Acropora vaughani, WELLS, 1954

Santodomingo, Nadiezhda, Wallace, Carden C. & Johnson, Kenneth G., 2015, Fossils reveal a high diversity of the staghorn coral genera Acropora and Isopora (Scleractinia: Acroporidae) in the Neogene of Indonesia, Zoological Journal of the Linnean Society 175 (4), pp. 677-763 : 730-731

ACROPORA VAUGHANI WELLS, 1954

FIGURE 26

Acropora vaughani Wells, 1954b: 416 , pl. 105 fig. 1, pl. 106 figs 1–8, pl. 107 figs 2–6.

Diagnosis

Colonies arborescent with indeterminate growth, composed of irregular, slender branches. Branch structure 50:50 axial/radial. Radial corallites, tubular to subimmersed, irregularly distributed, and thickened walls. Coenosteum composed of short elaborated spinules that can become costate on corallite walls ( Wallace & Wolstenholme, 1998; Wallace, 1999).

Material studied

Java: RGM 3998 , 1 specimen ; Sumatra: RGM 125829 , 3 specimens ; Timor: RGM 167823 , 1 specimen .

Modern comparative material: Holotype, USNM 44452 , Bikini Atoll, Marshall Islands; RMNH 20979 , SW Salayer,

reef edge, SW Pulau Bahuluang, Indonesia; MTQ G48344, Nain Island, North Sulawesi, Indonesia.

Skeletal characteristics

Corallum . Branches straight or slightly bent, round in transverse section, length 24.29–34.02– 40.22 mm, mid branch diameter 6.48–7.78– 9.97 mm; a single fragment of a branch tip, diameter 4.5 mm; only one branch with scar of a broken branch, angle 75.51° ( Fig. 26D ); growth probably indeterminate.

Corallites. Axial corallite visible in cross section and one branch tip, 1.04 mm exsert, outer diameter 1.42– 1.95– 2.47 mm, inner diameter 0.81 mm, wall thickness 0.34 mm, primary septa up to two-thirds R, secondary septa up to one-quarter R; radial corallites ( Fig. 26 B-C) evenly sized, irregularly distributed, mostly tubular to subimmersed, not touching, round calices, profile length 0.45–0.77– 1.27 mm, angle 29.21–64.39– 89.28°, outer diameter 1.18–1.60– 1.95 mm, inner diameter 0.65–0.74– 0.89 mm, wall thickness 0.29–0.40– 0.55 mm, distance between centres 1.85–2.62– 3.57 mm, primary septa up to one-third R, secondary septa up to one-quarter R. Corallite arrangement sequence 1–4–?–6–8–up to 10.

Coenosteum. Elaborated spinules throughout that can be aligned on some corallite walls, coenosteum amount 0.44–1.02– 2.75 mm ( Fig. 26C ).

Occurrence

Pliocene to Recent. The earliest occurrence is from Fatu Lulih, Timor Leste, of Pliocene age, 1.806 –5.332 Ma. Other specimens are from the Pleistocene localities Sonde in Java and Nalawo Valley in Sumatra of Calabrian to Gelasian age, 0.781 –2.588 Ma. The previously known fossil record includes specimens of Pliocene and Pleistocene age from Niue in the Pacific Ocean ( Wallace, 1999). In modern reefs this species occurs in the entire Indo-Pacific and Red Sea, although is less abundant and does not form monospecific stands ( Wallace, 1999); recent records from Indonesia include a wide distribution in Java, Sulawesi, Nusa Tenggara, Banda Sea, Halmahera and Irian Jaya ( Table 4).

Palaeoenvironment

This species has a few specimens in the fossil record and as part of heterogeneous faunas, e.g. with azooxanthellate corals in Sonde ( Gerth, 1921) and a diverse reefal fauna from Nias ( Gerth, 1925). Interpretations of a palaeoenvironment would be a matter of speculation. In modern reefs, this species is restrict- ed to protected subtidal habitats such as lagoons, sandy slopes or turbid waters around fringing reefs ( Wallace, 1999; Veron, 2000).

Remarks

The fossil specimen RGM 3998 was previously identified as Acropora trinilsecunda ( Felix, 1913) in the col- lections of the Naturalis museum. This particular specimen has not been reported in the literature. As explained in the discussion of A. borneoensis , the type material of Felix’s species was not located despite our efforts. Therefore, our knowledge about the three species from the Trinil outcrops, A. trinilprima , A. trinilsecunda and A. triniltertia , is restricted to our interpretation from his descriptions. Although some of the morphological traits of our material could match the description of A. trinilsecunda , the presence of a columellalike structure was not observed. The fossils included here are more similar to the extant species A. vaughani with radial corallites that exhibit the characteristic thickened walls. They compare well with the specimens RGM 20979 from Pulau Bahuluang and MTQ G48344 from Nain Island, Sulawesi. Other fossil specimens from distant localities in Sumatra and Timor Leste were also interpreted within the variation range of the A. vaughani species.

Figures

Figure 26. Acropora vaughani. A–C, RGM 3998, Sonde, Java, Pleistocene (0.8–2.6 Ma). A, whole specimen. B, detail of branch showing irregular distribution of radial corallites. C, detail of radial corallites showing thickened walls. D and E, RGM 167823, Fatu Lulih, Timor, Pliocene to Early Pleistocene (1.8–5.3): D, three fragments showing mid branch and branch tip (up right); E, detail of radial corallites with round calices and thickened walls. F, RGM 125829, Nalawo Valley, Nias, Sumatra, Pleistocene (0.8–2.6 Ma), whole specimen.