What Kind Of External Features Are Used To Separate Mammalas From Other Animals

MAMMALIAN CHARACTERISTICS

Many of the well-nigh important and diagnostic mammalian characteristics serve to further intelligence and sensibility, promote endothermy, or to increase the efficiency of reproduction or the securing and processing of food.

Basic structural body program is inherited from Therapsid mammal-like reptiles.

Survival through mammalian development was perhaps due to their ability to motion and to think more quickly than their Archosaurian counterparts.

Morphological trends were toward structural simplification:
    � skull and jaw bones lost or reduced in size
    � limbs and limb girdles simplified, reduced, and less laterally splayed

Fossil record provides petty evidence on when endothermy actually developed.

Diagnostic or Distinguishable Characteristics of Mammals:

Soft Tissues
Skin glands:   Mammalian skin contains several kinds of glands not found in other vertebrates.
    Mammary Glands: Provide nourishment for the young during their postnatal flow of rapid growth.
    Milk Limerick: Milk limerick varies with species:
    Cow�s milk 85% H2O
    Dry weight xx% Fat
                     xx% Proteins
                     sixty% Sugars - largely lactose
    also have sweat, sebaceous, scent, and musk glands

Hair: bodies of mammals typically covered with pilus, which has no structural homology in other vertebrates.
    - maybe developed before a scaly roofing lost in Therapsid reptiles
    - consist of expressionless epidermal cells that are strengthened by keratin

Fat and energy storage:
Fat and adipose tissue but are of vital importance as:
    � free energy storage
    � a source of heat and water
    � thermal insulation
    Lives of many mammals punctuated by times of crisis when nutrient is in short supply or energy demands are commonly high

Circulatory arrangement:
    Highly efficient system with iv-chambered heart acting as a double pump
        The RIGHT side receives venous blood from the body and pumps it to the lungs for oxygenation.
        The LEFT side receives oxygenated blood from the lungs and pumps it to the body.
    Erythrocytes biconcave, enucleated disk as possible mechanisms for increased oxygen-carrying chapters.

Respiratory system:
    Lungs are large and, together with the eye, virtually fill the entire thoracic crenel.
    Movements of air into and out of the lungs and volume of exchange due primarily to muscular diaphragm.

Reproductive arrangement:
    Both ovaries are functional and the ova is fertilized in the oviducts.
    Embryo develops within the uterus and lies within a fluid-filled amniotic sac
    Nourishment for embryo comes from the maternal blood stream via placenta
    Male testes typically contained within the scrotum outside the body cavity

Brain:
    Enlargement of the brain�s cerebral hemisphere
Neopallium - functions as centre for sensory stimulus and initiation of motor activeness

Sense organs:
    Sense of olfactory property astute as a outcome of evolution of the turbinate bones
    Olfactory lobes enlarged in carnivorous and insectivores but lost in porpoises and dolphins
    Hearing highly developed due to three middle ear basic: malius, incus, stapes, and external pinnae.
Tapetum lucidum - reflective structure inside choroid that improves night vision past reflecting lite
Vibrissae - tactile hairs/whiskers in the muzzles and lower legs of some mammals.

Digestive system:
    salivary glands are nowadays -specialized in anteaters: mucilaginous material makes the natural language sticky

Musculature organization:
    Limb and torso musculature highly plastic
    Variations for high speed locomotion

The Skeleton
Bones changes from Reptiles to Mammals
    � simplification of skeletal elements
    � reduction in the size and number of bones
    � limbs and girdle systems simplified
    � axial skeleton becomes more than rigid
    � ossification of big parts of the skeleton
    � evolution of epiphysis and diaphyses
    Skull
    � increased encephalon instance size
    � sagittal and lambdoidal crest increased
    � temporal muscle origin
    � zygomatic curvation protects eyes and provides an origin for the masseter
    � turbinal bones within the nasal cavity (improved scent/saturation of air)
    � foramina permit passage of cranial fretfulness
    � iii centre ear ossicles
    � dentary bone articulates directly with the squamosal
    � hyoid apparatus supports trachea, larynx, and base of operations of the tongue
    Teeth:
    � Heterodonty - specialized for feeding/diet
    � Originate in the premaxilla, maxilla, and dentary
    � Dentine covered past enamel
    Axial skeleton - limbs and girdles:
    � five well-differentiated vertebrae: cervical, thoracic, lumbar, sacral, caudal
    � sternum well developed to form a rigid rib cage
    � limb motion generally restricted to fore-aft directions in distal joints; more solid hip and shoulder attachments
    � pelvic girdle has characteristic shape: illium projecting forward and ischium and pubis back - all solidly fused
    � standard blueprint of bones in manus and foot (manus and pes) ii-3-3-3-iii

