Marrella splendens
The Burgess Shale is the most famous fossil deposit on
Earth. It is located near the town of Field in Yoho National Park,
southeastern British Columbia, western Canada. The deposit is famous for
its spectacular soft-bodied preservation - the organisms have had their
appendages & internal organs preserved. Many tens of thousands of
fossils have been collected from the Burgess Shale Formation over the last
century. Including known, but unnamed species, and excluding known or
demonstrable junior synonyms, the Burgess Shale biota totals at least ~280
species.
Many claim that Charles Walcott discovered the Burgess
Shale Lagerstätte (as soft-bodied fossil deposits are called by
paleontologists) in 1909. However, it was actually discovered in 1886 or
1888 by Richard McConnell, based on anomalocarid appendage material from Mt.
Stephen, in the Campsite Cliff Member of the Burgess Shale Formation. The
main collecting localities have been two quarries (Walcott Quarry & Raymond
Quarry) on the western side of the ridge connecting Mt. Field and Wapta
Mountain a little north-northeast of Field. Numerous other smaller
localities have been identified in the same area & for many, many
kilometers to the south. Collecting at the Burgess Shale was most intense
in 1910-1917 (Charles Walcott), 1925-1930 (Harvard’s Museum of Comparative
Zoology), 1966-1967 (Geological Survey of Canada), and 1975-2000s (Royal
Ontario Museum).
The most common soft-bodied species in the Walcott
Quarry Member of the Burgess Shale Formation is an odd, small arthropod
called Marrella splendens Walcott, 1912. It cannot be classified
with any traditional arthropod group, and several new high-level taxa have been
created to accomodate it and other soft-bodied arthropods (e.g., see Hou &
Bergström, 1997 - Fossils & Strata 45).
Classification: Arthropoda, Lamellipedia, Marrellomorpha,
Marrellida, Marrellidae
Marrella
is quite distinctive - it has two large, curved lateral cephalic spines and a
pair of large, posteriorly-directed cephalic spines. Many Marrella
specimens have squeezed-out gut contents (see below).
Stratigraphy: Walcott Quarry Member, Burgess Shale Formation, Ptychagnostus
praecurrens Interval-zone, lower Marjuman Stage, middle Middle Cambrian.
Marrella splendens Walcott, 1912 (~2 cm long, including antennae) from
the Burgess Shale (Middle Cambrian) at the Walcott Quarry above Field, British
Columbia, Canada.
(YPM 5861, Yale University’s Peabody Museum, New
Haven, Connecticut, USA)