cone shape)

  • ctenacanthimorpha: 2 dorsal fins w/ spines

  • xenacanthimorpha: freshwater, pleuracanth teeth

• subclass

  • holocephal: ex. chimeras

  • euselachii:

    • hybodonta: sister to modern day sharks

    • elasmobranchii: modern sharks and rays (ex. megalodon)

features of osterichthyes —> sarcopterygii

• osteichtyes = bony fish

• sarcoptergii = lobe fin fish (paired fins supported by radicals)

  • transitional from fishes to tetrapods

    • fish: gills, scales, fin rays

    • tetrapods: shorten skull, mobile neck, wrist joint

• subclass: actinopterygii

  • actinoptergians: ray fined (pelvic fin supported by soft rays)

  • palaeoniscoids

  • cladista

  • chondrostei

  • neopterygii