Paleontological Research
Volume 8, Issue 3, 2004
Volumes & issues:
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Articles
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Revision of the genus Glyphithyreus Reuss, 1859 (Crustacea, Decapoda, Brachyura, Xanthoidea) and recognition of a new genus
View Description Hide DescriptionAbstractThe definition of the brachyuran genus Glyphithyreus Reuss, 1859 (= Plagiolophus Bell, 1858non Pomel, 1857) is herein restricted such that the genus now embraces four species ranging from Paleocene to Oligocene in age. Other species previously referred to the genus have been placed in other genera, resulting in one new genus, Chirinocarcinus, and four new combinations, Chirinocarcinus wichmanni ( Feldmannet al., 1995), Lobonotus sturgeoni ( Feldmannet al., 1995), Stintonius markgrafi ( Lőrenthey, 1907 [1909]), and Titanocarcinus bituberculatus ( Collins and Jakobsen, 2003). The referral of Glyphithyreus to the Panopeidae Ortmann, 1893, extends the range of that family into the Paleocene. The geographic range of Stintonius Collins, 2002, is extended from England to include Egypt as well.
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A humpback whale, Megaptera novaeangliae (Borowski, 1781), from the Pleistocene Kioroshi Formation of Inba-mura, Chiba Prefecture, central Japan
View Description Hide DescriptionAbstractA humpback whale skull was discovered in the upper Middle Pleistocene sand bed of Inbamura, Chiba Prefecture. The morphological features of the skull are summarized as follows: the supra-orbital process of the frontal is elongated laterally and its posterior margin is straight; the orbit is relatively short considering the skull size; the squamosal is slender and protrudes anterolaterally at an obtuse angle; the squamosal sulcus is not developed at the base of the zygomatic process; the dorsal shape of the supra-occipital is equilaterally triangular; the basioccipital and the basisphenoid are fused, forming a wide plane on the ventral surface; the alisphenoid is not exposed in the temporal region. Based on these characteristics, the specimen was identified as Megaptera novaeangliae (Borowski, 1781). This is the first record of M. novaeangliae in the western North Pacific during Pleistocene time. No fossil has yet been described systematically as M. novaeangliae from Pleistocene strata. Therefore, there is a strong possibility that the new material is the oldest M. novaeangliae fossil in the world.
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New cheilostome bryozoans from the Middle Miocene of Hokkaido, Japan, and the first fossil occurrences of Kubaninella and Hayamiellina gen. nov
View Description Hide DescriptionAbstractThree new species and one new genus of cheilostome Bryozoa are described from the Kaigarabashi Sandstone Beds (Kunnui Formation, late Middle Miocene) of southwestern Hokkaido. These are Hayamiellina constans (Cribrilinidae), Integripelta sakagamii (Eurystomellidae), and Kubaninella miocenica (Adeonidae). Monotypic Hayamiellina gen. nov. is also reported living at shelf depths off the Commander Islands, Bering Sea, and in the Gulf of Alaska. The finding of K. miocenica constitutes the first fossil record of the formerly monotypic genus Kubaninella. These new records, from a locality previously sampled for Bryozoa, underscore the inadequate level of sampling and taxonomic work on the evidently biodiverse and highly endemic bryozoan fauna of the Japanese Cenozoic.
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Evolutionary trends and biostratigraphic significance of the ostracode genus Stigmatocythere in the Cenozoic succession of India
View Description Hide DescriptionAbstractStigmatocythere Siddiqui is an important ostracode genus and occurs profoundly in sediments of marginal marine to shallow inner neritic origin in the Cenozoic succession of western India. Its species have short stratigraphic ranges and wide geographic distribution, which makes them good markers and helps in finer subdivision of the Cenozoic strata. Nineteen species including one new species Stigmatocythere (Bhatiacythere) khoslai have been recognized from Lower Eocene to Middle Miocene sediments of western India. Of these, Stigmatocythere (S.) obliqua Siddiqui is restricted to the upper part of the Lower Eocene. Stigmatocythere (S.) lumaria Siddiqui morphotype A and S. (S.) portentum Siddiqui are restricted to the upper part of the Middle Eocene (Bartonian) and Stigmatocythere (S.) lumaria Siddiqui morphotype B to the Upper Eocene. Stigmatocythere (Bhatiacythere) khariensis Khosla and Pant is restricted to the Lower Oligocene, while S. (S.) bermotiensis Khosla and Pant ranges from Lower Oligocene to Upper Oligocene and Stigmatocythere (S.) reticulata Khosla and Pant from Oligocene to Lower Miocene (middle part of Aquitanian). Stigmatocythere (S.) khoslai sp. nov. ranges from Aquitanian to lowermost Burdigalian, S. (S.) chaasraensis Guha ranges from uppermost Lower Oligocene to Lower Miocene (middle Burdigalian), and S. (B.) reversa Khosla, S. (S.) quilonensis Khosla and Nagori range from Aquitanian to middle Burdigalian, while S. (S.) latebrosa Lyubimova and Guha, S. (B.) spinosa Khosla and Nagori and S. (B.) interrupta Khosla and Nagori are confined to the Lower Miocene (lower to middle Burdigalian). S. (B.) rete Khosla and Nagori and S. (B.) arcuata Khosla and Nagori are confined to middle Burdigalian and S. (S.) multicostata Khosla and Nagori ranges from middle to upper Burdigalian. S. (S.) colini Bhandari is confined to the lowermost Middle Miocene and S. (S.) keeni Bhandari ranges up to the top of the Middle Miocene. The above species of the genus Stigmatocythere belong to five evolutionary lineages. They are: 1- Stigmatocythere (S.) obliqua – S. (S.) portentum, 2- S. (S.) reticulata – S. (S.) latebrosa – S. (S.) multicostata – S. (S.) keeni, 3- S. (S.) bermotiensis – S. (S.) quilonensis – S. (S.) chaasraensis, 4- S. (B.) khariensis – S. (B.) khoslai – S. (B.) reversa – S. (B.) rete – S. (B.) arcuata, 5- Stigmatocythere (B.) reversa – S. (B.) interrupta. These lineages are briefly discussed here.
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Low-diversity shallow marine benthic fauna from the Smithian of northeast Japan: paleoecologic and paleobiogeographic implications
View Description Hide DescriptionAbstractAn unusually low-diversity shallow marine benthic community in a siliciclastic setting was identified and described from the Lower Triassic (Smithian) Hiraiso Formation (Southern Kitakami Mountains, northeast Japan). The Hiraiso fauna includes bivalve species of widespread genera, such as Eumorphotis, Entolium, Bakevellia (Maizuria), Unionites, Neoschizodus, and the oldest record of the crinoid genus Holocrinus. Facies analysis enabled reconstruction of an environmental gradient ranging through storm-dominated sedimentary settings of various depths, thus allowing us to estimate the probable habitats of the shelly fossil assemblage. Regional comparison of contemporaneous shallow marine fossil localities (i.e., Southern Primorye, Maizuru Terrane, and Chichibu Terrane) demonstrated particularly striking similarity among the shallow marine benthic communities of these siliciclastic settings. We thus infer no substantial ecological recovery among these tropical shallow marine benthic communities in Smithian time.
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