Isophyllia, MILNE EDWARDS & HAIME, 1851

Budd, Ann F., Fukami, Hironobu, Smith, Nathan D. & Knowlton, Nancy, 2012, Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia), Zoological Journal of the Linnean Society 166 (3), pp. 465-529 : 499-505

GENUS ISOPHYLLIA MILNE EDWARDS & HAIME, 1851 A: 87 ( FIGS 9C, D, 13A–F, 19A–F, 23A–F)

Synonyms: Isophyllastrea Matthai, 1928: 262 [type species: Astraea rigida Dana, 1846: 237 ; pl. 12, fig. 8a–d (by original designation).]

Type species: Oulophyllia ? spinosa Milne Edwards & Haime, 1849: 269, holotype = MNHN-Scle866 ( Fig. 9C, D) [= Madrepora sinuosa Ellis & Solander, 1786: 160 ]; by original designation.

Type species locality: ‘Patrie inconnue’ ( Milne Edwards & Haime, 1849: 269) [Recent].

Early descriptions:

1. ‘Polypier massif; multiplication par fissiparité; polypiérites à centres distincts, restant confondus en séries courtes qui sont soudées entre elles latéralement; cloisons fortement dentées, et dont les dents sont subégales; columelle rudimentaire; endothèque très-abondante; épithèque distincte.’ ( Milne Edwards & Haime, 1851a: 87).

2. Original description, Isophyllastrea : ‘Corallum. Massive. Corallites mostly with mono- and di-stomodaeal polyps, those with monostomodaeal ones 10–12 mm in diameter. Colline somewhat thick, faintly grooved above or ridged. Septa thickening towards wall, comparatively narrow, slightly sloping or almost vertical. Septal margins with teeth more or less resembling those in Isophyllia , sides of septa rough or spinulose. Septa meeting in groove on colline or continuous over ridged colline, exsert ends toothed. Columella feebly developed, consisting of loosely interlocking septal trabeculae.’ ( Matthai, 1928: 262).

Subsequent morphological descriptions ( Matthai, 1928 and later): Matthai (1928: 235–248, 262–268); Vaughan & Wells (1943: 192–193, 195–196); Wells (1956: F418, F419); Walton Smith (1971: 92–94);

Zlatarski & Estalella (1982: 177–182); Veron (2000: vol. 3: 36–37).

Diagnosis: Macromorphology: colonial. Intracalicular budding; initially circumoral. Meandroid (uniserial), usually short series (<five centres per series); medium calices (2.5–5 cm) with high relief (> 6 mm); three or more septal cycles, equal; thin, costate coenosteum; costae not confluent; weak continuous columella with trabecular linkage; reduced epitheca; no septal or paliform lobes; abundant endotheca ( Figs 9C, D, 13A–F).

Microstructure: parathecal wall with trabeculothecal elements. Well-developed clusters of calcification centres encircled by concentric rings of fibrous thickening deposits; clusters cross medial lines; reduced thickening deposits ( Fig. 23A–F).

Micromorphology: high (> 0.6 mm), widely spaced (1–2 mm), spine-shaped, pointed teeth, regularly arranged; layered (banded) interarea of septal teeth; teeth in major and minor septal cycles similar in size; compact columella, with columellar teeth differing in size and shape from septal teeth; spiky, aligned granules ( Fig. 19A–F).

Included species: Isophyllia sinuosa ( Ellis & Solander, 1786: 160) [holotype is from ‘Oceano Indie occidentalis’, and is lost; neotype (herein designated) = SUI102759 ( FA1134 ), Fig. 13A, B, Key Largo , Florida] .

Isophyllia multiflora ( Verrill, 1901: 125) [holotype = YPM4009 , Fig. 13C, D, Bermuda] .

Isophyllastrea rigida ( Dana, 1846: 237, pl. 12, fig. 8a–d) [holotype = YPM4297 , Fig. 13E, F, West Indies ] .

Remarks: Milne Edwards & Haime (1849) originally designated Oulophyllia ? spinosa as the type species of Isophyllia based on a specimen in their collection (MNHN-Scle866). As indicated in Matthai (1928: 237), this species has subsequently been synonymized with Isophyllia sinuosa (Ellis & Solander) , the type specimen of which is lost. A neotype (SUI102759, collected in Key Largo, Florida) has been therefore designated for Isophyllia sinuosa .

In the classification system of Vaughan & Wells (1943) and Wells (1956), the genus Isophyllia is distinguished by having a meandroid colony form, and centres with trabecular linkage; colonies form initially by circumoral budding ( Vaughan & Wells, 1943: 192). These authors point out that Isophyllia differs from Symphyllia (its superficially similar Indo-Pacific counterpart), in that Symphyllia has longer series and ·

centres with lamellar linkage. Our observations show Isophyllia differs from Mycetophyllia , in that Mycetophyllia lacks coenosteum and has confluent costosepta, centres with lamellar linkage, and paliform lobes. Isophyllia differs from Indo-Pacific Symphyllia in Isophyllia ’s possession of an epitheca, the shape of their septal teeth and granules, and the fact that teeth in major and minor septal cycles in Symphyllia differ in size and shape.

In the classification system of Vaughan & Wells (1943) and Wells (1956), the monotypic genus Isophyllastrea is similar to Isophyllia in having similarly shaped, large teeth (regular, pointed with circular bases); colonies that form initially by circumoral budding; and short series with trabecular linkage. It is distinguished by having a cerioid colony form and feeble columella ( Vaughan & Wells, 1943: 193, 195– 196). However, our observations show that Isophylllastrea is not truly cerioid because it has coenosteum, like Isophyllia , and columellae in the two taxa are equally developed ( Fig. 23A, B, D, E). Moreover, molecular data (cyt b and COI) show that Isophyllia sinuosa and Isophyllastrea rigida are identical (H. Fukami, unpubl. data). Nevertheless Isophyllastrea rigida is distinguished from Isophyllia sinuosa on the basis of microstructure (well-developed concentric rings associated with septal teeth, Fig. 23D–F), and micromorphology (smooth interarea of teeth, Fig. 19D–F). We feel that the similarities outweigh the differences, and synonymize the genus Isophyllastrea with Isophyllia , as in Zlatarski & Estalella (1982) and Veron (2000) but not Walton Smith (1971) and not Cairns, Hoeksema & Land (1999). We consider the two species to be distinct.

Following Matthai (1928), Walton Smith (1971) recognized three species of Isophyllia + Isophyllastrea ( Isophyllia sinuosa , Isophyllia multiflora , Isophyllastrea rigida ); whereas Zlatarski & Estalella (1982) recognized only one species ( Isophyllia sinuosa ), and Cairns, Hoeksema & Land (1999) recognized two species ( Isophyllia sinuosa , Isophyllastrea rigida ). Veron (2000) recognized Isophyllia sinuosa and Isophyllastrea rigida . The three possible species of Isophyllia recognized herein ( I. sinuosa , I. multiflora , I. rigida ) are distinguished on the basis of number of centres per series, calice width, and number of septa per cm ( Fig. 13). Isophyllia sinuosa and I. multiflora form series (valleys with two or more centres), whereas I. rigida is usually monocentric. Valley widths in I. sinuosa average 20–25 mm, in I. multiflora 12–15 mm, and in I. rigida 10–12 mm. Number of septa per cm range from seven to nine in I. sinuosa , and 11–12 in I. multiflora . I. rigida has 25–30 septa per corallite (more than three septal cycles).