Azumapecten tanassevitschi (Khomenko, 1934)
KHOMENKO, I. 1934. The stratigraphy of the Tertiary beds of the southwestern coast of the Schmidt Peninsula (northern Sakhalin). Transactions of the Geological Oil Institute [Serie A], 40: 12-85, pls. 1-19. [in Russian with English summary]. [p. 33, pl. 3, figs. 4, 5; pl. 4, figs. 1-5; pl. 5, figs. 3, 4; pl. 6, figs. 1, 2; pl.7, fig. 1]
1934 Pecten tanassevitschi Khomenko, 1934
1961 Chlamys daishakensis Masuda & Sawada, 1961
1977 Chlamys (Chlamys) sawanensis Omori, 1977
1961 Chlamys daishakensis Masuda & Sawada, 1961
1977 Chlamys (Chlamys) sawanensis Omori, 1977
I. P. Khomenko, 1934,
plates 3, 5, 6, 7, |
«Раковина крупнап, неравносторонняя, неравностворчатая; обе створки в одинаковой степени умеренно вздутые. Передние ушки приблизительно вдвое длиннее задних; биссусный вырез глубокий, ctenolium превосходо развит. Переднее ушко правой створки в верхней половине орнаментировано пятью грубыми чешуйчатыми закругленными ребрами, ширина которых увеличивается кверху; поверхность нижней половины ушка покрыта грубыми линиями нарастания. Переднее ушко левой cтвopки имеет 12 грубых закругленных чешуйчатых ребер, причем эти ребра или почти одинаковы, или кoe-где между более крупными вставляются болеc тoнкие; также ясно выражены линии нарастания. 3адние ушки обих cтвopoк менее массивны, и их скульптура значителЬно утoнченнее: кpoмe многочислениыx и теcно расположенных линий нарастания на каждой створке имеется по четыре токнких мелкочешуйчатыx ребра с большими равными между собой промежутками, на которыx выстунают по два тонкиx радиальных гребня. Число ребер 22, иногда почти совершенно одинаковыx, иногда несколько отличающиxcя по веmичине. Ребра выcокиe, их закругленные гребни покрыты многочисленными тонкими чешуями; межреберные промежутки глубокие, обычно шире ребер, иногдa равняются последним и очень редко уже ребер. Кроме концентрической скульптуры нарастания промежутки имеют второстепенные тонкие мелкочешуйчатые ребра, число которых может у крупных экземпляров доходить до трех; иногда второстепенные ребра прнлегают к главным с двух сторон, иногда только с одной, иногда встречаются отдельно от главных; вообше в этом отношении наблюдается большое разнообразие.
Размеры
Длина Bысота Коэф вздутость Коэф
мм мм высоты мм вздутости 112,0 124,0 110,7 27,8 25,3 85,0 94,0 110,6 21,5 25,3 79,0 87,0 110,1 20,0 25,3 Мелкие экземпляры oписываемой, формы слегка напоминают P. laetus Gld.,¹ но равномерность ребер, детали скульнтуpы и болыпая величина дают описываемой форме вполне самостоятельное значение. Также Р. tanassevitsthi напоминает формой и отделъными признаками Р. crassicostatus Sоw.,² но последний вид совершенно отличается скульптурой залних ушек, шириной и полной равномерностью ребер и отсутствием мелких промежуточных ребер. Напоминая скульптурой ребер нeсколько Р. kaneharai Уоk.,³ описываемый вид отличается формой, скульптурой ушек и дсталями скульптуры ребер.
Обнажение к югу от р. Пильтука (Nº 9).» ¹ А. Gоuld. Otia Conchologica. 1862, p. 177.
С. Lischkе. Japanische Meeres-Conchylen, Bd. I, 1869, р. 169, Taf. XII, Fig. 6, 7. S. Тоkunаga. Fossils fгom the Environs of Tokyo, Journ. Coll. Sс. Imр. Un. Tokyo, Vol. XXI, Art. 2, 1906, р. 65, pl. V, fig. 2. М. Yоkоyаmа. Fossils from Miura Репinsula, p. 152, pl. XIV. figs. 1, 2. М. Yоkоyаmа. Fossils from Upper Musashino of Kazusa and Shimosа, р. 180, pl. XIV, fig. 26. ² G. Dunkеr. Index Molluscorum maris Japonici. 1882, р. 239, tab. 13, fig. 28. ³ М. Yоkоyаmа. Tertiary Mollusca from Shiobara in Shimotsukе. Journ. Fac. Sc. lmp. Un. Tokyo, Vol. I, Рart 4, 1926, р.1З5, рl. XVIII, fig. 1; pl. XIX, figs. 1, 2, 5-7. I. P. KHOMENKO, 1934
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«Type locality.— Exposure along the coast to the south of Piltuk River, western part of Schmidt Peninsula, Sakhalin. Lectotype no. 30/5043.
