Acropora lavandulina (Michelin, 1840)

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 : 726

ACROPORA LAVANDULINA ( MICHELIN, 1840)

FIGURE 24

Madrepora lavandulina Michelin, 1840: 67 , pl. 14, fig. 2a, b; Wallace, 2008: 327, fig. 12; Wallace & Bosellini, 2014: 17–18, fig. 12.

Madrepora lavandulina var. inaequilatera von Fritsch, 1878: 127 , pl. 17. fig. 5, pl. 18, fig. 3.

Acropora sp. Wilson & Rosen, 1998: fig. 10L.

Diagnosis

Corymbose (?) colony with tapering branches; radial corallites evenly sized and distributed, not touching, tubular with round calices ( Wallace, 2008).

Material studied

Sulawesi: NHMUK PI AZ 1213 , Tonasa, 1 specimen cut into four fragments and two thin sections .

Fossil comparative material: NHMUK Pl AZ R54844, France, Middle Eocene.

Skeletal characteristics

Corallum . Full colony preserved within a limestone, probably with corymbose form, branch length 22.77– 30.0– 33.80 mm, mid branch diameter 6.16–6.89– 7.41 mm, round in cross section; a short branch, length 5.7 mm, extends from the main axis forming an angle of 76° ( Fig. 24A ).

Corallites. Axial corallites visible in transverse and longitudinal sections, inner diameter 1.10–1.84– 2.63 mm, primary septa developed three-quarters R, secondary septa observed as points, arranged as S1>>S2 ( Fig. 24C–E ); radial corallites evenly sized, tubular with round calice, outer diameter 1.01–1.29– 1.58 mm, inner diameter 0.51–0.78– 0.96 mm, evenly distributed, not touching, profile length 1.39–1.66– 1.86 mm, exert in angles 29–31.7–35° ( Fig. 24B ), primary septa up to onequarter R, secondary septa not observed. Corallite arrangement sequence 1–[?3]–up to 6.

Coenosteum. Not observed.

Occurrence

Eocene to Early Oligocene. The earliest occurrence of A. lavandulina is from its type locality in France of Eocene age ( Wallace, 2008). Previous fossil records from the Oligocene include: Chattian specimens from France, Upper Rupelian–Lower Chattian specimens from Italy. From the Miocene are Aquitanian specimens from Portugal and Burdigalian material from Italy and France ( Wallace, 2008; Wallace & Bosellini, 2014). The Tonasa specimen is of Early Oligocene age, Rupelian, 28.1– 33.9 Ma.

Palaeoenvironment

The Tonasa Limestone is an extensive carbonate platform of Eocene to Middle Miocene age ( Wilson & Moss, 1999); A. lavandulina occurs in Oligocene facies that have been interpreted as small coral patch reefs deposited at low to moderate energy with shallow to moderate depths in the photic zone ( Wilson, 1995).

Remarks

This fossil material is the earliest occurrence of the genus Acropora in the Indo-Pacific. It was previously illustrated in Wilson & Rosen (1998: fig. 10L) and left under open nomenclature. In this study, the specimen is interpreted as A. lavandulina based on measurements of characters that are comparable to the specimen NHMUK Pl AZ R54844 from the Middle Eocene of France ( Wallace, 2008). Von Fritsch (1878) described a specimen from north-east Borneo of Oligocene age as A. lavandulina var. inaequilatera based on the unequal distribution of the corallites around the branches; although von Fritsch’s material was not available for comparison with the Tonasa material, the two illustrations ( von Fritsch, 1878: pl. 17. fig. 5, pl. 18, fig. 3) and complete description suggest that his specimen can also be interpreted as A. lavandulina . Felix (1921) reported one additional record of this species from Gunung Badupar, East Kalimantan, of Late Miocene in age; however, there is neither material available nor illustration, and the description is rather incomplete, so this record is presented with doubt in the stratigraphic range chart ( Fig. 6 ). None of the different polished or thin sections available show conclusively the colony type of the species; however, its resemblance to the extant Acropora aculeus from the latistella species group and same orientation of branches in one of the polished sections ( Fig. 24C ) allow us to predict a corymbose colony. The corallite arrangement sequence is inferred from the different sections that show a maximum of six radials around the axial ( Fig. 24C, D ).

Figures

Figure 6. Stratigraphic range of Acropora and Isopora species. *Species from this study; remaining ranges were gathered from the literature review. Extension of the stratigraphic range based on the fossil material of this study is indicated as (←) for the earliest occurrence or (→) for latest occurrence. (?) Uncertain identification of Acropora lavandulina from Felix (1921). (M) Occurrence of fossil in the Miocene, 5.3–23 Ma, as no information on stratigraphic detail was available for some localities.

Figure 24. Acropora lavandulina. NHMUK PI AZ 1213, Tonasa, Sulawesi, Oligocene (28.1–33.9 Ma). A, AZ 1213a, polished section of the whole specimen preserved in a limestone. B, AZ 1213d, photomicrograph of longitudinal section showing tubular radial corallites evenly sized and distributed. C, AZ 1213b, polished section showing axial corallites in transverse section of three branches (upper middle) and a longitudinal section of a branch tip (down right). D, AZ 1213c, transverse section showing axial corallite. E, AZ 1213e, photomicrograph of transverse thin section.