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Mammology
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Mammalogy Kingdom Animalia Phylum Chordata -Subphylum Vertebrata (Craniata) -Class Mammalia Endothermic vertebrates with hair, mammary glands, 3 middle ear bones and other unifying features (see p. 53) Enucleate red blood cells, muscular diaphragm -Dentary squamosal jaw articulation 4 major themes in this book (and mamalogy) 1. Evolution 2. Scientific investigation 3. Mammalian diversity 4. Form and Function The field of mammalogy can be approached from many directions -ecosystem -as a resource -cellular -we are mammals -etc. -behavior Chapter 2 History of Mammalogy Starts, we assume with prehistoric humans and other hominids -mammals were food -mammals were predators -eventually, mammals were domesticated -mammals were even the subject of worships and religious rituals Whereas mammalogy had its beginnings in prehistory, as a scientific field we can trace it back to the Greek and Roman Philosophers. -Hippocrates (460-377BC) -Aristotle (384-322BC) -grouped animal “forms” and recognized whales and humans as mammals along with horses, cows, sheep, etc. Along with Pliny the Elder (23-79AD) Aristotle formed much of what was known about mammals (including mammals that do not and did not exist) well into the Middle Ages. Galen (AD 130-201) was am early Roman anatomist and probably one of the 1st to dissect mammals for scientific purpose. Mammalogy (and other sciences) did not advance much until at least the 1200’s and not substantially until the 1500’s with the exploration of the world be the Europeans Mark Catesby (1683-1749) described many of the mammals in the English colonies in what is now the SE US and Bahamas Georges Buffon (1707-1788) a Frenchman compiled (but did not actually write much of) the 44 vol. “Histoire Naturalle” in which he attempted to assemble all known facts about all animals Modern Taxonomy also had its beginnings during this time. John Ray (1627-1705) an Englishman defined a species and may have come up with an early form of the system Linnaeus popularized and developed. Carl von Linni (Carolus Linnaeus 1707-78) a Swedish botanist, is credited with developing the binomial system of nomenclature we use today. -His 10th ed. of “Systema Naturae” (1758) forms the basis for modern taxonomy -Also these species were grouped into a hierarchical arrangement species into genera, genera into families etc. -Many Naturalists were working throughout the worked. In North America, as young country began to expand, expeditious were sent out to map and explore the west. Thomas Jefferson (1743-1826) sent out one of the most important expeditions: (1774-1809) Meriwether Lewis and William Clark (1770-1838) in 1804-1806. -Lewis and Clark discovered and brought back many new organisms, including mammals. Mammals that Lewis and Clark “Discovered” included -Not really but brought to the attention of science -pronghorn, grizzly bear, and prairie dogs Also sent by Jefferson- Zebulon Pike (1779-1813) traveled throughout the west and southwest and actually was far more famous in his day than Lewis and Clark. Trappers, fur traders, army officers, and RR people all contributed to early mammalogy in the North America. Many of these early records, particularly those of the fur trading companies, are invaluable data bases even today! Thomas Say (1787-1843) was a surgeon naturalist on several army expeditions. Spencer Fullerton Baird (1823-1887) was associated with the R’s and helped found the US National Museum (Smithsonian) and published a very important monograph. -“General Report on North American Mammals” (1859) -Descriptions of 730+sp. of mammals. C. Hart Merriam (1855-1942) initiated a publication; “North American Fauna” refined techniques in mammalian taxonomy (including emphasis on cranial traits and teeth), helped form the Bureau of Biological Surveys (1905) and served as the 1st president of the American Soc. Of Mammalogists it was formed in 1919. Museums have been important to mammalogy since the earliest times (e.g. the great natural history museums of Europe) and continue to be important centers of study. “Our ability to study various mammalian systems or to work on the systematic and phylogeny of a particular group of mammals depends on the continued existence and mainterrance of these museum collections.” p.17 Charles Darwin (1809-1882) while not considered a mammalogist, contributed greatly to mammlaogy through his collections and through his theory of evolution through natural selection (1858) (which was indendently developed by Alfred Russell Wallace 1823-1913) considered to be the father of modern geology. Emergence of Mammalogy as a Science -As I have