Bairdoppilata magnafasciata Maddocks & Horne 2024, n. sp.
Creators: name: Maddocks, Rosalie F.
name: Horne, David J.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Ostracoda
Podocopida
Bairdiidae
Bairdoppilata
Bairdoppilata magnafasciata

description: Bairdoppilata magnafasciata, n. sp.
(Figs 3, 4A–L, 5A–N, 6A–M, 7A–K; Tables 1, 2)
Not 1870 Bairdia fasciata n. sp. -Brady, 193, pl. 19, figs. 20, 21.
? 1966 Bairdia laevicula Edwards —Baker & Hulings, pl. 1, fig. 18.
1975 Bairdoppilata (Bairdoppilata) fasciata (Brady) —Teeter, p. 420, figs. 3g, 4e.
Material Examined: One adult female carapace with dry remnants of soft parts; 318 empty valves and carapaces.
Types: Holotype specimen 4144LV, USNM 1607054, a dry LV from sample UH2744, Belize. Paratype specimen 4141 RV, USNM 1607055, a dry RV from the same sample, Belize.
Type locality: Caye Chappel, Belize carbonate shelf, western Caribbean Sea. Approx. lat. 17 o 41’43”N, Long. 88 o 02’32”W. Inside a sea cave, water depth approximately 25 feet (8 meters).
Derivation of Name: Latin magnus, large; plus fasciatus, banded, striped, bundled.
Dimensions: Holotype specimen 4144LV, USNM 1607054: L 1.096 mm, H 0.655 mm. This valve plots within the lower of the adult clusters (Fig. 3) and is presumed to be from a male. Paratype specimen 4141 RV, USNM 1607055: RV L 1.084 mm, H 0.585 mm. This valve plots within the lower of the adult RV clusters (Fig. 3) and is presumed to be from a male. The dimensions of all illustrated specimens are given in Table 2.
Teeter (1975) reported the following dimensions for carapaces identified as Ba. (Ba.) fasciata: Female: L 1.15 mm, H 0.72; male: L 1.07 mm, H 0.62 mm. His dimensions plot within the adult female and male clusters, respectively, for Ba. magnafasciata (Fig. 3).
The H:L scatter plot (Fig. 3) shows likely size dimorphism, with presumed females being both longer and higher than males but similar in shape. This is a common pattern in bairdiids.
Occurrence: Bahamas, Belize, Cozumel, Cuba, Jamaica, Roatan (Table 1). It may have been illustrated from the coast of Puerto Rico under the name Bairdia laevicula Edwards, 1944 by Baker & Hulings (1966, pl. 1, fig. 18, part of their Assemblage A). The species has been sought but not yet seen in samples from Bermuda, Grand Cayman, the Florida Keys, and the Flower Gardens in the Gulf of Mexico.
Description: Carapace smooth, oblong to lozenge-shaped, slightly inflated medially; highest slightly anterior to midlength in lateral view; thickest at midlength, tapering almost symmetrically to pointed anterior and posterior ends in dorsal view (Figs 4G–H). The amount of LV>RV overreach in right-lateral view is small at the mid-dorsal and mid-ventral margins, even less along the anterodorsal and posterodorsal margins, and nonexistent along the anteroventral and posteroventral margins (Figs 4G, J).
Lateral outline of LV elongate-subovate to obscurely subhexagonal, with broadly and evenly rounded anteroventral margin, long and straight anterodorsal margin, short and sloping mid-dorsal margin, straight and steeply sloping posterodorsal margin, obliquely up-curving posteroventral margin, and nearly horizontal to weakly rounded ventral margin, lacking any ventral indentation (Figs 4B, D, F 5C, I; 6G; 7C, I). Anterodorsal and posterodorsal angles rounded and indistinct; posterior angle obtuse, bluntly rounded, not caudate, lacking any posterodorsal sinuosity above it. Lateral outline of smaller RV necessarily more angulate, with more clearly indicated anterodorsal, posterodorsal, and posterior angles and small ventral indentation (Figs 4A, C, E; 5A, G; 6F, H; 7A, B). In dorsal view the carapace is somewhat inflated medially, thickest at mid-length, with gently curved sides, tapering smoothly and nearly symmetrically to moderately rounded anterior end and slightly more tapered posterior end.
Hinge bairdiid with no special features; thin edge of RV fits into narrow groove of LV, barely widened at anterior and posterior ends (Fig. 5K). Supplemental bairdoppilatan dentition consists of about 6 small denticles on the anterodorsal and posterodorsal edges of the RV; these may be hard to see, because the valve edge is not thickened in this region. The LV has at least 6 small locules located high on the infold just beneath the anterodorsal and posterodorsal overhangs, but the usual thickening of the infold ventral to the locules is not well developed (Figs 5E–F, L–M).
Valve margins smooth, without marginal spines. Marginal infold of moderate breadth with anterior and posteroventral vestibules. RPC and false RPC numerous, radiating laterally outward and superposed near margins. Adductor muscle scar pattern bairdiid, with about 9 scars arranged in 3 rows in a loose rosette (Fig. 7H).
