Exam 3 master set

Crocodylomorpha during the Triassic

most diverse group of mid and top level terrestrial predators

small, light, agile

Crocodylomorpha during Jurassic - Cretaceous

terrestrial and semiaquatic predators

Notosuchia characteristics

primarily terrestrial

lived in southern hemisphere, Gondwana

all extinct

Neosuchia characteristics

primarily semiaquatic

Laurasia origins (some Gondwana)

includes extant species

recurrent gigantism throughout evolution

extant Crocodylomorpha groups

Alligatoridae (alligators, caimans)

Crocodylidae

Gavialidae

Crocodylian general characteristics

laterally compressed tails and webbed hindfeet, - swimming

ears, eyes, nostrils on top of head - stalking

tapetum lucidum - low light sight

integumentary sensory organs in head - sensitive pressure sensors

parental care

Crocodylian nose structure

external nostrils + choanae (internal nostrils)

gular valve, secondary palate

characteristics of Crocodylian parental care

all mothers nest guard

babies vocalize in nest to synchronize hatching

parents or non-related adults guard the baby creche

general life history of turtles

oviparous

no parental care (few exceptions)

slow maturation

high juvenile mortality

structure of turtle shells

carapace = top shell

plastron = bottom shell

scutes = thin outer veneer, made of beta-keratin

vertebrae + ribs inside

limb girdles inside of ribs

archosaur hypothesis

turtles are a sister taxa to Archosauria within Diapsida

strongest support across phylogenetic studies on DNA

two lineages of extant turtles

Cryptodires (hidden-neck)

Pleurodires (side-neck)

Cryptodires - characteristics

bend neck in an S-shape into the shell

~75% of turtle species

every turtle species in North America

Pleurodires - characteristics

fold neck to the side under carapace

~25% of turtle species

used to be worldwide, used to include marine species

now, only occur in southern hemisphere

TSD - Type Ia

cold = males

hot = females

TSD - type Ib

cold = females

hot = males

TSD - type II

cold and hot = females

middle of the curve = males

is temperature sex determination or genetic sex determination more common in turtles?

temperature sex determination

Rhynchocephalia taxonomy

sister order to Squamata

Sphenodontidae - only extant family

Tuatara - only extant species

reached peak diversity in Mesozoic

Rhynchocephalia physical features

acrodont dentition

akinetic skull

paired outpockets of cloacal wall (homologous to hemipenes)

2 rows of teeth in upper jaw

groups within Squamata

lizards, snakes, worm lizards

reproduction in squamates

paired hemipenes in tail (not cloaca)

mostly oviparous

viviparous squamates use placentas

viviparity evolved independently over 100x

Lepidosaur organisms

tuatara, lizards, snakes

lizard skull structure, type of eating

built for crushing

strong skull, relatively stiff jaws

snake skull structure, type of eating

built for engulfing

less dense, flexible loose jaws

types of snake teeth

aglyphous

opisthoglyphous

proteroglyphous

solenoglyphous

structure of aglyphous teeth + type of snake

lacks grooves

teeth are same shape on maxillae (but can differ in size)

found in most non-venomous snakes

structure of opisthoglyphous teeth + type of snake

grooved fangs at the back of the maxillae

only found in Colubridae snakes

(harmless in North America, highly venomous in Africa)

structure of proteroglyphous teeth + type of snake

short enlarged hollow fangs, front of shortened maxillae

only in Elapidae snakes (highly venomous)

structure of solenoglyphous teeth + type of snake

hollow fangs at front of very reduced maxillae

long and foldable, stabbing

only in Viperidae (venomous)

processes involved in modern clade distribution

dispersal and vicariance

dispersal definition

connected populations share genes

vicariance definition

barriers to gene flow within an existing population leads to speciation

post-Pangaea herpetological lineage origins

salamanders - Laurasia

anurans - mostly Gondwana

reptiles - mostly Gondwana

Crocodylia - North America

direction of herp movement during Great American Herp Interchange

South America → North America

role of Central America during Great American Herp Interchange

acted as a filter between the continents; species on the move diversified in Central America before crossing over to the other continent

Wallace’s line description

a line drawn between Borneo and Sulawesi to indicate a geographical boundary that many species of animals do not appear to cross (delineates a separation between Asian and Australian fauna)

Triassic Faunal Turnover

shift from synapsids to Pseudosuchians and Rhynchosaurs

end of Triassic → shifted to Ornithodira

carnivorous dinosaurs diversify in Jurassic

Crocodylomorph ankle type

crurotarsal - flex back and rolls

Ornithodira ankle type

mesotarsal - restricted movement (only back and forth)

provides stronger backwards thrust

basal archosaur hip placement

horizontal from pelvis - legs on side of body

Dinosauria hip placement

vertical from pelvis - legs under the body

supports more weight and longer strides

pubis direction in Saurischians

extends forward

pubis direction in Ornithischians

extends back

two groups within Ornithodira

Pterosauria

Dinosauria

Ornithischia characteristics

pubis extends back (provides room for gut)

all herbivores

crests, horns, frills - complex society

groups within Ornithischia

Thyreophora

Ceratopsia

Pachycephalosauria

Hadrosaurs

Thyreophora characteristics

armored Ornithischians

Stegosauria and Ankylosauria

osteoderms in back skin, weaponized tails

Ceratopsia characteristics

horned Ornithischians

basal - bipedal, no horns or frills

derived - quadrupedal, horns and frills, male-male combat, social

Pachycephalosauria characteristics

helmeted Ornithischians

heavily thickened skulls

male combat

Hadrosaur characteristics

duck-billed dinosaurs

divided by presence or absence of hollow crest (resonance chamber)

