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of the
FLORIDA STATE MUSEUM
Biological Sciences
Volume 33
1988
Number 2
THE HOLLOW-RIBBED LAND SNAILS OF THE GENUS
COELOSTEMMA OF THE SOUTHWESTERN
UNITED STATES AND MEXICO
Fred G. Thompson
UNIVERSITY OF FLORIDA
GAINESVILLE
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THE HOLLOW-RIBBED LAND SNAILS OF THE GENUS
COELOSTEMMA OF THE SOUTHWESTERN
UNITED STATES AND MEXICO
Fred G. Thompson*
ABSTRACT
This paper discusses the hollow-ribbed species of Coelostemma (Gastropoda,
Pulmonata, Urocoptidae). Goniapex, new subgenus is proposed for C. pyrgonasta, new
species (type locality: Bishop's Cap Mountain, New Mexico). Referred species are C
townsendi (Bartsch, 1906), C. freytagi Bartsch, 1950, C. bryantwalkeri (Pilsbry, 1917), C.
rciteri Drake, 1951, and C. attenuapex, new species (type locality: 12.7 km SE Ciudad
Camargo, Chihuahua). Coelostemma marrsi Drake, 1951 is a junior synonym of C freytagi
Bartsch, 1950. Coelostemma (C.) scaphopleuron, new species (type locality: 1.5 km WNW
Colotlipa, Guerrero) also has hollow ribs, but is more closely related to solid-ribbed species
from southern Mexico. Holospira (Allocoryphe) minima Martens, 1897 is superficially similar
to Goniapexin that it also has hollow ribs.
RESUME
Se discuten las species de Coelostemma (Gastropoda, Pulmonata, Urocoptidae) con
costillas huecas. Se propone Goniapex subgenero nuevo para C. pyrgonasta, especie nueva
(localidad tipo: Bishop's Cap Mountain, New Mexico). Las species asignadas son C.
townsendi Bartsch, 1906), C. freytagi Bartsch, 1950, C. bryantwalkeri (Pilsbry, 1917), C. reiteri
Drake, 1951, y C. attenuape, species nueva (localidad tipo: 12.7 km SE Ciudad Camargo,
Chihuahua). Coelostemma marrsi Drake, 1951 es sin6nimo de C freytagi Bartsch, 1950.
Coelostemma (C.) scaphopleuron, species nueva (localidad tipo: 1.5 km WNW Colotlipa,
Guerrero) tambi6n tiene costillas huecas, pero es mas afin a species de costillas s61lidas del
sur de Mexico. Holospira (Allocoryphe) minima Martens, 1897 se parece superficialmente a
Goniapexpues tambi6n tiene costillas huecas.
Key words: Gastropoda, Pulmonata, Urocoptidae, Coelostemma, Holospira, Goniapex,
Allocoryphe, Mexico, Guerrero, Chihuahua, New Mexico, Bishop's Cap Mountain,
Chihuahua Desert, sculpture.
*The author is Curator in Malacology, Florida State Museum, University of Florida,
Gainesville, Florida 32611.
THOMPSON, F. G. 1988. The hollow-ribbed land snails of the genus Coelostemma of the
southwestern United States and Mexico. Bull. Florida State Mus., Biol. Sci. 33(2):87-112.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
TABLE OF CONTENTS
Introduction ................................................................................................................................................88
A know ledgem ents..................................................................................................... .......................89
M easurem ents ...................................................................................................... .......................... 89
C oelostem m a.................................................................................................................. ......................... 90
G oniapex new subgenus............................................................................... ..................................... 90
Coelostemma pyrgonasta new species...................................................... ............................. 92
Coelostem m a townsendi (Bartsch) ......................................................................................................... 94
Coelostem m a freytagi Bartsch................................................................... ...................................... 95
Coelostem m a reiteri D rake......................................................................... ..................................... 97
Coelostem ma attenuapex new species...................................................... ..................................... 99
Coelostemma bryantwalkeri (Pilsbry) .................................................... ..................................... 100
Coelostemma scaphopleuron new species................................................................................. 101
L literature C ited ................................................................................................... ....................... 102
F igures................................................................................................................................. ............. 104
INTRODUCTION
During recent years a considerable number of new species of land snails
have been discovered inhabiting various mountain ranges in New Mexico.
One is a snail described below from Bishop's Cap Mountain. It is particularly
interesting because it belongs to a genus thought to be endemic to Mexico in
areas far to the south of the United States border. Systematic affinities are
with several poorly known species from the Chihuahua Desert. In order to
properly define the species from New Mexico it is necessary to redescribe its
Mexican counterparts. Collectively they comprise a very distinct group within
Coelostemma (Urocoptidae, Holospirinae) and warrant the recognition of a
new subgenus.
Coelostemma consists of snails with cylindrical shells that have an
enlarged hollow axis internally. The axis may or may not bear spiral lamellae,
nodes, or oblique thread-riblets. The species are obligate inhabitants of
limestone. The genus is known from Veracruz, Oaxaca, Guerrero, Mexico,
Colima, Nueva Leon, Coahuila, Durango, and Chihuahua, and is herein
recorded from New Mexico. Coelostemma is divided into five subgenera.
Coelostemma s. s. is found in the states bordering the southern edge of the
Mexican Plateau, Coahuila and Nueva Leon (Pilsbry, 1953; Thompson,
1971). Styloptyx and Crycoryne are known only from southern Durango.
