Exam 1 Chapter 3C Flashcards
Modern members of Lepidosauria?
o Tuatara
o Anole lizard
o snek
3 hypotheses for turtle phylogeny
ANapsid, Archosuar, and Lepidosaur hyptheses
Anapsid hypothesis
: branched alone after reptiles
Archosuar hypothesis
hypothesis considered more, genetically clear, branches off in Archosauromorpha before birds and crocodiles
Lepidosaur hypothesis
branches in Lepidosauromorpha, right after synapsida
- most likely
Pelycosaurs
: Earliest synapsids - intermediate between the reptiles and mammals
Therapsids
Major group of synapsids: includes mammals, their ancestors and relatives
* Many of the traits today seen as unique to mammals had their origin within early therapsids
o Which group if ancestral to modern mammals?
therapsids!!
o Understand the various therapsid traits inherited by modern mammals
More mammalian-like than other therapsids
Modern mammals descended a group of cynodonts
Therapsids: cynodontia
Most likely underground to avoid environmental struggle
Retained features in mammals from therapsids
Five digits
Quadrupeds with less-splayed locomotion – legs under body
Two occipital condyles to articulate the skull with the first cervical vertebra
A secondary palate
A large dentary bone (mandible- lower jaw)
“Synapsid” means it had a single temporal fossa
Defining traits of mammals
o Mammary glands with nipples (nipples absent in monotremes)
o Hair
o Sebaceous and sweat glands
o A muscular diaphragm separates the thoracic and abdominal cavities
o Endotherms
Monotremes
ovaiparous/egg laying, have cloaca
Marsupials(metatheria)
most have marsupim/pouch for underdeveloped young when born
ex. kangaroo, opposum
Placental mammals
eutheria, most mammals
- baby develops in placental sack they gain nutrients from during growth and before birth
