Lecture 5 Flashcards
Describe the conodont and what it contributes to teeth
Tooth-like micro-fossils were found in the late Cambrian. They were early vertebrates.
What does the conodont look like and what key chordate features did it have?
V-shaped myomeres, notochord, caudal fin rays, post-anal tail and mineralised dental tissue. Large eye with muscles
What does the shape of the conodont teeth suggest?
Posterior: Slicing and crushing food & Anterior: impaling food
What organisms are more derived than agnathans?
Ostracoderms, small, jawless fish encased in a bony or shell-like carapace
Why are ostracoderms more derived than agnathans?
Dermal bone & olfactory tract connecting olfactory bulb with forebrain and cerebellum in the hindbrain. This is lacking in agnathans
What are ostracoderms?
A clade
What is ‘the next big thing’ in evolution?
Jaws
What gill arches were modified to become jaws?
The 1st and 2nd gill arches
Describe the evolution of the gill arches into jaws
The 1st arch gave rise to the jaws themselves and the 2nd (pharyngeal arch) is attached for support
What is the palatoquadrate? and describe it
The jaw. It is attached by ligaments to the chondrocranium and has some support from the hyoid arch (2nd).
What is amphistylic?
It means double support
What are the first 4 gnathostome characteristics?
jaws formed from mandibular arch, gill skeleton, hypobranchial muscles for suction, paired nostrils & olfactory sacs
What are the last 5 gnathostome characteristics?
1st gill slit (spiracle), 3 semi-circular canals (including horizontal canal), conus arteriosis, horizontal septum (in trunk muscles), vertebrae with centra
When did teeth evolve and why?
They evolved after jaws because placoderms lack them
Describe teeth in regards to bony fish and tetrapods
These organisms teeth imbedded into dermal bone, cartilagenous fish lack these. Cartilaginous fish (sharks) teeth form on skin as a tooth whorl that rests on the jawbone.
