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207 Cards in this Set
- Front
- Back
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Integumentary System
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skin and its derivatives (hair, scales, horns)
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Integumentary System Functions
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protection, sensory, respiration, temperature regulation, electrolyte balance, food storage, nourishment for young, locomotion
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Epidermis Layers
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stratum corneum
stratum lucidum stratum granulosum stratum germinativum |
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Epidermis
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a continuous layer of epithelial cells
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Epidermis nutrition
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-has no blood vessels
-dependent on underlying dermis for nutrition |
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Keratinization
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-process seen in amniotes
-includes flattening, loss of nuclei, thickening of the cell membrane, cells die and are sloughed off at times (called desquamation) |
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Dermis Layers
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papillary layer
fibrous reticular region subcutaneous layer |
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Fibrous Reticular Region
Other Name |
Corium - because the "skin" (leather) is made from this layer
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Dermis Contents
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-small blood vessels
-nerve endings -sweat glands -sebaceous glands -pigment cells |
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Dermis Composition
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collagen and elastin fibers in a gel-like matrix
-panniculus adiposus: fatty tissue -panniculus carnosus: muscle tissue |
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Dermis Composition
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collagen and elastin fibers in a gel-like matrix
-panniculus adiposus: fatty tissue -panniculus carnosus: muscle tissue |
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Epidermal Derivatives
Beaks |
thickened epidermis covering the jaws
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Epidermal Derivatives
Epidermal Scales |
embryological outpushing of epidermis containing a small papilla of mesodermal tissue, connected by narrow zones of uncornified epidermis
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Epidermal Derivatives
Feathers |
a derivatives of the stratum corneum
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Epidermal Derivatives
Feathers General |
-do not cover the body
-lie in tracts called pterylae -featherless areas are apteria |
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Epidermal Derivatives
Feathers Types |
-down (plumules)
-filoplumes -contour feathers (flight feathers) |
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Contour Feathers
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-divided into remiges (wings) and retrices (tail)
-larger and made of several components |
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Contour Feather Components
Quill |
inserts into the skin
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Contour Feather Components
Shaft (rachis) |
main support bean for feather
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Contour Feather Components
Aftershaft |
a small secondary feather located near the plume base of some feathers
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Contour Feather Components
Barb |
the small lines that extend from the shaft to make the vane of the feather
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Contour Feather Components
Barbule |
smaller hook-like offshoots from the barb that holds barbs together
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Contour Feather Components
Follicle |
the area in the skin from which the feather grows
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Contour Feather Components
Vane |
the collection of barbs that provide a wind resistant surface for flight
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Epidermal Derivatives
Hair |
strictly mammalian, purely epidermal in origin
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Epidermal Derivatives
Lanugo |
-downy coat of hair on a fetus
-lost just before or just after birth |
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Parts of Hair
Shaft |
above skin
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Parts of Hair
Root |
within skin
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Parts of Hair
Hair Follicle |
pit sunk in dermis
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Parts of Hair
Bulb |
hollow structure surrounding dermal papilla
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Parts of Hair
Dermal Papilla |
contains connective tissue, blood vessels
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Cross-Section of Hair
Cuticle |
outside, it is a pattern of scales
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Cross-Section of Hair
Cortex |
layer inside cuticle
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Cross-Section of Hair
Medulla |
inner layer, pigment is usually found there
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Epidermal Derivatives
Claws, Nails, Hooves |
highly keratinized structures at tips of digits in amniotes
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Epidermal Derivatives
Claws, Nails, Hooves Unguis |
the harder upper portion of a nail or claw
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Epidermal Derivatives
Claws, Nails, Hooves Subunguis |
the softer under portion of a nail or claw
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Epidermal Derivatives
Horns, Horn-like Structures, Antlers True Horn |
-Cattle
-never shed, made of a bony core and an epidermal sheath |
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Epidermal Derivatives
Horns, Horn-like Structures, Antlers Pronghorn |
-found in the pronghorn, which is not an antelope
-a true horn whose bony core is never shed, but the epidermal sheath is shed |
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Epidermal Derivatives
Horns, Horn-like Structures, Antlers Giraffe Horn |
bony core is covered by living skin
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Epidermal Derivatives
Horns, Horn-like Structures, Antlers Antler |
-deer
-bony core grows anew each year -velvet is the skin |
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Epidermal Derivatives
Horns, Horn-like Structures, Antlers Rhinohorn |
-rhino
-agglutinated hair-like filaments -always grows -never shed |
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Skin Glands
Fishes |
mucous and poison glands
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Skin Glands
Amphibians |
granular glands (poison) and mucous glands
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Skin Glands
Birds |
preen glands, but not much else
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Skin Glands
Mammals Sebaceous Glands |
-oil
-lanolin, used as a base for cosmetics, comes from sebaceous secretions of sheep |
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Skin Glands
Mammals Sweat Glands |
cool the body
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Skin Glands
Mammals Mammary Glands |
produce milk for babies
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Other Cornified Structures of the Skin
Baleen |
whales that filter plankton (krill)
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Other Cornified Structures of the Skin
Rattles |
on tails of rattlesnakes
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Other Cornified Structures of the Skin
Combs |
some birds, such as chickens
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Where was dermis first present?
