Page 41 - Land Snails of New Mexico

some of our lots from Colorado and other mountain states undecided,..."Whereas,itseemswisetoabandonalbula,a c a u t i o n a r y n o t e is s o u n d e d a n d a n e w p r o b l e m m a y b e b r o a c h e d by Pilsbry'sobservationinthesame paragraph that"V. albula is somewhat intermediate between gracilicosta and cyclophorella
.." Thisopensaquestionastowhether"albula"might represent hybrids or intergrades between two species or subspecies, gracilicosta and cyclophorella.
Vallonia gracilicosta occurs widely in northeastern N e w Mexico, where itisprobably the most common land snail. In mostplaces,itisassociatedwithbrokenterrain,asalongthe Ogallala Caprock escarpment, the Cimarron River Canyon, basaltic flows and basalt-capped mesas, and in all the isolated northeastern mountains. It extends from the Oklahoma State Line to at least the Sangre de Cristo Mountains. Towards the south, the species becomes less widespread and, east of the Sacramento Mountains, itisrestrictedtoafew localitiesalong the Ogalalla Formation scarp, usually on north-facing slopes.
Shellsattributabletobothgracilicostaand cyclophorella are widespread in the Sacramento Mountains. Along canyons, V. gracilicosta extends to lower, more arid elevations at about 5,400ft.Athigherelevations,V gracilicostaseemstoprefer floodplains of the mountain canyons, whereas V. cyclophorella is more common on adjacent wooded, often rocky, canyon
slopes. Occurrence of these two Vallonias sympatrically in the
Sacramento Mountains argues for considering them as separate
species rather than subspecies of each other. However, it is
possible that they could behave differently elsewhere, as in the north-centralmountainswhereintermediateformsoccurinsome
places, like those that Pilsbry (1948:1032) allocated to V. albula. Another population with puzzling, intermediate characteristics occurs in the Big Hatchet Mountains and is treated below as a separate species, V. sonorana, for practicality.
West of the Rio Grande Valley occurrences of V. gracilicostaseemtobescattered.Tothenorth,V gracilicosta occurs in the Zuñi Mountains and M o u n t Taylor areas and along stream valleys in extreme northern San Juan Co. (Los Pinos, Animas, and La Plata Rivers). Southward, populations have been found in the valley of the Gila River.
Paleontology—Wallonia gracilicosta occurs as a Pleistocene fossilwestwardacrossthesouthernpartofNew Mexicoandinto A r i z o n a , w h e r e B e q u a e r t a n d M i l l e r ( 1 9 7 3 : 1 9 3 ) r e p o r t e d it a s a fossil,but not living. Itseems to have become extinct in the formerwesternpartofitsrangeduringtheHolocene. Vallonia
cyclophorella, by contrast, is a widespread living species in Arizona.
Vallonia sonorana H. A. Pilsbry, 1915. Proceedings of the A c a d e m y of Natural Sciences of Philadelphia, 67:345, Fig. 5. T.L.: Summit of Big Hatchet Mountain (=Hacheta Grande),HidalgoCo.,New Mexico.
Wallonia sonorana has had a checkered taxonomic career. PilsbryandDanielscollecteditintheBigHatchetMountainson an expedition in 1910. Pilsbry (1915) later described the species. In his 1948 monograph (p. 1033), Pilsbry relegated V. sonorana to the synonymy of V. albula, discussed above. As
construed by Pilsbry, V. albula appeared to have something of anintermediatemorphologybetweenthatofV.cyclophorella andV gracilicosta,whichalsoseemedtobethecasewithV. sonorana.Itisinthesizerangeofthesetwo species.As shown in Pilsbry's (1948: Fig. 552) illustrations, some specimens exhibitthethinlipcharacteristic of V. cyclophorella and others, thethickenedlipofV gracilicosta.Ourspecimenstendmore toward the cyclophorella thinner-lip form.
Bequaert and Miller (1973:63) assigned V. sonorana to the
synonymyofV gracilicosta.Thismayprovetobethemost
judiciousallocation,especiallybecauseV gracilicostaoccursas
a fossil in the area of the Big Hatchet Mountains. Numerous
fossil specimens, for example, have been taken in Pleistocene
depositsofU-Bar Cave, south oftheBig Hatchets, and from the Little Hatchet Mountains to the northwest.
B e c a u s e o f its p u z z l i n g i n t e r m e d i a c y b e t w e e n c y c l o p h o r e l l a andgracilicosta,we electtoretainthespeciesinV.sonorana, where originallyplaced,untilitsstatusbecomes clearer.
N e w Mexico Distribution and Habitat--This species is
known only from the Big Hatchet Mountains. Pilsbry and DanielstookitfromthesummitofHachetaGrande. We have
takenitatseverallocalitiesatthebaseofcliffsonthenorthface
o f H a t c h e t a G r a n d e , w h e r e it w a s f o u n d i n l e a f litter m a i n l y o f GambelOakandinamountainsidewoodlandofoakandtall
pinyonsandjuniper. Thehabitatisratherxericandisassignable totheUpper Sonoran LifeZone.
Family Urocoptidae
In his monograph of 1946, Pilsbry retained all species in the
family Urocoptidae from the United States in the genus
Holospira,whiledesignatingseveralsubgenera. Subsequent authors have been more inclined to elevate these and other
subgeneratogenericrank. Herein,wehavefollowedthe recommendations of Thompson (1974, 1988) in regard to generic and subgeneric rankings.
Genus Metastoma
Metastoma roemeri (L. Pfeiffer, 1848, as Cylindrella). Monographia Heliceorum viventium sistens descriptiones systematicasetcriticasomnium huiusfamiliaegenerum et specierum hodie cognitarum, 2:382. T.L.: Near N e w Braunfels,Comal Co.,Texas. (distortedmetastoma)
General Distribution--Metastoma roemeri is the only urocoptidoccurringinNew Mexicothatisnotalocalendemic. Its r a n g e e x t e n d s f r o m t h e B a l c o n e s E s c a r p m e n t a r e a o f T e x a s westward to the Hueco and Franklin Mountains, El Paso Co., and into southern N e w Mexico.
N e w Mexico Distribution--Metastoma roemeri occurs in somemountainsofsouthernNewMexicoeastoftheRioGrande
Valley. ThewesternmostrecordsarefromtheSanAndres Mountains.Italsomay occurinthenorthernprolongationofthe FranklinMountainsintosouthernDoña Ana Co.,New Mexico, because itisfound in this range a short distance south in Texas. It has been taken in fossil form in probable Pleistocene sediments excavated from Conkling's Cave on the east side of
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