Tritonychus

Tritonychus phanerosarkus is a Cambrian lobopodian, exceptionally preserved in the Orsten fashion by phosphate deposition, additionally preserving muscle fibres. Its name loosely translates to "Three-clawed animal with well displayed flesh". Phylogenetic analysis suggests that it was a close relative of the Onychophora, possibly even a member of the main lineage. The fossil was discovered in the Xiaotan section, Yongshan, Yunnan Province in the Yu'anshan Formation.

The muscle fibres preserved in its legs establish peripheral musculature as a characteristic of all panarthropods, but are arranged in an unusual pattern (detailed below).