Isocrystallithus compactus
Set number: 2049
-
1
-
2
-
3
-
4
-
5
-
6
-
7
-
8
-
9
-
10
-
11
-
12
-
13
-
14
-
15
-
16
-
17
-
18
-
19
-
20
-
21
-
22
-
23
-
24
-
25
-
26
-
27
-
28
10µm
Isocrystallithus compactus Verbeek,1976
Species of Isocrystallithus have a parallel-sided, hollow distal process with a plug at its termination. In the side view, Isocrystallithus compactus exhibits parallel extinction with length-slow (+) elongation. The elliptical base features a rim and a small central opening, surrounded by six struts. In the plan view, Isocrystallithus compactus displays parallel extinction but length-fast (-) elongation.
Both Isocrystallithus compactus and Sarmania partitum exhibit parallel extinction, but differ in their distal processes and base morphology. In Isocrystallithus compactus, the distal process is hollow, whereas in Sarmania partitum, it is solid and comprises four ridges. The base of Sarmania partitum, as viewed in the plan, features a rim and two pores separated by the base of the solid distal process, which appears as a diagonal cross in the plan view. In comparison, the base of Isocrystallithus compactus in plan view has a narrow rim and a central opening surrounded by struts.
The side view of the base in Sarmania partitum reveals two levels and the ridges of the distal process.
Verbeek, J. W. 1976. Upper Cretaceous calcareous nannoplankton from Ballon and Théligny in the type area of the Cenomanian stage (Sarthe, France). Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen. B79: 69-82.
Varol, O. 2025a. A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222
Holotype
Isocrystallithus compactus
Verbeek, 1976
Early Cenomanian
Theligny, Sarthe, France.