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