Archosaur PRINT

8/6/2019 Archosaur PRINT

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Behold the Archosauria(archon [ruling] + sauros [lizard])

Mammalia Testudines Rhynchocephalia IguaniaCrocodylia Aves

[ --------------------------------------- Reptilia ------------------------------------------------------------------------------------------------- ]

[ ------------------------------------------- Amniota ----------------------------------------------------------------------------------------------------------- ]

[ -------- Archosauria---- ] [ ------------ Lepidosauria ------------------------------------------------------------------ ]

shell made of bony plates

ribs + (most of) backbone

fused to carapace

scapula within ribcage

amniotic egg (extra embryonic membranes: amnion, chorion, allantois)

keratin in skin

Gekkota Scincomorpha Varanidae Serpentes

[ -------Varanoidea ----- ]

[ ------------------ Scleroglossa ---------------------------- ]

[ ---------------- Squamata ------------------------------------------------- ]

caudal autotomy, simple male hemipenes

well developed male hemipenes

cloacal scent

glands

antorbital fenestrae

Synapomorphy: antorbital fenestrae (holes in the skull before the eyes)


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Crocodylia: Remnants of greatness (relics: only 23 species left today)

at least 240-230 my old, earliest forms may have been terrestrial survived the Cretaceous-Tertiary extinction (65 mya) and radiated into terrestrial + marine/

freshwater ecosystems

experienced their own mass extinction towards the end of the Eocene (~ 38 mya) pushed back towards the tropics in advance of cooling temperatures leading up to the

Pleistocene Ice Age

Who are they?

gharial(1 species)

alligators, caimans(8 species)

crocodiles(14 species)

about half the species have some

marine tolerance (e.g., the Indo-

Pacific croc: salt glands on tongue)

only 1 species has marine

tolerance (American

alligator)

This tree only shows the relationships among the extant (living) crocodylians.

There are at least 47 extinct species in this group, many of which were marine, so

it makes it difficult to determine what the ancestral habitat was like


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What makes them special? Generalized reptilian head:

external nares (nostrils)at tip of snout

internal nares open into roof of mouth

trachea or windpipe(opening at back of

mouth, except in snakes)

In crocodylians however:

Snout is elongated

External nares (nostrils) are moved from the tip of the snout to the dorsal

surface of the snout. They are also elevated on the snout.

Internal nares (choana) open at the back of the mouth

The bones of the skull are modified to form a complete secondary palate (bones

are enlarged and fused to make the roof of the mouth completely bony)

Internal nares


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A large fleshy flap from the tongue and secondary palate forms a valve at the back

of the throat. When closed, this valve completely seals the mouth from the trachea

and esophagus in the throat. Advantage: crocodilians can breathe with their mouth

closed, mouth open under water (as long as the nostrils are above water) and/or

mouth full of food!

Generalized crocodylian head:

nostril moved to the dorsal

surface of snout and elevated

internal nares moved back, open behind palatal valve

trachea

greatly elongated snout

restructuring of skull and upper jaw bones

to form a complete secondary palate

fleshy folds at back of palate and tonguemeet to form a big valve (palatal valve) at back of mouth

passage from external to internal nostrils is surrounded by bone, including the secondary

palate - forms a channel for air flow from nostrils to back of mouth


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Efficient ambush predators

Excellent vision (tapetum lucidum behind retina + large pupil gives themvisual acuity comparable to an owl),hearing, sense of smell

stealth and surprise launch via powerful tail

jaws have a weak opening force (small muscle) but extremely powerfulclosing (crushing bite)

grab-gulp or grab-drown-twirl

Social animals(havent seen this for awhile), crocodylians generally hang outtogether in basking areas. At least three species (e.g., the Nile crocodile) may

hunt cooperatively


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Extremely complex behavioural repertoires using vocal (very sophisticated),

visual, chemical, and tactile cues

Courting like crocodylians: internal fertilization, oviparous, polygamous

courtship is prolonged, beginning with

male-male struggles for territories and dominance (head ramming),

followed by male-female roaring and other vocalizations, head and nose rubbing

(chemosensory, tactile), bubbling

Gentle parents

All crocodylians have extensive care of the eggs and babies

In general it is only the female who provides the care (exceptions include the

Nile and mugger crocs which display biparental care).

