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Parade of the

Comparative Vertebrate Anatomy

VertebratesVertebrates

~60,000 known species Most successful animal group in terms of

survival One of the largest group of taxa in animal

kingdom Found in various types of environments Evolved for 590M years Unique characteristics:

Presence of vertebral column Formation of cranium

TheGeologicTimeScale

Vertebrate Classification1. Agnatha2. Acanthodii3. Placodermii4. Chondrichthyes5. Osteichthyes6. Amphibia7. Reptilia8. Aves9. Mammalia

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The Vertebrates Agnathans

Ostracoderms Cysclostomes

Placoderms Acanthodians Chondrichthyans

Elasmobranchs Heterocephalans

Osteichthyans Actinopterygians Sarcopterygians

Amphibians Labyrinthodonts Temnospondyls Microsaurs Lissamphibians

Reptilians Anapsids Squamates Crocodilians

Avians Archeornithes Neornithes

Mammals Monotremata Marsupialia Insectivora Xenarthra Tubulidentata Pholidota Chiroptera Primates Lagomorpha Rodentia Carnivora Pinnepedia Perissodactyla Artiodactyla Hyracoidea Proboscidea Sirenia Cetacea

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Class Agnatha

Order: Heterostraci Order: Osteostraci Order: Anapsida Order: Coelolepida Order: Petromyzontiformes (lampreys) Order: Myxiniformes (hagfishes)

Ostracoderms

Cyclostomes

(Jawless fishes)

Ostracoderms Oldest known vertebrates (Cambrian period) Body covered with bony dermal armor (plates and tile-like

scales) – armored fishes Mostly 2-30 cm in length (longest: 2 m) Mostly freshwater habitat (few marine during Silurian period) With sense organs (eyes) and pineal body (3rd eye); nostril

(leads to olfactory sac) Filter feeders

Ostracoderm fossil from Canada(Silurian-Devonian Period)

Cyclostomes Living jawless fishes Notochord retained in adults Single median nostril No paired fin Naked skin (slime glands) With buccal funnel (adaptation to

parasitic life) – with rasping tongue andhorny denticles (lamprey)

Seven gill slits Some marine, some freshwater Lampreys are anadromous organisms

(marine but lay eggs in freshwater) Hagfishes: both gonads are present but

only one is functional

Myomyzon (Lamprey)Fossil dated during theCarboniferous period

Eptatretus (Hagfish)

Tentacles Gill slits (twelve pairs) Mucous glands

Gill openings (seven pairs) Petromyzon(Lamprey)

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Class ChondrichthyesSubclass Elasmobranchii (naked gill slits) *Order Cladoselachii (primitive paleozoic sharks) *Order Plueracanthodii (freshwater paleozoic sharks with lobed

fins) Order Squaliformes (sharks) Order Rajiformes (sawfish, skates and rays)

Subclass Holocephali (gills covered with operculum) Order Chimaeriformes (Chimaeras)

Elasmobranchs Cartilaginous fishes Placoid scales Ventral mouth With claspers (internal

fertilization) Macrolecithal egg Oviparous organism (eggs

with horny leathery shellwith tendrils)

Presence of spiracle (1st gillslit) except chimeras

Mostly marine

Elasmobranchs Squaliformes with fusiform bodies (swift swimmers) Rajiformes with dorsoventrally flattened body (bottom

dwellers) Long gestation period (2 yrs) Cranium without sutures Several sets of teeth Large animals (20 m-whale shark) Absence of swim bladder

Heterocercal tailLarge livers (bouyant oils)Pectoral fins as hydrofoilsAbsence of bones

Class Osteichthyes Subclass Sarcopterygii (Choanichthyes) – lobe-finned fishes,

fins attached to appendage (give rise to tetrapods) Actinistians – mostly extinct except Latimeria Rhipidistians – ancestors of amphibians Dipnoans – lungfishes

Subclass Actinopterygii – ray-finned fishes, modern fishes Superorder Chondrostei – chiefly paleozoic Superorder Holostei – dominant Mezoic fishes with ganoid scales Superorder Teleostei – present forms of bony fishes

