Glyptobairdia trinodosa Teeter, 1975

Maddocks, Rosalie F., 2022, Taxonomic applications of the esophageal flapper valve in Bairdoppilata and Glyptobairdia (Bairdiidae, Ostracoda), with comments on anatomy, ontogeny, and geography, Zootaxa 5175 (3), pp. 301-342 : 335-338

Glyptobairdia trinodosa Teeter, 1975

( Figs. 20 , 21A–J )

1975 Bairdoppilata (Glyptobairdia) trinodosa Teeter , n. sp.: p. 421, figs. 3h, 4f.

1983 Bairdoppilata (Glyptobairdia) binodosa [sic] Teeter.—Palacios-Fest et al., table 1.

1988A Glyptobairdia trinodosa Teeter. —Bold, table 2, p. 150.

Material: Sixteen subfossil carapaces and valves from near-reef sediments of the carbonate platform of Belize and Honduras.

Dimensions: Dry carapace specimen 4083W, LVL 0.720 mm, LVH 0.431 mm, RVL 0.708 mm, RVH 0.351 mm. Teeter reported carapace dimensions of L 0.70 mm, H 0.40 mm.

The H:L clusters for G. trinodosa ( Fig. 21 ) are more compact than those for G. coronata , in part because fewer specimens were recovered from fewer localities. It is likely that females are longer and higher than males, but without soft parts this cannot be confirmed. The clusters of G. trinodosa ( Fig. 20 ) overlap with the lower and middle parts of the clusters for G. coronata ( Fig. 17 ), approximately equivalent to the Florida population of that species.

Anatomical Remarks: The subfossil valves are colorless, transparent to translucent, with a sugary texture and no opaque pattern. The two dorsal ends of the U-shaped central ridges on the lateral surfaces are thickened or flare into sharp crests ( Figs. 21A–H ). A large round node is isolated a little above the gap between these ends. A second node is located in the middle of the central space, and the third node is positioned anteroventrally at a little distance from the second. This ornamental configuration is easily distinguished from that of G. coronata .

Teeter mentioned but did not illustrate supposed sexual dimorphism: “Dimorphism present in left valve; posteroventral part of submarginal rim depressed in males, continuous in females.” This feature could not be confirmed in the specimens examined for this report. The “submarginal rim” mentioned by Teeter actually consists of two low, rounded, crescentic (concave-up) folds in the marginal fabric, located in the anteroventral and posteroventral regions. They more or less coincide with the valve margins as seen in lateral view, but not the valve edges. They do not meet at midlength, nor do they extend dorsally. Because of the rather coarse pattern of punctation, which crosses these ridges, small nicks or breaks in the narrow muri may appear to interrupt the ridges in some specimens. These are accidental features, probably post-mortem.

Like that of G. coronata , the RV hinge has prominent, crescentic terminal teeth, which are directed laterally (into corresponding sockets of the LV) and project dorsally above the level of the median hinge-bar ( Fig. 21I ). This is a contrast to the hinge of most bairdioids, in which the ends of the RV hinge-bar are less elevated relative to the median bar and less tooth-like in form. The hinge elements of G. trinodosa display coarse ligamental crenulation, like that of G. coronata ( Figs. 21I–J ).

The soft parts and esophageal valve of this species are unknown.

Taxonomic Remarks: Bold (1974, p. 34) initially suggested that “this may be no more than a local variant” of G. coronata , but the differences between these two species are consistent, and specimens are easily sorted where they occur together.

On the Belize platform, Teeter (1975, Table 1 ) reported nine adult specimens plus uncounted juveniles of G. trinodosa at six collecting stations. For G. coronata , he collected eight specimens at four stations, and the two species occurred together in one sample. The occasional co-occurrence of these two uncommon species is confirmed in the near-reef assemblages of Belize and Honduras examined for this report .

