Strange phallus-shaped creature provides crucial missing link: Discovery pushes fossil record back 200 million years

Mar 13, 2013
Two individuals of Harrimania planktophilus, a modern enteropneust (harrimaniid) worm. This proboscis is to the left. The total length of a relaxed and uncoiled animal is approximately 32 mm. Credit: C.B. Cameron, Université de Montréal

Christopher Cameron of the University of Montreal's Department of Biological Sciences and his colleagues have unearthed a major scientific discovery - a strange phallus-shaped creature they found in Canada's Burgess Shale fossil beds, located in Yoho National Park. The fossils were found in an area of shale beds that are 505 million years old.

Their study, to be published online in the journal Nature on March 13, 2013, confirms Spartobranchus tenuis is a member of the acorn worms group which are seldom-seen animals that thrive today in the fine sands and mud of shallow and . Acorn worms are themselves part of the , a group of closely related to today's sea stars and . "Unlike animals with hard parts including teeth, scales and bones, these worms were soft-bodied, so their fossil record is extremely rare," said author Dr. Chris Cameron of the University of Montreal. "Our description of Spartobranchus tenuis, a creature previously unknown to science, pushes the fossil record of the enteropneusts back 200 million years to the , fundamentally changing our understanding of biodiversity from this period."

Since their discovery in the 19th-century, some of the biggest questions in hemichordate evolution have focused on the group's origins and the relationship between its two main branches: the enteropneusts and the pterobranchs, including graptolites. "One of the big punchlines from my graduate work, was that enteropneusts and pterobranchs are closely related" said Cameron, a specialist on the taxonomy, evolution and biogeography of hemichordates.

Spartobranchus tenuis (Walcott) from the Burgess Shale. Top -- individual specimens within and outside their tubes. Bottom -- Close-up of a specimen within its tube. Credit: Marianne Collins

"It's astonishing how similar Spartobranchus tenuis fossils are to modern day acorn worms, except that they also formed fibrous tubes." The tubes provide a key missing link that connects the two main hemichordate groups. "The explosive radiation of graptolites in the Paleozoic planktonic ecosystems is known only from the diversity of their tubes. Our findings suggest that the tubes were lost in the lineage leading to modern day enteropneusts, but elaborated on in graptolites and retained to the present day in pterobranchs" added Cameron.

Hemichordates also share many of the same characteristics as chordates – a group of animals that includes humans – with the name hemichordate roughly translating to 'half a chordate.'

Undescribed species of a modern enteropneust (ptychoderid) worm. The proboscis is to the left. The total length of a relaxed and uncoiled animal is approximately 88 mm. Credit: C.B. Cameron, Université de Montréal.

"Work from my lab has shown that enteropneusts filter feed using a pharynx perforated with gill slits, just like the invertebrate chordates" added Cameron. Spartobranchus tenuis probably fed on small particles of matter filtered from the seawater. "There are thousands of specimens at the Walcott Quarry in Yoho National Park, so it's possible Spartobranchus tenuis may have played an important role in moving carbon from the water column to the sediment in the early environment" said Cameron.

Detailed analysis suggests Spartobranchus tenuis had a flexible body consisting of a short proboscis, collar and narrow elongate trunk terminating in a bulbous structure, which may have served as an anchor. The largest complete specimens examined were 10 centimetres long with the proboscis accounting for about half a centimetre. A large proportion of these worms was preserved in tubes, of which some were branched, suggesting the tubes were used as a dwelling structure.

Other members of the Spartobranchus tenuis research team are lead author Jean-Bernard Caron of the Royal Ontario Museum and Simon Conway Morris of the University of Cambridge.

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More information: The study, entitled "Tubicolous enteropneusts from the Cambrian period", is available at www.nature.com as of March 13.

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User comments : 14

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philw1776
1.5 / 5 (8) Mar 13, 2013
I will not comment on the uses these poor creatures would be subjected to were they to appear in the modern world.

Read more at: http://phys.org/n...html#jCp
El_Nose
5 / 5 (3) Mar 13, 2013
... they are in the modern world ...

http://en.wikiped...orn_worm
VendicarE
2.8 / 5 (12) Mar 13, 2013
Finally fossil evidence of the First Libertarians.

Where is RyggTard? Did someone steal his family photo album?
ziphead
1.4 / 5 (10) Mar 13, 2013
Finally fossil evidence of the First Libertarians.

Where is RyggTard? Did someone steal his family photo album?


If the creature like that did not spit the dummy many moons ago, where would you be Dickarian? :)

Or are you Lenjin's clone?
VendicarE
2.7 / 5 (7) Mar 13, 2013
Sadly ziphead's response tells us much about what Libertarians and Randites really think of women.

"spit the dummy" - Ziphead

"Or are you Lenjin's clone?" - Ziphead

I'm not sure how you go from ancient phallus shaped Libertarians to Lenjin, and splitting women, but it is a fascinating exploration of the mental damage caused by Libertarian/Randite thinking.

Tell us more.
EyeNStein
1.5 / 5 (8) Mar 14, 2013
The headline is misleading. It hardly pushes back the entire fosil record, just for this type of multi-cellular creature.
The 3.5 Billion year complete fossil record is largely untouched.
humy
not rated yet Mar 14, 2013
That has just got to be the most ugliest missing link I have ever seen!
It looks suspiciously like male genitalia but with something really horribly wrong with it.
El_Nose
not rated yet Mar 14, 2013
@humy speak for yourself
Phil DePayne
1 / 5 (6) Mar 14, 2013
Remarkable example of Lamarckian evolution! Quite astounding!
ziphead
1 / 5 (5) Mar 14, 2013

Tell us more.


You are the idiotic analogy initiator; share the blame.

Or are libertarians also responsible for making you say stupid yet strangely predictable things that get you booted off forum every so often?

Wanna talk damaged minds? Seriously? Look at your track record in here.
VendicarE
5 / 5 (1) Mar 14, 2013
Zipperhead seems to be a very angry man. I suspect that hate is what has caused his loathsome comments regarding women.

He smells Libertarian to me.
Torbjorn_Larsson_OM
5 / 5 (1) Mar 17, 2013
I, for one, welcome our Cambrian explosion hemisemidemi-clad Overworms!

But I don't welcome irrelevant politics on a phylogeny post. Can the worms.

@ENS: Context says it is "pushes [relevant part of the] fossil record".

I think the non-existent "missing link" claim is worse. Unpacking what you undoubtedly already know: It is a transitional form, sure. But it was never "missing" nor a "link". (It is unlikely to be directly related to the extant species.)

@PDP: "example of Lamarckian evolution".

Claim in need of reference.
Phil DePayne
1 / 5 (5) Mar 17, 2013
Of course; the organism evolved such a form out of habit - passing this bad habit on to its progeny
Isaacsname
not rated yet Mar 17, 2013
I'm just here for the dick jokes.

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