Zoo 110 lec final: Reptiles, Amniote Innovations & Dinosaurs

Who are amniotes?

Reptiles + Birds + Mammals

The four extraembryonic membranes

1. Chorion

2. Allantois

3. Amnion

4. Yolk sac

What is the Amnion extraembryonic membrane’s function

1. provides nutrients, immune protection, waste removal, and gas exchange for the growing baby

2. Innermost part of egg

What is the Chorion extraembryonic membrane’s function

1. Outermost

2. Highly vascularized

3. Works with allantois to remove carbon dioxide and acquire oxygen

What is the Allantois extraembryonic membrane’s function

1. Sotres metabolic waste

2. Highly vascularized

3. Works with chorion

What is the Yolk sac extraembryonic membrane’s function

1. Provides nutrients

What are the nine innovations/features that characterize non-avian amniotes

1. Amniote egg

2. Keratinized epidermis

   1. Scales-> thicker more waterproof skin

   2. Some can shed off other species can’t

3. Aspiration breathing (negative pressure)

4. Greater (but still incomplete) separation of pulmonary & systemic circuits, high pressure blood flow

   1. Higher pressure than amphibians

   2. Separate right and left atrium

5. Ectothermic

6. Polyphyodont, homodont teeth

7. Vomeronasal (Jacobson’s) organ (VMO)

8. Internal fertilization

9. Metanephric kidneys, excrete uric acid

What are turtle shells made of?

Keratinized epidermis

What are the 4 orders in reptilia

1. Testudines

2. Squamata (Lizards & Snakes)

   1. Suborder Sauria (Lizards)

   2. Suborder Serpentes (Snakes)

3. Sphenodontia

   1. Tuataras

4. Crocodilia

Features of Order Squamata

1. Snakes are just derived, limbless lizards

2. Entire clade has a modified diapsid skull *** 

   1. Lower temporal bar lost, enables internally moveable (kinetic) skull

3. Males with hemipenes

   1. They get everted and are branched

What is special about Order Squamata’s kinetic skull

1. diapsid skull

   1. To make their skull very movable and to have their jaws open really wide

   2. Lots of additional space in their skull

   3. Increased kinetic power-> can move almost all independent skull bones

What are the first 3 specialized features of Suborder Serpentes

1. Skulls highly modified to swallow large prey

2. Able to walk their jaw forward to work their prey down their throat

   1. Pterygoid bone

3. Venom developed in many, e.g., rattlesnakes

What are the last 3 specialized features of Suborder Serpentes

1. Infrared sense in pit vipers like rattlesnakes

   1. Picks up prey in the dark

2. Use tongue and vomeronasal organ to smell

3. Many use constriction to suffocate prey

What are the four types of snake locomotion

1. Lateral undulation

2. Concertina motion

   1. Moves vertically in a narrow space

3. Rectilinear motion

4. Sidewinder motion

   1. Tumbling their bodies across the sand

Are “Reptiles” monophyletic or paraphyletic?

Paraphyletic

Why do we say reptiles “completed” the transition to land?

1. Developed key adaptations that allowed them to fully thrive on land without the need for an aquatic or semi-aquatic environment for their life cycle

2. First fully terrestrial vertebrates

What innovation was critical for completing this transition?

1. Most important: amniote egg

   1. Has tough shell preventing water loss = didn’t need to lay them in a water source

   2. Encloses amniotic sac

   3. Allowed them to move away from bodies of water and become larger

How do reptiles ventilate their lungs using negative pressure?

1. Use their diaphragm to produce negative pressure (low pressure) within the lungs that allows them to expand and draw in air

2. Crocs use a muscle that pulls their liver down to expand their pleural space instead of a diaphragm

How do birds & reptiles excrete waste?

1. Birds & reptiles= produce uric acid -> less toxic to the body tissues

   1. must detoxify ammonia by converting it

How is uric acid different from how animals that live in water excrete waste?

1. Aquatic= ammonia 

   1. a toxic waste that is highly soluble in water and easily diluted in the surrounding aquatic environment, so they do not need to conserve water in the same way

Which (synapsids vs. diapsids vs. anapsids) applies to most reptiles?

1. Diapsids 

   1. comprise a diverse range of reptiles, including lizards, snakes, birds, and crocodilians

What was the first vertebrate group to evolve flight?

