Page 60 - Land Snails of New Mexico

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0.7mileofeachother,differbyabout4.5mm inmeandiameter (14.5vs 19.0mm).Dentitionishighlyvariable,rangingfrom toothless specimens to those with one or two low basal denticles andashortparietaltooth.Many shellsfromPatosMountain,to the west, closely resemble shells from the eastern end of Capitan Mountain, near Pine Lodge, in both size and development of dentition.Theselocalitiesareneartheeasternandwesternlimits
6,000-to9,300-ftelevation.A populationat7,200-ftelevation attained maximum size. Size gradually and progressively decreasedaboveandbelowthiselevation(Stern,1973:Fig. 11). A similar300-ftintervaltransect,from9,600to12,000ftinthe SierraBlancaPeakarea,showed ageneraldecreaseinshellsize with increase in elevation (Stern, 1973: Fig. 10).
oftherangeofthespecies,andtheirsimilarityseems toillustrate well the inadvisability of partitioning A. pseudodonta into subspecies.Therefore,we treatithereatthespecieslevelonly.
Distribution and Habitat--Ashmunella rhyssa rhyssa is widespread in the Sacramento Mountains, both areally and altitudinally.Itisespeciallycommon alongcanyons,occurring as low as 5,750-ft altitude, being found in limestone talus at lower elevations. At higher elevations, in the Canadian Life Zone, the species may be found throughout the forests. For instance, persons picnicking or camping in the recreation areas
Distributionand Habitat--TheLonePeak-CarrizoPeak
Patos Mountain-Capitan Mountain complex is composed of
igneous rock, which has produced large amounts of talus
especially on the upper and northern slopes of the Capitan
Mountains. Blagbrough (1991) interpreted the talus and
associated rock glaciers as being of Pleistocene periglacial
origin. All our collections of A. pseudodonta have been from
talus accumulations. At the eastern end of Capitan Mountain,
specimensoccurinatalusaccumulationatthelowerendof terraneoftheSacramentoMountainsandA.r.altissima,with
Forest Trail 64, atca. 6,200ft elevation, north of the Pine Lodge settlement. The species seems to thrive even at these lower elevationsiftalusispresent.
the igneous bedrock of the Sierra Blanca Mountains from the northern Sierra Blanca to the Nogal Peak areas. There are exceptions to this generality, however, for example, A. r. rhyssa is f o u n d a l o n g t h e l o w e r p a r t o f T h r e e R i v e r s C a n y o n i n a n a r e a of igneous rock.
Ashmunella rhyssa rhyssa (W. H. Dall, 1897, as Polygyra). T h e Nautilus, 11:2. T.L.: according to Pilsbry (1940:926),"Ashmun didnotstatejustwhere he collected thetypelotofA.rhyssa,butpresumablyitwas somewhere ontheeasternflankofSierraBlancaPeak,abovethetown ofRuidoso." (SierraBlancawoodlandsnail)
Ashmunella rhyssa altissima tolerates the highest summits of Sierra Blanca and Nogal Peaks, the former being almost 6,500 ft higher than the lowest elevations inhabited by the species. At these very high altitudes, above tree line, snails find shelterinrocktalus,muchastheirrelativesdoatthelowest elevations.NumerouscollectionsofA.r.altissimahavebeen made alsoalongcanyons inthe SierraBlanca Mountains, where colonies often are found along streams under willows and other small trees or (unfortunately for the malacologist) in nettle patches.
Ashmunella rhyssa altissima (T. D. A. Cockerell, 1898, as Polygyra). The Nautilus, 12:76. T.L.: summit of Sierra Blanca Peak, Otero Co., N e w Mexico.
Numerous species and subspecies of living and fossil Ashmunellas have been described from the Sierra Blanca
Paleontology-Pleistocene fossils s h o w that in the past A. r. altissima extended southward into the northern Sacramento
Mountains (a complex of mountains extending from Nogal Peak southward to Sierra Blanca Peak), and beyond these to include the Sacramento Mountains. In his 1940 monograph, Pilsbry recognizedthreespeciesandanumberofsubspeciesas inhabiting this mountain complex. In a revision of the A s h m u n e l l a s o f t h i s a r e a , S t e r n ( 1 9 7 3 ) r e d u c e d t h e n u m b e r o f taxa to one species,A. rhyssa, with the two subspecies indicated above. Stern considered the nominal subspecies as occurring throughout the Sacramento Mountains and northward to the lower south, east, and west slopes of Sierra Blanca Peak. H o w e v e r , o n S i e r r a B l a n c a ' s s l o p e s a r o u n d 8 , 0 0 0 - 9 , 0 0 0 ft, Stern detected evidence of intergradation between the two subspecies, with A. r. altissima occurring on the uppermost slopes (its type locality, atop the summit). Ashmunella rhyssa altissima occurs on the northern slopes of Sierra Blanca and northward in the Sierra Blanca Mountains to the Nogal Peak area, w h e r e it is c o m m o n a l o n g B o n i t o a n d N o g a l C a n y o n s a n d other canyons in the northern part of this range.
Mountains atleastas faras upper Tularosa Canyon, westward in the Tularosa Basin at least to Keen Spring (Ashbaugh and Metcalf,1986:13),andasfareastas4.4milesSEand4miles NW ofLincoln,alongBonitoandSalazarCanyons,respectively.
InhisanalysisofA.rhyssa,Sternsawclearevidencesofthe relationship between elevation and shell size, mentioned in connection with other species of Ashmunella, above. In Peñasco Canyon,ontheeasternslopeoftheSacramentoMountains,size was analyzedforcollectionstakenat300-ftintervalsfrom
Several presumed variants of A. rhyssa occur in calcareous Quaternary sediments of the Sacramento Mountains. None of these has been given taxonomic recognition. However, a number of different species of Pleistocene Ashmunellas from the Sacramento Mountains have been described by Metcalf (1973).
around Cloudcroft during summer months commonly note this snail crawling about. Our subjective assessment is that this species attainsthe greatestpopulation density of any Ashmunella inNew MexicointhehighforestsoftheSacramentoMountains.
In general, A. r. rhyssa is associated with the limestone
F o s s i l s o f A . r. r h y s s a h a v e b e e n f o u n d t o t h e s o u t h , i n t h e Guadalupe Mountains, where the species does not live at this time. Fossils have been noted in Pine Spring Canyon in the Guadalupe Mountains of Texas. In the Guadalupe Mountains foothillsinEddy Co.,fossilsofA. r.rhyssahavebeentakenca. 8 m i l e s w e s t o f M a l a g a i n s e d i m e n t s a l o n g t h e B l a c k R i v e r a n d alongRockyArroyoCanyonatca.3,500ft,about1mileSW of Rocky Arroyo Cemetery. The above records indicate a more widespread distribution of A. rhyssa in the past, to both the southeast and west, and to lower elevations than atpresent.
Ashmunella carlsbadensis H. A. Pilsbry, 1932. The Nautilus,46:19.T.L.:accordingtoPilsbry(1940:978):"A