Without oxygen, there would be no carnivores. Without carnivores, there would be no Cambrian explosion, the stunning evolutionary burst of diversity in species and body forms that began 540 million years ago.
Those are the findings of a new study that stitches together competing models for why meat-eating appeared simultaneously with the Cambrian explosion. Previously, one camp of scientists had proposed that rising oxygen levels gave animals the extra power to evolve complex body forms. Another school of thought said that competition among animals drove the sudden appearance of new species, such as the weird and wild life forms found in the Burgess Shale, a rock formation in Canada that has been an amazing source of fossils.
"There’s always been this tension," said lead author Erik Sperling, a postdoc at Harvard University. “Each side is looking at their own data, which is often common in science.”…
… is an extinct stem-arthropod genus found in Cambrian fossil deposits. The only known species, O. regalis, is known from the Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they comprise less than 0.1% of the community.
Opabinia was a soft-bodied animal of modest size, and its segmented body had lobes along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food…
(read more: Wikipedia) (illustrations by Nobu Tamura)
Wiwaxia was one of the bizarre animals found in the 505-million-year-old Burgess Shale Formation of British Columbia, Canada.
Squashed flat in the rocks, these 5cm (2”) spiny creatures were difficult to analyze and reconstruct, and what exactly they were is still being debated. For many years they were tentatively considered to be distant relatives of polychaete or annelid worms, but more recent studies and better microscopic imaging techniques have found a primitive radula-like structure in their mouths — suggesting that they might actually be closer related to molluscs.
The armour coat of scale-like sclerites and the long asymmetrical rows of spines were probably a defense against predators. I’ve given it a splash of some sea-slug warning colors here just for fun.
Opabinia is an extinct stem-arthropod genus found in Cambrianfossil deposits. The only known species, O. regalis, is known from the Middle Cambrian Burgess ShaleLagerstätte of British Columbia, Canada. Fewer than twenty good specimens have been described. Opabinia was a soft-bodied animal of modest size, and its segmented body had lobes along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food…
Where: Specimens first known from the Burgess Shale of Canada, now possibly found in other sites in North America of similar ages.
What: Perspicaris is another enigmatic stem arthropod from the Burgess Shale fossil lagerstatten deposit. It is a bivalve arthropod, like our last Burgess Shale fossil Tuzoia, but has more bits than just its eyes sticking out, so more conclusions as to its life style can be drawn. Sticking out from the front of its carapace are eyes and relatively thick antennae and emerging posteriorly is a powerful tail. Perspicaris swam though the water column under its own power, but swam to the bottom of the paleo-ocean to feed. Sediment preserved in the gut of a few specimens shows this animal was a deposit feeder; consuming loose mud on the ocean floor and processing all minute food particles from these sediment grains.
The evolutionary relationships of Perspicaris are not well known, like Tuzoiait is proposed to either be related to a subgroup of crustaceans or to be a stem taxon to all living arthropods. As you probably have concluded, the relationships between all of these taxa is an area of paleontology that really needs more people working on it!
What: Fasciculus is yet another fantastic fossil from the Burgess Shale fossil site in BC, Canada. It is extremely rare, with only one known specimen. This single specimen was found in 1917, but not fully described in detail until 1996. It is about 4.5 inches (11.4 cm) wide, and is perserved in intricate detail.
Unlike most fossils from the Burgess Shale, Fasciculus is confidently linked to a living group. It is placed as a stem Ctenophora,which are the comb-jellies. Comb-jellies are not closely related to ‘normal’ jellyfish, which fall into the cnidaria along with the hydras. Ctenophoras are cup-like animals that swim though the water, with multiple sets of cilia arranged in longitudinal series, so that they resemble combs, giving them their common name of comb-jelly. In Fasciculus you can see these rows wonderfully preserved. The discovery of a stem member of this lineage once again shows that most, if not all, modern phyla were well separated even as long ago as the Cambrian.
What: Opabinia is one of the rarest forms from the Burgess Shale fossil lagerstatten. We have explored the Burgess Shale fauna before with Anomalocarisand Hallucigenia. Opabinia, unlike these other species, has not had a confusing history with various interpretations of its anatomy. This does not mean that 1.5-3 inch (4-7cm) long invertebrate is much like any modern form though! Far from it, Opabinia is unlike anything alive today. Much of its body resembled Anomalocaris, which it is possibly related to, but its head is where the most bizarre features were. It had 5 eyes and a proboscis up to 1/3rd of its length, ending in a form of gripping claw. This proboscis was flexible enough to curve around to its mouth, which was hidden on the underside of its head and directed posteriorly. It is thought Opabinia swam though the ancient seas by flexing its body, picking up soft bodied prey animals with this ‘trunk’. No traces of legs have been found in any of the ~20 or so fossil specimens.
Like most Burgess Shale taxa, the relationships of Opabinia are uncertain. It is somewhat hesitatingly placed as a stem arthropod in a lot of classifications, but this relationship is based in turn on an uncertain link with Anomalocaris. It is possible that Opabinia is far removed from all modern phyla. One of the biggest supports for this later view is its 5 eyes, a configuration never again seen in the history of life.
I might have gone a bit overboard with the images today, but this is one of my most favorite fossil forms! It is just so odd and different from anything else.