Coelastrea, VERRILL, 1866: 32

Huang, Danwei, Benzoni, Francesca, Fukami, Hironobu, Knowlton, Nancy, Smith, Nathan D. & Budd, Ann F., 2014, Taxonomic classification of the reef coral families Merulinidae, Montastraeidae, and Diploastraeidae (Cnidaria: Anthozoa: Scleractinia), Zoological Journal of the Linnean Society 171 (2), pp. 277-355 : 302-304

GENUS COELASTREA VERRILL, 1866: 32 ( FIG. 8 )

Type species

Coelastrea tenuis Verrill, 1866: 33 ; original designation, Verrill, 1866: 33.

Original description

‘Corallum massive, cellular, fasciculate, formed by prismatic coralites [sic] intimately united by their walls which are thin and simple. The exterior of the corallum is destitute of an epitheca, lobed and distinctly costate like that of Metastrea . The cells are polygonal, often closed below by the dissepiments, which, occuring [sic] at the same level, unite from all sides forming thus transverse septa. In a transverse section traces of a very rudimentary and loose columella are seen in some cells. Septa in three or four cycles, unequal, the inner edges prolonged into strong paliform teeth.

The polyps increase by fissiparity, and near the margin by disk-budding. This genus appears to bear the same relation to Goniastrea that Metastrea does to Prionastrea , differing from it in the absence of epitheca and the lobed and striated exterior, thinness of the walls, and rudimentary columella. From Metastrea it differs in the last character, and in its mode of increase as well as in the coincidence of the dissepiments and the strong pali.’ ( Verrill, 1866: 32). Subsequent descriptions

Leuckart, 1869: 214; Vaughan, 1907: 104; Vaughan & Wells, 1943: 168; Chevalier & Beauvais, 1987: 714.

Diagnosis (apomorphies in italics)

Colonial, with intracalicular budding only. Corallites monomorphic and discrete (one to three centres); monticules absent. Coenosteum costate, limited amount (includes double wall) or fused walls. Calice width medium (4–15 mm), with medium relief (3–6 mm). Costosepta not confluent. Septa in ≥ four cycles (≥ 48 septa). Free septa regular. Septa spaced six to 11 septa per 5 mm. Costosepta equal in relative thickness. Columellae trabecular and spongy (> three threads), <1/4 of calice width, and continuous amongst adjacent corallites. Septal (multiaxial) lobes well developed. Epitheca well developed and endotheca low−moderate (tabular) ( Fig. 8A, D, G ).

Tooth base at midcalice circular. Tooth tip at midcalice irregular; tip orientation perpendicular to septum. Tooth height medium (0.3–0.6 mm) and tooth spacing medium (0.3–1 mm), with> six teeth per septum. Granules scattered on septal face; irregular in shape. Interarea palisade ( Fig. 8B, E, H ).

Walls formed by dominant paratheca and partial septotheca; trabeculothecal elements may be present; abortive septa absent. Thickening deposits fibrous. Costa centre clusters weak; 0.3–0.6 mm between clusters; medial lines strong. Septum centre clusters weak; 0.3– 0.5 mm between clusters; medial lines strong. Transverse crosses present. Columella centres clustered ( Fig. 8C, F, I ).

Species included

1. Coelastrea tenuis Verrill, 1866: 33 ; holotype: YPM IZ 476 (dry specimen; Fig. 8A ); type locality: ‘Sandwich Islands?’ ( Verrill, 1866: 33); phylogenetic data: none.

2. Coelastrea aspera ( Verrill, 1866: 32) ; syntypes: USNM 402 , 403 (two dry specimens; Fig. 8B–D ); type locality: Ryukyu Islands , Japan; phylogenetic data: molecular and morphology .

3. Coelastrea palauensis (Yabe & Sugiyama in Yabe et al., 1936: 30, pl. 19: figs 5, 6); holotype: TIU 56631 (dry specimen; Fig. 8G ); type locality: Palau; phylogenetic data: molecular and morphology .

