Heterocyathus alternata Heterocyathus alternatus Heterocyathus aequicostatus Azooxanthellate Scleractinia (Cnidaria, Anthozoa) from South Africa Filander, Zoleka N. Kitahara, Marcelo V. Cairns, Stephen D. Sink, Kerry J. Lombard, Amanda T. ZooKeys 2021 2021-10-28 1066 1 198 Verrill, 1865 Verrill 1865 Anthozoa Caryophylliidae Heterocyathus CoL Animalia Heterocyathus alternatus Scleractinia 0 1 Cnidaria species alternatus   Fig. 4A, B   Heterocyathus alternataVerrill, 1865: 149  Heterocyathus alternatus . -Folkeson 1919: 10-11, pl. 1, figs 10-11 . -Hoeksema and Best 1991: 230-231, figs 12-18. - Cairns 1998: 384, fig. 3D-E. - Cairns 1999a: 99-100, fig. 14E-F . -Cairns 2004a: 281.  Heterocyathus aequicostatus. - Boshoff 1981: 37 (in part).  Type locality. Gaspar Straits, between the Bangka and Belitung Islands, Sumatra, (Indonesia); depth unknown (Hoeksema and Best 1991).  Type material. The holotype is deposited at the YPM (Hoeksema and Best 1991).  Material examined.  SAMC_A073105 ( 1 specimen): Easternmargin, 36 kmfrom Cape Vidal/ 32 kmoff Mgobezeleni Estuary, 27°48'54.00"S, 32°38'24.00"E;    52 m.SAMC_A073126 ( 5 specimens): Easternmargin, 25 kmfrom Cape Vidal/ 23 kmoff St Lucia Estuary, 27°54'42.11"S, 32°36'42.11"E;   42- 50 m.SAMC_A073214 ( 1 specimen): Easternmargin, 37 kmfrom Cape Vidal/ 32 kmoff Mgobezeleni Estuary, 27°48'47.88"S, 32°38'53.87"E;    50 m.SAM_H2808 ( 10 specimens): Easternmargin, 20 kmfrom Cape Vidal/ 22 kmoff St Lucia Estuary, 27°59'04.99"S, 32°40'08.00"E;    550 m.SAM_H3118 ( 19 specimens): Easternmargin, 2 kmfrom Durban/ 8 kmoff Umgeni Estuary, 29°52'00.00"S, 31°00'00.00"E;    99 m.SAM_H3119 ( 1 specimen): Southernmargin, 3 kmfrom Plettenberg Bay/ 2 kmoff Piesang Estuary, 34°03'06.80"S, 23°22'48.65"E;   30- 35 m. ORI_DIIIe1_1 ( 1 specimen): Localitydata unknown.  Description. Corallum squat, free, and with aboral or lateral efferent pores smaller than 1.5 mm in diameter. Base flat, but a prominent pore result in an asymmetric corallum. Calice circular to elliptical (GCD:LCD = 1.0-1.1). Largest specimen examined (SAMC_A073126) 9.5 x8.6 mm in CD, and 6.4 mm in H. Costae well-defined, finely granulated, and usually unequal in width. C1-2 sometimes slightly narrower than other costae. Intercostal striae relatively deep but disappear towards base. Base finely granulated. Central part of corallum darker than costae and associated septa. Septa loosely packed and having a star-like appearance, hexamerally arranged in four complete cycles according to the formula: S1> S2> S4> S3 (48 septa). S1 highly exsert, each bearing two or three paliform lobes. S2 slightly less exsert than S1. S3 smallest septa, not as exsert as S1-2, and bearing one or two paliform lobes. S4 wider than S3 and bears four or five paliform lobes, which are distinguishable from columellar elements. At calicular margin, S4 fuses to adjacent S1-2 forming prominent lancets. All septa appear to have straight axial margins, with granules arranged perpendicular to septal faces. All paliform lobes cylindrical, rising slightly above columellar elements, with traces of small and sparsely arranged granules. Fossa relatively deep, containing a papillose columella composed of 5-20 cylindrical elements.  Distribution. Regional: Southern to eastern margin of South Africa, from Plettenberg Bay extending towards Cape Vidal; 30-150 m. Elsewhere: Off Indonesia (Hoeksema and Best 1991 ; Cairns 2004a); Vanuatu; and Wallis and Futuna Islands ( Cairns 1999a); 0-319 m.  Remarks. Examined specimens closely resemble specimens reported by Hoeksema and Best (1991)as  Heterocyathus alternatus. However, some of the examined specimens (e.g., SAMC_A073126) have a darker centre and costal pigmentation, characters which Hoeksema and Best (1991)suggested to be representative of  H. sulcatus(see key from Hoeksema and Best 1991[page 222]). Cairns (1999) also noted specimens of  Heterocyathusthat are conspecific to  H. sulcatus, but lacked pigmentation, and other specimens of  Heterocyathusthat display colouration but are distinctively different from  H. sulcatus. Based on this, we suggest that colouration is of low taxonomic importance. Nonetheless,  H. alternatusclosely resembles  H. aequicostatusamong the South African congers. Apart from the differences in septa and costae profile highlighted in the  H. aequicostatusaccount (see remarks section), the less crowded septa and star-like appearance (a result of S4 inclination towards S3) of  H. alternatusdistinguishes it from  H. aequicostatus. Furthermore, the pali of  H. alternatusare distinguishable from columellar elements in comparison to that of  H. aequicostatus, which are indistinguishable.  Heterocyathus alternatuswas first reported in South Africa by Boshoff (1991), who identified it as  H. aequicostatus(ORI_DIIIe1). Additionally, specimens examined include zooxanthellate representatives (> 40 m) (Hoeksema and Best 2015) and should therefore not be considered in biodiversity assessments focusing on azooxanthellate forms. 2021-01-01 2021-12-31 2021-01-01 Mgobezeleni Estuary -27.814999 Eastern 1 32.640003 Cape Vidal 1 2021-01-01 2021-12-31 2021-01-01 St Lucia Estuary 52 -27.911697 Eastern 1 32.611694 Cape Vidal 5 2021-01-01 2021-12-31 2021-01-01 Mgobezeleni Estuary 46 -27.8133 Eastern 1 32.6483 Cape Vidal 1 2021-01-01 2021-12-31 2021-01-01 St Lucia Estuary 50 -27.98472 Eastern 1 32.66889 Cape Vidal 10 2021-01-01 2021-12-31 2021-01-01 Umgeni Estuary 550 -29.866667 Eastern 1 31.0 Durban 19 2021-01-01 2021-12-31 2021-01-01 Piesang Estuary 99 -34.051888 Southern 1 23.38018 Plettenberg Bay 1 2021-01-01 2021-12-31 2021-01-01 33 Locality 1