|Anthocyrtium hispidum Haeckel|
Radiolarians are unicellulars, wee little things with a diameter of 0.1–0.2 mm.
They produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm.Their beautifully elaborate mineral skeletons are usually made of silica. We find radiolaria as zooplankton throughout the ocean and their skeletal remains make up a large part of the cover of the ocean floor as siliceous ooze.
Due to their rapid turnover of species, they represent an important diagnostic fossil from the Cambrian onwards. Because they occur in continuous and well-dated sequences of rock, they act like a yardstick, helping geologists accurately date rock from around the globe.
In the Upper Triassic rocks, which predate the Triassic / Jurassic Mass Extinction event by about 10 million years, radiolarians are preserved in hundreds of forms. Just above them, in the early Jurassic rock layers laid down about the time of the great die-offs, only a fraction of the previous number of forms are represented. The more recent Jurassic rock shows a rebound of radiolarian diversity, though of course, in different forms, a diversity which continues to flourish and expand in today’s oceans.
Photo: Anthocyrtium hispidum Haeckel, magnification: 400x, bright field (negative image), stacked image Fundort / Site: Barbados Alter / Age: approx. 32-35 million years (late Eocene - early Oligocene) Präparation / Preparation: Andreas Drews