Page 59 - Land Snails of New Mexico

wasreferredearliertotheArizonaspeciesA. chiricahuanaDall, 1896. Later,Pilsbry (1905:233) placed thissnailinA. a. robusta. The type locality of robusta is imprecise, being somewhere in the Jemez Mountains, apparently between Bland and Jemez Springs. Pilsbry (1940:924) noted that robusta occurred at elevations higher than the nominal subspecies. It seems likely that A. a. robusta is only a higher-elevation ecophenotype of A. ashmuni, and not deserving of subspecific recognition. It is clear that shell size is influenced b y conditions prevailing at different elevations in a number of species of Ashmunella, and this is most likely the case here. Generally, progressively larger shells are found at higher elevations, at least t o a r o u n d 8 , 0 0 0 ft, a b o v e w h i c h t h e t r e n d m a y r e v e r s e .
Distribution--This Ashmunella is a denizen of the Jemez
Mountains region. Ithas been taken from Santa Clara Canyon on the northeast to Bland on the southeast, across the Jemez range to the Jemez Springs area, and then northwestward to the Nacimiento Mountains. Itis,then,one ofthemore widespread Ashmunellas, areally, and is the northwesternmost representative ofthegenus.
Habitat--Most collections of this species have been from forested canyons, as at Bland and in Santa Clara and Frijoles Canyons. After summer rains, the snails may be seen on paths near the creek in Frijoles Canyon, Bandelier National Monument. It occurs at Bland in rock talus, and in the Nacimiento Mountains it can be found in association with limestone outcrops along the Rio de las Vacas and Rio Caballo. Ashmunella ashmuni also occurs in Joaquin Canyon, in red granitetalusalongtheGuadalupeforkoftheJemezRiver.
SpeciesofSouthernNewMexico, East of the Tularosa Basin
Ashmunella pseudodonta (W. H. Dall, 1897, as Polygyra). Proceedings of the U.S. National Museum 19:343. T.L.: Capitan Mountains, White Oaks, Lincoln
Co., N e w Mexico. (Capitan woodlandsnail)
Pilsbry (1940:924-925) recognized two subspecies of Ashmunella pseudodonta, the nominal subspecies with type localitylistedas "Capitan Mountains, White Oaks, Lincoln Co.,
at7500 feet(E. H. Ashmun)" and A. pseudodonta capitanensis, withtypelocality"NearBaldonado Springs,CapitanMountains, LincolnCo.,altitude8200feet(E.H.Ashmun)." IfReverend A s h m u n collected the type of nominal subspecies near White Oaks, itis likely that itwould have been from Carrizo Peak, to the south ofWhite Oaks, or possibly from Patos Mountain to the southeast. In Ashmun's time, both of these mountains probably were considered as part of the more easterly located Capitan Mountains.We havebeenunabletolocateBaldonadoSprings.
Supposedly, A. p. capitanensis differed from the nominal subspeciesinitslargersizeandlesserdevelopmentofdentition. nearBlandintheJemezMountains,SandovalCo.,New WehaveseencollectionsofA.pseudodontafromLoneand Carrizo Peaks and Patos Mountain on the west, to the Capitan Mountains on the east, and failed to find any shell characteristics thatshow ageographicpatternsuggestive ofthepresence oftwo subspecies. Shell size varies greatly, but this seems related to suchfactorsaselevationandslopeexposure,discussedabove. Two lotscollectedintheareaofCapitanPass,fromwithinca.
have envisioned these to comprise an eastern and a western
subspecies,buthedidnotmakeacaseforthis.Themaincriteria
used in separating the two subspecies appear to have been
slightlylarger size and more consistent presence of a bifid basal
t o o t h i n A . t. p o r t e r a e . H o w e v e r , P i l s b r y , h i m s e l f , q u e s t i o n e d t h e usefulness of shell size in A. thomsoniana as a taxonomic
character(1940:921): "Whether sizeisofracialsignificance.. s e e m s t o m e d o u b t f u l ; it m a y b e t h a t l a r g e r s i z e i s a r e s p o n s e t o longer humid seasons higher up." Moreover, Cockerell and Cooper (1902:109) concluded that "the character of the basal tooth,whether double or single, ishighly variable, and not to be reliedontoseparateraces." Thus,itseemsthatneitherofthe two differentiating characters--shell size and presence or absence of a bifid tooth--was considered very important or consistent, even by these earlier workers. It is possible that a
detailed study might show the validity of recognizing two subspecies of A. thomsoniana, but lacking such evidence, it seems wisest to refrain from such partitioning. This position is reinforced by noting that Cockerell also described a subspecies, A. t. cooperae, 1901, which Pilsbry (1940:921) noted was i n t e r m e d i a t e b e t w e e n A . t. t h o m s o n i a n a a n d A . t. p o r t e r a e i n regard to shell diameter.
Distribution--Ashmunella thomsoniana occupies only the southernmost tip of the Sangre de Cristo Mountains, approximately south ofthenorthern boundary of San Miguel Co. (as ifthe boundary extended westward across the range). It is not known what factor, or factors, prevent its occurrence farther north in the range into what appears to be very similar habitat.
Habitat--Most collections of A. thomsoniana have been taken along forested canyons like those northeast of Santa Fe. In upper Pecos Canyon, these snailsmay be seen crawling about after summer showers, even in campgrounds frequented by humans. Here, itis likely to be observed especially along the marginofthenarrowfloodplainandbaseoftheflankingforested
slopes.
Thespecieshasbeenobservedasfardown thePecosValley
as Villanueva State Park, at 5,750 ft, where it occurs under riparian shrubs and small trees on the Pecos Riverfloodplain. At Montezuma, in the eastern foothills of the Sangre de Cristo range, the species occurs in talus immediately east of an abandoned smelter, at an elevation of ca. 6,800ft.
Paleontology--Pilsbry (1940:919) synonymized a fossil species, A. antiqua Cockerell, 1901, from Pleistocene deposits n e a r L a s V e g a s , w i t h A . t. p o r t e r a e . A n o t h e r f o s s i l t a x o n , A . t.
pecosensis Cockerell, 1903, was described from a deposit at "ValleRanch,Pecos,"basedonasinglespecimen.We alsohave collected fossils of A. thomsoniana of probable Pleistocene age along Pecos Canyon near Pecos.
Ashmunella ashmuni (W. H. Dall, 1898, as Polygyra). ProceedingsoftheU.S.NationalMuseum, 19:342.T.L.:
Mexico. (Jemez woodlandsnail)
Pilsbry (1940:922–923) recognized two subspecies ofA. ashmuni, the nominal subspecies, with type locality near Bland, and A. a. robusta Pilsbry, 1905. The type of this latter subspecieswascollectedbyRev.E.H.Ashmun,himself,and
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