Chanos chanos

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Class Osteichthyes Largest group of

extant vertebrates Bony fishes With operculum Terminal mouth With swim bladders

(air sacs)-neutralbouyancy

With cloaca Overlapping scales

(ganoid, ctenoid,cycloid,)

Fins stiffened bylepidotrichia

Actinopterygii Ray-finned fishes Fin rays joined by membranes Absence of internal nares Main distinguishing characteristic:

endoskeleton composition Superorder Chondrostei-cartilaginousSuperorder Holostei-cartilage & bones Superorder Teleostei-bone

Chondrosteans Most primitive ray finned

fishes With ganoid scales Largely cartilaginous With spiracle Ex. Sturgeon, paddlefish

can reach 8 m marine and freshwater toothless (bottom feeders) can reach up to 100 years Roe (egg) – sold

commercially as Russiancaviar

Holosteans Intermediate form of ray-finned

fishes

Freshwater

Ganoid scales; No spiracles

Single air bladder

Endoskeleton is ossified

Braincase is largelycartilaginous

Examples: Bowfin

Garpike

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Teleosts Modern fishes

Ossified skeleton

With cycloid or ctenoid scales(flexible and overlapping)

~20,000 species

Found in any body of water

With swim bladders

Homocercal (equal lobe),protocercal (single lobe,vertebral column at center) ordiphycercal tail (single lobe andvertebral column turns dorsally)

No spiracle

Teleosts

caudalfin

dorsal fin

pectoral fin(one of two)pelvic fin

(one of two)

anal fin

muscle segmentsfin supports

brain

olfactorybulbheart

livergallbladder

stomachintestineswim bladder

kidneyanusurinary

bladder

Sarcopterygii Lobed-finned fishes Bony and fleshy lobe at the base of their paired fins With internal nares that open into oropharyngeal cavity Gill slits covered with operculum Give rise to the ancestors of tetrapods Some with cosmoid scales 2 major groups:

Actinistians – mostly extinct except Latimeria Rhipidistians – ancestors of amphibians Dipnoans – lungfishes

Latimeria

Coelacanth Only extant species discovered in Madagascar coast (originally

believed to be extinct for more than 65 M years) Skull and lower jaw architecture resembles of tetrapods

(powerful jaw suspension) Predatory

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Dipnoans “True” lungfishes Only 3 living genera Non-functional gills Undergo aestivation

during dry season Similarity with

amphibians: Swim bladder connected to

pharynx Swim bladder supplied with

blood via 6th aortic archinstead of dorsal aorta

Larvae with external gillslits

Presence of internal nares

Origin of tetrapod limbs

Class Amphibia Start of tetrapods Anthracosaurs – ancestors of amniotes (mississippian

to triassic period) Cold blooded; Can live both in land and water With lungs; can respire thru skin, mouth, pharynx,

lungs

Subclasses:Labyrinthodontia- Stegocephali – 1st tetrapodsLepospondyli -Lissamphibiaa

LissamphibiansOrder: Anura

(tailless) Frogs (elongated

urostyle)

Order: Urodela(Tailed) Salamander

(perenibranchiate (retainlarval gills); neotenous

Order: Apoda(Legless) Caecilians (borrow-

dwelling; short tail;~30cm long)

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Class Reptilia Cold blooded (aquatic,

terrestrial) Scaly; with claws Breathe thru lungs Developed long neck

(cervical vertebrae) Pelvic girdle articulates

with 2 sacral vertebrae Internal fertilization Paired limbs usually

pentadactyl Heart with right and left

atria Cotylosaurs = stem

reptiles

Class Reptilia Subclasses (based on type of skull)

Anapsida Absence of temporal arch Cotylosaurs, turtles (chelonia) LepidosauriaWith 2 temporal fossae; Powerful jaw suspension Sphenodon sp. or tuatara

Archosaurs Diapsid skull (2 temporal arches); Extinct Thecodonts (dinosaurs, crocodiles and alligators)

Class Reptilia Subclasses (based on type of skull)

EuryapsidsWith single dorsal temporal fossae; modification of diapsids Descendants of birds (plesiosaurs, ichthyosaurs)

SynapsidsWith single lateral temporal fossae; descendants ofmammals Heterodont dentition; dentary bone as the largest bone ofthe lower jaw Therapsids