Diagnostic Mammalian Traits:

Pelage = hair
Ears
Mammary glands
Diaphragm
Left aortic curvation
Enucleated erythrocytes
3 centre ear bones
Single dentary
Dentary/squamosal jaw articulation

Mammal - a hairy, endothermic, homeotherm which, in most cases, bears live young which are nursed from mammary glands

Studying the development of Mammals:
    � helps us understand where and why they are distributed
    � understand development
    � sympathise our past

Era  =»  Catamenia  =»  Epoch

Eras:
Precambrian or Protozoic- to 570mya
        Commencement life - algae, bacteria, worms
Paleozoic (old) - 570 - 225mya
        Age of fishes
Mesozoic (middle) - 225 - 65mya
        Historic period of reptiles  ~twenty reptilian orders
Cenozoic (recent) - 65mya to present
        Age of mammals  ~thirty mammalian orders

Mesozoic mammals tended to be somewhat insignificant - limited fossil prove indicated holding  to conservative mouse-like form and quadrupedal locomotion

Dramatic adaptive burst following the extinction of the dinosaurs

Why and so many mammals in such a brusk time?
Plate tectonic and continental drift
Mesozoic - Pangea 230 mya
Laurasia - Europe and Asia - northern
Gondwanaland - Republic of india, S. America, Africa, Antarctica, Australia, southern

When mammals arose, continents were fairly shut together
    - pieces breaking off with groups of mammals
    - dissimilar conditions evolved different mammals
    - geographic isolation

Mammals evolved from Synapsid reptiles

i. former reptile group
2. past its peak prior to dinosaurs
3. competition from other reptiles
4. named for skull blazon
5. ii important orders - Pelycosauria (primitive) and Therapsida (avant-garde)

Evolution of the Skull:
Synapsid (one window) skulls:

ane. permit jaw muscles to bulge
2. more surface area for musculus attachment
3. lighter skull
4. opening thickened around edges due to pressures

Guild Pelycosauria 1. primitive gild that gave ascent to the Therapsids 2. outset grouping to depart radically from the basic reptilian pattern = 300mya 3. �bowl lizards� pelvic structure immune organs to be carried off of the ground- increased agility 4. many changes in size, teeth, skulls, jaw musculature five. many forms evolved 6. may have had increased torso temperature, appetites, and feeding effectiveness

Dimitrodon 1 i/2 - 3m long Predaceous - jaws deep, bigger muscles, canines developing and lots of sharp teeth - no true heterodonty Unique sail structure - brandish and/or thermoregulation. Order Therapsida 1. term refers to characteristic mammal-like arch of the cheekbone- may be for harder bite two. size variable from a rat to a bear iii. limbs thin, and body raised off ground- faster, more active? 4. secondary palate developing 5. dentary condign larger vi. phalangeal formula develops two-three-three-3-three vii. chemical communication develops- sites for well developed vomeronasal organs 8. fossils suggest shine instead of scaly skin- no indications of hair ix. thought to take laid eggs, just no remains take been located egg guarding =» egg heart-searching =» egg retention =» live birth x. milk evolved from secretions to keep humidity high in egg brooders? xi. middle ear bones developed- allowed for higher frequencies to be heard: hearing sounds of insects - insectivory- (perhaps) - tooth differentiation

Disappearance??  mid-Jurassic during the rising of dinosaurs
    - forced to become nocturnal??
    - forced toward pocket-sized size??

Order Therapsida; Infraorder Cynodontia (domestic dog tooth)

- basal stock for mammals
- virtually 2m in length
- highly cursorial (limbs rotated)
- well developed secondary palate
- reduction in number of lumbar ribs = likely development of diaphragm
- elevated metabolism . . . Why?
    � diaphragm nowadays - efficient respiration, more active
    � locomoter efficiency
    � histiological bone examination - no growth rings, Haversian canals - prison cell degradation, vessel patterns
    � location of fossils - 60° latitude, no good hibernation sites for some, must produce heat to survive
    � homeothermy - insulation, sweat glands = hair??  Bear witness for pilus vibrissae pits on cynodont skulls
    � heterodonty - came with increased locomoter efficiency - probably with increased oxygen uptake

Increased locomoter efficiency and increased oxygen uptake allowed and aided in chasing and securing casualty = differentiation in teeth

Greater mastication prior to swallowing - increased area for better enzyme activeness

Dentary-Squamosal jaw articulation developing with reduction of the quadrate and articular - become free to aid in transmission of sounds and vibrations.

