TheThe EarlyEarly PaleozoPaleozoicic WorldWorld

LateLate CambrianCambrian andand EarlyEarly OrdovicianOrdovician developmentdevelopment ofof LifeLife andand LandLand

Jarðsaga 1 -Saga Lífs og Lands – Ólafur Ingólfsson RoleRole ofof oxygenoxygen inin CaCambrianmbrian evolutionevolution

Oxygen priorities: Low oxygen levels: respiration & tissue synthesis

High oxygen levels: oxygen can be used for lower priority things - skeletons, shells, etc.

Oxygen reached critical threshold in , eliminating the need for priorities.

Evidence: modern low O2 environments have only small, soft-bodied forms. TheThe LateLate CambriaCambriann GlobeGlobe TheThe LateLate CambrianCambrian ClimateClimate Fossil Assemblages of the Proterozoic - Cambrian boundary Windows into the Past: Chengjiang Lagerstatten Chengjiang Lagerstatten

Sinoburius lunaris

Xandarella spectaculum Squamacula clypeta LateLate CambrianCambrian developdevelopmentment ofof lifelife

Trilobites, brachiopods, and other typical Cambrian groups continued to flourish. Molluscs diversified.

During this time grazing increased. Mat scratchers and mat miners migrated upwards towards littoral zone and downwards to deeper water Trace fossils made by show that the animals of the Cambrian were developing new ecological niches and strategies - such as active hunting, burrowing deeply into sediment, and making complex branching burrows. AlmostAlmost everyevery metazoanmetazoan phylumphylum arrivarriveded onon thethe CambrianCambrian scene...scene...

Almost every metazoan phylum with hard parts, and many that lack hard parts, made their first appearance in the Cambrian. The only modern phylum to appear after the Cambrian was the phylum Bryozoa (mosadýr), which is not known before the early . PLANTS ANIMALS flowering plants arthropods chordates conifers annelids cycads mollusks echinoderms ginkgo ferns ribbon FUNGI gnetophytes worms horsetails roundworms flatworms mosses, rotifers club fungi lycophytes liverworts cnidarians whisk ferns , sac fungi hornworts sponges comb jellies

Trichoplax zygomycetes red green brown algae algae algae chytrids ciliated flagellated diatoms protozoans protozoans dinoflagellates chrysophytes euglenoids sporozoans

PROTISTANS water slime amoeboid molds molds protozoans

eubacteria

MONERANS archaebacteria

chemical origin of life The Early Cambrian Radiation

With abundant oxygen, phyla underwent adaptive radiation, but many early phyla did not stand up to competition Metazoan Diversification: Molluscs Metazoan diversification: The Echinoderms (Skrápdýr) TheThe ConodonConodontsts The conodonts first appear duringtheLateCambrian. Thesewereprobablyfast swimming micro-predators, soft-bodied animals, now considered to be among the first vertebrates, with flattened elongate eel-like bodies. They are known almost entirely from their The wide variety in conodont teeth hard (calcium phosphate) suggestthatevenat thisearly tooth-like elements, but a stage in the evolution of life, they few instances of soft tissue were part of a com-plex ecosystem preservation revealed their of predator and prey physical form. Cephalochordates: Primitive, Fish-Like Forms (appear by at least Middle Cambrian)

Amphioxus

conodonts conodont Cartilaginous fishes

Bony Fishes

Primitive Fishes TheThe fishesfishes startstart toto evolve...evolve...

The first fishes, and among the first vertebrates, were the ostracoderms (bryn- fiskar), which appeared in theLateCambrianPeriod, about 510 million years ago, and became extinct at the end of the , about 350 million years ago. The internal skeletons of these jawless creatures are rarely preserved. PoorPoor Ostracoderms had bony external shields swimmswimmersers that covered the head and most of the trunk. From 9-30 cm long, ostracoderms had rather thick, flattened bodies with only a pair of side flaps to help in steering. They probably swam clumsily just above the sea floor. The mouth served to obtain oxygen and to retain bits of food. Early Paleozoic Ostracoderms (Jawless fishes) RecurringRecurring extinctionsextinctions duringduring thethe CambrianCambrian PeriodPeriod The Cambrian extinction first of a number of such events through Earth’s history AA majormajor extinctionextinction byby thethe endend ofof thethe Cambrian.Cambrian. Why?Why?

