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Trinity Term 1 > Mesozoic World: rise of the archosaurs > Flashcards

Mesozoic World: rise of the archosaurs Flashcards

1
Q

Describe the Mesozoic Era

A
  • post-End-Permian outpouring of the Siberian Traps (252mya)
  • pre-end-Triassic Chicxulub impact (66mya).
  • “Carnian Pluvial Event” (232mya); temporarily interrupted droughts of the Triassic and released dinosaur diversification
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2
Q

Describe the Archosauria

A
  • diapsids
  • dominated the terrestrial environments of the Mesozoic
  • replaced the synapsids that had dominated the Palaeozoic
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3
Q

Describe the Mesozoic oceans

A

diapsid clades rise to dominance

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4
Q

Describe the marine diapsids of the Mesozoic

A
  • ichthyosaurs
  • plesiosaurs
  • marine turtles
  • mosasaurs
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5
Q

Describe marine mesosaurs

A

became extinct in the Permian.

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6
Q

Describe Ichthyosauria

A
  • marine diapsid
  • most specialised
  • streamlined body form
  • heterocercal tail (convergent with those of sharks)
  • viviparity
  • oxygen isotope ratios of their tooth phosphate suggest endothermy
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7
Q

Describe the Plesiosauria

A
  • specialised clade of marine diapsid, allied with several other marine clades including placodonts, nothosaurs, and pachypleurosaurs.
  • typical body form: four paddle-like fins and a long neck.
  • viviparity
  • tooth oxygen isotope ratios suggest endothermy
  • typical plesiosaur ca. 3m long
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8
Q

Describe modern turtles

A
  • ossified shell
  • upper carapace and a lower plastron
  • fused to the ribs
  • horny beak without teeth
  • regionally endothermic
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9
Q

Describe Odontochely

A
  • The Triassic turtle (sc. 220mya) - shallow marine deposits
  • full complement of teeth
  • no ossified carapace.
  • ossified plastron (lower shell evolved before the upper shell as a defense against predation from below
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10
Q

Describe the Archosauria

A
  • greatest of all the diapsid radiations
  • crocodiles, pterosaurs, dinosaurs (including birds) and relatives
  • derived four-chambered heart: adaptation to active lifestyles
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11
Q

Describe Pterosaurs

A
  • more closely related to dinosaurs than to crocodiles, together forming most of the clade Avemetatarsalia
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12
Q

Avemetatarsalia

A

all archosaurs more closely related to birds than crocodiles.

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13
Q

Describe modern crocodiles and birds

A
  • four-chambered heart
  • derived character of archosaurs
  • adaptation to active lifestyles
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14
Q

Describe the Crocodylomorpha

A
  • far greater diversity of body form than living crocodiles
  • some fully marine species
  • some highly athletic terrestrial forms varying from robust to gracile
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15
Q

List some Crocodylomorpha

A
  • Protosuchus
  • Terrestrisuch
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16
Q

Describe Protosuchus

A
  • robust
  • ~1m
  • Jurassic
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17
Q

Describe Terrestrisuchus

A
  • gracile
  • ~0.5m
  • Triassic
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18
Q

Describe the specifics of the Pterosauria

A
  • highly-specialized for flight
  • earliest known forms (Late Triassic) accomplished fliers
  • largest animals ever to fly.
  • generally diurnal
  • minority may have been at least crepuscular
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19
Q

Describe the Pterosaurian wing

A

skin membrane stretched between the hyper-elongated 4th finger of the forelimb, and the ankle area of the hindlimb

20
Q

Describe Pterosaur flight

A
  • smaller pterosaurs used flapping flight
  • largest pterosaurs glide long distances while soaring
21
Q

Describe Pterosaur locomotion

A
  • walked quadrupedally (wing membrane stretched between forelimb and hindlimb)
  • unlike that of any extant animal
  • plantigrade (“flat-footed”) hindlimb and a digitigrade forelimb (walking on the fingers to accommodate the wing)
22
Q

Describe the Pterosaur wing

A
  • cruropatagium
  • propatagium
  • cheiropatagium
  • wrist
  • steroid
  • phalanges of extended wing finger
23
Q

Describe Pterosaur reproduction

A
  • eggs are rarely preserved
  • shell parchment-like (like a snake’s)
  • some pterosaurs may have bred colonially, and may have provided care to their offspring (convergent with birds)
  • pterosaurs carried two eggs, so retained both oviducts.
24
Q

Describe Pterosaur thermoregulation

A
  • covered in pycnofibres
  • endothermic
25
Q

Describe pycnofibres

A
  • sometimes branched
  • filamentous integumentary appendages
  • melanosomes on the head crest suggests they were also used in display
26
Q

melanosomes

A

pigmented intracellular organelles

27
Q

Describe Dinosauria phylogeny

A
  • Ornithischia
  • Saurischia
28
Q

Ornithischia

A

variety of herbivorous bipeds and quadrupeds

29
Q

Saurischia

A

Sauropoda and Theropoda

30
Q

List some Ornithischia

A
  • Stegosaurus
  • Triceratops
  • Gastonia
  • Parasaurolophus
  • Maiasaura
31
Q

List some Sauropods

A
  • Mamenchisaurus (basal)
  • Brachiosaurus
32
Q

List some therapods

A
  • Allosaurus
  • Aves (birds!)
33
Q

Describe Dinosauria origins

A
  • originated in the Middle Triassic (c. 245mya)
  • ecosystems still recovering from the end-Permian mass extinction
  • Pangaea
34
Q

Pangaea

A

the continents formed the one giant land mass

35
Q

Describe Dinosauria diversification

A
  • Late Triassic, following the Carnian Pluvial Event (234-232mya)
  • climate switched from arid to humid, then back
  • Cretaceous break-up of Pangaea isolated the various groups of dinosaur in Laurasia and Gondwana: rapid allopatric speciation
  • isolated groups underwent separate, slower adaptive radiations through the rest of the Cretaceous
36
Q

Describe Dinosauria diversity at the End-Cretaceous

A

declined sharply during the last 10My

37
Q

Describe Dinosauria thermoregulation

A
  • last common ancestor of dinosaurs and pterosaurs was endothermic
  • ectothermy evolves secondarily in some Ornithischia.
  • elevated and relatively stable body temperatures inevitable at very large body size
  • long Sauropod necks + air sacs running through vertebrae may have played a role in thermoregulation
38
Q

Describe small dinosaurs

A

low growth rates, like modern lizards

39
Q

Describe large dinosaurs

A

fast growth rates, like modern precocial birds

40
Q

Describe Argentinosaurus

A
  • Sauropoda
  • 83,000kg
  • 40m
  • maximum walking speed: 2ms-1
41
Q

Describe Tyrannosaurus

A

maximum walking speed of 5ms-1

42
Q

Describe Dinosauria ventilation

A
43
Q

Describe ventilation in modern birds

A
  • lungs connected to balloon- like system of anterior and posterior air sacs
  • air sacs act as a pair of bellows, alternately storing air during one phase of the inhalation/exhalation cycle, and releasing it to the lungs during the next phase
  • unidirectional flow through the lungs
  • much more efficient in gas exchange than tidal flow
  • same in non-avian saurischian dinosaurs
44
Q

Tidal flow

A

mammalian lungs

45
Q

Describe Dinosauria reproduction

A
  • oviparous
  • carefully arranged their eggs in the nest
46
Q

Describe Saurodopomorph reproductor

A
  • coloniality
  • nest site fidelity
  • hydrothermal geyser field for incubation

Trinity Term 1 (38 decks)

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