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Title: Priapulid worms: Pioneer horizontal burrowers at the Precambrian-Cambrian boundary
Authors: Jean Vannier1, Ivan Calandra1, Christian Gaillard and Anna ylinska

The major evolutionary events that characterise the Precambrian-Cambrian transition are accompanied by profound ecological changes in the composition of benthic communities, the nature of the substrate, and the occupation of marine ecospace. The increased animal activity on and within the substrate is attested to by numerous trace fossils, such as the cosmopolitan Treptichnus pedum whose first appearance is used as the global stratotype section and point (GSSP) to mark the base of the Cambrian. In spite of its major importance in biostratigraphy, the maker of Treptichnus  trace fossils, and more generally of treptichnids, has long remained an enigma. Treptichnids were subhorizontal burrow systems produced in the subsurface and had a worldwide distribution throughout the Cambrian. Here we show, by using experimental ichnology, that the treptichnid burrow systems were most probably produced by priapulid worms or by worms that used the same locomotory mechanisms as the Recent priapulids (e.g., Priapulus). Their typical three-dimensional morphology with repeated arcuate probing branches suggests that their function was related to the feeding strategy of the worm such as predation or scavenging upon small epibenthic or endobenthic invertebrates. This interpretation is strongly supported by the preserved gut contents of Cambrian priapulids from the Burgess Shale Lagerstätte that contain effectively a variety of small epibenthic prey. The antiquity of treptichnids would designate priapulids as one of the earliest infaunal colonisers of the substrate that possibly interacted with epibenthic communities, thus playing a leading role in the construction of the early marine food chain, and as important subhorizontal bioturbators in the early stages of the "Cambrian Substrate Revolution."

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Treptichnus pedum
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Treptichnus pedum (formerly Phycodes pedum, Manykodes pedum by J. Dzik, or sometimes wrongly named Trichophycus pedum) is regarded as the earliest widespread complex trace fossil. Its earliest appearance, which was contemporaneous with the last of the Ediacaran biota, is used to define the dividing line between the Ediacaran and Cambrian Periods. However, it has since been discovered below the originally defined global boundary stratotype section.
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In the '80s, Spanish researchers found the first fossils of Cloudina in Spain, a small fossil of tubular appearance and one of the first animals that developed an external skeleton between 550 and 543 million years ago. Now palaeontologists from the University of Extremadura have discovered a new species, Cloudina carinata, the fossil of which has preserved its tridimensional shape.
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Ediacaran biota
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This year marks two important anniversaries in the history of the study of life on Earth: the birth in 1919 of the geologist Reginald Sprigg, and the death in 1989 of the palaeontologist Martin Glaessner. Both of these men spent large portions of their careers working on some of the most enigmatic creatures in the fossil record - the Ediacarans - a group of multicellular organisms that lived for a relatively narrow slice of time between 575 and 542 million years ago during the Ediacaran period (whose span was formally defined in 2004 as encompassing the interval between 635 and 542 million years ago). The fleeting existence of the Ediacaran biota occurred just before the rise of complex animal life.
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Eight-Armed Animal Preceded Dinosaurs
An eight-armed creature that looked more like a modern party favor than a living animal colonised a large section of the world's oceans over 300 million years before the first dinosaurs emerged, suggests a new study.
The findings represent the first comparable animal fossils from the Ediacaran Period, 635 to 541 million years ago, which appear in two drastically different preservation environments -- black shale of South China and quartz rock of South Australia.

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The fossilised trail of an aquatic creature suggests that animals walked using legs at least 30 million years earlier than had been thought. The tracks - two parallel rows of small dots, each about 2 millimetres in diameter - date back some 570 million years, to the Ediacaran period. The Ediacaran preceded the Cambrian period, the time when most major groups of animals first evolved.

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Earliest animal fossils

The fossilised trail of one of the earliest animals - a multilegged creature that walked over the bed of an ancient sea once covering Nevada



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The fossilised trail of an aquatic creature suggests that animals walked using legs at least 30 million years earlier than had been thought. The tracks -- two parallel rows of small dots, each about 2 millimetres in diameter -- date back some 570 million years, to the Ediacaran period.

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Flinders Ranges rocks contain a rare frozen record of extreme climate change, leading researchers say.
Dr Alan Collins from Adelaide University's school of Earth and Environmental Sciences, said the rocks provided a unique glimpse of weather patterns 600 million years ago.

"The rocks at the bottom of Enorama Creek in the Flinders Ranges were deposited near the equator, providing some of the best evidence of climate change"

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Latitude: 31°19'53.2"S, Longitude: 138°38'0.2"E.

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