Sea lilies and hair stars

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Sea lilies and hair stars
A recent, stalked sea lily in the caldera of a submarine volcano.

A recent , stalked sea lily in the caldera of a submarine volcano .

Temporal occurrence
Cambrian until today
513 to 0 million years
Locations
  • worldwide
Systematics
without rank: Tissue animals (Eumetazoa)
without rank: Bilateria
Over trunk : Neumünder (Deuterostomia)
Trunk : Echinoderms (Echinodermata)
Sub-stem : Pelmatozoa (Pelmatozoa)
Class : Sea lilies and hair stars
Scientific name
Crinoidea
Miller , 1821

Sea lilies and hair stars (Crinoidea from ancient Greek κρίνος, lily ') belong to the echinoderm tribe (Echinodermata) and are related to sea ​​urchins and starfish . In the system, the sea lilies and hair stars with around 620 species are compared to all other today's echinoderms (Eleutherozoa) as a sister group Pelmatozoa .

The system is uncertain. All today's sea lilies and hair stars are counted in the subclass Articulata. This is divided into two to five orders, depending on the source. A distinction is often made between cirrus-bearing sea lilies (Isocrinida) and cirrus-less sea lilies (Millericrinida). There is only agreement that the hair stars (Comatulida), which do not live sessilically and which today constitute the bulk of the surviving species, form their own order.

There are only about 25 stalked, sessile species that mostly live in the deep sea up to 6000 meters and with a maximum height of half a meter remain much smaller than their extinct relatives.

features

Anatomy of a crinoid

Most species of sea lily are attached to the sea ​​floor with a stem and at the top they have a cup built with plate wreaths, which protects the soft body of the animal. From the edge of the cup, five arms branch out (five-pointed symmetry). Further division of the arm bases results in 10 or 20-arm crowns. With the help of feather-like arm attachments (pinnulae), plankton is filtered and transported into the mouth . The top of the chalice is called a tegmen.

All sea lilies and feather stars feed by filtering edible particles with their feathery arms from the water flowing past.

Systematics

The sea lilies and hair stars are currently divided into five subclasses:

Fossil crinoids

Fossil sea lily crowns

The sea lilies have appeared since the Ordovician and, with the exception of the hairy stars (Comatulida), only live today in the deep sea area south of the equator ("living fossils").

During the Middle Triassic ( Muschelkalk ), the sea lily appeared in large numbers in the Central European flat sea area (Germanic Basin) that it became rock-forming ( trochitic limestone ).

In addition to the fixed forms, there are also free-swimming sea lilies. During the Black Jura (Lias) there were e.g. B. due to the hostile conditions (lack of oxygen) in deeper sea areas only free swimming sea lilies. They lived either in colonies, attached to driftwood or as solitary animals.

Another group, the buoy sea lilies (scyphocrinites), was widespread in the Upper Silurian and Lower Devonian (around 400 million years ago). The most beautiful finds of Scyphocrinites elegans come from Morocco near Erfoud . In addition to the goblets, there were spherical structures (lobolites) with a diameter of 10 cm and more, originally gas-filled “buoys” on which the stems hung with the goblets facing down. The buoy sea lilies of Morocco are among the most remarkable developments of sea lilies at all. How the buoys developed from originally small roots is still the subject of research.

The largest colony of sea lilies that has ever been found and prepared in the world is exhibited in the Urwelt Museum Hauff in Holzmaden . It is 18 m × 6 m in size. It grew on a twelve meter long driftwood and comes from the Black Jura (Lower Toarcian ) from Holzmaden.

Locations

Stalk member of Holocrinus dubius on the surface of the upper limestone bank of the lower shell limestone
Part of a stem of Seirocrinus  sp. from the Lower Jura , Lower Pliensbachian

Fossilization of sea lilies can be found in the peripheral areas of the Elm ridge in the soft Elm limestone , particularly pronounced in Erkerode (in the middle of the ridge, the harder, lower limestone came to light through erosion). Above all, the species Encrinus liliiformis was found with its compact, robust crown. In recent times, entire communities of mussel and sea lilies have been found in the Elm, which represented narrow, reef-like structures. The Klages collection ( Königslutter ) has several hundred copies, including a large stone slab with 16 sea lily crowns and stems up to 70 cm in length.

One of the classic find areas of completely preserved Encrinus liliiformis is the area around Crailsheim. The trochite banks are particularly powerful here and consist, in layers, almost entirely of trochites of this type. Specimens from the Crailsheim area can be found in many museums.

Popular beliefs and customs

Trochitic limestone, found near Erkerode on the western edge of the Elm

Trochites , the fossilized limbs of the sea lilies that formed from the calcareous crinoid skeletons, are particularly common . The trochitic limestone was processed into necklaces as early as the Stone Age . This was obvious because the tube-like trochites sheathed the animals' nerve canals. In the pre-Christian times was u. a. In Central Europe the former nerve canal was drilled free in fossil trochites and the individual links were threaded into a necklace. With the Teutons , the trochites were considered a sign of bravery. This meaning remained for a long time. In the course of Christianization, the population had to give up their trochites (Bonifatius pfennige, Wichtelpfennige or witch money). As late as 1714 , trochites were found in pharmacies as a remedy for various diseases such as epilepsy , melancholy , poisonous animals, nosebleeds, dizziness and kidney problems. They were also intended to promote bravery, facilitate the afterbirth and give the owner a long life.

Certain fossils of crinoids as well as those of many-armed brittle stars (Ophiuroidea) were in a past when these fossilized forms their viewers even terror could excite, as " Medusa called". The sea-dwelling Medusa from Greek mythology turned people to stone by the mere sight of her head covered by snake hair.

literature

  • Janina F. Dynowski, James H. Nebelsick, Adrian Klein and Anita Roth-Nebelsick: Computational Fluid Dynamics Analysis of the Fossil Crinoid Encrinus liliiformis (Echinodermata: Crinoidea). In: PLoS ONE. Volume 11 (5): e0156408, doi: 10.1371 / journal.pone.0156408
  • Hans Hagdorn : Triassic: the crucial period of post-Palaeozoic crinoid diversification . In: Swiss J Palaeontol., 130, 2011, pp. 91-112
  • Hans Hess, William I. Ausich, Carlton E. Brett, and Michael J. Simms: Fossil Crinoids . Cambridge University Press, 2003, ISBN 0-521-52440-7

Web links

Commons : Sea Lilies and Feather Stars  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Crinoid Morphology. University of California Museum of Paleontology website (accessed February 5, 2016)
  2. ↑ Helmut Hölder : Natural history of life . 2nd Edition. Springer-Verlag, Berlin, Heidelberg, New York 1989, pp. 153 .