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
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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