Feb 6, 2017

Miniscule bag-like animal at the root of human ancestry (and that of starfish, and....)

Luckily it is only the size of a pinhead and has been extinct for some 540 million years, otherwise the monstrous appearance of Saccorhytus coronarius would be the stuff of nightmares. And, like it or not, scientists think that this is one our remote human ancestors.
Category: General
Posted by: Sarah

reconstruction of the millimetre-sized Saccorhytus coronarius The 540 million year old fossil remains of Saccorhytus coronarius has been squashed over time but still clearly shows its large mouth and the strange cone-like structures on its body.

The millimetre-sized Saccorhytus was a bag shaped creature with a flexible ‘skin’, large mouth and so far as we can tell no anus, which lived in earliest Cambrian times, when life was confined to the seas. At that time life was only just beginning to evolve and split into familiar animal groups of today, such as the sponges, jellyfish-like cnidarians and molluscs. Until now fossil evidence for more complex deuterostome animals, such as sea urchins, starfish, hemichordates and all vertebrates did not appear until between 520 and 510 million years ago.

However, the new fossil discovery of Saccorhytus from early Cambrian age limestones in China has pushed the record of deuterostome evolution back to earliest Cambrian times. Cambridge palaeobiologist, Simon Conway Morris, along with Chinese and German colleagues claim that their new fossil preserves fundamental features characteristic of the deuterostomes, such as bilateral symmetry as opposed to the radial symmetry found in more primitive animals such as corals and jellyfish. As a deuterostome,

Saccorhytus is the earliest known member of this large group and gives us an idea of what our most remote ancestor might have looked like.

The scientists searched through the residues of some 3 tonnes of limestone, which they dissolved in acid, looking for any identifiable organic remains. Organic microfossils of various kinds are known from rocks of this age but most of them are spores and cysts of relatively primitive organisms.

Conway Morris and colleagues have never before seen any fossils quite like Saccorhytus, whose tiny flattened remains are preserved in extraordinary detail. One of the most curious features of Saccorhytus is the array of tiny cones on the surface of the body bag. In the absence of an anus, they may have functioned as return outlets for water taken in through the mouth. As such, they were precursors to the gill-slits, which are one of the defining characters of the deuterostomes.

This new research by Professor Simon Conway Morris of the Department of Earth Sciences in the University of Cambridge is published in Nature. Reference: Jian Han, Simon Conway Morris, Qiang Ou, Degan Shu and Hai Huang. Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China). DOI: 10.1038/nature21072.

Monday to Friday
10:00 to 13:00 & 14:00 to 17:00

10:00 to 16:00 


We are CLOSED on Good Friday but open Saturday and Monday as usual


How do you reach an untapped audience 4 hours away? You join forces with colleagues in affiliated organisations and travel down to the seaside together to do some outreach!

Explosive (Earth) activities @ the Sedgwick Museum took place on Saturday 18th March 2017...!

A new hypothesis of dinosaur relationships and early dinosaur evolution



'Tools of the Trade'
Available to purchase in the Sedgwick Museum shop

Tools of the Trade

Agostino Scilla's
'Vain Speculation Undeceived by Sense'
English translation available to download.
Agostino Scilla download

Our Rocks are on the Move!
We are reuniting our important rock collections under one roof! Can you help support the building of our new Sedgwick Museum Collections store? Read more and donate here

Friends of the Sedgwick Museum prizewinners give us their thoughts on their time at the Museum in 2016
Click here to read

Work Experience at the Sedgwick - read about our latest student to visit us for two weeks and experience life in a Museum. 

Studying Earth Sciences at Cambridge University

Did you know?
The University of Cambridge is listed at the top of The Complete University's Guide 2016 for geology.

Discover more about studying Earth Sciences at the University of Cambridge in this video featuring Museum Curator of Mineralogy and Petrology Professor Marian Holness and Sir David Attenborough