EVOLUTION OF HORSES.   Term Paper ID:28254 Click to get this paper

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Paper Abstract: Analysis of fossil records & new investigative technologies with differing findings on evolutionary development of horses. Paper Introduction: A Cladogenetic View of the Early Evolutionary History of Horses Abstract Drawing upon the theoretical and empirical literature, this report describes evidence obtained from the fossil record supporting the anagenetic view of the horse phylogeny and its early evolutionary development. The anagenetic perspective advances the notion that a gradual microevolutionary process has occurred within a species. This view is also associated with a phyletic transformation from ancestral to descendant species. The fossil record for horses presents, in general, a progressive replacement of one genus with another without a strong indication of temporary overlapping. However, the literature also suggests that anagenetic development was dominant within the Eocene and Oligocene, while genetic diversity (branching) suggesting a Text of the Paper: The entire text of the paper is shown below. However, the text is somewhat scrambled. We want to give you as much information as we possibly can about our papers and essays, but we cannot give them away for free. In the text below you will find that while disordered, many of the phrases are essentially intact. From this text you will be able to get a solid sense of the writing style, the concepts addressed, and the sources used in the research paper. and its early evolutionarydevelopment The anagenetic one genus with another without a strong indication oftemporary overlapping from the second half of horsedevelopment The to Miohippus representing a single trunk of thephylogenetic tree From the ancestral home of horses and to million years ago itis variousenvironments and ways of life in the view of many professionals is that that an anagenetic macroevolutionarytransformation took place literature to examine the fossil record from thelate Eocene and but most readily observable in peryear Many palentological interpretations are controversial of horseevolution has followed what Hulbert calls a pattern There was says Simpson no constant and overall increase process in the fossil record Simpson fossilrecord He also suggested that parallel and convergent evolution tookplace the late Oligocene are placed by conventionin a species evolution and thespeciation process generally dominant mode ofspeciation in rapidly evolving clades particularly and evolutionary models MacFadden departsfrom Simpson by emphasizing by transformational change within populationsrather than by theadaptive radiation of hypsodont forms into and beyond the Oligocene began to occur in the Tertiary period abundantly in deposits of the most significantly in size butdisappeared from America at theend of their evolutionary tether in the attainment of speed may most probably have crossed into Asia prior obtainedfrom the fossil record at Costillo Pocket in south-central the Oligocene and Miocene periods elucidated the species-level systematics of middle-Miocene horse phylogeny and characters recognized within the evolution Molarized premolars tridactyl feetEquinae Miocene Cement-covered high-crowned cheek Hulbert and MacFadden state that three newtypes we have a wealth of digit of the forefoot was lost teeth had developed A distinctdepression or pit known been associated with acorresponding increase in intelligence early horses Sensory developments of this kind the early Miocene Kalobatippus Anchitherium and Desmatippus alongwith Parahippus from the early Miocene of North America Theanchitheres the Equinae in which significant cladogenetic branching that one of the critical plants particularly grasses The connection betweenobserved tooth crown height browsers with correspondingshifts in tooth-crown height Morell has summarized recent evidence from the fossil recordand stated suggested that the emergence of high-crowned many regions use the so-called C teeth suggests that some of the fed on mostly C plants D Mexicanus for general adaptive traits in the same ecosystemssuggests that horses divided to Cope's Rule in whichan increase in body size appear to haveminimized competition for dentition in Miocene horses allowed them to invade dramatically MacFadden identifies the fossil Hemisphere A combination ofnatural climate changes leading to twomillion years ago only the hipparionine horses predominating in North Americanfaunas Their going on apace inthis particular era In ten species of horses in these events speaks further to thequestion of what kind evolutionarytopic and to draw upon the literature to a virtually straight single line of evolution Morerecently not only serves to explicate the thesis advanced established theories of necessity requirerevision Simpson's The ancestry of the horse HorsesThrough Time New from Florida Science Morell V Dietary theoretical and empirical literature this reportdescribes evidence obtained from alsoassociated with a phyletic transformation from ancestral to descendantspecies The and Oligocene whilegenetic diversity branching suggesting a cladogenetic developmentalpattern is be a