Early Fauna

3+ billion years – life forms
cyanobacteria (blue green algae) – very early
changed atmosphere – generate oxygen

Sudden rise of life
4/5ths of history involved with the  creation of biological chemicals
Proterozooic-Phanerozoic boundary = time when living organisms are clearly present ("visible")
Earlier thought due to appearance & fossilization of “shelled” animals
Actually true – Phanerozoic = visible life (but multicellular life exists before)
Explosion really occurs at this boundary
Diversity rises up to Ordovician
Constant thereafter w/ change & replacement in forms

Vendian fauna – (end of PreCambrian occuring around 550 - 600 million years ago)
Slow accumulation of sediment (more slowly than igneous or sedimentary rocks)
Some radiogeneric elements (U – Pb)
Ediacaran fauna = Vendian fauna or Vendozoans
1^st recognized by Reg Spriggs (1946)- although the earliest discovery was made in Namibia, Africa in 1920's but not recognized. 
saucer shaped fossil
found near Ediacara, Australia
similar to jellyfish
later – Roger Mason (1957)
discovers “fern fronds” fossil
in Leicestershire, England (midlands)
considered algae
later compared to Ediacaran sea pens (stalked hydroids or anemones)

relationships to present
trilobozoans – “three lobes”

like jellyfish (medusae) – but which have 4 lobes
swim or crawl? (ribbon-like tracks found)
graze on algae?
Initially fit to modern forms
Additional discoveries don’t fit (Namibia)
Initial unknown sequence of multicellular forms?

Seilacher’s hypothesis
Close examination shows differences between Ediacaran fauna and modern forms
Not like soft corals (branches of polyps) – flattened lobes w/ connected tissue
Quilted mattresses – immobile (w/ stalks for attachment)
Tough-skinned – unlike worms or jellyfish or any modern design
Considered as novel forms, possibly a natural experiment that failed
Dickinsonia – example
Bilateral
Mobile
Contracts upon death (halo around fossilized form)
Spriggina
Seilacher- holdfast one end- frond for the rest
Glaessner – segmented body (wormlike)
Others – early arthropod (predates trilobites)

Large size is difficult
Most no bigger than 4 inches
Double length & width = 4 times surface area, 8 times volume
Circulation a problem 
(insects limited by diffusion of oxygen) 
(dragonflies long & thin)
blue-green or green algal symbionts
(lying flat on shallow algal covered surface?)
(Newfoundland fossils found at great depth though)
lived at intersections of mud and water (low vs. higher oxygen zones)

Loss of Vendozoans
End of Precambrian 
Not known why
Co-occurring worm traces (not burrowers though)
Worm-like forms may have survived into Cambrian

Tomotian fauna
Early Cambrian – shelly fauna [be able to recognize these forms but not their names]
Archaeocyathids – very abundant

Champagne-glass shape
Roots at bottom
Cup in a cup upper part
Appear similar to sponges or corals

Tubes and horns & pointed hats
May be early mollusks (or brachiopod valves)

Narrow (hatchet shaped bodies- pelecypoda?)
Plough through sediment? – cyanobacteriovores?)

Cylinders 
Halkeriids – northern Greenland fossil (1990)
Armored (sharp angular plates) slug-like
Shelled at both ends
Microdictyon
Flanked with sclerites & “legs” beneath

Two strategies for protection
Scales & Sclerites w/ horns
Fine for protection from carnivorous worms, not good for predators that swallow you whole
So they disappear from record

Burgess Shale – mid Cambrian

Charles Doolitle Walcott – of the Smithsonian Institution
Eastern British Columbia – Rockies in Yoho National Park
Wonderfully preserved – hairs on appendages, last meals
Live in a broad shallow sea on a sunlight seafloor next to an escarpment (cliff) 
Occasional collapses of escarpment bury these animals bury these animals in deep anoxic (withouth oxygen) cold water where decomposition doesn't occur thus  “taking a snapshot” of their life forms
Initially most forms shoehorned into existing phyla
Harry Whittington reexamines – 1970s 
Geological Survey of Canada
Trilobite expert
Marella unique arthropod – ¾ inch long

1^st thought to be trilobite form
spiked (defense against worms)
without eyes
legs below 
feathery gills above
scuttled and fed on algae

Opabinia

Nozzle trunk at front w/ spiny jaws (feeds mouth behind)
5 eyes
paddle gills underneath
hard to classify – between annelid and arthropod
Hallucigenia– 1 & ¼ inches long

First described as walking on stilts, w/ dorsal tentacles moving food forward to head
Then turned over when it was realized that they walk on flexible legs with the stilts as defensive spines

Fleshy barbed legs
Mouth with pair of tentacles
Often found w/ sponge remains (crawled around and ate them?)
Hallucigenia and Aysheaia similar to onycophorans (velvet worms)
Alalcomenis – shrimp like arthropod
Large head w/ 2 eyes on stalks
Tapering segments end in paddle
Pair legs with downward pointed spines
Scavengers on dead and dying
Leanchoilia – arthropod
Triangular head with upward prong
Short body
Spiky tail
Short legs w/ paddle gills outside
Curious pair of anterior great appendages
With antennae and three sharp claws
Good swimmer?
Anomalocaris = odd shrimp – largest (2 foot) & fiercest? of Cambrian fauna

Odd parts
Anomalicaris so called  “tail” found in 1880s is actually a feeding appendage
“sponge-like" species named Laggania is actually the body of Anomalocaris
“medusae-like” species named Peytonia is actually the mouth  of Anomalocaris
soft & segmented – glided through water
cruising predator
Sanctacaris – slightly earlier than Burgess shale (but nearby)

Broad flat head
Prominent eyes
Large clawed feeding arms
Active swimmer? – predator?
Predates – Chelicerates (Eurypterids & horseshoe crabs)
Wiwaxia – puzzle
Naked sole (creeper)
Domed upper surface w/ scales and 2 rows of spines
Curved jaws near front