Reptiles and Birds Flashcards
How many fenestra do anapsids have?
0
How many fenestra do diapsids have?
2
Why are turtles hard to place on a phylogenetic tree?
They have no fenestra (anapsids), so they would be placed before the divergence of synapsids and sauropsids, if not for other evidence
What are the possible phylogenetic hypotheses on the placement of turtles?
- Diverged after split of Amniota as a sister taxon to Diapsida
- Diverged after Diapsida as a sister taxon to Sauria
- Diverged after split of Sauria into Lepidosauria and Archosauria, as a sister taxon to Lepidosauria
- Diverged after split of Sauria into Lepidosauria and Archosauria, as a sister taxon to Archosauria
Where are turtles placed in the amniote phylogenetic tree based on our current hypothesis?
After the divergence of lepidosaurs and archosaurs, as a sister taxon to Archosauria
What are some fossil pieces of evidence that support hypothesis 4 seen in stem turtles?
They have an upper temporal fenestra, and the development of a carapace, and plastron (which gastralia fused into). Gastralia are seen in Archosauria
Although turtles are diapsids, why do they have no temporal fenestra?
Temporal emargination caused the loss of fenestrae
Why might it be important for turtles to separate locomotion and lung ventilation, like crocodiles?
Lie-in-wait predation strategy requires little to no movement, and they can’t use buccal pumping due to their lack of gills
How are members of Lepidosauria distinguished from each other (Rhynchocephalia, Serpentes, and “lizards”)?
The position and/or absence of their temporal bars
What is the sister taxon to Squamata?
Rhynchocephalia (Tuataras)
List the synapomorphies of Lepidosauria
Keratinous overlapping scales
Transverse cloacal opening
Autotomy planes in caudal vertebrae and muscles
What dermal layer are scales made of? What biological mechanism determines its patterning?
Ectoderm; molecular pre-patterning by activators and inhibitors
What three characteristics of scales are used to determine locomotive ability?
Organization, shape, and overlap tell us about the locomotive strategy
Transverse vs. sagittal
Transverse goes across the body (lateral to lateral), while sagittal goes up and down the body (cranial to caudal)
What mechanism may be regulating autotomy planes?
HOX genes
True/False? The location of an autotomy plane on the vertebrae is the same for all lepidosaurs
False. Varies by species
Why are autotomy planes useful in studying lepidosaur development?
They are well-preserved in the fossil record, as they are seen in the vertebrae
How do lepidosaurs drop their tails without dying of blood loss?
Segmented muscular bundles prevent bleeding by restricting blood flow to that autotomy plane
What is a unique feature of tuatarans?
They have no ear openings and have a pineal eye
List the synapomorphies of Rhynchocephalia
Lower temporal bar re-evolved
What can we infer about the skull structure of squamates in relation to the synapomorphy of Rhynchocephalia?
They lack the lower temporal bar
List the synapomorphies of Squamata
Hemipenes
What is a hemipene?
A 2-headed penis that squamates have that function independently of each other
A phylogenetic tree based solely on morphology has what trends?
It tends to be polyphyletic (skinks), and some groups cannot fit into clades
A phylogenetic tree based solely on molecular evidence has what trends?
Tends to be more monophyletic
A phylogenetic tree based on morphology and molecular evidence has what trends?
Both monophyletic and polyphyletic, but more specific than just molecular evidence, strongest argument
List the synapomorphies of Serpentes
Upper temporal bar lost
The loss of the lower and upper temporal bars allow for what in snakes?
Cranial kinesis
What is cranial kinesis?
The ability of the components of the skull and jaw to move independently, especially when eating
What is jaw walking?
The independent movement of the left and right sides of the skull and jaw to move when eating large prey
What is another name for the upper temporal bar?
The jugal
The jugal makes up which important bones in the skull?
The upper and lower bars
What are some features of Dibamidae? What do they resemble?
Absence of ear holes
Rudiments of the hindlimbs
Highly fused head
Fossorial locomotion
Resemble caecilians (convergence!)
What is a synapomorphy of Gekkota?
Toe scansors
What is unique about Pygopodidae?
Limbless, but have pads and flaps where the pelvic and pectoral girdles would be
Fossilized gecko specimens show what evidence?
Toe pads
What organisms does Scincoidea include?
Skinks
What squamate clade is the most speciose?
Scincoidea
What is the main difference between Lacertidae and Teiidae?
They vary geographically (Lacertidae is old world, Teiidae is new world)
Where do mosasaurs fit into the Sauria phylogeny?
Sister taxon to Serpentes (under Squamata)
What evidence suggests mosasaur’s positioning on the phylogenetic tree?
They have a forked tongue and similar palatal morphology to snakes
Helodermatidae
Gila monsters, extremely venomous, slice flesh which teeth and let venom seep into wound
Varanidae
Monitor lizards, semi-aquatic
What is the main difference between Agamidae and Phrynosomatidae?
Geography. Agamidae is old world, Phrynosomatidae is new world
Chamaeleonidae
Chameleons. Zygodactyls, arboreal, protrusible tongues
Dactyloidae
Anoles. Show extreme convergent evolution due to biogeographical separation
Iguanidae
Iguanas
What are the three sensory systems in Squamata?
Vomeronasal, nasal olfactory, and gustation
Describe the olfactory system in squamates
Large surface area in the nasal cavities allows for chemosensation
The vomeronasal system in squamates connects which structures?
Olfactory surface area and palate
Describe the gustatory system in squamates
Taste buds on lingual and oral surfaces
What are the two predatory modes seen in squamates?
Sit and wait and active foraging
What impacts predation mode?
Reliance on chemosensation
Sit and wait predators rely on:
Eyesight
Active foraging predators rely on:
Chemosensation
How do active foragers use chemosensation to hunt?
Able to use all three systems to determine strength of signals for directional sensing
What is usually associated with sit and wait predatory styles?
Cranial ornamentation, crypsis, and territoriality
What are the defense mechanisms seen in Squamates?
Autotomy, crypsis, venom, and deterrence
Describe autotomy
The loss of the tail along an autotomy plane. Its regeneration depends on the diet of the organism
Are squamates the only organisms that use autotomy?