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as bony scales or plates in Ostracoderms
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How did dermis evolve?
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gradual trend toward reduction of dermal bone and development of fibrous, leathery dermis
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Dermal Scales
Cosmoid Scale |
-Sarcopterygians
-primative bony scale made of several layers |
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Dermal Scales
Cosmoid Scale Layers |
top: single enamel layer
second: cosmine layer third: spongy bone fourth: lamellar bone |
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Dermal Scales
Cosmoid Scale Layer: Cosmine Layer |
-type of dentine
-has branching canals |
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What do the first two layers of the Cosmoid Scale lead to?
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evolution of teeth
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Dermal Scales
Ganoid Scale |
-most primative of extant forms
-several shiny, hard layers of ganoine are present -found in gars |
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Dermal Scales
Cycloid and Ctenoid Scales |
-Cteni = teeth
-found in most teleosts -consists of thin layers of bone imbedded in dermis and covered by a layer of epidermis |
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Dermal Scales
Placoid Scale |
-found in Chondrichthyes
-homologous to the vertebrate tooth -inner layer of hard, mesodermal dentine -outer layer is a epidermal enamel layer forming a "spine" |
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Skeletal System
Primary Function |
biomechanics - provides motion and support
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Skeletal System
Secondary Functions |
-protection of internal organs
-mineral homeostasis -hemapoiesis (production of blood cells) |
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Tissue Components
Notochord |
from endoderm
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Tissue Components
Connective Tissue, Cartilage, Bone |
formed from mesodermal mesenchyme
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Collagen
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-proteinaceous fiber synthesized by fibroblasts
-bundles form framework for connective tissue and network on which minerals are deposited for bone and cartilage |
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Loose Connective Tissue
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-small branching reticular fibers and collagen fibers
-makes up framework for organs -binds muscle fibers together -holds muscle to skin |
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Dense Connective Tissue
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-collagen fibers and elastin fibers
-makes up tendons and ligaments |
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Tendons
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-muscle to bone attachment
-long parallel bundles |
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Ligaments
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-bone to bone attachment
-a less regular arrangement of collagen fibers |
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Cartilage
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-formed within a matrix of collagen fibers
-living cells lie in lacunae -chondrocytes are derived from chondroblasts -chondrocytes lay down the intercellular matrix of sulfonated mucopolysaccharides |
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hyaline cartilage
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found at articular surfaces of bones at the joints
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fibrocartilage
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intervertebral discs, attachment of ligaments to bones
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elastic cartilage
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pinnae of ear
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calcified cartilage
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jaws of sharks
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evolutionary trend
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reduction in the amount of cartilage and specialization of whats left
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bone
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made of hydroxyapatite crystals with intercellular matrix deposited by osteoblast cells
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osteocytes
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trapped in the lacunae
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lacunae
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connected by lacunae
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Spongy Bone
Trabeculae |
probide strength at areas of greatest stress
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Spongy Bone
Marrow |
yellow-much adipose tissue
red- highly vascularized, hemopoietic tissues |
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Bone Development (Ossification)
Blastema |
aggregation of mesenchymal cells that differentiate into muscle, bone, or cartilage depending on the stimulus
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Bone Development (Ossification)
Membrane Bone |
-bone formed directly from membranous blastema with no cartilage precursor
example-lower jaw, parts of the skul, vertebrae of salamanders and caecilians |
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Bone Development (Ossification)
Membrane Bone Dermal Bone |
histologically membrane bone which is ontologically derived from the dermis
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Bone Development (Ossification)
Membrane Bone Endochondral Bone |
-bone formed where hyaline cartilage already exists
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Long Bones
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-Endochondral Bone
