Leptoria, MILNE EDWARDS & HAIME, 1848

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 : 322-324

GENUS LEPTORIA MILNE EDWARDS & HAIME, 1848 A: 493 ( FIG. 16 )

Type species

Meandrina phrygia Lamarck, 1816: 248 = Madrepora phrygia Ellis & Solander, 1786: 162 , pl. 48: fig. 2; original designation, Milne Edwards & Haime, 1848a, vol. 27: 493; holotype: MNHN IK-2012-14001 (dry specimen; Fig. 16A ); type locality: ‘l’Océan des Grandes- Indes et la mer Pacifique’ ( Lamarck, 1816: 248).

Original description

‘Diffère des genres précédents [ Meandrina , Manicina , Diploria ] par sa columelle lamellaire. Les collines sont simples, minces ou vésiculeuses.’ ( Milne Edwards & Haime, 1848a, vol. 27: 493).

Subsequent descriptions

Milne Edwards & Haime, 1849a, vol. 11: 291; Milne Edwards & Haime, 1857, vol. 2: 405, 406; Klunzinger, 1879: 13; Duncan, 1884: 90; Gardiner, 1899: 739; Delage & Hérouard, 1901: 626; Gardiner, 1904: 764; Vaughan, 1918: 117; Vaughan, 1919: 421; Hoffmeister, 1925: 27; Faustino, 1927: 141; Matthai, 1928: 109, 110 (non Platygyra Ehrenberg ); Coryell & Ohlsen, 1929: 205; Yabe et al., 1936: 38 (non Platygyra Ehrenberg ); Vaughan & Wells, 1943: 169; Alloiteau, 1952: 617, 618; Crossland, 1952: 150; Wells, 1956: F402; Nemenzo, 1971: 166; Wijsman-Best, 1972: 50; Chevalier, 1975: 109; Veron et al., 1977: 114, 115; Scheer & Pillai, 1983: 126; Wood, 1983: 154; Veron, 1986: 496; Chevalier & Beauvais, 1987: 717; Sheppard, 1990: 14; Bosellini, 1999: 222; Veron, 2000, vol. 3: 202.

Diagnosis (apomorphies in italics)

Colonial, with intracalicular budding only. Corallites monomorphic and uniserial; monticules absent. Walls fused. Calice width small (<4 mm), with low relief (<3 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 lamellar or spongy trabecular (> 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. 16A, D ).

Tooth base at midcalice circular. Tooth tip at midcalice irregular; tip orientation perpendicular to septum. Tooth height low (<0.3 mm) and tooth spacing narrow (<0.3 mm), with> six teeth per septum. Granules aligned on septal face, perpendicular to septal margin; weak (rounded). Interarea palisade ( Fig. 16B, E ).

Walls formed by dominant trabeculotheca and partial septotheca; abortive septa absent. Thickening depos- its 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. 16C, F ).

Species included

1. Leptoria phrygia ( Ellis & Solander, 1786: 162, pl. 48: fig. 2); holotype: GLAHM 104018 (dry specimen); type locality: ‘Oceano pacifico’ ( Ellis & Solander, 1786: 162); phylogenetic data: molecular and morphology.

2. Leptoria irregularis Veron, 1990: 147 , figs 53, 54, 95; holotype: MTQ G32489 (dry specimen; Fig. 16D ); type locality: north side of Kayama Island , Sekisei Lagoon, Ryukyu Islands, Japan, 15 m depth; phylogenetic data: molecular and partial morphology .

Taxonomic remarks

Leptoria was established by Milne Edwards & Haime (1848a, vol. 27: 493) as a genus with lamellar columellae, and Meandrina phrygia Lamarck, 1816: 248 , as the type. Two other living taxa, Meandrina gracilis Dana, 1846: 261 , and Meandrina tenuis Dana, 1846: 262 , were also included ( Milne Edwards & Haime, 1857, vol. 2: 407) but later synonymized with the type species ( Matthai, 1928: 112; Chevalier, 1975: 110; Veron et al., 1977: 115). All specimens used to describe them correspond to the original description in the possession of lamellar columellae.

The addition of Leptoria irregularis Veron, 1990: 147 , necessitates the broadening of this description. Molecular phylogenies have placed this species at two distinct positions, sister to Scapophyllia cylindrica ( Fukami et al., 2008) or Leptoria phrygia ( Huang et al., 2011) . Material for the former were collected from Okinawa, Japan, just 400 km north of the type locality, whereas the latter sample came from the Philippines. We have not been able to examine either of these types in detail, but assume the latter to be positively identified in order to preserve the taxonomic status quo. Nevertheless, the presence of ‘irregularly fused trabeculae’ ( Veron, 1990: 148) suggests that lamellar columellae are only present in Leptoria phrygia and not the entire genus. Our character analysis shows that this trait is an autapomorphy.

Leptoria has been considered a synonym of Platygyra by several authors ( Matthai, 1928: 110; Wells, 1936: 124; Ma, 1937: 97) because by elimination, the first three of five species listed by Ehrenberg (1834: 323) were deemed unsuitable as they were thought to refer to the Atlantic species Madrepora labyrinthiformis Linnaeus, 1758 ( Matthai, 1928: 110) . Platygyra phrygia ( Lamarck, 1816: 248) , fourth on the list, was therefore regarded as the type of Platygyra , with Leptoria becoming a synonym. This interpretation was short lived, as Vaughan & Wells (1943: 169) redesignated the first species on Ehrenberg’s list, Maeandra (Platygyra) labyrinthica from the Red Sea, as type species of Platygyra (see also Vaughan, 1901a: 50), and also resurrected Leptoria immediately after (see remarks for Platygyra below).

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

Morphological remarks

Leptoria is sister taxon to the clade comprising Australogyra and Platygyra , with small calice diameter (<4 mm; likelihood of 1.0 based on the Mk1 model) and low relief (<3 mm; likelihood 1.0) as synapomorphies. Along with the narrower spacing between teeth (<0.3 mm; likelihood 1.0) in Leptoria , only these size-related features distinguish the genus from its closest relatives, subcorallite characters included.

Leptoria phrygia is the only species in Merulinidae to possess lamellar columellae, but this is lacking in its conspecific Leptoria irregularis , which may account for its association with the phylogenetically distant Merulina ampliata and Scapophyllia cylindrica ( Veron, 2000, vol. 3: 202). However, subcorallite characters may separate them on the basis of Leptoria ’s weak granule alignment and trabeculothecal walls without abortive septa. Only macromorphology has been characterized for Leptoria irregularis ; detailed investigation on this species will clarify its status.

Figures

Figure 16. Leptoria Milne Edwards & Haime, 1848a, has uniserial corallites, fused walls, small (<4 mm) and low-relief (<3 mm) calices, septa in <three cycles (<24 septa), and lamellar or spongy columellae. Septal teeth are low (<0.3 mm) and narrowly spaced (<0.3 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, Leptoria phrygia (Ellis & Solander, 1786), type species of Leptoria; macromorphology, Meandrina phrygia Lamarck, 1816, holotype of Leptoria MNHN IK-2012–14001, unknown locality (A); micromorphology (scanning electron microscopy; B) and microstructure (transverse thin section; C), hypotype USNM 38508, Murray Island, Australia. D, Leptoria irregularis Veron, 1990; macromorphology, holotype MTQ G32489, Ryukyu Islands, Japan. E, F, Leptoria phrygia (Ellis & Solander, 1786); micromorphology, hypotype USNM 89850, Mangata, Cook Island (E); microstructure, hypotype USNM 83200, Marshall Islands (F).