already discussed began with the Greek Philosophers. -HOWEVER, clean up to the 1800’s most scientists studied multiple taxa and it really wasn’t until the late 1800’s and early 1900’s that mammalogy emerged as a distinct discipline. American Soc. of Mammalogist was formed in 1919. -Most centers of mammalogy formed around major museums at Harvard, Yale, Michigan, Cornell, Kansas, Texas Tech, and UC Berkeley. Joseph Grinnell (1877-1939) was at VC Berkeley -Prime force in mammalogy and W.J Hamilton (1902-1990) at Cornell As the 20th Century progressed, mammalogy moved out of the museums into many different areas. -Medicine, game mgmt, behavior, ecology, conservation, genetics, physiology, etc. -Medicine, and game mgmt nothing new Chapter 3 Methods and Techniques We will go over this chapter in the Lab. Chapter 4 Evolution and Dental Characteristics Mammals evolved from reptilian ancestors during the 100 million year period from the late Paleozoic to the early Mesozoic era. -See the time line Table 4.1 to put it into perspective. Mammals came from synapid (S.C) reptiles that 1st appeared in the late Paleozoic (~320-mya) in N.A. -2 Major orders -Pelycosauria -Therapsida- mammals come from these -See Fig. 4.2 and 4.12 The Pelycosaurs were common and relatively diverse and included both carnivorous and herbivorous forms. -One suborder, Sphenacodontia, which included the famous sail back “dinosaurs” (not really dinosaurian) such as Dimetrodon is believed to have given rise to the Therapsida sometime during the Permian, which eventually replace the Pelycosours and were much more mammal-like The Therapsida can be divided into 2 suborders: -Anomodontia- were the dominant terrestrial herbivores for 60 million years -Theriodontia- primarily carnivorous and much more diverse than anonrodaonts -Included the very successful Cynodontia which gave rise mammalian -had a secondary palate and complex cheek teeth Cynodontia existed for ~70 million years from Triassic to Jurassic periods and diversified into both carnivorous and herbivorous forms. -Cynodonts share many features with mammals including: 1. Tricuspid Vdentition and double rooted 2. Jaw structure- increases dentary size 3. Modification of 1st 2 vertebrae into the atlas/axis complex 4. Similar phalanges and many others -Also, more erect posture legs underneath rather than sprawling movement -Increased adaptability in feeding Life other vertebrates, the story of mammals is one of locomotion and feeding. The transition between the mammal-like reptiles and mammals is fairly well-documented in the fossil record through tooth, jaw, and cranial elements -For example, in reptiles and mammal-like reptiles, jaw, and articular bones. -See p.53 Table 4.3 Comparison of Reptiles and Mammals -Late an additional joint formed between the cranial squamosal and the surangular bones of the jaw. The changes in jaw articulation were concurrent with changes in ear structure particularly middle ear bones membrane to inner ear. Mallwus is derived from the articular bone Incus is derived from the quadrate. There are 2 Alternative Hypothesis for the origins of mammals Fig. 4.7 Mammals may be monphyletic or polyphyletic (if we believe the Monotremes arose independently). The 1st mammals (p.48) -Remember, by most accounts (unless you are an extreme supporter of punctuated equilibrium) the transition from reptiles to mammals was gradual. But once we have something defined as a mammal (dentary- squamosal jaw art.) what were these early mammals like? -For the most part, during their 1st 100 million years, mammals were a rare and insignificant part of the terrestrial fauna. -They were small (usually smaller than modern squirrels), uncommon (relatively) and probably nocturnal. -Very little niche overlap between these early mammals and the dinosaurs. E.g. mammals and the dinosaurs were larger than the largest mam. for ~140 million years and it wasn’t until the extinction of the dinos. That mammals grew to larger sizes and diversified. -Talk about niche overlap and competitive exclusion. The classification and relationships among the early mammalian Mesozoic groups is uncertain (see Fig. 4.8 and Table 4.2) “Prototheria”- considered a subclass by some and Order Monotremata is often placed in here, although there is no clear evidence that they belong here (see Fig. 4.8, Table 4.2 and p.170). Several important early Prototheria include: -Morganucodontids- may have been ancestral to monotrium -Triconodonta- includes, small carnivores teeth similar to later therians -Docodonta- probably omnivores -Multituberculata -had rodent-like incisors -herbivores These are all mammals -Although they had both a dentary-squamosal and quadrate articular jaw articulations -Cheek teeth