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16 Cards in this Set
- Front
- Back
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Are PELYCOSAURS a grade or a clade?
What do they include? |
PELYCOSAURS are a grade. (THERAPSIDS are a clade).
Pelycosaurs are "mammal-like reptiles". (Clade THERAPSIDS include mammals). |
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What are the two derived lineages of PELYCOSAURS?
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EDAPHOSAURS: Herbivores
SPHENACODONTIDS: Carnivores |
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What are the sail fin differences in EDAPHOSAURS and SPHENACODONTIDS?
What does this tell us? |
Edaphosaurs have crossbars on sailfin bones.
Sphenacodontids do not; sailfin is also much smaller. This is a result of independent evolution. |
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What is the paleobiology of pelycosaurs?
How is this? |
All palycosaurs use sprawling limb posture.
The shoulder socket of the scapula is directed out towards the side. |
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What are the skull differenced in Pelycosaurs and Therapsids?
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Pelycosaurs have lots of "canine" teeth - Therapsids have a single large one.
Pelycosaurs' rear skull slopes forwards, Therapsids' rear skull slopes backwards. |
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What are the limb differences of pelycosaurs and therapsids?
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Pelycosaurs use a sprawling limb posture.
Therapsids are more upright. |
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What are the trends indicated by the differences in pelycosaur and therapsid skull differences?
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Larger brain and greater food processing ability.
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What is the trend for evolution of the jaw muscles in synapsids?
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Expansion and differentiation of the jaw closing muscles.
Differentiates from single jaw closing muscle (adductor mandibulae), to 3 different muscles for rotary motion. (Big fossa for Masseter and a wide zygomatic arch). |
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What is the trend for evolution of teeth in synapsids?
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Homodont dentition shifts to Heterodont dentition.
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How does synapsid evolution evolve for an active lifestyle?
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The formation of a secondary palate allows for breathing AND having food in the mouth.
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What is the trend for jaw bones in synapsid evolution?
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Jaw bones evolve into ear bones (Malleus and Incus). Trend to decrease postdentary bones & increase dentary size.
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What is the trend for limb posture evolution in synapsids?
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Pelycosaurs' use sprawling limb posture, which evolves into a more upright limb posture.
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What is the trend for tails in synapsids?
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Shortening of tail indicates shift of leg retractor muscle location from tail (big & heavy to drag around) to pelvis (butt muscles - GLUTEALS) - less to drag, more upright.
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What is the trend for rear ribs in synapsids?
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Loss of rear (LUMBAR) ribs = presence of DIAPHRAGM muscle (helps expand chest to bring in more air for breathing)
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What is the trend for nasal bones in synapsids?
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Nasal Turbinate Bones:
• Thin scrolls of bone in nasal passage covered with moist tissue • Warms & moistens air on way in, extracts water from warm air on way out. • Required increase in respiratory rate to supply oxygen • Lungs damaged by cold dry air |
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What are the 'need-to-know' trends of evolution in synapsids from pelycosaurs to therapsids?
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• Synapsid evolution shows trends to eat & process food more efficiently, move around more, and breath more efficiently
• SYNAPSIDS CHARACTERIZED BY INCREASING ACTIVITY & SHIFT TO ENDOTHERMY |
