Mitromorpha mirim, Simone & Cunha, 2012

Simone, Luiz Ricardo L. & Cunha, Carlo M., 2012, Taxonomic study on the molluscs collected in Marion-Dufresne expedition (MD 55) to SE Brazil: Xenophoridae, Cypraeoidea, mitriforms and Terebridae (Caenogastropoda), Zoosystema 34 (4), pp. 745-781 : 771-772

publication ID

https://doi.org/ 10.5252/z2012n4a6

publication LSID

lsid:zoobank.org:pub:857CAD31-66E1-4CEE-AB4D-CCD64541D0EF

persistent identifier

https://treatment.plazi.org/id/03AA8317-C652-0D4D-FF7E-9FD7C86A0C9B

treatment provided by

Felipe

scientific name

Mitromorpha mirim
status

n. sp.

Mitromorpha mirim n. sp.

( Fig. 9 View FIG G-K)

TYPE MATERIAL. — Holotype: Brazil, Espírito Santo, off Itaúnas, continental slope of Abrolhos, 18°56’S, 37°52’W, 85-105 m depth, MNHN 25227 ( Fig. 9G, H, K View FIG ) ( MD 55, stn DC 82, Bouchet, Leal & Métivier coll., 28. V.1987). Paratypes: same data as holotype, MNHN 25228, 2 shells, MZSP 102674, 1 shell. — Off Itaúnas, 18°49’S, 37°57’W, 60 m depth, MNHN 25229, 2 shells, MZSP 102683, 1 shell ( Fig. 9I, J View FIG ) (stn DC 83).

TYPE LOCALITY. — Brazil, Espírito Santo, off Itaúnas, continental slope of Abrolhos, 18°56’S, 37°52’W, 85- 105 m depth ( MD 55, stn DC 82).

DISTRIBUTION. — Off Espírito Santo, Abrolhos continental slope.

ETYMOLOGY. — The specific epithet is derived from the South American Tupi-Guarani word “mirim”, meaning small; an allusion to the small size of the shells.

DIAGNOSIS. — Shell length c. 4 mm, fusiform; protoconch paucispiral, broad; sculpture of spiral cords and axial undulations, with subsutural cord larger and dotted. Aperture elongated; outer lip lyrate, inner lip with pair of columellar folds.

DESCRIPTION

Shell: length up to 3.7 mm, outline fusiform ( Fig. 9 View FIG G-J); width c. ½ length. Colour uniform pale beige with perisutural white band. Protoconch whitish, of 1.5 whorls, mammillate ( Fig. 9K View FIG ); comprising c. 10% of length and c. 23% of shell width; surface smooth, glossy; transition with teleoconch clear, orthocline. Spire conic, comprising c. 40% of shell length; spire angle c. 53°. Teleoconch of about four whorls, profile straight to weakly convex, suture plane. Sculptured by spiral cords and axial undulations, forming weak reticulation; c. 18 axial and four spiral cords in penultimate whorl ( Fig. 9H, I View FIG ); c. 18 spiral lines in initial region of body whorl ( Fig. 9G, I View FIG ), with small smooth anterior area close to canal; subsutural line slightly larger and more nodulose. Distinct slope in outer lip short (less than ⅛ whorl) ( Fig. 9J View FIG ); outer lip thicker on thread, becoming thinner towards edge. Aperture elliptic, c. 60% of shell length and c. ⅓ shell width ( Fig. 9G, I View FIG ); c. 3 times longer than wide; weakly oblique related to longitudinal shell axis. Outer lip internally lyrate, with 4-5 spiral inner, weak cords, being upper cord larger, becoming gradually narrower in peri-siphonal region ( Fig. 9G View FIG ). Inner lip slightly concave, possessing pair of low, middle folds, being uppermost fold slightly larger than inferior fold. Siphonal canal short, slightly rostrate, projected forwards and dorsally ( Fig. 9G, I View FIG ). No broad callus or umbilicus.

MEASUREMENTS (inmm). — Holotype: 3.7 × 1.8; paratype MZSP 102683 View Materials : 3.7 × 1.8.

HABITAT. — Sandy-mud bottoms, 60-105 m depth.

REMARKS ON BOTH SPECIES OF MITROMORPHA The generic attribution is based on the shell shape and the presence of a pair of small teeth in the inner lip. The genus was naturally described in Mitridae , based on those teeth. It was transferred to Turridae H. Adams & A. Adams, 1853 afterwards ( DuBar 1958). However, a close resemblance to the costellariid genus Pusia Swainson, 1840 is also clear, based on a set of characters, such as the relative small size, the elongated aperture lyrate within ( Cernohorsky 1970: 55). The number of columellar plicae was decisive for the final decision.

Both Mitromorpha sama n. sp. and M. mirim n. sp. are very similar. They can be distinguished from each other only by some characters. The main one is the size; shells of M. sama n. sp. are almost double in relation to shells of equivalent degree of development of M. mirim n. sp. This feature is shown in Fig. 9L View FIG , where two typical specimens are illustrated at the same scale; the specimen of M. sama n. sp., on the right, and that of M. mirim n. sp. on the left. In Figure 9L View FIG is also clear the differences in size even of the protoconch. Beyond the size, M. mirim n. sp. still differs from M. sama n. sp. by proportionally wider protoconch, by protoconch slightly pointed (compare Figure 9E and K View FIG ), by axial sculpture being mainly by undulation instead of aligned pustules, by more rounded outline, by proportionally longer aperture (c. 60% of shell length, instead of c. 50% for M. sama n. sp.), and by the short distinct slope preceding outer lip (compare Figure 9D and J View FIG ).

The bathymetry is also a distinguishable feature, as Mitromorpha sama n. sp. occurs in 607-940 m depth, and M. mirim n. sp. in 60-105 m depth.

There are no other species in western Atlantic similar to both species described herein. They differ from M. azorensis Mifsud, 2001 , from Azores, by the well-developed sculpture and in lacking reticulate colour spots. They differ from M. biplicata (Dall, 1889) , from Atlantic coast of USA, in lacking so developed axial treads and by much axial sculpture. They differ from M. dormitor (Sowerby, 1844) , from north Caribbean, in having well-developed axial sculpture and by taller spire length. They differ from M. zilpha Dall, 1927 , from Georgia, USA, by darker colour ( M. zilpha is dull white), in having about one more whorl in the teleoconch, and in lacking small shoulder close to suture. Additionally, both species still differ from the local Pusia venusta Sarasúa, 1978 , from Cuba and Colombia, in lacking strong axial sculpture, by its proportional longer aperture, thinner walls, more convex whorls, and pale, uniform colour ( P.venusta is normally orange, with white and black spots) ( Sarasúa 1978; Díaz & Puyana 1994).

Family TEREBRIDAE Mörch, 1852

MNHN

Museum National d'Histoire Naturelle

MD

Museum Donaueschingen

V

Royal British Columbia Museum - Herbarium

MZSP

Sao Paulo, Museu de Zoologia da Universidade de Sao Paulo