crest is larger in males

some of first evidence of parental care

Saurischia characteristics

pubis extends forward

two groups - Sauropodomorpha + Therapoda

Sauropodomorpha characteristics

long necks, small heads

basal prosauropods - bipedal

derived sauropods - quadrupedal

largest ever terrestrial vertebrates

two groups of sauropods

Macronarians - reach up high to feed

Diplodocoids - grazed the ground

Therapoda characteristics

fast bipedal carnivores - hollow bones, 3 toed limbs

basal - small, lightly built

derived - 3 types

3 types of derived Therapods

Tyrannosauroids - predators of large prey, use jaws as weapon

Ornithomimosaurians - lightly built runners, catch small prey in hands

Maniraptorans - fast moving active feathered predators

sister diapsid groups

Lepidosauromorpha and Archosauromorpha

extant reptile groups (all within Diapsida)

Squamata

Rhynchocephalia

Crocodylia

Testudines

(technically, aves)

reptiles with temperature-dependent sex determination

most turtles

sphenodontids

some lizards

crocodylians

reptiles with genetic sex determination

all snakes

most lizards

some turtles

acrodont dentition (description)

derived form

on the acme (sits directly on top)

not often replaced

pleurodont dentition (description)

ancestral condition

staggered replacement

sloped towards the tongue

modified pleurodont dentition (description)

sloped towards tongue on the lip of the bone

special case in derived snakes

organisms with α-keratin skin

reptiles, amphibians, mammals

organisms with ß- keratin skin

only reptiles

purpose of ß-keratin skin

provides strength and rigidity

prevents disruption of permeable layers

scales - structure and purpose

folded areas of epidermis

ancestral tetrapod condition!

protects from abrasion and predation

DOES NOT prevent desiccation (skin lipids do that)

epidermis generation layers

ß-keratin = outer layer

α-keratin = inner layer

fluid layer - breaks down connections for shedding

lenticular sense organs (or scale organs) - structure and purpose

sensory organs in some scales

often have papillae - act as mechanoreceptors

columella

single inner ear bone in reptiles

hearing structure in snakes

quadrate-columella ligament

lower jaw → quadrate → ligament → columella

special vision structures in reptiles

scleral ossicles - anchor the muscles that change lens shape

colored lipid droplets - filter and focus light

snake eye structures

spectacle - transparent scale that protects the eye and focuses light

colorless lipid drops

tinted lenses - act like sunglasses, filter out blue light for diurnal snakes

processing center is in the thalamus

retina only expands/contracts to modulate light

NO ciliary muscles or scleral ossicles

mechanism of vision focusing in lizards and mammals

change lens shape

mechanism of vision focusing in snakes

move lens backwards and forwards (like a camera)

purpose of pit organs in snakes

specialized to detect infrared; sensitive enough to detect 0.001°C difference

Ichthyosaur timescale

appear in the Triassic

peak diversity in Jurassic

decline in the Cretaceous

Ichthyosaur characteristics

air-breathing fish eaters, live birth

hypocercal tail

have forelimbs and hindlimbs

basal form - lizards with flippers

derived form - lizard shark shape

event that preceded the appearance of ichthyosaurs

The Great Dying (the Permian-Triassic extinction)

2 types of Sauropterygia

Placodonts

Plesiosauria

Placodont timeline

appear, peak, and decline in the Triassic

Placodont characteristics

least changed from ancestral terrestrial form

lived in shallow water

crushed mollusks with tablet teeth

broadened gastralia, resembling turtle shells or horseshoe crab shells

Plesiosauria timeline

appear in late Triassic, live until end of the Cretaceous (K-T extinction)

Plesiosauria characteristics

live birth - some offspring 30-50% of mother’s length

contains 2 lineages: Pliosaurs (short necks) and Plesiosaurs (long necks)

marine diapsids in Squamata

Mosasaurs

Mosasaur timeline

appears in late Cretaceous

dominant marine predators while Ichthyosaurs + Pliosaurs declined

live until KT extinction at end of Cretaceous

Mosasaur characteristics

live birth, generalist predators

Varanid family

basal group - shaped like extant monitor lizard

derived group - heterocercal tail, small fins

marine crocodylomorphs

Metriorhynchid

Metriorhynchid timeline

appear in early Jurassic

disappear in early Cretaceous

Metriorhynchid characteristics

only marine archosaurs of the Mesozoic

heterocercal tail

short snout - eats other reptiles

long snout - eats fish

Ornithodira extinct lineages

Pterosauria

Dinosauria

1st flying vertebrates

Pterosaurs

2 types of Pterosaurs

Rhamphorhyncoids

Pterodactyloids

Rhamphorhyncoid characteristics

paraphyletic group, basal Pterosaurs

long stiff tail with rudder, some have teeth

Pterodactyloid characteristics

derived Pterosaurs

no tail, no teeth

independently derived traits, shared between Pterosaurs and birds

teeth reduced or lost

tail reduced or lost

keeled sternum

fused thoracic vertebrae

thin-walled bones

postcranial pneumatization

large eyes and cerebellum

issues with lateral undulation

compresses lung on one side → hard to breathe while moving

type of movement for early synapsids

sprawling walk (similar to alligators)

structural changes for synapsid movement

limbs moved from side to under body

loss of lumbar ribs, addition of diaphragm

function of the diaphragm in synapsids

divides the thoracic cavity: pulmonary cavity (lungs, heart) and abdominal cavity (liver, stomach, intestines)