Scleractinian Coral Family, Meandrinidae

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Family Meandrinidae: (Gk. maiandros, windig; L. ina, like).... a reference to the winding valleys. This is a major family of the Cretaceous, with extant genera being remnants of Tethyan (not Cretaceous/Tertiary) extinctions. The colonies are phaceloid, massive, submassive, columnar or sometimes encrusting. Superficially they resemble faviids (Meandrinidae have fine, non-porous skeletal structures while faviids are nearly opposite). Genera of this family have solid walls; likewise their septa are solid, exsert and evenly spaced. The group in general is common in protected environments. Not much is known about the reproductive behavior in Meandrinidae. However, the majority of zooxanthellae species are gonochoric broadcast-spawners.
The family is made up of seven genera (i.e. Meandrina, Ctenella, Dichocoenia, Dendrogyra, Montigyra, Gyrosmilia, and Eusmilia). The genus Meandrina; Dichocoenia, Eusmilia, and Dendrogyra are entirely Atlantic, while Ctenella and Gyrosmilia are limited to the south-eastern Indian Ocean and the Red Sea. (Veron 2000).	Some members of the family Meandrinidae (80kB)
Key to the family Meandrinidae Colony not phaceloid Colony meandroid Valleys convoluted Colony hemispherical: Genus *Ctenella* Colony columnar: Genus *Dendrogyra* Valleys not convoluted Columella present: Genus *Meandrina* Columellae absent: Genus *Gyrosmilia* Colony not meandroid Colony plocoid: Genus *Dichocoenia* Colony not plocoid: Genus *Montigyra* Colony phaceloid: Genus *Eusmilia*
Indo-Pacific genera: ---------------------------------------------------------------------------------------------------------- Ctenella (Gk. ktenos, comb; L. -ella, relating to the septa): C.chagius, confined to the central Indian Ocean, is the only Indo-Pacific species of Meandrinidae which is otherwise confined to the Caribbean. Even at family level, extant distributions are not reliable indicators of place of origination. It forms massive encrusting or explanate colonies which are brownish in color. Corallites are joined in longitudinal series and the valleys are usually long and sinuous. A mid-line between septa of adjacent corallites is well established. The distance from mid-ridge to mid-ridge is about 1.5cm and the valleys are about 1cm deep. Septa are clearly visible, closely packed, with the larger ones running over the corallite walls without interruption. PRESENT DISTRIBUTION: Central Indian Ocean. GENERAL ABUNDANCE: uncommon, conspicuous. FOSSIL RECORD: None. NUMBER OF EXTANT SPECIES: 1 known species; i.e. C.chagius, from Chagos in the central Indian Ocean, which thus has the most anomalous distribution of all corals. Gyrosmilia (Gk. gyros, round; smilion, knife): G.interrupta forms small rounded coral heads that are attached by a narrow peduncle. Corallites are joined in longitudinal series with long and sinuous valleys. Septa alternate in size and about half are broader than the rest and exsert. Septal margins are small. PRESENT DISTRIBUTION: Western Indian Ocean. GENERAL ABUNDANCE: uncommon. FOSSIL RECORD: none. NUMBER OF EXTANT SPECIES: 1 known species. Montigyra (L. mons, mountain; Gk. gyros, round): This genus is known from a single specimen (M.kenti). Present indications are that it could now be extinct. It is a hemispherical and sub-meandroid corallum with groups of septa fused into monticules. Septa are thin and compact. PRESENT DISTRIBUTION: NW Australia only. GENERAL ABUNDANCE: rare. FOSSIL RECORD: none. NUMBER OF EXTANT SPECIES: 1 known species Atlantic genera: --------------------------------------------------------------------------------------------------------------- Meandrina (Gk. meandros, winding; L. -ina, denoting likeness): Forms rounded or flattened colonies that may be attached to hard substrate or be free-living. Superficially they resemble faviids; Meandrinidae have fine, non-porous skeletal structures while faviids are nearly opposite.Colonies are yellow, pale-brown in color. Colonies are joined in series to form a system of valleys and ridges. Distance from mid-ridge to mid-ridge is about 10-15mm and the valleys may be 10mm deep. Larger septa are widely spaced. Paliform lobes are absent, the columella is plate-like and lies deep in the fossa. There is a distinct line along the top of the walls to which septa joins (is not an ambulacral ridge). PRESENT DISTRIBUTION: Caribbean, Gulf of Mexico and Bermuda. GENERAL ABUNDANCE: generally common, conspicuous. FOSSIL RECORD: Eocene (?) of the Caribbean, Oligocene of the Tethys. NUMBER OF EXTANT SPECIES: 2 known species. Dichocoenia (Gk. dicha, divided into two; koinos, to share): Forms massive colonies that are either rounded or flattened and whitish, yellow, or brown in color. Corallites are separate and have distinct walls; they are mono- to polycentric and correspondingly are either rounded, oval, or elongate with a diameter of 3-4mm. Septa are usually in 2 cycles; their margins are smooth. Perithecal area are non-costate and slightly irregular with low tubercles or granules. Distinct paliform lobes present. PRESENT DISTRIBUTION: Caribbean, Gulf of Mexico and Bermuda. GENERAL ABUNDANCE: sometimes common, conspicuous. FOSSIL RECORD: 'Cretaceous, Eocene of the Caribbean, Miocene of the Tethys. NUMBER OF EXTANT SPECIES: 2 known species. Dendrogyra (Gk. dendron, tree; gyros, round): D.cylindrus is a massive coral that grow in a distinctive columnar or pillarlike forms. The colony may be 2 or 3m high and about the same width across the base. Septa are clearly visible - 6 or 7 large septa/cm w hich are separated by walls. Columella well developed and plate-like lamellar. PRESENT DISTRIBUTION: Caribbean and Gulf of Mexico. GENERAL ABUNDANCE: uncommon, very conspicuous. FOSSIL RECORD: Miocene of the Tethys. NUMBER OF EXTANT SPECIES: 1 known species. Eusmilia (Gk. eu-, true; smilion, knife; -leios, smooth); previously grouped under Caryophylliidae; E.fastigiata forms rounded colonies of prominent well-spaced corallites that are long-stalked and rises from a common base (phaceloid growth). Septa are prominent, leafy, numerous, and in cycles. Costae are visible on the outside walls and are slightly rough to the touch. Smaller septa are not exsert but larger ones are leafy and protrude by about 5mm. They continue down the outside and have crenulated or minutely dentate margins. A small columella is present. PRESENT DISTRIBUTION: Caribbean and Gulf of Mexico. GENERAL ABUNDANCE: Sometimes common, very conspicuous. FOSSIL RECORD: Oligocene (?) of the Tethys, Miocene of the Caribbean. NUMBER OF EXTANT SPECIES: 1 known species.