Page 53 - Land Snails of New Mexico

nearNM Highway191inCatronCo.Thisisoneofseveral speciesoflandsnails,morewidespreadineasternArizona, whichbarelyenterwesternNew Mexico.
Oreohelix barbata H. A. Pilsbry, 1905. Proceedings of theAcademyofNaturalSciencesofPhiladelphia,57:279, Pl. 25, Figs. 57, 58; Pl. 19, Fig. 5; Pl. 22, Fig. 6. T.L.: According to Bequaert and Miller (1973:129) the T.L. is i n t h e C h i r i c a h u a M o u n t a i n s o f C o c h i s e C o . , A r i z o n a , i n Cave Creek Canyon near Winn Falls (bearded mountainsnail)
Oreohelix barbata has been reported from the Chiricahua Mountains of Arizona and the Mogollon Mountains of N e w Mexico. In the Mogollon Mountains, the species occurs in southwesterncanyonsoftherange,atleastfrom LittleDry Creek Canyon northwestward to Whitewater Creek Canyon, and then northeastwardatleasttoWillowCreekCanyon.We havefound italong creeks at the bottom of such canyons in riparian forest. Here,itoccursinrockrubblewherethereisalsoanabundance of leaf litter from deciduous trees. The distribution of this species in the Mogollon and Chiricahua Mountains is reminiscent of that of Gastrocopta prototypus, discussed above,
and could suggest a distributional history involving either vicariance or migration.
Genus Radiocentrum
The genus Radiocentrum differsfrom Oreohelix in thatits first1% (embryonic)whorlsbearsharplydefinedradialribsand the animal is egg-laying, rather than live-bearing, as in Oreohelix. There are a number of species of the genus in southeastern Arizona and in northwestern Chihuahua, but N e w M e x i c o is i n h a b i t e d p r e s e n t l y b y o n l y t w o s p e c i e s o f t h e g e n u s .
T h i s is a g e n u s w i t h a fossil r e c o r d e x t e n d i n g b a c k t o C r e t a c e o u s t i m e i n w e s t e r n N o r t h A m e r i c a . P r o b a b l y , it h a s i n h a b i t e d N e w M e x i c o d u r i n g m o s t o r all o f t h e C e n o z o i c .
Radiocentrum hachetanum (H. A. Pilsbry, 1915, as Oreohelix). Proceedings of the Academy of Natural SciecesofPhiladelphia,67:330,Pl.6,Figs. 1-1d,6,Text Fig. 4a. T.L.: summit of Hacheta Grande, Big Hatchet Mountains, Hidalgo Co., New Mexico. (Hacheta mountainsnail)
Radiocentrum ferrissi (H. A. Pilsbry, 1915, as Oreohelix). Proceedings of the Academy of Natural Sciences of Philadelphia, 67:332, Pl. 6, Figs. 4-5d, T e x t fig.4b.T.L.: at"Station3"(seebelow)intheBigHatchet Mountains, Hidalgo Co., New Mexico. (fringed mountainsnail)
To avoid repetition, shells of the two species of Radiocentrum from the Big Hatchet Mountains are compared together, but they differ conchologically in numerous respects
(seeKey).
Distribution and Habitat--From thecollectionsofPilsbry
and L. E. Daniels in 1910 and of ourselves, itappears that R. hachetanum is a species of the higher areas of the Big Hatchet
complex.PilsbryfounditonandaroundthesummitofHacheta Grande,thehighestpeakintherange.We havefounditina fairlymesichabitatonthenorthfaceofHachetaGrandeandon the northeastern slope of North Hatchet Peak.
Radiocentrum ferrissi, on the other hand, was taken by PilsbryandDanielsatlowerelevationsinthemore arid,. southern part of the Big Hatchet Mountains. H e described the type locality as follows (Pilsbry, 1915:333):
O u r S t a t i o n 3 is o n l e d g e s o f h i g h cliffs f a c i n g t h e mouthofSheridanCanyon,andespeciallyona bench abouthalf-way up. Here Ferriss'sOreohelix lives on an almost inaccessible clifflooking out over the mesa into Mexico. There is little
vegetationon theledges. ...The Oreohelix colony is of small extent, the ledges where they were observed living are probably not over a couple of square rods in area, with perhaps an equal area on thetalusbelowthecliffs,wheredeadshellswere found. These estimates are from memory, as I neglected to note the figures at the time.
Pilsbry goes on to note that the only other locality where R. ferrissiwasfoundwas on theeastsideofTeocalliButte--alow, elongate mountain on the southwestern periphery of the range.
H e n o t e d (p. 3 3 3 ) that this locality w a s " m o r e restricted, a n d if possible more arid" than the type locality.
Pilsbrydescribedasubspeciesforeachofthetwoliving species, based on dead shell materials collected in the Big HatchetMountains. Ineach case,he assumed thatthe subspecies had gone extinct, these comprised R. hachetanum cadaver and R. ferrissimorticinum. Both ofthese sepulchral subspecies were found and described from the same station (Pilsbry's No. 5) on the north side of a peak located southwest of Hacheta Grande, which Pilsbry called Daniels Mountain in honor of his field companion.
W e have seen fossils of both R. hachetanum and R. ferrissi
in sediments on the east slope of North Hatchet Peak, and have not seen fossils of hachetanum elsewhere. Radiocentrum
ferrissi, on the other hand, seems to have been adept at long distance travel (for a snail) during the Pleistocene. Fossils of R. ferrissi are common in Pleistocene deposits in U-Bar Cave, located in a small limestone mountain outlying the Big Hatchet Range to the south (and west of the northern Alamo Hueco Mountains). Fossilshave been taken also on Howells Ridge, in t h e n o r t h e r n Little H a t c h e t M o u n t a i n s . M o s t u n e x p e c t e d l y o f all, is the occurrence of Pleistocene fossils that appear attributable toR.ferrissiatseverallocalitiesintheFranklinMountains ofEl Paso Co., Texas, 110 miles to the east of the Big Hatchet Mountains. In Vinton Canyon in the northern Franklin Mountains, R. ferrissi occurs in Pieistocene deposits together
with Oreohelix neomexicana, discussed above. Family Succineidae
. .The identification of succineids is notoriously difficult because the shells of many species are similar, even those of different genera. Characteristics of the reproductive organs generallyhavebeen used todifferentiatespeciestaxonomically. This being the case, the true identity of type specimens, most consisting of shells only, is often in question. For species
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