Glyptobairdia, Stephenson, 1946

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 : 330-331

Genus GLYPTOBAIRDIA Stephenson, 1946

1946 Glyptobairdia Stephenson : p. 345.

1963 Triebelina Bold. —Morkhoven, p. 34 [part].

Type-species: Bairdia coronata Brady, 1870 [= Glyptobairdia bermudezi Stephenson, 1946 ].

Species Included: The only species for which the soft anatomy has been described, including the esophageal valve, is G. coronata (Brady) (by Rome 1960). The other living species, G. trinodosa Teeter , is known, so far, only by subfossil specimens from the reefs and carbonate platform of Belize and Honduras, and Alacran Reef on the Yucatan platform. Bold (1974) illustrated a fossil RV of Glyptobairdia sp. from the Morne Delmar Formation, Pliocene of Haiti.

Taxonomic Remarks: Several bairdiid genera, including Paranesidea and Triebelina , have some species with robust, asymmetrical carapaces and a densely punctate or nodose surface. From these, Glyptobairdia is easily distinguished by its bairdoppilatan supplemental dentition, the consistent placement of sculptural ridges, the esophageal valve, and the soft anatomy. Glyptobairdia is represented only in the Caribbean region, although some other lineages of ornate bairdiids, such as Triebelina and Havanardia , appear to be circumtropical.

For a time, Glyptobairdia was regarded as a subjective synonym of Triebelina Bold, 1946 . Both genera have highly asymmetrical, heavily calcified, densely punctate carapaces with a tendency to develop ornamental ridges and nodes. The similarities do not extend to the soft anatomy, however, which are of bairdoppilatan aspect in Glyptobairdia and of unique character in Triebelina . Various views in this controversy were summarized by Morkhoven (1958), Rome (1960), Maddocks (1969), Bold (1974), Malz & Lord (1988), Warne (1988) and Maddocks & Wouters (1990). The similarities arise from convergence, presumably, as species of both lineages live in high energy habitats near the reef front. Bold (1974) emphasized that ornate bairdiids are polyphyletic and have arisen multiple times in geologic history, providing examples of heterochronous parallelism.

The RV hinge of both species of Glyptobairdia has unusually prominent, crescentic terminal teeth, which are directed laterally (into corresponding sockets of the LV) and which extend dorsally above the level of the median hinge-bar ( Fig. 21I ). This is a contrast to the hinge of Bairdoppilata and most other bairdioids, in which the ends of the RV hinge-bar are less elevated relative to the median bar and less distinctly demarcated from it. Doubtless, the exaggeration of this feature serves to anchor the axis of rotation securely in these asymmetrical, robustly calcified animals.

Bold (1974) doubted whether instars of Glyptobairdia can be distinguished consistently from those of other bairdiids in a subfossil assemblage. Teeter (1975, p. 421-422, discussing G. trinodosa ) mentioned that instars of Glyptobairdia have the bairdian outlines, valve asymmetry, and punctate ornament of the adult, but they lack any indication of the thick carapace ridges. He did not measure or illustrate these instars, nor did he explain how he identified them as G. trinodosa rather than G. coronata .

Measurements and photographs of the A–1 and A–2 instars of G. coronata are published here for the first time. These juvenile specimens are from a subfossil assemblage in the Florida Keys, which also yields abundant adults of G. coronata but not G. trinodosa . No instars of G. trinodosa have yet been recognized in the samples examined for this report.

Figures

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.