Pavona giannii sp. nov.

Figs 2, 3,, 5, 6, 7

Type locality.

Yemen: Shabwa Province, Bir Ali, Hyllanyia Island, 13°59.183'N, 48°19.137'E; depth 5 m; 11 November 2008, F. Benzoni leg.

Type material.

Holotype • 1 colony fragment (10.5 x 5.1 cm, Fig. 2); Original label: “ Bir Ali, Hyllanyia Island, Yemen; 13°59.183'N, 48°19.137'E; 11 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; collection code BA 034; MNHN -IK-2012-14233 ”.

Other material.

Djibouti • 1 colony fragment (Fig. 7 C, part of the colony in situ); Maskali Island; 11°42.38'N, 43°9.24'E; 29 Feb. 2020; F. Benzoni leg.; Dolphin Cruise exped.; KAUST DJ 403 . Yemen • 1 colony fragment (Figs 3 A, H, 5 A, D, F, H – L); Aden, Ras Antouk; 12°45.085'N, 45°1.659'E; 8 Mar. 2009; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB AD 016 • 1 colony fragment (Fig. 6 A, whole colony in situ); Balhaf; 13°58.402'N, 48°11.549'E; 22 Mar. 2014; F. Benzoni leg.; Creocean-Total Balhaf LNG Plant monitoring program exped.; UNIMIB BAL 252 • 1 colony fragment (Fig. 5 B, C, E, G); Balhaf; 13°58.413'N, 48°10.532'E; 24 Mar. 2014; F. Benzoni leg.; Creocean-Total Balhaf LNG Plant monitoring program exped.; UNIMIB BAL 253 • 1 colony fragment; Bir Ali; 13°59.116'N, 48°15.372'E; 16 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 010 • 1 colony fragment; Bir Ali; 13°59.094'N, 48°14.018'E; 16 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 017 • 2 colony fragments (Fig. 3 C); Bir Ali; 13°59.180'N, 48°15.692'E; 19 Nov. 2008; F. Benzoni leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BA 066 • 2 colony fragments (Fig. 6 G, colony in situ); Burum; 14°19.266'N, 48°59.641'E; 18 Mar. 2009; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB BU 049 • 2 colony fragments; Al Mukallah; 14°30.923'N, 49°9.254'E; 17 Mar. 2007; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB MU 085 • 1 colony (Fig. 3 B); Al Mukallah; 14°30.696'N, 49°9.360'E; 18 Mar. 2007; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB MU 128 • 1 colony fragment (Figs 3 D, 6 C, colony in situ); Socotra Island, Hawlaf; 12°40.662'N, 54°4.497'E; 14 Mar. 2010; F. Benzoni and M. Pichon leg.; UNIMIB - Creocean-Total Yemen Coral Biodiversity exped.; UNIMIB SO 078 . Oman • 1 colony fragment (10 x 8 cm); Dhalkut; 16°41.235'N, 53°11.749'E; depth 9.4 m; 4 Dec. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0895; UF 17903 • 2 colony fragments (Fig. 6 B, colony in situ); Mirbat, Eagles Bay; 16°56.377'N, 054°47.799'E; depth 5.4 m; 9 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0096; UF 17957 • 1 colony fragment (Fig. 3 F); Mirbat, Qinqari Bay; 17°0.561'N, 55°1.240'E; depth 6 m; 12 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0226; UF 18088 • 1 colony fragment (Fig. 3 G); Muscat, Jazirat Al Fahl; 23°40.953'N, 58°30.011'E; depth 5.9 m; 1 Feb. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0722; UF 18089 • 1 colony fragment; Mirbat, Marriott Wreck; 16°56.933'N, 054°43.686'E; depth 10.4 m; 7 Jan. 2022; F. Benzoni leg.; Oman Bioblitz exped.; collection code OM 0017; UF 18090 . Mayotte • 3 colony fragments (Figs 3 E, 5 E, part of the colony in situ); Îlot Mtsamboro; 12°38.031'S, 45°1.140'E; 1 Jun. 2010; F. Benzoni leg.; Tara Oceans exped.; UNIMIB MY 069 . Seychelles • 1 colony fragment; Mahé Island, Horse Shoe Reef; 24 Feb. 2019; F. Benzoni and R. Arrigoni leg.; University of Seychelles Outer Islands coral collection facility exped.; UNISEY SY 079 • 1 colony fragment; same data as for preceding; UNISEY SY 080 • 1 colony; Mahé Island, Le Cap; 12 Jan. 1966; B. R. Rosen leg.; NHMUK 1981.3.5.425 • 1 colony; Mahé Island, Baie Ternay; 28 Dec. 1965; B. R. Rosen leg.; NHMUK 1981.3.5.426 • 1 colony (Fig. 4 A, B); Mahé Island, North East Point; 22 Dec. 1965; B. R. Rosen leg.; NHMUK 1981.3.5.427 . Sri Lanka • 1 colony (Fig. 4 C, D); Galle; W. C. Ondaatje leg.; NHMUK 1883.3.24.4 • 1 colony; W. C. Ondaatje leg.; NHMUK 1883.5.23.8 . Malaysia • 1 colony (Fig. 4 E, F); Pulau Songsong, West Coast, Peninsular Malaysia; C. Betterton leg.; NHMUK 1979.9.24.66 .