Secondary palate increased area of the nasal crenel
    - immune for simultaneous mastication and respiration
    - warm, moisturize, and clean air
    - increase sense of odor - chemical smells/pheromones (vomeronasal organ)

Masseter muscle has essentially the same zipper equally in modern mammals - insertion on lateral surface of dentary and originates on the zygomatic arch; enhanced control of transverse jaw movement.

First Mammals - after Cynodonts
    ~ 10cm long
    xx-30gm
    long snouts
    rows of complex teeth - probably insectivorous
    partially arboreal
    probably nocturnal - favored by endothermy

Early mammals were small - at least an society of magnitude smaller than Cynodonts
     - arose in Triassic
     - stayed small with Cretaceous (140mya)

Why stay small?
    - competition from moderate-sized not-dinosaur reptiles (turtles, crocodiles) - probably not, lived in different habitats
    - contest from small immature dinosaurs - carnivorous when young
    - lacked sophisticated evaporative cooling mechanism
    - more important features were evolving than size:  maternal intendance, soft anatomy, and physiology each demonstrated by similarities between therians and non-therians

Mesozoic Mammalian Radiation
Electric current evidence indicates that mammals probably evolved monophyletically from cynodont reptiles

Early mammals displayed structural features that distinguish them from even the most advanced cynodonts:

1. In species of like torso size, the morganucodontid brain was three or four times larger than that of even the nigh avant-garde therapsids, a reflection perhaps of greater neuromuscular coordination and improved auditory and olfactory acuity.
2. The condyle of the dentary bone fit into the glenoid fossa of the squamosal bone.
3. The cheek teeth were differentiated into premolars and molars, and the premolars were probably preceded by deciduous teeth.
4. Chewing was on one side of the jaw at a time, and the lower jaw on the side involved in chewing followed a triangular orbit as viewed from the forepart
v. During chewing, the inner surface of the upper molars sheared confronting the outer surface of the lower molars.
six. The cochlear region of the skull was far larger and more than conspicuous ventrally than in cynodonts.
7. Body weight, probably xx to 30 grams, was an guild of magnitude smaller than in any Heart Triassic cynodont .
8. The pelvis was esscntially mammalian, with a rodlike ilium and a pocket-size pubis .
9. As role of a series of specializations allowing rotary head movement, the dens of the axis was large and protuberant and fit into the atlas.
10. The thoracic and lumbar vertebrae arched dorsally, the thoracic vertebrae had narrow, posteriorly directed neural spines, and the lumbar vertebrae bore dorsally directed neural spines.

Early radiation best described as a dichotomy betwixt ii early groups, the Kuehneotheriidae and Morganucodontidae.

Morganucodontidae - basic triconodont molar - may take evolved triconodons, docodonts, and monotremes. Kuehneotheriidae- triangular molars - may accept given rise to the therians (symmetrodonts, pantotheres, marsupials, and eutherians)

Increasing evidence indicates more than circuitous relationships amongst early on mammals - only the monotremes, marsupials, and eutherians survive today.

Order Triconodonta - late Triassic early on cretaceous - i of the oldest primitive prototherians - predaceous - largest = house cat size - heterodont - 14 teeth in dentary - canines large - molar cusps 3, organisation in front end-to-dorsum row Order Docodonta - late Jurassic - roughly quadrate teeth -cusp non aligned anterioposteriorly Lodge Symmetrodonta - late Triassic to belatedly Cretaceous - probably predaceous - three fairly symmetrical cusp

Order Multituberculata - first appeared in the late Jurassic period to Tertiary - first mammalian herbivores - wide spread in both the old and new worlds - Ecologically equivalent to rodents - strongly built lower jaw with attachment for powerful jaw muscles - 2 or 3 incisors - diastema in forepart of premolars, three parallel cuspules - olfactory lobes enlarged

It has been generally accepted that eutherians and metatherian mammals evolved from the Order Pantotheria
    - profile of the ventral border of the dentary bone is interrupted past an athwart process
    - the lower molar has a posterior �heel� which is separated by the talonid
    - the trigonid section of the pantotheric lower tooth and the triangular upper molar resemble the corresponding teeth of some primitive eutherians and metatherians

During the Cretaceous, land dwellers were banned from intercontinental movement by oceans and seaways
    - populations of mammals on unlike continents evolved in isolation under different environmental conditions
    - primeval known marsupials are from late Cretaceous Canada, Westerns N.A. and Peru.
    - mammalian radiation coincided with a burst of flowering plants (Angiosperms), Lepidoptera (moths and butterflies), Isoptera (termites), and Coleoptera (beetles).

