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93 Cards in this Set
- Front
- Back
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Amniotes Structure |
Name refers to three extra embryonic membranes A. Amnion B. Allantois C. Chorion * In placental mammals the membranes found in the egg have been modified. -embryo is still surrounded by an amnion filled with amniotic fluid. - allantoic and yolk sac become the umbilical cord. |
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Monophyletic group |
- Arose from amphibian like tetrapods in the early carboniferous period of the Paleozoic era (363 MYA) |
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Hylonomus |
- one of the best known early amniotes |
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Hylonomus lyelli |
Only species in genus. - Disarticulated skeleton found in Nova Scotia by John William Dawson - Lived entirely on land - Ancestor of lizards, crocodiles, turtles and birds - Represents earliest known reptile. |
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Late Carboniferous Amniotes diverged into two major groups |
1. Sauropsida A. Anapsida B. Diapsida 2. Synapsida |
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Anapsids |
- " no arch", no opening behind eye - The most primitive reptiles known - Often referred to as "stem reptiles" - Represented today by turtles |
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Diapsids |
- "two arches" two openings behind the eye. Diverged from the anapsids in late Pennslyvanian Gave rise to all living reptiles other than turtles |
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Synapsids |
"fused" two openings fused to one opening, one opening behind eye Group finally gave rise to the mammals A. Pelycosauria B. Therapsida * Different skull structure than early anapsids - Temporal openings |
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Pelycosaurs |
- Most primitive - Pelvis shaped like a bowl Gr. Saur, lizard - Referred to as bowl lizards - Earliest, most primitive synapsids - Dominant land animal for 40 million years |
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Pelycosaur Examples Family: Ophicodontidae |
Ophiacodon: "snake tooth" Named by Othniel Charles Marsh- 1878 - One of the most basal synapsids - Lived from late Carboniferous to Early Permian in N. America and possibly Europe *Once thought to be semi-aquatic, it most likely lived on land |
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Pelycosaur Examples Family Edaphosauridae |
Edaphosaurus "pavement lizard" -First described by Edward Drinker Cope - 1882 *One of the earliest known large herbivorous amniote tetrapod |
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Pelycosaurs
Family Sphenacodontidae |
Most closely related to therapsida (the group that includes the mammals) Dimetrodon: "two-measured teeth" Possessed both shearing teeth and canine teeth. |
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Therapsida |
"mammal-like" - exhibited so many characteristics of mammals. |
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Two groups of Therapsida |
1. Anomodonts 2. Theriodonts |
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Anomodonts |
Dicynodonts Most numerous, diverse, and long-lived anomodonts Dicynodon "two dog-teeth Herbivorous Toothless except for prominent tusks Probably cropped vegetation with a horny beak, like a tortoise. Tusks may have been used for digging up roots and tubers |
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Theriodonts |
Primarily carnivorous One group of theriodonts that gave rise to mammals is Cynodontia Cynodonts existed for 70 million years, throughout the Triassic to middle Jurassic period |
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Cynodont characteristics |
1. Dentition changed to tricuspid and double-rooted cheekteeth 2. Increased dentary bone size with reduction in postdentary bones 3. Development of glenoid fossa on the squamosal bone 4. Modification of the atlas/ axis complex 5. Modified pectoral and pelvic girdles. 6. More erect posture 7. Development of the masseter muscles |
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Example of a cynodont |
Thrinaxodon About the size of a fox Found in S. Africa and Antarctica Semi-sprawling posture, an intermediary form between the sprawling position of pelycosaurs and more upright posture in current mammals Probably carnivorous, feeding on insects, small herbivores and invertebrates. |
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Probainognathus |
Gr. "progressive jaw" - Carnivorous cynodont in S. America - Posterior extension of the dentary.