time oflow equine diversity family Equidae over the past millionyears is ancientmembers of the family MacFadden states that at any However from about million years years ago as many as a dozen species rapid diversification becomingcharacteristic of the is an excellent mediumfor examining both anagenesis and cladogenesis It cladogenetic evolution of the horse was occurring a years Between and paleontologists named an new fossil evidence is uncovered Throughout the family was definitely notorthogenetic or straight and toe evolution in different that a distinct process known astransformation leading Simpson Simpson also argued that the more slight MacFadden moved forward from the from ancestral to descendant species only recently that cladogenesis has achieved claims that Simpson held a life-long of the fossil record it is becoming increasinglyobvious the North American equine fossil record beginning history of mammals that the ancestors of the horse horses and tapirs of today can be observed times North America possessed at least nine perfectly offered thoughRidgeway makes reference to various types may have led to the extinction dawn horses known as hyracotheresappeared in the faunas of severed the directconnection between North America and increasinglyadapted for living in open habitats and kind of branching thatis associated with Age Key CharacterHyracotherium Eocene Increased ratio of brain MacFadden p At the beginning of the the Haplohippus and are among facial and bodyproportions Mesohippus and Miohippus had much more classic The skull muzzlewas lengthened and a larger gap between the the opening for the eye Hulbert speculates eye placement is believed to have been linked to out that Miohippus was the genera fromwhich the most Equus were identified Originating from the late Oligocene size comparable to modernEquus and achieving superior to that of otherspecies thus facilitating its horses underwent an explosiveadaptive radiation resulting in MacFadden also believes that the fossil record simultaneousvariations in tooth-crown height This suggests that fairly significantcladogenetic However when the species switchedback to eating browse the controversial conclusion With respect to dietary variations Morell of the isotopes carbon andcarbon than do C plants which mix of C grasses and a grazer MacFadden believes that the coexistence of horses diversified rapidly to include of the Miocenesuggests that species size was not a cladogeneticpattern of evolution was beginning to occur MacFadden is in the emergence of Equus Startingabout eight million to five species atany given hoofed herbivores e g deer and bison may also common ancestor three-toed hipparionine and equine Nevertheless the great diversity of species in the late Miocene period is said to have been event Hulbert Only three horse species survived eliminating during theera under discussion herein Summary and Conclusions The of horses as evident in the fossil the Miocene which created a multiplicity of the fossil recordyields more and more such as Hulbertand MacFadden References Gould S J Life's Natural History MacFadden B J Ancient New York Benjamin Blom Simpson G G Horses New A Cladogenetic View of the Early Evolutionary History of perspective advances the notion that a gradualmicroevolutionary process has However the literature also suggests report focuses therefore on the North American Eoceneand this time on a cladogenetic developmental processis seen to be many fossil sites across thecontinent have been usually possible to find species of MacFadden also says that horsediversity increased so acladogenetic or branching speciation took place during the leading to limited diversity and numbers ofspecies the Oligocene with specific reference to Miohippus andMesohippus Such an the latterperiod DiscussionAnagenesis and Cladogenesis Hulbert states that paleontologists withcontending and alternative hypotheses and theories two-track system Onthe one hand paleontologists including George in size ora definitive pattern of steady change from also rejected the idea that horse evolution simultaneously and that selected quantum shifts involving single genus Miohippus but that Miohippus and Mesohippus interpreted from the fossil record Hedefines anagenesis during an adaptiveradiation MacFadden While Simpson and other cladogenetic evolution and thisdeparture has accumulation across numerous events of discrete branchingspeciation the pattern was decidedlycladogenetic Thus the following discussion The Emergence of Speciated Branching Ridgeway has claimed that it With two extinct families of recent geological agein almost every part the time of the Spanish these horsesfell prey to one or more tosuch an infestation Hulbert states that at the beginning Coloradoprovides evidence of two disparate species one larger and one Hulbert says that at this juncture North American horses took been responsiblefor a revised interpretation of the evolutionary patterns of the familyEquidae The following table presents these characters Recent teeth springing foot Equus Pliocene Evolution of horses appeared in North America These are the generaHaplohippus evidence from theincredibly fossilferous rocks of late-Eocene and Oligocene age andthere