Polyschides tetraschistus (Watson, 1879)

Simone, Luiz Ricardo L., 2024, New species, misidentifications and problematic taxonomy of some Atlantic South American marine mollusks: a review, Papéis Avulsos de Zoologia 64, pp. 1-104 : 98

Polyschides tetraschistus (Watson, 1879) ( Fig. 65 A-G)

Siphodentalium tetraschistum Watson, 1879: 521 , 1886: 15-16 (pl. 2, fig. 8).

Cadulus tetraschistus : Pilsbry & Sharp 1898: 148 (pl. 23, fig. 1); Henderson, 1920: 3, 12, 96-97 (pl. 17, fig. 1); Morretes, 1949: 52; Lopes & Alvarenga, 1955: 181; Rios, 1970: 143.

Polyschides xavante Caetano & Absalão, 2005: 1-8 (figs. 1-4) (new synonym).

Polyschides noronhensis Simone, 2009: 414-417 (figs. 16-22, 75-86) (new synonym).

Polyschides tetraschistus : Steiner & Kabat, 2001: 448.

Type localities: S. tetraschistum : Challenger sta. 113A: Anchorage off Fernando de Noronha, 7-25 fms [03°57′S 32°24′30″W, 13-46 m]. Polyschides xavante : Sancho Bay (3°51′S 32°26′W), Fernando de Noronha Island, Pernambuco, Brazil, 10- 15 m. Polyschides noronhensis : Porto Beach, 03°50′06.67″S 32°24′10.00″W, 6 m.

Types: S. tetraschistum holotype BMNH 1887.2.9.66 ; P.xavante holotype IBUFRJ 14190. Paratype: MZSP 43518 ; P. noronhensis holotype MZSP 88441 , MZSP 32011 , 3 paratypes (all examined) .

Remarks: A reanalysis of these gadilids, conducted in conjunction with the scaphopod specialist Carlos Henrique S. Caetano (Universidade do Estado do Rio de Janeiro), led me to the conclusion that the three species of Polyschides with a type locality from Fernando de Noronha actually constitute a single biological entity ( Fig. 65 A-G). As discussed in the original description of the three species,they are differentiated by having a very slender shell, with relatively weak central obesity ( Caetano & Absalão, 2005; Simone, 2009). Among the three names (see synonymic list above), priority is given to P. tetraschistus .

A challenge arises concerning the perception that the species is endemic to the Fernando de Noronha oceanic island. However, the former concept of " P. tetraschistus ″ describes a species with a more robust shell, distribut- ed from North Carolina, USA, to Buenos Aires, Argentina. The former concept of P. tetraschistus has three nominal synonyms (MolluscaBase, 2023); the oldest one is Siphonodentalium quadridentatum Dall, 1881 ( Fig. 65H ), from Florida. This species can be revalidated to replace the previous concept, aiming to designate the species with a slightly more robust shell and a broader geographic range:

Figures

Figure 65.Polyschidestetraschistusshells of typespecimens:(A) holotypeof SiphodentaliumtetraschistumBMNH 1887.2.9.66(L 6.6mm),left view;(B)same,dorsal view;(C) same,detail of posterior end;(D-E) holotype of Polyschides xavanteIBUFRJ 14190 (L 5.4 mm), leftand dorsal views;(F)holotype of Polyschidesnoronhensis MZSP 88441, leftview (L 8.6mm);(G) paratype MZSP 46736,detail of posterior region,left view,scale:= 0.25 mm;(H) replication of Dall (1889:pl. 27, fig.5) illustration of Cadulusquadridentatus(L 13.2mm);(I) Polyschidesquadridentatum holotypeMCZ 7739 (L 9.5mm),rightview;(J)same,anteriorview;(K) same,posterior view; (L) replication of Bush (1885: pl. 45, fig. 20) illustration of Cadulus incisus (L 8 mm); (M) ordinary specimen of P.quadridentatum, MZSP 119346 (L 6.1 mm) (from Itaparica,Bahia,Brazil) (courtesyVitor A.Fogarolli),left view;(N) same,dorsal view;(O) same,detail of posterior end,right view,scale:= 1 mm.