AD Mammals Flashcards
Describe some mammalian characters found in extinct and extant taxa
Presence of three ear ossicles Presence of cochlea Secondary palate well developed Vertebrae divided into: cervical, thoracic, lumbar, sacral, and caudal Hair
Mammalian inner-ear bones evolved from
modified ancestral (reptile-like*) jawbones
Describe a reptile vs mammals jaw bone
Reptiles:
- Jaw joint composed of articular (lower jaw)
and quadrate (upper jaw)
- Only one ear ossicle, the columella
Mammals:
- Articular and Quadrate bone incorporated
into middle ear as ossicles: Malleus and
Incus (which articulate with the innermost
Stapes, the Columella).
- Dentary and Squamosal bones form the jaw
joint
How did the mammalian jaw and middle ear evolve?
- Simplification of the mandible: tooth-bearing Dentary bone increased in size relative to the postdentary elements
- Integration of elements of the ancestral cranio-mandibular jaw joint into the ossicular chain:
• unique middle and inner ear morphology: capable of more sensitive sound detection
Mammalian middle ear evolved independently in at least three mammalian lineages by detachment from the mandible, but
the emergence of a secondary jaw joint is a key innovation that unites all mammaliaforms
• Miniaturization may have provided a selective regime for the evolution
of the mammalian jaw joint, followed by the integration of the
postdentary bones into the mammalian middle ear
(Lautenschlager et al. 2018).
What are synapsids?
not reptiles, but a phylogenetic
group that includes mammals and early
mammal-like lineages
Was the mammalian ear driven by feeding, not hearing? Discuss
• not simply an ‘‘improved’’ single-ossicle middle ear that was found in
stem amniote vertebrates
• is a “radical and fortuitous new development that owes its origin more to changes in feeding patterns than to hearing”: happened to
transmit higher-frequency sounds better than single-ossicle middle ears and
• enabled the evolution of the high upper-frequency hearing limits of
most mammals.
Extant mammals are characterized by two
salient features
What are these?
• hair and mammary glands.
– Neither of these are directly preserved in fossils
Describe the Order Cetacea
whales, dolphins, porpoises • Highly specialized for aquatic lifestyle • Most are marine, some live in freshwater • Many are highly intelligent and social • Broadly separated into “toothed whales” and “baleen whales"
Whales are mammals. Describe how
• Warm-blooded • Have hair, lungs, placenta, & produce milk • Bear live young • Two nasal passages (with 1 or 2 blowholes) • Have arm, wrist, & finger bones, & some with vestigial pelvis / legs • Tale moves vertically
Why are fossils important?
Fossils can provide a great deal of information: • Complete skeletons are rare, but even a single bone can yield important information • Fossils can reveal more than just age, anatomy, and identity … • … also diet, locomotion, senses, physiology, habitat, and more!
What are the 3 major reproductive categories?
Monotremes
• Egg-laying mammals
Marsupials
– Embryos born early, then nursed from inside
mother’s pouch (e.g., kangaroos)
• Placentals
• Embryos develop inside the womb, receiving nutrients and
O2 from the mother via the placenta
• Newborns are fed milk from mammary glands
Describe rodents
• Nearly 50% of mammals are rodents • Have no canine teeth, but two very larger incisors • Almost all are herbivores – Ex. Mice, Squirrels, Beavers
What is a hominid?
Modern humans & our direct and indirect ancestors since our lineage split from the chimpanzee
Describe hominid evolution
upright posture evolved before large brains
Foramen magnum: opening on the undersides of our
skulls
• Anterior (rather than posterior) placement evolved
several times independently in mammals
What is Out-of-Africa theory?
assumes that archaic Homo in
different places of the world was
replaced by H. sapiens from
Africa
What is multiregional theory?
assumes that archaic Homo in
different places of the world
developed independently into
H. sapiens
