Saturday 2 November 2013

A Chambered Glass Sponge from the Early Devonian of northern 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 forthcoming paper in the journal Acta Palaeontologica Polonica available online from 17 June 2013, Martin Nose of the SNSB-Bavarian State Collection of Palaeontology and GeologyRadek Vodrážka of the Institute of Geology at the Academy of Sciences of the Czech Republic and Luis-Pedro Fernández and Isabel Méndez-Bedia of the Departamento de Geología at the Universidad de Oviedo, describe a species of Chambered Glass Sponge from the Early Devonian of northern Spain.

 The new species is placed in the genus Casearia, and given the specific name Casearia devonica. It is the oldest member of the genus by around 200 million years, as well as being the oldest known Chambered Glass Sponge and the first Chmabered Glass Sponge from the Palaeozoic. Chambered Glass Sponges are otherwise known from the Late Triassic to the Late Jurassic.

Casearia devonica is a straight or branching Chambered Sponge, comprising up to 18 chambers, each 0.5 to 5.0 mm in height. It was discovered in shales of the Valporquero Formation near the village of Colle in the Cantabrian Mountains in northern Spain. These shales are thought to have formed in mud mounds between Coral outcrops, in waters bellow the storm wave-base. Modern Glass Sponges no longer form similar chambered shapes, but they do typically live bellow the wave-base, being found across the globe in waters deeper than 100 m.

Chambered Hexactinellid Sponge Casearia devonica in thin section. Scale bar is 5 mm.

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