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Family Siderastreidae: (L. sideris, star; Gk. aster, star)....relating to the regular star-like arrangement of the calices and septa.
A formerly diverse family in the Caribbean, the Siderastreidae are now represented there only by two species of Siderastrea. Psammocora and Coscmaraca have clear affinities, with Psammocora vaughani being intermediate between them. The other genera within the family are paucispecific, with uncertain relationships.

Colonies are colonial, massive, or laminar. Corallites are small, immersed and with numerous thickened septo-costae. The septa are usually fused at the inner margins to form a fan-like group, have granulated upper margins and are closely compacted and equally spaced. The corallite walls are very poorly defined. The family consists of six extant genera that are distantly related and have a worldwide distribution; i.e. Pseudosiderastrea, Horastrea (Madagaskar only), Anomastraea (western Indian Ocean), Siderastrea, Psammocora, and Coscinaraea.
The genera Horastrea and Anomastraea are restricted to the western Indian Ocean and the Red Sea, while Siderastrea is predominant in the Atlantic. The remaining genera Pseudosiderastrea, Psammocora and Coscinaraea are only found in waters of the Indo-Pacific.


Some members of the family Siderastreidae

All genera found within the Indo-PAcif region are easily found around PNG (for morphological characteristics see table). Coscinarea columna is a gonochronic species. It appears that Siderastrea are mostly gonochoric exhibiting either a brooding or spawning mode of reproduction. Members of the genus Horastrea and Anomastarea show intratentacular budding.

Key to the family Siderastreidae Corallite walls well defined Colony plocoid: Genus Horastrea
Colony not plocoid Colony cerioid Septal teeth saw-like: Genus Pseudosiderastrea
Septal teeth not saw-like: Genus Siderastrea
Colony not cerioid: Genus Anomastraea
Corallite walls not well defined Corallites < 3 mm diameter: Genus Psammocora
Corallites > 3 mm diameter: Genus Coscinaraea
Indo-Pacific genera: ----------------------------------------------------------------------------------------------------------

Pseudosiderastrea (Gk. pseudo, false; sideris, star; aster, star):

P.tayami is an encrusting to massive colony that are 10-15cm in diameter. Its color is pale brown, gray, or pink. The corallite walls are pale or white, crowded with shared walls, and polygonal (ceroid) in shape. The corallites are 2-4mm in diameter. The fossa is shallow. Septa are closely packed and visible as fine lines running between adjacent calices. Septa are numerous and in cycles (30 septa in a 3mm calice or 50 in a larger one). Septa are slightly exsert, dentate, or granulated with no synapticulae joints present. A tiny columella is present (consisting of 1-4 pinnules).
PRESENT DISTRIBUTION: Western Indian Ocean to western Pacific.
GENERAL ABUNDANCE: Uncommon, cryptic.
FOSSIL RECORD: Pliocene of the Pacific.
NUMBER OF EXTANT SPECIES: 1 known species.
Psammocora (Gk. psammos, sand; kora, pupil of the eye): In general, the species of Psammocora are distinct. They may show substantial environment-correlated variation, the same variation being repeated in most geographic regions. Except for some colonies of P.nierstraszi, coralla from western and eastern Australia are indistinguishable. P.superficialis shows no geographic variation throughout the entire Indo-Pacific.
Branching, encrusting, leafy, or massive colonies that are green, brown or wine-colored. The surface of the coral is smooth or granular and a few mm high. Calices are closely packed and superficial, measuring about 1-2mm in diameter, that they are hard to spot. Septa are numerous and visible which may end in a wide, blunt monticule (thamnasterioid structure), giving a flower-like appearance (petaloid septa rather than terming them septo-costae). Septa may be broken into rows of minute tubercles. Columella usually small and pinnacle-like. Corallite wall is absent or weak (no crown-like appearance as often seen in Coscinarea). Genus is frequently found on reef flats and often houses endolithic activity (Lithophaga, and Cirripeda).
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean to far eastern Pacific.
GENERAL ABUNDANCE: generally common, sometimes cryptic.
FOSSIL RECORD: Miocene of the Caribbean.
NUMBER OF EXTANT SPECIES: 12 known species.
Coscinaraea (Gk. koskinos, sieve; araios, thin, porous): Two morphologically similar species (C.mcncilli and C.marshae) are endemic to extra-tropical southern Australia. The remainder have tropical distributions. Two other species (C.exesa and C.columna), also morphologically similar, a re common and widely distributed and account for most records of the genus.
Colonies form massive, encrusting, plate-like extensions and seldom exceed 30cm in diameter. They are brown or green in color and rough in surface structure. Calices are crowded, have a shared rounded wall and are 2-7mm in diameter; in some species, adjacent corallites often are crowned with a double-row of pinules. Septa are visible, granulated (fine-toothed), and run over the exsert corallite walls or collines into adjacent calices. There are 20-30 septa in a calice of 3mm diameter. Septa are minutely dentate while the columella is papillose. Species are often confused with those of Psammocora.
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean to southern Pacific.
GENERAL ABUNDANCE: generally common, conspicuous.
FOSSIL RECORD: Eocene (?) of the Caribbean.
NUMBER OF EXTANT SPECIES: 9 known species.
Indian Ocean genera: ---------------------------------------------------------------------------------------------------------