were three toes on as a facial fossa were present on the though perhaps improved instinct may be a alongwith improvements in the olfactory and auditory and Archaeohippus had all emerged Of retained the low-crowned relatively simple teeth and paddedfeet took place Hulbert Hulbert further suggests that explanationsfor the evolutionary pattern observed in and interpreted diet of extinct horses is awidely accepted model When one compares different fossil recordsor equid clades found across that the teeth of ancient equines may teeth in horses represented anirreversible evolutionary photosynthetic pathway to turn carbon six horse species of million example had high tooth crowns but teeth marked as would up the niches and resources available to them It over time results in descendant species beinglarger on average than available food and space by occupying severaldifferent niches Clearly this a new adaptivezone A multitude record from this time presenting aportrait of a return to increased global aridity and lessproductive land ecosystems is single horse genus Equus consisting of a fewspecies remained numerical superiority in the fossil record notwithstanding it was Equus both the New World and the Old World the first event andfour more of evolutionary process was at work and supports theassertion identify current thinking andresearch on the topic as the work of Hulbert and MacFadden demonstrates inthe outset of the report with respect to the appropriateness seminal work in this field is thereforeaugmented and expanded York Roberts Rinehart MacFadden B J Fossil Horses Cambridge CambridgeUniversity data straight from the horse's mouth Science Ridgeway W The the fossil record supporting theanagenetic view of the horse phylogeny fossil record for horses presents in general a progressivereplacement of observed in the fossil record depicted as a simple anagenetic progression of generafrom Mesohippus a classic example of macroevolution MacFadden NorthAmerica is given fossillocality in North America from about ago the fossilrecord indicates that horses evolved rapidly adapting to have been found What this suggests early Miocene Hulbert Earlier MacFadden and Simpson agree is the purpose of thisreport to draw upon the processthat is rooted in the Eocene average of three new species of fossil horses course of the twentieth century the trail and linear in terms of evolutionary branches of the family werenot revealed as an orthogenetic to specialization can be identified in the progressive horses of the middleOligocene and all the horses of work of Simpson anddifferentiated between the two major modes of Cladogenesis orbranching as opposed to phyletic speciation is the prominencebecause of what MacFadden characterizes as its importance insystematic methodologies commitment to thepredominant role of evolution that during the second half of horse evolution represented by inthe late Eocene and continuing made theirfirst appearance Hoofed animals Fossil remains ofhorses are found distinctwild species of Equidae These species varied the possibility that after coming to of the NorthAmerican Equidae which North America and Eurasia Evidence Europe and major climatic changesbegan which continued throughout for running MacFadden believes that recent work has cladogenetic evolution MacFadden identified thekey morphological size to body size and expanded neocortex Mesohippus Miohippus Oligocene late Eocene contemporary paleontologists including the best known of the fossilhorses Hulbert claims that horse-likefeatures than older genera The fifth anterior nipping teeth orincisors and the posterior chewing thatthe increase in size of the horse's skull may have improvements inthe vision of these striking example of cladogenetic branching can be observed By Miohippus two main lines ofdescent are recognized a body weight of to kilograms Ultimately itwas survival and advancement MacFadden has suggested numerous clades with high-crowned teeth forgrazing on abrasive supports varied patterns infood consumption ranging from grazing to branching was in fact taking place during this evolutionaryperiod teeth did not change MacFadden states that grazinghorses typically ate grasses which in are primarily trees and shrubs Evidence from fossil C shrubs and twigs while a couple so many species ofsimilar ancestry and largespecies and even a few dwarf lineages Contrary linear progression in terms ofdevelopment Miocene horses says MacFadden convinced that the advent of hypsodonty high-crowned years ago horse diversity dropped fossil locality in the Northern have affected horse diversity As of horses diversified rapidly between and million years ago with fossil record hasconvinced paleontologists that cladogenetic branching was responsible for theextinction of four genera and the maximum diversityobserved in the late Miocene Each of purpose of this report was to examine a specific record was anagenetic orprogressing in horsespecies or branches on the evolutionary trunk This discussion of its secrets to paleontologists and newinvestigative technologies little joke Natural History Hulbert R C diets ecology and extinction of million-year-old horses York Oxford University Press Horses Abstract Drawing upon the occurred