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You are here:   animal list > Cryptoplax larvaeformis




Cryptoplax larvaeformis (Burrow, 1815)

Flexible Chiton of the Great Barrier Reef

Samantha Oliver (2011)




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Evolution & Systematics

Fossil History

Systematics and Phylogenetics

Morphology and Physiology

External Morphology

Internal Anatomy

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Fossil History

Chitons have appeared in the fossil record as early as the upper cambrian (Yates el al1992), since this time Chiton plate morphology and the general body plan has not changed significantly (Hoare 2000). However, fossilised shell plates show that microaesthetes stuctures are a post-Paleozoic innovation. There are 3 fossils that provide insights into the ancestral  origins of the Chiton.

Wiwaxia corrugata:
This fossil it remarkably similar to molluscs in terms of body shape as well as having a radular like feeding structure found to be homologous  to the extant mollusc Helicoradomenia, suggesting molluscan ansestory (Figure 1) (Yates el al1992)

Odontogriphus omalus:
Like molluscs, Odontogriphus is dorso-ventrally flattened, and is elongated in body plan, it has a muscular foot lined with si
mple gills, and a central, ventral mouth that houses a radula. This radula was seen to be very similar to the radula of Wiwaxia (above), again suggesting molluscan affinity 's (figure 2) (Yates el al1992).

Halkieria evangelista:
Is a fossil found to have sticking similarities to polyplacophorans it is:
  • similar in it's mineralogical composition.
  • overall morphology
  • sclerite arrangement
However, different from Chiton in that Halkieria lacks an important layer of shell (the tagmotum) as well as pore canals in its terminal shell plate.