Transactions of the Royal Society of Edinburgh: Earth Sciences

Research Article

Banffia constricta, a putative vetulicolid from the Middle Cambrian Burgess Shale

Jean-Bernard Carona1 p1

a1 University of Toronto, Zoology Department, Ramsay Wright Building, Toronto, Ontario M5S 3G5, Canada. e-mail: jcaron@rom.on.ca

ABSTRACT

Although Banffia constricta was first described in 1911, the affinities of this soft-bodied fossil animal have remained unclear. Banffia is redescribed here, on the basis of over 300 specimens. Banffia has a bipartite body measuring up to 10 cm in length. The entire body is axially twisted along a spiral, clockwise as seen from the front. The anterior section consists of two fused carapace-like units with a prominent crown-like structure at the anterior end surrounding the mouth. This crown-like structure is composed of three concentric circlets. A single antenniform outgrowth lies posterior to the mouth. The posterior section of Banffia is composed of 40 to 50 lightly sclerotised segments. The anus is terminal, and situated in a caudal notch. The gut is straight. Simple serially repeated structures along the gut may represent metameric mid-gut diverticulae. Banffia is considered to have been an epibenthic gregarious animal and possibly a deposit-feeder.

Banffia is putatively classified as an end-member of the phylum Vetulicolia, in a new class, the Banffozoa. If the vetulicolids represent a stem-group deuterostome, the absence of gills and a possible endostyle in Banffia is problematic. The presence of mid-gut diverticulae in Banffia may represent a link with the protostomes.

(Received July 28 2004)

(Accepted May 06 2005)

KEY WORDS

  • Body plan;
  • Cambrian explosion;
  • crown-group;
  • Deuterostome;
  • mid-gut diverticulae;
  • origins Of bilaterians;
  • Problematica;
  • Protostome;
  • stem-group

Correspondence:

p1 NSERC Post-Doctoral Fellow-Palaeobiology, Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario M5S 2C6, Canada.