Acropora papillare, Latypov, 1992

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 : 716-718

ACROPORA PAPILLARE ( LATYPOV, 1992)

FIGURE 19

Acropora papillare Latypov, 1992: 121 , fig. 6 Acropora indiana Wallace, 1994: 963 , fig. 4

Diagnosis

Colonies with semi-determinate growth, sub-arborescent shape, branches cylindrical to conical. Axial corallite dominates branch diameter. Radial corallites short tubular to labellate. Coenosteum of elaborated spinules, reticulo-costate on and in between corallites ( Wallace & Wolstenholme, 1998; Wallace, 1999).

Material studied

East Kalimantan: NHMUK PI AZ 6977 , TF275 , 310 specimen fragments from the same colony. Modern comparative material: Holotype of A. indiana MTQ G 46445, Rowley Shoals , Western Australia ; MTQ G48563 Kupang, West Timor, Indonesia.

Skeletal characteristics

Corallum . Probably sub-arborescent, branches tapering, length of specimen fragments 29.79–37.36– 46.14 mm, round in cross section, basal branch diameter 21.54–24.09– 26.48 mm, middle branch diameter 11.19–12.74– 14.96 mm, branch tip diameter 5.60–6.55– 7.45 mm. Branching in open wide angles 53.73–84.65– 119.14°, distance between branches at least 17–21.63– 31.53 mm.

Corallites. Axial corallite, round calice, profile length to first radial 1.30–1.53– 1.80 mm, outer diameter 2.40– 2.90– 3.20 mm, inner diameter 1.40–1.58– 1.70 mm, wall thickness 0.40–0.49– 0.60 mm, primary septa threequarters R, secondary septa one-quarter R; radial corallites gradually sized, mainly labellate, some short tubular interspersed with subimmersed corallites, round calices, lower wall thickened, profile length 1.60–1.92– 2.20 mm, angle 32.79–41.36–48.48°, outer diameter 1.06– 1.13– 1.20 mm, inner diameter 0.62–0.73– 0.77 mm, wall thickness 0.20–0.24– 0.31 mm, not touching, closely arranged, distance between centres 1.85–2.30– 2.78 mm, primary septa developed three-quarters R, axial margins sinuous, sometimes reaching the centre of the radial corallite, secondary septa up to one-quarter R. Corallite arrangement sequence 1–8–12–[12- up to 14].

Coenosteum. Smooth costate on corallite walls, reticulate with simple spinules between radial corallites; coenosteum amount between adjacent corallites 0.97– 1.16– 1.51 mm.

Occurrence

Early Miocene to Recent. This record is the earliest occurrence of the species with specimens found in the locality TF275 , Kari Orang, East Kalimantan, of Early Burdigalian age, 18–20 Ma. In the Recent, A. papillare occurs mainly in intertidal reef flats and it is distributed in the Indo-Pacific from Cocos-Keeling Islands to the Great Barrier Reef ( Wallace et al., 2012). Records from Indonesia include some localities in Sulawesi ( Table 4) .

Palaeoenvironment

The sediments exposed at locality TF275 were fine sand. Acropora papillare was found together with phacelloid colonies of Galaxea sp. , massive colonies of Dipsastraea sp. , and a few branching Porites specimens. This environment has been interpreted as a subtidal shallowwater environment with calm waters. The thin orange– yellow horizon containing reef corals overlies a bed> 5 m thick of grey silty clays with mollusc and azooxanthellate corals typical of the upper bathyal zone, ∼ 200 m depth. The erosive base of the reefal horizon on the upper bathyal bed suggests that the former bed containing corals is a turbidite carried down to bathyal depths (J. Todd, pers. comm., 2014).

Remarks

Specimens recovered from TF275 were collected together forming what could be interpreted as a single sub-arborescent colony with widely separated branches. The skeleton is porous and growth lamination was observed at the base of some branches ( Fig. 19C ). Morphological features and measurements for characters of branches and corallites resemble the modern specimen MTQ G48563 from Flores (Indonesia). However, radial corallites of the fossil specimen are never touching but widely apart. The coenosteal structure composed of simple spinules ( Fig. 19I ) is typical of the aspera species group, and is a key character allowing identification of the fossil specimen as A. papillare . Most radials on branches have degraded walls giving the appearance of subimmersed corallites, yet original aragonite may be still present.

Figures

Figure 19. Acropora papillare. NHMUK PI AZ 6977, TF275, Kari Orang, Bengalon, East Kalimantan, Early Miocene (18–20 Ma). A, aspect of a colony in situ as seen from below, showing corymbose to caepito-corymbose growth form. B, detail of a transverse section of a branch in the field, branch diameter approx. 15 mm. C, AZ 6977a–c, three cylindrical branches showing wide-open branching pattern and incipient branches. D, AZ 6977d, electron micrograph of a branch tip. E, AZ 6977d, top view of axial corallite. F, AZ 6977e, transverse section of branch showing eight radial corallites arranged around the axial. G and H, AZ 6977b: G, electron micrograph of radial corallites near the tip – short tubular and subimmersed radials; H, detail of tubular radial corallite with thickened lower wall. I, AZ 6977d, electron micrograph of reticulate coenosteum formed of a mix of simple and laterally flattened elaborated spinules.