Apertaxis is known only from the Sierra Guadaloupe, Coahuila. The fifth
subgenus is defined in this paper. It occurs in Chihuahua and New Mexico.
THOMPSON: HOLLOW-RIBBED LAND SNAILS
The snails treated in this paper have in common hollow axial ribs on the
postembryonic whorls of the shell and also a simple, enlarged hollow
columella. The structure of the columella places them in Coelostemma. The
hollow ribs would suggest that they all are closely related within the genus.
Hollow axial ribs are an uncommon morphological trait in the Holospirinae.
Of the approximately 150 species named in this subfamily, only one has been
described as having hollow ribs. The close relationships implied by the rib
structure do not exist. Instead, the trait represents a case of morphological
convergence. Features of the embryonic whorls demonstrate that hollow-
ribbed species belong to three different generic or subgeneric groups.
ACKNOWLEDGEMENTS
I wish to express my gratitude to the following people who have assisted me in this
project. For the loan of type specimens in their charge: John B. Burch, Museum of Zoology,
University of Michigan (UMMZ); Robert Hershler, National Museum of Natural History
(USNM). Kurt Auffenberg and Mary Lou Lyman assisted in the preparation of photographs
and illustrations. Artie Metcalf, University of Texas, El Paso (UTEP) brought to my attention
specimens of Coelostemma pyrgonasta, which led to a review of other species to which it
appeared related. Field work in Mexico was conducted under permit 219.1, issued by the
Direcci6n General de La Fauna Sylvestre, Mexico. Specimens catalogued at the Florida State
Museum are referred to by UF numbers.
MEASUREMENTS
Cylindrical land snails, such as Urocoptidae and Clausiliidae, are highly
variable individually in shape due to allometric growth that frequently occurs
in the lower whorls (e.g. Figs. 30-33, 42-46). Therefore shell measurements
are made differently from those usually employed for other kinds of land
snails. These measurements (Figs. 1, 2) are described here because confusion
exists in the literature due to inconsistent methods used by various authors.
SHELL LENGTH.- The distance parallel to the axis from the base of the
peristome to the top of the apex (Fig. 1). SHELL WIDTH.- The widest part
of the shell above the last whorl. This measurement does not include the
peristome (Fig. 1). APERTURE WIDTH.- The greatest diameter
perpendicular to the columella across the face of the aperture. This
measurement includes the peristome (Fig. 1). APERTURE HEIGHT.- The
greatest vertical distance across the aperture. This measurement includes the
peristome and is made parallel to the face of the aperture (Fig. 2). ANGLE
OF APERTURE.- The angle formed in lateral profile between the plane of
the aperture and the axis of the shell (Fig. 2).
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
Coelostemma Dall, 1895
Goniapex, new subgenus
Type species.-- Coelostemma pyrgonasta, new species.
Referred species.--
Holospira (Haplocion) townsendi Bartsch, 1906
Holospira bryantwalkeri Pilsbry, 1917
Coelostemma freytagi Bartsch, 1950
Coelostemma reiteri Drake, 1951
Coelostemma attenuapex, new species
This subgenus is proposed for a group of species endemic to the
Chihuahua Desert of northern Mexico and the southwestern United States.
The species inhabits isolated limestone hills and mountain ranges where they
occupy xeric habitats among limestone boulders and talus. The subgenus is
characterized by the growth form of its embryonic shell, its postembryonic
sculpture, its peristome, its columella, and its shell color. The embryonic shell
consists of three or four large protruding whorls. The second whorl is
conspicuously larger than the following two whorls and is distinctly angular at
the periphery (Fig. 3). The embryonic sculpture is superficially smooth.
Under high magnification it consists of a dense mesh of close, vertical threads
and granules on the first two whorls and weak ribs on the third whorl (Figs. 3,
4). In contrast Coelostemma s. s. has low, rounded embryonic whorls bearing
poorly defined granules and riblets (Fig. 52, 53). The embryonic whorls of
Ciycoryne and Styloptyx are similar to Coelostemma s. s. (Thompson 1971:
271, 290). The postembryonic shell of Goniapex is sculptured with hollow
axial ribs, and incomplete, irregular incremental threads between the ribs
(Figs. 3, 7). The peristome is broadly expanded and nearly equally wide
around the aperture. It is flat-faced, in contrast to the trumpet-shaped
opening that is found in most other Urocoptinae, including other subgenera
of Coelostemma. The columella is hollow and large, being about 0.20-0.45
times the diameter of the shell. It is smooth and lacks lamellae or
protuberances such as characterize the subgenera Crycoiyne and Styloptyx
(Thompson 1971). The dull lusterless shell is light brown or tan in color, in
contrast to the glossy white shells of Crycoryne, Styloptix, and most species of
Coelostemma s. s. The growth form of the embryonic whorls and the broad,
flat-faced peristome are unique features of Goniapex.