No. In some cases, fish use this tactic too, with their scales
What is crypsis?
Blending in with the environment
Provide an example of an organism that uses deterrence
Horned lizard (Phrynosomatidae)
Explain how Phrynosomatidae uses deterrence
There is a lot of venous drainage behind the eye. When threatened, muscles squeeze these veins, which builds pressure in the head until they rupture and squirt blood onto the threat. Blood does not chemically differ from circulatory blood, so no other chemicals but the blood itself is used
What is important about venom glands in terms of development? How do we know?
Derived from salivary glands; they contain pancreatic enzymes
Why is venom important to study? Provide an example
Can be used to derive drugs. For example, the GLP-1 protein found in some venom is used in Ozempic
What is a gular fan?
A fan located on the throat of an anole used in communication in conjunction with head bobs
What kind of gular fan would be used in a very green, leafy area?
Red, for high contrast
What kind of gular fan would be used in a place with lots of light?
A translucent flap, that refracts light
Describe gular fans in the context of mating rituals. What colours mean which?
Orange: establishes large territory and roster of females
Blue: establishes small territory
Yellow: sneaker male, steals females from blue and orange
What is the tradeoff between gular fans and crypsis?
Bright fans may attract predators
Lizard dialects
Vary depending on species, using the same methods but in different ways (more head bobs than another species, for example)
The development of different lizard dialects may lead to:
Speciation by reproductive isolation
Describe what happens when only juvenile skinks are present in a basking setting
All get lots of time to bask
Describe what happens when only skinks within a family are present in a basking setting
All get lots of time to bask
Describe what happens when dominant and subordinate skinks are present in a basking setting
Dominant skinks get lots of time basking, while subordinate skinks spend most of their time in shade because they aren’t permitted access by the dominant skinks
Describe how communication between skinks impacts fitness
Subordinate skinks have reduced fitness because they do not achieve the level of sunlight they need for proper thermoregulation. Dominant skinks have increased fitness for the opposite reason
True/False? Lizards can be viviparous
True
What is the difference between lizard placenta and placental placenta?
Placentals have much more physical connection to their mothers, while lizards don’t have as much
What are the benefits of being a viviparous lizard?
Eggs don’t have to be warmed, and movement isn’t limited by a nest
What are the disadvantages of viviparity in lizards?
More parental care (energetically costly), which leads to smaller clutch sizes, and locomotion and communication are limited
What are the pressures that might have caused parthenogenesis to evolve?
No energy is spent on reproduction, and extreme temperature determines sex (usually favours females, which can undergo parthenogenesis again if need be)
Describe how you can get a fertilized egg through parthenogenesis
In extreme heat conditions, 1/3 polar bodies created by meiosis fuses with the oocyte, causing a fertilized egg
Which sex determination strategy do most lizards use? What clades are the exceptions?
Genetic; Gekkonidae, Scincidae, Chamaeleonidae
What is unique about geckos in terms of sexual reproduction?
They have similar sex chromosome complexes to Monotremes (can use XY or ZW)
An organism with ZZ sex chomosomes is _________
Male
An organism with ZW chromosomes is ________
Female
True/False? Serpentes uses both genetic and environmental sex determination
False. They use genetic sex determination
What sex determination method do Testudines use?
Environmental sex determination
How do homeothermic ectotherms regulate body temperature? How does this differ from endotherms?
Use behaviour rather than metabolism
Describe the behaviour of a homeothermic ectotherm lizard on a warm day
They actively seek out heat from the environment and bask with most of their body’s surface area facing the sun. They are active once within their optimal temp range
Describe the behaviour of a homeothermic ectotherm lizard on a hot day
Utilize convective cooling from the environment (like wind) and reduce surface area exposed to the sun either by staying in the shade or facing directly towards the heat source
Describe the behaviour of a homeothermic ectotherm lizard on an extremely hot day
They avoid activity all together and seek shelter
How does activity level change in homeothermic ectotherms as environmental temperature increases?
No activity if cold, optimal range has most activity and it decreases as heat increases from there
In what conditions do homeothermic ectotherms and endotherms converge in terms of energy conservation
In extreme heat
What is a facultative endotherm?
Can occasionally use metabolism to generate body heat
What function does facultative endothermy serve in lizards?
Has links to sex determination in species that rely on the environment
Allopatric speciation
Speciation occurs due to physical barriers, like geography
Sympatric speciation
Speciation occurs due to niches within one geographical area
Provide an example of sympatric speciation
The Ameiva genera, that speciated due to light availability differences in a forest
How does weight impact sympatric speciation in Ameiva?
Species of lesser weight tend to spend more time in the unshaded areas, while greater weight species tend to spend more time in the inner forest. Species in the middle of this weight distribution spend time at the edge of the forest
Why do smaller Ameiva species spend more time in unshaded areas?
They gain and dissipate heat a lot faster and have a higher metabolism, so they can dart in and out of the sun without overheating
Why do larger Ameiva species spend more time in shaded areas?
They dissipate heat much slower, so are at risk of overheating in unshaded areas. They can bask, then spend much more time in the shade than smaller species
Where would juveniles of larger Ameiva species tend to hang out? What is this an example of?
Spend more time in unshaded areas because they dissipate heat faster, but as they grow they move towards the inner forest; niche partitioning
What is an ecomorph?
Two species with different phylogenetic origins that share a particular niche
The presence of an ecomorph suggests what for the niche the species share?
Convergence
What are the three key attributes of snake locomotion?
- Epaxial and hypaxial musculature and connective tissue
- Vertebral interactions
- Relative position of the ribs to vertebrae
What do tendons connect?
Muscles to muscles
What modifications to the vertebrae do snakes have? How do they aid in locomotion?
Extra zygapophyses (zygosphenes and zygantra), which increase the stability of the vertebrae and disallow independent motion of each vertebra
Where are the ribs located in snakes? What does this allow for?
Attached to the vertebrae and present all along the body excluding the tail. They allow for the different modes of locomotion in snakes (rectilinear, gliding, concertina, etc)
Why do snakes have a loss of limbs?
