H. recta group of Young (1998)
Distinctive group of Late Oligocene to Mid Miocene Helicosphaera species, with flange terminating abruptly rather than expanding into a wing. Blanket confined to central area, so flange is dark is dark in cross-polars. Central area openings usually show inverse orientation (i.e. they point toward the flange termination). Bar conjunct with rim.
| Drawing | Outline description |
Range |
| |
H. recta - large pores separated by horizontal bar | NP24-NN1 |
| |
H. obliqua - tear-drop shaped with narrow, distinctly oblique, openings |
NP24-NN6 |
| |
H. perch-nielseniae - more rectangular shape than obliqua |
NP23-NN6 |
|
|
H. orientalis - small, quadrate, with tow large openings |
NN6-11 |
Neogene: H. recta group