Fossil Records

Question 0

What are the two types of fossils?

Answer 0

Body fossils - the remains of once living organisms (e.g. shells, bones)
Trace fossils - signs that organisms were present (e.g. footprints/tracks, burrows)

Question 1

What is a fossil?

Answer 1

The naturally preserved remains of organisms that lived in the past or their traces.

Question 2

What is Taphonomy?

Answer 2

The study of how dead organisms are incorporated into the fossil record.

Question 3

What is fossilisation without alteration?

Answer 3

Freezing, mummification, unaltered shell remains, tree sap (amber).

Question 4

What’s fossilisation with alteration?

Answer 4

Permineralization: mineral laden waters that go into empty parts of bones.
Petrification: hard tissues replaced by stone e.g. silica.
Replacement: hard and soft tissues replaced.

Question 5

What is the best way to become a fossil?

Answer 5

Become buried in sediment as quickly as possible after death.

Question 6

At what point in time did life evolve?

Answer 6

Proterozoic Eon, Neoproterozoic Era, Ediacaran Period.

Eons–Eras–Periods–Epoch(–Age)

Question 7

What is the geological time scale for the origin of life?

Answer 7

Best guess for emergence of life: Archean Era, Eoarchaen Eon (3.8Bya)
Beginning of Phanerozoic Era: (~600Mya).

Question 8

What is one of the primary means of identifying eras, periods, epochs and ages?

Answer 8

Index fossils (primarily marine invertebrates).

Question 9

What makes a good index fossil?

Answer 9

They must be distinctive (easy to ID)
They must be geographically widespread
They must be abundant
They must only be found within a limited geological time.
E.g. trilobites are used to define the paleozoic era.

Question 10

How many metazoan phyla are there?

Answer 10

35 - 34 of which are entirely invertebrates.

Question 11

Where did phyla originate?

Answer 11

Primarily in benthic marine habitats. The first appearance in the fossil record is at ~600Mya, but probably existed earlier.
Representatives of nearly all phyla present by 500Mya during Cambrian Epoch.

Question 12

What are the Ediacaran fauna?

Answer 12

The first unambiguous evidence of complex multicellular organisms - worldwide distribution. ~600-540Mya.
Debatable evidence of some modern phyla (not sure if even animals)
Soft bodied and primarily sessile.
+No preserved hard parts, mostly impressions on shallow depth sandstone beds.
Largely vanish from fossil record by early Cambrian (~540Mya)

Question 13

What was the Cambrian Explosion?

Answer 13

Cambrian period (~540-485Mya).
+Most modern phyla well established in the Cambrian.
+First appearance of animal ‘skeletons’ (shells, chiton)
+Period noted for rapid diversification & first appearance of phyla.
+By end of Cambrian, all major phyla had appeared (apart from Bryozoa).

Question 14

What are trilobites?

Answer 14

“3 lobes” primarily benthic & filter feeder organisms. ~300Mya fossil record, bookend Paleozoic. 10 orders, 5k genera, 20k species.
Found on every continent. Range in size: 1-70cm.
Fossils tend to be shed exoskeleton.
Primarily epifaunal marine benthic. Used as jewellery by humans for 50k years.
FIRST EVIDENCE OF COMPLEX EYES.
Cambrian - Permian.

Question 15

What were trilobite eyes made from?

Answer 15

Calcite, with eye shades suggesting diurnal lifestyle. Even earliest trilobites had eyes - appearance of improving eyesight could have led to Cambrian Explosion.

Question 16

How many specimens had eyes in the Cambrian fossil record?

Answer 16

36% of species, of which 87% were hunters/scavengers.

Question 17

What are Archaeocyathids?

Answer 17

“Ancient cups.” Cambrian record only.
First reef building animals - after extinction no reefs until Ordovician.
Probably Porifera but debatable.
Short lived (15Mya) but highly diverse (100 spp)
Index fossils for lower Cambrian.
Hosted a high diversity of marine inverts.