Reduced HOX gene signaling in the limb buds
How does girdle position relate to limb reduction and movement?
The farther the girdles, the more reduced the limbs, the more lateral undulation
Why are snakes seen as the “reverse transition to land”?
Because in the transition to land, limbs were gained, but snakes lost their limbs
What was the primary environmental pressure for the loss of limbs and scale pattern on the ventral surface?
Substrate interactions
Describe lateral undulation
Hypaxial muscles within a segment on one side of the body work together to contract while the muscles of the same segment on the other side of the body are relaxed. These segments alternate throughout the body at any given time (first segment, left contracted. Second segment, right contracted. Etc)
What is an extreme of lateral undulation?
Gliding
Describe gliding locomotion (snakes)
The ribs move with the hypaxial musculature to flatten, creating a “wing” out of the snake’s entire body
Describe sidewinding
Snake uses extra epaxial musculature to “skip” sideways along with the hypaxial movements of undulation
In what climates is sidewinding used? Why?
Hot climates (deserts) with loose substrate; it reduces surface area in contact with the hot sand, which helps in thermoregulation
Which snake locomotion strategy is the fastest but most energy consuming?
Sidewinding
Describe rectilinear motion
Most hypaxial muscles contract and stretch in segments along the ventral surface used in a caterpillar-like movement
What kind of ventral scales does a sidewinder require?
Porous to reduce friction and surface area exposed to substrate
What kind of ventral scales does a rectilinear snake require?
Thick dermis that can withstand high abrasion
What is the tradeoff with rectilinear motion?
Slow, but conserves energy
What kind of snake will use rectilinear motion?
Very venomous snakes that don’t need to chase down prey
Describe concertina motion
Snake creates anchor points by pinching its substrate between its segments using hypaxial muscles. Used to climb. Epaxial muscles used to extend the neck after anchoring to move to the next anchor point
What is a pit organ? Which nerve innervates it?
An organ snakes use located near their mouth and eyes to sense thermal traces. Innervated by the cranial nerve that also attaches to the eye
How do snakes use their pit organs?
Use them in conjunction with their eyes
If snakes could only use their pit organ and eye contralaterally (one left and one right), what would happen? What does this imply?
Contradiction in their ability to pinpoint the location of prey; rely on both organs on both sides altogether
What do snakes use in their predation strategies?
Venom and constriction
What kind of motion do constrictors use to hold prey?
Concertina
Why do constrictors target mammals?
Mammals use diaphragmatic breathing, which is easy to stop if the prey item is squeezed so their lungs can’t expand
What evidence suggests venom glands are derived from salivary glands? Are they homologous or analogous?
They have proteins that are similar to the enzymes (pancreatic-like) found in salivary glands. They are homologous structures
Which tissues have the potential to be venom glands in snakes? What does this show?
Venom gland, rictal, infralabial, and potentially the supralingual; convergence
Describe the head musculature in boas. Why?
Superficial and deep masseter; they are nonvenomous so don’t need specialized muscles
Describe the head musculature in vipers. Why?
Superficial and deep masseter, with a specialized deep masseter looping around the superficial; used to squeeze venom out of the venom gland
Describe the head musculature in early snakes. Why?
Superficial and deep masseter, but venom gland is medial to superficial; muscles “stimulate” the venom gland rather than “squeeze” it
Describe how teeth, fangs, and venom glands have the same developmental origin
Form from the same developmental lamina as venom glands consisting of neural crest plus mesenchyme
Compare boid and viperid vertebrae
Boid: less lateral protrusion to allow for more lateral flexibility (needed to constrict prey)
Viperid: more lateral and dorso-ventral ornamentation to allow for more muscle attachment (faster striking)
What predation modality would we see in constrictors more often?
Active foraging
What predation modality would we see in venomous snakes more often?
Sit and wait, use crypsis
Describe cranial kinesis. What is this called?
Jaw is able to unhinge to allow consumption of large prey items; “jaw-walking”
What are the defense mechanisms snakes use?
Caudal lure, spitting venom, venomous resistance, and aposematism
What is aposematism?
Mimicry (non-venomous looks like venomous)
Aposematism is likely a result of:
Convergent evolution
Why do snakes have indeterminate growth?
Their low metabolisms allow them to put much more energy into producing new tissue than mammals, which use most of their energy just maintaining homeostasis
In terms of thermoregulation, snakes are:
Homeothermic ectotherms
Like other squamates, snakes can sometimes be ____________ endotherms
Facultative
When do squamates tend to use facultative endothermy?
When incubating eggs
Why is studying Titanoboa important?
Researchers able to deduct the environment in which it lived by studying the vertebrae and correlating its size to body temperature, which suggests it lived in cooler places due to its massive size
List the synapomorphies of Testudines
Ventral osteoderms fused together (plastron)
Axial skeleton fused to osteoderms (carapace)
Carapace and plastron fuse together to form the shell
Shell is covered with keratinous plates superficially (scutes)
Pectoral and pelvic limb girdles within the shell
Loss of teeth, have keratinous beak
Describe the placement of scutes relative to the fused bones underneath
Scutes are larger than the individual bones, so one scute covers multiple bones in order to distribute applied weight more evenly
What kind of organ are scutes?
Ectodermal
Which came first? The carapace or the plastron?
Plastron developed first
What was the function of the plastron in ancestral turtles?
Aquatic ballast
Gastralia are homologous to:
The plastron
Why do we believe the plastron developed from the gastralia?
They share the same organizational pattern
Why do turtles need an aquatic ballast?
They don’t have a swim bladder like fish
Compare the amniote pectoral girdle to the testudine pectoral girdle
Amniotes:
- protrude dorsal to ribs
- muscle plate follows the curve of the rib
Testudines:
- internal to the shell (ventral to ribs)
- muscle plate follows the curve of the rib, then wraps around the scapula (change in muscle connectivity)
Why did turtles evolve their girdles the way they did?
