Myida, Stoliczka, 1870

Order Myida View in CoL Superfamily Pholadoidea

Family Pholadidae Genus Cyrtopleura Tryon, 1862

Cyrtopleura angelicalis Stakowian & Simone , new species ( Fig. 62 View Figure 62 ) https://zoobank.org/ 0648B886-E2EC-4C95-BD1B-CCDB0E6A0864

Barnea (Scobinopholas) costata View in CoL : Morretes, 1949: 49 (non Linné, 1758).

Cyrtopleura costata View in CoL : Rios, 1970: 214, 1975: 254 (pl. 81, fig. 1214), 1985: 273 (pl. 95, fig. 1343), 1994: 295 (pl. 100, fig. 1437), 2009: 592 (fig. 1632); Passos & Magalhães, 2011: 6; Simone, 2019b: 10 (fig. 25); Stakowian & Simone, 2021: 1-7 (figs. 1-2); Passos et al., 2024: 52 (non Linné, 1758).

Types: Holotype MZSP 166519 View Materials , spm . Paratypes: MZSP 143461, 13 spm, 166518, 1 spm (voucher of Stakowian & Simone, 2021) from type locality.

Type locality: BRAZIL. Paraná ; São Miguel do IguaÇÚ, Baía de Paranaguá, Saco do Tambarutaca, near Port of São Miguel , 25°26′07.14″S 48°26′51.7″W [N. Stakowian col., 2018, estuarine mud] GoogleMaps .

Diagnosis: Shell height ~40% of length. Umbones between middle and anterior thirds. Sculptured by ~25 radial, tall threads, highly divergent anteriorly. Dorsal edge posterior to umbo wide. Infra-umbonal appendix broadly angulate (~40°).

Description: Shell of ~ 120 mm, ~2.5 times longer than tall; shell height ~40% of length; length ~2.1× maximum inflation ( Fig. 62A View Figure 62 ). Color white, with thin, dark periostracum mainly preserved among threads. Anterior edge rounded; posterior edge bluntly pointed, almost half of anterior edge; ventral edge widely convex; all these edged undulating because of terminal prominence of radial sculpture, mainly in anterior edge. Umbones weakly prominent, located between anterior and middle thirds of dorsal edge; anterior to it rounded edge as flap of insertion of anterior adductor muscle,outer concavity;posterior to umbo similar edge flap, but ~twice longer and lower; dorsal flaps lacking sculpture. Sculpture ~25 radial threads ( Fig. 62A, B, D, J View Figure 62 ), relatively uniformly spaced, interspaces ~3-times each thread width; each thread composed of successive, blunt nodes; interspaces smooth, only with growth lines; 4-5 anterior threads more spaced and more prominent, extending further shell edge. Inner surface opaque, white ( Fig. 62C, L View Figure 62 ); anterior adductor muscle scar in umbonal region (also working as ligament and abductor muscle); posterior adductor muscle locat- ed in middle region between umbo and posterior end, close to dorsal edge, ~3 times longer than wide; pallial line wide, parallel to shell edge in anterior and middle region, in its region preceding posterior third suddenly turning dorsally, possessing siphonal retractor muscle scar, running as concave line up to posterior adductor muscle scar. Infra-umbonal appendix with base firmly attached, broadly angulate (~40°) ( Fig. 62K, L View Figure 62 ). Metaplax ( Fig. 62E, F View Figure 62 ) with flattened ventro-posterior flap; wide, laterally expanded anterior component, with wide lateral ends and 4 divergent longitudinal folds in middle. Mesoplax ( Fig. 62G, H View Figure 62 ) entirely corneous, thin, flexible, attached almost directly to anterior adductor muscle ( Fig. 62I View Figure 62 : aa), outline slightly triangular, ~1.5 times longer than wide, blunt anterior end; inner scar triangular, occupying most of posterior third area.

Remaining characteristics, including anatomical description ( Fig. 62I View Figure 62 ), see Stakowian & Simone, (2021: 1-7, figs. 1-2).

Etymology: The specific epithet has as inspiration the species′ common name "angel wings", as its shell looks like, from the Latins angelicalis , meaning angelic.

Distribution: From Rio Grande do Norte to Santa Catarina. Brazil.

Habitat: Estuarine, intertidal level; muddy bottoms, buried in sediment up to ~ 1 m deep ( Stakowian & Simone, 2021).

Measurements: Holotype MZSP 143461 ( Fig. 62 View Figure 62 A-I): 105.2 by 42.0. Paratype: MZSP 166518 ( Fig. 62 View Figure 62 J-L): 100.0 by 40.8.