-the shaft is is diaphysis -periosteal bone grows outside the diaphysis |
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Joint
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where two bones meet
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Joint types
Diarthrosis |
-movable joints
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Joint Types
Diarthrosis Includes: |
-joint capsule - encloses the cavity around the joint
-synovial fluid - lubricates the joint and nourishes the cartilage -synovial membrane - line the capsule |
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Joint Types
Synarthrosis |
sutures, such as in the skull
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Joint Types
Ankylosis |
fusions, also found in the skull
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Heterotopic Bones
Sesamoid Bones |
found at friction points, fibrous connective tissue
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True Heterotopic Bones
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-just embedded in tissue
example: baculum (penis bone found in some mammals), os clitoridus (female homology of baculum) |
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dermal
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developed in dermal skin, no precartilage
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endoskeleton
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usuallly preformed in cartilage, deeper lying
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visceral skeleton
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branchial (pharyngeal) skeleton and derivatives such as ear ossicles, jaws, hyoid, and visceral arches
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somatic skeleton
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remaining internal skeletal structures
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axial skeleton
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-postpharyngeal axial: vertebrae, ribs, trunk, and tail
-cranial: skull (part visceral, part dermal, part somatic) |
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appendicular skeleton
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limb girdles and limbs
(free appendages) |
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Function of the Postpharyngeal Axial Skeleton
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1) compression struct in fishes - movement
2) suspension of body mass and transfer of weight to girdles an appendages; in tetrapods, protection of visceral organs and spinal cord and rigid support; lung ventilation in amniotes |
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What does the shape of the centrum reflect?
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the nature of movement between adjacent centra and the amount of support the vertebral column must provide
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zygopophysis
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articular surfaces between vertebrae
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Vertebral Development
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-in connective tissue, septa between myotomes (embryonic muscle segments)
-from mesenchyme of schlerotome origins -arches form first as cartilagenous plates |
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Vertebral Development
Centrum |
centra form by:
-chondrification (cartilagenous fishes) -ossification of cells that invade the notochord (most amniotes) -perichondrial deposition (bony fishes) |
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Evolution of Axial Skeletal System
Fishes |
-for motion and buoyancy
-vertebral column --> -resists compression of body -converts contractions of longitudinal muscles into lateral undulations |
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Fishes use what type of locomotion?
(figure in notes) |
-anguilliform (eel-like) locomotion: like skating\
using alternating waves of contraction |
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Buoyancy
depends on tail shape |
Heteroceral - sharks, heavy-bodied fishes without lungs or air bladders
Homocercal - most other fishes |
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Evolution of Axial Skeletal System
Amphibians |
axial skeleton is a support beam to resist bending in the vertical plane (belly doesn't drag)
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Labyrinthodonts
(ancestral amphibians, a step up from Rhipidistian Crossopterygians) have: |
rachitomous vertebrae, including an intercentrum and a pair of pleurocentra
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Rachitomous vertebrae evolved into several other forms:
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-stereospondylous vertebrae
-embolomerous vertebrae -amniote vertebrae |
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Stereospondylous Vertebrae
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intercentrum enlarged and became the sole component of the centrum; pleurocentrum disappeared
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Embolomerous Vertebrae
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found in a sideline of labyrinthodont evolution; pleurocentra enlarge and fuse to the enlarged intercentrum
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Amniote Vertebrae
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pleurocentra enlarged greatly; intercentrum greatly reduced or completely lost
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Amphibian vertebrae show the beginnings of regional specialization
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1) single cervial vertebra (like Necturus)
2) trunk vertebrae 3) single sacral vertebra which articulates with the pelvic girdle 4) caudal vertebrae |
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Frog specialization
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shortened vertebral column
urostyle - fused caudal vertebrae |
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Evolution of Axial Skeletal System
Reptiles |