Partial Classification of Mammals ? = Extinct

Kingdom Animalia
    Phylum Chordata
    Subphylum Vertebrata
        Grade Mammalia
            Bracket Prototheria
                Infraclass Eotheria ?
                    Order Tricodonta ?
                        Family Morganneodontidae ?
                    Club Docodonta ?
                        Family Docodontidae ?
                Infraclass Ornithodelphia
                    Guild Monotremata
                        Family Tachyglossidae
                        Family Ornithorhynchidae
                Infraclass Allotheria ?
                    Order Multituberculata ?
                        (?) Family Haramyidae ?
            Subclass Theria
                Infraclass Trituberculata ?
                    Order Symmetrodonta ?
                        Family Kuchneotheriidae ?
                    Order Pantotheria ?
                Infraclass Metatheria - all marsupial mammals
                Infraclass Eutheria - all placental mammals

NONEUTHERIAN MAMMALS: MONOTREMES AND YardARSUPIALS

Monotremes and Marsupials can easily be considered apart from other mammals

� both are relatively primitive

� have different reproductive patterns

Monotremes - egg-layers

Marsupials - bear tiny, poorly developed immature

Monotremes diverged from other mammals ~190mya

Marsupials diverged from Eutherians ~100mya

ORDER MONOTREMATA

Represented by three genera, each with a single species. Monotreme translates into "i-hole" - refers to the presence of a cloaca, a single reproductive/excretory outlet

Monotremes retain many reptilian traits:

• egg-layer - incubate in a bird-similar fashion
• extra basic in pectoral girdle - more rigid than therians� interclavicle, clavicles, precoracoids, coracoids
• epipubic basic
• splayed opinion and carriage
• no lacrimal basic
• reproductive tract
• cloaca, shell gland, penis-no baculum, seminal vesicles, prostate, testis intestinal
• cervical ribs
• lack vibrissae
• brain not well developed - no corpus collosum, reduced convolutions
• no auditory bullae - surrounded by tympanic rings
• lack mammae - no nipples - young suck milk from 2 lobules in a temporary pouch

ORDER INSECTIVORA

Refers to the nutrition of many, but . . . taxonomic doubtfulness and disagreements on classification are causing many issues - the order serves as a user-friendly "grab-all"

Most archaic eutherian guild

Third largest order with ~77genera and 400spp.

Rodents ~1700spp.

Chiroptera ~850spp.

Distributed through most of both hemispheres except Australian region, northern part of Southward America, and polar regions

Originally idea to accept evolved in Former World (Europe and Asia) and moved into the New World

- primeval fossil Insectivores (Batodon) from mid-Cretaceous Northward America ~100mya
- oldest members of clearly recognized families - soricids and talpids - from Eocene ~50mya "Catch-purse" of forms making information technology difficult to form subclassifications - many generalized forms
- some could be lumped
- some may be considered as separate orders
- Butler (1972) ". . . any fossil eutherian non closely related to one of the other orders is classified in the order Insectivora."

Order Macroscelidea - Elephant shrews

Gild Scandentia - Tree shrews

General characteristics:

- usually small
- long narrow snout
- 5 clawed digits
- normally short, close-set fur
- anterior vena cavae paired
- pinnae small to absent-minded
- minute eyes - some covered with skin
- scrotum when present anterior to penis
- most insectivorous
- terrestrial, fossorial, semiaquatic
- plantigrade - heels touch basis when walking

Full general cranial traits: - minor encephalon case with smooth cerebral hemisphere
- no auditory bullae - ring-shaped tympanic bone
- jugal reduced or absent
- zygomatic curvation absent in some
- usually enlarged and specialized incisors with sharp shearing cusps
- canines usually reduced
- some genera retain tribosphenic molars Social club CHIROPTERA

2nd largest order of mammals with ~170 genera and 850 species

Characterized as the only mammal to accept evolved truthful flying

Represents the most poorly understood/misunderstood groups of mammals

Relatively recent biological research has revealed:

• extraordinarily circuitous social beliefs, including harems maintained past males and complex vocalizations
• coordinated neuromuscular and behavioral adaptations allowing detailed perception of prey and their environments by the apply of audio
• unsurpassed ability to conserve daily energy or survive through periods of stress by drastic reduction of metabolic rates

Bats take near cosmopolitan distribution, being absent only from the arctic and polar regions and from isolated oceanic islands

