Synapsids and the Origin of Mammals

Question Answer
Who were the non-therapsid pelycosaurs? Eothyrididae
The earliest known pelycosaurs (but not most primitive). Medium-sized with long, slender heads, reflecting semi-aquatic fish-eating habits. Late Carboniferous to Early Permian of North America and Europe. Ophiacodontidae
Large (pig-size) herbivorous forms. Middle Permian of North America and Europe. Caseidae
Large-size herbivores, some with a sail. Early Permian of North America. Edaphosauridae
Large-size carnivores, some with a sail. Early Permian of North America and Europe. Sphenacodontidae
lower temporal fenestra synapsida
snout deeper than wide eupelycosauria
reflected lamina of angular bone. retroarticular process of articular turned downward sphenocodontia
reflected lamina of angular deeply notched. upper canine in larger maxilla. limbs held more under body and slimmer, temporal fenestra enlarged. therapsida
had sails from greatly enlarged neural arches. supported skin that was vascularized, for thermoregulation. both primitive endaphosaurs and derived shpenacodontids
A sphenacodontid that toy manufacturers misidentify as a dinosaur. longer thinner legs than other eupelycosaurs, but held out horizontally. Dimetrodon
coronoid process on dentary theriodontia
temporal fossa open dorsally euthriodontia
parital bony secondary palate. postcanine teeth with anterior and posterior accessory cusps. masseteric fossa on dentary. double occipital condyle. cynodontia
primitive therapsids. both herbivores and carinivores. reflected lamina of angular deeply notched. upper canine in maxilla, slightly reduced in herbivorous form. dinocephalians
another primitive therapsid, lasted until late Triassic. teeth highly reduced except or upper canines as tusks. toothless beak as cutting surface. dicynodonts
jaw point enabled lower jaw to slide back and forth against upper jaw for crushing dicynodonts
increase in number of sacral vertebrae form 2-3 in pelycosaurs to 4 more. has coronoid process on dentary but still has forelimbs extending outward from the body. Gorgonopsian theriodont
partial bony secondary palate. differentiated teeth with incisors, canine tooth, cheek teeth with cusps. cynodont characteristcs
bowing out of zygomatic arch. lumber ribs reduced or lost. distinct calcaneal heal. expanded iliac blade. cynodont characteristics
in their pelvis, muscles to move femur downward and backward originate on tail. pelycosaur
in their pelvis, muscles originate on ilium and insert on greater trochanter of femur. mammals
an intermediate between pelycosaur and mammal, with more laterally oriented head and with greater trochanter. cynodont femur
have reduced coracoids, reduced clavicle and interclavicle. acromion process first appears. therapsids
lateral head of humerus incipient in cynodonts evolution mammalian humerus
mammalian phalangeal formula of 2-3-3-3-3 first appears in cynodonts
secondary palate formed from premaxilla and maxilla bones before mammals
enalarged temporal opening of skull. differentiated dentition with large canine and cusped cheek teeth. secondary palate extending to palatine bone. Cynognathus
Size of small dog. large dentary forming most of lower jaw. double occipital condyle. spine along front of scapula. extended ilium of pelvis. Cynognathus
reflected lamina of angular=tympanic bone.
quadrate=incus; articular=malleus.
manubrium=retroarticular process of articular.
jaw joint into middle ear
quadrate and articular bones were loosely connected to skull and lower jaw. they may have been hearing with their lower jaw cynodonts
quadrate and articular bones were loosely connected to skull and lower jaw. they may have been hearing with their lower jaw cynodonts
May have had a diaphragm as do mammals cynodonts
loss of lumbar ribs and tapering of thoracic ribs like mammals. cynodonts
rod-like ilium, loss of postorbital bar betwen orbit and temporal fenestra, slender zygomatic arch, bony wall between eyeballs, enlarged nasal cavity. tritylodonts, herbivorous probainognathans
dentary/squamosal jaw articulation. double rooted postcanine teeth. specialization of braincase. mammalia
brain enclosed at side only by combination of prootic, opisthotic, and epipterygoid. primitive synapsids
3 cusps in line teeth of primitive mammals
holotheria, triangular arrangement of cusps mammalian teeth
early Jurassic mammal with premolars and molars Morganucodon
still had angular and articular bones in lower jaw. early mammals
sister group of synapsida is the sauropsida
synapsids are among the most primitive amniotes
synapsid synapomorphy of lower temporal fenestra bounded by postorbital and squamosal bone
provides space for expansion of contracted muscle snd better site for attachment of origin of adductor muscle. fenestra

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