unclassified Scleractinia

South Pacific Ocean, Duration 10 seconds

Plerogyra sinuosa is not the primary subject of the video clip; the primary subject is Periclimenes tosaensis (Jelly cleaner shrimp). Coral Sea, Duration 22 seconds

In captivity

Figure 1.Colonies of Pachyseris rugosa (a–c) and Pachyseris speciosa (d–g) in situ. a Image of the whole colony of specimen IRD HS2893, Prony Bay, New Caledonia b Lateral view of the fronds of specimen IRD HS2594, Prony Bay, New Caledonia c Fronds of specimen IRD HS2856 viewed from above, Prony Bay, New Caledonia d Tiers of foliose projections of a colony from New Caledonia e Image of specimen UNIMIB SO040, Socotra Island f Part of specimen KAUST SA714, Saudi Arabia g Detail of a colony with reduced carinae and brightly colored polyp mouths, growing in very turbid environment, Banc des Japonais, New Caledonia.

South Pacific Ocean, Duration 10 seconds

In captivity

Figure 2.Pachyseris rugosa. a Lateral view of colony IRD HS1442 b Lateral view of colony IRD HS152 showing very irregular fronds and carinae c Detail of the fronds of specimen IRD HS152 d Specimen IRD HS221, white arrow points at a dash-like columella e SEM image of IRD HS2594, white arrows point at the fused dissepiments connecting the inner end of the radial elements and the reduced columellae f SEM image of ornamentation on radial elements showing single granules (sg), clumped granules (cg) and menianae (me).

Coral Sea, Duration 15 seconds

Figure 1.Colonies of Pachyseris rugosa (a–c) and Pachyseris speciosa (d–g) in situ. a Image of the whole colony of specimen IRD HS2893, Prony Bay, New Caledonia b Lateral view of the fronds of specimen IRD HS2594, Prony Bay, New Caledonia c Fronds of specimen IRD HS2856 viewed from above, Prony Bay, New Caledonia d Tiers of foliose projections of a colony from New Caledonia e Image of specimen UNIMIB SO040, Socotra Island f Part of specimen KAUST SA714, Saudi Arabia g Detail of a colony with reduced carinae and brightly colored polyp mouths, growing in very turbid environment, Banc des Japonais, New Caledonia.

Figure 3.Pachyseris speciosa. a The holotype USNM 119, West Indies b Specimen UNIMIB SO020, Socotra Island c Detail of the holotype showing parallel carinae and alternating radial elements d Detail of the specimen in b e SEM image of IRD HS2673, white arrows point at one of the spatula-shaped processes extending from the inner end of the radial elements and forming the columella f SEM image of the same specimen (Figure 3e) in a portion where columella processes are fused to form a continuous structure (white arrow) g SEM image of IRD HS2263 showing the ornamentation of the radial elements consisting of vertically fused granules (vfg) seen from above and the zigzag pattern of the radial element margin (dashed line) h SEM image of IRD HS2673 showing the radial element zigzag pattern (dashed line) and face ornamentation consisting of clumped granules (cg), vertically fused granules (vfg), and menianae (me).

Figure 11.In situ and corallum images of a and d Pachyseris speciosa b and e Pachyseris inattesa sp. n., c and f Leptoseris mycetoseroides in the Red Sea.

Figure 2.Pachyseris rugosa. a Lateral view of colony IRD HS1442 b Lateral view of colony IRD HS152 showing very irregular fronds and carinae c Detail of the fronds of specimen IRD HS152 d Specimen IRD HS221, white arrow points at a dash-like columella e SEM image of IRD HS2594, white arrows point at the fused dissepiments connecting the inner end of the radial elements and the reduced columellae f SEM image of ornamentation on radial elements showing single granules (sg), clumped granules (cg) and menianae (me).

Figure 4.Pachyseris inattesa sp. n. in situ. a KAUST SA1300 b KAUST SA426 c KAUST SA887 d holotype RMNH Coel. 41613 e KAUST SA1284 f KAUST SA004 g KAUST SA1301 h KAUST SA1305.

Figure 5.Development of carinae and series of calices in Pachyseris inattesa sp. n. in situ. a Well-developed carinae and elongated series of calices in specimen KAUST SA429 b Well-developed carinae and short series of calices in specimen KAUST SA887 c Poorly developed carinae and short series of calices in specimen KAUST SA1284 d Poorly developed carinae and long series of calices in specimen KAUST SA1293.

Figure 6.Pachyseris inattesa sp. n. a KAUST SA426 b Holotype RMNH Coel. 41613 c View of the marginal part of the holotype in b d View of the central part of the holotype in b e KAUST SA678 f KAUST SA1301 g KAUST SA429.

Figure 7.SEM images of Pachyseris inattesa sp. n. showing micro-morphological details. a Adjacent calices in series in specimen KAUST SA492 b Single calice in the same specimen as in a, the white arrow points at the single columellar process, which extends from the inner end of the radial elements reaching the fossa c Another calice in the same specimen (Figure 7a) with multiple columella processes (white arrows) extending from the inner end of the radial elements d A calice of specimen KAUST SA1305, the white arrows point at the finely ornamented columellar processes extending into the fossa from the inner end of the radial elements e Parallel and equal radial elements across a carina (top of the carina indicated by the dashed transparent white line) presenting the typical zigzag pattern of the margin (dashed grey line) f Detail of radial elements as in Figure 7e, showing the upper margin zigzag pattern (dashed grey line) and face ornamentation consisting of clumped granules (cg).

Figure 10.SEM images of Pachyseris inattesa sp. n. (a, c, e) and Leptoseris foliosa (b, d, f) a and b similar arrangement of adjacent calices in specimen KAUST SA1305 and IRD HS2854, respectively c and d calices the same specimens as in a and b, respectively e and f lateral ornamentation of the radial elements (light blue arrows) and pattern of their upper margin in specimens (yellow dashed lines) as in a and b, respectively.

Figure 11.In situ and corallum images of a and d Pachyseris speciosa b and e Pachyseris inattesa sp. n., c and f Leptoseris mycetoseroides in the Red Sea.

Figure 8.Map of the Red Sea showing the sampling sites where Pachyseris inattesa sp. n. was collected, including the type locality. Circled regions indicate approximate distribution of the Farasan Banks (a complex reef network spanning about ~250km of the Saudi Arabian coast) and the Farasan Islands (a system of > 80 islands spanning about 150km of the southernmost Saudi Arabian coast adjacent to the Yemeni border).