BIOL 329 Lecture Notes - Lecture 27: Herbivore, Synapsid, Dimetrodon
6 May 2018
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Lect 27
MAMMALS – ORIGIN, SPECIES DISTRIBUTION
Native: 136, Introduced: 13, Terrestrial: 120, Marine: 30 spp.
Cetacea, Carnivora, Rodentia, Lagomorpha (rabbit), Insectivora (mole/vole thing), Chiroptera (bats),
Artiodactyla (mountain goat), Perrisodactyla (horse), Didelphimorphia (opossum – delphi = wob,
Primates.
Synapsida gave rise to Therapsida which gave rise to mammals. Diapsids diverged into others (reptiles,
birds, etc.)
Synapsids: monophyletic group originating in the Carboniferous. First group of amniotes that diversified
– before diapsid radiation. Most abundant tetrapods in the Paleozoic. Body 10-500 kg. Pelycosaurs
(sailbacks: Dimetrodon: vascularized sail on the back (first evidence of endothermy)) = first radiation and
predominantly in the northern hemisphere (Laurasia): warm, moist. Elongated neural spines – heavily
vascularized and probably thermoregulation. Both carnivorous and herbivorous. Had sprawling limb
posture, long toes, lumbar ribs. Lower and upper jaw were largely homodont (all teeth the same) apart
from a canine tooth – first evidence of tooth differentiation. Expansion of the dentary and reduction of
the other teeth led to the jaw size seen in mammals today.
Therapsids thera = wild beast. Early Peria, differed in having a very large temporal fenestra and
differentiation of teeth into incisors, canines and post-canine teeth (heterodont) – differentiation from
Pelycosaurs. First development of arched-palate – separate mouth and nasal passages – able to chew
and breathe at the same time (unlike Pelycosaurs).
Pelvic and pectoral girdles and limbs thinner and joints more flexible, short foot and toes relative to
Pelycosaur. Limb position shifts for increased upright posture. Hind limb movement by muscles to iliac
blade rather than to lateral processes
Therapsids: reduction in number of cervical vertebra to ~7. Reduction in ribs. Higher number in
Pelycosaurs.
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Document Summary
Native: 136, introduced: 13, terrestrial: 120, marine: 30 spp. Cetacea, carnivora, rodentia, lagomorpha (rabbit), insectivora (mole/vole thing), chiroptera (bats), Artiodactyla (mountain goat), perrisodactyla (horse), didelphimorphia (opossum (cid:858)delphi(cid:859) = wo(cid:373)b(cid:895), Synapsida gave rise to therapsida which gave rise to mammals. Pelycosaurs (sailbacks: dimetrodon: vascularized sail on the back (first evidence of endothermy)) = first radiation and predominantly in the northern hemisphere (laurasia): warm, moist. Elongated neural spines heavily vascularized and probably thermoregulation. Had sprawling limb posture, long toes, lumbar ribs. Lower and upper jaw were largely homodont (all teeth the same) apart from a canine tooth first evidence of tooth differentiation. Expansion of the dentary and reduction of the other teeth led to the jaw size seen in mammals today. Early per(cid:373)ia(cid:374), differed in having a very large temporal fenestra and differentiation of teeth into incisors, canines and post-canine teeth (heterodont) differentiation from.