Description.

Colonial, corallum encrusting with attached margins, growing on the underlying substrate and broadly following its surface relief (Figs 2 – 4, 6, 7); maximum observed thickness 1 cm. Corallum surface smooth and devoid of ridges, crests, monticules or hydnophorae (Figs 2 B – D, 3, 4). Corallites crowded, less than a corallite diameter apart, and thamnasteroid in arrangement (Figs 2 B – D, 3, 4, 5 A – F). Budding intratentacular, locally leading to the formation of variably developed corallites series by repeated incomplete separation of walls after budding. Their outline is variable even within the same colony ranging from elliptical to kidney-shaped (Fig. 3 H), polygonal (Fig. 3 F) or irregular (Figs 2 C, 3 C). Corallites 2.4 mm (± 0.1 SE) in average maximum diameter and 1.7 mm (± 0.1 SE) in average minimum diameter. On average, 23 septa (± 1 SE) occur per corallite (Table 1), the 6 S 1 reaching the columella, their inner margin fusing with it; their average length is 0.9 mm (Table 1). Septa arranged in three orders (Fig. 5 G, K, L), those of the first and second (S 1 and S 2, respectively) sub-equal in thickness and length, all attaining the same height (Fig. 5 J – L). S 2 may reach the columella or remain slightly shorter either with free margin or occasionally fusing with the columella more deeply in the fossa. Third order septa (S 3) are always present, almost complete. S 3 septa are less than ½ of S 1 and S 2 in length (Fig. 5 J, K), never reaching the columella, and are thinner and shorter in height than S 1–2 (Fig. 5 L). Septal sides of S 1 and S 2 ornamented with scattered blunt granules, S 3 sides smooth (Fig. 5 J – L). Synapticulae connecting radial element lateral sides horizontally can be visible in less densely calcified specimens (Fig. 5 B, C, E). S 1 and S 2 upper margins flush, flattened and running parallel to corallum surface giving it an overall even appearance (Figs 2 D, 5 C, F). Where corallite series occur, radial elements run beyond the series shared wall to the adjacent series, perpendicularly to its axis (transparent pink dashed lines in Figs 2 C, 3 A – F, H, 5 A – C, J). Above the shared wall, they are mostly parallel, their upper margin flattened and flush with the corallum surface (Fig. 5 C). Viewed from above, the radial elements running over the adjacent corallite series shared wall resemble frets over a guitar fingerboard (Fig. 5 J), their ladder-like arrangement identical to that usually observed over the ridges forming in other congeners (Veron and Pichon 1980: figs 21, 24). Columella present, solid and made of a single blunt process its tip sitting lower than the upper septal margin (Fig. 5 D – I). Maximum and minimum average columella diameter 0.5 and 0.2 mm, respectively (Table 1). Columella transverse section below the tip shape ranging from circular to elongated and dash-like in outline.

Typically, polyp tentacles are extended in the daytime; therefore, coenosarc, tentacle, oral disc, and mouth coloration is usually visible in situ. Living tissue surrounding the mouth orifice and the oral disc is white (Figs 6 D – G, 7) to light grey (Fig. 2 A). Tentacles commonly white, giving colony surface a bearded appearance (Figs 2 A, 6 A – F, 7). Occasionally, tentacles can also be light green or brown (Fig. 6 A), seldom brown (Fig. 7 C). The coenosarc is typically brown (Figs 2 A, 6 A, C, D, F, G, 7 A, B) to savora mustard yellow (Fig. 6 B, E).

Etymology.

This species is named after Giambattista J. d. C. Benzoni, known as Gianni (1946-2024) for his unconditional support throughout my personal and professional life, and the graceful pride he took in being a coral taxonomist’s father.

Distribution and habitat.

Pavona giannii sp. nov. is a reef-dwelling species known from multiple localities north and south of the equator in the tropical Indian Ocean (Fig. 1). This species can be part of shallow water coral reef communities occurring in well-lit conditions between 1 and 15 m depth. It can encrust blocks of coral rubble, dead coral colonies or limestone, and can also grow on non-carbonate bedrock as observed in the Gulf of Aden and Arabian Sea. There, Pavona giannii sp. nov. seasonally withstands the low temperature and nutrient rich waters brought by the summer Arabian Sea upwelling (Sheppard and Sheppard 1991). These recurrent conditions limit coral reef formation and select the scleractinian taxa able to withstand a pseudo-high latitude effect (Benzoni et al. 2003, 2012).