Diploastrea

Matthai, 1914, p. 72

Type Species

Orbicella minikoiensis Gardiner, 1904, p. 774, pl. 63, fig. 35 = Astrea heliopora Lamarck, 1816; Original Designation Matthai, 1914, p. 72

Type Specimen: Syntype; NHMUK 1927.5.4.152; Verified; Dry Preserved

Type Locality: Minicoy, Lakshadweep, India (Recent)

Matthai, 1914, p. 72 explicitly states that Diploastrea was established based on Orbicella minikoiensis Gardiner, 1904, p. 774, pl. 63: fig. 35, which therefore is the type species. This species was shown to be the same as Astrea heliopora Lamarck, 1816, p. 265 (Matthai, 1914), commonly mistaken as the type of Diploastrea. The syntype series consists of NHMUK 1927.5.4.152, 1927.5.4.153, 1927.5.12.8.

Classification

• Family: Diploastraeidae Chevalier and Beauvais, 1987, p. 721

Synonyms

• Thegioastraea Michelotti In Sismonda, 1871

Diagnosis

Colonial, with extracalicular budding only. Corallites monomorphic and discrete (1–3 centers); monticules absent. Coenosteum costate, moderate amount (< corallite diameter). Calice width medium (4–15 mm), with medium relief (3–6 mm). Costosepta not confluent. Septa in ≥ 4 cycles (≥ 48 septa; including very short free septa). Free septa present but irregular. Septa spaced 6–11 septa per 5 mm. Costosepta unequal in relative thickness. Columellae trabecular and spongy (> 3 threads), ≥ 1/4 of calice width. Paliform (uniaxial) lobes absent. Epitheca well developed and endotheca low-moderate (tabular). Tooth base at mid-calice elliptical-parallel. Tooth tip at mid-calice regular (pointed). Tooth height medium (0.3–0.6 mm) and tooth spacing medium (0.3–1 mm), with > 6 teeth per septum. Granules scattered on septal face; weak (rounded). Interarea smooth. Walls formed by synapticulotheca and partial septotheca; abortive septa absent. Thickening deposits in concentric rings with extensive stereome. Costa center clusters strong; > 0.6 mm between clusters; medial lines absent. Septum center clusters strong; > 0.5 mm between clusters; medial lines absent. Transverse crosses absent. Columella centers clustered.

Description

'Corallum. Incrusting or massive. Corallites circular not projecting. Walls fused and perforate, hence peritheca almost absent. Calices shallow. Septa in not less than two orders, the first two entocoelic, each consisting of twelve septa, exsert, much thickened towards their outer ends. Columella formed of twisted trabeculæ from septal margins. Calicular dissepiments oblique. Polyps. Close together with narrow edge-zones, no coenosarc. Mesenteries in not less than two cycles, each of twelve couples, usually directly continuous from polyp to polyp, primaries meeting stomodæum; all with filaments. Mesoglæa thick. Tentacles corresponding in number and position with entocoeles and exocoeles. Stomodæum short, laterally compressed with two directive grooves. Multiplication by budding.' (Matthai, 1914: 72)

Comparisons

Diploastrea is easily distinguished from all of Montastraeidae, Merulinidae, Lobophylliidae and Mussidae by its synapticulotheca, presumably an autapomorphy. Examination of the microstructure of clade XIV would enable this hypothesis to be tested. In constrast to the other genera of Faviidae (sensu Veron, 2000), and Merulinidae in general, Diploastrea is differentiated on the basis of septal teeth that have elliptical-parallel bases and regular (pointed) tips, synapticulotheca, thickening deposits showing concentric rings with extensive stereome, costa and septum center clusters that are spaced far apart (> 0.6 mm and > 0.5 mm respectively), and absence of medial lines. Across its range, Diploastrea is easily recognizable and shows very limited variation (Crossland, 1952; Veron et al., 1977; Wijsman-Best, 1980; Wood, 1983; Veron, 1986, 2000).