THOMPSON: HOLLOW-RIBBED LAND SNAILS
SHELL
WIDTH
SHELL
LENGTH
APERTURE
HEIGHT
APERTURE
WIDTH
ANGLE OF
APERTURE
Figures 1, 2.-- Shell measurements of cylindrical land snails.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
Relationships are difficult to determine within the morass of genera and
subgenera that comprise the Holospirinae. Goniapex is treated as a subgenus
of Coelostemma because of its enlarged hollow columella. About 15 genera
and subgenera of Holospirinae are currently recognized, all of which are
based upon shell characteristics. Evolutionary convergence in shell characters
has been a common occurrence. The hollow-ribbed species discussed in this
paper are an example of one such convergence in which species of three
different subgenera show this trait. Goniapex is most similar in appearance to
Allocotyphe Pilsbry 1946, a subgenus of Holospira, occurring west of the
Sierra Madre Occidental in Sonora and Sinaloa. The type species, H. (A.)
minima von Martens, has a dull brown shell with hollow axial ribs and has an
enlarged hollow columella (Figs. 9-11). However, the aperture differs from
that of Goniapex by being trumpet-shaped. The growth form of the
embryonic whorls differs by regularly increasing in size, by being acutely
angular at the shoulder and flattened below, and by the embryonic sculpture
which consists of regularly spaced ribs that are overlayed by an open mesh of
granular reticulations (Figs. 5, 6). A single species of Coelostemma s. s. also
has hollow ribs, but other characteristics of the shell indicate relationships
within that subgenus, as is discussed below. Apertaxis Pilsbry 1953 also may
be closely related. The type species, C. (A.) coahuilensis (Bartsch 1906), has
an extended apex, but the embryonic whorls are rounded and the
postembryonic whorls support fine, solid thread-like riblets. The type species
remains too poorly known to allow further interpretations of its phylogenetic
position (Thompson 1971: 298-299).
Large areas of suitable habitat exist in southeastern and eastern
Chihuahua from which no specimens of Goniapex have been collected.
Further field work undoubtedly will discover additional new species in this
group.
Etymology.-- The subgeneric name Goniapex is derived from the
Classical Greek gonia, meaning angle, and apex, in allusion to the unique
form of the embryonic whorls.
Coelostemma pyrgonasta, new species
Bishop Tubeshell
(Figs. 12-14)
Description.-- Shell elongate-elliptical in shape. Cylindric portion
consisting of 4-5 whorls, slightly tapering upward. Apex elongate conical,
containing about 10-11 whorls; first two embryonic whorls distinctly enlarged
and strongly angular peripherally (Figs. 3, 12, 13); apex weakly concave in
outline below embryonic whorls. Last whorl with a short neck extending
THOMPSON: HOLLOW-RIBBED LAND SNAILS
peristome about 1 mm forward (Fig. 13). Neck slightly flattened dorsally,
rounded laterally and below. Shell medium-sized and moderately stocky;
about 15-18 mm long; about 0.28-0.32 times as wide as long. Color light
brown with light tan ribs; peristome white; interior of aperture tan. Shell
narrowly umbilicate. Columella simple and hollow (Fig. 14); slightly concave
within each whorl; widest at base of spire, gradually narrowing below.
Columella 0.30-0.36 times width of shell. Whorls 14.8-16.6; weakly arched
and nearly flattened peripherally. Suture moderately impressed. Embryonic
whorls 2.7-3.2; first 2.5 whorls superficially smooth, followed by oblique,
weak axial riblets. Sculpture on postembryonic shell consisting of narrow,
protracted, arched, hollow axial ribs that are about half as wide as their
interspaces. Ribs narrowest at their upper ends, slightly enlarged at their
bases and only slightly crenulating the suture. Penultimate whorl with 30-48
ribs (41 in holotype). Ribs on last whorl continuing around base and into
umbilicus; forming an angular crest around baso-lateral margin where the
ribs are abruptly reduced in height (Fig. 12). Aperture slightly wider than
high; 0.67-0.73 times width of shell; 0.20-0.23 times length of shell; aperture
opening ovate in shape. Peristome moderately wide and flat; widest in baso-
columellar area, and usually narrowest in parietal-columellar corner. Plane of
aperture lying at an angle of about 15-21 to axis of shell.
Measurements in mm of the holotype and four paratypes (UF 34482)
selected to show variation are as follows.
length width aper.h. aper.w. whorls
Holotype 16.7 5.8 3.6 3.6 15.9
Paratype 14.5 4.5 3.3 3.3 14.9
Paratype 16.6 4.9 3.6 3.6 15.7
Paratype 17.1 5.2 3.4 3.5 16.4
Paratype 17.8 5.0 3.5 3.6 16.0
Type locality.-- NEW MEXICO, Dona Ana County, west-northwest side
of Bishop's Cap Mountain (32" 11' 25" N, 1060 36' 06" W); 5200 ft (1600 m)
altitude, 200 ft (60 m) below the summit. HOLOTYPE: UF 93143;
collected 1 December 1970 by Fred G. Thompson and Artie Metcalf;
PARATYPES: UF 34481 (30), UF 34482 (31), UF 34483 (36), UTEP 9957
(18); same locality as the holotype.
Bishop's Cap is a nearly conical mountain that is capped with a dense
limestone which forms abrupt cliffs about 65 m high surrounding the summit.
Snails were found only in talus at the base of the cliffs, where they were
aestivating on the underside of huge limestone boulders.
Distribution.-- C. pyrgonasta is confined to the uppermost slopes around
the summit of Bishop's Cap Mountain, New Mexico. It is very disjunct in its
distribution from other known species of Coelostemma.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
Remarks.-- This species is readily distinguished by its elliptical-conical
shape, very short neck behind the peristome, low number of whorls, large
number of ribs, the baso-lateral angle formed by the ribs on the last whorl,
and the non-uniform width of the peristome. The slope of the aperture is
greater than is usual for Goniapex. Most specimens have a slope of 20-21' to
the axis of the shell. The general appearance of the shell is more like that of a
large Microceramus than the cylindrical shape that characterizes most other
Coelostemma.