1. Birds→ Pterosaurs

   1. are not dinosaurs

Was the first vertebrate group to evolve flight homologous or analogous with other vertebrate flight mechanisms?

1. partly homologous (from forelimbs), but analogous as organs of flight

2. pterosaurs

   1. the wing was a skin membrane stretched between an elongated fourth finger and the body

   2. was powered by large chest muscles, similar to birds

      1. but the anatomical structure supporting the wings was fundamentally different

3. Birds

   1. wings with feathers

   2. different arrangement→ finger bones are greatly reduced

How can we tell that the first vertebrate group to evolve flight was mainly analogous with other vertebrate flight mechanisms?

1. From the different structural origins (such as the elongated fourth finger in pterosaurs vs. the forelimbs in birds) and the distinct evolutionary paths of these groups.

   1. Birds and pterosaurs do not share a common ancestor with flight capabilities

Who were the 3 extinct aquatic reptiles?

1. Mosasaurs

2. Ichthyosaurs

3. Plesiosaurs

Did the extinct aquatic reptiles evolve from terrestrial or aquatic ancestors?

Evolved from terrestrial ancestors

Were the extinct aquatic reptiles oviparous or viviparous, and how do we know?

All = viviparous

First 3 anatomical similarities of avian and non-avian dinosaurs

1. Skeletal Structure

   1. lightweight, hollow bones, which reduce overall body weight while maintaining strength

   2. long, S-shaped necks, which are also seen in modern birds

2. Feathers

3. Bipedalism

Last 2 anatomical similarities of avian and non-avian dinosaurs

1. Pelvic structure

   1. While avian dinosaurs have a modified pelvic structure for flight, their pelvis is still similar in structure to that of non-avian theropods

   2. pubis points downward or backward

      1. birds have a more specialized version

2. Furcula (wishbone)

   1. clavicle that fused to form the furcula

   2. plays a role in reinforcing the shoulder during movement

Describe the Ornithischian dinosaur pelvis

1.  “Bird-Hipped”

2. Pelvis has ilium, ischium, and pubis

3. Pubis points backward, runs parallel with ischium

   1. Birds also have backward-pointing pubis

      1. convergent evolution

4. Hole in their pelvic bone ***

   1. Allows them to bring their legs underneath their body

      1. Why we see bipedal forms

Describe the Saurischian dinosaur pelvis

1. “Lizard-Hipped”

2. Pelvis has ilium, ischium, and pubis

3. Grasping hand, asymmetrical fingers, more mobile neck

4. Pubis at an angle to the ischium

Which dinosaur group did birds derived from?

Saurischians

What are the 5 different groups of Ornithischian we covered?

1. Ornithopoda 

2. Ceratopsia 

   1. (horned dinosaurs)

3. Ankylosauria 

   1. (armored ankylosaurus)

   2. Have a club on its tail that's really big

4. Stegosauria 

   1. (stegosaurus)

5. Pachycephalosauria 

   1. (pachycephalosaurs)

What are the 4 different memebers of the group Ornithopoda

1. Hadrosaurs 

   1. ("duck-billed dinosaurs")

2. Iguanodontids

3. Heterodontosaurs

4. Hypsilophodontids

What are the 2 major groups of Saurischian dinosaurs?

1. Sauropods

2. Theropods

What are the four features of birds that were already present in theropod dinosaurs

1. Feathers 

2. Furcula (wishbone)

3. Pneumatic (hollow) bones

4. Tridactyl foot with big toe pointed backward

   1. To be able to perch

What are the first 2 specializations of the avian skeleton

1. Furcula

   1. fused pair of clavicles forming a V-shaped structure

   2. acts as a spring, absorbing and releasing energy during flight

   3. provides attachment points for key muscles involved in wing movement

2. Hollow bones

   1. internal struts or trabeculae that provide strength while minimizing weight

   2. reduces the bird's body weight without compromising skeletal strength, which is essential for flight

   3. often pneumatic

What are the last 3 specializations of the avian skeleton

1. Keel on sternum

   1. prominent ridge or extension of the sternum

   2. serves as the attachment site for the pectoralis muscles

2. Fused Bones

   1. carpometacarpus (carpals and metacarpals)

   2. tibiotarsus (tibia fused to tarsals)

   3. tarsometatarsus (tarsals fused to metatarsals)

3. Foot with three toes (digits II-IV) forward, big toe back

How do birds perch?