Original description.-- "Shell thick, inequilateral, inequivalve; both valves moderately inflated in same extent. Anterior auricle nearly twice as long as posterior one; byssal notch deep, ctenolium considerably variable. Upper half of anterior auricle of right valve ornamented with five rough grooves between imbricated and rounded ribs, becoming more wide toward upper; surface of lower half of auricle sculptured by deep growth lines. Anterior auricle of left valve with 12 deeply rounded and imbricated ribs, these ribs nearly equal or finer ribs intercalated with stronger ones in places; growth lines also distinct. Posterior auricle of both valves less massive, and their sculpture considerably fine: except for many narrowly arranged growth lines, four fine weakly imbricated radial ribs separated by equal interspaces, with two fine radial threads. Number of ribs 22, nearly equal or different from each other to some extent. Ribs high and rounded with many fine imbrications; interspaces deep, usually broader than ribs, but sometimes equal, very rarely narrower than ribs. Besides concentric sculpture due to growth, interspaces of ribs with fine and weakly imbricated secondary riblets; number of secondary riblets attaining three in large sample; secondary riblets situated on both sides or one side of main ribs in some cases, separated from main ribs in another cases; wide range of variation usually recognized on secondary ribs. (Originally in Russian, translated into English)". Remarks.— Chlamys tanassevitschi (Syntypes, Figures 5-1, 2) is characterized by its large shell size (maximum length 112 mm, according to Khomenko, 1934), narrowly elongated anterior auricle of right valve ornamented with four radial ribs, and 22 to 24 imbricated radial ribs on its shell surface with a few intercalated radial threads. The Ogikubo specimens are large in size (maximum length 126.9 mm) and have similar auricular characters. Although they have less numerous radial ribs (about 20), these ribs are scaled with fine radial threads on both flanks and three radial threads in each interspace. Therefore, the Ogikubo specimens are clearly identifiable with the present species. Krishtofovich (1964) and Zhidkova et al. (1968) misjudged the present species as a synonym of the Recent species Chlamys farreri nipponensis Kuroda. However, it is easy to distinguish tanassevitschi from the Recent species by the larger shell, narrowly elongate anterior auricle of right valve and less numerous ribs on the auricles of both valves. When Masuda and Sawada (1961) proposed Chlamys daishakaensis (Holotype, Figure 5-4), based on specimens from the Early Pleistocene Daishaka Formation, they did not compare it with the present species. As the result of examination of the type specimens, some topotype specimens and some specimens from the Setana Formation in Hokkaido (Figure 4-1), I can consider Chlamys daishakaensis to be a synonym of C. tanassevitschi because of its large shell size, similar shell shape and nearly equal number of ribs. Many previous authors frequently identified the present species with Chlamys iwakiana established by Yokoyama (1925a). As already pointed by Masuda and Sawada (1961), Chlamys iwakiana differs from C. tanassevitschi by having a less inflated left valve and less elevated radial ribs. According to Omori (1977), his new species, Chlamys sawanensis slightly differs from "C. iwakiana" (= C. tanasseivitschi) by having fewer secondary radial threads. However, his two specimens are smaller (maximum length, 66 mm) than the present species. Moreover, some specimens from the Sawane Formation (Figures 4-5, 5) show the same characteristics as the present one in shell sculpture and other features. Comparison.— The present species is allied to Chlamys (Leochlamys) tugidakensis MacNeil (1967) from the Pliocene? of the Tugidak Island in its narrowly elongate shape of auricle, and in similar form and number of radial ribs to the present species. The development of secondary riblets is the most obvious difference between Chlamys tanassevitschi and C. tugidakensis. Interstitial riblets are rarely present on the right young valves of tugidakensis. The Recent species, Chlamys (Leochlamys) farreri (Jones et Preston) is another allied species to the present one. As pointed out above, the Jarreri has a broader anterior ear of right valve, more numerous radial ribs on the anterior auricle (about six to seven on right valve, about twenty on the left), and lower radial ribs on the shell surface of both valves. Distribution.— Pliocene Pomyr Suite in northern Sakhalin, Early Pleistocene Shimonopporo, Setana and Tomikawa Formations in Hokkaido, Plio-Pleistocene Daishaka, Sasaoka, Haizume, Sawane, and Ogikubo Formations in Honshu.» AMANO, K. 1994. Diversity of Chlamys (Bivalvia) from
the Pliocene Ogikubo Formation, Central Japan. Transactions and Proceedings of
the Palaeontological Society of Japan [N. S.], 176: 661-676, figs. 1-7. [p. 668, 671]
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Chlamys (Leochlamys) tanassevitschi (Khomenko); K. Amano, 1994, Diversity of Chlamys (Bivalvia) from the Pliocene Ogikubo Formation, figures 4.1, 4.2, 4.4-4.7; figures 5.1, 5.2 (type specimens).
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