Females build extensive nests of vegetation, dig holes in the sand/mud (prolonged

exposure below 27oC and above 34oC kills embryos)


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Babies: vocalize while still in the eggs, heard by other nestlings, mother vocalizes

back, mother helps the babies hatch, precocial young can feed themselves. Babies

stay together in crches, in some species (such as the American alligator) the

young remain with mother for several years

Status: 2 lower risk (conservation dependent) + 3 vulnerable + 1 endangered + 6

critically endangered

Great Web Siteswww.flmnh.ufl.edu/cnhc/csl.html

for vocalizations: www.flmnh.ufl.edu/cnhc/croccomm.html


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Behold the birds . somewhere in here

e.g., VelociraptorMicroraptor

Dromaeosaurus

feathers originated at least here (areprobably older): feathers evolved longbefore modern birds [Aves] appeared

Sauropodomorpha

[ ----------------------------------------------------- Theropoda --------------------------------------------------- ]

e.g., Triceratops

e.g.,Tyrannosaurus

e.g.,Oviraptor

e.g.,Diplodocus,Titanosaurus (big

herbivores)

Ornithischia Avialae

[ ---------------------------------------------------------------- Dinosauria --------------------------------------------------------------------------------- ]

e.g.,Allosaurus

You do NOT have to know these trees. I only include them to give you a sense of avian origins.

You do need to know synapomorphies hallux [Avialae] and no teeth on maxilla [Aves].

ostriches,

emus

ducks, chickens,

turkeysArchaeopteryx

[ ------------- Avialae ----------------------------------------------------------------------------------------------- ]

[ ------------- Aves ------------------------------------- ]

V V V VV the rest

no teeth on maxilla

opposable big toe (hallux)


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Feathers !!!

Feathers are about 90% -keratin, which is stronger, more flexible, and lighter than

the keratin in scales, beak and claws

Feathers are much older than modern birds they originated somewhere in themiddle of dinosaur evolution

Incredible variation in feather modifications: structure (size, shape, length),

colour

Keeping feathers clean:

preen gland: found at the base of the tail, produces waxy esters, which protect

feathers from, water, dirt, UV radiation, parasites

Feathers are estimated to serve > 20 different functions in birds as a whole

thermal insulation (downy feathers, trap air) physical protection (thin skin)

tactile sensation (e.g., detect air currents) visual (e.g., signaling to conspecifics, camouflage)

flight water repellency

sound production (courtship) toxicity !! (only a few species, defensive)

Fully formed feathers are thus not made of living cells, so . there is no great

trauma when these feathers are periodically shed during molting


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Avian Sex

all have internal fertilization, but all are oviparous (egg-laying) females usually only have one functional ovary (the left one)

The following depicts the sequence of egg formation from ovulation at point 1 to

egg laying at point 7:

3. Magnum:albumen added

4. Isthmus: Shellmembranes added

5. Uterus: water and salts added,followed by the calcareous outer

shell

6. Egg moves into cloaca,development stops

7. Egg is laid, development begins againonce incubation starts

1. Ovary: Ovulation (eggcontains yolk + blastodisc)

vestigial rightoviduct

largeintestine

kidney

2. Infundibulum: Chalazae (thick

protein coils) added. Fertilizationoccurs (cleavage begins)

anus


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egg production is costly to the female (e.g., wood ducks use 88% of fat stores, red-billed queleas use protein from their major flight muscles), calcium is crucial


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Only basal birds have a penis (e.g., ostriches, ducks).

In other birds, sperm is transferred via the cloacal kiss

Courtship: Birds have a profusion, abundance, plentitude, and cornucopia ofcourtship displays: both vocal and visual (behaviours, colours)

courtship dances courtship feeding and grooming


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Mating Systems

a very small # of promiscuous species (e.g., hummingbirds)

a small # of polygynous species: leks or harem-holders(e.g., grouse, prairie chickens) (e.g. red wing blackbirds, eastern meadowlarks)

a small # of polyandrous species(e.g., jacanas, red phalaropes)


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Most avian species are classified as monogamous (about 90%); however, recent

studies using genetic fingerprinting have shown that about 90% of the so-called

monogamous species show some degree of extra pair copulation.

All species build nests, although this varies from simply clearing a spot in the sand

or on a rock ledge to the complex nests of weaverbirds


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All birds provide extensive care of the eggs and babies (Female only, biparental,

male only**). Babies vocalize while still in the eggs (remember crocs)

Precocial chicks: (30-40% of egg is yolk) chicks can feed themselves but still

need guarding (like crocs), downy, eyes open, run about (e.g., ducks, geese, chickens,swans, ostriches)

Altricial chicks:(15-27% of egg yolk) need feeding and extensive care (usually,

but not always) hatch naked, blind, and immobile (e.g., songbirds, raptors, gulls, crows,pigeons, etc.).

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Archosaur PRINT