1)intercentrum completely lost; centrum enlarged and composed of fused pleurocentra
2) more cervical vertebrae including atlas and axis (lizard head movement) 3)at least 2 sacral vertebrae 4)caudal vertebrae variable |
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Evolution of Axial Skeletal System
Reptiles Ribs |
-costal cartilages found in the septa between muscle segment become ossified, usuallly only in the thoracic region
-gastralia: abdominal ribs found in the ventral abdominal wall of some reptiles |
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Evolution of Axial Skeletal System
Birds |
Modifications primarily for flight and bipedal walking
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Evolution of Axial Skeletal System
Birds (5 changes) |
1)long, flexible neck (heterocoelous vertebrae)
2)trunk - acts as a fulcrum 3)synsacrum - fused trunk and sacral vertebrae 4) 6-7 caudal vertebrae movable, but last 4-7 are fused into a pygostyle 5) sternum has a large keel for flight muscle attachment |
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Evolution of Axial Skeletal System
Mammals |
1) most have 7 cervical vertebrae, atlas and axis are highly specialized
2)trunk region - subdivided 3)sacral region - 3 or more fused vertebrae to form the sacrum 4) caudal - vertebrae vary greatly in number |
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Evolution of Axial Skeletal System
Mammals Trunk Subdivision |
thoracic - 12-15 vertebrae, bear ribs
lumbar region - 4-7 vertebrae, have pleuropophysis (the rib component of the transverse process) |
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Evolution of Axial Skeletal System
Mammals Specialized Caudal Vertebrae |
coccyx - modified caudal vertebrae in humans
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Appendicular Skeleton
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skeletal elements supporting paired appendages and girdles
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Origin of the Appendicular Skeleton
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there was no appendicular skeleton in Ostracoderms or in modern agnathans
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Origin of the Appendicular Skeleton Theories 1
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modified gills - girdles come from gill arches
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Origin of the Appendicular Skeleton Theories 2
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fin-fold theory - continuous lateral folds on each side of trunk (such as metapleural folds in Amphioxus)
(most acceptable theory, based in part on Hox genes) |
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Origin of the Appendicular Skeleton Theories 3
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spine fin theory - spiny sharks with rows of lateral fins supported by spines
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Evolutionary Development of Appendicular Skeleton
Arthrodires |
a group of Placoderms with pectoral spines associated with pectoral fins
1) had dermal plates comparable to dermal elements of pectoral girdle 2)Scapulocoracoid cartilage |
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Scapulocoracoid cartilage
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a U-shaped girdle of one piece, serves as attachment surface for pectoral fins, and is the endoskeletal portion of the pectoral girdle
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Evolutionary Development of Appendicular Skeleton
Fossil Sharks |
had broad based fins supported by cartilageous pterygiophores
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Evolutionary Development of Appendicular Skeleton
Modern Sharks |
- narrow based fins
-reduction in the number of pterygiophores (basal pterygiophores: 3 in front -pectoral, 2 in back - pelvic) -radial pterygiophores extend outward from basal ones |
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Evolutionary Development of Appendicular Skeleton
Acanthodians ("spiny sharks") |
-had rows of lateral fins supported by a large spine at the anterior edge of each fin, crude pectoral girdle associated with first spine
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Evolutionary Development of Appendicular Skeleton
Actinopterygians "modern ray-finned fishes" |
-narrow based fins
-proximally, 3 basal pterygiophores -distally, bony fin rays (lepidotrichia - evolved from rows of bony scales) -pectoral girdle -pelvic girdle is a small cartilagenous rod |
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Actinopterygian
pectoral girdle |
endoskeleton portion small, usually not ossified
dermal portion large: -cleithrum large, scapulocoracoid attaches to it -clavicle small -post-temporal bone anchors pectoral girdle to back of skull |
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Actinopterygian
pelvic girdle |
small cartilagenous rod does not articulate with the vertebral column because the body is supported by water, not limbs
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Evolutionary Development of Appendicular Skeleton
Tetrapods |
have jointed limbs which support body weight and articulate to allow rotation
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Evolutionary Development of
Appendicular Skeleton Tetrapods early Labyrinthodonts (See Figure) |
(primative amphibians) show the three distinct segments in the Chiropterygium (hand wing or fin)
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Evolutionary Development of Appendicular Skeleton
Tetrapods Labyrinthodonts Pectoral Girdle |
-dermal portion reduced
-cleithrum and clavicle still present -post-temporal gone (head can move independently) -endoskeleton portion enlarged, scapulocoracoid ossified as a single element |
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Evolutionary Development of Appendicular Skeleton
Tetrapods Labyrinthodonts Pelvic Girdle |
-generally enlarged
-ilium: extended dorsally, articulated with sacral rib -pubis and ischium: ventrally expanded -pubic symphysis: strengthened the girdle |
