| Palæos: |  |
Procoelomates |
| INVERTEBRATES | Turrilepadida |
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| Palæos: | |
Procoelomates |
| INVERTEBRATES | Turrilepadida |
| Page Back | Unit Home | Animal Kingdom | Metazoa | Mikko's Phylogeny Home |
| Page Next | Page Up | Invertebrates | Kingdoms Index | Vertebrates Index |
These strange creatures were at one time thought to Palaeozoic barnacles. They first appear during the early Ordovician and continue until the Carboniferous. They have elongate plated bodies and presumably crawled along the sea bottom.
The Ordovician to Devonian Lepidocoelids had an elongate blade-like form (the "dorsal" edge thicker, the "ventral" straighter and thinner) and possessed two rows of overlapping alternating plates.
The Turrilepadids had four to six rows of triangular plates. In the most primitive form, the Ordovician to Devonian Plumulites, the thoracic lateral scales were different in form to the forward lateral scales, extending back in long spines reminiscent of halkeriids or wiwaxiids, with which these creatures were obviously related. More typical forms like Turrilepis were more regular in form, and the most advanced form was the extraordinary Silurian "segmented clam", Aulakolepos ketleyanum (Reed 1901)
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Links |  |
Machaeridia: Lepidocoleus jamesi
Machaeridians of the Al Rose Formation, Inyo Mountains, California
Jerzy Dzik, 1993, "Early Metazoan Evolution and the Meaning of Its Fossil
Record", in Evolutionary Biology, vol. 27, edited by Max K. Hecht et al., Plenum Press, New York, fig. 11 p.367
Karl Von Zittel Text-Book of Paleontology, ed. Charles R. Eastman, 2nd ed. vol.1 1937 MacMillan & Co. London, pp.743-4
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