Morphology of MammalsMorphology of Mammals

By : Geonyzl L. AlviolaBy : Geonyzl L. Alviola

What is a MAMMAL?

whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.

Mammals are divided into three main categories depending how they are born..

1. monotremes1. monotremes

2. marsupials2. marsupials

3. placentals 3. placentals

MonotremesMonotremes

most primitive mammals most primitive mammals mammals lay eggs; after the babies mammals lay eggs; after the babies

hatch, the mothers nourish their hatch, the mothers nourish their young with milk (Except for platypus)young with milk (Except for platypus)

name monotreme means "one-holed," name monotreme means "one-holed," referring to the referring to the cloacacloaca, a single hole , a single hole that serves the urinary tract, anus, that serves the urinary tract, anus, and reproductive tract in monotremes. and reproductive tract in monotremes.

platypus

spiny anteater

Placental mammalsPlacental mammalsPlacental mammals Placental mammals are characterized are characterized

by the following: by the following: Brain capacity is increased, allowing Brain capacity is increased, allowing

more capacity for memory, learning, more capacity for memory, learning, and conscious thought. and conscious thought.

Milk-secreting glandsMilk-secreting glandsMammals show behavioral flexibility, Mammals show behavioral flexibility,

the ability to expand on the basics the ability to expand on the basics with novel forms of behaviorwith novel forms of behavior. .

Hair covers at least part of the Hair covers at least part of the body (whales are an exception). body (whales are an exception).

Dentition (incisors, canines, Dentition (incisors, canines, premolars, and molars) is premolars, and molars) is extensive and specialized to meet extensive and specialized to meet dietary habits. dietary habits.

Placental mammals nourish their Placental mammals nourish their young within the mother's uterus young within the mother's uterus by the placenta that is a by the placenta that is a composite of maternal and fetal composite of maternal and fetal tissue. tissue.

Examples of Placental MammalsExamples of Placental Mammals

MarsupialsMarsupials

morphological feature which sets the marsupials apart from other mammalian groups is the marsupium, or pouch.

Females have 3 vaginae and 2 uteri but only a single opening - the cloaca

Most males have a 2 pronged penis just for the passage of sperm, and the cloaca for all waste excretion.

Metabolic rates.Metabolic rates. Metabolic rates in marsupials are also Metabolic rates in marsupials are also significantly lower than other mammals of significantly lower than other mammals of similar sizes, and life-spans are often similar sizes, and life-spans are often shorter. shorter.

Feeding HabitsFeeding Habits

Animals were also divided according to Animals were also divided according to its feeding habits.its feeding habits.

1. carnivorous1. carnivorous

it also include the insectivoresit also include the insectivores

2. Omnivores 2. Omnivores

that eats both plants and animalsthat eats both plants and animals

3. Herbivores (but they are several types of 3. Herbivores (but they are several types of herbivoryherbivory

Types of herbivoresTypes of herbivores

Granivory "seed eating“Granivory "seed eating“Folivory "leaf eating", Folivory "leaf eating", Frugivory "fruit eating", Frugivory "fruit eating", Nectivory "nectar eating", Nectivory "nectar eating", Gumivory "gum eating", Gumivory "gum eating", Mycophagy "fungus eating" Mycophagy "fungus eating"

Examples of seed eating mammalsExamples of seed eating mammals

deer

squirrels

Folivory "leaf eating", Folivory "leaf eating",

Three-toed-sloth

(Bradypus variegatus)

Lake Gatun, Republic of Panama.

FrugivoryFrugivory

Types of GaitTypes of Gait

GaitGait is the pattern of is the pattern of movementmovement of the of the limbslimbs of terrestrial animals, including of terrestrial animals, including humanshumans, during locomotion. Most animals , during locomotion. Most animals use a variety of gaits, selecting gait based use a variety of gaits, selecting gait based on on speedspeed, , terrainterrain, the need to , the need to maneuvermaneuver, , and energetic efficiency. and energetic efficiency.

Gaits are generally classed as Gaits are generally classed as "symmetrical"symmetrical" and " and "asymmetrical"asymmetrical" based " based on limb movement. on limb movement.