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Requirements to shift from Crossopterygian girdles and limbs to Labyrinthodont girdles and limbs
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-loss of elements connecting pectoral girdle to skull
-expansion of scapulocoracoid -expansion of pelvic girdle and attachment to vertebral column |
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Evolutionary Development of Appendicular Skeleton
Trends in Modern Vertebrate Limbs of Modern Amphibians and Reptiles |
more slender
reduction in number of tarsals and carpals |
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Evolutionary Development of Appendicular Skeleton
Trends in Modern Vertebrate Girdles in Modern Amphibians and Reptiles 1 |
-endoskeletal pectoral: distinct scapula and anterior coracoid
-dermal portion of the pectoral - more reduction -clavicle and interclavicle present, cleithrum gone |
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Evolutionary Development of Appendicular Skeleton
Trends in Modern Vertebrate Girdles in Modern Amphibians and Reptiles 2 |
pelvic girdle - puboischiadic fenestra between pubis and ischium (reptiles)
pubic regions do not ossify in amphibians |
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Pterosaur wings
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skin membrane supported by an elongated fourth phalange
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Bat wings
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skin membrane supported by greatly elongated 2, 3, 4, and 5th phalanges
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Bird wings
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arm and modified hand with feathers
han consists of three modified digits, two distinct carpals remain, and other carpals and metacarpals have fused to form the carpometacarpus |
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Pectoral Girdle of Birds
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-scapula reduced
-clavicles and interclavicle fuse to form furculum (wishbone) -greatly enlarged keel on sternum for attachment of flight muscles -anterior coracoid remains |
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Pelvic Girdle of Birds
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-pubis is rotated in a caudal direction
-all bones are firmly fused -ilium greatly elongated and fused with synsacrum -midventral pelvic symphysis gone, enlarging pelvic canal (for eggs) |
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Mammals
First to show? |
therapsids first show rotation under the body of limbs
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Mammals Ventral Musculature
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reduced in importance
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Mammals Dorsal Musculature
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more important for swinging legs and bracing legs at girdles; therefore, dorsal portions of girdles are expanded and vental portions are reduced
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Evolution of Mammals Pectoral Girdle 1
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anterior coracoid gone
posterior coracoid in synapsids reduced to coarcoid process in mammals, where is articulates with the humerus near the glenoid cavity of the scapula |
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Evolution of Mammals Pectoral Girdle 2
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cleithrum gone
interclavicles gone in all but the Monotremes clavicle reduced or completely lost in many forms (large in humans, but small in most others) |
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Evolution of Mammals Pelvic Girdle
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pubis and ischium reduced
all elements firmly fused (ilium, ischium, and pubis to form the innominate bone) epipubic bones in monotremes and marsupials are present to provide support for the pouch (marsupium) |
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Evolution of Mammals Limbs
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-long bones become longer
-radius is main support in the forearm -tibia is main support in the shin -carpals and tarsals reduced in number -feet and hands point forward instead of outward, digits more equal in length |
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Viceral Skeleton
Splanchnocranium |
-skeleton of the pharyngeal arches, gill arches and their derivatives
-mesenchyme origin is from ectoderm rather than mesoderm |
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Basic Gill Skeleton
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agnathans - branchial basket
jawed fishes - several jointed bars along the walls of the pharynx forming arches between gill slits |
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first two gill arches are specialized as:
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1) the mandibular arch (jaw)
2)the hyoid arch (supports the tongue) |
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Shark Skull
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1) Meckel's cartilage and palatoquadrate cartilage articulate with each other and with the ventral portion of the hyomandibula
2)dorsal portion of hyomandibula is connected to the otic capsule of the cranium by ligaments |
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Jaw Suspension
Hyostylic |
jaws braced against the hyomandibula, hyomandibula braced against otic capsule of the brain case
ex. elasmobranchs and most actinopterygians |
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Jaw Suspension
Amphistylic |
jaws and hyoid arch both braced against brain case
ex. some primitive sharks |
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Jaw Suspension
Autostylic |
hyomandibula not involved in supporting jaw at all, upper portion of jaw (palatoquadrate) fused or attached immovably to braincase
ex. lungfishes, chimera, all tetrapods |
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What changed with aquisition of terriestrial modes of life?
