Reticulochlamys proximus (Ihering, 1897)
IHERING, H. VON. 1897. Os molluscos dos terrenos terciarios da Patagonia. Revista do Museu Paulista, 2: 217-382, pls. 3-9. [p. 229, pl. 8, fig. 48]
1897 Pecten proximus Ihering, 1897
H. von Ihering, 1897, plate 8.
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«Pecten centralis Sow.
Est. VIII fig. 49
(valva esquerda) e 48 (valva direita sob a denominação "proximus")
Sowerby-Darwin 1. c. p. 376, Taf. líl, fíg. 32.
Pecten testa inaequivalvi, aequilaterali, tenui, subcirculari; valva sinistra depressa, costis magnis rotundatis 5—7 et liris squamosis numerosis, in interstitiis plerumque obsoletis, radiatis; valva dextra convexa costis 4—6 magnis rotundatis, liris squamiferis munitis, radiatis; auriculis radiatim liratis subaequalibus.
Long. 160, Alt. 170, Diam. circa 30 Mm. Form, santacruzensis (Jegua quemada). Esta espécie foi recolhida por Darwin em S. Julian, Port Desire e Santa Cruz e descripta por Sowerby com referencia a valva esquerda. A valva direita é mais convexa e tem os intervallos entre as costas quasi lisos ou só com alguns vestigios de linhas elevadas. Nesta valva direita falta quasi completamente a serra byssal, sendo apenas representada por algumas incisões pouco profundas. A valva esquerda tem 8 10 estrias escamosas nas costas cujo numero é de 5 ou de 7. Os intervallos são, ás vezes, lisos, ás vezes munidos de estrias escamosas e acontece que em grandes exemplares onde os intervallos são lisos, as estrias escamosas apparecem na peripheria inferior da valva. Das auriculas a anterior tem em geral 12, a posterior 7 linhas radiarias. São raros exemplares completos. A valva maior que vi tem 190 Mm. de comprimento. E' esta uma especie do género Pseudamussium parecida ao P. Simpsoni Phil, do terciário chileno. São tão différentes em forma e sculptura as duas valvas, que ao principio considerei a valva direita como espécie différente para a qual usei o nome de P. proximus. Nunca vi concha completa das duas valvas reunidas, e assim não é bem certo que foi com razão que reuni em uma especie estas valvas, o que entretanto é provavel.» HERMANN VON IHERING, 1897
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«Description.— Shell acline, large, attaining height of 220 mm, longer than high or as high as long, with right valve moderately inflated and left valve flat. Umbonal angle 100–105 degrees. Auricles subequal in size, separated from disc by deep channel; hinge length 46–51 percent of total length of shell; free margin of posterior auricles inclined posteriorly, free margin of left anterior auricle inclined anteriorly; auricular dorsal margin straight; one pair of well-marked resilial teeth; byssal notch extremely shallow in adults; ctenolium with one or three teeth in young stage. Both valves with five broad, rounded plicae that weaken ventrally; three central plicae higher than lateral ones; interspaces narrower than plicae on right valve and wider than interspaces on left valve; plicae and interspaces evenly ornamented by rounded, thick, widely spaced scaly riblets of equal width over entire disc. Shagreen microsculpture persistent throughout growth on both valves, appearing at beginning of radially sculptured stage on left valve (at shell heights between 10 and 15 mm) and at 25 mm on right valve, after commarginal lirae appear; more prominent than antimarginal ridgelets and commarginal lirae, and covers entire shell surface, crossing riblet crest of most specimens. Antimarginal and commarginal microsculptures developed as patches on riblet flanks and interspaces, more distinct in adult than in juvenile stages. Commarginal lirae dominate microsculpture in early ontogeny on right valve.
Type.— Holotype, a right valve MACN—Pi 240a from Yegua Quemada, (Monte León Formation, Early Miocene); height: 115.0 mm, length: 110.0 mm. Other material examined.— Eighteen right valves and 16 left valves, MACN—Pi 240b, CPBA 15.964–15.966, CPBA 16.889–16.895, EASPU 303–305; EASPU 307–308. Occurrence.— Monte Entrada, cerro Observación, Las Cuevas, and Yegua Quemada, (middle and upper Monte León Formation). Discussion.— One of the main sources of systematic confusion over Patagonian pectinids is the validity of the species Pecten proximus Ihering, 1897. This confusion was caused by Ihering (1897) referring a pair of isolated valves found at the top of the Monte León Formation to two different species. The left valve was included in Pecten centralis Sowerby (Ihering, 1897, pl. 8, fig. 49, MACN-pi 240a, Yegua Quemada, illustrated herein as Fig. 4.3) and the right in a new species he named P. proximus (Ihering, 1897, pl. 8, fig. 48, MACN-pi 240b, Yegua Quemada). Later, Ihering (1907) placed P. proximus in synonymy with P. centralis. However, subsequent findings of articulated shells of P. proximus and P. centralis have allowed the differentiation of two taxa, and recognition that the valve from the Monte León Formation that Ihering (1897) had initially assigned to P. centralis is the left valve of P. proximus. While Reticulochlamys proximus is restricted to the middle and upper horizons of the Monte León Formation (Austral Basin), Jorgechlamys centralis (Sowerby, 1846) is very common and restricted to the uppermost beds of the San Julián Formation and to the basal horizons of the Chenque Formation in the San Jorge Gulf (San Jorge Basin).» DEL RÍO, C. J. 2004. Revision of the large neogene pectinids (Mollusca: Bivalvia) of Eastern Santa Cruz and Chubut Provinces (Patagonia: Argentina). Journal of Paleontology, 78 (4): 690-699, figs. 1-6. [p. 693]
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Reticulochlamys proximus (Ihering, 1897); C. J. del Río, 2004, Revision of the large neogene pectinids of Eastern Santa Cruz and Chubut Provinces, figures 4.1-4.4.
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