Fossils Flashcards
What are corals?
Creatures closely related to a sea anemone, with hollow, bag-like bodies with a mouth at the top surrounded by tentacles
What do coral tentacles do?
catch and paralyse small organisms which are then pushed into the mouth
What is the role of the coral mouth?
Feeding - mostly at night
removing undigested food
What is the polyp?
The soft part of the coral
What is the corallum?
The calcareous skeleton which is built by the polyp, and is where the polyp sits
What are the two types of corals?
Solitary corals
Colonial corals
What is a colonial coral?
lots of polyps all living in a group (colony), all attached to the same corallum
What is a solitary coral?
A single polyp on a cup-like skeleton
What do corals have living inside them?
algae, zooxanthellae
What is the function of the algae inside corals? Why do they have a symbiotic relationship?
they photosynthesise during the day, producing nitrogen and carbon for the polyp, and in return, it gets oxygen and a sunny position
they also give the coral its colour
What are the 7 specific conditions that reef building corals need?
- latitudes of between 30 degrees N/S of equator
- depth of above 30m where there is plenty of light
- marine - salinity 30-40ppt
- temperature - 23-27 degrees C
- clear waters for photosynthesis
- no sediment which may clog the polyps
- high energy levels or wave action as it incorporates more oxygen and circulates nutrients
Name the features of solitary corals
- septa
- columella
- tabulae
- calice
- dissepiments
- epitheca
CORAL - What is the septum? (septa)
radial partitions
CORAL - What is the columella?
rod like axial structure
CORAL - What are tabulae?
horizontal partitions
CORAL - What is the calice?
cup shaped hollow which the polyp sits in
CORAL - What are the dissepiments?
small, downward curving plates between the septa
CORAL - What is the epitheca?
outer wall
What is a Lagerstatte?
- a fossil site exhibiting extraordinary preservation
- and often faunal or floral diversity
Why are Lagerstatten important?
- the worlds they span when combined cover some billion years of geological time
- they complete the most important portion of the fossil record for understanding evolution
What is the Lagerstatte for the Precambrian?
Ediacara
- the Ediacaran Hills, Australia
- named after the Ediacaran geological period
How old is Ediacara?
700 million years old
- oldest fossil Lagerstatte
What is ‘Ediacaran biota’?
the collective referral for the preserved soft bodied organisms, representing the earliest known complex multicellular organisms
What is the Lagerstatten for the Cambrian?
the Burgess Shale
- high in the Canadian Rockies
- named after the nearby Burgess Pass
How old is the Burgess Shale?
505 million years old
How are Burgess Shale fossils preserved?
as black carbon films on black shales
Why are the Burgess Shales important?
a record of early Cambrian life and its early diversification
- preserves soft-bodied organisms that would otherwise be missing from the fossil record and would contribute to BIAS
What is the Silurian Lagertstatte?
Wenlock Limestone
- in Herefordshire
How old is Wenlock Limestone?
420 million years old
- one of the first fossil communities discovered and studied
What does Wenlock Limestone tell us?
The environment in which the Wenlock Reef formed
- a reef formed in shallow tropical seas
Why is Wenlock Limestone important to palaentologists?
- shows how many different sorts of organism were living at the time/in this environment
- gives clues to the relationships between these organisms
What is the Jurassic Lagerstatte?
Solnhofen
- a warm shallow sea studded with islands covered a lot of where Germany is now
How old is Solnhofen?
around 155 million years ago, towards the end of the Jurassic
How did Solnhofen become a site for preservation?
sponges and corals grew on rises in this sea, forming reefs that divided up the sea into isolated lagoons
- cut off from the ocean and terrestrial runoff
- warm and isolated = salinity rose, became anoxic/toxic in some places
- nothing could survive bar cyanobacteria/small protists like foraminifera
How did Solnhofen preserve remains?
any organism that fell/drifted/washed in were buried in soft carbonate muds, and so many soft bodied creatures were not eaten by scavengers or torn apart by currents
