Animals – not plants
Despite their common name ‘sea lilies’, crinoids are animals but not plants, although they look like a flower (Fig. 1). They are related to the sea urchins, sea cucumbers and starfish, groups that are unified as echinoderms (see, for example, Broadhead and Waters, 1980). Crinoids consist of a “root”, a stem built of many disc-shaped elements (columnals) and a crown.
The name “sea lily rock” is often associated with the basal plates of fossilised crowns that resemble a lily flower and were collected as “Lilienstein” (“lily rock”) by gentlemen collectors in Central Europe, particularly in the nineteenth century (Fig. 2). In fact, crinoids were encountered for many hundred years and thus were already known by the famous Swiss and German scientists (respectively), Conrad Gessner and Georgius Agricola, in the sixteenth century. However, these early geoscientists only found the fossils, since living crinoids can only be found in the deep sea and were not known by the scientific community before the eighteenth century. This is the reason why the isolated stem elements called columnals occur in millions of specimens in the German Muschelkalk (Middle Triassic) were mystically called “Boniface pennies” or “Witch money”, before they were recognised as parts of crinoids.