Etymology.-- The species name pyrgonaste is from the classical Greek
pyigos, meaning tower, and nastes, meaning inhabitant, in allusion to the
geographic confinement of this species to the uppermost slope of Bishop's
Cap Mountain. In addition, a vernacular name is proposed for this species.
Coelostemma townsendi (Bartsch, 1906)
(Figs. 15-21)
Holospira (Haplocion) townsendi Bartsch,1906; Proc. U. S. National Museum
31: 145-146; pl. 4, fig. 13.
Haplocion townsendi Bartsch,1943; J. Washington Acad. Sci. 33: 56.
This species was known previously only from the holotype (USNM
109215). The original illustration consists of a photograph of the frontal
view. It is in poor focus and does not depict satisfactorily its characteristics.
A new description is given for the species based on the holotype and
additional material from near the type locality (UF 34490).
Description.-- Shell compact cylindrical-turret in shape; cylindric part of
shell consisting of about seven whorls that are nearly equal in diameter; apex
consisting of about 8-10 whorls that gradually diminish in size forming a
convex spire; first two embryonic whorls conspicuously enlarged and
protruding, forming a slight concavity on spire at this point. Shell medium-
sized, about 15-18 mm long; about 0.26-0.31 times as wide as long. Color of
shell dull tan with nearly white axial ribs; aperture and peristome white. Shell
narrowly umbilicate. Columella hollow, widest near middle of shell (Fig. 18,
21); about 0.27-0.29 times width of shell. Whorls 15.1-18.1, weakly arched
with a moderately impressed suture. Embryonic whorls 2.6-3.1; protruding,
conspicuously angular peripherally. Postembryonic whorls with posteriorly
arched hollow axial ribs that are narrowest apically and widest at their base;
ribs not alternating, nor crenulating suture; ribs about half as wide as their
interspaces; about 31-41 on penultimate whorl (38 in holotype, fide Bartsch
1906). Aperture extended forward slightly on a very short neck (Fig. 19);
lying at an angle of 9-18 to axis of shell; aperture opening circular, slightly
THOMPSON: HOLLOW-RIBBED LAND SNAILS
wider than high. Peristome broadly reflected, nearly uniformly wide around
aperture. Aperture 0.68-0.85 times width of shell, 0.18-0.22 times length of
shell.
Measurements in mm of the holotype and five specimens selected to
show variation are as follows.
length width aper.h. aper.w. whorls
Holotype 16.3 4.5 3.6 3.3 15.0
UF 34490 15.1 4.1 3.0 3.1 16.2
UF 34490 16.0 4.8 3.3 3.3 16.7
UF 34490 17.0 4.6 3.6 3.6 17.6
UF 34490 17.8 4.6 3.9 3.9 18.1
UF 34490 18.4 4.7 3.3 3.2 18.2
Type locality.-- CHIHUAHUA, Cerro Chilicote, (28 47'W, 106 05'N);
HOLOTYPE: USNM 10925; collected by C. H. T. Townsend. Cerro
Chilicote is a low peak on a low limestone range extending NNW-SSE, and is
approximately 20 km north of Chihuahua City and due east of the pueblo of
Alamida.
Specimens examined.-- CHIHUAHUA, 5 km NNE Chihuahua (UF
34490, 68 specimens; Museo Nacional de Mexico, 10 specimens; UTEP, 10
specimens). The holotype was also examined.
Distribution.-- Known only from the two localities cited above.
Remarks.-- This snail is distinguished from other species of Goniapex by
its compact cylindric-turret shape, its more numerous ribs per whorl, and the
slight forward projection of the aperture. The series of 68 specimens before
me from 5 km NNE Chihuahua (UF 34490) are similar to the holotype in all
respects. The locality from which the specimens came is separated from the
type locality only by a distance of about 12 km and is on the same limestone
ridge.
Bartsch (1906: 145-146) placed townsendi in Haplocion on the basis of
its smooth columella, even though he noted that it is enlarged and hollow in
contrast to typical Haplocion, which has a solid slender columella. In
addition, the configuration of the embryonic whorls differs from that of
Haplocion. In typical Haplocion the embryonic whorls are low and weakly
rounded.
Coelostemma freytagi Bartsch, 1950
(Figs. 22-29)
Coelostemma freytagi Bartsch, 1950; J. Washington Acad. Sci. 40: 265; figs. 1.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
Coelostemma mantsi Drake, 1951; Revista Sociedad Malacologica 8: 39-40;
figs 1-2.
This species was described by Drake as Coelostemma marrsi on the basis
of advice by Bartsch that it represented a new species. Almost concurrent
with Drake's description, but slightly earlier, Bartsch described the species as
C. freytagi. The holotype of freytagi has a complete apex and is in nearly
perfect condition (Figs. 22, 23). Apparently this is the only specimen Bartsch
received from Freytag. The holotype of marrsi has a broken apex and is badly
eroded (Fig. 24). Drake had about 20 specimens in the paratypic series.
Apparently none had complete apices. A new description is given for the
species based upon the study of more extensive material.
