Vertebrates Flashcards
Who are the vertebrates?
Successful group of phylum chordates.
Only arthoropods came close to beating us out.
however: issue! they are composed of intricate bones that are held together with tissues, which are readily broken up and distributed. Disarticulate rapidly after death. not good preservation.
What are the characteristics of Chordates? (sometimes in embryo)
- Bilateral symmetry
- Have gill slits
- Dorsal chord (spinal chord) running from brain to mucles/organs
- Notochord: stiff cartilage that supports nerve chord.
- Post anal tail
- Blood circulates forward in main ventral vessel and backward in dorsal vessels.
- Myotme V muscle blocks.
What is a Lancelet Branchiostoma?
Primitive chordate, has many of its features.
What is a subphylum urochordata?
Most primitive chordate, including sea squirts (tunicates)
Adults lived fixed to sea floor but larvae have tail and notochord and swim around. then butt their heads onto a rock and stay there until they die as filter feeders.
Describe vertebrate characteristics?
Surrounded by a vertebral column of bone or cartilage, there is a head end enclosed in a skull.
Ventrally located front.
Developed sensory organs.
What are clades?
Appearance of a new novel charictar shown by a node. Tips of cladogram are classified taxa. Everyone under a node needs to have those characteristics.
Need to be monophyleticly grouped i.e. Mammals. Containing all descendants.
What is Paraphyletic and polypheletic?
Para: group that doesn’t contain all of its descendants.
Poly: not a nested grouping (random taxa)
Why don’t fish exist?
THeir group doesn’t contain all the decendants, its paraphyletic!
What are the broad categories of the things we call fish?
Agnathans (jawless)
Gnathostomes (jaws)
Gnathostomes include Acanthodians, placoderms, chondrichthyes, osteichthyes.
What are pikaia?
Found at burgess shale, member of cephalocordata (chordates with head but no skull)
Same group that included lancelets. Very small (pinky finger sized)
What are myllokunmingia?
Size of paper clip, thinner than pikaia, distinctive head, myotomes, fins, notochord.
Has visible gill slits (unlike pikaia), had pharynx, digestive tract and a heart.
More definetely an early chordate than pikaia
What are Haikouichthys?
Same size as myllokunmingia but slimmer. Definite head and skull, and other chordate features. Swam in shoals.
FIRST TRUE VERTEBRATES first real “fish”
very highly debated.
What are conodonts?
Range from cambrian to triassic.
Known from tooth like structures called “conodont elements” that were initially thought to be from different species but were recognized as elements of an apparatus. Made of calcium phosphate.
Remained a mystery what they were for until in Granton Shrip bed in scotland, an unusual fossil with paired eyes and v muscle blocks (myotomes) was discovered with notochord, swimming fin AND conodont elements.
Other specimins fouund in Soom shale in south africa.
Apparatus for grabbing, grinding and slicing up food.
Not the direct ancestor of any later group of vertebrates. BEcome extinct in Triassic/jurassic extinction.
What are living examples of agnathans?
Hagfish and Lampreys that mostly have parasitic lifestyles.
Hagfish are old boys from cambrian. Regulate oxygen levels in their body and produce slime.
What are heterostracans?
Earliest abundant fish with a flattened head shield (devonian and silurian) that evolved in the oceans but moved to freshwater. Never had fins, only swam with tail. Variety of lifestyles. Poor swimmers, but may have used jet propulsion.
