Saccocoma
Saccocoma tenella in the Jurassic Solnhofen, Eichstätt locality
- Germany, ( Solnhofen limestone )
Saccocoma is an extinct genus of sea lilies ( crinoids ) from the tribe of echinoderms ( Echinodermata ). Currently, four species are placed in this genus that were found exclusively in Upper Jurassic marine deposits.
Description
The genus Saccocoma is a small, free-swimming crinoid with a total diameter (including arms ) up to about 5 centimeters. The body is only pea-sized and shows the typical, five-pointed radial symmetry ( Pentamerie ) the higher echinoderms. From him go five thin, each paired feathery arms, but which share very soon, so that Saccocoma apparently has ten arms. The mouth was located on the ventral side ( = bottom ) of the body. With the exception of the Solnhofen limestone, where completely preserved specimens are often found en masse, only isolated skeletal elements have been preserved usually obtained with micropaleontological methods and investigated.
Way of life
Only the type species of the genus ( Saccocoma tenella ( Goldfuss, 1831) ) from the Solnhofen limestones of Bavaria is known from complete specimens. Therefore, the following results refer mainly to this Article
In the upper Jurassic period ( about 150 million years ago) Saccocoma tenella has massively populated the sea of vats at Eichstätt in Bavaria. Later, the Solnhofen limestone from the fine-grained limestone deposits of these tubs.
With the ever moving arms the animal could swim only limited. The ciliated parts of the arms started very close to the body and were probably too stiff to allow swimming movements. Probably only the extreme ends of the arms were flexible enough to move the animal in the water column. Even a slight flow verdriftete the floating crinoid. The arms also served to filter food from the water and feed the mouth.
The free-swimming crinoids were often eaten by ammonites. This is proved by the remains of Saccocoma in coprolites (fossil feces ) of ammonites.
History
Saccocoma tenella was built in 1831 by the German physician and paleontologist Georg August Goldfuss ( 1782-1848 ) scientifically studied and described as Comatula tenella first valid. 1836 Agassiz proposed for this type of the genus Saccocoma ago.
In the Middle Ages had not yet recognized the true nature of free-swimming crinoids. At the time, visible on Solnhofen fossils have been held partly for " devil's work ". We interpreted these deposits at the time as legacies of the Biblical Flood.
1616 saw the Nuremberg apothecary, botanist and publisher Basilius Besler ( 1561-1629 ) in the Solnhofen crinoid Saccocoma a spider. From this time there was talk of the " Eichstätt spiders stones ". That it was marine deposits in Solnhofen Solnhofen and Eichstätt in space, made in 1730 for the first time, the physician Johann Jacob Baier ( 1677-1735 ) Republic. He interpreted the " Eichstätt spiders stones " for the first time as a starfish.
System
Currently four species are assigned to the genus Saccocoma, of which only one species was found but in complete specimens:
- Saccocoma quenstedti Sieverts Doreck & Hess, 2002
- Saccocoma longipinna Hess, 2002
- Saccocoma vernioryi Manni & Nicosia, 1984
Other species that were formerly assigned to the genus Saccocoma, other genera have been assigned now.