Mammalogy

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Kingdom Animalia

some form of free-moving, heterotroph, multicellular, DNA in the nucleus, no cell wall

Phylum Chordata

notochord, stiff dorsal bundle of nerves

Subphylum Vertebrata

Vertebrae surrounding spinal chord

Class Mammalia

Hair, mammary glands, and 3 specific inner-ear bones

Mammalogy

The study of the class mammal

Common features that aren’t unique to mammals, nor do all mammals have them

Internal temperature control (Birds also have)

Most live birth (Viviparous) (Some reptiles, amphibians)

How do we study mammals?

Taxonomic and Functional perspectives

Why do we study mammals?

Mammals have uses to humans, either as predators or prey
pets
source of food
recreational hunting
some pose health risks to humans
reservoirs and vectors of disease
damage the environment (beavers etc)
conservation
Learn about ourselves

Tetrapods (Devonian)

Animals with 4 legs
Lobe-finned fish
Moved onto land and started evolving legs

Amniotes

• Carboniferous

• No longer includes amphibians

• Rose from amphibian-like tetrapods

• Cleidoic egg

• Lays eggs on land

• Amnion

• No more larval stage

• Common ancestors of all reptiles, birds, and mammals

Amnion

Own personal “pond” for your embryo

Anapsid

• Sea turtles

• No lateral temporal fossa

Diapsid

• 2 lateral temporal fossa

• Crocodiles, birds

What is the advantage of having lateral temporal fossa?

• Holes are for muscle attachments to the jaw

• Allows muscles to pass through holes, mechanical advantage

Euryapsid

• All extinct

• Ichthyosaur, swimming dinosaurs

• ONE lateral temporal fossa

Where is the lateral temporal fossa on the euryapsid?

Lateral Temporal Fossa located above the postorbital + squamosal suture (connection between these bones)

Synapsid

• Eventually became mammals

• ONE Lateral Temporal Fossa

• big hole, zygomatic arch

Where is the lateral temporal fossa located on the synapsid?

below the postorbital + squamosal suture

What bone became the stapes?

The Stapes (it never changed)

What bone became the Incus (middle ear bone)

the Quadrate

What bone became the Malleus (first ear bone)

the Articular

When did we start considering animals definitively “mammals”?

When there became articulation between the squamosal and dentary bones

Dyphodont Dentition

Having 2 sets of teeth (baby teeth and adult teeth)- changes diet when you are a baby vs older

Complex occlusion

How the teeth fit together when the mouth is closed (like molars)

Prototherians

Egg-laying mammals, monotremes

Platypi and echidnas

numerous and diverse

Distinct mammalian structural features, but still have key structures/ancestor

Therian

At the split off, gained holoblastic cleavage (true breasts)

Placentation

Viviparity

Testicular descent

Split into marsupials and eutherians (everyone else)

Tribosphenic molars

Complex occlusal pattern, got stuff in threes, grinding and scissoring

What happened to the temporal opening between synapsids to mammals?

The temporal opening enlarged

What happened to the maxillary and palatine bones between synapsids and mammals?

Extended posteriorly and medially, forming a secondary palate. (Moved back and towards the middle, allows for better separation between nasal and oral cavities, breathe while chewing)

What happened to the nares (nostrils) between synapsids to mammals?

Moved posteriorly (back)

What happened to the occipital condyles between synapsids and mammals?

1 occipital condyle became 2

What was the trend in dentition from synapsids to mammals?

Not all, but most changed from heterodont to homodont

Heterodont dentition

Homodont dentition

What happened to limbs between synapsids and mammals?

Rotated 90 degrees from “splayed” stance to directly under the body

What happened to the ribs between synapsids and mammals?

Lost cervical and lumbar ribs,
number and size of thoracic ribs reduced

What happened to the carpal and tarsal bones between synapsids and mammals?

number of carpal and tarsal bones reduced

What happened to the phalangeal formula (number of finger/toe bones) between synapsids and mammals?

#phalangeal bones reduced

Skeletal characteristics of Modern Mammals

Single dentary bone (lower jaw)

3 ossicles of the middle ear (Malleus/Articular, Incus/Quadrate, Stapes)

2 occipital condyles

Epiphyseal plate on many long bones

What do the occipital condyles do?

Articulate with atlas of spinal cord, allow greater range of head motion

What is the epiphyseal plate?

growth plate

Soft tissue characteristics of modern mammals

Hair

Four-chambered heart, with functional left aortic arch

Biconcave erythrocytes (red blood cells) that enucleate (have no nucleus)

Mammary glands

Muscular diaphragm

What are most fossil lineages described by?

Only their teeth!

What does dentition reflect?

Trophic level and feeding specialization

What bones can teeth occur in in mammals?

Premaxilla, maxilla, and dentary

3 Layers of Skin

Epidermis, Dermis, Hypodermis

Layers of epidermis

Strata germinative, strata granulosum, strata cornea

Incisors

• Anterior most teeth

• Rooted in premaxilla/dentary bones

• Cut or gnaw

• Simple with a single root

Canine

• Posterior to incisors

• Only one pair of upper and lower

• Generally unicuspid with a single root

Premolars

• Posterior to canines and anterior to molars

• More complex than anterior teeth

• Generally smaller than molars

• Two roots

• Unicuspid or multicuspid

• Have deciduous counterparts

Molars

• Multicuspid

• 3 roots

• No deciduous counterparts

Deciduous

Have baby teeth + Adult teeth

Types of Insectivores

Aerial, Semiaquatic, Terrestrial

Insectivore