Each valve has a distinctive patch pattern of clear and opaque regions. In the LV the central opaque spot (1) is large, irregularly diamond-shaped, stepped or beveled anterodorsally, with a mid-dorsal extension; within this central spot the region immediately over the muscle scars may be somewhat more transparent, and the more opaque surrounding region may be irregularly J-shaped (Figs 4B, D, F; 5C, I, J; 6G, I; 7C, D, I, K). Other opaque spots in the LV include (2) a small band at the anterior angle, which may be extended diagonally-dorsally as an irregular streak, or which may be accompanied by a second smaller spot of variable shape diagonally above it; (3) two small mid-dorsal spots, which may be connected by a cloudy region to the dorsal extension of the central spot; (4) a posterodorsal spot, circular or irregular in outline, which is separated by a narrow clear band from a cloudy streak along the posterodorsal margin; (5) a small spot at the posterior angle; and (6) an irregular, cloudy or opaque band at the mid-ventral margin. In the RV the pattern of spots is similar, though not perfectly symmetrical, except that the mid-dorsal spots of the LV are absent (Figs 4A, C, E; 5A, G, H; 6F, H; 7A, B). In less well conserved specimens the pattern is more difficult to discern, because of cloudiness, abrasion, and corrosion. The patch pattern is easily recognizable in late juvenile instars, which have smaller but more sharply defined opaque spots and more transparent surrounding fields (Figs 5N; 7E, F, G).
According to a single carapace containing dry remnants of soft parts (specimen 1030F), the anterodistal claw of the A2 is about 2/3 as thick and 9/10 as long as the main claw; both are short and slightly curved (Fig. 6A). The fused claw is thick and smooth. The esophageal plate is wedge-shaped with straight sides and a smoothly curved posterior margin (Figs 6B, D). At least 15 small, conical teeth of equal size are arrayed along its posterior margin, with broad gaps before the small, multilobate corner teeth; this arrangement is usual for the genus Bairdoppilata (Maddocks 2018, 2022). The genital lobe has a relatively thick canal, which coils only through two whorls (Fig. 6C).
Comparisons: Ba. magnafasciata is very similar to Ba. parvafasciata, which also occurs in these assemblages. It differs by its larger size, smaller H:L ratio, more elongate-ovate and less high-arched lateral outline, less distinctly marked posterodorsal angle, the higher placement and non-caudate shape of the posterior angle, and the circular (rather than triangular) shape of the posterodorsal opaque spot. The posterodorsal slope is almost straight to weakly convex and lacks any sinuosity above the posterior angle. The posterior angle is less distinctly marked, more rounded, and is located at about one-third of height, a little higher than in most specimens of B. parvafasciata n. sp. The single, round posterodorsal opaque spot of the patch pattern is a convenient marker for this species, easily distinguished from the wedge-shaped, hanging triangle of Ba. parvafasciata n. sp.
The difference in size is consistent, but the differences of shape are subtle. Care must be taken with sorting adult and juvenile specimens. As is often the case with sympatric congeneric species, adults of the smaller species are approximately the same size as A–1 instars of the larger species. The width of the marginal infold must be verified for every specimen, to avoid mixing adults and juveniles of the two species.
From Bairdoppilata cushmani (Tressler, 1949), which is about the same size and occurs abundantly in the same assemblages (Maddocks 2022), Ba. magnafasciata n. sp. may be distinguished by its less angulate lateral outline, with less exaggerated posterodorsal and caudal angles, and the single posterodorsal opaque spot (rather than two spots).
Bairdoppilata magnafasciata is larger than Ba. cytheraeformis Hartmann, 1974 and not as high, relative to length. In lateral outline it is more elongate, with more rounded contours. The distal antennal claws are of unequal thickness and length, and they taper to points, unlike the equal lengths and rounded tips illustrated for Ba. cytheraeformis.
Bairdoppilata magnafasciata is larger than Ba. vitoriensis Da Luz & Coimbra, 2023 and not as high, relative to length. In lateral outline it is elongate-ovate and has rounded rather than blocky contours.
Remarks: Subtle differences in shape are visible in specimens from different locations (Fig. 3). Multiple specimens from these assemblages are illustrated (Figs 4–7) to show the range of variability and likely sexual dimorphism. The population from Roatan is largest overall. The populations from Cuba and the Bahamas are proportionally higher relative to length, with a more truncate posterior end and more resemblance to Ba. parvafasciata than populations elsewhere.
A few specimens in the Bahamas populations show a small anteromedian opaque streak with jagged edges, which may be connected diagonally to the anterior opaque spot. This streak has not been seen in populations from other localities.
Ba. magnafasciata is the larger of the two Caribbean species, the smaller one being Ba. parvafasciata n. sp. (see below). It was probably included by Teeter (1975) in his description of Ba. (Ba.?) fasciata (Brady). Here, it is represented in only one of the four samples from Belize, in lesser numbers than Ba. parvafasciata. Across all of the Caribbean assemblages studied here, it has higher total abundance and occurs in 18 of 29 samples (Table 1). It occurs preferentially in the shallow-water sands of platform and lagoonal environments, rather than in the coarser sands and coralline rubble near a reef tract.
description: Published as part of Maddocks, Rosalie F. & Horne, David J., 2024, " What's in a name? " Bairdia fasciata Brady, 1870, and two new Caribbean species of Bairdoppilata (Bairdiidae, Podocopida, Ostracoda), pp. 371-400 in Zootaxa 5448 (3) on pages 376-384, DOI: 10.11646/zootaxa.5448.3.3, http://zenodo.org/record/11231896