Flashcards in Synapsida Lecture (Amniote cont.) Deck (54)
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1
synapsids have (temporal)
one pair temporal skull opening behind orbits
2
synapsids = first lineage to
diverge from ancestral amniotes (sister lineage to class w/ other amniotes "diapsids")
3
synapsids include
mammals (only extant lineage)
4
Evolution of mammals lineages (3)
pelycosaurs, therapsids, cynodonts
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Pelycosaurs are the
most basal synapsids
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pelycosaurs radiation
into diverse lineages (carnivores & herbivores)
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pelycosaurs extinct
by end of paleozoic
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pelycosaurs monophyletic or paraphyletic?
paraphyletic (therapsid lineage emerged w/in a carnivorous pelycosaur lineage)
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Therapsids radiation
into diverse lineages (carnivores & herbivores)
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therapsids persisted
into mesozoic
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therapsids monophyletic or paraphyletic?
paraphyletic (cynodont lineage emerged w/in therapsid lineage)
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Cynodonts exhibited (2)
- heterodonty = differentiation of tooth types
- changes in jaw musculoskeletal structure
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cynodont jaw musculoskeletal structure changes:
- enlargement of dentary & reduction of posterior bones of mandible
- evolution of masseter muscle = allows lateral jaw movements
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cynodonts monophyletic or paraphyletic?
paraphyletic (mammal lineage emerged w/in cynodont lineage)
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Early mammals arose
>200 mya (Triassic)
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early mammals exhibited (2)
- diphyodont deviation = teeth replaced 1x in life
- new jaw joint btwn squamosal & dentary = quadrate & articular incorporated (w/ stapes) into middle ear
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early mammal jaw & joint evolution
w/ time --> decrease in quadrate & articular, increase in dentary
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what forms the jaw joint?
quadrate, squamosal, & articular
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early mammals had ____ & were likely _________
hair, endothermic
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early mammals also had a
secondary palate = separates feeding & breathing pathways / permits suckling by young
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mammal hair
- unique to mammals
- dead cells w/ keratin
- epidermal structure
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derivatives of mammal hair (2)
- vibrassae (mechanoreception)
- spiny armor (porcupines, hedgehogs, & echidnas have all independently evolved spines derived from hair) (protection against predators)
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great morphological variation through dental evolution is due to
feeding specializations
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mammals have greatest variety of
glands among vertebrates
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mammal glands (4)
- sweat glands (evaporative cooling)
- scent glands (communications (attracting mates, territorial marking)) (defense (skunks))
-sebaceous glands (expel sebum - keep hair/skin pliable)
- mammary glands (possessed by females (rudiment in males)) (milk secreted from glandular tissue to feed young)
*humans --> adipose tissue around glandular tissue forms breasts (unique & plays role as sexual signal)
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mammary glands are homologous to
sweat glands
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Mammalia =
Monotremata + Metatheria + Eutheria
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monotremata reproduction
oviparous (lay & incubate eggs)
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metatheria reproduction
vivaporous w/ altricial young (born at early developmental stage) (babies w/ eyes that can't open yet)
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