…and this is a 
Well, more like great-great-many-times-great-aunt of all squid, but it's still a spectacular fossil. Behold the Cambrian mollusc, Nectocaris pteryx.
(Click for larger image)
Reconstruction of Nectocaris pteryx.
This was one of those confusing, uninterpretable Cambrian animals, represented by only one poorly preserved specimen. Now, 91 new specimens have been dug up and interpreted, and it makes sense to call it a cephalopod. It has two camera eyes — not arthropod-like compound eyes — on stalks, an axial cavity containing paired gills like the mantles of modern cephalopods, and a flexible siphon opening into that cavity. There are also subtle similarities in the structure of the connective tissue in the lateral fins. Obviously, it has a pair of tentacles; no mouthparts have been preserved, but there are hints in the form of dark deposits between the tentacles, which may be all that's left of the mouthparts — and are in the right place for a cephalopod ancestor.
There are still mysteries. There's no hint of a shell; previous theories had postulated a shelled common ancestor to squid, nautiloids, and ammonoids, but either this was a specialized branch that lost the shell, or modern cephalopod groups independently re-evolved the structure. It also has only two tentacles! Again, we don't know whether this was the ancestral condition, or whether Nectocaris is the product of a derived fusion. Known cephalopod Hox genes use a novel combinatorial scheme to encode arm identities, so I guess I wouldn't be too shocked if the eight- to ten-arm condition is a relatively recent (in geological terms!) innovation.
About that great-aunt remark…here's where their analysis places the Nectocarids, as a Cambrian side-branch of the group that led to the modern forms.
(Click for larger image)
Phylogenetic position of the nectocaridids. Arrows indicate the crown groups of 1, molluscs; 2, conchifera; 3, cephalopods. Stars represent the earliest record of mineralization in each lineage. Clade divergence times (dotted lines) are unconstrained. Early branches follow previous phylogeny.
Note the dotted lines everywhere — those are lineages that we haven't found in the fossil record yet. Nectocaris is small (about 4cm long) and softbodied, and it required excellent preservation for any trace of them to survive. Specimens from the beginning of the Cambrian, representative of the groups indicated by the red arrows at 1 and 2, would be wonderful to have…but they're also going to be forms that wouldn't have been ideal for fossilization. Clearly, we need to fund more paleontology.
Ed Yong has more to say at Not Exactly Rocket Science.
Smith MR, Caron J-B (2010) Primitive soft-bodied cephalopods from the Cambrian. Nature http://dx.doi.org/10.1038/nature09068.
Life Science
Comments
Posted by: Alan B
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May 26, 2010 4:33 PM
Does that mean the trumpet-shaped mouth piece is imagination??
Posted by: PZ Myers
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May 26, 2010 4:38 PM
The trumpet-shaped piece is a funnel, not a mouth. It's comparable to the siphon in modern cephalopods which is, again, not a mouth.
Posted by: Galactus35
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May 26, 2010 4:39 PM
Only two tendrils? It's amazing it ever got anything done.
Posted by: Glen Davidson
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May 26, 2010 4:41 PM
It's just due to an alien Venter playing around.
Whatever, it's already closer to science than IDiocy is.
Glen D
http://tinyurl.com/mxaa3p
Posted by: Biddy
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May 26, 2010 4:44 PM
Three cheers for the Burgess Shale! I saw this story on CBC this morning and knew it would be posted on Pharyngula shortly. It’s such a relief to have some science thrown in amongst all the usual stories of bat-shittery. Thanx PZ!
Posted by: The Pale Scot
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May 26, 2010 4:47 PM
I beleive that that there is Matt Taibbi's "Vampire Squid :Vampyrosachman infergoldnalis", the "blood funnel" is obvious.
Posted by: Brownian, Most Vicious & Petty of Pharyngulites
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May 26, 2010 4:47 PM
Like wearing an onion on one's belt, two appendages seemed to be the style at the time.
Posted by: Shplane, some shit in french
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May 26, 2010 4:48 PM
AHA
SO WITH THOSE DOTTED LINES, YOU ADMIT THAT EVILUTION IS FALSEHOOD, AND THAT YOU ARE EDUCATED STUPID BY THE EVIL TEACHERS OF ONE-DAY TIME!!!11one
Posted by: Happy Tentacles
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May 26, 2010 4:55 PM
So that's what my great-great-grandmother looked like!
Posted by: Silič O'Nopolitanopoulos, Färschdbischuf Beesknees aus Ulm und Klein Elguth, Elector Pharynguline.
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May 26, 2010 4:55 PM
Does this mean that I, too, can hope to one day evolve eight to ten arms?
Bugger. Shouldn't have gone for that vasectomy, then.
If any of the mad, mad women of Pharyngula a willing, the count-ess tells me there are still a coupla spermatozoa around.
Posted by: MadScientist
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May 26, 2010 5:00 PM
"novel combinatorial scheme to encode arm identities"
How can it be novel if it's millions of years old?
Posted by: Vidar
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May 26, 2010 5:41 PM
@madscientist #11
Relatively novel. We're dealing with geological time scales, and those can reach into the billions of years.
Posted by: James F
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May 26, 2010 5:52 PM
It's fascinating to think of getting from this to the 90 or so tentacles of the nautilus.
Posted by: amphiox
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May 26, 2010 5:59 PM
What's striking to me is the superficial similarity of overall shape between Nectocaris and Anomalocaris - almost like molluscan and arthopodian/lobopodian versions of the same body form.
