RANGES
AND AGES
The ranges and ages of 150
species of Radiolaria are summarized in this section in three ways.
- We have prepared three
graphic range charts, one for the low-latitude Neogene (Table
1), one for the low-latitude Paleogene (Table
2), and one for the middle-latitude Neogene (Table
3). Species are arranged in order of morphotypic last appearances.
The letter "m" at either end of a range denotes a morphotypic
first or last appearance; the letter "e" denotes an evolutionary
transition.
- For the middle Miocene
to Holocene we have prepared a chart of reported low-latitude absolute ages
(Table 4). "Tm"
denotes a morphotypic last appearance, "Bm" denotes a morphotypic
first appearance, and an arrow indicates an evolutionary transition. Ages
that are shaded were considered by the original authors to be unreliable.
The absolute ages used are in accordance with the chronostratigraphy of
Berggren et al. (1985). For further information see the original reports.
- The radiolarian events
shown on the zonal description sheets have been summarized in two tables (Table
5. Low latitude radiolarian events and Table
6. Middle latitude radiolarian events). A dash in front of the event
(or group of events) separates it in time from the event(s) above and below.
Events separated by semicolons are approximately synchronous. The first and
last appearance of a taxon is indicated as "Bm" (earliest
morphotypic appearance) and "Tm" (latest morphotypic appearance)
and an evolutionary transition is shown with an arrow. "Morphotypic"
and "evolutionary" limits, as applied in the zonal definitions,
are explained in Riedel and Sanfilippo (1971, p. 1530).