Frequently abundant members of temperate faunas merely attain their highest densities and greatest diversities in tropical and subtropical areas

Bats occupy a number of terrestrial environments, including:

• temperate, boreal, and tropical forest
• grasslands
• chaparral
• deserts
• as well man-made structures beget first-class roost sites and agricultural areas having high insect abundance

PALEONTOLOGY

Because of their small-scale size, power to fly, delicate structure, and greatest abundance in tropical areas where fossilization rarely occurs, but fossils are rare

Icaronycteris alphabetize - from Eocene beds in Wyoming the oldest known undoubtable bat fabric first described by Jepsen in 1966 claws on the first two digits of the hand fairly brusk, broad wings Other fossils prove insectivory during Eocene - moth scales in gut Late Eocene and Oligocene deposits in France have shown evidence for Microchiroptera families Emballonuridae, Megadermatidae, Rhinolophidae, and Vespertilionidae Megachiroptera appeared in Oligocene in Italy

Fossil record shows little alter in some families since Eocene, indicating proficient adaptations to their particular environments - a sharp contrast to Oligocene horses which were sheep-sized and three-toed

Oligocene Tadarida were nearly identical to present-day members of the Molossidae family unit

Paleocene origins of bats seems probable, followed by a belatedly Cretaceous divergence from insectivorous stock

CHARACTERISTICS

The most of import feature near bats is their accommodation for flying

bones of the arm and paw (except thumb) are elongated and slender

flight membranes extend from the body and hind limbs to the arm and the fiveth digit, betwixt the fingers, from the hind limbs to the tail, and from the arm to the occipitopollicalis muscle - patagia

the hind foot is free from flight membranes, which may extend to the ankle Uropatagium (tail membrane) may not ever exist present as in the tail - multiple combinations

ears usually have some form of a tragus - flap in the front part of the ear - dissimilar shapes in dissimilar species

Calcar may or may not be nowadays - bony element extending off the pes which helps to support the uropatagium - may also be keeled (cartilagenous extension)

 

• serratus anterior muscle tips lateral edge of scapula downwards to help power downstroke
• adductor and abductors of the forelimb heighten and lower the wings (major muscles of flight) contrast with flexors and extensors of terrestrial mammals
• the clavicle articulates proximally with the enlarged manubrium and distally with the acromion process and base of the coracoid process

The hind limbs:

• rotated either 90 to the side from the typical mammalian posture - reptilian posture - or 180? - spiderlike posture - used for suspending the brute upside downwards
• reduced to conserve weight
• fibula commonly reduced
• back up for the uropatagium, in the class of the calcar

Reduction in Fly Weight:

• considerable advantage in metabolic economy to reduce distal components of the wing - must move faster as compared to proximal portion
• calorie-free wings are easier to command with speed and precision during rapid maneuvers associated with chasing insects
• movement of the elbow and wrist joints limited to one plane - elimination of musculature involved in rotation and bracing
• extension and flexion of the wing transferred from distal muscles of the forearm and hand to large proximal muscles (pectoralis, biceps, triceps)
• add-on of connective tissues with musculus reduction to "automatically" extend the chiropatagium with extension of the elbow

ORDER PRIMATES

Primates represent the seven^th largest order with 51 genera and 168sp

• xvi genera and 50 species in the New Earth
• often considered to exist the most important mammals (ego)
• no one denies that modern man is primate yet . . .
• few people understand why man is classified with animals such as the tree shrew, loris, and aye aye
• anthropologist have difficulty in defining what man is
• primates (living or fossil) are divers past an overall blueprint
• The fossil record is from the:
• Palocene and Oligocene of North America and Europe
• Miocene of Africa and Europe
• Pleistocene and recent of South America, Asia, Africa, and Madagascar

Club Scandentia - tree shrews as primates

5 genera, ~16sp

• Appearance - don't expect like primates merely internally primate-like, tin't base of operations on superficial appearances
• Multiple breast pairs - accept them but reduced in number, one-3 pairs archaic condition
• Muzzle too long - but shorter than well-nigh insectivores - birdie�south long
• External and center ear - external human being-like, middle ear primate-like
• Olfaction - rely on hearing, primates are more than vision oriented with increase in brain section for vision
• Vision - poor binocular but retina is primate-like
• Throat-chest scent glands - lower primates scent mark
• Nonprehensile feet and hands / non opposable simply is moveable
• No baculum or os clitoris basic - neither do humans
• Multiple births - primates don't unremarkably, but more primitive groups do
• Maturation period as well brusk - mature quickly rather than slowly - lots of differences in recognized primates
• Encephalon size relatively large in proportion to the body
• Blood/serological exam closer to primates
• Social behavior poorly developed

