Fish
The Earliest Vertebrate Animals
A. Urochordates (tunicates)
B. Cephalochordates (amphioxus)
C. Craniata (fishes)
Fish & Primitive Aquatic
Vertebrates’ preservation
• Sharks – teeth & skin denticles
• Teleosts (bony fish) – bone,
otoliths & scales
• Conodonts – tooth elements
Urochordate larva
free swimming with a
notochord, but as an adult
it morphs into a sessile
sponge like form.
Cephalochordate
Amphioxus has a notochord with V-shaped
body muscles, a primitive brain at the
anterior end and is free swimming
Jawless fish (agnathids)
develop from the
Ordovician through the
Devonian in three
groups:
Heterostracansheadshields with eyes
on sides
Osteostracansheadshields with eyes
atop and lateral fins
Furcacaudiformes(forktails) GOKWTA
The Ostracoderm Astrapis from the
Ordovician of Colorado.
Jawless, lacked an internal bony skeleton
and sported bony armor and a heavy
headshield, eyes on side.
The jawless Heterostracan Anglaspis
heavily armored, lacked jaws with a crude
ventral mouth, eyes on side of skull
Silurian and Devonian
The Devonian Heterostracan
Pteraspis
with typical heavily plated headshield but
flexible trunk and tail, lateral eyes.
The configuration of gills in early jawless fish was
simplicity itself with water taken in at the mouth
and passing out through several gill slits shown in
black. Between each gill slit was a thin strip of
bone, the gill arch (in white) that supported the gill.
…….To adapt a simple jaw required only the
development of a crude hinge on the first gill arch.
Reconstruction of the gill structure of the
Heterostracan Amphiaspid closely
resembles an automobile manifold structure
Gill structure and
function on most living
fish are remarkably
similar regardless of
the taxonomy with
plates mounted on a
rigid axis and two
pumps; one for blood
and one for water
(In a similar fashion a water
cooled engine requires a water
pump and a fan)
The Osteostracan cephalaspid
Hemicyclaspis had the typical armored
headshield of a jawless fish but featured
paired fins, a flexible tail for propulsion and
eyes atop skull
(Late Silurian to Devonian)
Unlike the Heterostracans the
Osteostracans as Hemicyclaspis shown
here had small eyes set very close together
atop their heads.
Only discovered in 1998 the early Devonian
Furcacudiformes or “forktails” don’t conform
to the other jawless fish (heterostracans &
osteostracans) and seem to be an entriely
new group of agnathids
Fish with jaws (the Gnathostomes)
DEVONIAN FISH
Fish first appear in the
Ordovician period but
the number and variety
of fish explodes in the
Devonian so the name
“age of fish” is highly
apropos for this period
The Upper Devonian primitive gnathostome placoderm
arthrodire Dunkleosteus featured a massive 6 foot long
headshield with scissor-like jaws mounted on a 20 foot
long body
The second group of placoderms, the Antiarchs
are characterized by the genus Pterichthys shown
here with a well armored body and small mouth
sited below the eyes. Restricted to the Devonian
period they were probably sediment feeders like
an earthworm or snails.
The anterior-ventral pectoral appendages of the
antiarch Pterichthys tell us they groveled about the
bottom only rarely rising off the sediment water
interface
Sharks (Chondrichthyes)
• Legendary resistance of phosphate parts
to dissolution
• CaPO4 Apatite composition
• Tooth classification (natural)
• Denticle classification (classically artificial)
• Mainly used in marine geology for deposits
well below CCD
• Sharks remarkable for slow evolution and
subsequent looooong stratigraphic ranges
The Actinopterygiians
or ray-finned bony
fish (Osteichthyes)
include the zillions of
species of extant
bony fish the Teleosts
that underwent a
phenomenal
evolutionary
explosion beginning
in the Jurassic
The Devonian lungfish Dipterus is
remarkably similar to modern
coelacanths found in very deep water
off South Africa and Indonesia today.
A living fossil! The coelacanth Latameria is a lobe finned
fish with close relatives dating back to the Devonian
period over 400 million years ago
As soon as the first specimen of the
coelacanth Latimeria was brought to the
surface the demand from museums and
ichthyologists world wide quickly threatened
their dwindling stocks. The animal was very
nearly studied to death!
Anterior ventral, posterior ventral and
posterior ventral fins lobe fins of the extant
Sarcopterygian coelacanth Latimeria all
display a well developed (robust) internal
bony skeleton in stark contrast to the ray
finned fish (Actinoperygians)
Bony Fish (Teleostei)
• Extremely “successful” group, regardless if you measure
success by diversity, biomass or adaptive radiation
• Bone, otoliths, scales, teeth
• Bone of little use unless skeleton is articulated
• Otoliths – used to assess age of populations by annular
growth rings
• Scales – extremely useful in subdividing deeper portions
of Los Angeles Basin
(Lore Rose David)
Teleost –
(bony) fish
Angel Fish
Pliocene,
Po Valley, Italy
~3 m.y.a.
Predator
Feeding
Strategies
Conodonts
• Candidate affinities
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Snail radula
Scolecodonts
Cephalopod molluscs
Fish teeth
Gill supports
Conodonts
• Biostratigrapy Cambrian – Triassic
• Thermal maturation (Harris, Epstein & Harris 1977)
• CaPO4 composition – bilateral symmetry
“facies free” = nektonic primitive fish
• Classically parataxial fossils
• Discovery papers on biological affinity by:
– Scott 1969
– Briggs, Clarkson & Aldridge 1983
Conodont Morphology
 Simple cones – Compound cones
 Blade/bar
 Platform
TRENDS
Cambrian – simple cones
Ordovician – compound cones, blades/bars
Silurian – platforms appear
Devonian – modified platforms (plates) appear
Miss/Penn – expansion of escutcheon on oral side
Permian/Triassic – mostly blades & cusps, fewer
platform types
Thermal Maturation Conodonts
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(also utilized with palynomorphs)
Pigment change due to enclosed organics
Experimental work by Harris et. al.
Munsell soil color chart–
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Pale yellow 50 ° - 80° C
Very pale brown 50 ° - 90 ° C
Brown to dark brown 60 ° - 140 ° C
Very dark greyish brown-dark reddish brown-black 110 ° - 200 °C
Black 190 ° - 300 ° C
Black +300 ° C
Clear to crystal clear >300 ° C
The End