Arthraster Forbes 1848
| Autor: | Gale, Andrew S. |
|---|---|
| Rok vydání: | 2020 |
| Předmět: | |
| ISSN: | 0269-3445 |
| DOI: | 10.5281/zenodo.4411406 |
| Popis: | Genus Arthraster Forbes, 1848 Type species. Arthraster dixoni Forbes, 1848 by original designation. Diagnosis. Long-armed, robust chaetasterids, in which the extraxial arm is constructed of 7 rows of ossicles, including 1 row of large radials, paired rows of supero- and inferomarginals and broad actinals. Arm ossicles with tall transverse crest; abactinals of disc small, round, with raised central region. Included species. In addition to the type species, A. cristatus Spencer, 1907. Remarks. Arthraster shares a number of similarities with Chaetaster, most obviously the long, subcylindrical arms and small disc, the fact that the abactinal, marginal and actinal ossicles are of similar size, and arranged in longitudinal rows. The extraxial ossicles of the arm (radials, marginal, actinals) of Arthraster (Fig. 1A, B) bear transverse ridges, similar to those present on the interradially positioned adradials and marginals of Chaetaster (Fig. 1D). The abactinal ossicles of the disc of Arthraster, revealed by preparation of the abactinal surface of the holotype of A. dixoni (Fig. 1B), are small and oval to rounded, as in Chaetaster. The differences between the genera include the smaller number of extraxial arm ossicle rows in Arthraster (7, rather than 13 in Chaetaster), and the presence of crested ridges on the arm and abactinal ossicles; the raised central regions are flat-topped in Chaetaster. 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 page 145, 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.","Spencer, W. K. (1907) A monograph of the British fossil Echinodermata from the Cretaceous formations. Vol. 2. The Asteroidea and Ophiuroidea. Monograph of the Palaeontographical Society, 4, 91 - 132. https: // doi. org / 10.1080 / 02693445.1907.12035532"]} |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|