- Adjacent surangular articulates with the squamosal, forming a new jaw joint lateral to the persistent reptilian joint between the articular and quadrate. |
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Earliest mammals |
Tritylodonts - "three knob teeth" - Most specialized of the herbivorous cynodonts - Skull is very mammalian in general appearance - Dentition gives them a rodent-like appearance. - One pair of incisors is greatly enlarged, but the canines are not developed. |
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Morganucodonts |
"Glamorgan teeth" - considered to be cynodonts - insectivorous and nocturnal - seeking prey while avoiding predators that were usually active by day - equipped with a "double-joint" jaw the articulation was made up of the 1. dentary-squamosal joint 2. quadrate-articular joint |
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Why do some consider the Morganucodonts to represent the earliest mammals? |
1. Dentary-squamosal joint 2. Teeth differentiate into incisors, canines, premolars and molars. 3. Two occipital condyles were present 4. Pelvic region distinct from the reptilian pattern 5. Mammalian posture. |
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Multituberculata |
- Name refers to the molariform teeth with up to 8 large, conical cusps. - Posterior lower premolar was often very large and was used for shearing - Longest lasting group of mammals (120 Million years) - Multituberculates and eutherian mammals coexisted for more than 70 Million years - Mainly herbivorous but also ate seeds, nuts and fruits |
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Ptilodus
Arboreal adaptations: |
1. Prehensile tail 2. joints of the tarsus and pes are modified to permit the foot to be reversed in the manner of squirrels, which allows them to descend the trunk of a tree headfirst. * Because of the narrow pelvis they probably gave birth to tiny, undeveloped young that were dependent on their mother for a long time. |
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Ptilodus skull |
Composed of an enlarged, shearing posterior lower premolar. |
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Is the origin of mammals monophyletic or polyphyletic? |
Two different interpretations 1. In the early Jurassic period, a single lineage of therapsids gave rise to early mammals. 2. Two or more therapsids lines independently achieved the mammalian grade of organization. * Different interpretations drawn from a fragmentary and incomplete fossil record. |
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Monophyletic |
Most authorities consider mammals to be the taxa sharing the single dentary bone with a squamosal-dentary articulation and their common ancestor. |
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Polyphyletic |
The characteristics of the three major mammalian groups evolved at different times and are viewed as a convergent evolution, then mammals have a polyphyletic origin. - monotremes - metatheria - eutheria |
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Cenozoic Era |
66-201 MYA |
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Two major groups of terrestrial carnivores of Cenozoic Era |
A. Ancestors of the modern order Carnivora
B. Order Creodonta *Both groups modified the posterior cheek teeth to form specialized shearing surfaces- carnassials. |
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Carnassials |
Creodonts - M1 and /or M2 and m2 or m3 Carnivora - P4 and m1 |
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Order Creodonta |
Term coined by Edward Cope in 1876. Existed from the Paleocene to the Miocene epochs (66-11 MYA). First large obviously carnivorous mammals. Shared a common ancestor w/ members of the order Carnivora. Found in N. America, Eurasia and Africa |
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Two families of Creodonta recognized |
1. Oxyaenidae Carnassials composed of M1 and m2. 2. Hyaenodontidae Carnassials composed of M2 and m3. |
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Family Oxyaenidae |
Patriofelis ferox (L. "father cat") Fossil collected in the Bridger Basin of southern Wyoming - Full-grown black bear with a head almost the size of an adult male lion |
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Family Hyaenodontidae |
Hyaenodon ("hyena-toothed) - Some species of this genus were among the largest terrestrial carnivorous mammals of their time. |
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Family Hyaenodontidae |
Sinopa ("fox", Native American word blackfoot) One of the smaller members of the family.
