Acropora halmaherae WALLACE & WOLSTENHOLME 1998
Creators: name: Santodomingo, Nadiezhda
name: Wallace, Carden C.
name: Johnson, Kenneth G.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Cnidaria
Anthozoa
Scleractinia
Acroporidae
Acropora
Acropora halmaherae

description: ACROPORA HALMAHERAE WALLACE & WOLSTENHOLME, 1998   
FIGURE 28  
 Acropora halmaherae Wallace & Wolstenholme, 1998: 258, fig. 54   
 Diagnosis   
Colonies arborescent to hispidose with indeterminate growth, composed of slender branches. Radial and axial corallites contribute equally to branch structure. Radial corallites tubular exsert, regularly distributed. Coenosteum reticulate, elaborated spinules (Wallace & Wolstenholme, 1998; Wallace, 1999).  
 Material studied   
Sumatra: RGM 125830, 4 specimens; RGM 791828, 1 specimen; RGM 125828, 4 specimens; RGM 791813, 1 specimen.  
 Modern comparative material: Holotype, MTQ G51513, Halmahera, Indonesia.   
 Skeletal characteristics   
 Corallum. Specimens show evidence of arborescent to hispidose colony form, branch length 13.48–19.01– 36.15 mm, branch angle 54.21–59.01–64.97°, mid branch diameter 3.25–5.00– 6.24 mm, round on transverse section, minimum distance between branches 7.80– 8.84– 9.88 mm; growth probably indeterminate.   
 Corallites. Axial corallite visible in incipient branches and transverse sections, outer diameter 1.55–1.90– 2.26 mm, inner diameter 0.80–0.99– 1.42 mm, wall thickness 0.31–0.39– 0.46 mm, primary septa up to two-thirds R, secondary septa up to one-quarter R; radial corallites evenly sized, irregularly dispersed on the branches, not touching, mostly tubular exsert, round to nariform calices, projected almost perpendicular from the branch in angles of 37.09–53.68–71.62°, profile length 0.59–1.57– 2.39 mm, angle, outer diameter 0.93– 1.25– 1.52 mm, inner diameter 0.45–0.60– 0.77 mm, wall thickness 0.19–0.25– 0.35 mm, distance between centres 2.04–3.47– 4.97 mm, primary septa up to two-thirds R, straight and smooth edges, secondary septa absent or visible as points. Corallite arrangement sequence 1–2– 4–4 up to 6.   
 Coenosteum. Reticulate with evenly arranged elaborated spinules rarely arranged into costae (Fig. 28C). Coenosteum amount 0.95–1.63– 2.21 mm.   
 Occurrence   
 Late Miocene (?) to Recent. The earliest occurrence is one poorly preserved specimen from Ci Bining in Java of Tortonian age, 8.5–11.6 Ma, and although it is similar to modern specimens of A. halmaherae, the identification remains uncertain. The other fossil material comes from Gawo and Mola Valley, Nias, Sumatra, of Calabrian to Gelasian age, 0.781 –2.588 Ma. These occurrences extend the distribution of the species to the eastern Indian Ocean in the Pleistocene. On modern reefs, A. halmaherae has a narrow distribution as it is only known from its type locality, Halmahera Island, West Papua, and some sparse records in Papua New Guinea, Micronesia and Marshall Islands (Table 4, Wallace et al., 2012).   
 Palaeoenvironment   
 Fossil corals in Ci Bining from the Ci Lanang beds include a rich fauna of several colony forms and genera such as Galaxea, Stylophora, Hydnophora, Fungia and Pocillopora that were preserved into clay-rich sediments and interpreted as rolled down from upper parts of the reef (Gerth, 1921). Specimens from Gawo and Mola Valley were recovered with contrasting faunas of azooxanthellate and shallow-water corals (Gerth, 1925). Acropora halmaherae inhabits protected sandy slopes on modern reefs (Wallace & Wolstenholme, 1998; Wallace, 1999).   
 Remarks   
 The specimen RGM 791828, previously identified as A. duncani (Gerth, 1925), was re-interpreted in this study. In addition, the specimens left in open nomenclature including RGM 791813 (Gerth, 1921), RGM 125828 and RGM 125830 (Gerth, 1925) were allocat- ed to this species. With their apparently hispidose colony form, slender branches and the typical tubular exsert corallites almost perpendicular from the main axis, these fossil specimens were assigned to A. halmaherae, and they compare well to the holotype MTQ G51513, Halmahera, Indonesia. Its protruding tubular corallites resemble those of A. abrohlosensis, but the latter species has thicker branches and more openly reticulate coenosteum. The fossil specimens of A. halmaherae from Nias represent the westernmost report of the species and extend its distribution to the Indian Ocean in the Pleistocene.
description: Published as part of 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, pp. 677-763 in Zoological Journal of the Linnean Society 175 (4) on page 733, DOI: 10.1111/zoj.12295, http://zenodo.org/record/5339562