Two new species of Tornidae (Caenogastropoda, Rissooidea) from Espirito Santo, Brazil
Author
Simone, Luiz Ricardo L.
text
ZooKeys
2012
238
77
85
http://dx.doi.org/10.3897/zookeys.238.3884
journal article
http://dx.doi.org/10.3897/zookeys.238.3884
1313-2970-238-77
Cyclostremiscus mohicanus
sp. n.
Figs 1-15
Types.
Holotype MZSP 106551 (Figs 1-5). Paratypes: 106552, 16 shells from type locality.
Type
locality.
BRAZIL.
Espirito
Santo;
Sao
Mateus, Guriri, 18°47'S, 32°39'W, 3 m depth.
Diagnosis.
Shell of about 2.5 mm; almost planispiral. Three carina-like spiral threads somewhat equidistant; superior surface smooth or with scanty spiral cords. Periphery smooth except threads. Peri-umbilical area with string spiral cords. Periostracum with aligned series of tall rods on spiral threads.
Description.
Shell. Up to ~2.5 mm, discoid; height ~52% of maximum width (Figs 3, 10, 12). Color pure white, weakly translucent (Figs 1, 2, 5, 6). Protoconch of 2 whorls, weakly-turbiform (Figs 4, 10, 11, 15); whorls of rounded profile, suture shallow; surface glossy, smooth; occupying ~10% of shell size; located almost central, weakly dislocated towards right. Transition protoconch-teleoconch unclear (Fig. 15). Spire weakly elevated, with ~45% of shell width; ~15% of shell height. Teleoconch up to 2.5 whorls, uniformly growing weakly planispiral, bearing three somewhat equidistant carinas (Figs 9, 10, 11, 12); peripheral carina as tallest, profile blunt, ~100°, located in middle level of last whorl, inflating ~15% shell width; inferior carina similar to peripheral carina, located midway between this and peri-umbilical slope (Figs 10, 12, 13); superior carina with ~half size as peripheral carina, located midway between this and adjacent suture (Figs 6, 8, 9, 11); between carinas somewhat planar surface, being weakly elevated in
carina's
base. Sculpture superior to peripheral carina absent (Figs 11, 14) to series of narrow, low, obsolete spiral cords (Figs 6, 8), varying from zero (surface smooth, Fig. 14) to ~10 (Fig. 8); interspaces between spiral cords ~1/4 their width; sculpture inferior to peripheral carina absent (smooth). Umbilicum widely opened; maximum diameter ~30% shell width; flanking by strong, somewhat planar slope; sculptured from 1 to 5 spiral cords, with interspaces ~3 times their width (Figs 5, 7, 12, 13). Aperture weakly prosocline (Figs 4, 9, 11, 13); rounded, weakly pentangular, i.e., bearing somewhat equidistant blunt angles produced by three carinas and umbilical slope (Figs 10, 12); with ~35% shell width, ~70% of shell height. Callus practically absent, weakly covering adjacent whorl in apertural implantation.
Periostracum (Figs 1-5). Opaque, transparent, color pale beige. Series of tall rods aligned on three carinas; rods of peripheral carina augmenting ~10% shell width (Figs 1, 2), about twice taller than wide, tip rounded, slightly broader than base; rods of superior carina similar to those of peripheral carina, with ~80% of their size (Figs 3, 4); rods of inferior carina also similar to those of peripheral carina, with ~30% their height and ~60% their width (Figs 3, 5). Each rod blade-like, flexible, located close to each other from same carina, forming tall flexible ridge on each carina. Periostracum ridge on three carinas suddenly finishing at apertural level. On aperture, region between ridge of superior carina and insertion of outer lip in adjacent preceding whorl a small region with ridge of peripheral ridge reabsorbed, forming anal notch with ~1/5 of aperture size (Figs 1, 2, 5).
Measurements (in mm). Holotype: 2.8 by 0.9; paratype 106552 (Fig. 10): 1.7 by 0.8.
Figures 1-15.
Cyclostremiscus mohicanus
sp. n. types 1 holotype MZSP 106551 (W 2.8 mm), apical view 2 same, umbilical view 3 same, apertural view 4 same, apertural-slightly apical view 5, same, apertural-slightly umbilical view 6 paratype MZSP 106552 #1, apical view (W 1.8 mm) 7 same, umbilical view 8 #2, apical view (W 1.7 mm) 9 #1, apertural-slightly apical view 10 same, apertural view 11 #3, SEM, apertural-slightly apical view (W 1.7 mm) 12 same, apertural view 13 same, apertural-slightly umbilical view 14 #4, SEM, apical view (W 1.5 mm) 15 same, detail of apical region, scale 0.1 mm.
Distribution.
Only known from type locality.
Habitat
. Sandy bottoms, 3 m depth (no living specimens).
Material examined.
Types.
Discussion.
Cyclostremiscus mohicanus
is similar to
Cyclostremiscus beauii
(Fischer, 1857) (
Rosenberg et al. 2009
;
Rubio et al. 2011
) from Florida and Caribbean. It differs by the smoother superior surface, lacking so developed spiral cords, the contrary happens in the umbilicum, in such that of
Cyclostremiscus mohicanus
has a series of spiral cords, while
Cyclostremiscus beauii
has
only growth lines; the size is also different, as
Cyclostremiscus mohicanus
has about 3 mm, while
Cyclostremiscus beauii
reaches 9-10 mm.
Cyclostremiscus mohicanus
also resembles
Cyclostremiscus pentagonus
(Gabb, 1873), also from Caribbean, it differs by the more developed spiral sculpture in the superior shell surface, by the peri-umbilical spiral sculpture, in being slightly taller (height/width tax= ~52% against ~48% of
Cyclostremiscus pentagonus
), and in having the peripheral carina slightly more elevated.
Cyclostremiscus pentagonus
has been referred as occurring in south Brazil (
Rios 2009
: 59, in Porto Belo, Santa Catarina;
Rubio et al. 2011
: 91); as that material was not found, this record is here considered doubtful, but possibly they are of
Cyclostremiscus mohicanus
. Another important difference between
Cyclostremiscus mohicanus
and
Cyclostremiscus pentagonus
is the protoconch, it has ~2 whorls (Fig. 15), while that of
Cyclostremiscus pentagonus
is ~0.5 whorl longer (
Rubio et al. 2011
, fig. 46F).
Cyclostremiscus mohicanus
is also somewhat similar to
Cyclostremiscus trilix
(Bursh, 1885), sharing the size and the carinas shape; however, it differs from that species in lacking the microtubercles on the protoconch, in having spiral sculpture in surface between suture and superior carina, and in being taller (height/width tax= ~52% against ~42% of
Cyclostremiscus trilix
).
The periostracum bearing expansions are relatively common in living and fresh-died specimens of tornids. However, a periostracum with the
Cyclostremiscus mohicanus
arrangement appears to be novelty. Nothing like that has been found in other congeneric species.
Cyclostremiscus mohicanus
clearly belongs to the "group 1" as defined by
Rubio et al. (2011
: 84), which encompasses carinate species of the genus, with 2 or 3 peripheral carinas. Possibly all carinas of those species are base of periostracal expansions like those of
Cyclostremiscus mohicanus
.