Early Paleozoic (Early Cambrian) Flashcards
How do we classify life on Earth? What is this term called?
Life can be divided into several groups, each more exclusive than the preceding group
THIS IS CALLED TAXONOMY
How does taxonomy work?
Each level of the hierarchy groups together animals with similar biological characteristics
What is the order of hierarchy in taxonomy from most general to most exclusive?
- KINGDOM
- PHYLUM
- CLASS
- ORDER
- FAMILY
- GENUS
- SPECIES
What does the Cambrian explosion mark?
Marks the appearance and diversification of animals in the Cambrian
MOST MAJOR GROUPS OF ANIMALS SHOW UP QUICKLY
THINGS GET MORE COMPLEX, THE NUMBER OF FAMILIES HAVE INCREASED FROM THE CAMBRIAN ONWARDS
What has occurred throughout the Phanerozoic eon regarding fauna?
There have been recognized 3 evolutionary faunas
EACH NEW FAUNA REPLACES THE OLD FAUNA IN TIME
Cambrian —> Paleozoic —> Modern
How are evolutionary faunas defined? What are faunas?
Defined by the dominance of a specific group of organisms
EACH WAS DOMINANT DURING A DIFFERENT TIME
Fauna = Group of animals !!
What was the first evolutionary fauna? What is unique about them?
CAMBRIAN FAUNA, whose fossils dominate in the Cambrian
THIS EARLY FAUNA IS VERY SHORT-LIVED
What were some Cambrian fauna (group of animals)?
Echinoderms
Arthropods
Sponges
Brachiopods
Snails
What are the Cambrian Echinoderms? What were they all classified regarding lifestyle?
These echinoderms were sediment stickers
Eocrinoids
Helicoplacoids
Edrioasteroids
What are Eocrinoids? What is the difference between these old crinoids compared to modern crinoids?
Share similarities to modern crinoids but they had a BLUNT STEM instead of a HOLDFAST (root, stick themselves to the sediment)
What are Helicoplacoids?
Also lived as sediment stickers with their blunt stem stuck into the seafloor
THEY HAVE NO CLOSE MODERN RELATIVES AND BASICALLY WENT EXTINCT
What are Edrioasteroids?
Have a broad stem at their base that they use as sediment stickers as well
THESE FOSSILS ALSO HAVE NO MODERN RELATIVE
What happened to these Cambrian echinoderms as microbial mats vanished? (Evolution)
EOCRINOIDS = ADAPTED TO BECOME CRINOIDS WITH HOLDFASTS (ROOTS)
HELICOPLACOIDS = DID NOT ADAPT AND THUS WENT EXTINCT
EDRIOASTEROIDS = ADAPTED TO BECOME ENCRUSTERS (makes a glue that helps them stick to surfaces)
What was the Cambrian arthropod? What was so unique about them?
First recognizable arthropod fossil of the Cambrian Period are the TRILOBITES
Where did the name TRILOBITE come from?
Comes from the fact that their body contains three LOBES (Left, Middle, Right)
THEY ALSO CONTAIN A HEAD, THORAX, AND TAIL
What do you call the head, thorax, and tail of the trilobites?
Head = CEPHALON
Thorax = MIDSECTION
Tail = PYGIDIUM
What is often preserved with trilobites?
Molted pieces of its exoskeleton, head, thorax, and tail
Since these pieces break off as they shed and molt
What are trilobites most closely related to?
BOTH SHARE A SIMILAR MORPHOLOGY AND LIFESTYLE
Chelicerates (ex. horseshoe crab)
How are Chelicerates different from other arthropods?
Other examples of chelicerates?
Have FANGS rather than jaws, OFTEN USED FOR EATING PREY
Spiders and Scorpions are another example
What are the earliest sponges called?
Earliest recognizable sponge fossil belong to a group called the ARCHAEOCYTHANS
SHARE MANY SIMILARITIES WITH SPONGES
What is the difference between Archaeocyathans and modern-day sponges?
Archaeocythans had notably TWO walls (INNER and OUTER WALL)
Modern sponges only have ONE wall
What was so important about Archaeocyathans regarding how they acted in their environment?
They are notable for being the FIRST animals EVER to construct reefs
BUILT REEFS LONG BEFORE CORALS EVER DID
Built ISOLATED reefs that stuck STRAIGHT UP from the seafloor
What happened to fossils within REEF LIMESTONE?
Fossils within REEF LIMESTONE are preserved in LIFE POSITION (Preserved oriented as they lived)
What happens to the Archaeocythans throughout the Cambrian?
By the MIDDLE CAMBRIAN, the archaeocyathans DECLINE SEVERELY and eventually go EXTINCT
What was a dominant component of the Cambrian Fauna?
INARTICULATE BRACHIOPODS
What’s the difference between ARTICULATE brachiopods and INARTICULATE brachiopods?
ARTICULATE = has a hinge
INARTICULATE = NO hinge
What showed the emergence of animals during the Cambrian explosion?
Due to the emergence of shells, shell is necessary for preservation as a fossil
Did animals exist before shells first appeared?
YES, it is common to find tracks from trilobites before their shelled fossils show up in rocks
Another ex. Tracks from snails feeding pre-date snail shells, scratch marks during the Proterozoic pre-date snail shells
RADULA SCRATCH MARKS FROM THE PROTEROZOIC PRE-DATE CAMBRIAN-AGE SNAIL SHELL FOSSILS