They needed to be modified in order to accommodate the shell
Describe the differences and similarities between archosaurian and testudine ectodermal organ patterning in relation to teeth
The same in every way except turtles lack the ectodermal patterning pathways specific to teeth
What is the main difference between Cryptodira and Pleurodira?
Cryptodira folds its neck into a dorsoventral “c” shape, while Pleurodira folds its neck into a lateral “c” shape
What are the challenges of living within the shell?
Ventilation
Locomotion
Feeding
Muscular insertion and origins
Thermoregulation (linked to sex determination)
Describe the differences in the pelvic girdles between cryptodires and pleurodires
Cryptodires: pelvic girdle not fused with the shell
Pleurodires: pelvic girdle fused with shell
What were the results from a multi-varied analysis on turtle musculature between Cryptodira locomotion and Pleurodira locomotion?
The way in which the muscles worked was highly differentiated between Cryptodira and Pleurodira (different muscular insertions and origins), but they converged on muscle performance and efficiency (working together) in locomotion (walking muscles used similarly, swimming muscles used similarly)
Describe diagonal sequence locomotion
Left front foot and right back foot step forward together and vice versa
Describe lateral sequence locomotion. What is this type of locomotion seen in?
Left side works together, right side works together; big tortoises (Testudinidae)
Describe synchronous locomotion. What is this type of locomotion seen in?
Front flippers work together synchronously; sea turtles (Cheloniidae)
What kind of locomotion would you expect to see in a semi-aquatic (pond) turtle?
Both diagonal and synchronous
Contrast diaphragmatic breathing and Testudines breathing
Testudines: active inhale and exhale
Diaphragmatic: active inhale, passive exhale
Describe inspiration in turtles
Pectoral girdle is pulled cranially, pelvic girdle pulled caudally, which causes negative pressure within the gut, which then causes negative pressure within the lung
Describe exhalation in turtles
Pectoral girdle pushed caudally, pelvic girdle pushed cranially which causes positive pressure in the gut, which then causes positive pressure on the lungs
What is an important part of turtle respiration?
The gut
The snapping mechanism of a turtle’s jaw is enabled by this component:
Otic capsule (part of the jaw joint)
Describe the sequence of selection pressures on turtles that resulted in the development of the otic capsule
The shell put pressure on the neck (needed increased mobility), which put pressure on the skull (mobility requires emargination), which then put pressure on the existing jaw structure (development of a new joint)
What is green fat?
Turtle homologue to brown fat in mammals
What thermoregulatory strategy do turtles use?
Homeothermic ectothermy
Why are turtles spending less time in the water, even at night?
The water is getting too hot for them during the day, then it retains that heat at night, so they don’t go back in
Why is climate change an issue for Testudines?
They use environmental sex determination
What is the muscular ridge?
It is the shunt in Testudines that separates deoxygenated blood from oxygenated blood when the ventricle contracts
Describe what happens in the contraction of the atria in turtles
Atrioventricular valves are open, allowing oxygenated blood into the left side of the ventricle and deoxygenated blood into the right, separated by the intraventricular canal
Describe what happens in the contraction of the ventricle in turtles when the muscular ridge is contracted
Atrioventricular valves are closed and the muscular ridge is contracted, separating oxygenated blood and deoxygenated blood. Oxygenated blood goes to the right and left aorta, deoxygenated blood goes to the pulmonary artery
What is the advantage of having the intraventricular shunt?
Used for lower metabolism to allow for increased blood oxygen efficiency by reducing blood flow to the lungs when not in use (swimming). Also used to increase systemic blood flow when basking to warm up faster
The intraventricular shunt in turtles is convergent to what in crocodylians?
Inter-aortal sunt (Foramen of Panizza)
Explain testudine migration
They are born on an island east of Brazil and migrate west for most of their lives, until they’re ready to reproduce, then they swim back to the same beach they were born at and lay their eggs there
What are the cues used by sea turtles in their migration back to the island they were born at?
Geomagnetic imprinting, light (direction and phase of the moon), and wave directionality (underwater currents act like highways)
How is turtle migration biology applied to ocean research collection?
Robots were developed to use the same cues to navigate the ocean
Describe type Ia sex determinism in turtles
Low temp: male
High temp: female
Describe type II sex determinism in turtles
Extreme temps: female
intermediate temps: male
What are the consequences of having mostly environmental sex determination in a climatically unstable environment?
- more of one sex than the other
- impacts their behaviour
- eggs need to be incubated at a specific temperature to conserved the bottle-necked sex
Describe the vulnerable hatchlings experiment
Hatchlings were put on a small island and exposed to various levels of white light and moonlight exposure to see what impacted their movement to the ocean
What was seen in the white light vs moon night treatment?
Most turtles moved towards the white light, but some were rescued by the moon and moved towards the ocean
What was seen in the weak white light vs moon night treatment?
Most turtles moved towards the white light, but some were rescued by the moon and moved towards the ocean
What was seen in the white light vs moonless night treatment?
Almost all turtles moved towards the white light
What was seen in the weak white light vs moonless night treatment?
Almost all turtles moved towards the white light
In the vulnerable hatchlings experiment, what was the difference between white light and weak white light?
No difference
In the vulnerable hatchlings experiment, what was the difference between moon night and moonless night?
Some hatchlings were rescued by the presence of the moon, whereas on moonless nights, none made it to the ocean
How can the vulnerable hatchlings experiment be applied to their conservation?
Coastal cities may impact where the hatchlings are attracted to, which negatively impacts them by attracting them away from the water
List the synapomorphies of Archosauria
Antorbital fenestra
Mandibular fenestra
Thecodont teeth (how they use the teeth)
Double row of osteoderms along vertebral column
Fourth trochanter on the femur
How many fenestrae do archosaurs have in total?
4
Osteoderms in general would be a(n) ___________ of Archosauria
Apomorphy
What are the hypotheses for the development of the mandibular and antorbital fenestrae?
Extra room for muscles or to make the skull lighter (sinuses)
How does the development of the 2 extra fenestrae assist birds?
Assists in the evolution of flight (lighter head if they were sinuses and not for muscle attachment)
What are thecodont teeth?
Teeth heavily rooted in the jaw
What is the shape of an early archosaur’s upper jaw? Why?