within a species This view is thatanagenetic development was dominant within the Eocene Oligocene fossil records Both periods are considered to at work Introduction The fossil record of horses identified as containing abundant remains of horses that seem to have livedside-by-side dramatically that at some fossil sites from million Eocene andcontinued into the Oligocene with The fossil record says MacFadden examination will demonstrate that from the Oligoceneperiod on have been analyzing theequid fossil record for well over coming into vogue andthen falling by the wayside as Gaylord Simpson argued that the evolution of the horse four toes to three and finally one toe Foot was atotally random process He argued adaptiverelationships also influenced this evolutionary process intergradeso perfectly and the differences between them are very as associated with macroevolution or phyletictransformation early paleontologists did discusscladogenesis it is become a standardized interpretation of horse evolution Gould However MacFadden has convincingly argued that despitethe inherent limitations will identify a cladogeneticbranching pattern in was only at a comparatively lateepoch in the the Perissodactyles the earliest ancestralforms of the of America and Ridgeway believes that in pre-glacial conquest Fewsatisfactory explanations for this disappearance have been predators Another theory is that an infestationof parasites of of the Eocene epoch about million years ago tiny smaller Atthe end of the early Eocene the continental drift adifferent course in their evolutionary history and became of an importantadaptive radiation What occurred was precisely the Table I Key Morphological Characters Family EquidaeTaxon of the passive stay Recent apparatus Mesohippus and Miohippus The latter two were much moreadvanced than in SouthDakota and adjacent states Most significantly in both the forefoot and hindfoot side of theskull in front of more apt description of this phenomenon Additionally improved senses took place asbranching occurred Hulbert also points these groups it wasfrom Anchitherium that the ancestors of of Miohippus but reached a considerable the sensorydevelopment of Equinae may well have been horses in the North Americanfossil record relates to diet Fossil of long-term adaptation and evolution North America one finds enormous have evolved in partbecause of the existence of new food change though Morell points out that thisis a somewhat dioxide into sugars and starches Such plants incorporate different amounts years ago ate solely C grasses but others chewed a beanticipated in a browser rather than was during the Miocene that their ancestors the fossil record supports the idea that a of evolutionary changes through branching anddiversification ultimately resulted pre-Miocene levels of only three generally associated with the end ofbranching Additionally competition with cud-chewing in the Northern Hemisphere Hulbert states that evolving from a which would eventually assume primacy among all horse species the advent of a new climaticphase in the genera and six more species in the second that a cladogenetic process of evolution was occurring For many years paleontologists held that theevolution paleontologists have found evidence supporting a cladogeneticevolutionary pattern in of thecladogenetic interpretation It also demonstrates that as by that of contemporary researchers Press MacFadden B J The heyday of horses Origin and Influence of the ThoroughbredHorse and its early evolutionarydevelopment The anagenetic one genus with another without a strong indication oftemporary overlapping from the second half of horsedevelopment The to Miohippus representing a single trunk of thephylogenetic tree From the ancestral home of horses and to million years ago itis variousenvironments and ways of life in the view of many professionals is that that an anagenetic macroevolutionarytransformation took place literature to examine the fossil record from thelate Eocene and but most readily observable in peryear Many palentological interpretations are controversial of horseevolution has followed what Hulbert calls a pattern There was says Simpson no constant and overall increase process in the fossil record Simpson fossilrecord He also suggested that parallel and convergent evolution tookplace the late Oligocene are placed by conventionin a species evolution and thespeciation process generally dominant mode ofspeciation in rapidly evolving clades particularly and evolutionary models MacFadden departsfrom Simpson by emphasizing by transformational change within populationsrather than by theadaptive radiation of hypsodont forms into and beyond the Oligocene began to occur in the Tertiary period abundantly in deposits of the most significantly in size butdisappeared from America at theend of their evolutionary tether in the attainment of speed may most probably have crossed into Asia prior obtainedfrom the fossil record at Costillo Pocket in south-central the Oligocene and Miocene periods elucidated the species-level systematics of middle-Miocene horse phylogeny and characters recognized within the evolution Molarized premolars tridactyl feetEquinae Miocene Cement-covered high-crowned cheek Hulbert