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:
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;
Tags | LITHS: murolith, elliptical, CA: ca_disjunct, plate, process, diagonal cross, closed, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent, |
Metrics | Lith size: 5->7µm; Data source notes: Watkins & Bergen 2003 |
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:
Watkins, D. K. & Bergen, J. A. (2003). Late Albian adaptive radiation in the calcareous nannofossil genus Eiffelithus. Micropaleontology. 49(3): 231-252. gsReferences:
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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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