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Ask The Hunting Experts => Understanding Deer => Topic started by: Big58cal on December 12, 2007, 01:04:01 PM

Title: Origin, Classification and Distribution of White-tailed Deer - Part I
Post by: Big58cal on December 12, 2007, 01:04:01 PM
This information was taken from White-tailed Deer: Ecology and Management.  It is A Wildlife Management Institute Book, Compiled and Edited by Lowell K. Halls, published by Stackpole Books, copyright 1984 by the Wildlife Management Institute.

Rollin H. Baker, Director Emeritus, The Museum, Professor Emeritus, Department of Fisheries and Wildlife, Department of Zoology, Michigan State University, East Lansing, Michigan

Origin of Artiodactyla

     Artiodactyls--even-toed ungulates in which the body weight is supported by the third and fourth metapodials (paraxonic)--had their beginning in the family Dichobunidae during the Eocene Epoch (36-58 million years ago) in both North America and Eurasia (Dawson 1967, Rose 1982).  The origin of hoofed mammals is obscure (Pilgrim 1941a), but many paleontologists (Gazin 1955, Matthew 1915, Romer 1966, Simpson 1945) believe that the ancestral even-toed suborder Palaeodonta was derived from the Condylarthra, an early Tertiary Period assemblage of mammals intermediate between insectivores and true ungulates.  The earliest recognizable artiodactyls (genus Diacodexis) in the early Eocene already had elongated limb elements for cursorial gait and possessed the distinctive double-pulleyed ankle bone (Guthrie 1968, Schaeffer 1947).  Thus it is very likely that the even-toed ungulates were undergoing development earlier, during the Paleocene Epoch.  Artiodactyls flourished and diversified throughout the Eocene, and with the decline of the odd-toed ungulates (Perissodactyla) in the Oligocene Epoch, the artiodactyls underwent pronounced adaptive radiation in terrestrial habitats--in the Miocene Epoch (Viret 1961).  Many phyletic lines became extinct.  Others gave rise to the ancestral stocks of modern artiodactyls (Pilgrim 1941a, Simpson 1945, Romer 1966), and continued to overshadow the odd-toed perissodactyls--the horses, tapirs and rhinos.
     Modern Artiodactyla (approximately 171 species) include the Suina and the Ruminantia suborders.  The Suina contain the pigs, peccaries and hippopotamuses, which have feet with four "functional" toes, separate metapodials usually--insted of coalesced cannon bones, bunodont molar teeth, canine tusks and simple stomachs.  The Ruminantia contain the cud-chewers--the modern camelids--as surviving members of the Infraorder Tylopoda, and the tragulids (chevrotains), cervids, giraffids, antilocaprids and bovids of the Infraorder Pecora.  Today's rumnants usually have limbs with two functional toes, metapodials fused as cannon bones, complex selenodont molars, upper incisors reduced or absent, upper canines often lacking but sometimes enlarged in males, and compound stomachs.

