Nectocaris Update

26 05 2010

Good tidings and well-wishes!

Last week, I leant some coverage to the bizarre little Burgess Shale creature Nectocaris pteryx. At the time, all of the publicly-available information about the species maintained that

A) Its known from but a single specimen.

B) Postcranially, Nectocaris was a sinuous, chordate-like creature.

However, shortly after my article was published, everyone’s favorite stuffed theropod pointed out that a pair of Burgess Shale scientists (The University Of Toronto’s Martin Smith & Jean-Bernard Caron) had argued that Nectocaris was, in fact, the earliest-known cephalopod and were working on a paper to this end. Evidently, the pair had stumbled upon NINETY-ONE additional specimens such as the one below:

That paper was released today, and the results have dramatically altered our perceptions of what this beast looked like. Ed Young of the brilliant blog “Not Exactly Rocket Science” has the scoop.

For those too lazy to click on the link to my earlier post, here’s a traditional reconstruction of Nectocaris as derived from the genus’ first and, for several decades, solitary specimen:

And here’s the updated reconstruction based on this wealth of newfound material:

I think it’s fairly obvious to say that this isn’t merely some miniscule alteration: it radically changes everything we thought we knew about this creature’s anatomy and phylogeny. To quote Mr. Young:

“Around four centimetres in length, Nectocaris had a soft, flattened, kite-shaped body with two fins running down its sides. Its small head was adorned with two long tentacles and two stalked eyes. Unlike the compound eyes that were common among Cambrian animals, probably had the camera-like structure that modern cephalopods use. From its neck protruded a flexible funnel, which opened into an internal cavity containing pairs of gills.

The funnel lay behind some of the earlier confusion about Nectocaris. In the original specimen, it was flattened so that it looked like a shield-like plate behind the eyes, reminscent of a crustacean’s body armour. The new specimens put paid to that interpretation. The structure is clearly a funnel, similar to those used by modern cephalopods. Nectocaris probably used it to swim the same way, giving it an extra boost of jet propulsion to complement the beating of its large fins.”

The homogeneous lack of shells throughout the newfound Nectocaris specimens have shattered the notion that cephalopods evolved from Monoplacophorans: an assertion which largely rested upon the fact that the earliest known representatives of this tentacled group had previously been the nautiloids. Evidently, the shells which graced several groups and species of subsequent (and current) cephalopods evolved independantly.

However, not every gap has been filled in assigning Nectocaris to this new role: none of the fossils appear to display the intimidating beak-like mouth and horny tongue (known scientifically as the ‘radula’) of squids, octopi, and their kin remains, as far as the authors can ascertain, absent from N. pteryx. The radula is of particular importance due to its presence in nearly every group of modern mollusks and has hence become a uniting feature.

Regardless of what Nectocaris’ true relations may be, this news provides yet another example of how fossilized species with which the scientific community feels it’s somewhat familiar can drastically suprise its members almost instantaneously by way of new discoveries (or even, in some cases, a second trip through the archives).

A POINT TO CONSIDER: How much time will elapse before PZ Meyers jumps all over this story?

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3 responses

26 05 2010
Thomas R. Holtz, Jr.

Having seen the paper, I’m not sure that they are entirely right in a cephalopod placement for this critter and its relatives. I think one can make the case that this is a poorly-mineralized anomalocaridid-relative, with the “fins” being homologs to the lateral flaps and the “siphon” being a homolog to the central mouth-ring.

Still, awesomely weird.

26 05 2010
tanystropheus

Intriguing… It’s times like these when I wish I could afford subscriptions to all these bloody online journals!

I fully realize that, given these financial surcumstances, I have but one photograph of the new specimens. Nevertheless, based upon this document, I don’t really see much similarity between the short, multitudinous rods exhibited along the creature’s sides and the wide, angular lateral flaps of the anomalocaridids.

Again, however, I could easily be totally wrong about this due to my present lack of information…

29 05 2010
Burgess Shale Extravaganza: Nectocaris « The Theatrical Tanystropheus

[…] NOTE: Much of the information contained in this article has been effectively rendered out-dated by a very recent discovery. Click here to find out why. […]

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