Hooked at the rostral end; helps to prevent prey escape
What allows for the double row of osteoderms seen in archosaurs?
HOX gene expression
A heavily protruding fourth trochanter indicates:
Locomotion is more reliant on the tail
What does the fourth trochanter serve as?
A muscle attachment site for the main undulatory tail muscle
What is implied about the reduced fourth trochanter in avians?
They rely less on their tail for locomotion
Why is the majority of muscle strain on the fourth trochanter?
The muscle that attaches to this point is very reliant on this process, and the organism that uses this muscle is very reliant on the muscle
True/False? Archosauria includes the dinosaurs
True
What are the non-avian dinosaurs?
Everything except Neornithes
What are the avian dinosaus?
Neornithes
The faveoli in crocodylian ventilation are analogous to:
Lamellae in the gills of fish
What type of ventilation do crocodylians have?
Cuirassal ventilation
What type of ventilation do avians have?
Unidirectional ventilation
What is the general change in the structure of the ventilation from crocodylians to avians?
Increased rigidity of respiratory organs
True/False? Much like testudine ventilation, crocodylians actively exhale and inhale
True
Describe the difference in the relative position of testudine ventilation structures versus crocodylian ventilation structures
Turtles: dorso-ventral
Crocodylians: Cranio-caudal
Because turtles respiratory structures are dorso-ventral, what force are they more impacted by than crocodylians?
Gravity
Explain inhalation in crocodylians
Negative pressure in the lung is caused by contraction of the diaphragmatic muscles
Explain exhalation in crocodylians
Forced contraction of the gastralial muscles, which allows for the air in the lungs to be exhaled. Pulls the lungs cranially to force air out
How many of cycles of respiration are needed to exhale a single molecule of O2 in birds?
2
Describe inhalation in birds
Negative pressure draws oxygenated air into the posterior air sacs. At the same time, negative pressure brings deoxygenated air from the lungs into the anterior air sacs
Describe exhalation in birds
Positive pressure pushes oxygenated air from the posterior air sacs into the lungs. At the same time, positive pressure pushes deoxygenated air from the anterior air sacs out
Is the unidirectional ventilation system efficient?
Very efficient, as there is no anatomical deadspace as there is in humans (cannot breathe out all of the air in our lungs)
Why do birds need such an efficient ventilation system?
Needed for flying, as this is very oxygen-dependent
What is the name of the shunt in crocodylians?
Inter-aortal shunt (foramen of Panizza)
Describe typical blood flow through a crocodylian heart
Pressure in the systemic circuit (left ventricle) is typically greater than in the pulmonary circuit (right ventricle), causing oxygenated blood to flow from the right aorta through the foramen of Panizza into the left aorta. Small amount of deoxy blood mixing in left aorta
Describe blood flow through a crocodylian heart when submerged or basking
Basking: expanded capillaries reduce systemic pressure, so more deoxygenated blood is able to flow through the left aorta along with some oxygenated blood. Blood volume is increased in the systemic circuit to heat up faster
Submerged: blood is shunted away from the pulmonary circuit to increase oxygen efficiency when lungs cannot be used
What happens to the foramen of Panizza when the crocodylian is active? Inactive?
Open; closed
Why do crocodylians need their inter-aortal shunt?
They are homeothermic ectotherms, so already have a low metabolism. On top of that, they are sit-and-wait predators, so they need to be able to shunt so they don’t have to breathe as often
What are the differences between the therian circulatory system and the avian circulatory system?
Therian is left systemic artery, avian is right systemic artery
What are the similarities between the therian circulatory system and the avian circulatory system?
Everything except their right-left inversion
Why do therians have a right systemic artery and birds a left?
No specific reason, the selection pressures kind of just worked out that way
Why do therians and avians have such similar circulatory systems?
Both homeothermic endotherms (convergence on circulatory system = most efficiency (no shunts))
What are the clades in Crocodylia?
Crocodylidae, Gavialidae, Alligatoridae
How to tell the difference between gators and crocodiles?
Gators have a U-shaped snout, their top teeth cover their bottom teeth. Crocs have a V-shaped snout, top and bottom teeth both jut out
What is a gavial’s snout modified for?
Eating fish
What do ancient crocodylians show on their teeth
Wear (potentially from mastication)
Why do crocodylians not have distinct synapomorphies between each clade?
Adaptive radiation and fast evolution of some traits caused a lot of convergent evolution
What two things, when considered alone, do not determine evolutionary potential?
Morphology and molecular evidence
Provide three examples of “living fossils”
Coelacanth, tuatara, and crocodylians
Why do the “living fossil” species not entirely provide their evolutionary potential/background?
They are still currently evolving and diverged in their own way from their ancestors
Compare the difference between crurotarsal ankles and mesotarsal ankles. What clade shows each?
Crurotarsal: Calcaneus and astragalus not fused, so the ankle joint is between them, allows for more rotational freedom; Crocodylia
Mesotarsal: Calcaneus and astragalus are fused, so the joint is distal to them; Aves
Sprawling locomotion in crocodylians
Low energy, uses lateral undulation
Erect locomotion in crocodylians
High energy, but usually faster. May walk or gallop
Are crocodylian’s girdles efficient?
Yes! They allow for both a sprawling and erect posture
The secondary palate in crocodylians allows for:
Breathing while the rest of the body is submerged, which is important for their predation strategy
What predation strategy do crocodylians have?
Sit and wait
What are the bones of the crocodylian palate?
Premaxilla, maxilla, palatine (secondary bony palate)
The evolution of the secondary palate in crocodylians is convergent with:
Mammals
Can crocodylians masticate?
No, they must swallow their prey whole, so break up their prey by death-rolling
What are the two types of crocodylian vocalizations? What are they used for?
Bellowing and subsonic vibrations; courtship or a threat display
What were the osteoderms seen on the dorsal side of crocodylians selected for?
