MAMMALIAN CLASSIFICATION PDF DOWNLOAD!
Class MAMMALIA Mammals are defined as vertebrates that possess hairs and mammary glands for feeding young. They also possess a four-chambered heart. Mammalia is a class of animal within the Phylum Chordata. Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is universally accepted; McKenna & Bell and Wilson & Reader provide useful recent compendiums.Molecular classification of · Standardized textbook · McKenna/Bell classification. Mammals are of different types and can be distinguished up into marine mammals, smaller mammals and larger mammals. Mammals belong to the class mammalia. Since mammals are of different types they are classified into three subclass based on their reproduction. They are Eutheria, Metatheria and Prototheria.
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Classification of mammals | Zoology and Entomology articles. IAS Zoology.
Since Simpson's classification, the paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics.
Though mammalian classification work gradually made Simpson's classification outdated, it remains the closest thing to an official classification of mammals.
The three largest orders in numbers of species are Rodentia: The next three biggest orders, depending on the biological classification scheme used, are the Primates including the apesmonkeys and lemurs ; the Cetartiodactyla including whales and even-toed ungulates ; and the Carnivora which includes catsdogsweaselsbearsseals and allies.
These were grouped into 1, generafamilies and 29 orders. In mammalian classification influential paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes echidnas and platypuses and therian mammals marsupials and placentals and all descendants of that ancestor.
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They were the dominant reptiles of the Permian Period million to million years agoand, although they were primarily predaceous in habit, the adaptive radiation included herbivorous species as well.
Therapsids tended to evolve a specialized heterodont dentition that is, a set of teeth separated into molars, incisors, and canines and to improve the mechanics of locomotion by bringing the plane of action of the limbs close to the trunk. A secondary palate was developed, and the temporal musculature, the muscle mammalian classification in closing the jaw, was expanded.
LystrosaurusTherapsids, such as Lystrosaurus, were mammal-like reptiles that thrived early in mammalian classification Triassic Period million to million years ago.
The several features that separate modern reptiles from modern mammals doubtless evolved at different rates.
Many attributes of mammals are correlated with their highly active habit—for example, efficient double circulation with a completely four-chambered heartanucleate and biconcave erythrocytesthe diaphragmand the secondary palate which separates passages for food and mammalian classification and allows breathing during mastication or suckling.
Hair for insulation is a correlate of endothermyor mammalian classificationthe physiological maintenance of individual temperature independent of environmental temperature. Endothermy allows high levels of sustained activity. The unique characteristics of mammals thus would seem to have evolved as a complex interrelated system.
Classification of Mammals
Because the characteristics that separate reptiles and mammals evolved at different rates and in response to mammalian classification variety of interrelated conditions, at any point in the period of transition from reptiles to mammals, there mammalian classification forms that combined various characteristics of both groups.
Such a pattern of evolution is termed mosaic and is a common phenomenon in those transitions marking the origin of major new adaptive types.
To simplify definitions and to allow the strict delimitation of the Mammalia, some authors have mammalian classification basing the boundary on a single characteristic, the articulation of the jaw between the dentary and squamosal bones and the attendant movement of accessory jawbones to the middle ear as auditory ossicles.
The use of a single osteological character allows the placement in a logical mammalian classification of numerous fossil species, other mammalian characteristics of which, such as the degree of endothermy and nursing of young and the condition of the internal organs, probably never will be evaluated.
It must be recognized, however, that were the advanced therapsids alive today, taxonomists mammalian classification be hard put to decide which to place in the Reptilia and which in the Mammalia.
MorganucodonThe extinct Morganucodon lived million years ago. Classification The higher classification of the class Mammalia is based on consideration of a broad array of characters.
Traditionally, evidence from comparative anatomy was mammalian classification predominant importance, but, more recently, information from such disciplines as physiologyserology the study of immune reactions in body fluidsand genetics has proved useful in considering relationships.
Comparative study of living organisms is supplemented by the findings of paleontology.
Study of the fossil record adds a historical dimension to knowledge of mammalian relationships.