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first and second specialized arches and following gill arches changed dramatically
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Metamorphosed amphibians and amniotes have completely lost functional gills, but gill arches are still present as:
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1) support for the tetrapod tongue
2) form special structures at the entrance to the lungs |
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Fate of Gill Arches in Tetrapods
Palatoquadrate |
ensheathed by dermal bone, part becomes primary palate and part becomes ossified as the quadrate bone (hinge of the jaw in amphibians reptiles and birds)
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What does the palatoquadrate become in mammals?
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one of the ear ossicles called the incus
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Fate of Gill Arches in Tetrapods
Meckel's Cartilage 1 |
may remain as cartilage in crocodilian and turtle mandibles
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Fate of Gill Arches in Tetrapods
Meckel's Cartilage 2 |
becomes invested by dermal bones (several), gradually reduced in number leaving only the dentary
-posterior end ossifies as articular cone in amphibians, reptiles, and birds -ossifies as the middle ear bone (malleus) in mammals |
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Fate of Gill Arches in Tetrapods
Hyomandibula |
-no longer involved in bracing jaw against brain case, so is lost (lungfishes) or modified (everybody else)
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Fate of Gill Arches in Tetrapods
Hyomandibula in Amphibians |
-lost articulation with palatoquadrate (now quadrate) and has become attached to new tympanic membrane ("eardrum")
-also abuts the otic capsule, surrounded by first pharyngeal pouch to become middle ear and first ear ossicle (columella, also called stapes in mammals) |
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The rest of the hyoid arch is incorporated into the tetrapod hyoid apparatus
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body (corpus) - derived from the basihyal of the original hyoid arch and the basibranchial cartilages of gill arch 3 (and sometimes 4)
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Entoglossal Bone
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in lizards, a greatly extended process from the body reaching into the tongue
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Horns (cornua)
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ceratohyal cartilage of original hyoid arch (anterior pair) and 3rd and 4th arches (caudal pairs)
-amphibians and reptiles have several horns -birds have one pair -mammals have two pairs |
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Hyoid Apparatus functions to :
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-anchor the tongue
-provide attachment for larynx muscles -assist in lower jaw movement -provide attachment of muscles for swallowing |
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Laryngeal Skeleton
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cricoid cartilage - from arch V
arytenoid cartilage - from V, supports vocal cords thyroid cartilage - from IV, maybe V (mammals only) |
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Primative Visceral Skeleton
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associated with feeding and branchial respiration is modified by tetrapods for use in communication
1)transmission of airborne sound (ear bones) 2)attachment of tongue muscles 3)attachment and movement of vocal cords |
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Cranial Skeleton Components
Neurocranium |
chondocranium
cartilage precursor, surrounds brain and sense organs |
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Cranial Skeleton Components
Visceral Skeleton |
pharyngeal skeleton or splanchnocranium
skeletal derivatives of gill arches |
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Cranial Skeleton Components
Dermatocranium |
portion derived from dermal bone, surrounds the other two components
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Neurocranium Development
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-of mesenchyme (sclerotomal) origin
-orderly process, similar in all vertebraes --cartilagenous rods and six sense capsules coalesce, followed by centers of ossificaiton turning the structure into bone |
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Neurocranium Development
Rods |
parachordal - rods that develop on either side fo the front of the notochord
trabeculae (prechordal) - a pair of rods located near the pituitary gland |
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Neurocranium Development
Sense Capsules |
nasal capsules (olfaction - smell)
orbital cartilages (eyes - vision) otic capsules (ears - audition) |
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Occipital Arch
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posterior fused arch forming foramen magnum (hole in skull where spinal cord and brain meet)
