Philobrya J.G. Cooper, 1867

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 : 156-157

Genus: Philobrya J.G. Cooper, 1867

Synonymy

Bryophila P.P. Carpenter, 1864 (non Treitschke, 1825). Type species Bryophila setosa Carpenter, 1864 (by monotypy).

Philobrya J.G. Cooper, 1867 . Type species: Bryophila setosa Carpenter, 1864 (by monotypy).

Philippiella Pfeffer, 1886 . Type species: Philippiella quadrata Pfeffer, 1886 (subsequent designation by Dell 1964).

Briophila Fisher, 1887 , misspelling for Bryophila P.P. Carpenter, 1864 .

Stempelleria Clasing, 1918 . Type species: Avicula (Meleagrina) magellanica Stempell, 1899 (by monotypy).

Stempellia Odhner, 1922 (as a subgenus of Avicula ) (non Léger and Hesse, 1910. Type species: Avicula (Stempellia) aequivalvis Odhner, 1922 (subsequent designation by Dell 1964, as first revisor).

Stempellaria Dell, 1964 , misspelling for Stempelleria Clasing, 1918 .

Remarks: Carpenter (1864) introduced Bryophila to place a new species he described: B. setosa , overlooking the fact that the name he proposed was a junior homonym of Bryophila Treitschke, 1825 , a genus of Lepidoptera . Cooper (1867) placed Bryophila setosa in a new genus he erected: Philobrya . Although the author did not explicitly state that this genus is a replacement name for Carpenter’s name, the fact that the latter be a junior homonym and the only inclusion of B. setosa by Cooper (1867), makes Philobrya available as substitute name. Malchus (2006) provided the most recent definition of this genus, considering as diagnostic characters: the presence of a tear-drop-shape, the umbo caped by prodissoconch, a posteriorly elongated ligament and resilial groove, a single adductor muscle scar (the posterior one: Fig. 2G–I ) and the hinge plate comprising G1b teeth and lacking of G2 teeth. Urcola & Zelaya (2021) described a peculiar ontogenetic change in the hinge teeth of the type species of Philobrya : the development of G1b teeth in small-sized specimens, and the subsequent disintegration of these teeth along the ontogeny. A similar phenomenon was described by Malchus (2006) for Philobrya brattstromi . The study of the type species of Philippiella Pfeffer, 1886 , Stempelleria Clasing, 1918 , and Stempellia Odhner, 1922 (as part of the present study) revels that all these taxa share the above-mentioned characters. Consequently, these taxa are here regarded as junior synonyms of Philobrya .

The original description of Philippiella accounts for the presence of two muscles scars: one of them located in the “antero-frontal” part of the shell, and the other in the “middle part of posterior margin”. Although Pfeffer (1886) recognized that the muscles scars are hardly visible, both muscle scars are shown in the figures he provided ( Martens & Pfeffer, 1886: pl. 4, figs. 6b and 7). However, the present study reveals that the type species of Philippiella only has one adductor muscle: the posterior one ( Fig. 2G ). The other “diagnostic” characters originally described for Philippiella (i.e., the general shell outline, the thickness and projection of the periostracum, the extension of the ligament, and the lack of hinge teeth in large-sized specimens) are not exclusive characters, but fit within the intraspecific variability of Philobrya .

Clasing (1918) introduced the new genus Stempelleria to place Avicula (Meleagrina) magellanica . Even when Dell (1964: 168) commented on the difficulties for properly recognizing the type species, he included Stempelleria (wrongly referred as “ Stempellaria ”) in the synonymy of Philobrya .As part of this contribution we had the opportunity to study the type species of Stempelleria (see below), and confirm that it does not correspond to Avicula Bruguière, 1792 [currently regarded as a junior synonym of Pteria Scopoli, 1777 ], Meleagrina Lamarck, 1819 [currently regarded as a junior synonym of Pinctada R̂ding, 1798] or Pteriidae (as defined by Tëmkin 2006 and Wada & Tëmkin 2008), a family where both Pteria and Pinctada are currently placed. Instead of belonging to Pteriidae , the type species of Stempelleria proved to be congeneric with the type species of Philobrya . These findings allowed us to confirm the synonymy of Stempelleria with Philobrya .

Odhner (1922) introduced Stempellia (as a subgenus of Avicula ) to place a new species he described from Juan Fernández archipelago( Avicula (Stempellia) aequivalvis )and another already described species: Avicula(Meleagrina) magellanica ; overlooking the fact that Stempellia was already preoccupied for a genus of microsporidian, which had been introduced in 1910 by Léger and Hesse. Dell (1964) wrongly referred to Avicula (Stempellia) aequivalvis as the type species of Stempellia Odhner “by monotypy”. Despite this error, Dell’s (1964) restriction may be regarded as a subsequent designation of the type species of that genus. The study of the holotype of Avicula (Stempellia) aequivalvis (GNM 11968) and more than 500 additional topotypic specimens of this species (Zelaya, Ģller and Bieler, in prep), allowed us to confirm that this species belongs to the genus Philobrya .

Dell (1964) also included Hochstetteria Vélain, 1877 , in the synonymy of Philobrya , probably following the previous placement used by Bernard (1897) for the type species of Hochstetteria . This synonymy was followed by several subsequent authors (e.g., Tevesz 1977, Dell 1990, Malchus 2010). However, Urcola & Zelaya (2021) confirmed that the type species of Hochstetteria ( H. aviculoides Vélain, 1877 ) shows two adductor muscles scars. This condition led to the authors to consider Hochstetteria as distinct from Philobrya .

Tevesz (1977) also considered Notomytilus Hedley, 1916 , and Micromytilus Cotton, 1931 , as synonymous of Philobrya , a criterion followed by Huber (2010). However, a more detailed study of the type species of these genera is needed before accepting this synonymy.

Figures

FIGURE 2. Orientation, measurements, and morphological and anatomical characters of Philobrya species. A: inner view left valve, B: antero-dorsal view, C: detail of the hinge plate, D: prodissoconch, E, F: periostracal projections, G‒I: gross anatomy of specimens in which the right valve was removed (G: P. quadrata, H: P. magellanica, I: P. limoides). Abbreviations: ada, antero-dorsal area; antG1b, anterior series of G1b teeth; ca, central area; G1ba, angle between anterior and posterior series of G1b teeth; H, shell height; L, shell length; Lp, prodissoconch length; p, prodissoconch; pam, posterior adductor muscle; pams, posterior adductor muscle scar; pda, postero-dorsal area; pe periostracum; postG1b, posterior series of G1b teeth; re, resilifer; ri, rim; s, setae; ua, umbonal angle; W, shell width.