Lecture 7

Question 1

Describe birds (what distinguishes frown from other vertebrates)

Answer 1

. Bipedal vertebrates
. Distinguished from other vertebrates by feathers- unique modifications of outer skin
. Toothless bulls with a horny sheath
. Effectively feathered flying machines
. Unique amongst extant vertebrates in that they have two distinct and independent locomotory systems

Question 2

What are the closest extant and extinct relatives to birds?

Answer 2

Extant- reptiles. Birds have many similarities to reptiles

most closely related to bipedal carnivorous dinosaurs: theropods

Question 3

What are the characteristics that birds and modern reptiles share?

Answer 3

. Skulls articulate with 1st neck vertebrae via a single condyle (ball and socket): occipital condyle
. Simple middle ear with only one ear bone (stapes)
. Lower jaws: 5-6 bones each side
. Hind limbs: angled or jointed between tarsal bones
. Scales on the legs of birds are similar to the body scales of reptiles
. Lay eggs with a yolk and a polar body
. ZW female heterogametic sex determination
. Both have nucleated erythrocytes

Question 4

How is the middle ear of mammals different to that of birds and modern reptiles?

Answer 4

Mammals have 3 ear bones, the others have 1

Question 5

How do mammals lower jaws differ from that of birds and reptiles?

Answer 5

Reptiles and birds have 5-6 bones each side whereas mammals have one mandibular bone

Question 6

How to mammals hind limbs differ to that of reptiles and birds?

Answer 6

Reptile and birds hind limbs are angled or jointed between tarsal bones whereas in mammals the angle is between tibia and tarsi

Question 7

What was the name of the crow sized bipedal reptile that suggests the evolution between reptiles to birds called?

Answer 7

Archaeopteryx

Question 8

Describe Archaeopteryx (how did it move)

Answer 8

. Blunt snout
. Small reptilian teeth
. Feathers on wing and tail, plus probably over body as well
. Feathers had asymmetrical vanes
. Probably not a strong flier (shallow keel) so perhaps glided from place to place

Question 9

What evidence suggested that Archaeopteryx was arboreal? What evidence supported that it was not and was cursorial?

Answer 9

. It has strong curved claws suggesting arboreal habits
. However, the sandstone beds that the fossil was recovered did not suggest that this was a forested area but indicated a lack of trees

Question 10

What did the early hypotheses of how birds evolved favour? What was issue with these hypotheses?

Answer 10

Favoured a thecodont origin and that birds split off early in crocodilian evolution.
Not an attractive idea because of a gap in the fossil record of 90 million years between Archaeopteryx and thecodont crocodiles

Question 11

What are theocodonts?

Answer 11

A diverse group of lightly built reptiles giving rise to crocodilians, ornithischians (‘bird-hipped), saurischians and Pterosauria

Question 12

What did Sauriscia give rise to?

Answer 12

Sauropodamorpha and Theropoda

Question 13

Give 2 examples (using a Latin name) of a Sauropodomorpha

Answer 13

Diplodocus, Brontasaurus

Question 14

What do theropods consist of?

Answer 14

. Carnosauria

. Coelurosauria

Question 15

Without feather impressions what would Archaeopteryx have been classified as?

Answer 15

A coelurosaurian dinosaur- small bipedel dinosaurs that probably chased small vertebrates and insects

Question 16

What do juvenile dinosaurs and birds both have?

Answer 16

Long-bone growth plates(- cartilage discs near ends of bone which allow rapid bone elongation during development) with a similar structure in birds and dinosaurs, the border between bone and cartilage undulates but is straight in other vertebrates

Question 17

What is Sinornis? Describe it and explain its importance in understanding the evolution of birds

Answer 17

. An early Cretaceous fossil from China
. A toothed sparrow-sized bird with many features of Archaeopteryx and Theropod dinosaurs
. Sinornis probably capable of sustained flight similar to that in modern birds

Question 18

What are the features intermediate between Archaeopteryx and modern birds (Neornithes)?

Answer 18

Hand modification for flight, ability to fold wings high over body, pygostyle for support of tail fan, perching foot with opposable rear toe or Hallux

Question 19

What is Confusciornis?

Answer 19

A fossil connecting dinosaurs and birds from China.

Modern-looking beak, but primitive diapsid skull, lacked a keel, possibly not a strong flier

Question 20

When was the Confusciornis alive?

Answer 20

Late Jurassic/ early Cretaceous

Question 21

What is Sinornithosaurus?

Answer 21

A Dromaeosaurid dinosaur with a filamentous integument, a bird-like shoulder girdle- a prerequisite for flight, but clearly a dinosaur not a bird because no proper feathers and no evidence that it could fly

Question 22

What is Unenlagia?