Fossil found in Wyoming |
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Order Carnivora |
No consensus on the classification. Two broad patterns are seen. 1. Suborder Feliforma Felids, hyaenids, viverrids, herpestids 2. Suborder Caniformia Canids, ursids, procyonids, mustelids, mephitids, ailurids, odobenids, otariids, and phocids. |
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Three basic morphotypes of cats |
1. Conical-toothed cats - Upper canines are short and unserrated. - Round in cross-section. 2. Saber-toothed cats A. Scimitar-toothed cats
B. Dirk-toothed cats
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Two types of Saber-toothed cats |
A. Scimitar-toothed cats Canines are short and broad and may have very coarse serrations. Ex. Machairodus B. Dirk-toothed cats Canines are long and slender with very fine or no serrations. Ex. Barbourofelis |
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Nimravidae |
- Often referred to as "false saber-toothed cats". - Not related to the true cats (family Felidae) - Lived between 40 and 7 MYA. - Cat-like appearance with shorter legs and tails than are typical of cats. - True cats have an auditory bulla divided by a septum. Nimravids either show an ossified bull with no septum or presumably a cartilaginous bulla that was not preserved. |
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Nimravidae
Dinictis |
Dinictis Endemic to the plains of N. America from about 37,2 to 20.4 MYA. Dinictis walked plantigrade, unlike modern felidis. It was a predator Named by Joseph Leidy in 1854. |
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Nimravidae Barbourofelis |
Barbourofelis - Probably the most famous nimravid - Endemic to N. America, living from 13.6 to 5.3 MYA. - Barbourofelis fricki was the last of the nimravids. It was about the size of a modern lion. - It possessed some of the largest teeth of all time. |
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Proailurus |
"first cat" - First animal recognized as a cat. - Lived in Europe in Asia approximately 25 MYA. - Compact and small animal, just a little larger than a domestic cat, weighing about 20 lbs. |
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Pseudaelurus |
- Probably evolved directly from Proailurus - Ancestor of today's felines as well as the extinct machairodont saber-tooths. - Originated in Eurasia and was the first felid to reach N. America about 18.5 MYA |
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Family Felidae
Subfamily Felinae |
Living and fossil conical-toothed cats. |
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Felidae Subfamilies |
1. Felinae Living and fossil conical-toothed cats after Pseudaelurus 2. Subfamily Machairodontinae "saber-toothed" Saber-toothed subfamily Not ancestors of living cats. Endemic to Asia, Africa, N. America, S. America and Europe Living 23 MYA to about 11,000 years ago. |
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Smilodon fatalis |
- Found in the Le Brea Tar Pit - Only found in N. and S. America - Went extinct about 10,000 years ago. - Dirk-toothed cat |
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Machairodus |
- scimitar toothed cat. - Found in Europe, Asia, Africa and N. America - Some species were as large as lions |
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Saber-teeth evolved four times in what groups? |
1. Nimravidae 2. Felidae 3. Creodonta 4. Thylacosmilus, a marsupial |
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Biogeography |
Study of patterns of organisms, including both extant and extinct species. *Zoogeography is a subdivision of biogeography. |
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Historical biogeography |
- Changes in species ranges over evolutionary time. - What is the ancestral distribution? - Where did the species originate? - Where are its closest living relatives? - How has the distribution been influenced by geological events such as continental drift? - Of special interest is endemism and disjunct distributions. |
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Ecological Biogeography |
- What features of the environment restricts species to their present range? - Species ranges is the complete area of the Earth over which individuals of particular species occur. Often inferred from museum specimen records. Ranges are dynamic, changing over time as a consequence of abiotic and biotic factors. - How is their distribution influenced by climate, environmental features, and other organisms? - What determines the number of species (species richness) in an area? |
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Father of Biogeography |
Alfred Russell Wallace 1823-1913 - 1876 Divided the world into the faunal regions. |
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Wallace's Faunal Regions |
- Nearctic - Neotropical - Ethiopian - Palearctic - Oriental - Australian - Oceanic |
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Wallace's Line |
Separates the Oriental region from the Australian region. There is a sharp break in faunal composition between the islands of Bali and Lombok and extending north along the Makassar strait. - This separation was due a deep trench in the strait that was impassable regardless of the water levels. |
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Great American Biotic Interchange |
Cretaceous- Paleocene dry-land connection between N. America and S. America.
