Page 52 - Land Snails of New Mexico

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calciphiles.Thetwonorthernspeciescould, then,reasonablybe considered as comprising a group of their own.
Additional Species of Oreohelix
At atimeequivalenttothelatestPleistoceneglaciation,it seems likelythatmost ofthe mountains in southern N e w Mexico were inhabited by oreohelicid snails (Oreohelix and Radiocentrum). Fossilsfrom many mountains with calcareous bedrock seem to confirm this. (Molluscan fossils are not found inmountainswithigneousbedrockinNewMexico.) The mountains bordering the Rio Grande Rift on the west, plus the CaballoMountains, would have harbored representatives ofthe groups discussed in the preceding sections. Eastward, in addition to Oreohelix nogalensis of the Sierra Blanca Mountains, discussed above, there occurs a small species, O. neomexicana.
Oreohelix neomexicana H. A. Pilsbry, 1905. Proceedings
of the Academy of Natural Sciences of Philadelphia,
57:282, Pl. 11, Figs. 8, 9; Pl. 19, Fig. 9; Pl. 25, Fig. 59. T.L.: Canyon Diablo near Rowe, San Miguel Co., N e w Mexico.
Oreohelix neomexicana was originally described (Pilsbry, 1905) as a subspecies of O. yavapai; the nominal subspecies of which occurs in north-central Arizona. Herein, we elevate
neomexicana to species status on the basis of conchological differences already listed by Pilsbry (1939:520) and because of the geographical separation of more than 200 miles between known populations of yavapai and neomexicana. W e also relegate O. y compactula Cockerell, August 1905, and O. socorroensis Pilsbry, 1905, to the synonymy of O. neomexicana,Pilsbry,May 1905.Thenamesocorroensishas page precedence (p 279) over neomexicana (p 282) in Pilsbry (1905). However, acting as firstrevisers (Ride et al., 1985:53), We choosethenameneomexicanabecausethistaxonhasan
identifiable type locality, whereas socorroensis does not. The type locality of socorroensis is given as "Negra Mountains, Socorro Co." in its description, wherein Pilsbry noted that he was unabletolocatethetypelocality,andthatthecollectorof thetypeserieswasunknown.We alsoareunabletoidentifyany " N e g r a M t s . " i n N e w M e x i c o . F r o m its a p p e a r a n c e , w e s u s p e c t that the type of socorroensis is a fossil.
As shown by Crews (1981, unpubl, M.S. thesis,University ofTexas,El Paso),O. neomexicana isfound, living,from north central N e w Mexico, in foothill regions of the southern Sangre de Cristo and Jemez Mountains, southward through the Sandia andManzanoMountains,GallinasPeakinnorthwesternLincoln Co.,theOscuraMountainsofSocorroCo.,andrecentlyasmall living population has been found in Arcente Canyon ca. 4.7 road-milesSofHighRollsat7,200ftelevationinthe southwestern Sacramento Mountains, Otero Co. Pilsbry (1939:520) reported itfrom near Grants, Cibola Co., but we have been unable to find any Oreohelix in that area, including MountTaylor. .
Habitat--Oreohelix neomexicana has been taken near Montezuma in the southeastern foothills of the Sangre de Cristo
Mountains, in scant cover under loose stones alongside a paved r o a d . I n t h e S a n d i a M o u n t a i n s , it o c c u p i e s a v a r i e t y o f h a b i t a t s from lush forested canyons on the east side of the range to the environmentally extreme conditions of Sandia Crest, where a d w a r f e d f o r m o c c u r s a b u n d a n t l y . O n t h e C r e s t , it o c c u r s u n d e r limestonerocks.IntheManzanoMountains,itwasfoundunder single stones in areas of rich leaf litter, on Gallinas Peak, it occurs in igneous-rock talus associated with rock glaciers (Blagbrough, 1991:837). In the Oscura Mountains, a range with muchcalcareousbedrock,ithasbeencollectedonthewestside below North Oscura Peak and from another locality on the west side two miles north of South Oscura Peak. Thus, the species seems to tolerate a broad variety of habitats in mountains where it still exists. D e s p i t e this ability, it h a s g o n e extinct o v e r m u c h of the southern part of its former range, apparently during the Holocene, as indicated below.
Oreohelix neomexicana varies greatly in size from mountain range to range, and even within ranges, as exemplified in the Sandia Mountains. Pilsbry (1939:416) discussed the great diversity in size that may occur within a given species of Oreohelix,evenovershortdistances.He notedthattheremay be significant variation in shell size even within the same colony. Similarly, Henderson (1924:110) wrote concerning Oreohelix inColorado:"Itisnotatalluncommon tofindacolonyinwhich those individuals living under the best cover are large and robust, while those at the edges where cover is scant are dwarfed."
Paleontology--Oreohelix neomexicana iswidespread as a fossil in colluvial and alluvial deposits in the Sacramento Mountains. Fossils from alluvial deposits along the Tularosa River have been dated as being of Holocene age. However, a living population has been found only at the one site noted above. Fossils of O. neomexicana also occur southeastward
from the Sacramento Mountains, in the Guadalupe Mountains into Texas. West ofthe Sacramento Mountains, itisfound as a fossil in the San Andres Mountains and, to the south, in the HuecoandFranklinMountainsofTexas.
Oreohelix houghi W. B. Marshall, 1929. Proceedings of the U.S. National M u s e u m , 76(5):2, Pl. 1, Figs. 7-10. T.L.: Heber, Navajo Co., Arizona. (Diablo mountainsnail)
D i s t r i b u t i o n — O r e o h e l i x h o u g h i i s a s p e c i e s m a i n l y o f e a s t central Arizona. Bequaert and Miller (1973:127-128) recorded itfromeasternCoconinoCo.,eastwardtotheareaofSt.Johns and Springerville in Apache Co. Pilsbry (1939:516) referred to itas being a species of the Little Colorado River Valley. The Zuñi and Carrizo W a s h Valleys are northeastern branches of the LittleColoradoValley.Itisnotsurprising,then,thatO. houghi followsthesevalleysheadwardintoNew Mexico.We have specimens from about 4 miles east of Zuñi, Pilsbry assigned (1939:431)specimensfrom5mileseastofZuñitoOreohelix strigosa depressa. However, itseems likely that these specimens werereallyO.houghi.CourtesyofMr.DickDuman,wealso have obtained specimens from south of Zuñi, in Valencia Co., in the area of Cibola Canyon, which drains into the Zuñi River Canyon. Still farther south, Rebecca Smith-Sealy has found O. houghi along Carrizo Wash, 3 miles east of the Arizona border,