Platygyra, EHRENBERG, 1834: 323

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 : 337-339

GENUS PLATYGYRA EHRENBERG, 1834: 323 ( FIG. 24 )

Synonyms

Astroria Milne Edwards & Haime, 1848a, vol. 27: 493 (type species: Madrepora daedalea Ellis & Solander, 1786: 163 , pl. 46: fig. 1; subsequent designation, Milne Edwards & Haime, 1849a, vol. 11: 297); Caeloria Milne Edwards & Haime, 1848a, vol. 27: 493 (type species: Meandrina daedalea Lamarck, 1816: 246 = Madrepora daedalea Ellis & Solander, 1786: 163 , pl. 46: fig. 1; original designation, Milne Edwards & Haime, 1848a, vol. 27: 493).

Type species

Maeandra (Platygyra) labyrinthica Ehrenberg, 1834: 323 (non Madrepora labyrinthica Ellis & Solander, 1786: 160 , pl. 46: figs 3, 4) = Maeandra (Platygyra) lamellina Ehrenberg, 1834: 323 ; original designation, Ehrenberg, 1834: 323.

Original description

‘Stolonibus in margine stirpis repentibus, in disco nullis.’ ( Ehrenberg, 1834: 323).

Subsequent descriptions

Vaughan, 1901b: 305; Wells, 1936: 124, 125; Vaughan & Wells, 1943: 169; Alloiteau, 1952: 618; Wells, 1956: F402; Nemenzo, 1959: 106; Wijsman-Best, 1972: 45; Chevalier, 1975: 122; Veron et al., 1977: 98; Scheer & Pillai, 1983: 122; Wood, 1983: 151; Veron, 1986: 488; Chevalier & Beauvais, 1987: 716; Sheppard, 1990: 14; Veron, 2000, vol. 3: 176, 177.

Diagnosis

Colonial, with intracalicular budding only. Corallites monomorphic and mostly uniserial, but may also be discrete (one to three centres); monticules absent. Walls fused. Calice width medium (4–15 mm), with medium relief (3–6 mm). Costosepta confluent. Septa in <three cycles (<24 septa). Free septa present but irregular. 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. Paliform (uniaxial) lobes absent. Epitheca well developed and endotheca low−moderate (tabular) ( Fig. 24A, D, G ).

Tooth base at midcalice circular. Tooth tip at midcalice irregular; tip orientation perpendicular to septum. Tooth height low (<0.3 mm) and tooth spacing medium (0.3– 1 mm), with> six teeth per septum. Granules aligned on septal face, perpendicular to septal margin; weak (rounded). Interarea palisade ( Fig. 24B, E, H ).

Walls formed by dominant trabeculotheca and partial septotheca; abortive septa absent. Thickening deposits fibrous. Costa centre clusters weak; <0.3 mm between clusters; medial lines weak. Septum centre clusters weak; <0.3 mm between clusters; medial lines strong. Transverse crosses absent. Columella centres aligned ( Fig. 24C, F, I ).

Species included

1. Platygyra lamellina ( Ehrenberg, 1834: 323) ; syntype: ZMB Cni 682, figured in Matthai (1928, pl. 65: fig. 2) (dry specimen; Fig. 24A ); syntypes: ZMB 669, 683, listed by Matthai (1928: 37, pl. 65: figs 1, 3) as types of Maeandra (Platygyra) labyrinthica var. leptochila and Maeandra (Platygyra) labyrinthica , respectively (not found); type locality: Red Sea; phylogenetic data: molecular and morphology.

2. Platygyra acuta Veron, 2000 , vol. 3: 190, figs 1–4 (see also Veron, 2002: 161, figs 295–297; ICZN, 2011: 165); lectotype (designated herein): MTQ G55845 (dry specimen); type locality: Mahé, Seychelles, 15 m depth; phylogenetic data: molecular and partial morphology.

3. Platygyra carnosa Veron, 2000 , vol. 3: 184, figs 1–3 (see also Veron, 2002: 159, figs 292–294; ICZN, 2011: 165); lectotype (designated herein): MTQ G55795 (dry specimen); type locality: Hong Kong, 5 m depth; phylogenetic data: none, but mitochondrial genome sequenced ( Wang et al., 2013).

4. Platygyra contorta Veron, 1990: 145 , figs 51, 52, 84; holotype: MTQ G32488 (dry specimen); type locality: Puerto Galera , the Philippines, 15 m depth; phylogenetic data: molecular and partial morphology .

5. Platygyra crosslandi ( Matthai, 1928: 48, pl. 47: figs 1a, b, 2, pl. 56: fig. 8a, b); holotype: NHMUK 1928.3 .1.7 (dry specimen); type locality: Red Sea; phylogenetic data: none .

6. Platygyra daedalea ( Ellis & Solander, 1786: 163, pl. 46: fig. 1); holotype: GLAHM 104006 (dry specimen; Fig. 24D ); type locality: ‘Oceano Indiae orientalis’ ( Ellis & Solander, 1786: 163); phylogenetic data: molecular and morphology.

7. Platygyra pini Chevalier, 1975: 155 , pl. 9: figs 3, 6, pl. 12: figs 4–6, pl. 13: fig. 1; holotype: ‘P 135e’ ( Chevalier, 1975: 155), MNHN status unknown; type locality: Baie de Gu, Ile des Pins, New Caledonia, 33 m depth; phylogenetic data: molecular and morphology.

8. Platygyra ryukyuensis ( Yabe & Sugiyama, 1935: 394) (see also Yabe et al., 1936: 38, pl. 28: figs 3–5; holotype: TIU 48237 (dry specimen); type locality: Amami Ōshima, Ryukyu Islands, Japan; phylogenetic data: molecular and partial morphology.

