Bairdiidae, Sars, 1888

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), Zootaxa 5448 (3), pp. 371-400 : 392-393

Bairdiidae of Other Atlantic Oceanic Islands

Remote oceanic archipelagos have fascinated naturalists since Darwin (1839). Their marine faunas are the result of complex interactions of multiple processes, including dispersal, vicariance, adaptive radiation, production of lecithotrophic vs. planktotrophic larvae, ocean circulation, and geologic history, including volcanism, tectonism, and changes in sea level and temperature. The volcanic and tectonic history of oceanic islands in the North and Central Atlantic is associated with spreading of the Mid-Atlantic Ridge, fracture zones, and mantle plumes or hot spots.

The Bermuda platform is an edifice of as much as 200 m of coral reef limestone, founded on the eroded remnant of an Oligocene intraplate (hot spot) volcano ( Coates et al. 2013). It is located on the edge of the Sargasso Sea (32 o 20’N, 65 o 45’W) near the northern limit of hermatypic reef corals, set by the 22 oC winter isotherm. The Ostracoda, Foraminifera and macro-invertebrate communities of Bermuda are of Caribbean derivation, and dispersal via the Gulf Stream is likely. Six bairdiid species in five genera (but no Bairdoppilata ) were described from modern carbonate sediments by Maddocks & Kornicker (1986), Maddocks & Iliffe (1986), Keyser & Schöning (2000), and Maddocks (2021, 2022). None of the three most abundant Caribbean species of Bairdoppilata ( Ba. cushmani , Ba. magnafasciata , n. sp., Ba. parvafasciata , n. sp.) have reached Bermuda. The Genus Bairdoppilata is represented in Bermuda only by three rare species, which have Caribbean affinities.

Madeira (33 o 26’N, 16 o 44’W) and the Canary Islands (29 o 15’N, 16 o 30’W) are ancient hot spot volcanos in the northeastern Atlantic Ocean ( Doniz-Paez et al. 2020; Ramalho 2015). Brady (1911) identified 48 nearshore marine species from Madeira, including B. acanthigera among the 5 species of Bairdiidae . Schornikov & Keyser (2004) described 50 species of Paradoxostomatinae , but no Bairdiidae , from rocky tide pools and the nearshore zone of Madeira and the Canary Islands.

The Azore s are volcanic islands located on fracture zones of the Mid-Atlantic Ridge (25 o 32 ’ W, Long. 37 o 40 ’ N), near a hot spot at the triple junction between the American, Eurasian and African plates ( Gente et al. 2003, Cantner & McFadden 2019). Meireles et al. (2014a, 2014b) described a small ostracod fauna (20 species) from the Azores. It included no Bairdoppilata and only one (misidentified) species of Bairdiidae ( Maddocks 2015) .

The St. Peter and St. Paul Archipelago of Brazil is an uplift of mantle rock exposed in the St. Paul transform fault system of the Mid-Atlantic Ridge (0 o 55’N, 29 o 20’43”W) ( Campos et al. 2022). From these wave-swept, algaeencrusted shoals, Antonietto et al. (2012) and Coimbra et al. (2012) described 13 species, including 2 species of Triebelina and 1 of Neonesidea , but no Bairdoppilata . All were considered to be circumtropical, and their dispersal was attributed to the Equatorial Current.

Rocas Atoll (3.863 oS, 33.806 oW), the only atoll in the southern Atlantic and one of the smallest in the world), is built on a volcanic seamount, 266 km from coast of Brazil, near the northern edge of the South Equatorial Current ( Garcia et al. 2022). Coimbra & Carreno (2012) reported 22 species of Ostracoda from Rocas Atoll, many in open nomenclature, but no Bairdoppilata . The affinities of the identified species were Caribbean or circumtropical.

Trindade Island (20 o 30’S, 29 o 18’W) is an eroded hot spot volcano on the Vitoria-Trindade Fracture Zone, 1,120 0 km from the coast of Brazil ( Monteiro et al. 2022). Coimbra & Carreno (2012) reported 21 species from Trindade Island, mostly circumtropical or in open nomenclature, but no Bairdoppilata .

Ascension Island is a volcano on the Ascension fracture zone, which offsets the Mid-Atlantic Ridge in the South Atlantic Ocean (7 o 56’S, 14 o 22’W) ( British Geological Survey 2023). Here, from small faunules collected in tide pools, Maddocks (1975) described two species of Neonesidea and Triebelina (with circumtropical and Mediterranean affinities), as well as two species of Bairdoppilata (in open nomenclature, not resembling the species described here).

From the mainland of West Africa, there are few records of living Bairdiidae , and comparison of the meager faunal lists shows little commonality with island assemblages. Witte 1993) described four species of Bairdiidae (but no Bairdoppilata ) from beaches of Senegal and Gambia. Keen (1972, no systematics) reported that Bairdiidae make up 15 to 30 percent of the ostracod assemblages at the edge of the continental shelf of Sierra Leone. Hartmann (1974) described three species of Bairdoppilata from Angola at Moçamedes (15 o 10’S, 12 o 15’E). The carapace of one of them ( Ba. cytheraeformis , see above), shows some resemblance to the Caribbean species Ba. parvafasciata .