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ZOOL 320 - CH 21
Synapsids and the Origin of Mammals
| Question | Answer |
|---|---|
| Who were the non-therapsid pelycosaurs? | Eothyrididae Caseidae Varanopseidae Ophiacodontidae Edaphosauridae Sphenacodontidae |
| 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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