Taxonomic remarks

Coelastrea was described by Verrill (1866: 33) based on the type specimen of Coelastrea tenuis collected by Dana during the US Exploring Expedition (1838– 1842). The original museum label states ‘Sandwich Islands?’, referring tentatively to Hawai’i. The genus description was subsequently reproduced in Leuckart (1869: 214) and Vaughan (1907: 104, pl. 26: figs 2, 2a). The latter furthermore repeated Verrill’s description of the species, which was listed by Studer (1901: 398) as one of several species from Hawai’i described by Verrill. An unidentified Coelastrea sp. from the locality was also figured in Bryan (1915, pl. 111: fig. 12). Coelastrea was recognized as a distinct genus in Vaughan & Wells (1943: 168) with a note regarding its type locality being ‘reputedly the Hawaiian Islands’. It was later synonymized by Wells (1956: F402) with Goniastrea . The status of the type species was not addressed, although it was presumably transferred into Goniastrea . More recently, Chevalier & Beauvais (1987: 714) listed Coelastrea as a valid genus and added Malaysia to its known range. However, there is much doubt that any living specimen has been collected since the initial description, certainly not in Hawai’i (D. Fenner, pers. comm.) where Goniastrea is not known to be present ( Veron, 2000; Veron et al., 2009). Records of live Coelastrea tenuis being exported out of El Salvador in the eastern Pacific and an unspecified locality in the USA between 1996 and 1997 were reported by CITES (2001), but these were not substantiated by voucher collections and thus most likely misidentifications. Fossil corals from the Plio-Pleistocene of Nias, an island off western Sumatra, Indonesia, were attributed to this species as Goniastrea tenuis by Boekschoten et al. (1989: 118), along with Goniastrea edwardsi and Goniastrea pectinata .

We posit that Coelastrea tenuis may have been identified as Goniastrea aspera Verrill, 1866: 32 , in more recent treatments, but without a more extensive investigation, we are unable to verify the species status of Coelastrea tenuis . On the bases that Goniastrea aspera and Favia palauensis Yabe & Sugiyama, 1936: 30 , pl. 19: figs 5, 6, match Coelastrea tenuis in nearly all macromorphological characters (i.e. lack of spongy columellae in Coelastrea tenuis ), and that they are distinct from the rest of the Goniastrea on both molecular and morphology trees, we resurrect the genus Coelastrea and transfer these species into it.

Coelastrea is widely distributed on reefs of the Indo- Pacific, and absent in the eastern Pacific. It is also not likely to be found in Hawai’i, as no living Coelastrea tenuis has been positively identified from Hawai’i and eastwards.

Morphological remarks

Coelastrea is a well-supported clade on the morphology tree, with bootstrap support of 86 and decay index of 2. Two synapomorphies have been identified for this genus: limited coenosteum or fused walls (likelihood of 0.60 based on the Mk1 model) and presence of regular free septa (likelihood 0.98). These apomorphies distinguish it from closely related genera, in particular Dipsastraea and Trachyphyllia , but they are also present in part amongst Goniastrea . Most Goniastrea spp. have fused walls, and regular free septa are present in Goniastrea retiformis and Goniastrea stelligera . Other characters, mostly subcorallite ones, are more useful for separating Coelastrea and Goniastrea , e.g. more septa (≥ four cycles), parathecal walls (no abortive septa), strong costa and septum medial lines, and transverse septal crosses in Coelastrea .

The present phylogenetic analysis is based on the clade Coelastrea aspera + Coelastrea palauensis . Coelastrea tenuis , if valid, most resembles Coelastrea aspera , differing only in the lack of spongy columellae, and in some corallites, having no columella at all. Its corallites are also more irregular in terms of size and shape (see Vaughan, 1907: 105).

Figures

Figure 8. Coelastrea Verrill, 1866, has discrete corallites with double or fused walls, septa in ≥ four cycles (≥ 48 septa), regular free septa, and well-developed septal (multiaxial) lobes. Septal teeth with medium height (0.3–0.6 mm) and spacing (0.3–1 mm). Walls formed by dominant paratheca and partial septotheca, with strong costal and septal medial lines. A, Coelastrea tenuis Verrill, 1866, type species of Coelastrea; macromorphology, holotype YPM IZ 476, unknown locality. B–F, Coelastrea aspera (Verrill, 1866); micromorphology (scanning electron microscopy; B) and microstructure (transverse thin section; C), syntype USNM 402, Ryukyu Islands, Japan; macromorphology, syntype USNM 403, Ryukyu Islands, Japan (D); micromorphology (E) and microstructure (F), hypotype RMNH 13844, Gulf of Aqaba, Israel. G–I, Coelastrea palauensis (Yabe & Sugiyama, 1936); macromorphology, holotype TIU 56631, Palau (G); micromorphology (H) and microstructure (I), hypotype RMNH 14084, New Caledonia.