Post on 21-Jun-2020
transcript
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
Craniata
Vertebrata
GnathostomataOsteichthyes
Actinopterygii (fish)Chondrichthyes
Sarcopterygii
Figure only from Berkeley.edu
Handout
For extant fishes
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
X
Other “inverts”Echinoderms, et al.
Vertebrate phyla
DeuterostomesProtostomes
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
Myxiniformes
Chondrychthyes
Osteichthyes
Petromyzoniformes
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
MyxiniformesChondrychthyes
Osteichthyes
Petromyzoniformes
Gnathostomata
HolocephaliElasmobranchs
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
Lungfish
Sarcopterygii
Osteichthyes
Coelacanth
Osteolepimorpha
Actinopterygii
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
Lungfish
Sarcopterygii
Osteichthyes
Coelacanth
Osteolepimorpha
Actinopterygii
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
Lungfish
Sarcopterygii
Osteichthyes
Coelacanth
Osteolepimorpha
Actinopterygii
Chondrostei
Neopterygii
TeleosteiGars Bowfins
Multicellular – 3 tissue layers