Suborder Streposhirhini	Suborder Haplorhini
Primitive	Advanced
upper lip divided	upper lip non divided
orbit and temporal fossa continuous	postorbital plate
lacrimal foramina within orbit	outside orbit
smaller braincase	larger braincase
foramen magnum posterior	ventral
olfactory oriented	vision oriented
more hairy face	less hairy confront

Rhinarium - fleshy pad with moisture glands on end of nose - cool and wet

Most nonhuman primates occur in tropical areas - considering of cultured and biological plasticity human being adapts to most biomes

Primate Pattern

Centers around adaptation to tree life and arboreal existence, secondarily evolved for life on the ground

Qualities to exploit forest canopies:

• behavioral plasticity - adaptation allows change at a second�s notice

• general beefcake - "evidently"
• neurologically complex
• individuality - nervous system allows quick thinking
• large cognitive centers devoted to easily, thumbs, and song areas

• grasping extremities - belongings on in copse
• opposable thumbs and toes
• pentadactyl
• grip powerful and precise, claws reduced to nails and more sensitive, friction ridges/callouses

• good vision - eyes in the front end of the caput

• nose reduced or rostrum dropped to move nose out of the field of view
• mobile limbs - propelled through the trees

power to hold torso erect - stand up up to free the hands

Xenarthra (Edentata) , Philodota , and Tubulidentata all share a major structural trend, the loss or simplification of dentition Xenarthrans (armadillos, sloths, anteaters): underwent tertiary radiation in South America

Pholidota (pangolins) and Tubulidentata (aardvark): Old World groups, each of which has conservatively maintained a unmarried structural plan.

Lodge Xenarthra = Edentata

"strange articulation" = new                     "no teeth" = old

Not of dandy importance but are remarkably interesting because of their unique construction and unusual ecological roles, large fossil types, and remarkable Tertiary radiation in South America

All share a series of distinctive morphological features:

• actress zygopophysis-like joint (Xenarthrous) which brace the lumbar vertebrae
• incisors and canines absent
• cheek teeth, when present, lack enamel and each has a single root - continuous growing
• brain example unremarkably long and cylindrical
• the hind foot is ordinarily five-toed
• forefoot has 2 or three prominant toes with large claws

Major Xenarthrous structural trends are toward a reduction and simplification of the dentition, specialization in the limbs for climbing or digging, and rigidity of the axial skeleton

Gild CARNIVORA - PREDATORS

An aboriginal, profitable (and honorable) occupation

Appeared in the early Paleocene (Creodonts) earlier most of the contempo mammalian orders

Probably evolved in response to the nutrient resources offered by expanding array of herbivores

Most contempo carnivores are predaceous and have a remarkable sense of olfactory property

many carnivorous

may be omnivorous - bears

may be specialized - cats

Cursorial abilities may be express - Ursidae, Procyonidae
                          well developed - cheetah, canids

General Characters:

• larger brain case
• good sense of odour
• well-developed canines
• small incisors - usually 3/iii
• shearing and crushing teeth
• many have carnassial pair P ⁴ /yard _ane
• cheek teeth vary
• "long faced" - P 4/4, chiliad 2/3 - dogs, bears
• "short faced" - P 2/2, thou 1/1 - cats
• transverse mandibular fossa - good for biting, not for grinding
• reduced or absent-minded clavicle
• plantigrade or digitigrade
• well-developed scent glands

ORDER CETACEA (Greek = whale)

Mysticeti - baleen whales 11spp.

Odontoceti - toothed whales 67spp.

Noted as existence mammals that are about fully adapted to aquatic life

Fossil information indicates cetaceans are an sometime and successful group:

• swimming ability
• capacity to echolocate in many
• social beliefs

intelligence?

ORDER RODENTIA (Greek "to gnaw")

About half of all mammals currently alive are rodents

Plants are the well-nigh abundant food source - rodents adjusted as herbivores to take advantage of this food supply

30 families
418 genera
~1750 species

Why so successful?

