Philobrya sanjuani Urcola & Zelaya, 2021

Urcola, Matias Ricardo & Zelaya, Diego Gabriel, 2024, The Genus Philobrya J. G. Cooper, 1867 (Bivalvia: Philobryidae) In Patagonia And Adjacent Antarctic Waters, Zootaxa 5437 (2), pp. 151-192 : 180

Philobrya sanjuani Urcola & Zelaya, 2021

( Figure 16 )

Philobrya sanjuani Urcola & Zelaya, 2021: 26 , 27, fig. 3.

Remarks: Philobrya sanjuani was recently described by Urcola & Zelaya (2021, p. 26, 27) thus being unnecessary to redescribe it herein. The species is characterized by having a delicate, modioliform shell with short anterior dorsal margin, narrow posterior slope, a microscopically pitted prodissoconch, and a cancellate dissoconch, covered with a thin, yellowish white periostracum, forming fine radial folds. As mentioned in the original description, Philobrya sanjuani is most similar to P. wandelensis ( Fig. 18 ), from which it differs by having a shorter anterior portion of the dorsal margin, more markedly differentiated dorsal slope, narrower radial periostracal folds, and smaller prodissoconch and resilifer (Appendix 1).

Other similar species in general shell outline are Philobrya atlantica ( Fig. 4 ), P. brattstromi ( Fig. 8 ) and small-sized specimens of P. blakeana ( Fig. 6 ). Philobrya sanjuani differs from all these species by having a smaller resilifer, shorter periostracal setae, and a pitted prodissoconch (Appendix 1). Philobrya sanjuani remains at present only known from its type locality, at Shag Rocks, 313 m depth.

Figures

FIGURE 4. Philobrya atlantica. A: syntype (USNM 97057), B‒K: specimens from Santa Cruz Province (B‒F: MACN-In 44414, G‒K: MACN-In 44415). A‒E: outer views right valve (A‒D: with periostracum, E: without periostracum), F: outer view left valve (without periostracum), G: inner view left valve, H: inner view right valve, I: brooded embryo removed from the demibranch of an adult specimen, J, K: hinge plate of a 4.2 mm L specimen (J: left valve, K: right valve). Scale bars A‒H: 1 mm; I: 100 µm; J‒K: 500 µm.

FIGURE 6. Philobrya blakeana. A, I: lectotype of Brachidontes (Hormomya) blakeanus (MMUM EE 7674), B, J‒L, O, P: specimens from Tierra del Fuego (B: MACN-In 44420, J, K, O, P: MLP-Ma 16106, L: MLP-Ma 16108), C‒H, M, N: specimens from Burdwood Bank (MACN-In 44422). A‒C, E‒H: outer views right valve (A, B: with periostracum, C, E‒H: without periostracum), D: outer view left valve (without periostracum), I, J: inner views right valve, K: inner view left valve, L: brooded embryo removed from the demibranch of an adult specimen, M‒O: hinge plates right valve (M: specimen of 7.7 mm L, N: specimen of 5.2 mm L, O: specimen of 3.5 mm L), P: hinge plate left valve (specimen of 3.5 mm L). Scale bars A‒K: 1 mm; L: 100 µm; M‒P: 500 µm.

FIGURE 8. Philobrya brattstromi. A‒C, H, I, L‒N: specimens from Burdwood Bank (A, B, L: MACN-In 44438, C, H, I, M, N: MACN-In 44435), D, F, G, J, K: specimens from Tierra del Fuego (D: MACN-In 44432, F, G: MACN-In 44431, J, K: MLP-Ma 16114), E: holotype (NRM 3894). A‒D, F, J: outer views right valve (A: with periostracum, B‒D, F, J: without periostracum), E, G: outer views left valve (E: with periostracum, G: without periostracum), H: inner view left valve, I: inner view right valve, K: detail of prodissoconch, L, M: hinge plates left valve (L: specimen of 4.9 mm L, M: specimen of 3.3 mm L), N: hinge plate right valve (specimen of 3.2 mm L). Scale bars A‒I: 1 mm; J: 200 µm; K: 100 µm; L‒N: 500 µm.

FIGURE 16. Philobrya sanjuani. A‒C, J, K: paratypes (MACN-In 43524), D‒G: specimens from Shag Rocks (MLP-Ma 16135), H, I, L, M: holotype (MLP-Ma 15115). A, B, D‒G: outer views right valve (A: with periostracum, B, D‒G: without periostracum), C: outer view left valve (without periostracum), H: inner view left valve, I: inner view right valve, J: detail of prodissoconch, K, L: hinge plates right valve (K: specimen of 2.3 mm L, L: specimen of 2.7 mm L), M: hinge plate left valve (specimen of 2.7 mm L). Scale bars A‒I: 1 mm; J: 100 µm; K‒M: 500 µm. (Figures 16A‒C, H‒M are reproduced from Urcola & Zelaya (2021)).

FIGURE 18. Philobrya wandelensis. A, J: syntype (MNHN-IM-2000-31621), B, C, E‒I, K, L: specimens from South Georgia (MACN-In 43523), D: specimen from South Orkney (NMS Z 1921.143.701). A‒C, E: outer views right valve (A‒C: with periostracum, E: without periostracum), D, F: outer views left valve (D: with periostracum, F: without periostracum), G: inner view left valve, H: inner view right valve, I: detail of prodissoconch, J, K: hinge plates right valve (J: specimen of 4.1 mm L, K: specimen of 2.7 mm L), L: hinge plate left valve (specimen of 2.7 mm L). Scale bars A‒H: 1 mm; I: 100 µm; J‒L: 500 µm. (Figures 18A‒L are reproduced from Urcola & Zelaya (2021)).