Connection lost but island arcs were probably intermittently available between S. America-Antilles-Yucatan Peninsula from the Eocene to the present. Islands pushed up by the Caribbean tectonic plate. Early Miocene (23 MA)- most of Central America came into existence as the Chortis tectonic microplate and Middle American arc combined and moved into place from the west. |
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When was the Isthmus of Panama established? |
Late Pliocene * As far as is known, none of the endemic S.A. carnivorous metatherians crossed the land bridge. The only S.American terresterial predator to reach N. America was Titanis, a 3 meter tall, flightless phorusrhacid bird, in the Early Pliocene before the land bridge was formed. |
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Two groups of mammalian participants in the interchange |
1. "Waif immigrants" 2. Mammals that dispersed across the Panamanian land bridge at various times after its emergence |
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Waif immigrants |
Dispersed along the island arc in the late Miocene and Early Pliocene. A. Megalonychidae- sloths B. Mylodontidae- extinct ground sloths Dispersed from S. America to N. America |
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Did the mammals that dispersed across the Panamanian land bridge disperse well? |
Initially dispersed was equal in both directions. But later it was very unequal. S. America taxa - diversified little in N. America N. America taxa - radiated explosively in S. America throughout the Pleistocene. |
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Beringia |
- Area of land between modern day Alaska and Russia (Bering Strait). - Name after Vitus Bering, a Danish explorer for the Russian czar 18th century. - The Bering-Chirikob expedition explored the waters of N. Pacific between Asia and N. America |
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History of Beringia |
Ocean levels rose and fell several times in thepast. During extended cold periods,tremendous volumes of water are depositedon land in the form of ice and snow, which cancause a corresponding drop in sea level. Thelast “ice age” occurred around 12-15,000years ago. During this period the shallow seasnow separating Asia and North America nearthe present day Bering Strait dropped about300 feet and created a 1,000 mile widegrassland steppe, linking Asia and NorthAmerica together with the “Bering LandBridge”. |
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What was Beringia like? |
- Cold - Arid - Short grassland with areas of bare ground - Climate drier than today - Relentless winds buffeted the steppes - At times the climate was apparently cold temperate and permitted the survival of animals not adapted to arctic conditions - at other times it was arctic and barred their passage. |
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Mammals in Beringia? |
Large: Mammoths, bison, horses, musk oxen, saiga antelope Small: voles, lemmings, shrews |
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Mammals that immigrated to N. America through Beringia? |
Grizzly Bear Moose Bison (Bison priscus, now extinct) |
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Refugia |
Circumscribed areas within a larger biomewhich preserve biodiversity during periods ofenvironmental change. |
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Nunataks |
Refugia within the continental icesheets of glacial periods, were ice-free pocketsof variable size. In them, remnants of thepreglacial biotas survived until the iceretreated. |
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Examples of mammals that survived the driftless area during the last glaciation |
- Franklin's ground squirrel - Least weasel |
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Ecogeographic "Rules " |
1. Island Rule 2. Bergmann's Rule-1847 3. Allen's Rule-1877 4. Gloger's Rule-1833 5. Rapoport's Rule-1982 |
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Island Rule |
Small mammals on islands tend to have larger body size than their close relatives or ancestors on the mainland (insular gigantism) Large mammals show the opposite trend, with island species usually smaller than their mainland counterparts |
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Bergmann's Rule |
1847 - Carl Bergmann - German anatomist - Body sizes of mammals and birds tends to increase with increasing latitude. - Original explanation was based on the superior heat-conserving capacity of large-bodied endotherms |
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Allen's Rule |
1877 - Joel Asaph Allen - American mammalogist - Mammals and birds living in cold climates have shorter appendages than do their close relatives in warm climates. |
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Gloger's Rule |
1833 - Constantin Gloger - German zoologist - Originally referred to plumage colors of closely related birds and the humidity levels of their habitats. - Darker forms more frequently found in humid environments and lighter forms in dry areas. - In mammals the rule would apply to pelage color. |
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Rapoport's Rule |
