Lecture 18 - Reptiles and dinosaurs

Question 1

Reptiles: when did they appear, what new characteristics did they bring, where do they mainly reside in, and what are the other interesting features?

Answer 1

320 mYa

Scales, hard-shelled eggs that could contain water (offspring not needed to stay near water) and ignore the tadpole stage which is where offspring are most vulnerable

Mainly tropical areas (they are cold-blooded)

• None are solely herbivorous
• They make up 30% of terrestrial vertebrate
• Reptiles are not monophyletic
• Vertebrate group most under threat
• Almost always ectotherms

Question 2

Dinosaur clade groups after Archosauria and what they evolved into

Answer 2

Archosauria as the common ancestor:

• Crocodilia (crocodiles)

Evolved into the bird total group

Question 3

Dinosaur clade groups in the bird total group and what they evolved into

Answer 3

Bird total-group:

• Aphanosauria
• Pterosauria (dimorphodon, pteranodon etc)
• Lagerpetidae
• Silesauridae

Evolved into dinosauria

Question 4

Dinosaur clade groups in the dinosaur group and what they evolved into

Answer 4

Dinosauria:

Ornithischia (triceratops, ankylo, iguanodon etc)
Sauropodomorpha (Apatsaur, isisaur, amargasaur)

Evolved into theropoda

Question 5

Dinosaur clade groups in the Theropoda group and what they evolved into

Answer 5

Theropoda:

Ceratorsauria, coelurosaruia, dilophosauridae, megalosauroidea, allosauroidea, etc

Evolved into Maniraptora

Question 6

Dinosaur clade groups in the Maniraptora group and what they evolved into

Answer 6

Maniraptora:

Alverazsauria, Therizinosauria, Oviraptorosauria

Evolved into Paraves

Question 7

Dinosaur clade groups in the Maniraptora group and what they evolved into

Answer 7

Paraves:

Eosinopteryx, Eumaniraptora (Troodontidae and Jinfengopteryx),

Evolved into Avealea

Question 8

Dinosaurs in the Avialea group and what they evolved into

Answer 8

Avialea:

Anchiornis, Archeopterygidae, Jixianogornis, Jeholornis, etc

Evolved into Pygostalia

Question 9

Organisms in the Pygostalia group

Answer 9

Pygostalia:

Current day birds

Question 10

Alligators: head shape, habitat, size, lifespan, salt glands, and body colour

Answer 10

Short, wide snout in a U shape

Freshwater only (NA/China)

Can reach up to 14 feet

30-50 years

Not fully developed, can’t cope in a salty habitat

Dark colour: black, grey etc

Question 11

Crocodile: head shape, habitat, size, lifespan, salt glands, and body colour

Answer 11

long, thin snout in a V shape

Can live in saltwater and freshwater and can be found everywhere

Can reach up to 19 feet

70-100 years

Fully developed, can expel salt if needed

Dark colour: black, grey etc

Question 12

Turtle/tortoise shell

Answer 12

Part of its body – bone filling in the gaps between ribs, growing out from the spine

Question 13

The years of dinosaurs ruling the planet and mass-extinction events

Answer 13

251mYa: end-Permian mass extinction wiped out 95% of species

215mYa: dinosaurs rule the planet (Triassic era)

200mYa: end-Triassic extinction, many species of Archosaurs died out

145mYa: end-Jurassic, Cretaceous period begins

66mYa: End-Cretaceous, all species except birds, small mammals, crocodiles, and other small organisms extinct

Question 14

Earliest dinosaurs

Answer 14

Archosaurs:
Reptiles with upright posture, pillar-like legs, and holes behind the eyes

Question 15

Three groups of marine reptiles: what are they, what were they like, and how long did they live (in mYa)?

Answer 15

Ichthyosaurs: dolphin-like, sclerotic eye rings (250-90)

Plesiosaurs: long-necked, lived everywhere (215-66)

Mosasaurs: large lizards related to monitor lizards (86-66mYa)

These were reptiles that had returned to the seas, they were not dinosaurs (dinos were not aquatic)

Question 16

Pterosaurs: what are they, where did they come from, how long did they live, and what are their significant features?

Answer 16

Flying dinosaurs

Phylogenetic origin uncertain (Lagerpetids??)

230mYa - 66mYa

• First vertebrate with powered flight
• Could not roost
• Includes quetzalcoatlus, the largest flying animals to ever exist

Question 17

Pterosaurs: what are they, where did they come from, how long did they live, and what are their significant features?

Answer 17

Flying reptiles - NOT dinosaurs but closely related

Phylogenetic origin uncertain (Lagerpetids??), is a type of archosaur

230mYa - 66mYa

• First vertebrate with powered flight
• Could not roost
• Includes quetzalcoatlus, the largest flying animals to ever exist
• Pteroid bone only found in them
• Non-pterodactyloid - small, have tails, early forms
• Pterodactyloid - large, no ail, most diverse group

Question 18

Stegosaurs: what are they, where did they live, how long did they live, and what might the back plates have been used for?

Answer 18

Quadrupedal dinosaurs with plates on their back

Every continent excluding Antartica (so far)

200mYa - 145mYa

• Initially thought to have plates as a defence mechanism but, since plates had weak support and capillaries were suggested to be near plates, it is likely that they were used for thermoregulation

Question 19

Saurischia: what does this mean and what species are part of this?

Answer 19

“Reptile-hipped” dinosaurs - Forward-oriented pubic bones

• Theropoda (Tyrannosaurs, etc)
• Sauropoda (Diplodocus etc)

Question 20

Ornithischia: what does this mean and what species are part of this?

Answer 20

“Bird-hipped” dinosaurs - Backward-oriented pubic bones

• Ornithopoda (Hadrosaurs etc)
• Thyreophora (Stegosaurs etc)
• Marginocephalia (Triceratops etc)

Question 21

Did dinosaurs have feathers?

Answer 21

Indentations in fossilised bones suggest dinosaurs may have had bones

Preserved feather in a 99 million-year-old amber suggests feathers existed back then

Question 22

What colour were dinosaurs?

Answer 22

Melanosomes can be found present in some well-fossilised bones which suggest dinosaurs were a chestnut/reddish-brown colour

Question 23

Oviraptor egg colours

Answer 23

A recent identification of bird egg pigments protoporphyrin and biliverdin in Oviraptor shells from China suggest eggs were blue-green,
like many modern birds

Question 24

Synapsid: what is it and what animals are an example of it?

Answer 24

A vertebrate with one major hole (temporal fenestra) in their skull

Most mammals and mammal-like reptiles

Question 25

Diapsid: what is it and what animals are an example of it?

Answer 25

A vertebrate with two major holes (temporal fenestrae) in their skull

Most reptiles and all birds

Question 26

Ectotherm: what is it and what animals are ectotherms?

Answer 26

An organism that relies on the environment to regulate its temperature

Reptiles, fishes, amphibians, etc

Question 27

Endotherm: what is it and what animals are endotherms?

Answer 27

Organisms that thermoregulate themselves

Mammals, birds, etc

Question 28

Therapsids: what are they?

Answer 28

“Mammal-like” synapsid reptiles that flourished during the Permian-Triassic periods until the last forms were extinct during the Cretaceous period

These are considered ancestors of the mammals