The very end of the Cambrian saw a mass extinction that killed off a number of unique taxa, including: • the last archaeocyathids • the anomalocarids • many lobopods (worms) •manytrilobites • basal arachnomorphs (fjölfætlur) • several orders of early nautiloids (kuggar) • a number of primitive echinoderms WhatWhat doesdoes itit taketake toto survive...?survive...?

During the Cambrium and most of the Ordovician, sea levels were high. On the continental shelves, marine organisms engage in evolutionary experiments. The number of families of known marine invertebrates increases from about 200 at the end of the Cambrian to around 500 in the early Ordovician.

Pikaina EvolutionaryEvolutionary experimentsexperiments:: StrangeStrange animals...animals... Haplophrentis carinatus

Wiwaxia corrugata

Marrella splendens Hallucigenia sparsa

Opabinia regalis Amiskwia sagittiformis FewFew questionsquestions onon extinctioextinctionsns andand survivalsurvival

• Were victims of early extinctions biologically inferior to the groups that survived? • Were they less effective in competing with other taxa or in avoiding predators? • Can extinctions of whole groups be blamed on predators? • Were they maybe simply the unlucky victims of catastrophic extinctions that struck species regardless of their ecological abilities? • Did groups go extinct because they failed to diversify rapidly? Stephen Jay Gould – Radical Thinker Could some Burgess Shale organisms belong to extinct phyla ? Is it possible that a phylum could be represented by few or single species ?

If so, suggests that the Cambrian Explosion produced more phyla than are present today

extinction

Conventional view: Gould’s View: Gradual increase in number Sudden appearance of phyla, of phyla through time removal of many by mass extinction CauseCause(s)(s) ofof CambrianCambrian extintextintion(s)ion(s) notnot known...known... During the Late Cambrian alone, there were three distinct bio-stratigraphic intervals in trilobite distribution, each marked by a mass- extinction. The cause(s) of the late Cambrian extinction(s) are not known, but it seems almost certain that a change in sea level occurred at this time, changing the habitat to which many of these early animals were adapted, and driving them to extinction. Pherhaps climate change as well...? OrdoviciumOrdovicium PeriodPeriod (495(495--443443 MY)MY) –– aa periodperiod ofof greatgreat diversificationdiversification

• The Ordovician was named by the British geologist Charles Lapworth in 1879. He took the name from an ancient Celtic tribe, the Ordovices, renowned for its resistance to Roman domination. • The boundary between the Cambrian and the Ordovician is marked by the appearance of certain planktic graptolites TheThe OrdovicianOrdovician (495(495--443443 MY)MY)

Particularly good examples of Ordovician sequences are found in: • China, Western Australia, Argentina, the United States and Canada. • Ordovician rocks over much of these areas are typified by considerable thickness of lime and other carbonate rocks that accumulated in shallow subtidal and intertidal environments. • Rocks formed from sediments deposited on the margins of Ordovician shelves are commonly dark, organic-rich mudstones which bear the remains of graptolites and may have thin seams of iron sulfide. • Graptolites are the most common fossils found in the mudstones. MiddleMiddle OrdovicianOrdovician continentalcontinental plateplate configurationconfiguration The Ordovician Period - great radiation of life

Ordovician strata are • Life in sediments characterized by numerous developed – witnessed and diverse trilobites and by increased biotur- conodonts found in sequences bation of sediments. of shale, limestone, dolostone, Mostly bivalves and and sandstone. In addition, trilobites. bryozoans, corals, crinoids, as well as many kinds of •Lifeontheseafloor brachiopods, snails, clams, and developed rapidly – cephalopods appeared for the intense grazing, first time in the geologic scavenging, predation record in tropical Ordovician and reef building. environments. Starfishes arrive. NewNew groupsgroups ofof animanimalsals arrivearrive The Graptolites appear. For a long time no one was sure what kind of animals they were. Most fossil graptolites look like nothing so much as tiny sawblades. Well- preserved graptolites can be seen to be tubular in cross-section. Graptolites are thought to have been planktonic, floating or slowly sinking through the water. The spiral shape of some was probably an adaptation to slow sinking. Other graptolites may have been connected to gas-filled sacs, keeping them buoyant.

