Marrella splendens Walcott, 1912

Taxonomy

Lace Crab

Kingdom: Animalia
Phylum: Arthropoda
Class: Marrellomorpha
Order: Marrellida
Family: Marrellidae
Genus: Marrella
Species: Marrella splendens
Author Citation Walcott, 1912

Geological Time Scale

Eon: Phanerozoic
Era: Paleozoic
Period: Cambrian
Sub Period: None
Epoch: Miaolingian
International Age: Wuliuan

Stratigraphy

Stephen Formation
Phyllopod Beds

Provenance

Acquired by: Purchase/Trade

Dimensions

Length: 2 cm

Location

Walcott Quarry
Field, Yoho National Park
British Columbia
Canada

• burgess
• cambrian
• lace crab
• marrella
• tff-oilshale-ar1214
• walcott

Comments

This arthropod is a Marrellomorph, a clade of strange looking stem-group arthropods known from the Cambrian Burgess Shale and the slightly older Kaili Fauna in China (Marrella), the Silurian Herefordshire Lagerstätte in England (Xylokorys), the Ordovician Basal Upper Fezouata Formation (lower Arenig, or lower Floian), north of Zagora in southeastern Morocco and the Caradoc (Upper Ordovician) in Bohemia (Furca) and the Devonian Bundenbach Shale in Germany (Mimetaster and Vachonisia).
Marrellomorphs lacked mineralized hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. 

The head shield has two pairs of long rearward directed spikes. Marrellomorphs possessed two pairs of antennae, one long and sweeping, the second shorter and stouter. The two dozen segments each have a pair of six segmented leg / feathery gill structures. There is a tiny, button like telson at the end of the thorax. The best modern guest is that Marrellomorphs are moderately evolved primitive arthropods descended from a common ancestor of the major later arthropod groups.

Reconstruction of another Marrellomorph -  Mimetaster hexagonalis - from Bundenbach, Germany.

Reconstruction of Marrella splendens from the Cambrian Burgess Shale in Canada.

 

A thorough re-investigation of based on over 1000 specimens was recently published by D. García-Bellido and Marrella splendensD. Collins: “A new study of Marrella splendens (Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada” in Can. J. Earth Sci. 43(6): 721–742 (2006).

The overall form of Marrella and other Marrellomorphs suggests that it was a soft-bottom dweller. The wide carapace border would have prevented sinking into unconsolidated sediment.

Marrella splendens is the most abundant non-trilobite arthropod from this Lagerstätte. They are considered to live in groups of several individuals; two, three or even more species on one slab are not uncommon.