Taxonomic notes on hystrichospheres and acritarchs (dedikált példány) [antikvár]

TAXONOMIC NOTES ON HYSTRICHOSPHERES AND ACRITARCHSWILLIAM ANTONY SWITHIN SARJEANT Department of Geology, The University, Nottingham, EnglandIn course of preparation of an annotated bibliography of fossil dinoflagellates, acritarchs and related micro-organisms (Downie and Sarjeant, in press), a number of nomenclatural problems were encountered. These are discussed below. The principles of classification expressed by Downie, Evitt, and Sarjeant (1963) are here followed: accordingly, the problems are considered under the provisions of the "International Code of Botanical Nomenclature" as adopted by the Ninth International Botanical Congress, Montreal, August 1959.i. The genus Spiniferites Mantell 1850. Hystricho-spheres and acritarchs were first described fossil by Christian G. Ehrenberg in 1838. Wrongly considering the shells to be siliceous, Ehrenberg interpreted them as zygospores of Desmidiaceae and attributed them to a number of species within the genus Xanthidium.In 1845, the great paleontologist Gideon Mantel! subjected representatives of these fossil micro-organisms to a thorough examination and concluded:A careful examination of both recent and fossil Xanthidia leads me to doubt whether there is any analogy between the organisms in our flints and their supposed living types. The fossil forms have the body more decidedly spherical or globular, their spines are more strictly tubular and differently arranged; and they never exhibit that reniform or constricted character so constant in the recent Xanthidia, nor do they present any indication of spontaneous fissuration. The fossils are supposed by Ehrenberg to have been originally siliceous Uke the shields of other infusoria, but I do not know of any proof that has been obtained of this inference. On the contrary, so many examples occur in which the tubular arms are bent, contorted, and contracted and shrivelled in the middle as to convey the idea of a flexible, rather than a brittle, envelope. A crushed or torn specimen very lately found by my son, exhibits an appearance much at variance with the supposition that the original was composed of silex or of any other material that had a conchoidal fracture. I think in the present state of knowledge it will be proper, notwithstanding the highauthority with which we differ, to consider the so-called Xanthidia of the chalk as distinct from the recent organisms after which they have been named; in fact, as a genus of marine infusoria, should they not hereafter prove to be the gemmules of polyparia or the spores of marine plants.Having thus convincingly demonstrated the distinctive character of the fossils, the next logical step was for Mantell to propose a new name for them. This step was taken in 1850, in a footnote in his "Pictorial Atlas of Fossil Remains" (p. 191):" It would be convenient to distinguish these fossils by another name, and thus avoid perpetuation of the error; I would propose that of Spiniferites, in allusion to the numerous spines with which all the species are beset."Mantell did not immediatelly attribute any species to the genus, although it might be considered that a transfer of all fossil species to Spiniferites was implied. The omission was, however, rectified in 1854, in the entirely rewritten second edition of his "Medals of Creation." Three species are here figured and attributed to Spiniferites5. palmatus (fig. 79); 5. ramosus (fig. 77 nos. 4 and 6); and S. reginaldi (fig. 77 no. 5 and fig. 78). The same three species are also figured in the revised seventh edition of his "Wonders of Geology" (1857).The first of these is stated by Mantell to have been discovered by the Rev. J. B. Reade and corresponds in its morphology to a form figured as Xanthidium tuUferum (Reade, 1839, pi. 9 fig. 9). It was differentiated as a subspecies by H. H. White (1842); in White's text (p. 39) it is designated "X. tuhiferum recurvatum or palmaforme," in the plate caption (p. 40) as "X. tubiferum palmatum." Bronn (1848, p. 1375) lists this species as "Xanthidium palmatum"; Mantell thus follows Bronn's choice of name. Under Article 34 of the "International Code of Botanical Nomenclature," alternative names are acceptable if published on or before 1st Jan. 1953; the Code gives no direct guidance on which alternative