A bizarre creature that lived in the ocean more than 500 million
years ago has emerged from the famous Middle Cambrian Burgess Shale in
the Canadian Rockies.
Officially named Siphusauctum gregarium, fossils reveal a
tulip-shaped creature that is about the length of a dinner knife
(approximately 20 centimetres or eight inches) and has a unique filter
feeding system.
Siphusauctum has a long stem, with a calyx – a bulbous
cup-like structure – near the top which encloses an unusual filter
feeding system and a gut. The animal is thought to have fed by filtering
particles from water actively pumped into its calyx through small
holes. The stem ends with a small disc which anchored the animal to the
seafloor. Siphusauctum lived in large clusters, as indicated by slabs containing over 65 individual specimens.
Reconstruction
of Siphusauctum gregarium. The animals are shown in life position,
standing upright in the water column partially anchored into the
sediment by a small holdfast. © Marianne Collins
Lorna O'Brien, a PhD
candidate in the Department of Ecology and Evolutionary Biology at the
University of Toronto and her supervisor Jean-Bernard Caron, curator of
invertebrate palaeontology at the Royal Ontario Museum, report on the
discovery today in the online science journal PLoS ONE.
"Most interesting is that this feeding system appears to be unique
among animals. Recent advances have linked many bizarre Burgess Shale
animals as primitive members of many animal groups that are found today
but Siphusauctum defies this trend. We do not know where it fits in relation to other organisms," said O'Brien.
Cluster of four specimens of Siphusauctum gregarium. Scale = 10 mm. © Royal Ontario Museum
"Our description is based on more than 1,100 fossil
specimens from a new Burgess Shale locality that has been nicknamed the
Tulip Beds," said lead author O'Brien. Located in Yoho National Park,
British Columbia, the Tulip Beds were first discovered in 1983 by the
Royal Ontario Museum. They are located high on Mount Stephen,
overlooking the town of Field. Like the rest of the Burgess Shale, the
Beds represent rock layers with exceptional preservation of mostly
soft-bodied organisms. The Burgess Shale, protected under the larger
Rocky Mountain Parks UNESCO World Heritage site and managed by Parks
Canada, preserves fossil evidence of some of the earliest complex
animals that lived in the oceans of our planet nearly 505 million years
ago. The discovery of Siphusauctum expands the range of animal diversity that existed during this time period.
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