Pectinula cancellata Leanza, 1943
LEANZA, A. F. 1943. Pectinula, nuevo género de pelecípodos en el lías de Neuquén. Notas del Museo de La Plata. Paleontología, 8 (53): 241-249, pl. 1. [p. 244, pl. 1, figs. 1-6]
1943 Pectinula cancellata Leanza, 1943
«Specimens of Posidonotis from the upper Pliensbachian to lower Toarcian of Chile and the lower Toarcian of Argentina have generally been assigned to P. cancellata (e.g., Leanza 1943, p. 244, Pl. 1, figs. 1-6; Damborenea 1987, p. 193, Pl. 14, figs. 1-12, text-figs. 28,29; see also Aberhan 1994, p. 20, Pl. 6, figs. 5, 6). Damborenea (1987) only tentatively separated P. cancellata from the North American forms based on its larger size, relatively smaller auncles, and weaker radial ribs. However, the morphological ranges of both the North and South American specimens overlap considerably, as demonstrated by the specimens figured in Pl. 1. Consequently, P. cancellata is regarded as a junior synonym of P. semiplicata.»
ABERHAM, M. & J. PÁLFY. 1996. A low oxygen tolerant East Pacific flat clam (Posidonotis semiplicata) from the Lower Jurassic of the Canadian Cordillera. Canadian Journal of Earth Sciences, 33: 993-1006, pl. 1, text-figs. 1-5. [p. 998]
|
«Affinities: P. dalnellii LOSACCO, from the late early Jurassic of Italy (LOSACCO 1942) is similar to the South American species in size and ornamentation pattern, but has a wider apical angle and more numerous radial folds (up to 36). The anterior auricle of the European species is unknown. The same differences are shown by the Greek material here tentatively assigned to P. dainellii (see text-fig. 30 here). Part of the material from the upper Lias of Monte San Giuliano, Sicily, named by DE GREGORIO (1930, tav. 5, fig. 12-13 only) as Daonella elegantissima could also belong to the Italian species of Posidonotis, though his illustrations and description are insuficient for a definite opinion.
The North American material was referred to three nominal species that are probably synonyms, their "differences" seem to be the result of post-depositional distortion, as already noticed by CRICKMAY (1933 b: 52): P. semiplicata (HYATT 1894: 414; CRICKMAY 1933b: 52, pl. 14, fig. 4-7), P. symmetrica (HYATT 1894: 414; CRICKMAY 1933 b: 52, pl. 14, fig. 1-3) and P. balteata (CRICKMAY 1928: 62, pl. 4, fig. e-g). Their shells are all smaller than those of P. cancellata, their auricles are relatively larger and their radial ribs seem to be stronger. Nevertheless, there is an overlap in the ranges of morphological variability of both the Nortb and South American material and it is even difficult to decide whether they should be considered as separate species or not. On account of the subtle differences mentioned above P. cancellata is provisionally maintained as a different taxon for the time being. HAYAMI (1961, pI. 14, fig. 7) illustrated material from the late Pliensbachian of Japan that he identified as Amonotis n. sp. These specimens are referable to Posidonotis, though the auricles are not known. They are smaller than P. cancellata shells and resemble P. dainellii in shape and number of radial folds.» DAMBORENEA, S. E. 1987. Early Jurassic Bivalvia of Argentina; Part 2, Superfamilies Pteriacea, Buchiacea and part of Pectinacea. Palaeontographica, Abteilung, A, Palaeozoologie-Stratigraphie, 199 (4-6): 113-216, pls. 1-14. [p. 194, 196]
|
Posidonotis cancellata (A. Leanza); S. E. Damborenea, 1987, Early Jurassic Bivalvia of Argentina; Part 2, Superfamilies Pteriacea, Buchiacea and part of Pectinacea, plate 14, figures 1-12.
|