Sedimentology and Palaeontology: The Mesozoic

Question 1

What is the time range of the Mesozoic

Answer 1

251 Ma to 66 Ma

Question 2

Describe the Triassic

Answer 2

251 Ma to 199 Ma

First mammals and dinosaurs

Pangea - Supercontinent with arid interiors

No ice on poles

Many different groups of reptiles. For example Smilosuchus (meaning chisel crocodile) which was very successful in the late Triassic.

Whereas dinosaurs were not particularly dominant at this point.

Oldest dinosaurs just over 230 million years old - Possibly Nyasasaurus.

True mammals appear in late triassic

Question 3

Describe the Jurassic

Answer 3

199 Ma to 145 Ma years

Dinosaurs, Pterosaurs, Marine reptiles are dominant.

Mammals live in shadow of the dinosaurs.

Pangea continues to break apart.

Salamander, caecilians, frogs.

Question 4

Describe the Cretaceous

Answer 4

145 Ma years to 66 Ma years

Dinosaurs continue to dominate

Giant flying reptiles push the limits vertebrate flight

Atlantic ocean appears

Question 5

Describe the plants of the Mesozoic

Answer 5

Spore plants common during mesozoic:
-Liverworts
-Mosses
-Clubmosses
-Ferns

Gymnosperms

Flowered plants can be traced back to Mesozoic

Angiosperms in early Cretaceous

Grasses extremely rare or absent

Question 6

What does the word ‘dinosaur’/’dinosauria’ mean and who formally named?

Answer 6

Dinosauria was formally named by Sir Richard Owen in 1842

Dinosauria means terrible/formidable lizard/reptile

Derived from the latin words Deinos (Terrible/formidable) and Saura (reptile/lizard).

Question 7

What are the misconceptions and misidentifications around dinosaurs

Answer 7

Dinosaurs: erect limbs
Pterosaurs: Are related to dinosaurs but are not dinosaurs themselves.

Marine reptiles often mistaken for dinosaurs

As well as many other reptile groups mistaken for dinosaurs.

Question 8

In what period were dinosaurs dominant and how many dinosaur species where there?

Answer 8

Dominant land species for most of the Mesozoic (180 million years).

Hundred of species ranging in size from over 40 metres to under 60cm.

Question 9

Describe Thyreophora

Answer 9

Thyreophora meaning ‘shield bearers’ all have rows of protective dermal ossificatons (bone).

This group includes the armoured dinosaurs, from plate backed Stegosaurs to tank like Ankylosaurs.

Not all armour though: the plates of stegosaurs may have been display structures.

Some ankylosaurs (including ankylosaurus) evolved extensive protective shields, as well as tail clubs which would be used to fight off predators.

Question 10

Describe Ornithopods

Answer 10

Almost entirely herbivorous, although possible some omnivores in early history.

Derived forms developed efficient jaws for chewing.

Some species moved in packs and likely using complex head crests and noises for communication and recognition.

Head crests like on the Parasaurolophus.

Question 11

Describe Marcinocephalia

Answer 11

“Ridge heads”

Majority of species from the Cretaceous, only a few from Jurassic

Two clades/types of morphology:

The dome headed Pachycephalosuaria

The deep beaked typically frilled Ceratopsia. Famous Ceratopsians like the triceratops have horns.

Question 12

Describe Sauropodomorph

Answer 12

Long necked herbivores

The largest group of which are the Sauropods which includes the largest herbivores to ever evolve.

Even small forms of Sauropods were about the size of an elephant.

Many weighed as much as 80 to 90 tons.

Question 13

Describe Theropoda

Answer 13

Named ‘Beast feet’ due to their curved claws.

Many had surprisingly light, hollow limb bones.

Large skull, serrated teeth, relatively short forelimbs.

This group includes T. Rex and Velociraptor, as well as lesser known fish eaters (like spinosaurus) and even herbivores.

Includes groups such as; Coelurosauria, Ornithomimosauria, Maniraptorans, Therinizosauroidea