Transcript G1PalaeozoicFauna

The Palaeozoic fauna
1. Sepkoski’s Curves
2. The Palaeozoic fauna
3. Brachiopods
4. Corals
5. Graptolites
6. Predators
7. Ecological overview
1. Sepkoski’s Curves
Family diversity
Palaeozoic diversity plateau
Palaeozoic fauna
Ordovician radiation
End Permian extinction
2. Palaeozoic fauna
Lie-in-wait
predators
Corals and other
barrier builders
Brachiopods and
other filter feeders
Graptolites and other plankton
3. Brachiopods
Shell composition
Hinge mechanism
Pedicle
Digestive tract
Phylum Brachiopoda
Subphylum
Subphylum
Linguliformea
Craniiformea
L.Cam.-Rec.
L.Cam. – Rec.
Organophosphate
Calcareous
Lacking teeth and
Lacking teeth and
sockets
sockets
Present
Reduced or absent
Gut with anus
Gut with anus
Pedicle - used to attach the
animal to the sea floor
A.
Diductor muscle –
muscles which contract
to open the shell
Posterior
Subphylum
Rhynchonelliformea
L.Cam-Rec.
Calcareous
Teeth and sockets
present
Present
Gut without anus
Lophophore – food gathering
and respiratory mechanism.
Two arms (brachia) fringed
with cilia generate currents that
bring in food and oxygen
Anterior
Dorsal
Adductor muscle –
muscles which contract
to close the valves
Stomach
Ventral
Mouth
Teeth
B.
Muscle scars – can
be used to identify
certain species
Mantle – sheets of
tissue which line the
shell
Cardinal process –
diductor muscle
attachment site
Dorsal valve
Ventral valve
Brachidium –
lophophore support
4. Corals
Medusoid stage
Sexual
reproduction
Swimming larva
Corals are cnidarians
like jellyfish and sea
anemones
Asexual
reproduction
Polyp stage
Outer cell layer, with stinging
cells on tentacles
Inner cell
wall,
responsible
for digestion
Calcareous
skeleton
Basic coral
morphology
Coral diversity through time
5. Graptolites
Carboniferous
Benthic
diversity
Planktonic diversity
Faunal description
Dendroid graptolites become extinct.
Devonian
Pterobranch
Monograptid fauna Devonian
A., B., simple ‘Monograptus’
Silurian
Morphologically simple monograptids undergo a
series of minor radiations and extinctions.
Monograptid fauna - Upper
Silurian
C. Retiolites
D. Saetograptus
Saetograptids, robust monograptids, often with
spines on their early thecae, radiate. Retiolitids,
unusual graptoloids with a skeletal framework
around the rhabdosome, become common.
Monograptids radiate into a variety of forms with curved or spiral stipes
and complicated thecae. Thecae become isolated, asymmetrical, hooked,
spinose. Cyrtograptids evolve; monograptids that produce branches from
spines on their thecae and have a spiral form.
Monograptid fauna - Lower
Silurian
F. Normalograptus
G. Spirograptus
H. ‘Monograptus’
E. Cyrtograptus
Cambrian
Ordovician
Only one genus of diplograptids survives the end-Ordovician extinction event. This
group evolves into monograptids, which have a single stipe.
Fauna dominated by graptoloids with two thecae
arranged back-to back. These diplograptid
species showed more variety of thecal shape than
had been seen before, with boxy thecae and
curved thecal walls becoming common. V- and
Y- shaped graptoloids evolve.
Diplograptid fauna
I.’Climacograptus’
J. Dicellograptus
K. Dicranograptus
Maximum diversity of graptolites,
around 200 species worldwide.
High degree of faunal provinciality with
two major provinces, a low latitude Pacific
province and a higher, southern hemisphere
Atlantic province. Four and two stiped
graptoloids common.
Dendroid graptolites move from the
benthos into the plankton. Different thecal
types are lost. Number of stipes reduces,
but degree of regularity of the rhabdosome
increases rapidly. True graptoloids,
dominated by forms with a virgella, quickly
appear.
Benthic graptolites evolve from a common ancestor
of graptolites and pterobranchs. Maximum
diversity of benthic forms in the late Cambrian and
early Ordovician.
Planktonic
graptoloid
Dichograptid fauna
L. Didymograptus
M. ‘Isograptus’
N. Phyllograptus
Anisograptid fauna
O. Clonograptus
P. Staurograptus
First planktonic
graptolites are dendroids
Q. Rhaphidonema
Benthic
dendroid
6. Predators
Trilobites
Nautiloids
Conodonts
7. Ecological overview
1. Palaeozoic fauna takes over slowly
2. Fauna reaches higher diversity than
before
3. Includes mud grubbers like trilobites
from Cambrian fauna
4. Includes filter feeders and
macrozooplankton
5. Increased niche space above seafloor
6. Includes greater predator pressure
7. Survives mass extinctions at end
Ordovician and end Devonian
8. Wiped out at end Permian