Arthraster dixoni Forbes 1848
| Autor: | Gale, Andrew S. |
|---|---|
| Rok vydání: | 2020 |
| Předmět: | |
| ISSN: | 0269-3445 |
| DOI: | 10.5281/zenodo.4510545 |
| Popis: | Arthraster dixoni Forbes, 1848 Figures 1A, B, 2A, B 1848 Arthraster dixoni Forbes: p. 467. 1850 Arthraster dixoni Forbes: p. 336, pl. 23 fig. 1. p 1907 Arthraster dixoni Forbes. —Spencer: p. 91, pl. 18: fig. 1 only. 1913 Arthraster dixoni Forbes. —Spencer: p. 140. 1918 Arthraster dixoni Forbes. —Spencer: p. 168. 1966 Arthraster dixoni Forbes. —Spencer & Wright: U74, fig. 64.8. Diagnosis. Arthraster in which the crest on the extraxial arm ossicles is low and weakly sculptured. Type. NHMUK 47000, Middle Turonian of Balcombe, Sussex, U.K. Description. Arms cylindrical, elongated, disc small (Fig. 1A). Arms made up of 7 rows of extraxial ossicles, including radials (1), marginals (2 pairs) and actinals (1 pair). Actinals, inferomarginals, superomarginals in longitudinally and transversely aligned rows, bearing central, transverse crest. Radials with tall crest, concave distally. Abactinal surface of disc (Fig. 1B) rimmed by broad supero- and inferomarginals, including single interradial pair. Abactinal ossicles of disc small, round to oval, bearing central process. Adradials small, 4 pairs in each arm, only extending into base of arm. Remarks. The well-preserved actinal surface of the holotype has been illustrated a number of times (see synonomy, above), and the basic construction of the arm has been described. However, Spencer (1918) and Spencer & Wright (1966: fig. 64.8) mistook the two rows of actinal ossicles for adambulacrals, which appear on the edges of the ambulacral groove. In 2005, I was permitted to develop the part of the abactinal surface of the disc and basal arms of the holotype, which showed considerable similarities with the same parts of the living genus Chaetaster. These include the ridged interradial marginal ossicles, and the small abactinal ossicles of the disc. Published as part of Gale, Andrew S., 2020, The fossil record of the asteroid (Echinodermata) family Chaetasteridae Sladen 1889 and subfamily Hyalothricinae Fisher, 1911, pp. 144-150 in Zootaxa 4858 (1) on pages 145-148, DOI: 10.11646/zootaxa.4858.1.11, http://zenodo.org/record/4411478 {"references":["Forbes, E. (1848) On the Asteriadae found fossil in British strata. Memoirs of the Geological Survey of Great Britain, and of the Museum of Practical Geology in London, 2, 457 - 482.","Bruzelius, N. (1805) Dissertatio sistens species cognitas asteriarum, quamr. sub praesidio A. J. Retzius exhibet N. Bruzelius. Berlingianis, Lundae, 37 pp.","Hess, H. (1970) Schlangensterne and Seesterne aus dem oberen Hauterivian \" Pierre Jaune \" von St-Blaise bei Neuchatel. Eclogae geologiae Helvetica, 63, 1069 - 1091.","Spencer, W. K. (1918) A monograph of the British Palaeozoic Asterozoa. Monograph of the Palaeontographical Society, Part 3, pp. 109 - 168, pls. 6 - 13. https: // doi. org / 10.1080 / 02693445.1918.12088367","Spencer, W. K. & Wright, C. W. (1966) Asterozoans. In: Moore, R. C. (Ed.), Treatise on Invertebrate Paleontology. Part U. Echinodermata 3 (1). Geological Society of America and University of Kansas Press, Lawrence, Kansas, pp. U 4 - U 107."]} |
| Databáze: | OpenAIRE |
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