The images linked to this "Room" illustrate a variety of morphologies that can be displayed by Tertiary nannofossils. Select examples from three groups include forms referred to as discoasters, pentaliths, and holococcoliths. Discoasters
(e.g., Discoaster multiradiatus
are rosette or star-shaped species that may bear a spine or knob at the coccolith center and almost always show very low birefringence in polarized light. Pentaliths
(e.g., Micrantholithus angulosus)
are forms constructed of five similar calcite wedges. Great variation can be see amongst genera assigned to this group based on the shape of their wedges and the presence or absence of holes or other ornamentation. Holococcoliths
(e.g., Quinquerhabdus colossicus)
represent species that are constructed of small, uniformly sized calcite crystals, easily recognized but often difficult to classify into groups based on their dissimilar and seemingly unrelated morphologies. Nannofossils falling into other groups are also linked to images in the list, including
Coccolithus pelagicus,
a very common species which lives in the modern oceans, but first appears in the geologic record at the end of Cretaceous time.