Page 45 - Land Snails of New Mexico

General Distribution--The distributional center for R.
(1973:81) considered only californicum, of this group, to be living in Arizona. Our observations indicate that the minute P u n c t u m o f N e w M e x i c o i s o f t h e s a m e s p e c i e s a s t h e o n e i n Arizona. Itis,infact,similartothespecimen illustratedby Pilsbry (1948:Fig. 355) as P. californicum, from the Dragoon
durangoanus seems to be in northern México. The type locality
i s i n t h e S t a t e o f D u r a n g o , w h e r e w e h a v e c o l l e c t e d it. A l s o , i t
occursinsomelowmountainrangeswithcalcareousbedrockto
the south of Ciudad Juárez, Chihuahua, and in the Juárez
Mountainsthemselves.ItoccursintheFranklinMountains,El MountainsofsoutheasternArizona.Dr.BarryRoth,whois Paso Co., Texas, and specimens from there were described as studying Punctums of the west-coast states, has suggested (in
lit t., 2 3 J u n e 1 9 9 0 ) , h o w e v e r , t h a t t h e s p e c i m e n n o t e d f r o m t h e NewMexicoDistribution--InNewMexico,wehavetaken DragoonMountainsappearsdifferentfromP.californicumof
Bulimulus pasonis by Pilsbry (1946).
this species in the Howells Ridge portion of the Little Hatchet
Mountains. After a considerable hiatus, itoccurs again in the southernmost San Andres Mountains. Across the Tularosa
Basin, it occurs in the southwestern part of the Sacramento Mountains. Itprobablyoccursinthesouthwesternpartofthe GuadalupeMountainsinNew Mexico,butrecordssofarhave been only from nearby Texas.
Habitat--In all the above New Mexico habitats, R.
durangoanus isdefinitelyan inhabitantoftheUpper Sonoran ZoneandhasnotbeenfoundintheTransitionZone,incontrast toR.dealbatusneomexicanus.Ittoleratesxericconditions.Our
records are from along canyon walls or fairly steep foothill slopes of the mountains noted above. In such habitat, specimens have been found in limestone talus or under dead yucca stems and dead caudices of sotol, where they are sometimes attached to the underside of a stone or attached to plant material.
Family Punctidae
The family Punctidae and the following three families have been included often in the family Endodontidae. W e follow Solem (1983:47), who elevated several subfamilies of the Endodontidae to family status.
Genus Punctum
This genus contains the smallest discoid snails in the N e w Mexico land-snail fauna. Adult shells generally range in diameterfrom1.1to2.2mm. Thetaxonomicallocationofthese
minute gastropods is difficult and our identifications, below, are tentative.
Punctum minutissimum (I. Lea, 1841, as Helix). Transactions of the American Philosophical Society 9:17. T.L.: vicinity of Cincinnati, Ohio. (small spot)
A minute Punctum widespread in the higher mountains of
New MexicoclearlybelongstotheP.minutissimumgroupof
Pilsbry (1948:644). This group comprises P. blandinum of
Tennessee, P. minutissimum of the eastern United States, P.
californicum of the western United States, and P. randolphi of thePacificNorthwest,NewMexicoislocatedinanintermediate
zone in which some malacologists have assigned the local minute Punctum to minutissimum and others to californicum.
Baker (1930:9) reported a Punctum from the Sacramento Mountains as being very close to minutissimum. O n the other hand, J.C. Bequaert (pers comm.) considered specimens found intheGuadalupeMountainsofTexas,afewmilesfromNew Mexico, to pertain to P. californicum, and Bequaert and Miller
Californiaandthatitmay beanew or,atleast,differentspecies. Giventhisconsiderableuncertainty,we conservativelyassignthe NewMexicomaterialtoP.minutissimum,indicatingthatitis, at least, in the minutissimum group of Pilsbry (1948:644).
Genus Paralaoma
Paralaoma caputspinulae (L. A. Reeve, 1852, as Helix). ConchologiaIconica,Vol.7.T.L.:New Zealand.(pinhead spot)
This species has been assigned to various taxa in the
literature. It long ago was allocated to Punctum conspectum
(Bland, 1865). Roth (1985, 1986) referred it to Punctum
(Toltecia) pusillum (Lowe, 1831), but later (1987b;95-96)
transferred itto Paralaoma caputspinulae (Reeve, 1852). In
New Mexico, P. caputspinulae is common in Three Rivers
Canyon on the west side of Sierra Blanca Peak, Lincoln Co.,
w h e r e t h e s p e c i e s is f o u n d a l o n g a c r e e k i n r i c h l e a f litter u n d e r
heavy shade of a well-developed riparian forest. Elsewhere in
o u r s u r v e y , it h a s b e e n f o u n d o n l y a t 8 , 4 0 0 f t o n t h e w e s t s i d e o f
Lake Peak in the Sangre de Cristo Mountains, SantaFe Co. This
distributionalpattern ispuzzling. Although Pilsbry (1948:652)
recorded Punctum conspectum from Willow Creek in the
MogollonMountains,CatronCo.,we havenotfounditinthat
area. Bequaert and Miller (1973:153) listed Punctum
conspectum for Arizona, only on the basis of literature citations that recorded it from the southeastern and from several
mountains in the northeastern parts of the state.
Family Charopidae Genus Radiodiscus
Radiodiscus millecostatus H. A. Pilsbry and J. H. Ferriss, 1906.ProceedingsoftheAcademy ofNaturalSciencesof Philadelphia, 58:154, Fig. 10. T.L.: Carr Canyon, Huachuca Mountains, Cochise Co., Arizona. (ribbed
pinwheel)
A l t h o u g h r e c o r d s a r e s c a t t e r e d , it s e e m s t h a t t h e c e n t e r o f distribution for Radiodiscus millecostatus is in México, where ithas been reported as far south as Michoacán and Tamaulipas. It occurs in Chihuahua, and we have collected specimens in Coahuila.ItappearsthatNew MexicoandArizonaareonthe northernperipheryoftherangeofthisspecies.InNew Mexico Pilsbry (1948:657) reported R. millecostatus from Willow
Creek in the Mogollon Mountains, Catron Co., in which range we alsotookitinleaflitterfrom7,200-to9,650-ftelevation.In
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