In a In a symmetrical gaitsymmetrical gait, the left and , the left and right limbs of a pair alternate, right limbs of a pair alternate,

while in an while in an asymmetrical gaitasymmetrical gait, the , the limbs move together. limbs move together.

Other types of GaitOther types of Gait

Graviportal – Graviportal – adapted to support adapted to support great body weight great body weight

ex. elephantsex. elephants

Hippopotamus

Rhinoceros

Cursorial or Running Cursorial or Running

- slender, long - slender, long

limbs, legs limbs, legs

under bodyunder body

- example - example

deer, horsedeer, horse

Cursorial or RunningCursorial or Running

spinal flexion and extension adds length and velocity

Aerial Aerial

For flying mammals

VolantVolant

For gliding For gliding

Tensorial or Tensorial or DiggingDigging

* digging elements: * digging elements: teeth, feet, claws, teeth, feet, claws, head, snouthead, snout

• • moles, horned moles, horned lizard, gr. lizard, gr.

squirrelsquirrel

Saltation or hoppingSaltation or hopping

thrust: thrust:

lengthenedlengthened

hindlimbshindlimbs

tail-counterbalancetail-counterbalance

• • kangaroos, kangaroos,

some rodents, some rodents,

rabbits,rabbits,

Brachiation or arm swingingBrachiation or arm swinging

elongate handselongate hands

forming hooksforming hooks

• • fingers fingers curvedcurved

Scansorial or climbingScansorial or climbing

grasping & hooking grasping & hooking

elements- recurved elements- recurved claws, nails, claws, nails,

adhesion pads, adhesion pads,

prehensile tailprehensile tail

• • monkeys, sloth, monkeys, sloth,

tree squirrelstree squirrels

Swimming and divingSwimming and diving

streamlined body, limbsstreamlined body, limbs

modified into flippers modified into flippers (seals), (seals),

cetaceans & manatees & cetaceans & manatees &

dugongs (sirenians) lost dugongs (sirenians) lost

hindlimbs horizontal tail hindlimbs horizontal tail

flukesflukes

Swimming andSwimming and diving diving

    Kinds of teethKinds of teeth only mammals have differentiated (only mammals have differentiated (heterodontheterodont) teeth ) teeth

incisorsincisors-anterior-most teeth [uppers occur on -anterior-most teeth [uppers occur on premaxilla] premaxilla]

caninescanines--longer, conical teeth used for grasping --longer, conical teeth used for grasping cheek teethcheek teeth--post canine --post canine

premolarspremolars--cheekteeth that have deciduous --cheekteeth that have deciduous predecessors (milk dentition) predecessors (milk dentition)

molariform teeth, squarish teeth used for molariform teeth, squarish teeth used for grinding food grinding food

molarsmolars--cheekteeth that do not have deciduous --cheekteeth that do not have deciduous predecessors predecessors

NOTE that some mammals have NOTE that some mammals have homodonthomodont dentitions. dentitions. edentulousedentulous (edentate - without permanent teeth) (edentate - without permanent teeth)

A typical mammalian A typical mammalian tooth is made up of tooth is made up of three regions: the three regions: the crown, the neck and crown, the neck and the root the root

The visible part of the The visible part of the tooth that emerges tooth that emerges from the gum is the from the gum is the crown; the neck of the crown; the neck of the tooth is surrounded by tooth is surrounded by the gum. the gum.

The tooth is anchored in The tooth is anchored in the gum by the root, and the gum by the root, and a layer of bone-like a layer of bone-like tissue, called cement, tissue, called cement, fixes the root to the jaw fixes the root to the jaw bone. bone.

In most mammals, the In most mammals, the permanent teeth permanent teeth eventually stop growing eventually stop growing and their blood supply is and their blood supply is reduced, at which point reduced, at which point the teeth are described the teeth are described as ‘rooted’. as ‘rooted’.