Description.-- Shell elongate cylindric-turret in shape. Medium-sized,
about 16.4-21.0 mm long; about 0.21-0.25 times as wide as long. Apex
attenuate; concave in outline along uppermost whorls. Umbilicus rimate or
narrowly perforate. Color light grayish-brown with nearly white ribs;
aperture and peristome white. Columella tubular, weakly concave within each
whorl, about 0.22-0.28 times diameter of shell at widest whorl; widest at base
of apex, narrowing toward base of shell (Fig. 25). Whorls 16.1-20.1, weakly
arched with a moderately impressed suture; suture weakly crenulated at base
of ribs. Embryonic whorls 2.7-3.3; first two smooth, next embryonic whorl
with weak axial riblets that gradually increase in size. Following whorls
sculptured with large, hollow, oblique ribs that are higher than wide and are
about half the width of their interspaces; ribs more crowded toward apex,
more widely spaced below; ribs weakly reversed-sigmoid, narrowest at their
apex and enlarged at their base; 17-25 ribs on penultimate whorl holotypee of
freytagi, 20; holotype of marrsi, 25). Aperture projected forward on a
moderately long neck that is about 1/4 as long as diameter of last whorl; neck
rounded peripherally and below, flattened above and forming a rounded
angle dorso-laterally. Aperture opening broadly ovate, about as wide as high.
Peristome broadly expanded, flat, equally wide around aperture. Width of
aperture about 0.75-0.88 times width of shell; height about 0.16-0.21 times
length of shell. Aperture lying at an angle of about 7-14 to axis of shell in
lateral profile (Figs. 29).
Measurements in mm for the two holotypes and five other specimens
(UF 34485) selected to show variation are as follows.
length width aper.h. aper.w. whorls
freytagi 17.7 4.1 3.6 3.3 18.1
marrsi 18.2 4.6 3.4 3.3 14 +
UF 34485 16.7 4.1 3.3 3.3 16.9
UF 34485 17.7 4.1 3.3 3.5 16.8
THOMPSON: HOLLOW-RIBBED LAND SNAILS
UF 34485 18.1 4.4 3.2 3.3 17.2
UF 34485 19.7 4.5 3.6 3.7 18.6
UF 34485 21.0 4.5 3.4 3.7 20.1
Type localities.-- Coelostemma fi-eytagi Bartsch 1950: CHIHUAHUA,
29 km west of [Ciudad] Jimenez; HOLOTYPE: USNM 601851; collected
by George F. Freytag. Coelostemma marrsi Drake 1951: CHIHUAHUA,
Cueva Diablo, near Salaices; HOLOTYPE: USNM 601645; Collected by
Robert J. Drake, 18 August 1947. Both localities are in the Sierra Almoloya.
Specimens examined.-- I examined the holotypes of both fleytagi and
man'si. The following specimens from the Sierra Almoloya were also studied.
CHUHUAHUA: 4 km N of Salaices, 1450 m alt. (UF 34485, 41 specimens);
5.7 km WSW, 3 km N Salaices, 1600 m alt. (UF 34486, 22 specimens; Museo
Nacional de Mexico, 10 specimens).
Distribution.-- Apparently this species is endemic to the Sierra
Almoloya. This is a low limestone range that is about 6 km wide and lies just
a few kilometers north of Salaices. The range is also inhabited by two other
endemic land snails, Oreohelix almoloya Drake 1949 and Haplocion greggi
(Drake 1951). The latter species was described as Coelostemma greggi (Drake
1951: 40-41), but the slender, solid axis, as well as all other aspects of the shell
clearly place it in Haplocion (Thompson 1971: 269).
Remarks.-- This snail is identified by its relatively slender shape, its
moderately attenuate, concave apex, the low number of ribs on the
penultimate whorl, and the relatively long neck behind the aperture.
Apparently the species is most closely related to C. reiteri Drake because of
the shape of the apex and its crenulated suture.
Coelostemma reiteri Drake, 1951
(Figs. 30-34)
Coelostemma reiteri Drake, 1951; Revista Sociedad Malacologica 8: 41-42;
figs. 5-6.
Description.-- Shell obese, turret in shape with a moderately attenuate
apex; Upper portion of spire strongly concave in outline. Cylindric portion of
shell barrel-shaped, consisting of about six whorls. Apex consisting of about
13-17 whorls that gradually decrease in size and form an extended concave
spire. First two embryonic whorls strongly angular at periphery and
noticeably larger than next two whorls. Shell large, about 19-24 mm long;
about 0.25-0.33 times as wide as long. Last whorl with a short neck; length of
neck about 1/6-1/3 the diameter of last whorl. Neck rounded laterally and
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
below, weakly compressed above; upper ends of ribs forming a weak angle
along dorso-lateral margin of neck. Color light brown with nearly white ribs;
aperture and peristome white. Columella hollow; broad and club shaped;
about 0.31-0.44 times width of shell; weakly concave within each whorl.
Columella widest at base of apex, tapering gradually to last whorl; surface of
columella sculptured with numerous minute granules. Whorls, 18.1-23.1;
moderately arched with a moderately impressed suture. Embryonic whorls
3.0-3.5. Postembryonic whorls sculptured with numerous protracted,
posteriorly arched, hollow ribs that are almost as wide as their interspaces,
and are slightly higher than wide; 32-48 ribs on penultimate whorl. Ribs
narrow above; widest at their bases which crenulate the suture. Aperture
opening nearly circular, tending to be flattened above. Aperture width about
0.65-0.79 times width of shell; aperture height about 0.18-0.23 times length of
shell. Peristome broadly expanded, flat, nearly uniformly wide around
aperture opening. Plane of aperture lying at an angle of about 11-20 to axis
of shell.
