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Exam 3 historical geology exam

Terms in this set (58)

Pelycosaurs became extinct during the Permian and therapsids replaced them.
Therapsids displayed the
beginnings of mammalian
features:
- Fewer skull bones.
- Enlarged lower jawbone.
- Differentiation of teeth.
- More vertical legs.
- Possibly covered with fur. (*)
- May have been endothermic - warm blooded.
- They lived in cooler middle and
higher Permian latitudes, and
not just low latitudes.
Pelycosaurs (early
synapsids)
• long torsos and tails,
• sprawling legs typical
of cold-blooded
reptiles
• totally unrelated to
the diapsids we call
"reptiles" today
Pelycosaurs split into five families
• The Ophiacodontidae (above) were long-bodied, primitive, and perhaps even
aquatic - the earliest family.

Therapsids, mammal-like reptiles,
evolved from carnivorous
pelycosaurs in the Permian and
quickly evolved into herbivores
and carnivores.

Therapsids ("beast-holed faces").
• Jaw muscle holes were
rotated more upward than
those of Pelycosaurs.
• Upward AND outward
expansion in a single hole
• allowed the skull, mandible,
and brain to grow wider and
larger.
• The "squeezed brain" problem
was history.

larger brain allowed for more development of the
senses, including hearing.
• the rear bones of the jaw slowly began to shift
toward the ear canal, and developed into complex
structures to aid hearing.
• Marked the transition between the reptile's single
ear bone, and the three-boned inner ear of the
mammal.
• Therapsids, initially small and insignificant,
overran the still cold-blooded diapsids and spread
all over the Earth.
• Better hearing and sharper senses made these
creatures better hunters.