Sagenotriphora osclausum ( Rolán & Fernández-Garcés, 1995 )

Fernandes, Maurício Romulo & Pimenta, Alexandre Dias, 2019, Basic anatomy of species of Triphoridae (Gastropoda, Triphoroidea) from Brazil, European Journal of Taxonomy 517, pp. 1-60 : 37-39

Sagenotriphora osclausum ( Rolán & Fernández-Garcés, 1995)

Figs 2I , 24

Material examined

BRAZIL – Bahia State • [2, 2 d] specs; Forte Santa Maria, Salvador ; 0–10 m depth; 13°00´15″ S, 38°32´03″ W; 18 Feb. 2016; M.R. Fernandes leg.; MNRJ 35061 .

Description of basic anatomy

RADULA. Formula 7-1-1-1-7; central tooth and lateral teeth disposed around a central axis, marginal teeth lie in a kind of membrane, oblique to almost perpendicular to the central axis; central tooth resembles a pair of small curved paws, having a single common axis that bifurcates in about 56–62% of tooth length, originating the two halves of tooth, which are separated by an internal diastema (distance between extremities of inner cusps and distance between basal plates constitute respectively 16–24% and 9–14% of total width of tooth), each half of tooth bearing a globose base and four (or even five) short, triangular and sharp-pointed cusps similarly sized, comprising 21–34% of length of the entire tooth half; lateral teeth resemble one half of central tooth, with a robust base and four to five short, triangular and sharp-pointed cusps similarly sized, comprising 34–40% of length of the entire tooth; marginal teeth elongated and developing one behind or above the other in the same row, hindering a proper visualization; M1 to M4 resembling chainsaws, with curved cusps of very small size (in the lower part) or a little longer (upper part) concentrated in the distal portion (16–21% of tooth length) of the long and robust basal plate; M5 and M6 resembling brackens, with at least seven elongated finger-like cusps in the distal portion (25–50% of tooth length) of the long and thin basal plate; M7 with apparently nine or ten cusps very close to each other, almost inseparable; central tooth 8.0–9.0 µm wide, lateral teeth 3.9–4.4 µm wide, M1 to M4 15.6–16.5 µm long, M5 and M6 16.9–18.1 µm long, M7 14.8–17.8 µm long.

Remarks

This is a very unusual radula among triphorids. Rolán & Fernández-Garcés (2008) described six to seven cusps in the lateral teeth of a specimen of S. osclausum from Florida (southeastern USA), more than the four to five cusps herein described ( Fig. 24 C–D), possibly because of better angle views of this globose structure in that work. They described and illustrated only inner marginal teeth that resemble chainsaws (M1 to M4), not having noticed the elongated marginal teeth M5 to M7, which are described in the present study ( Fig. 24F ). In fact, marginal teeth of S. osclausum are extremely difficult to be discerned and quantified, owing to the great overlap among each other.

Despite having similar shell sculpture and protoconch morphology, the radula of S. candidula Rolán & Fernández-Garcés, 2008 , drawn by Rolán & Fernández-Garcés (2008), is quite different from that of S. osclausum , as the authors correctly stated. The marginal teeth of S. candidula are similar to M5 and M6 of S. osclausum ( Fig. 24F ), although apparently with fewer cusps.

The radula of the southwestern Pacific and the type species Sagenotriphora ampulla (Hedley, 1903) , described in Marshall (1983), is radically different from that of S. osclausum , considering both the morphology (shape and number of cusps) of all teeth and the number of marginal teeth (seven in S. osclausum , only one in S. ampulla ). Rolán & Fernández-Garcés (2008) were conservative when avoiding to give a new generic name for the western Atlantic species, arguing for that similarity of the central tooth being divided into two parts in both species might be a convergent feature of minor importance considering the discrepant morphology of the central and remaining teeth. Shell differences are also observed between them, like the embryonic shell sculpture (with vesicular granules in S. osclausum , but reticulated in S. ampulla ) and sculpture of subperipheral/basal cords (mainly smooth in S. osclausum , nodulose in S. ampulla ). Future phylogenies are necessary prior to the creation of a new generic name.

Figures

Fig. 2. Specimens studied. A. Metaxia excelsa Faber & Moolenbeek, 1991 (MZSP 122353). B. Metaxia rugulosa (C.B. Adams, 1850) (BMSM 56034). C. Cosmotriphora melanura (C.B. Adams, 1850) (MNRJ 33980). D. Iniforis pseudothomae Rolán & Fernández-Garcés, 1993 (MZSP 100957). E. Latitriphora albida (A. Adams, 1854) (BMSM 55442). F. Monophorus olivaceus (Dall, 1889) (MNRJ 34615). G. Nanaphora verbernei (Moolenbeek & Faber, 1989) (MZSP 85022). H. Nototriphora decorata (C.B. Adams, 1850) (MNRJ 28941). I. Sagenotriphora osclausum (Rolán & Fernández-Garcés, 1995) (MNRJ 35061). J. Similiphora intermedia (C.B. Adams, 1850) (MNRJ 29763). K. Strobiligera gaesona (Dall, 1927) (MZSP 53685). L. “Inella” harryleei Rolán & Fernández-Garcés, 2008 (FLMNH 450495). Scale bars: 1 mm.

Fig. 24. Sagenotriphora osclausum (Rolán & Fernández-Garcés, 1995), radula. A–F. MNRJ 35061. Scale bars: A–B = 10 µm; C = 5 µm; D–F = 2 µm.