• nearly cosmopolitan in distribution
• exploit a wide spectrum of foods
• important members of almost terrestrial faunas
• often achieve extremely high population densities
• small size to utilize shelters and escape predation
• high fecundity - large number of offspring, some survive
• rapid population turnover - natural selection operates quickly

Taxonomic relationships are difficult to understand Convergence - distantly related but await akin Heteromyidae and Dipodidae - morphologically similar in utilizing dry habitats Divergence - closely related but look nothing alike Geomyidae related to Heteromyidae - gophers fossorially adapted/kangaroo rats long legged and saltatorial Parallelism - closely related and pursue similar modes of life Muridae and Cricetidae - Former and New Earth rodents frequently lumped together into the same family - look very much akin and are conspicuously related through the fossil record Evolutionary radiations has allowed Rodentia to occupy niches filled by other orders S America species resemble: rabbits     = Hydrochoerus sp. (Capybara)
antelope   = Cavia sp. (Cavy) Size extremely variable: Largest:    South America Hydrochoerus sp. - Capybara ~100 lbs North America Castor canadensis - beaver ~50 lbs Smallest: Baiomys sp. Perognatus flavus
Reithrodontomys humilis ~5g Fossil record for rodents is not very good due to small and fragile bones

• Oldest from Paleocene of North America
• Ischyromyidae - represented by but a few teeth
• Eumegamys - largest known rodent about size of hippo, skull ~ii ft long
• Castoroides - Pleistocene beaver from Mississippi river valley ~7 ft long

Early divergence of suborders based on mandibles - Dissever past Tullburg (1899) and Wood (1985)

Sciurognathi - the angular process of the dentary bone originates in the plane that passes through the alveolus of the incisor and is ventral to the air sac

Hystricognathi - the angular process originates lateral to the vertical plane of the alveolus

Most distinguishing trait for the social club are based on dental characters: Incisors

• single pair in each jaw
• roots and lurid cavities open and evergrowing
• outside enamel, inside dentine rub against each other - differential habiliment produces chisel edge
• skilful for gnawing, grasping and property, piercing

No Canines - long diastema

Cheek Teeth

• highly variable
• premolars may or may not be present
• some e'er-growing, some rooted

Dental formula reduced to a maximum of 22 teeth 1/1 0/0 ii/one iii/3 = 22

Dentition best suited for herbivory but varies

Onychomys - carnivorous
Dipodomys - omnivorous Rodents have been broken out into four taxonomic groups based on jaw musculature and mandible/skull articulation Protrogomorphs - represents the primitive condition
Sciuromorphs - squirrel-like
Hystricomorphs - porcupine-like
Myomorphs - mouse-similar

Protrogomorphs

• Masseter muscles originate entirely on the zygomatic arch toward the placement of the origin of at least 1 division of the masseter on the rostrum
• represented merely by Aplodontia rufa (Aplodontidae)

Sciuromorphs

• The insertion of the anterior part of the lateral masseter is shifted onto the inductive surface of the zygomatic curvation and the next part of the rostrum - improved gnawing and grinding
• The temporalis muscle is relatively large and the coronoid process is moderately well developed
• occurs in Sciuridae and Castoridae

Hystricomorphs The origin of the medial masseter from the zygomatic curvation to an extensive area on the side of the rostrum passes through the often profoundly enlarged infraorbital foramen occurs in Dipodidae and most Hystricognaths

Myomorphs

• The inductive part of the lateral masseter originates on the highly modified inductive extension of the zygomatic arch and the anterior role of the medialmasseter originates on the rostrum and passes through the somewhat enlarged infraorbital foramen
• occurs in many members of the Sciurognathi, including all members of the family unit Muridae

Complicated jaw activeness allows the lower cheek teeth to move transversely or anterioposteriorly confronting the upper teeth, producing a crushing and grinding action.

Cheek teeth and incisors perform distinctively different functions - musculature is required to movement the lower jaws into power positions for teeth to function - "division of labor"

Order LAGOMORPHA

Rabbits, hares, and pikas are not a very various grouping but are important members of many terrestrial communities, and are nearly cosmopolitan in distribution and were only absent-minded from Antarctica, Commonwealth of australia, and southern South America

Ii families with 13 genera and 80 species

• Leporidae - rabbits and hares
• Ochotonidae - pikas

Taxonomic origins are from the Paleocene of People's republic of china - appear to share a common origin with rodents inside the Paleocene order Anagalida

• Leporidae underwent most of it's early development in the Oligocene and Miocene of Northward America
• Ochotonidae originated in Eurasia and developed largest number in North America

Conservatism in evolutionary design may exist related to the limitations of their functional position as "miniature ungulates" - direct competition with Artiodactyla may have limited lagomorphs to a single express adaptive zone

UNGULATES

Not a taxonomic term only is a full general term for a large grouping of cursorial forms

The proper noun implies that a hoof is present

Ii Orders:

Perissodactyla - horses, rhinos, tapirs - " odd toed"
Artiodactyla - pigs, peccaries, hippos, camels, deer, antelope, cattle, sheep, goats - "e ven toed"

Came from the Condylarthra - a various group of ungulate-like mammals that existed from Cretaceous to the Oligocene

Exceptional cursorial power - Why?

