Lecture 8

Question 1

What differentiate the dinosauria from the dinosauromorpha?

Answer 1

Elongate deltopectoral crest on humerus (= powerful forearms)
B) Perforate acetabulum (a cup-shaped opening on either side of the
hips where the head of the femur inserts)
large muscle attachment scars on their skulls

Question 2

Could dinosaurs arm wrestle?

Answer 2

No, as they had limited outward rotation.

Question 3

What are three reasons why dinosaurs were so strong?

Answer 3

push ups
throwing meat into mouth
holding on to females

Question 4

Are all birds dinosaurs? are all dinosaurs birds?

Answer 4

yes, no

Question 5

How old are the oldest dinosaur body fossils?

Answer 5

228 Ma

Question 6

What is the oldest evidence of dinosaur footprints?

Answer 6

242-237 Ma in europe and south america

Question 7

When did dinosauromorphs first appear?

Answer 7

244-242 Ma

Question 8

The oldest known confirmed dinosaur material was found when and where?

Answer 8

In 229-218 Ma rocks in argentina

Question 9

why is there controversy around the oldest dinosaur fossils coming from south america (argentina)?

Answer 9

Because the rocks in which they’re preserved are not common globally, so it might just be that the rock in only preserved in south america

Question 10

When did non dinosaur dinosauromorphs go extinct?

Answer 10

by the end of the late triassic

Question 11

Dinosaurs were diverse and widespread which suggests that?

Answer 11

evolution and dispersal took place quickly after the first appearance of dinosaurs

Question 12

By the end of the late triassic, what happened to non-dinosaur dinosauromorphs?

Answer 12

they went extinct

Question 13

How did the dinosaurs become so diverse?

Answer 13

The dinosaurs became reproductively isolated and changed due to diff selective pressures resulting from variation in ecological conditons, so they physically couldnt exchange genetic material and they became so different they couldn’t interbreed

Question 14

What are the four factors that caused the great diversity of the dinosaurs?

Answer 14

variabiloty in dinos
ecological variability
changes over time
ongoing natural selection

Question 15

How are modern species defined?

Answer 15

By observing animals in nature (who’s mating with who), and by living organisms

Question 16

How are species defined in the fossil record as compared to defining modern species?

Answer 16

Cannot observe species mating in the fossil record, look at changes over time in species in the fossil record as we see then evolve

Question 17

What are morphospecies?

Answer 17

They are a group of individuals that have some reliable characters distinguishing from other species

Question 18

What is the issue with identifying morphospecies?

Answer 18

We can’t tell if the observed variation is due to individual variation, sexual dimorphism, ontogenetic change (changes with age) or an incomplete fossil record.

Question 19

If two specimens look different a paleontologist will?

Answer 19

probably identify them as two different species

Question 20

How do you identify gender in the fossil record? What issues come with this?

Answer 20

Genitals aren’t preserved, you can:
-find an egg in the body cavity
look for medullary bone (confirms it’s female), look for size differences and differences in ornamentation

Question 21

Does the absence of a medullary bone and/or an egg mean the dinosaur is male?

Answer 21

no, these features only confirm a female

Question 22

How do you identify age in the fossil record?

Answer 22

Looking at LAGS, lack of fusion in the skull bone which means it’s a juvenile look for spongier bones versus solid which identifies youth versus adult

Question 23

What are LAGS?

Answer 23

Lines of arrested growth- these are formed seasonally and can be counted to estimate age in dinosaur bones and teeth

Question 24

Are torosauras and triceratops different dinosaurs?

Answer 24

No, torosaurus is just an older version of a triceratops

Question 25

What are the features of nanotyrannus that posits it being a young t-rex? What posits that it’s not?

Answer 25

Being a young t-rex:
small
spongy bone
fused skull
17 teeth on each side in the lower jaw compared to the 11-14 in t.rex
(indicates that some tyranosaurs lose teeth as they age, but some t.rexes stay the same, or the number of teeth vary among individuals unrelated to growth/age)
not being a young t.rex:
large number of differences in the skull and skeleton (in size and shapes of bones, presence of a dental groove)

Question 26

What are the three major groups of dinosaurs recognized by paleontologists?

