ESS 345 Ichthyology

ESS 345 Ichthyology Evolutionary history of fishes 12 Feb 2019 (Who’s birthday?) Quote of the Day: We must, however, acknowledge, as it seems to me, that man with all his noble qualities... still bears in his bodily frame the indelible stamp of his lowly origin._______, (1809-1882) Evolution/radiation of fishes over time Era Cenozoic Fig 13.1 Fishes are the most primitive vertebrate and last common ancestor to all vertebrates They start the branch from all other living things with vertebrae and a cranium Chordata Notochord Dorsal hollow nerve cord Pharyngeal gill slits Postanal tail Urochordata Cephalochordata Craniates (mostly Vertebrata) Phylum Chordata sister is… Echinodermata Synapomorphy – They are deuterostomes Fish Evolutionary Tree – evolutionary innovations in vertebrate history Sarcopterygii Chondrichthyes Actinopterygii (fish) For extant fishes Osteichthyes Gnathostomata Handout Vertebrata Craniata Figure only from Berkeley.edu Hypothesis of fish (vert) origins Background 570 MYA – first large radiation of multicellular life – Fossils of the Burgess Shale – Called the Cambrian explosion Garstang Hypothesis 1928 Neoteny of sessile invertebrates Mistake that was “good” Mudpuppy First Vertebrates Vertebrates appear shortly after Cambrian explosion, 530 MYA – Conodonts Notochord replaced by segmented or partially segmented vertebrate and brain is enclosed in cranium Phylogenetic tree Echinoderms, et al. Other “inverts” Vertebrate phyla X Protostomes Deuterostomes Nephrozoa – bilateral animals First fishes were jawless appearing in late Cambrian to Ordovician No fossils exist for extant jawless fishes (soft bodied) Ostracoderms “Shell skinned”, appear 450-460 MYA First major vert radiation (extinct 350 MYA) – No jaw, no paired fins, heavy bony armor – Marine and freshwater, small (<15 cm) – Sympatric with jawed fishes – 2 classes Pteraspidomorphs Cephalaspidomporhs Placodermi “Plate skinned”, 380 MYA they are abundant Bony plates, got big Jaws, paired appendages, depressiform Die out 350 – 325 MYA, probably sister group Acanthodii Acanthodii 440 MYA thru Permian Appear before Placoderms and last longer, but less diverse/abundant First jawed fishes (allows great specialization); how jaws originated… Acanthodii Many paired fins Fin fold theory 3 pairs otoliths, bony opercula, branchiostegal rays Early groups of fish – Modern Representatives Chondrychthyes Petromyzoniformes Osteichthyes Myxiniformes Gnathostomata Chondrichthyes Poor fossil record, appear 415 MYA in marine deposits (Devonian) Cartilaginous skeleton Teeth not fused to jaw Unsegmented epidermal fin rays Oil filled liver Spiral valve intestine Claspers Chondrichthyes (2 main lines) Elasmobranchii (sharks, rays, most diverse) – Batoidea (rays/skates) – deviates from many body plan (dorsoventrally flattened) – Selachii (sharks) – 5-7 gill openings, no swim bladder, largely predators Holocephali (chimaeras) Early groups of fish – Modern Representatives Elasmobranchs Osteichthyes Holocephali Petromyzoniformes Chondrychthyes Myxiniformes Gnathostomata Osteichthyes Lungs, bone, dermal bony scales, lepidotrichia (dermal) Physostomous Physoclistous FW mostly, stagnate tropical waters Subclass Sarcopterygii Lobed fin fishes Lungfishes – Lungs, cartilaginous skeleton, spiral valve intestine – Internal nostrils connect to pharyngeal region – S. America, Africa, and Australia Coelacanth – External nostrils, large swim bladder Osteolepimorpha Early groups of fish – Modern Representatives Osteolepimorpha Lungfish Coelacanth Actinopterygii Sarcopterygii Osteichthyes Subclass Actinoptergyii Diverse and hard to generalize Devonian but minor until Carboniferous period 350 MYA when large tropical environments abounded and land masses were close to the equator Most dominant type of fish since Early groups of fish – Modern Representatives Osteolepimorpha Lungfish Coelacanth Actinopterygii Sarcopterygii Osteichthyes Subclass Actinoptergyii Scales become less complex, and bony – Ganoid scales Branchiostegal rays Swim bladder - hydrostatic organ Homocercal tail Fin rays become more spiny Fin placement: P1, P2 Early groups of fish – Modern Representatives Gars Bowfins Teleostei Osteolepimorpha Chondrostei Neopterygii Lungfish Coelacanth Actinopterygii Sarcopterygii Osteichthyes Multicellular – 3 tissue layers.

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