Terms describing teeth:

Terms describe:

Skin attachment - Teeth are anchored to the skin by collagen fibers that run into the dentine from the dermis (in sharks).

Ligamentous in fangs of rattlesnakes

Pleurodont - may be ancestral attachment

Each tooth touches the bone with the outer surface of the root, may be joined to the jaw by cement or collagenous fibers.

Acrodont - scarcely have any roots

teeth abut against the rim of the jawbone by a continuous rim of hard tissue (most Osteichthyes).

Thecodont - roots of teeth in sockets (alveoli) in jawbone

The replacement of teeth in the mouth

Most vertebrates replace their teeth continuously, generation after generation, throughout life.

polyphyodont

Most mammals have only 2 generations of teeth.

Some acrodont teeth and plates of fused teeth are never replaced.

Whether the teeth are the same or different in shape

Homodont - Teeth are all about the same shape (most vertebrates, few mammals).

Heterodont - Teeth have different form and functions in different parts of the tooth row (mammals, a few fish).

Two characteristics of cheek teeth:

Bunodont: omnivorous, flat crowns covered with enamel

Lophodont: transverse ridged cusps

Selenodont: longitudinal ridged cusps

Secodont: carnassial carnivorous dentition

Brachydont: low crowned

Hypsodont: high crowned

Examples:

Alligator shows dentition that is thecodont (attachment), polyphyodont (replacement), homodont (variety of teeth).

Mammals show dentition that is thecodont, heterodont.

Mammalian cheek teeth may be designed for crushing and cutting of food - teeth capable of withstanding pressure - or designed to withstand wear.

Modifications for crushing / cutting:

1. Low crowned teeth (short and squat) grow to a specific size and then stop. The entire tooth surface is encased in enamel, the strongest of the tooth substances. Such teeth are brachydont.

Carnivores have shearing, cutting molars - brachydont, secodont dentition.

Epitomized by cat, cougar with single row of cusps

Bear, human dentition is omnivorous - brachydont, bunodont dentition

Flat crowned, dome like crushing molars

Modifications to resist wear:

2. Tall, high crowned hypsodont dentition

White - enamel

Brown - dentine

Enamel wears less than dentine or cement between crowns, leaving a rough, file-like surface.

Self-sharpening file

Deer - ridges of teeth run anterior-posterior (front to back)

moonshaped, hypsodont, selenodont dentition

chew back and forth

Beaver - hypsodont, lophodont

chew side to side

ridges run side to side

Horse- hysodont, selenolophodont

ridges run in both directions

chew in a circle

3. Rootless teeth do have unconstricted roots, grow continuously

Rodents such as beaver

Heterodont teeth require thecodont attachment.

Snake fang attached by a ligament, formed by two fused teeth to create fang.

Wolf eel has heterodont, acrodont teeth.

Decreased tooth number, reduced areas of placement

eg fish have teeth all over the mouth, on many bones of skull and on

tongue

In derived condition, teeth only on ridge of mouth

Increased size of teeth

Big teeth near pivot of jaw increases mechanical advantage, pressure

that can be exerted.

Not responsible for dental formulae

Vertebrae

know centrum, neural arch and spine, transverse process, hemal arch, zygopophyses

5 styles of vertebrae

Amphicoelus - concave on front and back, not interlocking

fish

With move to land, interlocking vertebrae (by centrum)

Procoelus - domed (convex) in back (posteriorly),

concave in front (anteriorly) - frog

Opistocoelus - domed (convex) in front (anteriorly),

concave in back (posteriorly) - turtle

Heterocoelus - fit like knuckles - bird

Acoelus - flat centrum on back and front - mammal

Resist compression, zygopophyses (spines coming off neural arch) interlock

prezygopophyses - before neural arch

postzygopophyses - after neural arch

Trunk vertebrae - between two girdles

Cervical vertebrae - condyles from back of skull fit into them

amphibians - 2 condyles

reptiles - 1 condyle, ball and socket joint

mammals - two condyles

Appendicular skeleton

ID bones of pelvic and pectoral girdles and limbs

Note walking style.

Plantigrade - ankle joint (us)

Digitigrade - balls of feet (cat)

Ungulagrade - tips of toes - toenail (cow)

Combined with reduction and fusion of distal limb elements

result is long, fast stride, increased running speed

Compare appendicular skeleton for birds and mammals, note modifications for flight

Bird skeleton - modification and adaptation for flight

furcula - fused clavicles

Cat - no clavicles (very reduced, unattached slivers of bone)

Scapulas not attached to arm, can absorb high impact, increase flexibility