Bairdoppilata fithianae, Maddocks, 2025

Bairdoppilata fithianae , sp. nov.

(Graphs 3, 6; Figures 2G–H View FIGURE 2 ; 11A–S View FIGURE 11 ; 12A–X View FIGURE 12 ; 13A–G View FIGURE 13 ; 14A–Y View FIGURE 14 ; 15A–S View FIGURE 15 ; 16A View FIGURE 16 –HH; 32A–H; 33A–I)

? 1880 Bairdia foveolata Brady—Brady , p. 55, pl. 8, figs. 1a–f, 2a–f (part).

? 1960 Bairdia milne-edwardsi Brady—Puri , p. 131, Pl. 6, figs. 14–15.

1974 Bairdoppilata sp. —Maddocks, p. 209 (part; not Pl. 2, figs. 4–7, 18 = Ba. floreana ).

? 1980 Bairdia sp. aff. B. bradyi van den Bold—Fithian , p. 100, Pl. 2, figs. 3a–b. (Unpublished dissertation)

Derivation of Name: For Patricia A. Fithian, who first recognized bairdoppilatan supplemental dentition in this species group.

Material Examined: 169 specimens.

Types: Holotype specimen 4151 LV, USNM 1751266 . Paratype specimens 4152 LV, USNM 1751267 ; 4181 RV, USNM 1751268 ; 4186Car, USNM 1751269 ; illustrated specimens USNM 1751270-1751295 .

Type Locality: UH 2376. Bahamas, off Harbour Lodge Beach, Hope Town, Atlantic Ocean side (east). 26 o 32’N, 76 o 57’W. On Elbow Cay , east of Great Abaco Island , coral reef, water depth 30–35 feet; 100 yards offshore, sandy bottom, non-turbid, within living reef growing on large limestone blocks GoogleMaps .

Occurrence: Bahamas, Bermuda, Cuba, Florida, Flower Gardens, Grand Cayman, Jamaica ( Table 1).

Dimensions: Holotype specimen 4151 LV, L 0.879 mm, H 0.510 mm . Paratype specimen 4152 LV, L 0.907 mm, H 0.519 mm . Paratype specimen 4181 RV, L 0.813 mm, H 0.453 mm . Paratype specimen 4186Car, L 0.845 mm, W 0.394 mm. Paratype specimen 4187Car, L 0.782 mm, W 0.343 mm. See also Graph 3.

Diagnosis: Carapace medium-sized, relatively high; dorsally arched, nearly symmetrical lateral outline, stubby caudal process; opaque patch pattern with oblong central spot and small, circular anterior and posterior spots.

Description: Carapace nearly symmetrical in right-lateral view with moderate dorsal overreach; broadly arched dorsal margin, steeply sloping anterodorsal and posterodorsal margins, gently curved anteroventral margin, and level ventral margin ( Figure 15G, K, M–O View FIGURE 15 ). Caudal process distinct, thick, bluntly terminated, somewhat swollen but not ridged; subtle, perhaps illusory swelling may be present at anterior angle ( Figures 12A, C, E, F, I, L, N, P, R, U, X View FIGURE 12 ; 15A–S View FIGURE 15 ; 16R–V View FIGURE 16 ). Slender in dorsal and ventral view, only slightly swollen medially, with evenly curving lateral margins, acutely tapering anterior end, and more constricted posterior end ( Figure 16A–J View FIGURE 16 ).

LV opaque patch pattern includes dense central spot and two dorsal spots, either separate and diffuse or distinct and connected to central spot by lighter streaks to suggest Y-shape; RV has more oblong central spot and more diffuse dorsal spots; anterior and posterior spots circular, not extended vertically ( Figure 11A–S View FIGURE 11 ).

Ligamental striation on hinge surfaces; well-developed supplemental dentition ( Figure 16P–R, X View FIGURE 16 –AA, DD– HH). Duplicature wide, vestibules narrow or absent ( Figures 11A–S View FIGURE 11 ; 12A–S, U, W–X View FIGURE 12 ; 15J–L View FIGURE 15 ). Selvages nearly straight, edged by brown thread of chitin; flange narrow ( Figures 12S–V View FIGURE 12 ; 15J–L View FIGURE 15 ; 16P–Q View FIGURE 16 ). LV anteroventral and posteroventral margins smooth, or punctate surface ornament may overrun edge as a narrow, scalloped edging; RV anteroventral and posteroventral margins smooth, thickened, very slightly out-turned ( Figures 12A–X View FIGURE 12 ; 16S View FIGURE 16 ).