Horastrea (Malagasy word hora, coral; Gk. aster, star):

H.indica as its only representative, is a massive to hemispherel colony that are small in size. Polyps are pale-brown with a pale, gray-blue, oral disk. Corallites are separate and distinct and raised several mm above the coral surface (phacelo-meandroid). Corallites are rounded or regular and are 8-10mm in diameter. Valleys may reach 4cm in length. Septa are numerous (as many as 80 arranged in 5 cycles) clearly visible and closely packed. Septa may be perforated with compound teeth. Columella is distinct and papillose in appearance.
PRESENT DISTRIBUTION: Western Indian Ocean only.
GENERAL ABUNDANCE: generally uncommon.
NUMBER OF EXTANT SPECIES: 1 known species.
Anomastraea (Gk. anomos, irregular, unequal; aster, star): A.irregularis forms encrusting or massive colonies that are less than 10cm in diameter. Calices are crowded with shared walls and hexagonal, circular, elongated or irregular in shape. Calices between 2-4mm in diameter with a shallow fossa. Septa are visible as fine lines that radiate from the calice center over the walls. Septa are numerous, reach the columella, and fuse with their longer neighbors. There are 25-30 septa in a 3mm thick calice; septa are slightly exsert with their margins dentated.
PRESENT DISTRIBUTION: Western Indian Ocean only.
GENERAL ABUNDANCE: uncommon, cryptic.
NUMBER OF EXTANT SPECIES: 1 known species.
Circum-tropical genus: -------------------------------------------------------------------------------------------------------

Siderastrea (Gk. sideris, star; aster, star):

Recorded in the western Pacific (Philippines) from only a single specimen. It was also found in the Gulf of Panama where it may be an relict endemic. S.radians has been recorded from both the Atlantic and Indian Ocean. If identification of Indian Ocean occurrences is correct, it is the only species occurring in both the Indo-Pacific and the Atlantic.
Forms massive, rounded, or encrusting colonies that are brown, green, or red in color with monocentric ceroid corallite arrangement. Calices are crowded, regular, and have shared walls. They are rounded and deep with a diameter of 2-4mm. Septa are clearly visible as fine lines, immersed and evenly thick at the perimeter where also synapticular jointd are visible. The homogenous septa are numerous and in cycles (S.radians <48; S.siderea >48 septa; S.savignyana 30-35 septa). A columella is not present or rudimentary with few pinules.
PRESENT DISTRIBUTION: Red Sea and western Indian Ocean to Philippines; far eastern Pacific; western to eastern Atlantic.
GENERAL ABUNDANCE: uncommon in the Indian Ocean, often common in the Caribbean.
FOSSIL RECORD: Cretaceous of Tethys; Eocene of the Caribbean.
NUMBER OF EXTANT SPECIES: 5 known species.