Amniotes, reptiles and birds Flashcards
What are the 3 shared derived characteristics fo clade amniotes?
- Amniotic egg, direct development, internal fertilization
What does the amniotic egg provide and by which extraembryonic layers?
4 extraembryonic layers
- gas exchange - allantois, chorion
- nutrients - yolk sac, albumen
- protection from dessication - shell, amnion, chorion
Characteristics of amniotic egg shell?
- leathery or calcareous shell preventing dessication that is lost in mammals
- adaptation for laying eggs on land
- egg shells form internally after copulation and internal fertilization
How is internal fertilization achieved?
Intromittent organs are male genitaloa specialized to deliver sperm during fertilization.
- necessary for amniotic egg development
What are some other amniote adaptations for terrestrial life?
- thick, impermeable skin resistant to dessication
- axial skeletal muscle-powered lung ventilation (intercostals)
How are amniotes classified and what are the 3 classifications?
Based on number of temporal fenestrae in the post-eye area of the skull
Anapsid: none
Synapsid: 1 pair
Diapsid: 2 pair
Amniote phylogeny?
- monophyletic with 2 clades
Diapsids - reptiles
Synapsids - mammals
What are 3 characteristics of non-avian reptiles?
- skin protection and shedding
- reproductive adaptations
- circulatory system and thermoregulation
Skin structure of reptiles?
thick, dry keratinous scales that create a waterproof barrier
- highly resistant to dessication
- skin is shed in sections or all at once
What reproductive adaptations do reptiles have?
- lay eggs in leathery shells
- oviparous and lay eggs on land
- some are viviparous with a rudimentary placenta
- parental care is minimal except in crocodilians
Circulatory system and thermoregulation in reptiles?
- 3-chambered hearts
- ectothermic and behavioural thermoregulation
- lower metabolic rate results in reduced food and energy requirements
What are the 2 lineages of diapsids?
Lepidosaurs and Archosaurs (Pterosaurs, dinosaurs)
Turtles/Tortoise characteristics? feeding, anatomy, skeleton?
- herbivores or carnivores
- lay eggs on land
- anapsid skulls but descended from diapsids
- bony/cartilaginous shell made of dorsal+ventral shields fused to the vertebrae
- toothless beaks
- single intromittent organ
Lepidosaur characteristics?
– teeth fused to jaw and body covered in scales derived from epidermis
- scals are moulted
- hemipenis (paired)
- monophyletic with Tuataras and squamates
Tuatara characteristics?
- lack modified jaw structure of lizards
- no intromittent organ
- internal fertilization via copulation
Squamate characteristics? Lizard and snake characteristics?
- lizards and snakes
- loosely jointed jaws and skulls
- hemipenis
Lizards - external ears
- well-developed limbs (may be lost secondarily)
- insectivorous or herbivorous
- may be poisonous
Snakes - monophyletic legless lepidosaurs (seondarily lost)
- vestigial pelvic girdle retained in some species of snakes
- carnivorous: kill via venom or suffocation, swallow with loosely articulated jaw and elastic skin
Defining characteristic of archosaurs? 2 lineages?
socketed teeth not fused to jaw
- lost/replaced by beak in some lineages
Crocodilians and birds
Crocodilian characteristics?
- semi-aquatic, large predators
- elongated, flattened skull
- swallow prey whole
- single intromittent organ
- maternal care
Extinct archosaurs?
Pterosaurs
Non-avian dinosaurs: Herbivorous ornisthischians and carnivorous saurischians
What are theropods?
saurischian, bipedal carnivorous reptiles that couldn’t fly
Archaeopteryx characteristics?
- feathered and had wings for powered flight
- teeth, bony tail and wing claws
Theropod and bird similarities?
- hollow, thin-walled bones and skeletal similarities
- egg laying and brooding
- feathers homologous to theropod scales
- organ similarities in brain, heart and muscles
Bird phylogeny?
- monophyletic
- underwent rapid adaptive radiation after evolution of flight
- sister taxa with crocodilians
7 shared derived characteristics?
Wings with keratin feathers
Light-weight hollow bones
Tootless beaks
Adapted digestive system
Organ reduction
Endothermy
High metabolic rate, 4-chambered heart, complex respiratory system
