CVA M2: Ch7 lecture notes

Remainder of Ch.3 + also Ch.7: The Skull

eureptilia

• diapsid skull design

• lepidosauromorpha- mesosaurs + turtles + fossils + snakes + lizards (parareptilia + lepidosauria)

• archosauromorpha- stem groups + thecodonts + crocs, pterosaurs, dinosaurs (ornithischians and saurischians) + birds

• archosaurs- crocs, pterosaurs, dinosaurs (ornithischians + saurischians), birds

• euryapsida- mesozoic marine reptiles (ichthyosaur + plesiosaur)

“euryapsids”

• ichthyosaurs + sauropterygia (plesiosaurs)

• believed to be paraphyletic 

• sharp teeth, could be big or small

• fish + deep sea squid specialists

• only 1 fenestration in skull, still diapsids though b/c covered up the other hole?

• teeth are continually growing + some fused to upper skull (not seen in mammals)

stem amniote: mesosaurs

• fully aquatic

• webbed feet

• laterally compressed tail

• anapsid skull

“parareptilia”/reptilia: testudinata 

• turtles + fossil groups

• anapsids

• carapace (top of shell), plastron (bottom of shell)

• dorsal skeleton fused to carapace 

  • less vertebrae in turtles compared to other reptiles

    

turtle shell

• for fossorial and aquatic lifestyles

• fused skull (fortified)

• shortened limbs

  • forearms stronger (for digging + swimming)

• digits shortened (sometimes webbed)- more strength 

• strong neck muscles (helpful for turtles ramming against substrate to help them dig)

• wide cervical vertebrae (enables to have an increase in SA for neck muscles to attach to)

• protection, later 

extant testudines

• austro-south american, afro-south american

  • pleurodira= “side neck turtles”

    • more vertebrae + long slender neck

    • can’t retract heads b/c neck too long

      • curve neck around to hide head 

    • fully aquatic + carnivorous

    • long neck to reach out and grab fish prey + have evolved suction feeding

• americas + europe, australasia 

  • cryptodira

    • variety of diets + locations where they live (more ecologically diverse)

    • many in US: semi-aquatic or fully terrestrial

    • turtles + tortoises (more dome shaped shell, live in drier enviornment)

reptilia: lepidosauria

• sphenodon + squamates

• synapomorphies:

  • overlapping scales- provides smooth feel

  • ecdysis- shed their skin (in fragments or whole)

  • hemipenes- paired copulatory structures in the males, 2 penises (base + it bifurcates)

  • tail autonomy- can lose tail and grow another one back

sphenodon

• sauropsida→ reptilia → diapsida→ lepidosauria→ ________ + squamates 

• tuatara, only found in NZ, 2 sp

• acrodont teeth (teeth fused to skull, lack roots), 2 rows of teeth

  • not deciduous 

• parietal gland @ top of head, allows to have strict circadian rhythm  

• males have big developed crest

squamates

• sauropsida→ reptilia → diapsida→ lepidosauria→ sphenodon + _________

• ~11k species

• lizards (~7000sp) + snakes (serpentes, ~3400sp)

serpentes

• sauropsida→ reptilia → diapsida→ lepidosauria→ squamates→ lizards + ________

• snakes

• ~3400 sp

• can be small (threaded snakes 6”) or v long (pythons 27-29ft)

• obligate carnivores (must eat other animals/meat to survive)

• synapomorphies:

  • elongate

  • limbless

  • scales

  • vestigial pelvis

    • not all, but some males have claws to scratch female to let her know to mate

    • remnants of hindlimbs, vestigial structure 

  • carnivorous 

  • kinetic skulls

  • recurved teeth 

synapsida

• gnathostomes→ teleostomi → sarcopterygii → tetrapoda →  amniota → sauropsida (eureptilia + parareptilia) + ______ (stem lineages + mammals)

• ~360mya 

• stem lineages (always extinct, closest relative to extant lineage we’re looking at) + mammals 

• 1 skull fenestration

  • jugal + zygomatic process of the squamosal 

stem mammal lineage: pelycosaurs

• late carboniferous→ early permian 

• diversity of diets: carnivores, herbivores (can tell through teeth + jaw size)

