Silurian Flashcards
When was the Silurian period?
444-419 million years ago
What happened to old evolutionary fauna such as the Archaeocyathans when there was an emergence of Paleozoic fauna?
Archaeocyathans made Cambrian reefs but were soon extinct which led to new reef builders in the Paleozoic such as the sponge and corals
What is a new type of sponge found in the Paleozoic fauna at the start of the Silurian? What are their structures?
Stromatoporoids
Consists of vertical pillars and horizontal layers called LAMINAE
What are other corals that are found in the Paleozoic fauna in the Silurian?
Tabulate corals
Rugose (horn) Corals
What are tabulate corals? What are the two unique features about them?
Corals formed from HONEYCOMB patterns FROM ABOVE and consist of VERTICALLY STACKED CHAMBERS
What are Rugose (horn) corals?
ONLY corals to ever form HORNS
HORN-SHAPED SKELETON OCCUPIED BY ONE POLYP
What did these 3 organisms (rugose, stromatoporoid, and tabulate) create?
Creation of the FIRST MODERNNNN-looking WAVE-RESISTANT reefs made of CORALS AND SPONGES
sets the standard for all reefs that follow
What took over once trilobites started to decline in the Silurian?
What is another name for them?
SEA SCORPIONS
Took over as dominant arthropods of the ocean
EURYPTERIDS, rivaled sharks in size
What are sea scorpions closely related to?
CHELICERATES
had a pair of FANGS for stabbing prey
What is another major group that emerges in the Silurian besides coral, sponges, and chelicerates?
CHAMBERED-SHELL CEPHALOPODS
Are there any chambered-shell cephalopods today?
The ONLY modern representative is the NAUTILUS
What happened to the Chambered cephalopods during the Silurian period?
Became abundant in the world’s oceans, some grew to nearly the height of a person
How do chambered cephalopods grow?
The addition of new BODY CHAMBERS each larger than the previous
FILLED WITH GAS to add buoyancy
How many groups existed as the shelled cephalopods? How are they different from each other?
TWO GROUPS
Nautiloids: Have simple suture between chambers
Ammonoids: More complex suture
Why did ammonoids have a complex structure?
It added structural stability, SUTURES BECAME MORE COMPLEX OVER TIME
What happened in the Silurian period that changed how shelled cephalopods looked?
During the Silurian, new coils were added to their shell to form spiral patterns
Adapted to a different lifestyle
