Lec 10 Flashcards
Euteleostomi
“Osteichtyes” + Tetrapods
SYNAPOMORPHIES:
- -Endochondral bone
- -Dermal bone derivatives
- –Fin rays (LOST in tetrapods)
- –Jaws covered by dermal bones (i.e. premaxillae, maxillae, dentaries)
- -Lungs
- –Most species with gas bladders derived from lungs (EXCEPT tetrapods)
“Osteichthyes”
“Bony fishes”
Includes Actinopterygii and Sarcopterygii
Historical PARAPHYLETIC group: Does NOT include tetrapods
Actinopterygii
Includes:
- -Cladistia (bichirs)
- -Chondrostei (sturgeon and paddlefishes)
- Neopterygii
- -Lepisostiformes (gars)
- -Amiiformes (bowfin)
- -Teleostei (LOTS of fishes)
SYNAPOMORPHIES:
- Fin rays supported by parallel rows of bones (RADIALS - endochondral) which then articulate with elements of pectoral/pelvic girdle
- Various characteristics of skull, scales, tail morphology, etc.
- Ray fin/wing:
- -KEY synapomorphy
- Endochondral appendage bones (radials) and associated musculature do not protrude from body
- Ganoid scales
~30,000 species
Operculum covers single opening to gill arches = ANCESTRAL
Cladistia
Bichirs
Ancient sister lineage to all other actinopterygians
Diverged from all other actinopterygians ~400mya
Controversial phylogenetic placement for decades: Sister to Actinopterygii or Sarcopterygii?
–Current view: Actinopterygii
SYNAPOMORPHIES:
- -Lobed PECTORAL fins:
- –Convergence with sarcopterygians
Ancestral Traits:
- -Paired lungs
- –HOMOLOGOUS to tetrapod lungs
Can use gills; MUST breathe air
Ganoid scales = heavy armor
Spiral valve: MAY be ancestral trait
~12 species in tropical Africa
Chondrostei
Used to be PARAPHYLETIC because taxon included bichirs until recently:
- Historical PARAPHYLETIC
- Current MONOPHYLETIC
Includes:
- Sturgeons
- Paddlefishes
Cartilaginous skeleton:
- -Reversal
- -Secondarily derived
- -Likely due to heterochrony (paedomorphosis)
- –Old adults sometimes show slight ossification of some cartilaginous elements
ANCESTRAL:
–HETEROCERCAL caudal fin
~29 species
Chondrostei: Sturgeons
Ventral mouth without teeth and with sensitive barbels for finding food (benthic invertebrates and fish)
Largest FW fish (andromous)
- -Beluga sturgeon (Asia) reach 8.5m and 1300kg
- -White sturgeon (N.A.) reach 4m and 590kg
~27 species
Chondrostei: Paddlefishes
Paddle-like snout - embedded electroreceptors
Filter feeders on zooplankton
2 species:
- Mississippi drainage: up to 2m
- Yangtze River: up to 5m
Neopterygii
SYNAPOMORPHIES:
- -Clavicle lost or greatly reduced
- -Mobile maxilla
- -Various other ostelogical characteristics
Includes:
- -Lepisostiformes (gars)
- -Amiiformes (bowfin)
- -Teleostei
Lepisostiformes
Gars
7 species
Mississippi drainage into Central America and Caribbean islands
Gas bladder also functions as a lung
Ganoid scales (ANCESTRAL)
Alligator gar nearly 3m and 150kg
Amiiformes
Bowfin
1 species: MONOTYPIC order
Sister to teleosts
Easter US and Canada
Gas bladder also functions as lung
Scales: more like TELEOSTS than basal actinopterygians
Gars and bowfins once groups as HOLOSTEI: PARAPHYLETIC
Teleostei
~96% of all fish
–About 1/2 of all vertebrates
SYNAPOMORPHIES:
–Mobile PREMAXILLA
–Cycloid scales: Lighter and more flexible giving greater maneuverability and speed
—Later ctenoid (spiny) scales evolved in some lineages and scales lost in others
–HOMOcercal caudal fin (even on all sides)
–SUCTION FEEDING: Possible due to mobile premaxilla
Found in nearly ALL aquatic habitats
Suction Feeding:
- Expansion of buccal (oral) cavity generates NEGATIVE pressure to draw in food
- Possible due to mobile MAXILLA (ancestral) and PREMAXILLA (synap)
Sarcopterygii
SYNAPOMORPHIES:
- -Fin rays supported by sturdy endochondral skeletal elements and musculature within fins
- -Fins articulate with pectoral/pelvic girdle via a single element
Flesh fin/wing
Lobe-finned fishes + tetrapods
- -Historically did NOT include tetrapods = PARAPHYLETIC
- -CURRENT view - Tetrapods INCLUDED and MONOPHYLETIC
8 extant NON-TETRAPOD species (with DIPHYCERCAL tail)
Includes:
- -Actinistia (coelocanths)
- -Dipnoi (lungfishes)
- -Tetrapoda
Sarcopterygii: Actinistia
Genus Latimeria
–AKA the “coelocanth”
Deep ocean fish discovered off of southern Africa in 1938
2 species (another in Indonesia)
“Living fossil”
- -Exant species or a couple of species that are the only extant representatives of a once much larger group
- —Only a few representative species (1 or 2)
Sarcopterygii: Dipnoi
6 species
Cartilaginous skeleton = REVERSAL
Prominent notochord = REVERSAL
Can survive in OXYGEN-POOR water due to LUNGS
African and South American species can survive dry periods with “cocoon” of slime and mud
- -Estivation
- -Especially dominant in African species