Answer 26

Therapods (mostly meat eating)
Sauropodomorphs (long necked dinos)
Ornithischians (everything else)

Question 27

Ancestors of the Sauropodomorphs were what pedal?

Answer 27

bipedal, through time they got larger and larger and could not longer move just with their hind legs

Question 28

How do scientists lump dinosaurs into two clades (the saurischian and the ornithischian)?

Answer 28

Based on the arrangement of bones in the hips (pelvic girdle) (the ilium, ischium, and pubis)

Question 29

What two ways are the pubis oriented, and what dinos do they identify?

Answer 29

1. Down and slightly forward- lizard hipped (saurischians)
2. At least part of the pubis points backwards as in the bird-hipped (ornithischians dinos)

Question 30

Based on hips what are theropods and sauropodomorphs considered?

Answer 30

saurischians, all other dinos are ornithischians

Question 31

What lineage led to the birds? The ornithischia or the saurischia?

Answer 31

The therapoda led to birds, since therapods are saurischia, saurischia

Question 32

The ornithischians are a ______ lineage?

Answer 32

extinct

Question 33

Why is ornithischia known as bird hipped, but did not give rise to birds?

Answer 33

The pubis rotates backwards as birds develop that why ornithscia are known as bird hipped, but saurischia dinosaurs is what led to birds

Question 34

What has more shared derived characteristics? Ornithiscia or saurischia?

Answer 34

Ornithischia

Question 35

Name the shared derived characteristics of all ornithiscians? (7)

Answer 35

Predentary bone
toothless and roughened tip of snout
a narrow bone (called the palpebral) that crosses the outside of the eye
socket
* jaw joint set below upper tooth row
* cheek teeth with low, subtriangular
crowns
* at least 5 sacral vertebrae
* ossified (turned to bone) tendons
above the sacral region

Question 36

What are the shared characters of the saurischia?

Answer 36

*Elongate vertebrae in the neck
* distinctly large hand
* loss of finger V
* thumb (digit 1) falls across the palm

Question 37

What does the limited shared characters of the saurischia indicate?

Answer 37

Carnivory

Question 38

What’s a more robust group? Ornithiscia or saurischia?

Answer 38

ornithischia

Question 39

What suggests that feathers evolved thrice versus once?

Answer 39

Therapods all share feathers- could say that feathers evolved once in therapoda, but tianyulong which was an ornithiscian dinosaur had feathers so they may have evolved twice, however some pterosaurs also had feathers so feathers may have evolved thrice or they evolved once at base of tree at ornithodira.

Question 40

In 2017 what revision of the dinosaur tree happened? What does this suggest?

Answer 40

They grouped theropods and ornithiscia into a new group called the ornithoscelida because they had more similarities, suggests that classic interpretation of hips being a diagnostic character are not true

Question 41

What did the 2017 reinterpretation explain?

Answer 41

That some members of the Ornithischia and Theropoda have feathers or feather-like
structures, but sauropodomorphs and herrerasaurids do not (but it could be that we
just haven’t found a sauropod with feathers yet).
* That primitive ornithischians look like theropods
* That birds are “lizard-hipped dinosaurs”- so feathers eolved once at base of ornithoscelida

Question 42

What problems are involved with the 2017 reinterpretation?

Answer 42

Both sauropodomorphs and theropods have pneumatic bones (bones with air sacs)
throughout their skeletons, but ornithischians do not.
* (Although pterosaurs also have pneumatic bones, so perhaps this is a primitive trait of
all Ornithodira?)
* Carnivory evolved twice (once in theropods and once in herrarasaurids

Question 43

Without DNA evidence what must we do when grouping dinos?

Answer 43

must decide which features of the skeleton are more important in terms of evolution

Question 44

What three groups of dinosaurs are scientists in agreement with? Where are they unsure?

Answer 44

three groups: ornithiscia, sauropodamorpha, theropoda
known that two groups more closely related but don’t know for sure, also don’t know where herrerasaurids fit in