Juvenile instars with more extended caudal process ( Figure 14A–J View FIGURE 14 ). Opaque pattern of juvenile A-1 instar a broad vertical streak in the LV, with two separate dorsal spots in Y-shape; but broad vertical streak of RV is continuous from ventral to dorsal margin; small anterior and posterior spots ( Figure 14A–B, F–G View FIGURE 14 ). In A-2 instar, central streak narrower, not as dark, with cloudiness in dorsal region of LV but not RV; anterior and posterior spots faint ( Figure 14C–D, H–I View FIGURE 14 ). In A–3 instar, central streak smaller, lighter; anterior and posterior spots missing ( Figure 14E, J, S View FIGURE 14 ).

Juvenile A–1 LV anteroventral and posteroventral margins smooth; RV anteroventral margin with frill, posteroventral margin with tiny spines ( Figure 14A–B, F–G, L View FIGURE 14 ). Juvenile A–2 LV anteroventral margin with frill, posteroventral margin with sharp spines; RV anteroventral and posteroventral margins with uncalcified edge-strip ( Figure 14C–D, H–I, M–P View FIGURE 14 ). Juvenile A–3 LV anteroventral margin with frill; posteroventral margin with sharp, triangular spines ( Figure 14E, J, Q–T View FIGURE 14 ).

Remarks: Ba. fithianae is the most widely distributed species in the present collections. Morphologically it is the most central and least distinctive of the six species in the Ba. fithianae species group. Nevertheless, it is recognizable by its arched, nearly symmetrical lateral outline, stubby caudal process, and opaque patch pattern with circular anterior and posterior spots. Small differences are evident in size and opaque patch pattern between specimens at different localities, which are considered to represent intraspecific variation ( Figure 11A–S View FIGURE 11 ).

On some specimens, the anteroventral and posteroventral edges may be thickened and slightly elevated or out-turned, producing a short reversal of curvature near the margin. In a few specimens, the minutely punctate surface ornamentation overruns the anteroventral and posteroventral margins to form a narrow, scalloped edging. These features resemble the sima and velum of Ba. sima , but they are inconsistently expressed and much less strongly developed. Overreach of the anterior and posteroventral margins in lateral, dorsal and ventral silhouette is normal (LV>RV).

One rather small specimen (4183RV from Jamaica) is considered to be a juvenile A-1 instar, although it has a weakly calcified inner lamella, which is almost as broad as that of the adults ( Figure 14U–Y View FIGURE 14 ). A narrow, thickened rim wraps around all edges of the inner lamella, from the inner margin to the line of concrescence. This specimen is interpreted to be a juvenile that had not yet molted. During molting, the carapace splits along the groove outside this rim (ecdysial suture), and this crescentic plate of weakly calcified inner lamella then separates as an isolated fragment, too fragile to be preserved. These phenomena were discussed briefly by Maddocks (2022, p. 305) for other species of Bairdoppilata .

Brady (1880) reported and illustrated two “varieties” of B. foveolata from a dredging off Bermuda, but on the basis of his drawings, neither of them can be identified with Ba. fithianae .

Puri (1960) reported Bairdia milne-edwardsi Brady, 1869 C, from three stations in Florida Bay, comparing his specimens to the “more typical” of the two forms subsequently illustrated under this name by Brady (1880) from Bermuda. Puri did not provide distinguishing remarks for B. foveolata (mentioned only in his Table 1) and B. milneedwardsi , and it is possible that these are inconsistent appellations for what he considered to be a single species. Bairdoppilatan supplemental dentition was not mentioned. His dimensions (L 0.811 mm, H 0.473 mm) would plot within the lower part of the LV cluster for the population of Ba. fithianae , sp. nov., from Florida (Graph 3). Puri’s drawings (Pl. 6, figs. 14, 15) show points of resemblance to Ba. fithianae , sp. nov.: the moderate LV>RV dorsal overreach, the high-arched but asymmetrical dorsal margin, the nearly level ventral margin, the slightly swollen but not ridged caudal process, and the crisply punctate surface.

Maddocks (1974) reported Bairdoppilata sp. from the Flower Gardens, but specimens of four species were included in the material: Ba. collaevata , Ba. diatreta , Ba, fithianae , and Ba. floreana . The illustrations show Ba. floreana . The statement that “the species is also living on the Bermuda platform” applies only to Ba. fithianae .

Fithian (1980) illustrated the exterior and interior of a RV identified as Bairdia sp. aff. B. bradyi van den Bold. She remarked on the presence of bairdoppilatan supplemental dentition, which (she said) distinguishes this species from Bairdia bradyi and had not been mentioned previously by Bold (1957) and other authors. She also noted similarities to and distinctions from two other species, Bairdia teeteri Allison & Holden, 1971 and Paranesidea bensoni Teeter, 1975 . The lateral outline of the illustrated RV and the dimensions (L 0.83 mm, H 0.45 mm) would be acceptable for Ba. fithianae , although RV are not as easily identifiable as LV, and coating for SEM obscures the opaque patch pattern. She stated that it occurs in coarse sediments around northeastern Trinidad.