Taxon Concept provided by
| Taxon Concept provided by
|
|
| Home | Search | |
| TaxonConcept data set details: |
||||||
| Back to Search | ||||||
| Anonymous: Unedited TaxonConcept data | ||||||
| Notice: This catalogue page may contain unedited data.
| ||||||
Subspecies Candeina nitida praenitida Blow 1969 | ||||||
|
|
||||||
| Diagnosis / Definition: | ||||||
|
Blow (1969): Description of holotype: The highly trochospirally coiled test consists of about ii chambers arranged so that there are three chambers in the last whorl, four chambers in the penultimate whorl and three chambers (at least) in the initial coil about the proloculus; three distinct whorls of chambers are therefore present. The chambers are subglobular, inflated and only comparatively slightly embracing. No primary aperture visible externally, but sutural apertures present in the spiral suture which circumscribes the 3 chambers of the final whorl. Sutural apertures present in the dorso ventrally directed intercameral suture between the ultimate and penultimate chambers. Probably only two small sutural apertures also present in the intercameral suture of the penultimate and antepenultimate chambers. No sutural apertures present in any of the intercameral sutures prior to that of the antepenultimate chamber. The very small sutural apertures present in the spiral suture prior to that part circumscribing the last three chambers of the test appear to be entirely at the confluence of the intercameral and spiral sutures. These earlier dorsal spiral apertures are very few in number and probably only two are present prior to that part of the spiral suture circumscribing the final whorl. The wall is calcareous, radial hyaline [62a], thin and delicate, very finely perforate but with the pores widely scattered. The wall bears very small pustules and the pores open between them. Maximum diameter of holotype 0.42 mm. |
||||||
| Discussion / Comments: | ||||||
|
Blow (1969): Remarks: Candeina nitida praenitida is separated from Candeina nitida nitida in lacking small supplementary apertures in the intercameral sutures prior to the suture between penultimate and antepenultimate chambers. In other words, the subspecies praenitida is distinguished from nitida (s.s.) in possessing intercameral sutural apertures confined to the last two chambers only of the final whorl. Pl. 22, figures 5, 7, 8, show the morphology of a paratype of praenitida; this form still possesses a distinct slit like primary aperture and sutural apertures which are confined to the intercameral sutures of the ultimate, penultimate and antepenultimate chambers only. This paratype has dorsal spiral sutural apertures present only at the confluence of the intercameral and spiral sutures except for a very few apertures present in the spiral suture circumscribing the last two chambers. Accordingly, this form may be distinguished from Globigerinoides Parkerae at generic, specific and subspecific levels by means of the few sutural apertures present only in the intercameral suture of the ultimate, penultimate and antepenultimate chambers. Usually C. nitida praenitida has only three clear whorls of chambers but C. nitida nitida often has four whorls of chambers and as many as 6 whorls have been seen in this taxon. Again C. nitida praenitida seldom shows any great proliferation of the small apertures in the dorsal spiral suture prior to that part circumscribing the last whorl. However, in C. nitida nitida a considerable multiplicity of apertures occurs throughout very nearly all of the spiral suture. Similarly, in C. nitida nitida, the intercameral sutural apertures occur in most of these sutures even in the sutures between the very early chambers of the antepenultimate whorl. As emphasized above, the arbitrary distinction between C. nitida nitida and C. nitida praenitida is made in terms of the presence of intercameral sutural apertures in the sutures of chambers prior to that of the antepenultimate chamber. The evolution of C. nitida nitida from Globigerinoides Parkerae via C. nitida praenitida is seen to be the successive palingenetic development of the sutural apertures, both spiral and intercameral, into the successively earlier parts of the test combined with a proliferation of the apertures. The loss of primary aperture occurs within the continued morphogenetic development of Candeina nitida praenitida It is for this reason that the writer was forced into the position of disregarding the previously presumed generic importance of the primary aperture, since the presence or absence of the primary aperture seems to be unrelated to any other morphological change in forms which can be united in the taxon praenitida On the other hand, the presence or absence of intercameral sutural apertures provides a readily distinguishable biocharacter both for the generic distinction of Candeina from Globigerinoides and for the subspecific distinction of praenitida from nitida (s.s.). Stratigraphical Range: C. nitida praenitida first develops from Globigerinoides parkerae in the later parts of Zone N. 15 and the evolution forms a useful datum for the recognition of the proximity of the Zone N.16/Zone N.15 boundary. C. nitida praenitida gives rise to C. nitida nitida within Zone N. 17. From this it will be seen that the genus Candeina occurs from virtually the base of the Tortonian and thus is confined to the interval of the late Miocene to Recent. The holotype of C. nitida praenitida was obtained from sample ER.307, lower part of the Bowden formation, Jamaica; Zone N.16 (early part). |
||||||
| Synonym list: | ||||||
| Blow (1969): 1969 Candeina nitida praenitida Blow. - Blow : p.385 pl.22, figs.5-8
|
||||||
| References: | ||||||
Blow,W.H. (1969): |
||||||
| Anonymous: Unedited TaxonConcept data | ||||||
 This work is licensed under a Creative Commons Attribution 2.5 License. | ||||||
| Back to Search | ||||||
|
Taxon relations
Ranking (experimental) |
||||||