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07/12/2017 | Pressemitteilung

Visiting scientist from Kassel solves mystery of Cambrian fossils

Three fossils from the Early Cambrian that have long puzzled scientists belong to one and the same primordial animal. This is shown by investigations of new, more than 500 million years old finds from the so-called Chengjiang deposit. The paleontologist Dr. Qiang Ou, a visiting scientist with Prof. Dr. Georg Mayer at the University of Kassel, played a key role in the study. The discovery provides new insights into the evolution of biodiversity during the so-called Cambrian explosion.

Image: Huanzhen Li & Qiang Ou
Reconstruction of the feather polyp †Xianguangia sinica, an extinct phylum representative of cnidarians (jellyfish, corals & co.).

According to the findings of Ou, Mayer and other co-authors, the primordial creature †Xianguangiasinica, which lived about 520 million years ago,differentlythan previously assumed, belongs tothe phylum of cnidarians, which today also includes jellyfish, corals and sea anemones. The animal was about five centimeters in size, resembled a polyp, but had an additional body cavity, which apparently served as a hydroskeleton, as well as an anchor device at the base of the body. Characteristic were feather-like tentacles, which were covered with numerous cilia and probably served for feeding. "The feather polyp," as the scientists have now colloquially christened †X. sinica ,"wasa so-called suspension feeder ," Mayer notes. That is, it filtered organic material out of the water by the blink of an eye and thus transported it toward the mouth. Until now, it had been assumed that †X. sinica, like most recent cnidarians, fed predatorily with the help of cnidocytes (= cnidocytes).

The scientists were also able toclarify the previously contradictory classification of the fossils †Chengjiangopennawangii (a supposed sea feather) and †Galeaplumosusabilus (the supposedly oldest hemichordate) unequivocally:Accordingly, these fossils are merely body fragments of †X. sinica, previously misidentified and described as two independent species.

The detailed reconstruction of the body structure of †X. sinicawas made possible by 85 new specimens, some of them exceptionally well preserved, from the Chengjiang deposit in China. Ou, Mayer and colleagues examined these using light and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), among other techniques. The scientists then also performed phylogenetic analyses to classify the fossil species in the animal phylogenetic tree. The results suggest that the diversity of body forms and diets of the prehistoric cnidarians was greater than previously thought.

Crucial parts of this study were conducted at the University of Kassel, where Dr. Qiang Ou (40) has been conducting research at the Department of Zoology since July 2016 as a fellow of the Alexander von Humboldt Foundation.

Numerous previously unknown fossils have been discovered in the Chengjiang deposit in recent decades, which now open up a new dimension to our understanding of the evolution of species diversity in the Cambrian era. However, many of these fossils have not yet been fully and unequivocally evaluated. The term Cambrian explosion refers to the massive appearance of new species during the Cambrian age, about 530 million years ago.

The results have now been published in the prestigious journal Proceedings of the National Academy of Sciences of the United States of America (PNAS): http://www.pnas.org/content/early/2017/07/26/1701650114.abstract.

 

 

Reconstruction of the feather polyp †Xianguangia sinica, an extinct phylum representative of the cnidarians (jellyfish, corals & Co.). Copyright: Huanzhen Li & Qiang Ou: http://www.uni-kassel.de/uni/fileadmin/datas/uni/presse/anhaenge/2017/Fossil_Photo_Qiang_Ou_Huanzhen_Li.jpg

 

Contact:

Prof. Dr. Georg Mayer

University of Kassel

Department of Zoology

Tel: +49 (0)561 804-4805

E-mail: georg.mayer[at]uni-kassel[dot]de