Tetraclitella purpurascens miocenica, Buckeridge, John S., 2008

Buckeridge, John S., 2008, Two new species and a new subspecies of Tetraclitella (Cirripedia: Thoracica) from the Cainozoic of Australia and New Zealand and a consideration of the significance of tubiferous walls, Zootaxa 1897, pp. 43-52 : 45-47

Tetraclitella purpurascens miocenica subsp. nov

1983:? Tetraclitella sp. cf. T. purpurascens (Wood, 1815): Buckeridge, 77–78, Plate 5 figures c, d.

Diagnosis: Tetraclitella having paries externally with narrow longitudinal ridges separated by more than their own width; radii thick, broad, with strong ridges sub-parallel to base of shell; radii not elevated over adjacent parietal surface; opercula unknown.

Distribution: Late Miocene to early Pliocene, Victoria, Australia.

Holotype: P47193, a latus (figured in Buckeridge 1983: plate 5 figures c, d), from the late Miocene- Pliocene Moorabool Viaduct Formation (see Holdgate et al. 2002; Birch, 2003).

Material: Moorabool Viaduct Formation (previously Moorabool Viaduct Sands): P47193, a latus, length 5.9 mm; from Moorabool, Victoria. Age: Late Miocene-Pliocene (Cheltenhamian-Kalimnan), Grangeburn Formation: P47189, a latus, from Forsyths, Victoria. Age: Early Pliocene (Kalimnan). All specimens are held in the type collection of the Museum of Victoria, Melbourne.

Description (based upon latera only): Shell small, with medium-low profile; orifice large, probably rhomboidal; exterior of latus with up to six narrow, well-spaced longitudinal ridges separated by slightly more than their own widths, ridges crossed by fine, sinusoidal transverse growth lines; radii broad with horizontal summits, growth ridges strong, parallel to base of shell and crossed by striae parallel to articular margin; radii thick, relatively flat, slightly depressed with respect to paries; sheath weak, extending internally for slightly more than half height of paries; longitudinal pores rounded in section, with a commensurate thickening of pore walls; base apparently membranous; carina, rostrum and opercula unknown.

Comparison with other species: Tetraclitella purpurascens miocenica subsp. nov. is distinguished from Tetraclitella purpurascens purpurascens by the more widely spaced external ribbing, the weakly depressed radii, a higher conic shell, and the rounded parietal pores with relatively thickened pore walls. This taxon differs from Tetraclitella nodiscuta sp. nov. by its less rugose external ribbing, and the rounded rather than polyhedral longitudinal pores. It has a smaller, more delicate shell, and lacks the inner row of wide parietal pores that occur in Tetraclitella judiciae sp. nov.

Remarks: No further material has been recovered since this taxon was described and figured in Buckeridge, 1983.

Etymology: Chronologic, after the Miocene epoch from which the oldest specimens were found.