Nannotax3 - ntax_mesozoic - Eiffellithus vonsalisiae

Distinguishing features: Medium to large eiffellithid with asymmetrical cross (20-35° from axis). Arms divided by central suture and with blunt to pointed tips.

Citation: Eiffellithus vonsalisiae Watkins & Bergen, 2003

Taxonomic discussion: This species differs from E. praestigium (its presumed ancestral form) by its somewhat larger size and by the greater divergence of the cross axes from the ellipse axes. The alignment of the cross arms at about 10–20° to the ellipse axes in E. praestigium results in a peculiar optical illusion such that when the ellipse is aligned with the polarizers, the cross axes appear subparallel to the ellipse axes. This is especially true of those arms near the minor ellipse axis. This is never true in E. vonsalisiae, as the cross arms always appear divergent from the ellipse axes regardless of the orientation of the coccolith.
This species differs from E. turriseiffelii by the clearly symmetrical, diagonal cross of the latter as opposed to the asymmetrical diagonal nature of the cross in E. vonsalisiae.

Distinguishing features: Medium to large eiffellithid with asymmetrical cross (20-35° from axis). Arms divided by central suture and with blunt to pointed tips.

Morphology: This species has a broadly to normally elliptical rim which is smooth to slightly serrate in outline. The outer rim is thin (approximately 1µm) and composed of 35 to 60 steeply inclined elements. The inner rim is composed of blocky elements that are approximately 2µm wide. The rims exhibit a first order white birefringence, although the largest specimens have a markedly yellow overtone. A small (approximately 3 by 2µm) elliptical hole characterizes the middle of the central area. The central hole is spanned by an asymmetrical, diagonal cross that might have supported a small hollow stem, although no central structure has been observed. The four arms of the cross lie obliquely to the major and minor axes of the ellipse, so that the axes of the cross and the axes of the ellipse are displaced by more than about 20° but less than about 35°. Each arm is composed to two sets of elements divided by a central suture that is usually only faintly evident. The arms taper distally and the tips of the arms are distinctly pointed. Numerous specimens were observed with a small but distinct offset of the cross arms nearest to the minor axis. [Watkins & Bergen 2003]

Size: Length = 6.4–9.0µm (µ=7.7, s.d.=0.8, n=30)
Width = 4.4–6.9µm (µ=5.7, s.d.=0.6, n=30)
Eccentricity = 1.3–1.5 (µ=1.4, s.d.=0.1, n=30)

Geological Range:
Last occurrence (top): within Early Cenomanian Substage (96.24-100.50Ma, top in Cenomanian stage). Data source: Watkins & Bergen 2003
First occurrence (base): within BC26 zone (103.27-104.06Ma, base in Albian stage). Data source: Watkins & Bergen 2003

References:

Hill, M. E. & Bralower, T. J. (1987). Early evolution, stratigraphy and taxonomy of Eiffellithus eximius and closely-related species. In, Stradner, H. , & Perch Nielsen, K, (eds) Proceedings of the INA Meeting, Vienna 1985. Abhandlungen der Geologischen Bundesanstalt. 39: 89-97. gs V O

Watkins, D. K. & Bergen, J. A. (2003). Late Albian adaptive radiation in the calcareous nannofossil genus Eiffelithus. Micropaleontology. 49(3): 231-252. gs

Tags	LITHS: murolith, elliptical, CA: cross-axial, ca_disjunct, plate, process, diagonal cross, closed, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
Metrics	Lith size: 6->9µm; Data source notes: Watkins & Bergen 2003

Eiffellithus vonsalisiae

References:

Comments (0)

Add Comment