Beginnings of Cervidae

     The earliest pecorans occurred in the Upper Eocene.  They have been classified as belonging to Superfamily Traguloidea, the most primitive group of Pecora.  Although cervids likely may have had ancestral stock in common with modern representatives of the Family Tragulidae--the chevrotains, Tragulus of Asia and Hyemoschus of Africa--Webb and Taylor (1980) emphasize that these tragulids are remote from higher ruminants.  Nevertheless, early members of this superfamily appear to have been the ancestral stock from which were derived the more advanced cud-chewing families Cervidae, Giraffidae, Antilocapridae and Bovidae (Pearson 1964, Romer 1966, Viret 1961).  These families appeared early in the Miocene, with a distinctive developmental hiatus becoming evident between the more primitive deer/giraffe line and the more advanced pronhorn/bovid line.  The former became chiefly browsing animals, with low-crowned teeth, and generally inhabited forest and/or brush country.  The pronghorn/bovid descent, on the other hand, fostered mostly grazing animals, with high-crowned teeth, and lived usually in open areas that were a conspicuous part of the lanscape of mid-Tertiary geological times.
     Cervids had their origin in the long-extinct pecoran family Palaeomerycidae, which flourished in the Eurasian late Oligocene and Miocene.  Representatives of this family, or of Dromomerycidae, a closely related New World counterpart, are known to have existed from the Miocene to the mid-Pliocene of North America (Dawson 1967).  This lineage showed progressive development of elongated two-toed limbs, low-crowned teeth adapted for browsing, stout traguloidlike upper canine tusks in primitive forms (persisting in modern cervids, Cervulus, Elaphodus and Moschus) and, in more advanced genera, hornlike structures extending upward at various angles over the orbits.  It was the belief of Sir Richard Owen (see Scott 1962) that there is an inverse relationship between horns, or antlers, and canine tusks in pecorans, with those species without horns or antlers having long, saberlike upper canines and those species with horns or antlers having reduced (as in Cervus) or lost (as in Odocoileus, except on rare occasions) upper canines.  The modern exceptions are the muntjac, or barking deer (Cervulus), and the tufted deer (Elaphodus), each of which has both antlers and tusks.
     The Eurasian genus Dremotherium and the American Blastomeryx, despite lacking bony protuberances from the frontal bones, and possessing formidable canine tusks (Matthew 1908), seem to have been the forerunners of later Miocene palaeomerycids of the genera Aletomeryx, Cranioceras and Dromomeryx.  These three fossil forms had hornlike processes (probably not shed as in the case of true antlers) extending upward and over the orbits (Romer 1966).  Apparently lacking the horny coverings typical of the pronghorn/bovid line, the head protuberances of these genera could correspond to the skin-covered outgrowths on the skulls of modern giraffes, or of modern cervids in velvet, or to the basal pedicels of deer antlers (Pilgrim 1941b).  Of interest is that one of these genera, Aletomeryx, had both upper canine tusks and hornlike structures (see Gregory 1951).  Variation is shown in Cranioceras, which bears a median horn extending back from the occiput.
     One further step in "antler" development came with the appearance of the genus Lagomeryx, a palaeomerycid considered by Romer (1966) as lying at the point of origin of the deer family.  This animal had paired, deerlike, vertical, bony spikes with short side branches.  Again, these structures probably were not deciduous.  In fact, no true intermediates have thus far been found between fossil forms with permanent giraffelike protuberances and the annually shed antlers in modern cervids.
     Strange indeed was the course of evolution that developed the "disposable" head adornments of the Cervidae, sepecially when "permanent" ones, like the bovids', might have served the same functions.  The antler growth process requires considerable expenditure of nutrients by the carrier.  In fact it seems almost too energy-expensive for the individuals to have endured, despite the fact that antlers grow, then as now, during the vegetative season when foods are usually plentiful.  Be that as it may, cervids have diversified successfully and persisted throughout four continents plus northern Africa.
     True "antlered" cervids appeared first in the Eurasian Miocene.  Persisting however were primitive antlerless and tusked characteristics in at least some forms (continuing in the modern musk deer [Moschus]).  Because some biologists consider this pecoran as a relict, perhaps it really does not pertain to this discussion--belonging more likely to a distinct family, namely Moschidae (Webb and Taylor 1980).  The Old World genera Dicrocerus and Stepanocemas are perhaps the earliest recognizable members of the Family Cervidae.  These deer, whose fossil remains were found in both Miocene and Pliocene beds, were small--muntjaclike in size, and had forked antlers.
     From this Pliocene stem stock, specific lines of cervid evolution are obscure, but obviously diversified, appearing first in Eurasia and later in North America.  On the latter continent, modern cervis derived as a result of the evolvement of two major groupings.  These were the Subfamily Odocoileinae, in which were derived Odocoileus, Alces, Rangifer, five neotropical genera, and Old World Hydropotes and Capreolus, and the Subfamily Cervinae, in which were derived circumboreal Cervus and three Old World genera.  In both subfamilies the tendency was toward a gradual increase in body size and antler dimension.  These developments culminated in the massive bulk and the huge adornments of the North American "stag-moose" (Cervalces) and the Eurasian "Irish elk" (Megaloceros).  These largest of antlers were thought by some theorists (see Lull 1924, Simpson 1951) to be hinderances--perhaps leading to the animals' demise in the wane of the last receding glaciers.  However, there is no actual basis for such conclusions (Gould 1974).
     The fossil record of the Pleistocene Epoch bears evidence of the presence at that time of all modern genera of New World deer.  However, the derivation of these, except perhaps for that of Cervus (known from the Eurasian late Pliocene), is obscure.  Romer (1966) regarded Odocoileus strictly as an American development--with an unknown Asian lineage, and as ancestral to the several distinctive deer genera now found in South america.  In the Pleistocene, New World cervids shared both forested and open areas with an impressive array of hoofed associates, including mammoths, mastodons, horses, tapirs, peccaries, camelids, pronghorns and bovids.  Only nine cervid genera, one pronghorn, and nine bovid genera--plus a few neotropical tapirs, camelids (llamas and allies), and peccaries--survived the postglacial "ordeals" and inhabit the Western Hemisphere today.  The rest of the great assemblage of "Ice Age" ungulates has disappeared, and the reasons why are in dispute (Martin and Wright 1967).

