Canadaspis perfecta

Overview

A two-valved carapace up to 5.2 cm covered about half the body; that figure measures the carapace, not the whole animal. The head carried eyes, unsegmented anterior appendages, antennulae and toothed mandibles. Eight thoracic segments bore two-branched limbs whose outer branches are interpreted as gills; seven abdominal segments lacked legs.

Its mandibles suggest it fed on coarse particles and other material, and it is reconstructed as a near-bottom swimmer or walker that scavenged and particle-fed. Fossil midgut glands are preserved. On one slab of about a square metre, Haug, Caron and Haug (2013) counted at least 743 shields. Fewer than 10 percent kept thoracic parts, none showed guts, and other animals there were well preserved. They inferred moults from a synchronised moulting event rather than mass death.

Walcott first assigned the species to Hymenocaris in 1912; the genus Canadaspis was erected in 1960. The museum account replaces the older crustacean identification with placement among hymenocarine mandibulates in Canadaspidae.

Origins & earliest records

Walcott described it under Hymenocaris in 1912; Canadaspis was erected in 1960.

Evidence & interpretation

Over 5,000 museum specimens, including lectotype USNM 57703 and a moult-rich slab.

Selected bibliography

Documented works and useful reading. This is not a list of every appearance.

1. 01

   Canadaspis perfecta

   Royal Ontario Museum · n.d.

   Selected bibliography; museum account read: taxonomy, age, research history, description, ecology.

2. 02

   Demecology in the Cambrian: synchronized molting in arthropods from the Burgess Shale

   Haug, Caron & Haug · 2013

   Selected bibliography; Abstract, Results and Figure 1 caption used for the Canadaspis slab only.

Family, evolution & connections

Taxonomic classification

A hierarchy of classified groups, not a chain of direct ancestors.

Source note: Hymenocarine mandibulate; the historical crustacean identification is superseded.

1. familyCanadaspidae
2. genusCanadaspis

References

Sources supporting this profile. Linked pages have their own scope and editorial standards.

1. museumcanadaspis perfectaResearch access: 2026-10-06
2. journal articleDemecology in the Cambrian: synchronized molting in arthropods from the Burgess ShaleResearch access: 2026-10-06

Image credits

A sourced illustration has not yet been added. This gap is included in the coverage record.