Graptolite synrhabdosomes: biological or taphonomic entities?

Synrhabdosomes, structures made of mostly radially arrayed graptolite rhabdosomes attached by distal regions of their virgulae, have been considered as biological entities by some in the past, but as taphonomic structures by others more recently. Our survey of at least 200 synrhabdosomes, more than...

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Bibliographic Details
Published in:Paleobiology 1998, Vol.24 (1), p.37-48
Main Authors: Gutiérrez-Marco, Juan Carlos, Lenz, Alfred C.
Format: Article
Language:English
Subjects:
Aggregation
Bedding planes
Biological taxonomies
Earth sciences
Geology
Graptoloidea
Marine
Paleontology
Plankton
Shales
Taphonomy
Taxa
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Summary:Synrhabdosomes, structures made of mostly radially arrayed graptolite rhabdosomes attached by distal regions of their virgulae, have been considered as biological entities by some in the past, but as taphonomic structures by others more recently. Our survey of at least 200 synrhabdosomes, more than 90 of which derive from one locality in northwestern Spain, shows that all synrhabdosomes are most probably entirely monospecific assemblages composed of a more or less finite number of rhabdosomes, all of which are consistently straight or only weakly curved, and all of which bear simple, or relatively simple, thecae. We conclude, therefore, that synrhabdosomes are biological entities, and we suggest that they formed infrequently as, perhaps, temporary structures to increase food-gathering efficiency during times of lower plankton supply in local, relatively restricted water masses.
ISSN:0094-8373
1938-5331
DOI:10.1017/S0094837300019953