Order Chelonia Cyclenis amboinensis (land

turtle) Jaws lacks teeth Covered with hard horny

beaksTortoise

Enormous size Large head shields Limbs modified into

swimming flippers Chelonia sp. (sea turtle) Gopherus sp. (desert turtle) Eretmochelis inbricata

(hawksbill turtle)

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Order Squamata Represent the most recent reptiles

Suborder Lacertilia (Lizards) 2 pairs of pentadactyl limbs Upper and lower eyelids Nictitating membrane Hemiphyllodactylus sp. (Houselizard)

Expanded digits for climbingwalls and trees

Gecko gecko (tree lizard) Nocturnal; eyes are large,

pupils vertical Eyelids are lost Adhesive toe pads Capable of loud vocalization

Varanus sp. (Giant or monitorlizard)

Large lizard with tail longerthan head and body

Draco rizalis (flying lizard) Lateral folds of the trunk

Order Squamata Suborder Ophidia (Snakes) Limbs are absent Eyelids are immovably fused Eyes are covered by transparent scales Ophidia sp. (snake) Crawl by bending into a series of S-shaped

curves Some have fangs connected to poison sacs

Cobra Long cervical ribs that can be rotated outward Has hollow non folding fangs connected to

poison sacs

hollowfang

venom gland

Order Crocodilia Modified descendants of a group of bipedal archosaurs Giants of the living reptiles Crocodylus sp. (crocodiles)

Infest rivers and lakes in tropical region Snout is narrow and pointed 4th tooth of the lower jaw is exposed when the mouth is

closed Aggressive

Alligator sp. (alligator) Most abundant in the coastal regions of the southern US Snout is broad and blunt 4th tooth of the lower jaw fits into a pit in the upper jaw Passive

The Vertebrates Agnathans

Ostracoderms Cysclostomes

Placoderms Acanthodians Chondrichthyans

Elasmobranchs Heterocephalans

Osteichthyans Actinopterygians Sarcopterygians

Amphibians Labyrinthodonts Temnospondyls Microsaurs Lissamphibians

Reptilians Anapsids Squamates Crocodilians

Avians Archeornithes Neornithes

Mammals Monotremata Marsupialia Insectivora Xenarthra Tubulidentata Pholidota Chiroptera Primates Lagomorpha Rodentia Carnivora Pinnepedia Perissodactyla Artiodactyla Hyracoidea Proboscidea Sirenia Cetacea

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Class Aves Endothermic with feathers Bipedal locomotion Scales on their beak, legs and feet Single occipital condyle and diapsid skull Reduced body weight

Slender long bones with air cavities No teeth Has a large sternal keel (carina) for

attachment of massive flight muscle Presence of air sacs Reduced wrist bones, palm digits Fusion of bones (synsacrum) Absence of urinary bladder

Uropygial gland Forelimbs for flying Has a crop for storage of seeds and grain Stomach is gizzard Females with left ovary and left oviduct

only External incubation

Archeornithes Subclass:

Archeonithes(Archeopteryx sp)oldest known birdhad a long reptilian

tailthecodont teeth on

both jawsForward nostrilsSkull was more

reptilian than avianabsence of beaksunfused synsacrumhad smaller wings

Neornithes Subclass: Neornithes (Modern Birds)Superorder: Odontognathae (with

teeth)Superorder Neognathae (without teeth) Ratites - can’t fly Carinates – can fly

Class Mammalia with mammary gland (except

monotremes) with hairs Synapsid skull 1 dentary bone articulating with

squamosal bone 3 middle ear bones With diaphragm (separates

thoracic from abdominal cavities Sweat glands Absence of cloaca (except

oviparous mammals) Heterodont dentition 2 sets of teeth Biconcave, non-nucleated RBC Ear with pinna Specialized voice box Developed cerebral cortex

Major Divisions:OviparousProtheria (monotremes) lays egg and with cloaca

ViviparousMetatheria (marsupials) yolk sac as placenta

Eutheria (placentals) with chorioallantoicplacenta

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Mammalian Orders1. Monotremata2. Marsupialia3. Insectivora4. Xenarthra5. Tubulidentata6. Pholidota7. Chiroptera8. Primates9. Lagomorpha10. Rodentia11. Carnivora12. Pinnepedia13. Perissodactyla14. Artiodactyla15. Hyracoidea16. Proboscidea17. Sirenia18. Cetacea