Measurements in mm for the holotype (USNM 601627) and six other
specimens selected to show variation are as follows.
length width aper.h. aper.w. whorls
Holotype 23.7 7.2 4.6 4.9 19 +
UF 34492 19.0 5.7 4.3 4.4 18.2
UF 34492 20.2 5.5 3.9 3.7 19.2
UF 34492 22.1 5.6 4.1 4.1 20.3
UF 34491 21.0 6.3 4.0 4.1 20.6
UF 34491 23.0 5.9 4.3 4.1 22.6
UF 34491 24.0 6.1 4.7 4.8 23.0
Type locality.-- CHIHUAHUA, Distrito Jimenez, Los Remedios (26
53'N, 104 21'W). Los Remedios is a small village at the southeast end of the
Sierra de Los Remedios.
Specimens examined.-- I have examined the holotype and the following
specimens. CHIHUAHUA: Sierra Las Margaritas, 21 km NE Ciudad
Jimenez, 1385 m alt. (UF 34491, 38 specimens); limestone ridge 26 km SSE
Ciudad Camargo, 1260 m alt. (UF 34484, 145 specimens; UF 34492, 59
specimens; Museo Nacional de Mexico, 25 specimens; UTEP 9959, 10
specimens).
Distribution.-- This species occurs in southeast Chihuahua in a series of
low limestone mountain ranges that extend in a linear direction from Los
Remedios northwest to about halfway between Ciudad Jimenez and Ciudad
Camargo.
Remarks.-- This species is readily distinguished by its large, obese size,
its strongly recurved axial ribs, its wide hollow columella, and its nearly round
THOMPSON: HOLLOW-RIBBED LAND SNAILS
aperture opening. Drake (1951: 41-42) selected a specimen with a broken
apex for the holotype. He stated incorrectly that the holotype is 20.4 mm
long and 7 mm wide.
Coelostemma attenuapex, new species
(Figs. 35-39)
Description.-- Moderately large; slender with a very attenuate apex.
Shell about 21-23 mm long; about 0.22-0.24 times as wide as long. Cylindric
portion consisting of about 6-7 whorls. Apex consisting of about 14-16
whorls. Widest point of shell at about 4-5 whorls above aperture. The lower
whorls narrow slightly, and the upper whorls taper gradually into the very
attenuate cone. First two embryonic whorls strongly carinate and
conspicuously larger than next two whorls. Last whorl with a short neck
extending forward for a distance equal to about 1/6-1/3 the diameter of the
last whorl. Color of shell light tan with whitish ribs; aperture and peristome
white. Shell rimate or very narrowly umbilicate. Columella hollow and
ample, about 0.30-0.36 times diameter of shell (Fig. 39); widest at about
middle of shell, tapering slightly below. Columella straight-sided within each
whorl. Whorls, 21.8-23.6. Embryonic whorls, 3.0-3.4. Remaining whorls on
spire and cylindric portion of shell sculptured with large, protracted,
posteriorly arched, hollow axial ribs that are about as wide as their
interspaces; ribs continuing on neck almost undiminished. Penultimate
whorl with 21-29 ribs (29 in holotype). Ribs narrowing above and enlarged at
their bases where they crenulate the suture. Aperture opening broadly ovate
in shape; slightly wider than high. Width of aperture about 0.70-0.82 times
width of shell; height about 0.16-0.20 times length of shell. Peristome very
wide and flat; nearly uniform in width around aperture. Plane of aperture
lying at an angle of about 10-16 to axis of shell.
Measurements in mm of three specimens selected to show variation are
as follows.
length width aper.h. aper.w. whorls emb.wh.
Holotype 22.0 5.0 4.2 4.1 22.2 3.1
Paratype 21.0 5.0 4.1 4.1 21.8 3.3
Paratype 22.3 5.0 3.5 23.2 3.4
Type locality.-- CHIHUAHUA, limestone ridge 12.7 km southeast of
Ciudad Camargo; 1275 m altitude. This locality is along the road to Ojinaga,
and is 2.5 km northeast of old Hwy. 45. The area is covered with a sparse
growth of xeric scrub. Snails were found aestivating under blocks of
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
limestone. HOLOTYPE: UF 93144; collected 25 November 1970 by Fred
G. Thompson. PARATYPES: UF 34488 (23), Museo Nacional de Mexico
(5); same data as the holotype.
Distribution.-- Known only from the type locality.
Remarks.-- This snail is readily distinguished by its size, its very
attenuate apex, its closely spaced ribs, its moderate neck and its relatively
wide columella. It is most closely related to an undescribed species from the
Sierra de Camargo, from which it differs by having fewer ribs and a longer
apex. The material on hand of the latter species (UF 34889) is inadequate for
taxonomic description.
Etymology.-- The name attenuapex is derived from the Latin attenuatus
and apex and alludes to the most striking feature of the species.
Coelostemma bryantwalkeri (Pilsbry, 1917)
(Figs. 40, 41)
Holospira bryantwalkeri Pilsbry, 1917; Nautilus 30: 124-125; pl. 4, fig. 6.