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Chief Centers of Ossification
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occipital, sphenoid, ethmoid, otic
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Dermatocranium
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dermal bones ensheathing toher parts of head skeleton, consists of 5 groups
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Dermatocranium
Group 1 |
Dermal Roof bones
-top of skull: frontal parietal, postparietal -edge of upper jaw: maxilla, premaxilla -circumorbital: lacrimal, prefrontal, postfrontal, jugal -temporal region: intertemoporal, supratemporal, tabular -cheek region: squasmosal, quadratojugal |
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Dermatocranium
Group 2 |
Palatal bones
-located in roof of mouth: vomer, pterygoid, palatine, ectopterygoid, epipterygoid (alisphenoid of mammals) |
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Dermatocranium
Group 3 |
Lower Jaw bones:
dentary, splenials, surangular, angular, prearticular |
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Dermatocranium
Group 4 |
Parasphenoid:
under neurocranium |
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Dermatocranium
Group 5 |
Opercular and Gular Bones:
covering branchial arches |
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Trends in Labyrinthodonts
(similar to crossopterygian ancestors) 1-3 |
1)increase in snout and jaw length
2)loss of joint near middle of neurocranium 3)many small snout bones fused |
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Trends in Labyrinthodonts
(similar to crossopterygian ancestors) 4 & 5 |
4)most of neurocranium ossified
5)opercular and gular bones lost |
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Trends in Labyrinthodonts
(similar to crossopterygian ancestors) 6 |
6)visceral skeleton modified
a)autostylic suspensorum at palatoquadrate b)hyomandibula - now auditory ossicle c)hyoid arch for tongue support |
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Trends in Extant Amphibians
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1)exceptionally broad and flat skulls
2)dermal bones lost 3)chondrocranium (neurocranium) unossified |
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Trends in Stem Reptiles
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1) skull higher, more narrow
2)external and middle ear moved lower and more caudal 3)temporal rood has no opening (fenestra) =Anapsid |
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Temporal Fenestra
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holes in the temporal region
developed in two main lines in reptilian skull evolution |
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Temporal Fenestra
Development |
-developed in areas of reduced stress where several bones come together
-provide firm attachment for jaw closing musculature -provide space for into which contracting jaw muscles could bulge |
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Temporal Fenestra Types
Anapsid |
no temporal opening although a notch sometimes occurs at the back of skull
-seen in stem reptiles and chelonians (turtles) |
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Temporal Fenestra Types
Synapsid |
one opening bordered above by postorbital and squamosal, seen in mammal-like reptiles
modified synapsid - opening merges onto braincase and into orbit, modern mammals |
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Temporal Fenestra Type
Diapsid |
two openings separated by the postorbital and squamosal (which join to form a bar)
modified diapsid: -bar between openings lost, birds -bar below lower opening lost, lizards |
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Trends in Birds
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-modified diapsid
-numerous dermal bones -skulls thin, high domed -large orbits |
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Trends in Mammals
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Changes in cranium associated with changes in sensory organs, brain size, breathing and feeding mechanisms
bones reduced by fusion and loss |
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Trends in Mammals
Otic Capsule |
greatly enlarged as inner ear becomes more complex
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Trends in Mammals
Nasal Capsules |
expanded, turbinate bones (delicate scrolls or bone supporting olfactory cells) are ossified
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Trends in Mammals
Brain Case |
completely ossified
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Trends in Mammals
Hard Palate/ Soft Palate |
secondary palata for separation of food and air passages
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Trends in Mammals
Changes in Jaw Musculature |
-enlargement of temporal fenestrae
-stronger bite, more precise jaw movement -dentary articulates directly with the squamosal |
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Trends in Mammals
Lower Jaw |
reduction in number of bones to one, the dentary
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