Synapsids (14 And 15) Flashcards
What are the five lineages of amniotes?
Turtles, crocodiles, birds, ‘lizards’ & snakes, and mammals
What are the major groups of synapsids? And what is the order of evolution?
‘Pelycosaurs’, Therapsids, Cynodonts, and Mammalia.
(In order listed)
What are key features of ‘Pelycosaurs’?
Reptiles that arose in the Carboniferous, single temporal fenestrae. Carnivorous and Herbivorous.
What are the key features of Therapsids?
Replaced Pelycosaurs, evolved in the early Permian, dominant until end of Triassic.
What are the two therapsid groups?
Dinocephalians and Cynodonts
Key features of Dinocephalians?
Heavy skulls, trend toward more erect limbs
What are the key features of Cynodonts?
Mammal-like reptiles, late Permian and Triassic, evolved jaw musculature.
Adductor differentiates into masseter and temporalis muscles.
What are the differences between Cynodonts and Pelycosaurs?
Pelycosaurs
One occipital condyle and sprawled posture (limbs extend out from body)
Cynodonts
Double occipital condyles and Limbs brought under body
First mammal characteristics?
Arose in late Triassic
Endothermy with enlarged brain for better hearing and smell
Mammary glands, extended parental care, large brain/body size ratio, hair
What bone makes up the lower jaw of fossil mammals?
The Dentary
Specialized teeth in mammals?
Incisors, canines, premolars and molars
What is the difference between early and modern ideas of dinosaurs and mammals?
Traditional
Early mammals were small, they persisted among dominant dinosaurs without diversification into new lineages, evolved after extinction of dinosaurs
Modern
Mammals started to diverge before the KT extinction and continued to diverge
Is it true there was increased diversification of living mammals after the loss of dinosaurs?
Yes
What are the living groups of mammals?
Monotremes, Metatheria (Marsupials), and Eutheria (Placentals).
Features of sebaceous glands?
- alveolar gland
- oily secretion often with hair
- waterproof hair and protect skin from drying
Features of sweat glands?
- tubular glands
- secrete water, salts, urea
- some important for thermoregulation
Features of mammary glands?
- develop from clump of cells in the ectoderm during embryonic development
- number and location of nipples varies across species
- provide nutrition for young offspring
Features of sweat glands?
- some derived from sebaceous glands, other from sweat glands
- defence, sexual selection
What are epidermal derivatives in modern mammals?
- claws, hooves and nails
- horns
- hair
-antlers
What is the only dermal derivative in modern mammals?
- osteoderms -> armadillos (exceptionally thick dermis)
Features of Monotremes?
- hair, endothermy, suckling of young
- lack nipples
- ex. Platypus
Features of Marsupials (Metatheria)?
- give birth to tiny young who suckle until the grow much larger, often in a specialized pouch of the mother
Features of placentals (eutheria)?
- most divers and widespread
- prolonged gestation of embryo in uterus with placenta
- distribution correlate with isolation of continents
What played a major role in the diversification of mammals?
Geological events (continental drift) and climatic events
