Five groups are counted among Recent echinoderms, feather stars and sea lilies (Crinoidea), seastars (Asteroidea), brittle and basket stars (Ophiuroidea), sea urchins (Echinoidea) and sea cucumbers (Holothuroidea). Additional about 15 groups have gone extinct during the long history of evolution.
Echinoderm research in Sweden and at the Swedish Museum of Natural History has a long history. Sven Lovén studied sea urchins in the 19th century and Hjalmar Théel described a new genus of sea cucumbers. At the same time, A.W. Ljungman in Uppsala described over 70 species of brittle stars and a sea cucumber.
This tradition is continued today by Sabine Stöhr with research on the classification (taxonomy) and evolutionary history (systematics) of brittle stars.