Shape + size selected for most vibrations possible in courtship displays (more vibrations = better fitness)
What is a type 1 survivorship curve? Provide an example
Offspring have high survivability until late life; elephants
What is a type 2 survivorship curve? Provide an example
Constant decrease in survivability over time; birds
What is a type 3 survivorship curve? Provide an example
Low survivability in early life until maturity; tortoises, sea turtles, crocodylians
What variable has the greatest effect on crocodylian sex ratio?
Temperature changes
How does crocodylian nest temperature change between 4.5°C and 8.5°C temperature increase?
Nest temperature increases with ambient temperature, where an 8.5°C increase has a greater impact
How does crocodylian sex ratio change between 4.5°C and 8.5°C temperature increase?
In 4.5°C, we see a rapid increase to almost all males in the population. In 8.5°C, we see the same, except a sharp change in the sex ratio now favouring females over males once a certain temperature is reached
How does crocodylian sex ratio change between more southern sites vs. more northern sites?
Same trend, but northern sites see an increase in the male vs female ratio a little later due to the temperature difference
Below 31.5°C and above 34.5°C, what sex is most common in crocodylians?
Female
Between 32.5°C - 33.5°C, what sex is most common in crocodylians?
Male
Based on the environmental sex determination temperatures seen in crocodylians, what type do they have?
Type II (females at extreme temps, males at intermediate temps)
What is significant about the Galapagos finches vs. the mainland finches?
The Galapagos finches are very very diverse due to adaptive radiation, but mainland finches don’t have as much diversity despite having the same amount of time to evolve and fill niches
What are the three big contributors to adaptive radiation in birds?
Their beak shape, habitat, and diet
Paleognathae
Possess an immobile palate, where the vomer and palatine are highly associated and the joint between the palatine and pterygoid does not move
Neognathae
Possess a mobile palate, where the vomer is reduced and the joint between the palatine and pterygoid is moveable
The moveable joint in Neognathae allows for:
Cranial kinesis
Which directions can the upper beak move in Neognathae?
Rostrally and caudally, as well as dorsally and ventrally
What does cranial kinesis in Neognathae allow for?
The filling of diverse niches (adaptive radiation)
What is the K-Pg boundary?
Meteor impact event
What was Galloanserae?
Primitive birds that had a neognathan palate, but they retained some primitive skull features
When did Neornithes rapidly diversify? Why?
After the K-Pg boundary; many ecological niches were left vacant due to the meteor impact that killed the dinosaurs, allowing Neornithes to fill those gaps and become super diverse
When did Galloanserae diversify?
Before the K-Pg boundary
What are the clades within Paleognathae?
Tinamidae (Tinamous), Rheidae (Rheas), Struthionidae (Ostriches), Apterygidae (Kiwis), and Casuariidae (Cassowaries, Emus)
When did Paleognathae diversify?
After splitting from Neognathae
Describe the Ratite tree before the discovery of ancient DNA in relation to the Moa
Monophyletic: The Moa was grouped with other large ratites due to their similar morphology
Describe the Ratite tree after the discovery of ancient DNA in relation to the Moa. What does this show?
Paraphyletic: The Moa is the sister taxon to Tinamous and is not as closely related to the other ratites as previously thought; shows convergence on large terrestrial birds
Apterygiidae
Small, flightless, and their eggs fill their entire body cavity
Rheidae + Casuariidae
Have quills on their arms, and fight using their feet, which have large, sharp claws. Some have casks on top of their heads
What is significant about the cask on the head of a cassowary?
Can be used to understand how dinosaurs developed their casks (none as a juvenile but grows over time)
Describe locomotion in Struthionidae
At slower speeds, their limbs are unloaded and force is exerted horizontally. At higher speeds, their limbs are axially loaded and force is exerted vertically, which is more efficient at greater speeds
The shorter the moment arm, _________
The more likely the joint is a snap joint
The longer the moment arm, _________
The more likely it acts as a regular muscle
Why are ostriches able to achieve such high speeds despite having such a high center of mass?
They have extremely efficient snap joints and increased area of the planar surface
How do Struthionidae increase the area of the planar surface?
Only have two toes, but each are covered in papillae that increase surface area
Why is ostrich locomotion so efficient?
Being acted on my sexual and natural selection (faster = better mate but also can run from predators)
What effects did tooth loss in birds have on other body systems?
Complete rhamphotheca (keratinous sheath over bill bone), and muscular gizzard with gastroliths and crop
What effects did the development of the muscular gizzard with gastroliths and crop have on other body systems in birds?
More efficient food processing and shift of center of gravity backwards and downwards
More efficient food processing in birds led to:
Homeothermy and endothermy (high basal metabolic rate)
Sustained active flight in birds was affected by:
Reduction in total body mass (skeletal lightening), homeothermy and endothermy, center of mass shifted back and down, and stronger flight muscles, extensive skeletal fusions, and tail reduction
What is significant about the K-Pg boundary?
Freed niches for birds to fill and diversify
After the K-Pg boundary, active sustained flight allowed for:
Diversification of modes of flight
After the K-Pg boundary, the complete rhamphotheca allowed for:
Diversification of beak shapes and uses (preening, diet, communication, thermoregulation, etc)
The origin of the rhinotheca (upper sheath) and gnathotheca (lower sheath) is homologous with:
The turtle beak
Large component of beak diversification caused by:
Differences in allometric growth
Positive allometry:
Body part increased relative growth to rest of body
Isometry:
Body part 1:1 growth rate
Negative allometry:
Body part decreased relative growth to rest of body
What are the important factors in beak diversification?
Allometry, development, size of the bird, foraging mode, and concerted interactions between other variables
What is a feather?
An ectodermal organ used in birds for many functions
What are the functions of feathers?
Flight, insulation (thermoregulation), courtship, sensation, contouring, predation,
What is a rachis
The central vein of a feather
What is a calamus
The part of the feather that inserts into the skin
What is a barb
A lateral branch from the rachis
What is a barbule
A branch from the barb
What are pennaceous barbs used for?
Colour deposition, structural colour, exposed to the environment
What are plumaceous barbs used for?
Soft filaments that make up the undercoat used for temp regulation
Feather type depends on:
Proportion of plumaceous : pennaceous barbs
True/False? Feathers have a unique genetic regulatory system compared to other ectodermal organs
False. Develop the same way
What are the five types of feathers?
