amniotes - chpt. 9.2-9.3, 13

batrachomorphs

amphibians + relatives

reptilomorphs

all other tetrapods

what groups are included in amniotes?

mammals, reptiles, birds

what are the 6 amniote synapomorphies? 

1. Amniotic egg

2. Keratinized skin

3. New ankle bone (Astragalus)

4. Two or more sacral vertebrae 

5. Costal (rib-mediated) breathing 

6. Elongation of neck + trachea

how to distinguish between synapsids and sauropsids

temporal fenestration 

what era did reptilomorphs + batrachomorphs arise? 

carboniferous period 

what are the names + functions of the 4 extraembryonic membranes? 

1. yolk sac - connects to gut tube 

2. amnion - fluid-filled sac that surrounds + cushions embryo

3. chorion - outer membrane (against shell or uterus), aids gas exchange

4. allantois - connects to end of gut tube, gas exchange + stores waste 

what is the function of the shell found on some amniotic eggs?

prevents dessiccation of embryo + porous nature of shell allows for gas exchange

Why must shelled eggs be laid on land?

amniote embryos have no gills for breathing underwater 

keratin 

protein

alpha keratin 

hair, horns, and nails (helical structure); found in mammals

beta keratin 

feathers + scales (pleated-sheet structure); found in reptiles + birds

astragalus

ankle bone - increased stability

costal (rib-meditated) breathing

contraction of muscles between ribs, pulls ribs out + forward to aid in inhalation 

• increases volume of chest cavity decreasing pressure, forces in air 

intercostals

ribs

temporal fenestrae

number of holes on each side of the skull 

anapsid

0 fenestra

diapsid

two fenestra on each side

synapsid

one fenestra on each side (mammals)

what are the two major amniote groups + what era did they arise in?

1. sauropsids

2. synapsids 

during carboniferous period

what characteristic makes turtles unique

have a secondarily derived anapsid condition

what is the function of temporal fenestrae

bigger jaw-closing muscles + increased bite power 

what did ancestral tetrapod locomotion look like? 

lateral bending - interferes w/ breathing, can only inflate one lung at a time

what does sauropsid locomotion look like? 

bipedality - walk on two feet w/ legs directly under body 

• axial muscles no longer required 

• lateral bending still main locomotion for lizards

what does synapsid locomotion look like?

most are quadrupeds; upright posture + flex up and down, inflate both lungs at once

name lung type of synapsids + describe them 

alveolar lungs: numerous levels of branching w/ tidal airflow 

name lung type of sauropsids + describe them 

faveolar lungs: unidirectional airflow through lungs over faveoli + fewer levels of branching 

what are faveoli? 

pocket/chambers for gas exchange

describe lung type of birds + crocdilians, and describe how they work 

parabronchial lungs; 

• air enters primary bronchus 

• flows into dorsal secondary bronchus (dorsobronchus)

• flows into parabronchi + moves past faveoli for gas exchange 

• flows into ventral secondary bronchus (ventrobronchus)

• exits through primary bronchus 

heart of synapsids vs. sauropsids

crocs, birds, mammals - complete separation of oxygenated + deoxygenated blood w/ complete septum; 4-chambered heart 

most reptiles - partial septum, usually functions as 4-chambered heart under normal conditions 

skin of synapsids vs. sauropsids

synapsids: smooth skin w/ hair made of alpha keratin 

sauropsids - scales, beaks, claws, and feathers formed w/ additional beta keratin protein 

what glands do synapsids have in their skin? 

sweat + milk (in females) glands; allows direct maternal care w/ milk 

excretory system of sauropsids vs. synapsids

sauropsids - urinary bladder reabsorbs water

• short tubules in nephrons

synapsids - nephrons reabsorb water

• urinary bladder only for storing urine

• longer tubules in nephrons

compare nitrogenous wastes of fish, synapsids, and sauropsids

fish - pure ammonia

synapsids - convert ammonia to less toxic urea

sauropsids - create uric acid, semi-solid paste; requires most energy to make but same most water

compare vision of synapsids vs. sauropsids 

synapsids - generally poor vision 

• rods = main photoreceptors 

• 2 cone types (blue, green)

  • primates = 3 (red, blue, green)

sauropsids - good color vision 

• cones = main photoreceptors

• 4 cone types (red, green, blue, UV)

what describes the condition of the turtle skull in terms of the number of temporal fenestrae found? 

ancestors of turtles has diapsid skulls, but today turtles exhibit a secondarily derived anapsid skull

true or false: are the scales on reptiles + the fur on mammals considered homologous structures? 

true 

what does “endothermal ectotherms” mean?

ectotherms that sometimes employ endothermal strategies to raise their body termperatures

what is the function of turbinate bones found in mammals + birds? 

ensure air entering respiratory tract is warm + moist. reduce water loss when air is exhaled