| Home> Cenozoic> Miocene>
 

List species

Actinosphaera haackei (Dreyer, 1973)

Description - Add description

Cortical shell is ovate, commonly thick-walled, with
circular or subcircular pores irregularly scattered. Surface is rough
and is covered with lamellar crests irregularly ramified and free or
connected with each other to form a labyrinthine system. At one or
both poles the lamellar crests may develop exaggeratedly, constitu-
ting one or two opposite bunches of multilamellar spines. Three
types of inner skeleton have been recorded in this species (Plate 19,
Figures 6, 8, 9): (a) a simple skeleton consisting of a delicate
microsphere connected to the cortical shell by a number of
thread-like radial bars; (b) an intermediate skeleton (Figure 8), the
radial bars of which are bi- or trifurcate, and (c) a double-shelled
inner skeleton (Figure 9) where the microsphere is surrounded by a
delicate median spherical shell consisting of large, irregular meshes.

Dimensions: Transverse diameter of the cortical shell is 100 to
160μ; length of the cortical shell is 115 to 170μ; and diameter of
the microsphere is 15 to 20μ.

Remarks: Assignment of the Quaternary Mediterranean forms of
the illustrated type to this taxon is only a provisional solution. At
any rate this species, as it is here understood, possesses a high
polymorphism which is expressed in terms of: size of the cortical
shell, presence or absence of the polar bunches of spines, and in
their number, in the thickness of the cortical wall, and others. The
large shells, similar to that illustrated in Figure 9, seem generally to
be much thinner-walled, and much less ovate than the small ones.

Dumitrica 1973


Description

 

Images

 

Synonyms

 

References

 

Distribution

 

Discussion / Comments

 

Web links