Aves

Archaeornithes A subclass of primitive reptile-like fossil birds including archaeoptyrex

Aves Birds, a class of bipedal homoiothermic vertebrates having the body clothed in feathers and front limbs modified as wings, and the skin of the jaw forming a horny bill (beak). They are descended from the extinct archosaurian reptiles.

Barb One of the delicate threadlike structures extending from the shaft of a feather and forming the vane

Barbule Lateral projection from barb of feather, serving to hold barbs together to form an unbroken vane

Contour Feathers Outermost feathers that cover the body of birds

Down Feathers The first fluffy feathers of young brids, with a short quill and with barbules not interlocking to form a flat vane. Some birds retain a down layer under adult plumage

Filoplumes Delicate hair-like feather with long axis and a few free barbs at apex

Follicle Sheath of epithelium surrounding hair or feather root

Furcula The united clavicles of birds, the wishbone

Manus Hand, or part of forelimb corresponding to it, as present in amphibians, reptiles, and mammals

Neognathae Superorder of “new jaw”-ed birds, mainly flying

Neornathes Subclass of birds, including all extant modern birds

Paleognathae The ratites, flightless birds of the subclass Neornithes such as the kiwis, cassowaries, and strich, which are secondarily flightless

Pectoralis Breast muscle connecting breastbone with humerus, much enlarged in birds where it is a main flight muscle

Pelvic Girdle In vertebrates, a skeletal support in the hip region for attachment of hind-fins or hindlimbs, made of a hoop of cartilages or bones

Pneumatized Having air cavities

Pygostyle A compressed upturned bone at end of vertebral column in birds, composed of fused vertebrae

Quill The central shaft of a feather

Shaft Stalk of feather or hair

Sternum Breastbone in vertebrates

Supracoracoideus A flight muscle in birds, running indirectly from breast bone to humerus and responsible for raising the wing

Synsacrum Mass of fused vertebra supporting the pelvic girdle of birds

Unciate Process A hook shaped process on the lateral borders of the superior surface of vertebral bodies of the third to seventh cervical vertebrae

Vane The web of a feather, consisting of the thread-like barbs

Air Sacs Spaces filled with air and connected with lungs in birds

Avascular

Lung Organ specialized for the respiratory uptake of oxygen directly from air and release of carbon dioxide to air

Mesobronchi In birds, the main trunk of a bronchus giving rise to secondary bronchi

Parabronchi One of numerous small tubules in lungs of birds, connecting dorsobronchi and ventrobronchi, and in which respiratory gas exchange takes place

Brief Breakdown **SPECIES POINT** Archaeoptyrex ~147myo, connective link between birds & dinosaurs

o A class of both reptiles & birds

o @ caudal region, vertebra runs to the very tip (see pic farther down)

Definitive morphology: SHAPED 4 FLIGHT

Little size difference, 2g min vs 20g max

**SPECIES POINT**

Teratorn sp. [~80kg!] extinct

Flight imposes restrictions weight-

reduction & other physiological factors

Feathers ONLY IN BIRDS: defining characteristic

Contour Feathers [body & flight feathers] o Aerodynamic contour: streamlines body surface, lightweight, strong covering

o Quill (from skin follicle), Shaft (continuation of quill, supporting barbs), Barbs (arranged in

parallel, spread diagonally from shaft ASYMMETRICAL vanes), Barbules link adjacent barbs by

overlapping hooks

o Preening (running beak parallel to barb axis) reattch barbules

o Asymmetrical + can rotate slightly

o @ downstroke air resistance, @ upstroke reduced resistance

o Homologous to reptile scales little elevation first forms, then follicle

o Dev. From epidermal elevation (supplied by dermal core)

o Roll into cylinder & sink to follicle, growing the feather

Pigments added, shaft/barbs keratinize [strength]

Protective sheath splits open

o Ordered moulting [symmetrical shedding of few pairs, & grow, repeat 4 other]

o exception: WATER FOWL (shed all @ once & hide b4 regrowth]

Down Feathers [insulation] o soft tufts [barbules lack hooks] beneath contour feathers; no keratinization

o #s lifestyle/stage: breast & abdomen (of water birds); entire body (of some

juveniles)

o Water fowl (abdomen heavily covered, protect against water)

o Thermoconductivity low for down feathers (+ many air pockets)

g cal cm-2 cm-1 sec -1 C-1

Filoplumes [sensory] o hair-like, few short barbs @ end; usually below contour feathers

o many nerve endings (@ base): [comm. pos & mmt of contour feathers]

EVO

Character Similarity [to:]

o General Therapod elongate, S-shaped neck, tridactyl [3-finger] digits, hollow, pneumatic bones

o Dromeosaurs wrist-structure “hand-turning”; shoulder joints allowing arm flapping,

feathers (NOTE: SYMMETRICAL (likely for thermoreg))

o Archaeopteryx contour feathers covering body, & differentiated flight feathers (still sucked)

o Asymmetrical Vanes

o Forelimb bones non-fused (fused later in birds for power)

o Tail [long] hinders flight

Theories of flight evo [2]

o Aboreal Theory were tree-dwellers jumping between trees

selective pressure for dist & accuracy

o Terrestrial Theory dromeosaurs terrestrial, bi-pedal hunters

o Claws @ end of wing tips wings evod as traps

o Skeletal elements for flight underdeveloped refinement

for horizontal jumping& balanced landing

Skeleton [light & strong] o Bones pneumatized ( less weight, helps cool the animal)

o No tissue in marrow cavity of long bones; spaces in bones [ext. of air sacs]; thin bone

walls

Thin cross-struts stiffen bone, prevent buckling

o Forelimbs highly modified for flight

Manus [~=hand]

o Bones reduced by fusion

o Primary flight feathers provide forward thrust [attached to manus]

Forearm

o Secondary flight feathers produce LIFT [ gliding]

o Longer forearm more gliding (ex. Albatross)

Other bones

o [many]Vertebrae fused rigidity

o Synsacrum +pelvic girdle leg support

o Throcaic, lumbar, sacral, caudal vertebra

o Pygostyle reduced posterior caudal vertebrae

o Uncinate Processes ribs braced together

o Sternum has large thin keel for muscle attachment

o Furcula fused clavicles (collar bones)

Flight muscles Large to meet flight demands; attached to keel & humerus

o Pectoralis largest flight muscle, pulls wing down

o Supracoracoideus under pectoralis

o attached by tendon to upper side of humerus;

raises wing

Gas Exchange [flight ENERGETICALLY DEMANDING] NOTE: balance between weight reduction & enhancement of physiol. system

o Paired lungs [1/2 mammalian size]+ 9 (interconnected) air sacs

o Air Sacs [arr. In pairs in thorax (ant)& abdomen (post)] 2|3x Volume of mammalian

May extend into bones; AVASCULAR [no gas xch there]

o Respiration in lungs, NOT air sacs

o UNIDIRECTIONAL air flow [& cooling] facilitated by air sacs

Lungs

o Trachea [split into] 2 mesobronchi (primary), run

through lung

o secondary bronchi parabronchi

[UNIDIR flow] [in mammalian, tidal (bidir)]

o Full Turnover = 2 inhalations & 2 exhalations

o On INHALE: air to posterior air sac (some to lung) [removes existing lung air, pushing it into

anterior sacs]; on exhale: from posterior air sac parabronchi out via trachea (air

anterior air sacs also pushed out

o Dinosaurs likely used a similar method; [lungs remained unchanged in birds]

o Air sacs have no intrinsic muscle everything –ve pressure!