Very important stratigraphic markers due to rapid evolution. GRAPTOLITES

In structure they were stick like organisms with an organic skeleton. In shape they could either be straight or curved, or possibly even spiral. Their preservation is quite often poor and usually just a carbonaceous film remain (hence their nam graptho: greek= write, lite: from greek, lithos= rock). KingdomKingdom AnimaliaAnimalia,, PhylumPhylum ProtochordataProtochordata •• GraptolithiniaGraptolithinia –– GraptolitesGraptolites –– plankticplanktic oror benthicbenthic – Appear as “pencil- like” marks on shale CoralsCorals firstfirst appearedappeared inin LowerLower OrdoviciumOrdovicium

Sea anemones (sæfíflar) are closely related to Paleozoic corals, while jellyfish are distant relatives. Coral is a very primitive animal consisting almost exclusively of a large stomach with an opening that serves both as mouth and anus. Corals dwell on the floor of shallow tropical seas. CoralCoral reefsreefs Coral reefs are complex, enduring, magnificent and dynamic living structures of geologic proportion. They are among our planet’s most prolific and intricately interrelated ecosystems. They are also the planet’s oldest natural com- munity. Today’s reefs are simply the most recent link in a lengthy genetic chain. TheThe nautiloidsnautiloids (Álfasmokkar)(Álfasmokkar)

The nautiloids, predecessors of present day squids and octopuses, evolve during the latest Cambrian and early Ordovician. They were highly successful predators SomeSome factsfacts onon cephalopodscephalopods ((hausfætlur,hausfætlur, smokkarsmokkar )) • All are active marine predators, able to swim swiftly, and easily competing with fish in the marine habitat. • There are 650 living species, but more than 7,500 fossil forms are known. • Cephalopods are quite large by molluscan standards (6- 70 cm), with the modern day Architeuthis, the giant squid, with a body length of up to 16 m • the Ordovician nautiloid Cameroceras had a straight shell up to 10 metres in length and and the ammonoid Pachydiscus seppenradensis, with a coiled shell 3 metres in diameter • The cephalopods are the largest invertebrates ever to live, with weights of one to two tons. CephalopodsCephalopods:: aa majormajor stepstep towardstowards moremore intelligentintelligent life...life... • The tremendous evolutionary radiation of nautiloid cephalopods meant an increase in the level of intelligence in Paleozoic oceans. • Cephalopods are the most intelligent of all invertebrates, owing to the development of elaborate manipulative organs (tentacles for touching and grasping). • One researcher described the common octopus as like a sort of aquatic dog or cat. Although Ordovician cephalopods were probably not equal to modern forms in intelligence, they were certainly superior to that of contemporary (non-cephalopod) life-forms. OrdovicianOrdovician seasea floorfloor ReferencesReferences,, webweb resourcesresources etcetc •• StanleyStanley,, EarthEarth SystemSystem HistoryHistory,, chapterchapter 1212 •• Fortey,Fortey, R.R. LifeLife –– AA naturalnatural HHistoryistory ofof thethe ffirstirst fourfour billionbillion yearsyears ofof lifelife onon Earth.Earth. NewNew York,York, VintageVintage Books,Books, 346346 pp.pp. •• ForteyFortey,, R.R. TrilobateTrilobate –– EywitnessEywitness toto EvEvolutionolution.. London,London, Flamingo,Flamingo, 246246 pp.pp. •• httphttp://www.ucmp.berkeley.edu/cambrian/camb.html://www.ucmp.berkeley.edu/cambrian/camb.html •• httphttp://jan.ucc.nau.edu/~rcb7/global_history.html://jan.ucc.nau.edu/~rcb7/global_history.html •• httphttp://www.gps.caltech.edu/~devans/iitpw/science.html://www.gps.caltech.edu/~devans/iitpw/science.html •• httphttp://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm://www.palaeos.com/Paleozoic/Cambrian/Cambrian.htm •• httphttp://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm://www.palaeos.com/Paleozoic/Ordovician/Ordovician.htm •• http://www.peripatus.gen.nz/Books/WonLif.htmlhttp://www.peripatus.gen.nz/Books/WonLif.html •• httphttp://www.toyen.uio.no/palmus/galleri/b://www.toyen.uio.no/palmus/galleri/bladladeer/blad_x03.htmr/blad_x03.htm •• httphttp://www.fossilmuseum.net/Paleobiology/Pale://www.fossilmuseum.net/Paleobiology/Paleoozoic_paleobzoic_paleobiiologolog y.htm#Ordy.htm#Ordoovicianvician •• httphttp://www.ucmp.berkeley.edu/ordovician/ordovician.html://www.ucmp.berkeley.edu/ordovician/ordovician.html