Remarks: Cyrtopleura angelicalis , coauthored by Nicole Stakiwian, was previously identified as C. costata on the Brazilian coast. However, at the time of the publication of its anatomical description ( Stakowian & Simone, 2021), several colleagues brought to our attention that the depicted shells did not entirely match those of the supposedly conspecific northern populations, specifically those from Florida and the Caribbean. One of the more emphatic colleagues was E. Petuch, who even sent a photo of a typical Floridian specimen ( Fig. 62M View Figure 62 ), highlighting that the Floridian "true" C. costata is more elongated and slender, a feature that can also be observed in Caribbean populations. He also emphasized differences in rib count and the structure of the ribs, especially at the anterior end (Petuch, personal communication). Upon studying samples from the Caribbean and Florida regions, we found that these differences were consistent, and we identified additional distinctions, as discussed below.

Cyrtopleura angelicalis is thus formally introduced to the Brazilian population, coauthored by Nicole Stakowian, distinguished from C. costata by its broader valve (shell height approximately 40% of its length, compared to approximately 30% in C. costata ). Additionally, C. angelicalis exhibits around 25 radial threads, while C. costata has roughly 35. Furthermore, the interspaces of the threads in C. angelicalis are wider, approximately three times the width of each thread, whereas in C. costata , the interspaces are narrow, equivalent to the width of the threads themselves. Moreover, the threads are more spaced out and prominent in the anterior region of C. angelicalis compared to those of C.costata . The on common patterns observed in both species. Howevinfra-umbonal appendix of C. angelicalis also differs from er, there is overlap of characters in some rare specimens, that of C. costata ( Fig. 62K View Figure 62 ), being slightly shorter and particularly in the anterior projected threads. The ideal wider, with the base forming an angle of approximate- scenario would be to investigate northern samples of ly 40°. In contrast, the appendix of C. costata is slightly C. costata with the same degree of detail as the Brazilian narrower, with an angle of approximately 30°, and easier C. angelicalis ones (as conducted by Stakowian & Simone, to detach, to the extent that it can be found isolated on 2021), along with DNA sequencing; undoubtedly,further beaches and was described as a peculiar capulid gastro- distinctions would emerge.

pod Capulus shreevei Conrad, 1869 , with the type locality on Long Island, South Carolina ( Conrad, 1869: pl. 13

fig. 3, 3a). Another synonym for C. costata is Leuconyx Superorder Anomalodesmata tyleriana H. & A. Adams, 1863, which lacks a type local- Superfamily Verticordioidea ity and has a scanty description. As no type material has Family Lyonsiellidae been located and there is no indication that this species Genus Lyonsiella Sars, 1872

was based on Brazilian samples, the best course of action Lyonsiella angulosa new species is to maintain it as a synonym of C. costata or possibly ( Fig. 63 View Figure 63 )

consider it a nomen dubium. https://zoobank.org/ C869C843-38B7-4627-BC2D-F7874BCD3A0B The distinctive characters mentioned above between

C. angelicalis and C. costata obviously exhibit some de- Type: MZSP166503, shell (right valve and fragments of gree of variation. The described distinctions are based left valve).

Type locality: BRAZIL. Espírito Santo ; off ItaÚnas, continental slope, 18°59′S 37°50′W, 600-637 m [ MD55 sta. CB76 , Bouchet, Leal & Métivier col., 27.v.1987] GoogleMaps .

Diagnosis: S Atlantic species with prominent umbo as apex of high, blunt carina; outline rectangular. Micro-sculpture as radially aligned nodes.

Description: Shell of ~ 10 mm; wall fragile, slightly translucent; outline slightly rectangular, 1.4 times longer than tall, 2.8 times wider than long (each valve) ( Fig. 63 View Figure 63 A-C). Umbo anterior, subterminal, very prominent; blunt, prosocline; from umbo initiating blunt carina, running obliquely towards ventral and posteri- or, separating posterior slope. Edge anterior to umbo slightly concave, edge posterior to umbo straight, bluntly angled ~150° with straight posterior edge; anterior edge rounded, slightly smaller than posterior; ventral edge vaguely convex. Sculptured by minute nodes radially aligned, ~8 lines per mm in middle region, apparently no concentric alignment ( Fig. 63G View Figure 63 ); each node separated from each other by average space equivalent to 3-times its width. Hinge only in cardinal region, ~ ⅙ of shell length ( Fig. 63D View Figure 63 ); with small, low, sub-umbonal tooth; and posterior thickness flanking ligament ( Fig. 63E, F View Figure 63 ); ligament with narrow intervalvar component, and thick, oblique component (~ ⅛ of shell length) just posterior to cardinal tooth, flanking ventral edge of hinge thickness. Inns surface glossy, slightly iridescent ( Fig. 63B, D View Figure 63 ); muscular scar of difficult individualization, both adductor scars on both ends of dorsal edge; pallial line entire.

Etymology: The specific epithet refers to the angularity of the shell outline, from the Latin angulus.

Distribution: So far known from the type locality.