1982 - Eduardo H. Rapoport - Argentinian ecologist - The latitudinal breadth of species ranges in mammals tends to increase from the equator to the poles. - Results from species' response to a relatively broad seasonal range of environmental conditions and are able to expand their geographic ranges accordingly. |
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Cursorial Adaptations |
Appeared early in the Cenozoic history of mammals *Enhanced by the expansion of the grasslands in the Miocene. |
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Three types of Calcaneum (heel bone) |
1. Plantigrade (human foot) 2. Digitigrade (Canine) 3. Unguligrade (Ungulates, horse, deer, etc.) |
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Pronghorn tarsal bones |
Calcaneum is no longer a weight bearing bone. Astragulus is now the weight bearing bone. Calcaneum remains important as a point of insertion for extensors of the foot. Astragulus is now acting as a double pulley and limits lateral movement. |
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Running speed is determined by what two factors? |
1. Stride length 2. Stride Rate = the number of strides/ unit time |
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Stride Length |
1. Elongation of the limbs - Probably the most important adaptation - The longer the limb, the longer the stride 2. Foot posture - Unguligrade-lengthens the limb 3. Role of the shoulder - Reduce/ eliminate the clavicle - Reorient scapula to side of a deep narrow chest - Shoulder joint now moves in the sagittal plane. 4. Role of the spine - Spine ungulates in the vertical plan - Animal extends back only hind feet are on the ground. 5. Muscle Mechanics - The most motion for the least shortening. - Muscles can move the joints through wider angles when they insert close to the joints than when they insert farther away. (The closer the muscle attaches to the joint the more flexibility. |
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Other Anatomical Adaptations for Running |
1. Reduction in limb mass • Reduction in abductor, adductor androtator muscles. • Lose lateral toes. • Fuse metapodials into a cannon bone. 2. Strengthening of hinge joint by splines andgrooves. 3. Springing Ligament (horse) |
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Automimicry |
- replication of patterns present in conspecific individuals at homologous sites or elsewhere on the body. |
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What skeletal structure defines a mammal? |
Dentary squamosal joint forms to define a mammal |
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Amniotes |
Organisms which have developed an egg that is quite similar to an aquatic environment.
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Pelycosaurs to mammal changes |
1. Size of temporal fenestration (holes) 2. Lower jaw and jaw joint 3. Bones for middle ear form 4. Formation of double occipital condyle 5. Development of a secondary palate. 6. Posture of the limbs straightened up and rotated 7. Change in shape of pectoral girdle. 8. Change in pelvic girdle 9. Atlas axis joints. (allowed for tilting of the head) |
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Chatacteristics of mammals |
1. Skin Glands 2. Hair (except for whales or porpoises) 3. 4 Chambered Heart (not just mammals, also birds) 4. Left aortic arch 5. Enucleated erthrocytes at maturity 6. Muscular Diaphraghm 7. Viviparous, bear their young alive 8. Highly developed neopallum (outermost part of the brain) 9. Loop of Henle in the kidneys- can change the concentration of the urine. 10. 7 cervical vertebra 11. Growth of long bones cease 12. Mandible is a single bone 13. 3 Middle ear ossicles 14. Double occipital condyles 15. Development of secondary palate 16. Heterodont dentition vs. Homodont dentition 17. Diphyodont dentition 18. Pectoral girdle redesigned 19. Pelvic girdle redesigned |
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Differing Dentition Characteristics of mammals Thecodont Acrodont Pleurodont |
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Dental Formula |
I (Incisor) C (Canine) P (Premolar) M (Molar) |
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Human Dental Formula |
2/2 1/1 2/2 3/3 = 32 - Numerator represents upper teeth in order of ICPM - Denominator represents the lower teeth also in order of ICPM |
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Simple to Tribubercular dentition |
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Modifications of molar teeth |
1. Tubercular - Designed to piercing exoskeletons 2. Bunodont -(hills or mounds) designed to grind away material between uppers and lowers 3. Lophodont, enamel and dentin present 4. Selenodont , looks like moon when seen from above. 5. Sectorial, L. sector "one who cuts" "scissors", cdesigned for shearing |
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3 structural layers of Hair |
- Unique to mammals 1. Medulla, center of shaft 2. Cortex, surrounds the medulla, lightly packed cells 3. Cuticle, outside of the cortex. |
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Classification of hair |
1. Based on growth patterns A. Angora- grows continuously B. Definitive- grows to a certain length and stops 2. Based on the functional type A. Vibrissae B. Pellage 3. Color |
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Three types of molting |
1. Postjuvenile Molt 2. Annual Molt3. Seasonal Molt |