MonotremesPlatypus (ductbill), Echidna (spiny anteater)Lay eggsAbsence of nipples (modified sweat glands sucked by

youngs)With cloacaTestes within abdomen (absence of scrotal sac)No pinna of ear

MarsupialiaYolk sac serve as placentaYoung nursed in marsupiumGeographically isolated in

AustraliaEx. Kangaroo, koala, wallaby,

opossum, phalanger,Tasmanian wolf

InsectivoraSubsist on insectsPlantigrade (flat footed)Absence of scrotal sacWith shallow cloacaSharp, pointed teeth

with incisorsPremolars poorly

developed

Albino hedgehoghedgehog

Moles

Tree shrew

shrew

Mole

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ChiropteraAbility to flyPresence of patagiumHindlimb digits with claws

(clinging)With keel (sternum)With pinnaSanguinivorous

PrimatesPrimarily arboreal mammalsGrasping handOpposable thumbPresence of nails (instead of

claws)Large cerebral hemisphereDuplex uterusOne pair of nipples (thoracic

region)PlantigradeHigher primates:

Platyrrhine – nostrils openon sidesCatarrhines – nostrils open

anteriorly

CarnivoraFlesh eatersTerrestrialLong sharp

caninesPowerful jawsFeet with tori

PinnipediaMarine flesh-eatersNo pinna of earsWith flippersAnadromous organisms

walrus

Sea Lion

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CetaceaAquatic marine mammalsWith tail fin similar to fishes (2

lobes)With flippersOne nostril (dorsal side)Ex. Dolphin, whale, porpoise

EdentataAdvance insectivorousToothlessArmored mammals (bony

plates)Can roll into a ball (defense

mechanism)NocturnalEx. armadillos

Peba(9-banded armadillo)

TubulidentataColumnar teeth

with tube-like pulpcavityanteatersLast surviving

ancient line ofhoofed mammalsDerived from

ancestral ungulatelineageDigitigradeEx. Aadvark

Pholidota Toothless scaly anteatersOverlapping horn scales Ventral and inside extremities have

exposed skin with hairsManus and pes with long curved

claws Skull is conical without a

zygomatic arch. Jaw muscles are weak. Tongue sticky & long, vermiform,

connected to long xiphisternumprocess of sternum

Muscular stomach wall.Grinding of food assisted by

pebbles (similar to gizzard ofbirds)

Pangolin

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RodentiaLargest group of

mammalsA pair of long curved

incisors (knawing)No caninesWith diastemaCan digest cellulose

(due to commensals)With long coiled

caecumCellulose eatersPlantigrade gaitClawed feetEx. mouse, hamster,

guinea pig, squirrel

LagomorphaHerbivores2 pairs of incisors (on

upper jaw)Split upper lipStrong hind legsEx. Rabbits, hares, pikas

PerissodactylaUnguligrades (walks on the

hoofed tips of 1 or 3 or 4 toes)most of the body weight is

borne in a single digithas a mexasonic foot – walk on

single digit (rhino and horses)Ex. horses, tapirs and

rhinoceros, zebras

ArtiodactylaUngulates (walk using 2

toes – paraxonic foot)Most diverseChambered stomach (at

least 3)Ruminants (chew cud)Ex. pigs,

hippopotamuses, cattles,camels, peccary, deer,antelopes, giraffe

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ProboscideaWith proboscisIncisor form tusksScanty hair on thick,

wrinkled skin5 toes ending hoof-like

nailsMolar are grindersBulky animalSubungulatesEx. elephants and

mastodons

Hyracoidea Hunchback when at rest Harelip Plantigrade 4 digits on forefeet and 3 digits on

the hind feetWith small flat hoofs (except 1 digit) Crowned teeth (similar to

ungulates) Ex. Hyrax

SireniaFreshwater or marineStrictly vegetariansFew hairsPaddle-like forelimbsHindlimb absent

(vestiges presentinternally – attachedpelvic girdle)Naked skinVestigial nails on

flippers (manatee)Ex. Manatees,

dugongs (sea cows)