- contour
- down
- semiplume
- filoplume
- bristles
Describe the anatomy of a contour feather
The barbs are asymmetrical (one side is longer than the other), and their barbules hook together with barbules from adjacent barbs to direct the flow of air during flight
Function of a contour feather
Flight
Ratio of pennaceous to plumaceous barbs on contour feathers
Many pennaceous, few plumaceous
What must contour feathers have lots of to function properly?
Surface area
Describe the anatomy of a down feather
Almost all plumaceous, very unorganized but hold lots of volume
Function of a down feather
Insulation
Why do diving birds have shorter down feathers than flying birds despite the fact they spend lots of time in cold water?
Shorter down feathers don’t hold as much air, so the bird is overall denser and is better at diving because it doesn’t have to fight the buoyancy of their air
Describe the anatomy of a filoplume
Very very small feathers with thin rachis and pennaceous filaments at the top
What are the functions of filoplume feathers?
Contouring (provide space between contour feathers for easier organization), sensation (allow birds to hear), and courtship (make vibrations)
How do peacocks use their filoplumes to attract mates?
They shake their filoplumes which emits <25Hz vibrations to attract mates
If filoplumes are clipped from the caudal tract, what happens?
Birds who signs of deafness
Describe the anatomy of a bristle
Rachis is mostly unbranched except for the bottom, which may have a few pennaceous filaments
What are the functions of bristles?
Sensation (like whiskers) and predation (funnel insects into mouth)
Are bristles a new trait in birds?
No, many different clades have them, which suggests their MRCA likely had bristles
Describe the development of a down feather
- Outpocket of the epidermis
- Invagination in the tissue around the outpocket
- Involution of the rachis to form barbs
- Barbules form
- Rachis forms
Describe the development of a contour feather
- Outpocket of the epidermis
- Invagination in the tissue around the outpocket
- Rachis develops
- Involution of the rachis to form barbs
- Barbules form
Why must the rachis form first in contour feathers?
Provides the structure for barbs
Why must the barbs form first in down feathers?
Require less organization than contour feathers, main focus is volume
What are feather tracts?
Areas set up to grow different feathers on different parts of the body
How fast is tract development in birds?
Very fast! Tracts are set up 4 days after neurulation
What does tetrachromatic mean?
Four colour cones instead of three
The fourth cone in bird’s eyes allows them to see:
UV light
Why are birds tetrachromatic?
They rely heavily on colours for communication, so they need a broader spectrum to operate with
What are the three types of colour birds use for their feathers?
- pigment
- structural
- iridescence
Describe pigment colour in birds
Pigment is deposited into the pennaceous filaments
Describe structural colour in birds. What colours is this used for?
The organizational pattern of molecules results in colours that would be difficult to produce with pigments; blues, purples, greens
Describe iridescence in birds. What colours?
Also structural, though the colour reflected depends on the angle you view them at; blues, purples, and greens
What are the ways in which birds care for their plumage?
- anting
- bathing
- preening
- molting
Describe anting in birds
They squish ant into their feathers, which acts as an anti-parasitic for ectoparasites
Describe bathing in birds
Bathe in either water or dirt to maintain their feathers
Describe preening in birds
They spread oil from their uropygial gland (found on the pygostyle) onto their feathers to protect and waterproof them
Describe molting in birds
They shed their feathers depending on the time of year, which is very energetically costly, so it’s under a lot of selection pressure
Describe molting in terms of thermoregulation
Density and mass of the feathers change depending on the season (degree of change depends what kind of feather)
Describe molting in terms of courtship
Mandarin ducks molt into a beautiful coat for courtship and dull coat any other time of the year
Describe how feathers aid in predation
Owls can fly almost silently because of the anatomy of their feathers and some herons use their wings to cover water to “calm” the fish before it attacks
Describe the flight feathers of owls that allow them to fly so silently
Fringed tail feathers, velvety exterior of feathers, and combs on the leading edge of the wings direct airflow in a way that makes owls fly almost completely silently
How are feathers used in courtship?
Bright colours, iridescence, and courtship behaviours are used to attract mates (speciation)
Why were birds able to achieve flight?
They have drastically reduced their mass by pneumatizing their bones
What is pneumatization?
Bone structure seen in birds where the majority of the bone is made up of air pockets
What are the four skeletal contributors to flight in birds?
- furcula (wishbone)
- keel
- synsacrum
- pygostyle
What is the purpose of the furcula?
Increased pectoral girdle stability
How was the furcula formed?
Fusion of the collarbones
What is the purpose of the keel?
Flight muscle attachment
What is the purpose of the synsacrum?
Acts as a counterbalance
What is the purpose of the pygostyle?
Holds the rectrices (tail feathers)
What are the four forces that act on birds during flight? Which direction does each act in?
- gravity (down)
- lift (up)
- thrust (forward)
- drag (backward)
Which forces inhibit flight in birds? Which allow for flight?
Gravity and drag; lift and thrust
Which forces can birds optimize in flight? Which forces can’t they optimize?
Lift, thrust, and drag; gravity
What do birds show a convergence on in relation to flight?
Wing shape (acts as an airfoil)
Describe how lift is generated
Air velocity on the dorsal side of the wing is faster, while on the ventral side is slower. Because the velocity is higher on the dorsal side, it is lower pressure, so the wing is lifted in the direction of the lower pressure (upwards)
What are the metrics of wings that impact drag and lift?
Aspect ratio and wing loading
Describe a high speed wing shape. Aspect ratio and wing loading?
Small, comes to a sharp point. High aspect ratio, low wing loading. Usually used for fast flapping (hummingbirds)
Describe an elliptical wing shape. Aspect ratio and wing loading?
Broad wing meant for short bursts of movement and not long flight. Low aspect ratio and high wing loading
Describe a high aspect ratio wing shape. Aspect ratio and wing loading?
Long and thin. Used in active/dynamic soaring birds and is very rarely flapped. High aspect ratio and low wing loading
Describe a slotted high-lift wing shape. Aspect ratio and wing loading?
