The dorsal, or upper side of Wiwaxia was covered in plates and spines called sclerites. Each one of these plates attached to the body wall with a root. These animals molted their sclerites when they grew (Morris 1985). The dorsal surface had about eight rows of sclerites along the length of its body, with approximately 6-8 sclerites per row. These sclerites overlapped one another (Morris 1985). On the sides, it had four rows of sclerites, the two upper rows facing upwards, while the two lower rows faced backwards (Morris 1985). In addition to these plates, it had two parallel rows of 7-11 vertical spines on its back on each side of the central axis (Morris 1985; Gould 1989).
Each sclerite has a hollow tube shaped root that expands out into a flat, one-sided blade, like a leaf (Smith and Lane 2014). The sclerites have longitudinal ridges, usually numbering between 9 and 15 (Smith and Lane 2014). The spines bear these ridges as well. Smaller sclerites have pustules that are absent is large sclerites (Smith and Lane 2014). The sclerites at the lower sides (ventro-lateral) of the animal are more sickle-shaped (Morris 1985; Smith and Lane 2014).
The ventral surface or ‘belly’ of Wiwaxia was in contact with the ocean floor and bore no sclerites (Morris 1985).
- Gould, S. J. 1989. Wonderful life. The Burgess Shale and the nature of history. W. W. Norton & Company, New York, NY.
- Morris, S. C. 1985. The Middle Cambrian Metazoan Wiwaxia Corrugata (Matthew) from the Burgess Shale and Ogygopsis Shale, British Columbia, Canada. Philos Trans R Soc Lond B Biol Sci 307:507-582.
- Smith, M. R., and P. Lane. 2014. Ontogeny, morphology and taxonomy of the soft-bodied Cambrian ‘mollusc’ Wiwaxia. Palaeontology 57:215-229.
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