Remarks

Matthai, 1914: 72 explicitly states that Diploastrea was established based on Orbicella minikoiensis Gardiner, 1904: 774, pl. 63: fig. 35, which therefore is the type species. This species was shown to be the same as Astrea heliopora Lamarck, 1816: 265 (Matthai, 1914), commonly mistaken as the type of Diploastrea (Vaughan, 1918: 142; Vaughan, 1919: 469; Vaughan and Wells, 1943: 137; Wells, 1956: F405; Veron et al., 1977: 153; Veron, 1986: 512; Budd et al., 2012; but see Chevalier, 1975: 60; Chevalier and Beauvais, 1987: 721), but the genus description is clearly based on three specimens collected by Gardiner at Minicoy, Lakshadweep, India (i.e. type locality of Diploastrea). Although Diploastrea is a monotypic genus for living corals, at least 11 fossil species have been assigned to it—e.g. Diploastrea crassolamellata (Duncan, 1863: 413, pl. 13: figs 1a–c) by Coryell and Ohlsen, 1929: 216, pl. 39: fig. 2; D. harrisi Wells, 1932: 248, pl. 30: fig. 9, pl. 37: fig. 6, pl. 38: figs 5, 6; and D. aequalis Budd in Budd, Stemann and Stewart, 1992: 589, fig. 9.6—extending its stratigraphic range to the Lower Cretaceous (Wells, 1956). The phylogenetic placement of D. heliopora as the deepest branching species of clades XV to XXI (Budd et al., 2012) appears consistent with these fossil assignments, but a detailed morphological analysis is necessary. A recent age estimate based on a time-calibrated relaxed molecular clock suggests that the lineage extends only up to ~70 mya (Huang and Roy, 2013), but this needs to be verified with more data given its disparity with fossil collections. Diploastrea heliopora is the only living species to have been assigned to the genus throughout its taxonomic history (Wijsman-Best, 1980), a testament to its phylogenetic uniqueness. Indeed, no other living taxon has been placed in the family Diploastraeidae, as proposed by Chevalier and Beauvais, 1987: 721. This scheme was however not accepted by Veron (2000), whose use of Faviidae from Wells (1956) dominated conventional taxonomy until Budd et al. (2012) recently revived Diploastraeidae to reflect the unequivocal support for D. heliopora as a distinct lineage (clade XV) among living species, either sister to Montastraea cavernosa (Huang et al., 2011; Arrigoni et al. 2012), or to Montastraeidae + Merulinidae + Lobophylliidae + Mussidae (Fukami et al., 2008). Diploastrea is widely distributed on reefs of the Indo-Pacific, and absent eastwards from Hawai'i.

Distribution

• Western Europe; Late Cretaceous
• Southern Europe; Late Cretaceous
• Subsaharan Africa; Late Cretaceous
• South Asia; Late Cretaceous
• North America; Late Cretaceous
• Central America; Late Cretaceous
• West Asia; Late Cretaceous
• Central America; Eocene
• Caribbean; Eocene
• Southeast Asia; Eocene
• Subsaharan Africa, Southeast Asia; Oligocene - Miocene
• Subsaharan Africa; Oligocene
• South Asia; Oligocene
• North America; Oligocene
• Central America; Oligocene
• Caribbean; Oligocene
• South America; Oligocene
• Southeast Asia; Miocene - Pliocene
• Southern Europe; Miocene
• North Africa; Miocene
• South Asia; Miocene
• Melanesia; Miocene
• Caribbean; Miocene
• South America; Miocene
• Southeast Asia; Miocene
• Southeast Asia; Pliocene - Pleistocene
• Melanesia; Pliocene
• Southeast Asia; Pliocene
• Subsaharan Africa; Pleistocene
• South Asia; Pleistocene
• East Asia; Pleistocene
• Australasia; Pleistocene
• Melanesia; Pleistocene
• Southeast Asia; Pleistocene
• Indian Ocean; Recent
• Western Pacific; Recent
• Central Pacific; Recent
• East Asia; Holocene
• Australasia; Holocene
• Melanesia; Holocene
• Micronesia; Holocene
• Polynesia; Holocene
• West Indian Ocean Islands; Holocene

This page has been in preparation since 04-Oct-2009 01:59

This version was contributed by Danwei Huang on 05-Feb-2014 17:56.

Page authors are: Ann Budd Danwei Huang. Please contact the editor if you would like to contribute to the diagnosis of this taxon.

The editor is: Ann Budd