Types of teeth based on function:Types of teeth based on function:

1. 1. incisors incisors – used for cutting– used for cutting

- located in front- located in front

2. 2. caninecanine – spike-like teeth with single – spike-like teeth with single

root root

- used for holding and- used for holding and

piercing piercing

3. 3. premolarpremolar – located behind the canine – located behind the canine

used for grindingused for grinding

4. 4. molar molar - larger than premolar - larger than premolar

Humans

DentitionDentition

The development of teeth and its The development of teeth and its arrangement in the moutharrangement in the mouth

Classification of dentition would be Classification of dentition would be based on the :based on the :

- arrangement- arrangement - shape- shape

- attachment- attachment - composition- composition

- function - function

ReplacementReplacement typically mammals are diphyodont--have a

single deciduous milk dentition some are polyphyodont--have multiple

replacement sets (Trichechidae-30+ molars)

toothed whales are monophyodont--have only a single set

Most tooth replacement is vertical. Trichechids and Elephantidae have

horizontal tooth replacement

Types of teeth as to AttachmentTypes of teeth as to Attachment

1. Acrodont – rootless teeth1. Acrodont – rootless teeth

Attached to the rim of the jawbone

e.g. lizards, tuatara

2. Pleurodont – rootless teeth,2. Pleurodont – rootless teeth,

- attached to lingual side of - attached to lingual side of

jawjaw

e.g. Lizards, snakese.g. Lizards, snakes

3. Thecodont – having teeth rooted in 3. Thecodont – having teeth rooted in

socketssockets

e.g. mammalse.g. mammals

crocodilianscrocodilians

Types of teeth as to size/shape of Types of teeth as to size/shape of crowncrown

1. Brachydont – crowns are low1. Brachydont – crowns are low

e.g. humans

pigs

2. Hypsodont – crowns are high2. Hypsodont – crowns are high

e.g. horsese.g. horses

3. Bunodont – crowns form peaks 3. Bunodont – crowns form peaks (omnivores)(omnivores)

4. Lophodont – cusps drawn out into ridges4. Lophodont – cusps drawn out into ridges

e.g. rodentse.g. rodents

5. Selenodont – cresent-shape cusps5. Selenodont – cresent-shape cusps

Dental FormulaDental Formula

All mammal species have a fixed arrangement of teeth which can be generalized into a dental formula.

The jaws of a mammal are vertically symmetrical.

Varieties of Premolars and Molars Varieties of Premolars and Molars

Insectivores eat insects. Many insects have a hard exoskeleton to protect their soft inner bodies. In order to pierce this hard body armour, insectivores of disinctive points on their molars.

hedghog (Erinaceus europaeus) cheek teeth

HerbivoresHerbivores

- Mostly are Mostly are vegetarianvegetarian

- These animals are These animals are ruminants. (these ruminants. (these are animals who are animals who are not equip a are not equip a cellulase to digest cellulase to digest the cellulose the cellulose

sheep (Ovis aries) cheek teeth

CarnivoresCarnivores

There teeth are There teeth are specialised to specialised to cope with cope with holding drown holding drown prey and tearing prey and tearing flesh. flesh.

Carnivores have a Carnivores have a special tooth in special tooth in both sides of the both sides of the jaw, these are jaw, these are called a carnassial called a carnassial teeth. These teeth teeth. These teeth are the last upper are the last upper molar and the first molar and the first lower premolar. lower premolar. These teeth are These teeth are designed to shear designed to shear through flesh. through flesh.

OmnivoreOmnivore

The premolars of The premolars of omnivores vary in shape omnivores vary in shape according to which order according to which order the animal belongs. the animal belongs. Probably the most Probably the most distinguishing feature in distinguishing feature in the Omnivore mouth are the Omnivore mouth are the molars. These teeth the molars. These teeth usually have more usually have more flattened crowns.flattened crowns.

pig (Sus scrofa) molars

Placental StructurePlacental Structure

Two characteristics are particularly divergent Two characteristics are particularly divergent and form bases for classification of and form bases for classification of placental types placental types

1. The gross shape of the placenta and the 1. The gross shape of the placenta and the distribution of contact sites between fetal distribution of contact sites between fetal membranes and endometrium. membranes and endometrium.

2. The number of layers of tissue between 2. The number of layers of tissue between maternal and fetal vascular systems. maternal and fetal vascular systems.