This species is known only from the holotype (UMMZ 140145), which
was found in river drift "along the Rio Conchos, not far above its confluence
with the Rio Grande," CHIHUAHUA. Measurements in mm for the
holotype are: length, 19.5; width, 5.3; aperture height, 4.1; aperture width,
4.2; 14.8 whorls remaining; penultimate whorl with 43 ribs. It has a broken
apex. Three important traits of the specimen are: (1) the ribs are hollow, (2)
the peristome is flat and nearly uniformly wide around the aperture, and (3)
the columella is simple and hollow. These traits indicate the relationship of C.
biyantwalkeri with the other hollow-ribbed species placed in Goniapex. It is
similar in appearance to C. townsendi, but it is larger, has more numerous
ribs, and has a longer neck on the last whorl. The distribution of the species
remains unknown. The Rio Conchos drains a very large area of Chihuahua,
and the holotype could have originated hundreds of kilometers from where it
was found.
Coelostemma Dall, 1895 s. s.
A new species from southern Mexico is described below. It has hollow
ribs, as do the other species discussed above, but its subgeneric relationships
appear to be in Coelostemma s. s. because of the structure of the embryonic
whorls.
THOMPSON: HOLLOW-RIBBED LAND SNAILS
Coelostemma scaphopleuron, new species
(Figs. 42-47)
Description.-- Shell elongate-clavate in shape with a long neck on last
whorl and a short apex with protruding embryonic whorls; greatest width of
shell slightly above middle. Cylindric portion of shell consisting of 8-9 whorls.
Apex short, consisting of about 6-8 whorls; concave in outline below
protruding embryonic whorls. Medium-sized, about 13-18 mm long;
moderately slender, about 0.26-0.31 times as wide as long. Color of shell tan
with light colored axial ribs.; interior of aperture and peristome white.
Umbilicus rimate or narrowly perforate. Columella hollow and tubular, about
0.53-0.59 times diameter of whorl; white with faint, oblique axial thread-
riblets. Whorls 13.6-17.3 (15.2 in holotype), flattened peripherally; suture
moderately impressed. Embryonic whorls 2.6-3.0 (2.9 in holotype); rounded
peripherally with a deep suture (Fig. 48); sculptured with minute granular
reticulations (Fig. 49); last half embryonic whorl with faint axial ribs.
Subsequent whorls sculptured with hollow axial ribs that are about half or a
third as wide as their interspaces and crenulate the suture along their upper
ends (Fig. 8); ribs tend to alternate along the suture; ribs weakly sigmoid on
middle whorls, arched posteriorly on upper and lower whorls and becoming
obsolete on neck of last whorl; 27-38 ribs on penultimate whorl (31 in
holotype). Interspaces between ribs smooth or with scattered minute
granules. Aperture extending forward on a short neck that is about 0.2-0.3
times the diameter of the last whorl; neck flattened above, rounded
peripherally and basally. Aperture slightly wider than high, about 0.65-0.71
times diameter of shell and about 0.17-0.20 times length of shell; lying at an
angle of 8-19 to axis of shell. Interior of aperture auriculate in shape with a
conspicuous parietal tubercular projection near posterior corner that
underlies an elongate indentation externally. Peristome moderately reflected
and trumpet-shaped, not flat-faced as in other species discussed above;
widest along basal and columellar margin; narrowest around posterior
corner.
Measurements in mm of the holotype and four paratypes (UF 34487)
selected to show variation are as follows.
length width aper.h. aper.w. whorls
Holotype 15.4 4.2 2.8 3.0 15.2
Paratype 13.2 4.0 2.5 2.7 14.3
Paratype 14.3 4.4 2.7 2.9 14.9
Paratype 16.3 4.3 2.8 3.0 15.8
Paratype 17.8 4.1 3.1 2.9 17.2
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
Type locality.-- GUERRERO, limestone ridge 1.5 km west-northwest of
Colotlipa (99" 10'W, 17 26'N); 800 m alt. The type locality is the area
adjacent to the Cueva de Colotlipa and is forested with a dense submesic
thicket of trees and shrubs. Snails were found aestivating on exposed
limestone. HOLOTYPE: UF 93145; collected 3 November 1970 by Fred
G. Thompson. PARATYPES: UF 34487 (53), Museo Nacional de Mexico
(5); same data as holotype.
Distribution.-- Known only from the type locality.
Remarks.-- There are no other hollow-ribbed species of Coelostemma s.
s. with which this snail can be compared. However, a close relationship with
C. fusca (Martens, 1897) may exist. C. fusca is a small brown snail that lives
at higher altitudes near Omilteme, Guerrero. Its shell is sculptured with fine,
solid riblets. The embryonic shell-form and sculpture of C. fusca (Figs. 50,
51) are very similar to those of C. scaphopleuron (Figs. 48, 49), contrasting
strongly with the embryonic characteristics of Coelostemma elizabethae
(Pilsbry 1895), the type species of Coelostemma (Fig. 52, 53). A close
relationship between C. fusca and C. scaphopleuron is suggested on this basis.
The Rio Balsas basin of Guerrero and Oaxaca is inhabited by a great
diversity of Coelostemma, all of which currently are placed in Coelostemma s.
s. (Thompson 1971). Pilsbry (1946: 123) erected the subgenus Megaxis for
Holospira fusca Martens 1897. Thompson (1971) synonymized Megaxis with
Coelostemma s.s. on the basis that its characteristics were not sufficiently
distinct to separate the two groups in light of the morphological variation of
some recently described species. Much more field work in the Rio Balsas
basin is required in order to clarify the group relationships of the numerous
species that inhabit the region, and undoubtedly many new species remain to
be described. Eventually it may be necessary to recognize more than one
subgenus in this area.
