Page 77 - Land Snails of New Mexico

Metcalf,A.L.,andSmartt,R.A.,eds.,1997,LandsnailsofNewMexico. New MexicoMuseumofNaturalHistoryandScienceBulletinNo.10.
LAND SNAILSOFNEW MEXICO
FROMAN HISTORICALZOOGEOGRAPHICPOINTOFVIEW
ARTHE L.METCALF
University of Texas at El Paso, Department of Biological Sciences, El Paso, Texas 79968-0519
ABSTRACT. Thisabstractbrieflynotesthefollowinggeneralities,inasmuchasasummary section is included. Efforts to delineate zoogeographic provinces for land snails of the southwesternUnitedStatesandforNew Mexico,inparticular,arediscussedandevaluated,minor modifications are proposed. A history is presented of geological, paleoclimatic, and paleontological aspects that seem to have been related to the N e w Mexico land-snail fauna, past andpresent,extendingfromtheLateMesozoictotheQuaternary.From thisanalysis,amodelis proposed concerning Cenozoic historical zoogeography of the N e w Mexico land-snail fauna.
INTRODUCTION
A SymposiumoftheAmericanMalacologicalUnionand Western Society of Malacologists, held in 1989 in honor of Dr. WalterB.Miller,stimulatedmy interestinthezoogeographyof landsnailsofNewMexico. Thetopicseemedaproposonsuch an occasion because Bequaert and Miller (1973) essentially initiated, and went far in analyzing, southwestern land-snail zoogeography. Hereinisadiscussionofsomehistoricalaspects ofthezoogeographyoftheland-snailfaunaofNew Mexico.
ZOOGEOGRAPHIC DIVISIONSAND PROVINCES
OF WESTERN LAND SNAELS
William G. Binney (1885:18-26) summarized his views
concerning zoogeography of North American land snails,
proposing three major"provinces". Eastern, Central, and Pacific.
In the United States, his Eastern Province extended from the
Atlantic coast to the Rocky Mountains, the Central Province
from theRocky Mountains to the Sierra Nevada, and the Pacific ProvincefromtheSierraNevadatothePacificOcean. He
subdivided the Pacific Province into more northern Oregonian and more southern Californian Regions.
Henderson (1931) recognized (see Fig. 1A) only two major geographic subdivisions in the land-snail fauna of the United States: an Eastern Division, essentially the same as Binney's Eastern Province, and a Western Division, incorporating Binney's Central and Pacific Provinces. Henderson retained Binney's Oregonian and Californian Regions, although referring to them as provinces, and extended the Californian eastward to incorporatesouthwesternmostArizona.He subdividedBinney's Central Province into the following three provinces: 1) T o the northwest, a Washingtonian Province was recognized east of the OregonianProvince.2)A southwesternProvincewasdefined, including Arizona, except for the southwestern part (noted above) and N e w Mexico, except for the eastern part (placed in the Eastern Division). 3) Henderson relegated the remainder of Binney's Central Province to a Rocky Mountain Province, which
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Figure 1.Molluscan provinces of western United States proposed by Junius Henderson (1931: Fig. 1). B, Molluscan provinces of western United States proposed by Henry A. Pilsbry (1948: Fig. 1). Abbreviations indicate the following provinces: O=Oregonian, C=Californian, W=Washingtonian, RM=Rocky Mountain, SW=Southwestern, T=Texan, and PL=Mexican Plateau. C, Boundaries of the Southwestern Molluscan Province proposed by Joseph C. Bequaert and Walter B. Miller (1973: Fig. 1; by permission ofThe University ofArizona Press).
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