Classification Based on Placental Classification Based on Placental Shape and Contact PointsShape and Contact Points

Examination of placentae from different Examination of placentae from different species reveals striking differences in their species reveals striking differences in their shape and the area of contact between shape and the area of contact between fetal and maternal tissue: fetal and maternal tissue:

DiffuseDiffuse: Almost the entire surface of the : Almost the entire surface of the allantochorion is involved in formation of allantochorion is involved in formation of the placenta. Seen in horses and pigs. the placenta. Seen in horses and pigs.

Classification Based on Placental Classification Based on Placental Shape and Contact PointsShape and Contact Points

CotyledonaryCotyledonary:: Multiple, discrete areas of Multiple, discrete areas of attachment called cotyledons are formed attachment called cotyledons are formed by interaction of patches of allantochorion by interaction of patches of allantochorion with endometrium. The fetal portions of with endometrium. The fetal portions of this type of placenta are called cotyledons, this type of placenta are called cotyledons, the maternal contact sites (caruncles), and the maternal contact sites (caruncles), and the cotyledon-caruncle complex a the cotyledon-caruncle complex a placentome. This type of placentation is placentome. This type of placentation is observed in ruminants. observed in ruminants.

Classification Based on Placental Classification Based on Placental Shape and Contact PointsShape and Contact Points

ZonaryZonary:: The placenta takes the form of a The placenta takes the form of a complete or incomplete band of tissue complete or incomplete band of tissue surrounding the fetus. Seen in carnivores surrounding the fetus. Seen in carnivores like dogs and cats, seals, bears, and like dogs and cats, seals, bears, and elephants. elephants.

DiscoidDiscoid:: A single placenta is formed and is A single placenta is formed and is discoid in shape. Seen in primates and discoid in shape. Seen in primates and rodents. rodents.

Classification Based on Layers Classification Based on Layers Between Fetal and Maternal BloodBetween Fetal and Maternal BloodJust prior to formation of the placenta, there are a Just prior to formation of the placenta, there are a

total of six layers of tissue separating maternal total of six layers of tissue separating maternal and fetal blood. There are three layers of fetal and fetal blood. There are three layers of fetal extraembryonic membranes in the extraembryonic membranes in the chorioallantoic placenta of all mammals, all of chorioallantoic placenta of all mammals, all of which are components of the mature placenta: which are components of the mature placenta:

1. Endothelium lining allantoic capillaries 1. Endothelium lining allantoic capillaries

2. Connective tissue in the form of chorioallantoic 2. Connective tissue in the form of chorioallantoic mesoderm mesoderm

3. Chorionic epithelium, the outermost layer of fetal 3. Chorionic epithelium, the outermost layer of fetal membranes derived from trophoblast membranes derived from trophoblast

There are also three layers on the maternal There are also three layers on the maternal side, but the number of these layers side, but the number of these layers which are retained - that is, not which are retained - that is, not destroyed in the process of placentation - destroyed in the process of placentation - varies greatly among species. The three varies greatly among species. The three potential maternal layers in a placenta potential maternal layers in a placenta are: are:

1. Endothelium lining endometrial blood 1. Endothelium lining endometrial blood vessels vessels

2. Connective tissue of the endometrium 2. Connective tissue of the endometrium 3. Endometrial epithelial cells 3. Endometrial epithelial cells

1. 1. Centric:Centric: the embryo expands to a large size the embryo expands to a large size before implantation, then remains in the center of before implantation, then remains in the center of the uterus. the uterus. Examples include carnivores, Examples include carnivores, ruminants, horses, and pigs.ruminants, horses, and pigs.

2. 2. Eccentric:Eccentric: The blastocyst is small and implants The blastocyst is small and implants within the endometrium on the side of the uterus, within the endometrium on the side of the uterus, usually opposite to the mesometrium. usually opposite to the mesometrium. Examples Examples include rats and mice.include rats and mice.

3. 3. Interstitial:Interstitial: The blastocyst is small and erodes The blastocyst is small and erodes through endometrial epithelium into subepithelial through endometrial epithelium into subepithelial connective tissue. Such implantation is often connective tissue. Such implantation is often called nidation ("nest making"). called nidation ("nest making"). Examples include Examples include primates, including humans, and guinea pigs.primates, including humans, and guinea pigs.