Friday, 17 January 2014

A hypercalcified Chaetetid Demosponge from the Late Carboniferous of northwest Spain.

Sponges (Porifera) are considered to be the most primitive form of animals. They lack differentiated cells, and can reform if disassociated by (for example) shoving them through a sieve. On the other hand they cannot be considered colonies of single-celled organisms, as they have definite structures, bodies with more-or-less set shapes consisting of networks of pores and channels through which water is pumped; the individual cells feeding separately by filtering food from the water in these channels. They are the only extant group of animals with a fossil record that extends significantly into the Precambrian.

In a paper published in the journal Palaeontologia Electronica in August 2013, Diego Corrochano of the Departamento de Geología at the Universidad de Salamanca and Ronald West of the Kansas State University, describe a new form of Chaetetid Demosponge (a group of Sponges that played a major role in reef-building in the Late Palaeozoic; they still exist but play a less prominent role in modern ecosystems) from the Late Carboniferous of León in northwest Spain.

The new species is named Loiscupula bachendensi, where 'Loiscupula' derives from 'Lois' a village close to the site where it was found, and 'cupula' meaning 'cup-shaped', and 'bachendensi' derives from the Bachende Formation, in which the specimens were found. Loiscupula bachendensi has a flattened cup-shape, reaching 5 cm high and 32 cm across. The underside shows a number of concentric rings, possibly reflecting a growth pattern. The upper side is dotted with cylindrical features, which can be simple or branches and reach up to 3.4 cm above the cup. Internally the Sponge has a structure of polygonal or cylindrical tubes.

Loiscupula bachendensi. (2) Side view showing the flat cup-shaped skeleton, with the central part of the specimen lower than the outer edges. (3) Top view, showing the wackestone matrix filling the cup. (4) Underside of the sponge, showing the plate-shape and the concentric rings around a central point; note the projected structures developed within each ring and usually preserved as eroded (truncated) protuberances (arrow). Corrochano & West (2013).


The preserved skeletons of Loiscupula bachendensi are composed of course calcite, with occasional preserved fascicular needles. Corrochano & West believe the original skeleton have been composed of aragonite.

Idealized reconstruction of Loiscupula bachendensi. Note the low conical growth form; (A) presumed attachment point; (P) projections on lower surface; (G) grooves; (R) ridges; (P) plate like skeleton; (C) cylindrical/branching features (extended mamelons/chimneys) on upper surface. Corrochano & West (2013).



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