Long and broad, used for passive/static soaring. Low aspect ratio and high wing loading
How is wing loading calculated?
Mass of bird/total surface area of the wing
What is wing loading?
A measure of how much mass each meter squared of the wingspan is responsible for in order to achieve flight
High wing loading means?
Each square meter is responsible for a high amount of mass
What can wing loading be related to?
Metabolic rate
How is aspect ratio calculated?
Wingspan^2/surface area of the wing
What is aspect ratio?
A measure of how much space there is under the wing for air to flow over (measures maneuverability)
High aspect ratio means?
Low maneuverability
What is the function of the primary and secondary feathers?
They function as independent ailerons (control pitch, yaw, and roll)
What is the function of the covert feathers?
They reduce turbulence
What is the function of the alula?
Increases air velocity above the wing to reduce turbulence
The downstroke of the wing is controlled by the:
Pectoralis
The upstroke of the wing is controlled by the:
Supracoracoideus
Which pectoral bones are involved in bird flight?
Keel, coracoid, sternum, and furculum
What is powered flight?
Active use of the flight muscles
What is passive flight?
Using air currents to generate lift instead of flapping their wings
What are the three divisions of powered flight?
- full/powered
- hovering
- flapping
Describe full flight
Wings are almost always flapping. Seen in large birds like geese
Describe hovering flight
An incomplete downstroke and figure 8 motion is used to generate lift on both the upstroke and downstroke. Seen in hummingbirds
Describe flapping flight
Used for high wing loading. Wings touch on the upstroke and downstroke and they create lift on both, which is necessary for high wing loading species. Seen in pigeons
Describe dynamic soaring
Takes advantage of gravity to generate speed and air currents above the ocean to generate lift without flapping. Very energy efficient. Seen in albatrosses
Describe static soaring
Uses static thermal columns to generate lift, and glide down from there until they need to get back up again. They will sometimes flap to generate more lift within the column. Seen in eagles
Describe the relative wing loading in increasing order for the four wing types
High speed < high AR < slotted high-lift < elliptical
Describe the relative aspect ratio in increasing order for the four wing types
Elliptical < slotted high-lift < high speed < high AR
Are pelycosaurs dinosaurs?
No
Are pterodactyls dinosaurs?
No
Are plesiosaurs dinosaurs?
No
What defines Dinosauria?
The pelvic girdle, which allows for an erect posture
What is special about the dinosaurian hip that allows for their upright posture?
It has a perforated acetabulum (hole that femur fits into)
Perforated vs imperforated acetabulum
Perforated has a hole where it joins with the femur, imperforated just has a divot/bowl
How is the femur oriented in crocodylians? What kind of posture does this give them?
Femur is lateral to the pelvis, which gives them a sprawling posture due to how the muscles attach (can’t physically become upright, one points ventrally, while the other points dorsally)
How is the femur oriented in dinosaurians? What kind of posture does this give them?
The head of the femur is offset, allowing the femur to be ventrolateral to the pelvis. This gives them an erect posture, as the muscle attachment allows for more stability for the upwards gait (both point dorsally)
What shape is the femur in dinosaurs that allows for their posture?
Head of the femur is offset, so it looks like an upside-down L
Which direction do the pubis and ischium point, respectively, in saurischian hips?
cranio-ventrally; caudo-ventrally
Which direction do the pubis and ischium point, respectively, in ornithischian hips?
Both point caudo-ventrally
Saurischia means:
Lizard-hipped
Ornithischia means:
Bird-hipped
Which clade gave rise to birds?
Saurischia
As the clades in Saurischia became more recent, what general trend can be seen?
A trend towards miniaturization, endothermy, and feathers
Describe why we see a gradual trend to miniaturization in contemporary carnivores
There is a wide range of meat variety to sustain every population
Describe why we see a sharp drop to miniaturization in carnivorous dinosaurs
It takes an enormous amount of resources to sustain large carnivorous dinosaurs, so they impede on other populations for food
Why were dinosaurs so much larger in the past than they are now?
The past was a lot warmer, thus there was more plant productivity, so herbivores flourished, so there was plentiful food for carnivores. It is much colder now, which decreases plant productivity and thus decreases the sustainable size of carnivores
Miniaturization is interplay between:
The changing climate and available resources
With a decreased body size, dinosaurs face increased _____________ and ____________, and retention of ___________________ need
Loss of heat; thermal conductance; homeothermic need
What is inertial homeothermy/gigantothermy?
The small SA/V ration permits retention of heat due to the sheer volume of the organism (maintains heat well)
Why was a shift towards endothermy seen in dinosaurs with dropping atmospheric temperatures?
As Ta decreases, miniaturization comes into effect, so heat is dissipated faster to the environment. In order to stay warm, maintaining heat from their metabolism was required
When was the evolution of feathers relative to the evolution of endothermy and trend to miniaturization?
As miniaturization became more prominent, feathers were evolved to insulate the body from the environment (could not rely on gigantothermy for heat retention). Endothermy evolved not long after that
What is the evidence used to argue for the existence of feathers before birds?
Integumentary filaments (proto-bristles) found on fossils, and osteological correlates show bumps on the bones where primitive feathers would’ve attached
List the features of Archaeopteryx that were important in determining its role as a stepping-stone to birds
- elongate digits to support flight feathers
- reduced caudal vertebrae
- pectoral girdle set up for powered flight (furcula)
- pubis directionality (points caudoventrally)
A fossilized feather from Archaeopteryx was discovered. What about its anatomy would suggest that it’s a flight feather?
- made out of mostly pennaceous filaments
- asymmetry of barbs (one side longer than the other)
- barbs are organized, as seen in contour feathers
List the features of Pygostylia that were important in determining its role as a stepping-stone to birds
- caudal vertebrae fused to form the pygostyle
From Pygostylia, what must change to get to modern Aves? What is the general trend in these changes? When did these features diversify?
- metacarpal fusion
- keel development
- coracoid modifications
- pygostyle modifications
- rectrices
- synsacrum
- edentulousness
Strengthen active flight; after K-Pg boundary
