Eiffellithus equibiramus


Classification: ntax_mesozoic -> Eiffellithales -> Eiffellithaceae -> Eiffellithus -> Eiffellithus equibiramus
Sister taxa: E. eximius, E. lindiensis ⟩⟨ E. gorkae, E. keio, E. parallelus, E. pospichalii, E. turriseiffelii ⟩⟨ E. collis, E. equibiramus, E. parvus ⟩⟨ E. monechiae, E. praestigium, E. vonsalisiae, E. hancockii, E. paragogus ⟩⟨ E. primus, E. striatus, E. windii, E. sp.

Distinguishing features: Medium, normally elliptical, eiffellithid; arms form symmetrical diagonal cross; each arm composed of two, subequal, rectangular, disjunct crystal-units with blunt distal tips divided by a prominent central suture.


Taxonomy:

Citation: Eiffellithus equibiramus Watkins & Bergen, 2003
Rank: Species
Taxonomic discussion: Eiffellithus turriseiffelii resembles a small morphotype of E. equibiramus in the symmetrical diagonal stem base. They can be differentiated by the morphology of the cross arms, which are rectangular and prominently bisected by a suture in E. equibiramus as opposed to distally tapering to a point in E. turriseiffelii. Eiffellithus parvus and E. equibiramus are of similar size range (5–7µm length), have symmetrical diagonal crosses, and have similar stratigraphic ranges. They are differentiated by the overall outline of the cross, which in plan view is a symmetrical diagonal cross in E. equibiramus but a compact rectangle in E. parvus. In addition, the crossbars in E. equibiramus are clearly divided into two sets of elements, while those of E. parvus act as single optical units.

Farinacci & Howe catalog pages: E. equibiramus *

Distinguishing features: Medium, normally elliptical, eiffellithid; arms form symmetrical diagonal cross; each arm composed of two, subequal, rectangular, disjunct crystal-units with blunt distal tips divided by a prominent central suture.


Morphology: This species has a normally to narrowly elliptical rim which is smooth to slightly serrate in outline. The outer rim is thin (<1µm) and composed of 35 to 50 steeply inclined elements. The inner rim is composed of blocky elements that are 1–1.5µm wide. The rims exhibit a first order white birefringence. A small (3 to 4µm) round hole characterizes the middle of the central area. A symmetrical, diagonal cross that supports a small hollow stem spans the central hole. The four arms of the cross are composed of two sub-parallel sets of elements, each of which is lath-shaped, yielding an arm outline that is distinctly rectangular in shape.Type section: Hole 1052E from Blake Nose (ODP Leg 171B)

Size: Length = 5.2–6.8µm (µ=6.0, s.d.=0.4, n=30) Width = 3.6–5.6µm (µ=4.4, s.d.=0.5, n=30) Eccentricity = 1.2–1.5 (µ=1.36, s.d.=0.1, n=30)

Most likely ancestor: Eiffellithus praestigium - at confidence level 3 (out of 5). Data source: Watkins & Bergen 2003.
Likely descendants: Eiffellithus parvus;

Search data:
TagsLITHS: murolith, elliptical, CA: ca_disjunct, plate, process, diagonal cross, closed, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
MetricsLith size: 5->7µm;
Data source notes: Watkins & Bergen 2003
The morphological data given here can be used on the advanced search page. See also these notes

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

Plot of occurrence data:

References:

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

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Eiffellithus equibiramus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 21-4-2021

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