differentiated into premolars and molars Theria -Arose at the same time as the Prototheria (Triassic) see Fig. 4.8 -Order Symmetrodonta (Kuehneotheriidae) was probably a sister group to the Prototherian Morganucodontids. -Camivores and insectivores -Often called “Pantothesis” -Order Eupantotheria- omnivores “A significant feature of pantotheres was their molars, which had 3 principal cusps in triangular arrangement (a tribosphenic molar- the basic pattern for most later mammals) Advanced therrans probably originated from the eupantothere family Peramuridae middle Cretaceous. Tribosphenic Molars -Early mammals as well as some of their synapsid reptile ancestors, had tooth cusps arranged longitudinally. The Therians have a tribosphenic (tutubercular) molar which allowed for both shearing and grinding of food. See Fig. 4.10 -Upper molar has 3 cusps collectively called the Trigon (Fig. 4.10 C&D) -Lower molar has also has 3 cusps (known as Trigonid, Fig 4.10A) but also has a “heel” or shelf called the Talonid (Fig 4.10 A&B) There can also be smaller “accessory” cusps in addition to the # main cusps. “During occlusion, a crushing or grinding action occurs as the protocone of upper molar contacts the talonid basin of the lower molar. Food is not only crushed but also sheared. This is believed to be the ancestral condition and can still be seen in some marsupials and insectivores, but has been highly modified (derived) in other mammals.” For example with the addition of a 4th cusp, molars of many modern mammals (humans) have become squarer. -quadritubercular -these teeth allowed much more efficient processing of food necessary for endothermy. -modified in most groups The great diversity of modern mammals (metatherians and cutherians) had its beginnings in the early Cenozoic era. WHY? 2 Major Events 1. Extinction of dinosaurs -Opened new “adaptive opportunity” 2. Brealcup of Pangea -Continental drift allowed major genetic differentiation of the various phylogenetic lineages to proceed in relative isolation (See Fig. 4.11) Other factors also important e.g. floral diversity also increased at this time. Most modern families date from before the Miocene As stated earlier, most of the mammalians adaptations relate to feeding and locomotion; However, these factors in turn are related to endothermy and its increased metabolic demands. Mammals necd ~10x more food and O2. Look over the summary and comparison of mammal-like reptiles and mammals on p.52-3 and Table 4.3. Biology and Ecology We will go into some of the characteristics of modern mammals in a little more detail now in the rest of Chapter 4 and in the following chapter on: -Integument, support, and movement (chp.5) -Food and deeding (6) -Nervous and endocrine systems (7) -Adaptations to a wide variety of environments (8) -Reproduction (9) Dentition “Teeth are one of the most important aspects of living (and extinct) mammals.” Occur in 3 bones -Premaxilla -Maxilla -Dentary Tooth morphology- See Fig. 4.17, p.56 -Crown-above gum line -Roots- below “ “ surrounded by cementum- has annli -Enamel overlays dentine -One of the hardest vertebrate tissues -Crystalized calcium phosphate -Dermal-Dentine -Rodents have enamel only on anterior surface Pulp cavity within dentine has blood and verves -Open (ever growing) vs closed (stop growing) rooted teeth Tooth socket is an aloveolus Edentate mammals often have teeth develop and resorb as embryos We went over the types of teeth in lab- incisors, canines, premolars, and molars. The hete4rodont dentition of most mammals is highly variable. Crown Height -Low crowns- brachyodont (omnivores and carnivores) -High crowns-hypsodont (herbivores) Occlusal surfaces -Bunodont- rounded cusps -Lophodont- continues ridges or lophs -Selenodont- lophs isolated and crescent shaped -Carnassial (sectorial) teeth- shearing cutting -Last upper premolar,1st lower molar Usually when one set of teeth is being used, the others are not (e.g. when an animal chews with cheek-teeth its incisors do not come together) WHY? -Gays in teeth (i.e. lost teeth)-diastema Diphyodont Mammals usually have 2 sets of teeth- “middle” teeth are deciduous and replaced by permanent ones -In most, replacement is vertical, but in elephants and manatees tooth replacement is horizontal. Dental formulas- went over this in Lab. -In eutherians the ancestral formula is 3/3, 1/1, 4/4, 3/3 = 44 -Metatherians- 5/4 1/1 3/3 4/4 = 50 END OF UNIT 1 UNIT 2 Structure (form) and function Integument- adapted for; 1. Need to retain H2O 2. Need to retain body heat Also serves a variety of other functions -Protection -Camouflage -Behavior and sexual selection -Secretes scents, oils, H2O, and milk -Others See Fig.
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