Practical Specimens Flashcards
What facial components does the splanchnocranium form in cartilaginous fish?
The upper and lower jaws plus the gills.
In cartilaginous fish, what forms the skull?
The neurocranium (or chondrocranium) that forms the braincase.
The splanchnocranium (or viscerocranium) that forms the facial skeleton.
What are the 2 hypotheses for the origin of jaws?
- The first 2 gill plates migrated forwards to form the upper/lower jaws and the hyoid, and the gill slit became the spiracle.
- The gills are a completely unrelated structure derived from the velum.
What components form the skull in bony fish?
The neurocranium, splanchnocranium and the dermatocranium.
What is the dermatocranium?
Forms the bones of the roof of the skull, the palate and the upper jaw. Bones often cover the eye and nostril regions.
In bony fish, what 5 parts is the splanchnocranium composed of?
- The hyomandibular
- The quadrate
- The articular
- The angular
- The branchiostegal rays
What is NOT part of the splanchnocranium?
The operculum.
In bony fish, where does the angular insert?
Into the dentary (lower jaw bone).
In bony fish, which are the teeth-bearing bones?
The premaxilla, dentary and vomer.
What is the vomer?
A bone in the roof of the mouth at the anterior of the skull.
In bony fish, are there teeth on the maxilla?
No. Well not in the cod (a teleost).
What is the jaw articulation in bony fish?
Between the quadrate and the articular.
What kind of dentition do reptiles have?
Homodont.
What is the jaw articulation in diapsids?
Between the quadrate and articular.
In diapsids, what is the purpose of the temporal fenestrae?
For muscle attachment and to make the skull lighter.
In reptiles, where do the pectoral and pelvic girdles sit and why?
Below the vertebral column to facilitate a sprawling gait.
What is the purpose of a sprawling gait? Give 3 reasons.
- Lowers the centre or gravity for stability
- May aid camouflage
- Allows the ribcage to extend back to the hind limbs to facilitate respiration
In reptiles where does the pectoral girdle attach?
The thoracic vertebrae.
In reptiles where does the pelvic girdle attach?
The lumbar and sacral vertebrae.
How does the ribcage differ in reptiles and mammals?
Reptiles = extends to the hind limbs, no diaphragm
Mammals = gap between the ribs and hind limbs, have a diaphragm
Why do mammals have a gap between their ribs and hind limbs? Give 2 reasons.
- Mammals have an erect stance and the gap increases stride length as must swings the limbs forwards.
- Mammals are v. active and require a diaphragm/increased lung capacity
Where do the pectoral and pelvic girdles attach to the vertebral column in mammals?
To the sides of the spine.
In which plane does the spine flex in mammals and why?
Vertical - the erect stance means more weight bares down on the spine. Having zygopophyses in a vertical plane prevents the spine collapsing under the downward force.
How does the erect stance of mammals facilitate respiration?
The lungs are NOT compressed in locomotion as they would be in a sprawling gait.
In some mammals, the orbit is congruent with the single temporal fenestra. How is this loss of the temporal bar advantageous?
Leaves a bigger space for jaw-closing muscle attachment over the zygomatic arch.
What is the jaw articulation in mammals?
Between the dentary (lower jaw) and the squamosal bones.
What has happened to the articular and quadrate in mammals?
They have migrated backwards in the skull to form the inner ear bones.
In mammals, what has the articular become?
The malleus.
In mammals, what has the quadrate become?
The incus.
What kind of dentition is characteristic of mammals?
Heterodont.
Which 2 animal groups are the ONLY ones to have secondary bony palates?
The crocodiles and the mammals.
What do the nasal turbinal bones do?
Support the nasal passages.
What is the shell formed from in turtles?
Carapace and plastron = expanded flattened ribs, fused vertebrae with external body armour (dermal bone).
There is also an epidermal covering of keratin.
What kind of teeth are characteristic of lepidosaurs?
Palatal teeth.
What kind of teeth are typical of venomous snakes and why?
Small, conical teeth with long fangs. Bite prey and wait to venom to take effect.
What teeth are characteristic of constricting snakes and why?
Large, recurve teeth that further impales the prey/pushes it down the throat.
How many digits (and which ones) do birds have?
Digits 1-3.
In crocodiles, what is the secondary palate made of?
The palatine, premaxilla and maxilla
Why is the vomer exposed in teleosts?
Because they have no secondary palate.
