Annachlamys murrayana (Tate, 1886)
TATE, R. 1886. The lamellibranchs of Older Tertiary of Australia, Part I. Transactions and Proceedings and Report of the Royal Society of South Australia, 8: 96-158. [p. 105, pl. 7, figs. 5a, 5b]
1886 Pecten murrayanus Tate, 1886
R. Tate, 1886, plate 7.
|
«Shell orbicular, fan-shaped, somewhat thin, scarcely equilateral, projecting slightly in front, inequivalve; valves rayed with about 20 rounded ribs broader or equal in breadth to the concave furrows, the whole crossed by close-set, thin, erect lamellae coincident with the margin; the lamellae increase in denseness from the umbo forward. Interior with flat ribs corresponding with the exterior furrows.
Left valve slightly and regularly convex; umbo acute, not extended beyond hinge line. Ears unequal, the anterior large roundly truncate, finely striated, perpendicularly and faintly rayed; the posterior elongate, arcuate, prominently rayed and concentrically striated. Right valve nearly flat, depressed at the umbo; ears equal truncate, finely striated perpendicularly, faintly rayed. Dimensions.— Length, 47 ; height, 45 ; thickness through both valves, 10 millimetres. Localities.— Common in the calciferous sandstone of the Middle Murravian, Blanchetown, &c.; rare in the Lower Murravian at Mannum. Not uncommon at Muddy Creek, Hamilton. This species belongs to a small group represented by P. solaris, Born, but it is not identical with any of the living species monographed by Reeve. P. solarium, Lamk., a fossil species of the European Tertiary, is also of the same type, but P. Murrayanus is distinguished by its fewer ribs and smaller wings. P. leopardus, Reeve, is its nearest ally, but the ribs are fewer, separated by wide interspaces, and is scarcely equivalve.» RALPH TATE, 1886
|
«Occurrence and time range. Longfordian (in Gippsland); Batesfordian to Bairnsdalian. Most records are Balcombian, as A. murrayana is common in Morgan Limestone on the Murray River and abundant in Muddy Creek Formation at Muddy Creek, near Hamilton. Excellent, typical specimens occur at Brock’s Quarry and Darriman Quarry, near Longford (Longfordian) but there are no other records before Batesfordian, and A. murrayana seems to have replaced A. rhipidata abruptly. Typical specimens occur in several Batesfordian limestone outcrops in Gippsland also. Baimsdalian specimens are known from very few localities, but a few specimens have been examined from the youngest part of Fyansford Formation and from Port Campbell Limestone. Thereafter, Annachlamys disappeared from the fossil record of southern Australia, except for Late Pleistocene and Holocene occurrences in the Perth and Carnarvon basins, Western Australia.
Remarks. The evenly and regularly, coarsely costate radial sculpture, identical on the two valves, the even, widely spaced coarser series of commarginal lamellae, the weakly inflated LV and particularly flattened LV umbonal area, the much more strongly inflated RV, the narrow, indistinct dorsal and intermediate hinge teeth, and the very shallow byssal notch show that this is a typical species of Annachlamys, closely resembling the tropical living type species, A. flabellata (Lamarck). It differs from A. flabellata in its smaller size (to c. 65 mm long; A. flabellata reaches 100 mm: AMS Cl 19782, 60 m, off Tin Can Bay, Queensland), in having an evenly curved margin, without the rather elongate, laterally extended anterodorsal and posterodorsal margins of A. flabellata, and in maintaining the prominence of the radial costae down the whole height of the disc, rather than the costae becoming lower and wider down the disc as in A. flabellata. Differences from A. rhipidata are pointed out above.» BEU, A. G. & T. A. DARRAGH. 2001. Revision of southern Australian Cenozoic fossil Pectinidae (Mollusca: Bivalvia). Proceedings of the Royal Society of Victoria, 113: 1-205, figs. 1-67. [p. 151, 153]
|
Annachlamys murrayana (Tate); A. G. Beu & T. A. Darragh, 2001, Revision of southern Australian Cenozoic fossil Pectinidae, figures 54A, B, F.
|
«The fossil record of Annachlamys appears to be limited to the Neogene (Miocene to Pleistocene) of the Indo-Pacific region. Examples are Annachlamys okinawaensis Noda, 1991, from the Ryukyu Islands, southwest Japan, Pecten (Chlamys) suvaensis Mansfield, 1926, and Pecten (Chlamys) nausorensis Ladd, 1934 from the late Miocene or early Pliocene of the Fiji Islands, and Pecten murrayanus Tate, 1886, from the Morgan Limestone of South Australia. The last species is possibly the oldest known Annachlamys. According to Ludbrook (1973: table I) the Morgan Limestone contains planktic foraminiferal zones N7 and N8. According to Berggren et al. (1995) these are of late Burdigalian and Langhian age. Roger (1939: 16) noted that the extant species Pecten leopardus, which is now assigned to Annachlamys, is known from the Miocene of Java and that it is probably a living representative of his Chlamys rotundata group, a group that is closely allied to Gigantopecten (see Bongrain 1988). Indeed, some Annachlamys have an unusual ontogenetic shift in convexity of the left valve, with the proximal part flattened, recalling the more extreme expression of this condition in the Gigantopecten clade.»
WALLER, T. R. 2006. New Phylogenies of the Pectinidae (Mollusca: Bivalvia): reconciling Morphological and Molecular Approaches. In S.E. Shumway & G.J. Parsons (Ed.) 2006: Scallops: Biology, Ecology and Aquaculture, 1-44. [p. 27, 28]
|