Foveolocyathus kitsoni ( Dennant, 1901 )

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 293

Foveolocyathus kitsoni ( Dennant, 1901)

Figs. 7A–G

Trematotrochus Kitsoni Dennant, 1901: 50–51 , pl. 2, figs. 2a–c

(SA as a fossil).– Bell, 1981: 10 (type deposition). Foveolocyathus kitsoni: Cairns, 1997: 27 (listed).

New records. VICTORIA: Balcombian (Late Miocene) of Port Philipp, 15 including SEM 1003, USNM 67981.— QUEENSLAND (Marion Plateau): Franklin 03/99/D10, 4, USNM 1008759; Franklin 03/99/D11, 18: 17 (including SEM 1002) USNM 1008764 and 1, ZMUZ; Franklin 03/99/D12, 2, USNM 1008760; Franklin 03/99/D13, 6, USNM 1008761.

Types. Dennant reported this species to be abundant in the fossil record of South Australia, and designated a single specimen as type (holotype), but Bell (1981) listed syntypes as NMV P27082. Type Locality: Eocene of South Australia .

Diagnosis (of Recent specimens). Corallum conical and slightly compressed, the GCD:LCD ranging from 1.13– 1.27. Largest corallum (Franklin 03/99/D11) 3.77× 2.98 mm in CD and 5.67 mm in height. Costae rounded and equal in width (0.15–0.18 mm), covered by low spines 30–35 µm in height that project outward from the costae as well as laterally into the intercostal spaces. Intercostal furrows quite deep, about the same width as a costa (0.15 mm) and periodically bridged by slender bars about 75 µm in width, delimiting depressions 0.11–0.13 mm in length. Although these depressions appear to be pores, they do not penetrate the theca and are thus more properly termed pits. Most costae run from calice to base, but the medial C2 is part of a costal trifurcation involving its pair of flanking C3, the trifurcation occurring just above the base ( Fig. 7E). Another trifurcation involves the S 3 in each of the four end halfsystems and their adjacent pairs of C4, these trifurcations occurring half to three-quarters of the distance from the calice to the base. Septa hexamerally arranged in 3 cycles with an additional 4 pairs of S 4 in the end half-systems, for a total of 32 septa. The 6 S1 and 2 medial S2 are equal in size, highly exsert (about 1 mm), and have slightly sinuous axial edges. The other 4 S2 are equally exsert but only about 85% the width of an S1. The 4 S 3 in the 4 end half-systems are accelerated in size to about 75% the width of an S1, and each is flanked by a pair of S4. Their axial edges bend toward and fuse with their adjacent S2. The remaining 8 S3 and the 8 pairs of S4 are of equal exsertness (0.3 mm) and width (about 50% width of an S1). Axial edges of S1–2 and accelerated S3 are fused to a horizontal, central columella platform from which 2–4 slender columella papillae arise. Fossa very shallow, the columellar platform almost at the level of the calice.

Remarks. Four species of Foveolocyathus are known (Cairns, 1997): two Recent species endemic to eastern Australia and two Tertiary (Eocene to Miocene) species endemic to southern Australia. The shape of the corallum (GCD:LCD = 1.13–1.27) and number of septa (32) rule out an identification as either of the two Recent species, as well as one of the fossil species. The specimens described above are remarkably similar to the fossil species F. kitsoni , heretofore known only from the Eocene of South Australia and herein reported from the Late Miocene (Balcombian) and Victoria ( Figs. 7C,D,F). Although Dennant (1901) described the species based on a type with a GCD of 5.5 mm and having 40 septa, coralla less than 4.0 mm in GCD (e.g., some from USNM 67981), have only 30–32 septa arranged in the same manner as the Recent specimens, all of which are less than 4 mm in GCD and have 32 septa. Furthermore, the GCD:LCD range of 1.13–1.27 is consistent with that of the fossil specimens, 1.14–1.31 (including those from USNM 67981). The only substantive difference between the fossil and Recent specimens is that the intercostal width of the fossil coralla is only about half that (i.e., 65–80 µm) of the Recent specimens ( Figs. 7F,G), which produces intercostal pits that are elongate (i.e., twice as long as wide) instead of circular, as in the Recent coralla. Even with this difference, the Recent specimens are considered to be morphologically indistinguishable in most respects from those in the Miocene, and thus is identified as such.