• sexually dimorphic, social animals, huge sail like fins across their bodies

• vary in size, long tails 

stem mammal lineage: therapsids 

• closely resembling current day mammals 

• early permian→ triassic 

• PT extinction → opened up more niches for them to roam

• synapomorphies:

  • slicing teeth

  • secondary palate= roof of mouth, can breath + eat at same time

  • nasal turbinates= light bony structures w/ soft tissues, help warm air animal takes in + works as cooling device

• reduced in size: dog→ weasel 

early mammalia

• late triassic (~250 mya)

• extant taxa: monotremes + theria (metatheria + eutheria)

• synapomorphies: 

  • hirsute (pelage=hair/fur, vibrissae=whisker)= hair growing off body (sensory structures)

  • mammary glands

  • heterodont dentition= dif types of teeth, in shape and function 

other mammalian synapomorphies

• sebaceous glands- gives off scent 

• anucleated red blood cells 

• tooth replacement + occlusion (proper alignment of teeth)

  • enables us to chew- upper + lower incisors match up to not wear out teeth 

  • not consistent, just replace teeth once

• middle ear→ 3 ossicles (incus, malleus, stapes)

  • enable us to hear sound v well in air

  • prior to this, terrestrial animals herd through reverberations in jaws 

monotremes

• gnathostomes→ teleostomi → sarcopterygii → tetrapoda →  amniota → synapsia→ mammalia→ ______ + theria (metatheria + eutheria)

• 5 sp

• platypus, echidnas 

• lack nipples

• lack external ears (still have 3 inner ear ossicles)

• egg layers 

metatheria: marsupials

• gnathostomes→ teleostomi → sarcopterygii → tetrapoda →  amniota → synapsia→ mammalia→ theria→ ______ + eutheria

• ~334 sp

• live birth

• pouch developers

  • opossums, koala, kangaroo, wombats, sugar glider, 

• altricial- young not fully developed when born, need more time w/ parent

  • crawl back into pouch to develop

• forelimbs well developed (bc they crawl back into pouch)

eutheria: placental mammals

• gnathostomes→ teleostomi → sarcopterygii → tetrapoda →  amniota → synapsia→ mammalia→ theria→ metatheria + ______

• us

• very diverse, on every continent 

• 18 lineages, ~4000 described species worldwide

• 40% of diversity from rodentia (1,600sp)

• edentata= oldest eutherians?

mammalian phylogeny- give examples of what animals are in which groups:

• monotremes: 

• metatherians (marsupials):

• eutherians:

  • edentata-

  • artiodactyla

  • cetacea- dolphins, whales 

  • perissodactyla

  • pholidota

  • carnivora 

  • chiroptera- bats 

  • insectivora

  • rodentia

  • lagomorpha

  • primates

  • scandentia

  • dermoptera

  • macroscelididae

  • tubulidentata

  •  hyracoidea

  • proboscidea

  • sirenia- manatees + dugongs

amniote skull terms

• anapsida- no fenestrations, ex: turtles

• synapsida- 1 fenestration, ex: humans

• diapsida- 2 fenestrations, ex: reptilia 

organization of skeletal tissue

• skeleton

  • exoskeleton 

    • keratinized- from epidermis (outer layer of skin)

      • ex: horns, scales, feathers

    • bony- from dermis (animals w/ bony sheath)

      • ex: armadillo, pangolin 

  • endoskeleton (deep w/in, helps propel us + allow us to move)

    • notochord- 1st endoskeletal component 

    • cartilaginous- 2nd component, protect/form canal for dorsal hollow nerve cord or ventral hollow nerve cord to go through? 

    • bony- 3rd component, can be dif degrees of mineralization 

or

• skeleton

  • cranial- everything @ head end 

  • post-cranial- everything after the head

    • axial- anterior to posterior axis

    • appendicular- shoulder + pelvic girdles + arms + legs, everything that juts-out?

cranial skeleton

1. splanchnocranium

2. chondrocranium 

3. dermatocranium 

(^developmental order)

splanchnocranium

• part of cranial skeleton

• derived from pharyngeal slits in protochordates 

• v soft tissue

chondrocranium

• part of cranial skeleton 

• neurocranium, protects brain, cartilaginous/endochondral bone 

• squishy bone, not mineralized, provides integrity + stiffness around chondrocranium 

dermatocranium

• part of cranial skeleton

• outer casing, dermal bone 

• diversity you see in skull comes from this