• evolved at same fourth dimension Miocene grasslands were developing
• open state
• needed speed to avoid predators in the absenteeism of trees

Perissodactyls

• reached peak in Eocene with their greatest multifariousness
• declined through Miocene
• few alive today

Artiodactyla

• peaked in Miocene following adaptive radiation
• may have out-competed Perissodactyls

Cursorial Specializations

2 factors determine speed:

• length of stride
• rate of pace (#/time)

Length of footstep:
1) Lengthen the limb

• metacarpals and metatarsals elongate and fused - cannon bone
• other limb bones elongated

2) Loss or reduction of clavicle

• loss of clavical frees scapula and shoulder joint from a strongly fixed zipper to axial skeleton

\ scapula free to pivot and rotate virtually a point most its middle assuasive leg to movement farther during stride
\ absorbs stupor of foot striking footing and not transfered to entire body

3) Flexion of the spine

• well developed muscles fastened to spine
• flexed when legs under body , extended when legs outstretched

Increased rate of stride:

i) Extra joints

• full speed of foot depends in part upon the speed of each articulation and the number of joints

\ each new articulation = increment foot speed
\ greater number of joints moving in the same plane also increases the speed of the limb

How done?

• Digitigrade/Unguligrade - elevator head off ground
• Phalanges and metapodials
• Scapula gratis
• Flexion of spine

two) Specialization in musculature

• proximal migration of musculus masses
• gets weight away from extremites
• concentrates middle of gravity
• insertion points migrate proximally - the closer the musculus to the insertion point the faster the response
• distal parts lighter (fewer muscles) - less energy needed to start/stop - oftern associated with a reduction in the basic
• plane of motion limited to one - fewer muscles needed

iii) Ungulate "ankle/wrist" specializations
 

Mammals with no reduction in limb elements

fibula		tibia
calcaneum		astragulus
cuboidal		navicular
	tarsals and metatarsals
	phalanges

Ungulates

tiba and fibula (frequently fused)

astragulus (becomes weight bearing)

other tarsals

metatarsals (fused in canon bone)

phalanges

4) Other specializations

Nuchal ligament
• heavy ring of elastin connective tissue
• anchored to neural spine and occipital of skull
• helps to support head

Springing ligament
• found in both front and back feet
• evolved from muscles that flex digits
• originates on proximal 1/3 of cannon bone and inserts on phalanges
• foot on ground ® phalanges extended by weight, ligament stretched
• weight off foot ® ligament springs back and foot flips backwards

\ increases speed of human foot without calculation muscles

Feeding Specializations for Herivorous Diets:
one) Cheek teeth

• big teeth with circuitous occlusal surfaces
• premolars molariform - hypsodont
• diastema
• elongated jaw for broader teeth

2) Digestion of plant material

• lack enzymes to digest cellulose - uses bacteria
• retentiveness time varies but is long
• 30 - 45 hours in Perissodactyles
• 70 - 100 hours Artiodactyls

Artiodactyls more efficient digesters - may live longer in areas with short food supply

Microflora and Fauna:

• in caecum of Artiodactyls
• # leaner est. 10¹⁰ - divide every xx min.
• protozoa est. 10⁶ - divide every ii-three days
• originally idea to only digest cellulose
• Also
• synthesizes vitamin B
• makes amino acids, simple proteins
• dissever urea into ammonia, set Northward to make amino acids
• decompose complex carbohydrates, convert to fat acids
• produce large quantities of CO_two and Methane

Ruminants = Cud chewers

General design of stomach activeness:

• fill stomach speedily and retire to safe spot to digest
• tummy large with iv chambers
• rumen - paunch
• reticulum - honeycomb tripe
• omasum - psalterium
• abomasum - breadbasket of other mammals
• food swallowed into rumen and churned with micro flora and fauna
• regurgitated to mouth (cud) and chewed to mix with micro flora/fauna
• reswallowed
• mixed between rumen and reticulum
• enters omasum
• compressed and mixed more than, threescore - 70% H_iiO absorbed

enters abomasum - enzymatic hydrolysis of food and micro flora/fauna

Source: https://www.shsu.edu/~bio_mlt/mammals.html

Posted by: rawlsupocand.blogspot.com

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