9. Platygyra sinensis ( Milne Edwards & Haime, 1849a, vol. 11: 298); holotype: MNHN IK-2010- 417 (dry specimen; Fig. 24G ); type locality: ‘les mers de la Chine’ ( Milne Edwards & Haime, 1849a, vol. 11: 299); phylogenetic data: molecular and morphology.

10. Platygyra verweyi Wijsman-Best, 1976: 55 , pl. 6: fig. 4; holotype: ZMA Coel. 9053a (dry specimen); paratypes: ZMA Coel. 8833, 9053b, 9054, 9984 (four dry specimens); type locality: Poeloe Dapoer, Thousand Islands, Indonesia; phylogenetic data: molecular only ( Keshavmurthy et al., 2012).

11. Platygyra yaeyamaensis (Eguchi & Shirai in Shirai, 1977: 555); holotype: unknown; type locality: Yaeyama , Ryukyu Islands, Japan; phylogenetic data: none .

Taxonomic remarks

The taxonomic history of Platygyra Ehrenberg, 1834: 323 , is extremely convoluted. It was described as a subgenus of Maeandra Oken, 1815: 68 , with five species, the first of which being Maeandra (Platygyra) labyrinthica Ehrenberg, 1834: 323 , to which he referenced as synonyms Meandrina labyrinthica ( Lamarck, 1816: 246) , Madrepora labyrinthiformis Linnaeus, 1758: 794 , and Madrepora labyrinthica Ellis & Solander, 1786: 160 , pl. 46: figs 3, 4. In order to clarify this, Brüggemann (1879: 571) fixed Madrepora labyrinthica ( Ellis & Solander, 1786: 160) as the type. This is problematic because the specimens described by Linnaeus (1758: 794) and Ellis & Solander (1786: 160) were derived from the Atlantic ( Matthai, 1928: 110).

More recently, Chevalier (1975: 122) and Veron et al. (1977: 98) treated Madrepora daedalea Ellis & Solander, 1786: 163 , pl. 46: fig. 1, as synonymous to Ehrenberg’s definition of the type species. However, examination of one of Ehrenberg’s syntypes of Maeandra (Platygyra) labyrinthica (ZMB Cni 682) strongly suggests that it is equivalent to the second (of five) species that he listed, Maeandra (Platygyra) lamellina Ehrenberg, 1834: 323 . In accordance with Vaughan & Wells (1943: 169), Wells (1956: F402), and Wells (1986: 49), we regard Platygyra lamellina as the type species of Platygyra .

The genus has consistently been recovered as a wellsupported clade in molecular phylogenies ( Fukami et al., 2004 a, 2008; Huang et al., 2009, 2011; Arrigoni et al., 2012). There is a general lack of genetic variation amongst Platygyra spp. ( Miller & Benzie, 1997; Lam & Morton, 2003), and where there is differentiation, morphotypes do not necessarily correspond with genotypes ( Mangubhai et al., 2007), partly caused by large phenotypic variation within species and high morphological overlap amongst species ( Miller, 1992, 1994; Mangubhai et al., 2007). Platygyra ’s closest relative appears to be Leptoria (together as subclade G) but they are genetically distinguishable from each other. Australogyra has not been sampled for molecular phylogenetic work, but based on morphological similarities with Platygyra even at the subcorallite level, they are expected to be closely related.

Platygyra is widely distributed on reefs of the Indo-Pacific, present as far east as the Tuamotu Archipelago in the Southern Hemisphere ( Glynn et al., 2007), but absent eastwards from Hawai’i in the north.

Morphological remarks

Platygyra is supported by a decay index of 1 on the morphology tree, with the synapomorphy of spongy columellae (> three threads; likelihood of 1.0 based on the Mk1 model), distinguishing it from closely related Australogyra (compact; one to three threads) and Leptoria phrygia (lamellar). Leptoria irregularis has spongy columellae however, and so the character state is recovered as a plesiomorphy on the molecular tree, which samples this species. It is not easily confused with Platygyra because of its small (<4 mm width) and shallow (<3 mm depth) calices.

Platygyra and Australogyra share all other characters, although the latter’s ramose growth form makes its colonies easily separable from those of Platygyra . Molecular data would further clarify the validity of Australogyra as a genus.

Figures

Figure 24. Platygyra Ehrenberg, 1834, has uniserial corallites, fused walls, septa in <three cycles (<24 septa), equally thick costosepta, and spongy columellae. Septal teeth are low (<0.3 mm) with medium spacing (0.3–1 mm); weak (rounded) granules aligned on septal face. Walls formed by dominant trabeculotheca and partial septotheca, with strong septal medial lines and aligned columella centres. A–C, Platygyra lamellina (Ehrenberg, 1834) = Maeandra (Platygyra) labyrinthica Ehrenberg, 1834, type species of Platygyra; macromorphology, syntype ZMB Cni 682, Red Sea (A; photo by K. Loch and W. Loch); micromorphology (scanning electron microscopy; B) and microstructure (transverse thin section; C), hypotype USNM 91127, Irian Jaya, Indonesia. D–F, Platygyra daedalea (Ellis & Solander, 1786); macromorphology, holotype GLAHM 104006 (D; photo by K. G. Johnson); micromorphology (E) and microstructure (F), hypotype SUI 122833 (FA1112), Lizard Island, Australia. G–I, Platygyra sinensis (Milne Edwards & Haime, 1849a); macromorphology, holotype MNHN IK-2010- 417, unknown locality (G); micromorphology (H) and microstructure (I), hypotype RMNH 12162, Hope Island, Australia.