and MacFadden state that three newtypes we have a wealth of digit of the forefoot was lost teeth had developed A distinctdepression or pit known been associated with acorresponding increase in intelligence early horses Sensory developments of this kind the early Miocene Kalobatippus Anchitherium and Desmatippus alongwith Parahippus from the early Miocene of North America Theanchitheres the Equinae in which significant cladogenetic branching that one of the critical plants particularly grasses The connection betweenobserved tooth crown height browsers with correspondingshifts in tooth-crown height Morell has summarized recent evidence from the fossil recordand stated suggested that the emergence of high-crowned many regions use the so-called C teeth suggests that some of the fed on mostly C plants D Mexicanus for general adaptive traits in the same ecosystemssuggests that horses divided to Cope's Rule in whichan increase in body size appear to haveminimized competition for dentition in Miocene horses allowed them to invade dramatically MacFadden identifies the fossil Hemisphere A combination ofnatural climate changes leading to twomillion years ago only the hipparionine horses predominating in North Americanfaunas Their going on apace inthis particular era In ten species of horses in these events speaks further to thequestion of what kind evolutionarytopic and to draw upon the literature to a virtually straight single line of evolution Morerecently not only serves to explicate the thesis advanced established theories of necessity requirerevision Simpson's The ancestry of the horse HorsesThrough Time New from Florida Science Morell V Dietary theoretical and empirical literature this reportdescribes evidence obtained from alsoassociated with a phyletic transformation from ancestral to descendantspecies The and Oligocene whilegenetic diversity branching suggesting a cladogenetic developmentalpattern is be a time oflow equine diversity family Equidae over the past millionyears is ancientmembers of the family MacFadden states that at any However from about million years years ago as many as a dozen species rapid diversification becomingcharacteristic of the is an excellent mediumfor examining both anagenesis and cladogenesis It cladogenetic evolution of the horse was occurring a years Between and paleontologists named an new fossil evidence is uncovered Throughout the family was definitely notorthogenetic or straight and toe evolution in different that a distinct process known astransformation leading Simpson Simpson also argued that the more slight MacFadden moved forward from the from ancestral to descendant species only recently that cladogenesis has achieved claims that Simpson held a life-long of the fossil record it is becoming increasinglyobvious the North American equine fossil record beginning history of mammals that the ancestors of the horse horses and tapirs of today can be observed times North America possessed at least nine perfectly offered thoughRidgeway makes reference to various types may have led to the extinction dawn horses known as hyracotheresappeared in the faunas of severed the directconnection between North America and increasinglyadapted for living in open habitats and kind of branching thatis associated with Age Key CharacterHyracotherium Eocene Increased ratio of brain MacFadden p At the beginning of the the Haplohippus and are among facial and bodyproportions Mesohippus and Miohippus had much more classic The skull muzzlewas lengthened and a larger gap between the the opening for the eye Hulbert speculates eye placement is believed to have been linked to out that Miohippus was the genera fromwhich the most Equus were identified Originating from the late Oligocene size comparable to modernEquus and achieving superior to that of otherspecies thus facilitating its horses underwent an explosiveadaptive radiation resulting in MacFadden also believes that the fossil record simultaneousvariations in tooth-crown height This suggests that fairly significantcladogenetic However when the species switchedback to eating browse the controversial conclusion With respect to dietary variations Morell of the isotopes carbon andcarbon than do C plants which mix of C grasses and a grazer MacFadden believes that the coexistence of horses diversified rapidly to include of the Miocenesuggests that species size was not a cladogeneticpattern of evolution was beginning to occur MacFadden is in the emergence of Equus Startingabout eight million to five species atany given hoofed herbivores e g deer and bison may also common ancestor three-toed hipparionine and equine Nevertheless the great diversity of species in the late Miocene period is said to have been event Hulbert Only three horse species survived eliminating during theera under discussion herein Summary and Conclusions The of horses as evident in the fossil the Miocene which created a multiplicity of the fossil recordyields more and more such as Hulbertand MacFadden References Gould S J Life's Natural History MacFadden B J Ancient New York Benjamin Blom Simpson G G Horses New If this paper is not what you are looking for, you can search again: Search for: or Click here to request an essay written just for you.