Ptilorhynchia obscuricostata Dagys 1968
Ptilorhynchia obscuricostata Dagys, 1968 Fig. 6.9–6.17 1968 Ptilorhynchia obscuricostata new species —Dagys, p. 63, pl. 5, fig. 6, 7, text-fig. 42. 2011 v. partim ‘ Lacunosella ’ sp.—Hammer et al. , p. 21, table 2. Material and occurrence. Seep 3 (PMO 224.915), seep 9 (PMO 224.881, PMO 224.880), see...
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| Format: | Text |
| Language: | unknown |
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Zenodo
2014
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| Online Access: | https://dx.doi.org/10.5281/zenodo.4952546 https://zenodo.org/record/4952546 |
| Summary: | Ptilorhynchia obscuricostata Dagys, 1968 Fig. 6.9–6.17 1968 Ptilorhynchia obscuricostata new species —Dagys, p. 63, pl. 5, fig. 6, 7, text-fig. 42. 2011 v. partim ‘ Lacunosella ’ sp.—Hammer et al. , p. 21, table 2. Material and occurrence. Seep 3 (PMO 224.915), seep 9 (PMO 224.881, PMO 224.880), seep 12 (PMO 224.884). Description. Wide triangular outline. Biconvex profile. Broad flat-topped uniplication of the anterior commissure. Smooth shelled with weak or incipient costae developed at the anterior margin, primarily in the fold/ sulcus of the anterior commissure. A few growth lines are present. Median septum and dental lamellae are visible. Other internal structures have not been investigated. Discussion. The generally smooth and uniplicate form with the development of costae only towards the margin of the valves was one reason why this material was tentatively referred to ‘ Lacunosella ’ (Hammer et al. 2011), due to its resemblance to L . groenlandica Owen (1976; and in Harper et al. 2005). However, the smooth shell, presence of costae at the valve margins, and broad uniplication of the anterior commissure are also characteristic of Ptilorhynchia obscuricostata (Dagys 1968). Even in the absence of serial sections of the present material, some useful observations can be made. The Spitsbergen specimens do not appear to show the massive shell-thickening of the ventral umbo that Owen observed in serial sections of L . groenlandica (Owen 1976, fig. 3). The presence of distinct dental lamellae in the umbo of the ventral valve is consistent with Ptilorhynchia , but of course not diagnostic of this genus as they are present in many rhynchonellide genera. In L. groenlandica Owen dental lamellae are massively overgrown (Owen 1976, fig. 3). A median septum is present in the dorsal valve of the Spitsbergen material whereas Lacunosella lacks a median septum (e.g. Owen 1976, fig. 3; Manceñido & Owen 2002, p. 1208). Stratigraphic and geographic distribution. Upper Volgian–uppermost Ryazanian, Spitsbergen and Lower Volgian of northern Siberia (Dagys 1968). : Published as part of Sandy, Michael R., Hryniewicz, Krzysztof, Hammer, Øyvind, Nakrem, Hans Arne & Little, Crispin T. S., 2014, Brachiopods from Late Jurassic-Early Cretaceous hydrocarbon seep deposits, central Spitsbergen, Svalbard, pp. 501-532 in Zootaxa 3884 (6) on pages 513-515, DOI: 10.11646/zootaxa.3884.6.1, http://zenodo.org/record/4951742 : {"references": ["Dagys, A. S. (1968) Jurskiye i rannemelovye brakhiopody Severa Sibiri [Jurassic and Early Cretaceous brachiopods from northern Siberia]. Akademia Nauk SSSR Sibiroskoe Otdelenie Institut Geologii I Geofiziki (IGIG) Trudy [Institute of Geology and Geophysics, Academy of Sciences of the USSR, Siberian Branch, Transactions], 41, 1 - 167. [In Russian]", "Hammer, O., Nakrem, H. A., Little, C. T. S., Hryniewicz, K., Sandy, M. R., Hurum, J. H., Druckenmiller, P., Knutsen, E. M. & Hoyberget, M. (2011) Hydrocarbon seeps from close to the Jurassic - Cretaceous boundary, Svalbard. Palaeogeography, Palaeoecology, Palaeoclimatology, 306, 15 - 26. http: // dx. doi. org / 10.1016 / j. palaeo. 2011.03.019", "Owen, E. F. (1976) Some Lower Cretaceous brachiopods from East Greenland. Meddelelser om GrOnland, 171 (3), 1 - 19.", "Harper, D. A. T., Alsen, P., Owen, E. F. & Sandy, M. R. (2005) Early Cretaceous brachiopods from North-East Greenland: biofacies and biogeography. Bulletin of the Geological Society of Denmark, 52, 213 - 225.", "Owen, E. F. & Mancenido, M. O. (2002) Rhynchonelloidea. In: Kaesler, R. (Ed.), Treatise on Invertebrate Paleontology, Part H (Brachiopoda Revised) 4, The Geological Society of America and The University of Kansas Press, Boulder, Colorado and Lawrence, Kansas, pp. 1279 - 1308."]} |
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