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C O U R S E 
Paleontology: Early Vertebrate Evolution
Alison Murray, University of Alberta
C O U R S E   L E C T U R E 
Diversity of Early Vertebrate Life
Notes taken on July 23, 2019 by Edward Tanguay
as paleontologists look back into the past, the further they look, the blurrier and smaller the view finder becomes
with living animals we can observe them directly
with animals from the Paleozoic Era (542-250 Ma, fish) or Mesozoic Era (250-65 Ma, dinosaurs) we observe them through fossils
becoming a fossil was like striking the lottery
as some soft Paleozoic life form, the chances of your remains being preserved was exceptionally small
and after a fossil was formed, it had to beat the odds again and again throughout the eons to survive until it was eventually be uncovered and studied
there is about a half billion years between the first appearance of vertebrates in the fossil record and today
during this time, sediments and their fossils were regularly destroyed
localities of exceptional preservation are all the more valuable for what they can tell us
we call these areas of exceptional preservation Lagerstätten
a German word that means storage place
it's only through specific Lagerstätten that we know anything about the earliest animals and vertebrates
because these were animals that were all soft-bodied
such localities are snapshots which afford us a brief glance of life at specific times of our Earth's history
the first evidence of life that we have in the fossil record is that of microbes
640 million years ago
bacteria and other single-celled organisms dominated the earth from around 3.8 billion years ago to 640 million years ago
life was mostly made up of microbial mass
on a twelve hour clock of evolutionary scale, higher animals don't show up until about 10:00, only two hours of evolution
before that it was only microbes
Ediacaran Period (635-542 Ma)
first multicellular life
first appearance worldwide of somewhat complicated trace fossils
Cambrian Period (542-485 Ma)
rapid diversification of lifeforms known as the Cambrian explosion
high proportion of Lagerstätte sedimentary deposits with exceptional preservation
Burgess Shale biota (508 Ma, middle of Cambrian Period)
soft-bodied organisms
first appears over 600 million years ago
first organisms to produce shells
modern animals
have anterior and posterior end
dorsal and ventral
bilateral animals like fish have heads, while radial animals like sea urchin don't
bilateral animals move forward or backward
radial animals more in any direction
therefore for bilateral animals, sensory organs become concentrated at the anterior end
most animals are bilaterally symmetrical
exception are echinoderms, e.g. starfish
some early fossiles are bilateral and are probably our ancestors
Cambrian Explosion
complex and multicellular life began to diversify in the Pre-Cambrian supereon
increased heavily in the Cambrian period (after 542 Ma)
increase in level of oxygen in oceans and atmosphere
rising sea levels
shallow water environment
animals evolved hard parts
enabled them to have protect themselves and rise up to the surface
Burgess Shale
shales deposited more than 500 million years ago
cliffs of the reefs protected it when the Rocky Mountains formed
animals lived in still water
flattened impressions of the animals
black color films made of iron-rich minerals
traced the outline of the soft tissues
closest relative of living vertebrates
two large eyes
vertebrae-like structures in the back
a large brain in front to process information from the eyes
segmented muscle bundles
could weave their way through the water