Death march of a segmented and trilobate bilaterian elucidates early animal evolution

The origin of motility in bilaterian animals represents an evolutionary innovation that transformed the Earth system. This innovation probably occurred in the late Ediacaran period—as evidenced by an abundance of trace fossils (ichnofossils) dating to this time, which include trails, trackways and b...

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Bibliographic Details
Published in:Nature (London) 2019-09, Vol.573 (7774), p.412-415
Main Authors: Chen, Zhe, Zhou, Chuanming, Yuan, Xunlai, Xiao, Shuhai
Format: Article
Language:English
Subjects:
631/181/414
704/2151/414
Analysis
Animals
Bilateria
Biological Evolution
Burrows
Chronology
Dating
Etymology
Evolution
Fossils
Geology
Humanities and Social Sciences
Identification and classification
Innovations
Letter
Motility
Movement - physiology
multidisciplinary
Natural history
Neoproterozoic Era
New species
Polarity
Science
Science (multidisciplinary)
Segmentation
Stratigraphy
Trace fossils
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Summary:The origin of motility in bilaterian animals represents an evolutionary innovation that transformed the Earth system. This innovation probably occurred in the late Ediacaran period—as evidenced by an abundance of trace fossils (ichnofossils) dating to this time, which include trails, trackways and burrows 1 – 3 . However, with few exceptions 4 – 8 , the producers of most of the late Ediacaran ichnofossils are unknown, which has resulted in a disconnection between the body- and trace-fossil records. Here we describe the fossil of a bilaterian of the terminal Ediacaran period (dating to 551–539 million years ago), which we name Yilingia spiciformis (gen. et sp. nov). This body fossil is preserved along with the trail that the animal produced during a death march. Yilingia is an elongate and segmented bilaterian with repetitive and trilobate body units, each of which consists of a central lobe and two posteriorly pointing lateral lobes, indicating body and segment polarity. Yilingia is possibly related to panarthropods or annelids, and sheds light on the origin of segmentation in bilaterians. As one of the few Ediacaran animals demonstrated to have produced long and continuous trails, Yilingia provides insights into the identity of the animals that were responsible for Ediacaran trace fossils. Yilingia spiciformis , a bilaterian dating to the Ediacaran period, is described from body fossils associated with trails produced by the animal, shedding light on the origins of segmentation and motility in bilaterian animals.
ISSN:0028-0836
1476-4687
DOI:10.1038/s41586-019-1522-7