1. Automatically-tightening tendons close the toes down around a perch

2. Extends into toes

3. When they crouch down, it automatically contracts the muscle

What are the 4 types of feathers we covered in class?

1. Contour feathers

2. Flight feathers 

3. Down 

4. Aftershaft feathers

What are the main 2 types of feathers we focused on in class?

1. Contour feathers

   1. Give the bird shape

2. Down

   1. Super fluffy

   2. Conserves heat

What are the two muscles that move a bird’s wing

1. Pectoralis muscles

2. Supracoracoideus

What does the Pectoralis muscles control/ where does it originate?

1. which control the downstroke of the wings

2. Originates on the ventral part of the humerus

What does the Supracoracoideus control/ where does it originate?

1. raises the wing

2. Originates on the top of humerus and passes through a space in the coracoid to the chest

What is unique about the avian respiratory system?

1. Unidirectional Airflow

2. efficient oxygen exchange

How does the avian respiratory system work?

1. achieved through a system of air sacs

2. Has two cycles of inhalation and exhalation

   1. push air through the lungs in one direction

Describe the two cycles of inhalation and exhalation in the avian respiratory system

1. Inhalation 1: 

   1. Air enters the trachea, flows into the posterior air sacs.

2. Exhalation 1: 

   1. Air from the posterior air sacs moves into the lungs, where oxygen is absorbed and carbon dioxide is released.

3. Inhalation 2: 

   1. Air moves from the lungs to the anterior air sacs.

4. Exhalation 2: 

   1. Air is expelled from the anterior air sacs, leaving the body

Did feathers evolve for flight? If not, what are some possible reasons for the evolution of feathers?

1. Not necessarily

   1. likely used for insulation, display

   2. however, in some species it may aid in flight

Who is Archaeopteryx?

1. An extinct early bird 

   1. transitional forms-> show us features that are intermediate between groups

Which of Archaeopteryx’s features are birdlike?

1. had feathers

2. Bones that are more bird like

   1. Lunate wrist bone

   2. Furcula (wish bone)

Which of Archaeopteryx’s features are reptilian like?

1. long tail, teeth 

2. three -fingered manus

3. Shoulder girdle

4. Small sternum 

5. Abdominal floating ribs

6. Partially fused metatarsals

What is the most diverse group of tetrapods?

Birds-> More than 10,500 species

What is unique about the bird reproductive tract, and how is this related to flight?

1. Ovary typically present on left side only, enlarges during reproductive season

   1. single functional ovary results in a lighter body

      1. As having a large, functional reproductive organ on both sides would add unnecessary weight, which could impair flight

How do birds fly?

1. two features: angle of attack + camber

2. When air is being directed downward, there is more pressure on the bottom of the wing

3. By lift and thrust

How do birds generate lift?

Created by the wing's airfoil shape and angle of attack, causing air pressure differences above and below the wing

How do birds generate thrust?

Generated by the bird's flapping wings, with the downstroke providing most of the forward propulsion

What are the 4 different wings forms?

1. Elliptical

   1. Length to width = equal 

   2. Low speed

2. High speed

   1. Slender tips of the wings

   2. Good for high speed flight

   3. exception-> hummingbirds

3. Dynamic soaring

   1. Long wings

4. High-lift or passive soaring

   1. Thick and long wings with wing slots

What type of wing is used by songbirds and others that must be highly maneuverable?

1. Elliptical

   1. allows for rapid turns, quick ascents, and changes in direction

What type of wing is used by birds that fly over the ocean?

1. Dynamic Soaring Wings

   1. maximize lift and minimize drag, allowing birds to glide for long distances without much flapping

2. Ex: Albatrosses

What type of wing is used by birds that soar over the land?

1. Broad, Long Wings with Slotted Tips

   1. improve lift and control

   2. thermal soaring, where birds use rising air currents (thermals) over land to gain altitude and glide for long periods

2. Ex: Hawks and vultures

What are the two groups of aves since dinosaurs?

1. Paleognathous birds

   1. flightless bird

2. Neognathous birds

   1. Birds that can fly

What are five threats to bird populations?

1. Invasive species

2. Deforestation

3. Pesticides

4. Lead poisoning

5. Housecats

What is the threats to bird populations (at least in N. America)?

Housecats