Bau und Funktion der Scyphocrinites ‐Lobolithen

Abstract

In Silurian loboliths (Camarocrinus, bladder‐like root of Scyphocrinites) two morphogenetic types are recognized: an older and previously almost unknown ‘cirrus lobolith’, and the familiar cosmopolitan ‘plate lobolith’. Their functional interpretation as buoys, for the latter type so far mainly based on its unusual form and mode of occurrence, is supported by (1) approximation to the paradigm, (2) buoyancy calculations of the gas contents, and (3) physical‐technical considerations based on the optimation involved in the phylogenetic transition from cirrus to plate loboliths. Die lange Zeit umstrittene Funktion der Lobolithen (hohle, kugelförmige Wurzelregion von Scyphocrinites) wird an zwei verschiedenen, aber phylogenetisch nahe verwandten Bautypen, dem bisher praktisch unbekannten, stratigraphisch älteren ‘Cirren‐Lobolithen’ und dem schon mehrfach bearbeiteten ‘Platten‐Lobolithen’, untersucht. Beide hatten mit Sicherheit Ballon‐Funktion; denn(l) entspricht ihr Bau dem Paradigma dieser Funktion, (2) besaßen beide Lobolithen auf Grund ihrer Gasfüllung eine mehr als ausreichende Tragkraft, (3) entspricht der Übergang von Cirren‐ zu Platten‐Lobolithen einer weiteren Optimierung der Ballon‐Funktion.

Discovery of plate‐type scyphocrinoid loboliths in the uppermost Pr̆ídolían–lowermost Lochkovian Upper Setul limestone of Peninsular Malaysia

“…Ubaghs (1978a) favoured the last hypothesis, which is consistent with the morphological characteristics of the bulbs, their worldwide distribution, approximation to a mechanical model (paradigm) for their function and calculation of their buoyancy as attachments to living crinoids which floated on the surface or at shallow depths in widespread ancient seas as proposed by Haude (1972).…”

“…Loboliths are the bladder-like roots of a floating crinoid named Scyphocrinites (Haude 1972). Haude (1992) separated the stratigraphically older, more primitive cirrus lobolith (Pȓídolían only) that belongs to Scyphocrinites and Carolicrinus from the younger plate lobolith (uppermost Pȓídolían-lowermost Lochkovian) belonging to Marhoumacrinus and Camarocrinus (re-established as a valid genus).…”

“…The initial difficulty in identifying the large globular fossils in the Memplam Bay limestone bed is understandable, considering that bulbous holdfasts of scyphocrinoids had been variously interpreted (see Ubaghs 1978a, p. T93) as bodies of organisms belonging to an independent class of echinoderms (Barrande 1887), cystoids (Sun and Szetu 1947), genital sacs (Jaekel 1904), brood-pouches or receptacles (Haeckel 1896), pathologic cysts induced by myzostomids (Haeckel 1896;Ehrenberg 1926), inflated roots serving for permanent or temporary settlement on muddy bottoms (Springer 1917) and floating organs (Hall 1879;Schuchert 1904;Yakovlev 1953;Stukalina 1967;Haude 1972). Ubaghs (1978a) favoured the last hypothesis, which is consistent with the morphological characteristics of the bulbs, their worldwide distribution, approximation to a mechanical model (paradigm) for their function and calculation of their buoyancy as attachments to living crinoids which floated on the surface or at shallow depths in widespread ancient seas as proposed by Haude (1972).…”

Treatise Online, no. 16, Part T, Revised, Volume 1, Chapter 19: Paleoecology of pelagic crinoids

“…1) and the lobed plate lobolith with a few large chambers, a curved, bilaterally symmetric root trunk, a simplified wall structure, and a characteristic collar (Fig. 2) (Haude, 1972(Haude, , 1992. The smallest plate lobolith known has a diameter of 5 mm (Hess, 1999a, p. 99), while the largest cirrus lobolith reaches a diameter of more than 30 cm (H. Hess, personal observation, 2000).…”

“…The crinoid's generation of gas to fill the bulb has so far not been explained in a satisfactory way. Haude (1972) assumed that gas accumulated from the surrounding water by diffusion, as in floating algae, but failed to define the mechanism. In a later paper, Haude (1998) suggested that larval or juvenile scyphocrinitids were attached by their root cirri to some plant material (algae) drifting at the air-water interface.…”