Answer 22

. Dinosaur from the late Cretaceous. Fills the gap (partially) between Archaeopteryx and non-avian Theropods Dromaeosauridae. I’d like Archaeopteryx in scapula morphology, pelvis and hindlimb
. Forelimb structure suggests that avian mode of forelimb folding, and extensive forelimb elevation necessary for powered flapping flight was already present in cursorial, non-flying Theropod dinosaurs
. But, too heavy to fly

Question 23

Describe Sinosaurapteryx and it’s connection to the evolution of birds

Answer 23

A small “feathered” dinosaur from China.
Important avian characteristics were already present in Theropod dinosaurs e.g. furcula (wishbone). Note also: typical Theropod characteristics, such as an enlarged claw on digit 2 on the foot, were also present in early birds. The skin of Sinosaurapteryx carried discrete filamentous structures- course sinuous filaments, possible branched, up to 40mm long. Are these protofeathers

Question 24

Describe Protoarcheopteryx

Answer 24

Small Theropod dinosaur, late Jurassic/ early Cretaceous beds (China): down-like feathers on body and tail, canes and barbed symmetrical feathers on body, arms, legs and tail

Question 25

Describe Caudipteryx and it’s connection to the evolution of birds/ what it suggests

Answer 25

Small Theropod dinosaur, late Jurassic/ early Cretaceous beds (China): reminds attached to 2nd finger of hand. Thus: down-like and later vaned body feathers evolved before flight feathers- full complement of feathers present in Coelurosaurs before birds had evolved

Question 26

Is Caudipteryx or Sinosaurapteryx more bird-like

Answer 26

Feathers (remige) attaching to the second finger of the hand of Caudipteryx are distinctly more bird-like than are the downy feathers of Sinosaurapteryx

Question 27

What are remiges?

Answer 27

Flight feathers

Question 28

What are retrices?

Answer 28

Tail feathers

Question 29

What do the remige (flight feathers) and retrices(tail feathers) in Caudipteryx have on them? What is this common in? Could Caudipteryx fly?

Answer 29

. They may have had tiny hooks that bind filaments into the aerodynamics structures common of flying dinosaurs
. They could not fly: arms far too short and flight feathers far too small to support body weight

Question 30

Describe nasal tyrannosauroid

Answer 30

‘Basal’ tyrannosauroid from the early Cretaceous if Liaboning, China, small and gracile, relatively long arms with three-fingered hands. The earliest known tyrannosauroid found so far.

Question 31

Give the evidence for protofeathers in tyrannosauroid

Answer 31

One specimen has a preserved filamentous integumentary covering similar to that of other coelurosaurian theropods from western Liaoning. The first direct fossil evidence that tyrannosauroids had protofeathers

Question 32

Feathers on flightless Theropods suggests what?

Answer 32

That feathers did not evolve for flight

Question 33

There is evidence that birds are the direct descendants of what?

Answer 33

Theropod dinosaurs

Question 34

Describe terror birds:Phorusrhacidae
(Describe what they looked like, where they lived and when, what is their modern relative, what do they set the record for?

Answer 34

Huge, flightless; tip predators in South America 62My- 15,000y ago; ~3m tall; modern relative- series’s. Record for the largest bird skull ever: 71cm long now with a curved 45cm beak

Question 35

What was Epidexipteryx hui?

Answer 35

A bird-like dinosaur with bizarre tail feathers

Question 36

What is Archaeopteryx widely accepted as being?

Answer 36

The most basal bird

Question 37

What are the features of Avialae? What do they characterise?

Answer 37

. Long and robust forelimbs

. Characterise the more inclusive group Paraves

Question 38

Give the features of birds

Answer 38

. Wishbones (furcula) 
. Breastbone (keep)
. Hollow bones
. Long arms and hands 
. Side-ways flexing wrists 
. Nesting behaviour 
. Rapid growth rates (discs of cartilage near ends of long bones) 
. Feathers 
(All these were present in the Theropod ancestors of birds)

Question 39

How is the forelimb of an avian wing modified? ( talk about the outerwing, the wrists and the hand)

Answer 39

. Outerwing skeleton
- fused hand and finger bones
- carpals and metacarpals are fused to form a carpometacarpus
. Most vertebrates wrists have 10 free carpals but words only have two
. Hand: 3 digits: digit 1 (thumb) moves independently

Question 40

Theropods have traditionally been assumed to have lost manual digits from where? This unusual reduction pattern in clearly present in what? Based on what? What does his contradict?

Answer 40

. The lateral side inward
. Present in basal theropods based on identification of their three digits as the medial ones of the hand (I-II-III)
. This contradicts the many developmental studies indication II-III-IV identities for the three manual digits of the only extant tetanurans, the birds

Question 41

A Jurassic ceratosaur from China helps clarify what?

Answer 41

Avian digital homologies

Question 42

Given II-III-IV identities in avians, the simplest interpretation is what?

Answer 42

That these identities were shared by all tetanurans. The transition to tetanurans involved complex changes in the hand including a shift in digit identities, with ceratosaurs displaying an intermediate condition

Question 43

What do comparisons among Theropod hands show?

Answer 43

That the three manual digits of basal tetanurans are similar in many metacarpal features t digits II-III-VI, but in phalanges features to digits I-II-III, of more basal theropods

Question 44

A new basal certosaur from the Jurassic (from in China)has what? What does this document?

Answer 44

Has a strongly reduced manual digits I, documenting a complex pattern of digital reduction within the Theropoda I

Question 45

Bilateral digit reduction more usual in what?

Answer 45

Theropods I.e. I-II-III-IV-B to II-III-IV

Question 46

Digits take on what identity during development?

Answer 46

Take on I-II-III during development

Question 47

‘Pro genesis’ or premature maturation of juveniles could lead to what?

Answer 47

To digit reduction

Question 48

Timing of maturation is likely to be subjected to strong what? Give an example

Answer 48

Strong natural selection
Fish from the high-predation marine population matured earlier than fish from low-predation pond population and males matured earlier than females (this is a dominant genetic trait)

Question 49

Plumage or integumentary coverings are more likely in what? Why?

Answer 49

Juveniles

High SA in relation to volume