Saccocoma
| Saccocoma | ||||||||||
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Saccocoma tenella in the Jura limestone, found in Eichstätt |
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| Temporal occurrence | ||||||||||
| Kimmeridgian to Tithonian ( Jurassic ) | ||||||||||
| 155 to 145 million years | ||||||||||
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Saccocoma | ||||||||||
| Agassiz , 1836 | ||||||||||
Saccocoma is an extinct genus of sea lilies (hair stars) from the echinodermic tribe(Echinodermata). There are currently four species belonging to this genus that were found exclusively inmarine depositsin Upper Jurassic .
description
The genus Saccocoma (Latin for "bag with hair") is a small, free-swimming sea lily with a total diameter (including arms) up to about 5 centimeters. The body is only about the size of a pea and shows the typical, five-rayed radial symmetry ( pentamerism ) of the higher echinoderms. From it go out five thin, paired, feathery arms, which, however, very soon divide, so that Saccocoma apparently has ten arms. The mouth was on the belly side (= underside) of the body. With the exception of the Solnhofen limestone limestone , where completely preserved specimens are often found in large numbers, only isolated skeletal elements have generally survived, which are obtained and examined using micropalaeontological methods.
Way of life
Only the type of the genus ( Saccocoma tenella (Goldfuss, 1831)) from the Solnhofen limestone limestone from Bavaria is known from complete specimens. Therefore, the following results mostly relate to this species.
In the upper Jura (about 150 million years ago) Saccocoma tenella populated the sea of the tubs near Eichstätt in Bavaria en masse . Later, the fine-grain limestone deposits of these tubs became the Solnhofen limestone .
With the constantly moving arms, the animal could only swim to a limited extent. The lashed parts of the arms started very close to the body and were probably too stiff to allow swimming movements. Presumably only the extreme ends of the arms were flexible enough to move the animal in the water column. Even a slight current drifted the floating sea lily. The arms were also used to filter food from the water and bring it to the mouth.
The free-swimming sea lilies were often eaten by ammonites . This is proven by the remains of Saccocoma in coprolites (fossil excrement) of ammonites.
history
Saccocoma tenella was scientifically examined in 1831 by the German doctor and paleontologist Georg August Goldfuss (1782–1848) and first validly described as Comatula tenella . In 1836 Agassiz proposed the genus Saccocoma for this species .
In the Middle Ages, the true nature of the free-swimming sea lilies was not yet recognized. At that time the fossils visible on Solnhofen slabs were sometimes mistaken for "the devil's work". At that time these deposits were interpreted as the legacies of the biblical flood .
In 1616 the Nuremberg pharmacist, botanist and publisher Basilius Besler (1561–1629) saw a spider in the Solnhofen sea lily Saccocoma . From this time on one spoke of the "Eichstätter spider stones". The doctor Johann Jakob Baier (1677–1735) made it public for the first time in 1730 that the plate limes in the Solnhofen and Eichstätt area were marine deposits . For the first time he interpreted the "Eichstätter Spiderstones" as starfish .
Systematics
Currently, four species are included in the genus Saccocoma , but only one species has been found in complete specimens:
- Saccocoma tenella (Goldfuss, 1831)
- Saccocoma quenstedti Sieverts-Doreck & Hess, 2002
- Saccocoma longipinna Hess, 2002
- Saccocoma vernioryi Manni & Nicosia, 1984
Other species that were previously assigned to the genus Saccocoma have now been assigned to other genera.
literature
- Michal Brodacki: Functional anatomy and mode of life of the latest Jurassic crinoid Saccocoma. Acta palaeontologica polonica, 51: 261-270, Warsaw 2006 ISSN 0567-7920
- Arno Hermann Müller: Textbook of Paleozoology Volume II Invertebrates Part 3 Arthropoda 2 - Hemichordata . 2nd edition, 748 pages, VEB Gustav Fischer Verlag Jena 1978.
