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A possible new pattern of cortical deposit in Tremadoc dendroid graptolites from chert nodules

Adam Urbanek & Piotr Mierzejewski

in: Hughes, C.P. & Rickards, R.B. (eds), 1986, Palaeoecology and Biostratigraphy of Graptolites, Geological Society Special Publication No. 20, pp. 13-19.
[Abstract] Rhabdosome fragments of dendroid graptolites (Dendroidea) from upper Tremadoc chert nodules, studied with SEM, show an unusual pattern of cortical tissue. In contrast to previously studied tissues it consists of an irregular meshwork of wavy, branching and interconnecting fibrils. Differentiated in size and thickness, the fibrous material includes thick, strongly branched fibres. Their presence is a characteristic feature of the cortex in the dendroids examined. The observed pattern of ultrastructure is tentatively described as 'reticulate fabric'. Its nature remains obscure. It may represent a primary feature, thus being an usual state of aggregation of fibrous material, but its secondary origin due to preservational degradation of normal dendroid cortex seems more plausible.
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