Etymology.-- The name scaphopleuron is derived from the classical
Greek, skaphe, hollow, and pleuron, rib. The name alludes to the hollow ribs
on the shell. It is the only known species of Coelostemma s. s. that has hollow
ribs.
LITERATURE CITED
Bartsch, P. 1906. The urocoptid mollusks from the mainland of America in the collection of
the United States National Museum. Proc. U. S. Natl. Mus. 31:109-160; pls. 3-5.
1950. A new terrestrial mollusk from Mexico. J. Washington Acad. Sci. 40:265; fig.
1.
Drake, R. J. 1949. A new species of Oreohelix, subgenus Radiocentrum, from southeastern
Chihuahua. Nautilus 62:109-112; pl. 8.
___ 1951. Three new species of Coelostemma from southeastern Chihuahua. Revista
Sociedad Malacologica 8:39-42; pl. 6.
THOMPSON: HOLLOW-RIBBED LAND SNAILS 103
Martens, Eduard von. 1890-1901. Biologia Centrali Americana: Land and freshwater
Mollusca. London. 706 p., 44 pls.
Pilsbry, H. A. 1889. New and little known American molluscs. No. 1. Proc. Acad. Nat. Sci.,
Philadelphia 41:81-88.
_ 1917. A new Holospira from Chihuahua. Nautilus 30:124-125, pl. 4, fig. 6.
_ 1946. Land Mollusca of North America, vol. 2, pt. 1:1-520. Philadelphia.
1953. Inland Mollusca of northern Mexico. II. Urocoptidae, Pupillidae,
Strobilopsidae, Valloniidae and Cionellidae. Proc. Acad. Nat. Sci., Philadelphia
105:133-167.
Thompson, F. G. 1971. Some Mexican land snails of the genera Coelostemma and
Metastoma. Bull. Florida State Mus., Biol. Sci. 15(5):267-302; figs. 1-12.
104
3
Figures 3-8.-- Sculpture of Holospirinae. Figs. 3, 4, 7.- Coelostemma (Goniapex)
pyrgonasta, new species, PARATYPE (UF 34483). Figs. 5, 6.- Holospira (Allocoryphe)
minima Martens, hill 2 km. S Hermosillo, Sonora (UF 93142).- Fig. 8.- Coelostemma (s. s.)
scaphopleuron, new species, PARATYPE (UF 34487). Fig. 3, X 18.7; Figs. 4, 6, X 125; Fig. 5,
X 25; Figs. 7, 8, X 51.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
THOMPSON: HOLLOW-RIBBED LAND SNAILS
0~
'a
W
ix
404W,
vo
^^^^^^^
*HI1* ;
V- ..**^
..Ik-.
^r
Figures 9-14.-- Figs. 9-11.- Holospira (Allocoryphe) minima Martens, hill 1 km S
Hermosillo, Sonora (UF 34496). Figs. 12, 13.- Coelostemma (Goniapex) pyrgonasta, new
species, HOLOTYPE (UF 93143). Fig. 14.- PARATYPE (UF 34482). Figs. 9-14 X 5.
ON:
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
16
17
20
18
21
Figures 15-21.-- Coelostemma townsendi (Bartsch).
20,21.- HOLOTYPE (USNM 109215). Figs. 15-21 X 3.5.
Figs. 15-19.- (UF 34490). Figs.
^w
15
15
\1
19
THOMPSON: HOLLOW-RIBBED LAND SNAILS
22 23 24 25
26 27 28 29
Figures 22-29.-- Coelostemma freytagi Bartsch. Figs. 22, 23.- HOLOTYPE of
Coelostemma freytagi Bartsch (USNM 601851). Fig. 24.- HOLOTYPE of Coelostemma
marrsi Drake (USNM 601626). Figs. 25-29.- (UF 34485). Figs. 22-29 X 3.4.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
32
A
Figures 30-34.-- Coelostemma reiteri Drake (UF 34491). Figs. 30-34 X 3.4.
THOMPSON: HOLLOW-RIBBED LAND SNAILS
35 36 37 38
.'-'.
39 40 41
Figures 35-41.-- Figs. 35-39.- Coelostemma attenuapex, new species. Figs. 35, 38.-
HOLOTYPE (UF 93144). Figs. 36, 37, 39.- PARATYPES (UF 34488). Figs. 40, 41.-
Coelostemma bryantwalkeri (Pilsbry), HOLOTYPE (UMMZ 140145). Figs. 35-39 X 3.9; Figs.
40, 41 X 3.1.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(2):
46
8 Itf
47
Figures 42-47.-- Coelostemma scaphopleuron, new species. Fig. 42.- HOLOTYPE (UF
93145). Figs. 43-49.- PARATYPES (UF 34487). Figs. 42-47 X 5.3.
THOMPSON: HOLLOW-RIBBED LAND SNAILS
50j
Figures 48-53.-- Embryonic shell characteristics of some Coelostemma. Figs. 48, 49.- C.
scaphopleuron, new species, PARATYPE (UF 34487). Figs. 50, 51.- C. fusca (Martens), 10
Km ESE Omilteme, Guerrero, 2100 m alt. (UF 93140). Figs. 52, 53.- C. elizabethae (Pilsbry),
18 km. E Tuxtla, Guerrero, 2000 m alt. (UF 93141). Figs. 48, 50, 52 X 28; Figs. 49, 51, 53 X
142.
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