Question 18

What is the Ordovician period?

Answer 18

Period between ~485-445Mya. Bookended by mass extinction events.
Coral fossils appear but few reefs.
Cephalopods diversify, along with new types of snails, clams and brachiopods.
Oldest complete vertebrate fossils (ostracoderm fish)
First appearance of bryozoans.
Probably origin of Crinoids (Class of Echinoderms, sea lilies)
Life on land appears. End of Ordovician marked by massive global cooling & sea level fall, due to movement of Gondwana to south pole.
Estimated 60% of marine inverts went extinct.

Question 19

What is the Silurian period?

Answer 19

~445-420Mya. Sea level starts to rise and water temperatures warm. Coral reefs are common. Reefs made of tabulate and rugose corals, sponges, and crinoids.
Land plants and animals diversify. Bony fish make first appearance.

Question 20

What were the coral reefs of Paleozoic like?

Answer 20

Corals appear around ~520Mya. They diversify around 470Mya, but no reefs. Reefs appear 433Mya, in late Devonian there is a mass extinction (359Mya, reefs suffer steep decline. 252Mya, rugosa and tabulate go extince.

Question 21

What was the difference between rugose and tabulate coral symmetry?

Answer 21

Rugose is bilateral, tabulate is radial.

Question 22

What was the Devonian period like?

Answer 22

Silurian and Devonian seas dominated by brachiopods & reefs composed of sponges and rugose and tabulate corals - trilobites on the decline. Often called age of fishes.
Brachiopods over the Phanerozoic: 12k fossil spp, 5k genera.
+Filter feeders, ecologically similar to clams, but in diff phylum.

Question 23

How would you find how many days there were into a Devonian year?

Answer 23

Devonian horn coral shows 380Mya old through radiometric dating.
The duration of a year does not change - 1 devonian year = 1 modern year. Length of day changes, so due to friction created by tides day gets longer over time (~2secs every 100k years)
Back calculatin from 380Mya and predicted that each year contain 396 days at 22 hours.
Corals show through daily increments of growth (CaCO3 absorption falls during night and increases during day) ~400 days in year, 21.9 hours long.

Question 24

What was the late Devonian mass extinction?

Answer 24

80% of spp went extinct (incl. terrestrial spp.) Reefs disappear, no more for 100Mya. Trilobites undergo steep declines.
Possible extinction rates not higher but speciation rates reduced dramatically (why?)
Global cooling - due to ‘greening’ of planet - CO2 removal.

Question 25

What was the Carboniferous period?

Answer 25

Named for extensive coal deposits formed during warm period. Brachiopods dominant, covering sea bed. Reefs not recovered from LDE. Crinoids highly abundant. Gastropods, sharks & bony fish diversify. 419-359Mya.

Question 26

What was the Permian period?

Answer 26

Last period of Paleozoic ear. Continents merge into Pangaea. Biggest of ‘big 5’ extinctions: 95% of marine & terrestrial spp go extinct. Possible cause: volcanic eruption in modern day Russia.
Paleozoic fauna suffer - trilobites gone.
[Corals reappear in triassic (modern scleractinian coral)12-14Mya after mass extinction. Modern Fauna rebound in mesozoic & continue diversification throughout Cenozoic.)

Question 27

What is considered a MASS EXTINCTION?

Answer 27

+Extinctions occur all over the world.
+Large number of species go extinct.
+Many types of spp go extinct.
+The extinctions are clustered in a short amount of geological time.

Question 28

Sepkoski’s evolutionary fauna of the Phanerozoic are divided into which three groups? What are the dominant animals in each?

Answer 28

Cambrian Fauna: Trilobite rich.
Paleozoic fauna: Brachiopod rich.
Modern fauna: Mollusc rich.

Question 29

What was the biggest of the big five mass extinctions during the Phanerozoic?

Answer 29

The Permian mass extinction.