Page 35 - Land Snails of New Mexico

Gastrocopta holzingeri (V. Sterki, 1889, as Pupa). The Nautilus, 3:37, 96, 119. T.L.: Will Co., Illinois. (lambda snaggletooth)
General Distribution--Gastrocopta holzingeri extends from the northern Appalachian region westward to the Plains statesandnorthtoCanada.Hubricht(1985:Map48)mappedit from many counties in Oklahoma, including the Panhandle, and Metcalf (1984a:57) took itin Cimarron Co., Oklahoma, in the westernmost Panhandle, from there its range extends into northeastern N e w Mexico.
New Mexico Distribution-Thisspecieswasfoundliving innortheasternNew Mexico,mainlyalongtheCimarronRiver Canyon and associated mesas in the extreme northern part of the state,on Sierra Grande, and along the Mora River valley on the easternslopeoftheSangredeCristoMountains. T.D.A. Cockerell collected it in 1903 in Gallinas Canyon near Las Vegas(ANSP11617).Aspecimen(ANSP83042)isindicated as being collected by E. H. A s h m u n in the Oscura Mountains, Socorro Co.
Habitat—In the areas noted above, G. holzingeri was found inleaflitterinwooded and brushy areas along canyon walls, and in montane forests as on Sierra Grande.
Paleontology-Gastrocopta holzingeri has been taken in Pleistocene deposits along the Rio Grande Valley in Doña Ana Co. indicating that its range extended farther to the southwest in times past.
Subgenus Vertigopsis
Gastrocopta pentodon (T. Say, 1822, as Vertigo). Journal of the Academy of Natural Sciences of Philadelphia, 2.376. T.L.: Pennsylvania, without precise locality. (comb snaggletooth)
Pilsbry observed (1948:888) that Gastrocopta pentodon "is found over a greater area than any other North American Gastrocopta." It also appears to be among the most taxonomically troublesome of North American Gastrocoptas, perhaps because of such an extensive range. In 1906, Vanatta and Pilsbry attempted to resolve the problem with a publication thatincluded53figures! Allattemptsshow thatthereisahighly variable taxon (or taxa) involved, which, at one extreme, exhibitslarger,moreovoidshells(1.7-2.0mm x 1.1-1.2mm)
and, at the other extreme, exhibits a more cylindrical, smaller
shell(1.5-1.8mm x0.8-1.1mm).Manyauthorshaveassigned
t h e s m a l l e r , m o r e c y l i n d r i c s h e l l s t o G . p e n t o d o n ( S a y ) a n d t h e
larger, more ovoid ones to G. tappaniana (C. B. Adams).
H o w e v e r , W . J. C l e n c h r e e x a m i n e d t h e t y p e s o f G . t a p p a n i a n a
and selected a lectotype (1965:106) that was of the smaller,
more cylindric pentodon morphology. Thus, the name
tappanianaseemsunavailableforthemore ovoidshells,butno
one has started to apply a different name. In his comprehensive
work (1985:9), Hubricht retains the name tappaniana, using it
a s a s p e c i e s n a m e . N e c k ( 1 9 9 0 ) r e p o r t s it a s a s p e c i e s f r o m t h e Texas Panhandle.
Bequaert and Miller (1973:89), unlike Hubricht (1985),
concluded that the forms pentodon and tappaniana were two extremes of a continuum across which intergradation was so gradual thatno demarcation could be made between two species. They wrote "the senior author reached the conclusion that itis impossibletorecognizeconsistentlytwobiologicalspecies,"and recognized only G. pentodon (which has priority). Ashbaugh and Metcalf (1986:10) followed the recommendation of Bequaert and Miller and assigned all fossil specimens of this complex from some spring-related deposits in southern N e w Mexicotopentodon,althoughmany were definitelyofthelarge, ovoid, shell shape typical of traditional "tappaniana."
It may be that the two shell morphologies are related to habitat and that they represent only ecophenotypes. The more ovoid, "tappaniana" form is found in damper, often marshy, habitats, whereas pentodon is a form of drier habitats. Baker (1939:100-101),who treatedthetwo asseparatespecies,noted that " G a s t r o c o p t a t a p p a n i a n a is f o u n d b e n e a t h p i e c e s o f w o o d , logs, and damp debris in wet places such as floodplains, moist woodlands and swamp edges, while Gastrocopta pentodon prefers drier situations."
So far,livingrepresentativesofthemoisture-loving,more ovoid, larger "tappaniana" form have not been found in N e w Mexico. However, it occurs as a fossil in spring-related Pleistocene deposits in Eddy, Otero, Lincoln, D o ñ a Ana, and Socorro Counties. Further investigation of the few remaining m a r s h y h a b i t a t s a t l o w e l e v a t i o n s m a y r e v e a l it still t o b e e x t a n t in the state.
The factthatthe most slender, cylindrical representatives of the G. pentodon spectrum, in size and shell morphology, approach specimens of Gastrocopta pilsbryana (V. Sterki) presents another complication. Pilsbry (1948.891) noted similarityinshellsofthetwospecies,butseparatedthem onthe basisof 1)fewerdenticles(fourorfive)inpilsbryanaandoften more than five inpentodon and 2) the presence of an internal, rimlike callus upon which the teeth of G. pentodon are borne, a character supposedly lacking in thin-lipped G. pilsbryana. W e note, however, that specimens presumably of G. pilsbryana from more eastern mountains in N e w Mexico (Sacramento and Guadalupe Mountains and the isolated mountains of the northeastern part of the state) have a distinct callus and corresponding external crest behind the outer lip, as in the case of G. pentodon. W e are undecided whether these should be considered a variant of G. pilsbryana or whether pilsbryana is another variant of pentodon. At present, and pending further work, w e prefer to retain, conservatively, the n a m e pilsbryana forNew Mexicomontanerepresentativesofthiscomplex,and
i n c l u d e l i v i n g p e n t o d o n i n t h e s t a t e list w i t h a q u e r y .
Gastrocopta pilsbryana (V. Sterki, 1890, as Pupa). The Nautilus, 3:123. T.L.: "Colorado River," presumably in Arizona. (montane snaggletooth)
General and New Mexico Distribution--Gastrocopta pilsbryana, as discussed in the preceding account, is very m u c h a southwestern mountain snail, found mainly in Arizona and N e w M e x i c o , e x t e n d i n g n o r t h i n t o s o u t h e r n U t a h a n d C o l o r a d o
andsouthtoChihuahua,México.ItoccursthroughoutNew Mexico inforested mountains.
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