Jens Lehmann (Germany)
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.
Millions of fossils
The most common crinoid fossil in Europe is unequivocally Encrinus liliiformis, first described by Lamarck in 1816. This crinoid grew in masses on build-ups, forming reef-like structures in association with other benthic organisms, like oysters and brachiopods, in the German Muschelkalk. Probably more than 99% of its fossils are formed only by the columnals. There are columnals that are larger in diameter than the “regular “ones (Fig. 2). These elements are called nodals and, in crinoids, they may have cirri branching from them. Both types of columnals are a dominant component of a famous building rock in southern Germany, the “Crailsheimer Trochitenkalk”.
However, crowns, or even crowns associated with a segment of the stem, are extremely rare in comparison. In many cases, the crowns are closed. This means the single arms, forming the upper part of the crown, are closely attached to each other (Fig. 1). This prevents us from having a look at the organs that filter the organic detritus for the crinoid from which it feeds: the pinnules (Fig. 3). Fig. 3 shows a specimen with a crown and a segment of the stem from the Muschelkalk of Northern Germany is presented that beautifully shows the pinnules in between the arms (Fig. 3). In this case, the preservation in mudstone made it possible, not only to preserve these fine details, but also to prepare these from the rock. In contrast, preparation of Muschelkalk fossils is usually not only challenging but often impossible, strongly depending on the mode of preservation.
The crinoid species, Encrinus liliiformis, was voted “Fossil of the Year” for the year 2019 by the German Palaeontological Society (Paläontologische Gesellschaft), due to its ease of recognition, its scientific-historical significance and its abundance. This is another time the society voted for a fossil that is accessible for everybody as at least single pieces of stem, but that also produced many brilliant museums specimens of more or less complete specimens that are unique, with a high monetary value.
This species is also among the relatively few crinoid species that are important as index fossils in the Phanerozoic, being eponymous for the Encrinus liliiformis biozone (Hagdorn, 1999b), dated as latest Anisian or earliest Ladinian of the Middle Triassic (Franz et al., 2015). More comprehensive accounts of this species can be found in the works of the Muschelkalk specialist, Hans Hagdorn (1996, 1999a, 2011).
To summarise, this fossil has made a multiple career for itself: as an organism in the Muschelkalk Sea, forming even reef-like structures; its remains made a career as a building rock; and finally, it became honoured as “Fossil of the Year” by the German Palaeontological Society.
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Franz, M., S. I. Kaiser, J. Fischer, C. Heunisch, E. Kustatscher, F. W. Luppold, U. Berner & H. G. Röhling 2015. Eustatic and climatic control on the Upper Muschelkalk Sea (late Anisian/Ladinian) in the Central European Basin. Global and Planetary Change 135: 1-27.
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Hagdorn, H. 1999a. Seelilien und Crinoidenkalke des Muschelkalks. In N. Hauschke & V. Wilde (eds): 321-330, Dr. Friedrich Pfeil, Munich.
Hagdorn, H. 1999b. Triassic Muschelkalk of Central Europe. In H. Hess, W. I. Ausich, C. E. Brett & M. J. Simms (eds): 164-176, Cambridge University Press, Cambridge.
Hagdorn, H. 2011. The Triassic – Crucial period of post-Palaeozoic crinoid diversification. Swiss Journal of Palaeontology 130: 91-112.
Hagdorn, H. 2012. Eine berühmte Seelilie aus dem Muschelkalk. In T. Martin, W. Von Koenigswald, G. Radtke & J. Rust (eds): 100-101, Dr. Friedrich Pfeil, Munich.