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 Globorotalia (Globorotalia) hirsuta praehirsuta Blow 1969 | ||||||
|
|
||||||
| Alternative name: | ||||||
| Diagnosis / Definition: | ||||||
|
Blow (1969): Description of holotype: Test fairly large, coiled in a low trochospire with about 10 chambers comprising the spire and with four chambers in the last whorl. The equatorial profile is slightly lobulate and the axial profile shows a plano convex outline. The peripheral margin is sub acute and bears a narrow but distinct carina. The spire opens fairly slowly at first but shows a marked degree of flare in the latest part of the coil. The earlier parts of the spire are tightly coiled and the chambers, as seen in dorsal aspect, are embracing and closely appressed except for the final chamber. The chambers as seen dorsally are much longer tangentially (anterior posterior) than radially broad and the dorsal intercameral sutures are strongly recurved. The dorsal intercameral sutures are weakly limbate in the later parts of the test. The ventral surface of the test does not have a distinct umbilical depression and there is no ventral concavity as in G. (G.) margaritae; the ventral surfaces of the chambers are only slightly inflated and the ventral intercameral sutures are only shallowly and broadly depressed, not distinctly incised. The dorsal surface of the test is convex and the dorsal spire protrudes above the level of the dorsal surfaces of the chambers of the last whorl. The aperture is an interiomarginal, umbilical extraumbilical slit like opening which extends only to about 2/3rds of the distance from the umbilicus to the periphery. The ventral surface of the final chamber is slightly inflated but there is no inflated lobe like extension into the umbilicus. Wall calcareous, radial hyaline [62a] with pustules mainly confined to the earlier parts of the test; ventrally the pustules are well scattered and separated. Maximum diameter of holotype 0.61 mm. |
||||||
| Discussion / Comments: | ||||||
|
Blow (1969): Remarks: G. (G.) hirsuta praehirsuta differs from G. (G.) hirsuta hirsuta in possessing a virtually flat ventral side to the test without a distinct umbilical pit like depression. G. (G.) hirsuta praehirsuta also lacks the more deeply incised ventral intercameral sutures and the more inflated ventral chamber surfaces (especially that of the last chamber) of G. (G.) hirsuta hirsuta. Thus in hirsuta (sensu stricto) the test is unequally biconvex but in praehirsuta the test is virtually plano convex. In G. (G.) hirsuta praehirsuta the earlier chambers, at least, are more tightly coiled, more embracing and more closely appressed (as seen in dorsal aspect especially) than in G. (G.) hirsuta hirsuta. The dorsal intercameral sutures of G. (G.) hirsuta praehirsuta are more strongly recurved and there is a characteristic dorso peripheral part of the chambers which appears to be strongly directed in a posterior direction. The aperture of praehirsuta is more laterally restricted than in hirsuta (sensu stricto). G. (G.) hirsuta praehirsuta differs from G. (G.) margaritae in showing no typically developed ventral concavity, for in margaritae the test, in axial profile, normally appears concavo convex. Even when this ventral concavity is absent in some specimens of margaritae, there is no significant inflation of the ventral chamber surfaces including the final chamber. The spire of G. (G.) margaritae is more tightly coiled than in G. (G.) hirsuta praehirsuta and the former taxon does not show the distinct flare of the spire as seen in the later parts of the test of praehirsuta The distinction between hirsuta (sensu stricto) and praehirsuta seems to be best made in terms of the absence or presence of a distinct umbilical pit, whilst the distinction between margaritae and praehirsuta is best made in terms of the more or less sudden change to a more open coiling mode seen in the later parts of the test of specimens referable to G. (G.) hirsuta praehirsuta. Additionally, the distinction between margaritae and praehirsuta can be made in terms of the ventral concavity of the former taxon and the essentially planoconvex test of the latter taxon. Finally, the consistently tighter coiling at all stages of ontogeny in G. (G.) margaritae is expressed in the dorsal appearance of the last few chambers of the spire which are much longer tangentially than broad radially as compared to the corresponding chambers of G. (G.) hirsuta praehirsuta Essentially, the evolution of G. (G.) hirsuta hirsuta from G. (G.) margaritae via G. (G.) hirsuta praehirsuta is accompanied by a gradual increasing laxity of the spire which is eventually shown in the development of a small but open umbilical depression in hirsuta hirsuta. The chambers, in dorsal aspect, become less closely appressed, less embracing and better separated one from the other in the development of the phylogenetically more advanced forms of the lineage. In axial profile, the test gradually becomes more tumid and there is the development of a convex ventral surface in G. (G.) hirsuta hirsuta as compared to the concavo convex and plano convex tests of the earlier forms of the lineage. There is little development in the relative strength of the carina but there is a gradual increase in the degree of both ventral and dorsal pustulation and an overall increase of average test size for a given stage of ontogeny. Stratigraphical Range: G. (G.) hirsuta praehirsuta develops from G. (G.) margaritae within the middle parts of Zone N. 18 but the two forms co exist for much of the succeeding later parts of Zone N.i8 and Zone N.19. G. (G.) hirsuta praehirsuta gives rise to G. (G.) hirsuta hirsuta within the earlier parts of Zone N.22. The holotype of G. (G.) hirsuta Praehirsuta was obtained from sample By. 61 collected from a section at Anzio, Italy, by D. D. BAYLISS; the horizon is referable to the earliest part of Zone N.19. |
||||||
| Synonym list: | ||||||
| Blow (1969): 1969 Globorotalia (Globorotalia) hirsuta praehirsuta Blow. - Blow : p.400 pl. 43, figs. 3-7
|
||||||
| 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) |
||||||