Burgess shale Animals Interpretation Commentary

Charles Doolittle Walcott paleontology

Burgess shale

• Charles Wolcott discovered
• in a shale outcropping
• on a steep mountainside
• of Mount Field in the
• Canadian Rockies
• fossils from five-hundred
• and five million years ago
• including impressions
• of soft body parts of
• previously unknown
• extinct animals.

Animals

• Amiskwia, a soft-bodied invertebrate,
• had a rounded head with a pair of tentacles and a four-ganglion brain,
• a flexible body with rounded fins on the sides,
• and a paddle-shaped tail.
• Anomalocaris, meaning “abnormal shrimp,” was a large arthropod
• with compound eyes on two stalks with thirty thousand lenses.
• Canadaspis had claws on its front appendages
• and spines on its head to protect its eyes.
• It had numerous legs with gill flaps under them.
• Its body was protected by hinged clamshells;
• the end of its thick segmented tail had spines.
• Canadia, a spiny polychaete annelid worm,
• looked like a long feathery slug with a pair of tentacles or parapodia
• and it had a gut that it could extend out as a feeding proboscis.
• Choia was a demosponge like the barrel sponge
• with a flattened conical body stiffened with long spines.
• Hallucigenia, was an odd kind of wormy creature
• with seven pincer-tipped tentacles lined up on one side
• and seven pairs of jointed spines on the other,
• but with no obvious head or means of locomotion.
• Haplophrentis was a small conical shelled creature
• with a small shell closing the big end
• and leaving two gaps on each side
• from which protruded fleshy curved arms.
• Leanchoilia had two front arms ending in whip-like feelers.
• Its body was protected by a segmented shell like a pill bug.
• Marrella is a small animal whose head shield
• had two pairs of curved rearward blades
• protecting its body from above.
• Under its head were two pairs of antennae,
• one long and sweeping back,
• the second shorter and stouter.
• Its body had two dozen segments,
• each with a pair of branched appendages,
• the lower branches being legs
• and the upper branches feathery gills.
• Odontogriphus, meaning “toothed riddle,” was like a tongue
• with a circular mouth on its underside having rows of teeth.
• Opabinia had five eyes, a tubular feeding proboscis
• a fifteen-segmented body with side lobes, and a fan-shaped tail.
• Ottoia was a predatory carnivorous priapulid worm.
• Its eversible spiney proboscis protruded from its U-shaped burrow.
• Peytoia, also called Laggania, swam like a cuttlefish
• and had two mouth appendages with long bristle-like spines.
• Perspicaris had two large eyes and a forked tail;
• the two sides of its thorax were hinged at the top.
• Pikaia was a swimming eel-like finned-tail creature
• with pair of tentacles and gill slits on either side of its head.
• Thaumaptilon, meaning “wonderful soft feather,”
• was a leaf-shaped animal attached to the sea floor.
• Trilobite was a common three-lobed arthopod,
• with a cephalon or head shield,
• a thorax with seven jointed segments,
• and a semicircular pygium rump.
• Wolcott found the basic Olenoides serratus
• and two-lobed Naraoia compacta, which lacks a pygium.
• Wiwaxia was a small oval animal sheathed
• in small hard overlapping plates or scales
• and protected by short ribbed spines or bristles.
• Yohoia had a head shield and thirteen body plates
• followed by a paddle-like tail. Under its head
• were two long arms, each ending in four spines like little fingers,
• and three pairs of appendages that probably served as legs,
• and under its body plates were single flaps with fringes.

Interpretation

• Interpreting the fossils of the Burgess Shale has continued.
• Were they evidence of a Cambrian explosion,
• the sudden appearance of multi-celled animals,
• defying Darwin and the orderly progress of evolution?
• Were they relatives of animals living today,
• such as branchiopods, crustaceans, echinoderms, and molluscs?
• Was Amiskwia an arrow worm, a ribbon worm, a mollusc,
• or an animal with no affinity to any living or extinct animal?
• Were the mouth, feeding appendages, and tail of Anomalocaris,
• discovered at first separately, separate creatures?
• Was Canadaspis a crustacean or an euarthropod?
• Did the spines of Choia radiate up and out for protection
• or were they laid out flat like the guy wires of a tent?
• Did Hallucigenia walk upon its spines,
• or did it slither in the mud on its belly?
• Was Haplophrentis a swimmer or a bottom feeder?
• Did Leanchoilia have two stalked compound eyes and two simple eyes,
• or did it have no eyes at all?
• Marrella was a primitive arthropod, but was it
• an early crustacean, scorpion, or trilobite?
• Was Odontogriphus the tongue of another creature?
• Was it an early mollusc, brachiopod, or worm?
• Were Opabinia’s gills set on top of its lobes
• or on special blades attached to the underside of its lobes?
• Was Ottoia a hunter, or did it wait for prey from its burrow?
• Walcott mistook Peytoia’s mouth for a jellyfish.
• Its feeding appendage and body were later found to be attached.
• Wolcott categorized Pikaia as a polychaete worm
• but others see it as a chordate or primitive vertebrate.
• Were Thaumaptilon sea pens, or colonial animals like corals?
• Thousands of spots on one of its sides could be separate creatures.
• Edward Lhwyd described a trilobite in 1698 as the skeleton of a flat fish.
• Charles Lyttleton in 1749 described it as a petrified insect.
• Manuel Mendez da Costa in 1754 said it was a marine louse.
• The Utes of North America called them little water bugs
• and wore them as amulets to ward off disease.
• Was Wiwaxia a polychaete, an annelid worm,
• or a primitive mullusc?
• To me, it looks like a simple sea urchin.
• Yohoia was shaped like a mantis shrimp
• but is thought to be an early horse-shoe crab or trilobite.