References Cited

Dawson, M. R. 1967.  Fossil history of the families of recent mammals. In Recent mammals of the world: a synopsis of families, ed. S. Anderson and J. K. Jones, Jr., pp. 12-53, New York:  The Ronald Press Co. 453 pp.

Gazin, C. L. 1955.  A review of the Upper Eocene Artiodactyla of North America.  Smithsonian Misc. Coll. 128.  Washington, D. C.: Smithsonian Institution. 96 pp.

Gould, S. J. 1974.  The origin and function of "bizarre" structures: antler size and skull size in the "Irish elk," Megaloceros giganteus.  Evolution 28(2): 191-220.

Gregory, W. K. 1951.  Evolution emerging.  A survey of changing patterns from primeval life to man.  Vol. II.  New York: The Macmillan Co. 1,013 pp.

Guthrie, D. A. 1968.  The tarsus of early Eocene artiodactyls.  Amer. Mus. Novit. 128.  New York: American Museum of Natural History, 96 pp.

Lull. R. S. 1924.  Organic evolution.  New York: The Macmillan Co. 729 pp.

Martin, P. S., and H. E. Wright, Jr., eds. 1967.  Pleistocene extinctions. The search for a cause.  New Haven: Yale Univ. Press. 453 pp.

Matthew, W. D. 1908.  Osteology of Blastomeryx and phylogeny of the American Cervidae.  Bull. Amer. Mus. Natur Hist. 24:535-562.

Pearson, R. 1964.  Animals and plants of the Cenozoic Era.  London: Butterworth & Co. Ltd. 236 pp.

Pilgrim, G. E. 1941a.  The dispersal of the Artiodactyla.  Biol. Rev., Cambridge Phil. Soc. 16(2):134-163.

Pilgrim, G. E. 1941b.  The relationship for certain variant fossil types of "horn" to those of the living Pecora.  Ann. Mag. Natur. Hist. 7:172-184.

Romer, A. S. 1966.  Vertebrate paleontology. 3rd. ed.  Chicago: Univ. Chicago Press. 468 pp.

Rose, K. D. 1982.  Skeleton of Diacodexis, oldest known artiodactyl.  Science 216(4546):621-623.

Schaeffer, B. 1947.  Notes on the origin and function of the artiodactyl tarsus.  Amer. Mus. Novit. 1356.  New York: American Museum of Natural History. 24 pp.

Scott, W. B. 1962.  A history of land mammals in the western hemisphere. Rev. ed. New York: Hafner Publ. Co. 786 pp.

Simpson, G. G. 1945.  The principles of classification and a classification of mammals.  Bull. Amer. Mus. Natur. Hist. Vol. 85.  New York: American Museum of Natural History. 350 pp.

Simpson, G. F. 1951.  The meaning of evolution.  New York: Mentor Books. 192 pp.

Viret, J. 1961. Artiodactyla. In Traite de Paleontologie, ed. J. Piveteau, pp. 887-1,021.  Paris: Masson. 1,138 pp.

Webb, S. D., and B. E. Taylor. 1980.  The phylogeny of hornless ruminants and a description of the cranium of Archaeomeryx.  Bull. Amer. Mus. Natur. Hist. 167(3):117-158.