Teeter (p. 421) stated that “The presumed juveniles of either this species or B. (G.) coronata indicate a remarkable ontogeny. They have the bairdian outline, show pronounced dorsal overlap, and have a punctate surface; but they lack any indication of the prominent ridges common to the adult.” The “dorsal overlap” he mentioned probably refers to overreach. In his Table 1 , juvenile specimens were recorded at just one station and identified as G. trinodosa , without explanation. Illustrations and dimensions were not provided for the juveniles. No adults of either species were recorded in that sample, and no juveniles of G. coronata were tabulated at any station.

Here, juveniles of G. coronata from collections in the Florida Keys are illustrated for the first time ( Figs. 19 AL). In the subfossil assemblages from Belize and Roatan examined for this report, no juveniles of either species have yet been seen.

Geographic Distribution: G. trinodosa occurs consistently, though never abundantly, in near-reef assemblages of the Belize carbonate platform and Roatan Island (Bay Islands, Honduras). It has been reported as far north as Cozumel on the eastern shelf of the Yucatan platform (Bold 1988A, table 2, p. 150; Palacios-Fest et al. 1983).

Figures

FIGURE 17. Glyptobairdia coronata (Brady). H:L scatter plot for 290 subfossil specimens from 10 Caribbean localities. Because of extreme valve asymmetry, two elongate diagonal clusters are evident: the upper cluster includes 180 LV and carapaces, and the lower cluster represents 110 RV. Adult females tend to plot at the upper right of each cluster, while males plot at the lower left. Separate clusters for instars A–1 and A–2 are represented in the Florida assemblages. In general, specimens from Bermuda tend to be larger, and those from Florida smaller, than those at other localities.

FIGURE 19. Glyptobairdia coronata (Brady), juvenile subfossil specimens from Florida. A–G, specimen 4078WJ, A–2 instar: A, C, E, RV exteriors in transmitted light, showing alignment of punctate ornament, elongate caudal process, terminal spinule, and tiny, irregular posteroventral frill; B, D, F, LV exteriors in transmitted light, showing alignment of punctate ornament, with marginal spinule at anterodorsal corner, zig-zag edges of incipient posteroventral frill, and sinuate caudal process; G, RV exterior in transmitted light, showing sinuate caudal process, with small terminal spinule and zig-zag posteroventral frill; incipient bairdoppilatan dentition is developed as six tiny denticles (or granules) on bend of posterodorsal edge. H, J, specimen 4077RVJ, A–1 instar: RV exterior in transmitted light, showing alignment of punctate ornament, darker NPC, AMS, narrow infold, and absence of calcified inner lamella. I, K–L, specimen 4076LVJ, A–1 instar: LV exterior in transmitted light, at high and low focus, to show delicate network of aligned punctate ornament, darker NPC, AMS, narrow infold, and absence of calcified inner lamella. Scale bar = 50 µm.

FIGURE 20. Glyptobairdia trinodosa Teeter. H:L scatter plot for 19 adult subfossil specimens (1 carapace, 8 LV, 8 RV) from 2 localities. Because of extreme valve asymmetry, LV plot in the upper cluster and RV plot in the lower cluster. Without soft–part control, sexual dimorphism cannot be verified, although it is likely that the longer specimens are females.

FIGURE 21. Glyptobairdia trinodosa Teeter, specimen 4083W. A–B, RV and LV exteriors in transmitted light; C–D, RV and LV exteriors in reflected light; E–F, RV and LV exteriors in transmitted light, with high focus to show incised punctate ornament, bulbous central nodes, and U–shaped central ridge; G–H, RV and LV exteriors in transmitted light, showing details of punctate ornament and nodes in central region; I, RV interior in transmitted light with long hinge, showing crescentic terminal teeth that project dorsally and ligamental crenulation of median bar; J, LV interior in transmitted light with long hinge, showing ligamental crenulation of median groove and pustular texture of dorsal surface. Scale bar = 50 µm.