Devonaster Devonaster was a Devonian starfish. It possessed a large central disc and broad arms. See also Starfish Diatoms Diatoms are photosynthetic single-celled algae that flourish in many aquatic environments. They are common in modern oceans, where they are an important link in the food chain. Some are free-floating, while others are attached to a substrate.
Diatoms have a two-part cell wall made of silica.
They have been found in sediments from the Early Cretaceous to recent times and are useful in many palaeoecological studies. Dicranograptus Dicranograptus was a graptolite with a single stalk that branched into a double stalk. Two rows of cups were attached to the single stalk, but the split stalks each bore only a single cup row. See also Graptolites Dictyonema Dictyonema was a dendroid graptolite, one that formed dense, many-stalked colonies. Individual animals lived in cups attached to the branches.