Could there have been any convergence going on? What do we think/know about Nectocaris' niche/lifestyle? Could it have been a predator with habits similar to what we think Anomalocaris was doing?
Posted by: dactylifera
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May 26, 2010 6:15 PM
I'm speechless. That is really, really beautiful.
Posted by: monad
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May 26, 2010 6:37 PM
@amphiox #14:
I also remember reading something comparing Nectocaris to what are considered early deuterostomes, like Vetulicola from the cambrian in Chengjiang.
That interpretation came with a very different reconstruction, though. The similarities included a head shield plus dorsal and ventral fins (quite unlike Anomalocaris), which have been replaced by tentacles and a siphon.
The difference is very curious. I also wonder about concluding cephalopods developed shells separately from other mollusks - wouldn't it make more sense to suppose Nectocaris lost it separately from modern squids?
Posted by: https://www.google.com/accounts/o8/id?id=AItOawmq9IDeEH2iZb2fS43vQEv2TBHOB2IXAt8
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May 26, 2010 6:41 PM
@amphiox #14:
Tom Holtz commented on my post noting the same similarity to Anomalocaris, but Martin Smith (1st author of new paper) turned up too and put forward reasons why he rejected the anomalocarid idea. I absolutely love blogs for stuff like this.
http://blogs.discovermagazine.com/notrocketscience/2010/05/26/nectocaris-mystery-fossil-was-actually-a-500-million-year-old-squid-relative/#comment-9273
Posted by: Mattir-ritated
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May 26, 2010 6:41 PM
Another thanks for something other than creationist anti-vax idiots and oiled sealife. The right mix is essential to the sanity of your readers.
Posted by: Stephanie
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May 26, 2010 7:10 PM
how related is this to the awesome Anomalocaris? does anyone know?
Posted by: DLC
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May 26, 2010 8:41 PM
Clearly this 3000 year old specimen proves that Cephalopods are a unique Kind, and so must have been on the Ark.
Clearly, DLC is suffering from mental impairment due to a stroke. Sorry... they run in the family.
Posted by: Stanton
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May 27, 2010 12:24 AM
Does anyone have any photos or references of Nectocaris' alleged relative, Petalilium?
Posted by: Marella
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May 27, 2010 12:31 AM
Aww, that's sooo cute!
Posted by: Westcoaster
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May 27, 2010 12:32 AM
It's modern cephalopods that use the novel combinatorial schemes of Hox genes to encode arm identities, not the snazzy looking two-tenticaled version.
Posted by: shonny
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May 27, 2010 1:54 AM
One can but marvel at the need for belief and faith in superstition, when reality and its myriad of possibilities are so much more exciting!
And I guess at only 4 cm length Nectocaris can safely be termed cute. What evolved from it might be a different kettle of . . . squid?
Posted by: Fortknox
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May 27, 2010 3:08 AM
Tell me if you agree with this-
Is Rachel Maddow superstitious?
Posted by: Fortknox
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May 27, 2010 4:11 AM
I updated the topic about Rachel Maddow providing explicit example.
Is Rachel Maddow superstitious?
Posted by: hobbitjeff22369
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May 27, 2010 6:54 AM
Re: squid. What a cutie. I love the Burgess shale. I would like to know more about when and where on the locality the samples were collected.
And seriously, Fortknox, stop spamming EVERY FUCKING THREAD ON HERE.
Posted by: mmelliott01
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May 27, 2010 6:59 AM
I love Burgess Shale fauna. The display at the Field Museum in Chicago is wonderful, but I'm still holding my breath for the Smithsonian Museum of Natural History to update their very old-fashioned exhibit.
Posted by: Rorschach
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May 27, 2010 7:06 AM
Cleanup and cull not far away, I would imagine.
Posted by: David Marjanović
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May 27, 2010 8:00 AM
The convergence between this and the anomalocaridids which lived in the place at the same time is... rather... flabbergasting.
The anomalocaridids are close relatives or members of Arthropoda, depending on how you define that latter name; and arthropods and molluscs are not close relatives at all, barely closer to each other than to us.
Posted by: mikerattlesnake
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May 27, 2010 8:28 AM
It says a lot about the quality of one's content when the only way he can get attention is with GIANT RED FONT.
Posted by: https://me.yahoo.com/a/eM9vTL9_o4CJZCSF.K8OQ44rATSSaUPiRKSvcw--#4e199
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May 27, 2010 10:36 AM
Hmm...this would explain a lot about your page on Uncyclopedia...gotcha!
Posted by: brasidas
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May 27, 2010 12:14 PM
I demand an online poll to decide democratically and unscientifically whether this creature is related to anomalocaris. Here are the options:
a) Nectocaris is obviously related to anomalocaris
b) Being a poopyhead, I don't think they're related at all.
c) I'm a simpering agnostic about their relationship
Posted by: amphiox
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May 27, 2010 1:25 PM
If the proposed relationship holds up this really is an amazing example of morphological convergence with anomalocaridids, and consistent with other such examples in how the fine details diverge and betray their separate ancestries.
e.g. The eyes are both on stalks, but one is compound as typical for arthopods and the other is a camera-type, typical of cephalopds. The "arms" are segmented arthropod (biramous? not sure about that)appendages in one and a modified molluscan muscular foot in the other. One is partially segmented and calcified, the other is not. Etc.
Without the mouthparts preserved we can't know if Nectocaris could do the trilobyte flexing/cracking thing for feeding that Anomalocaris was thought to have done, but if it had anything like the beak of modern cephalods, such would be very possible. (And if it had a radula I suppose it could drill through shelled prey just like lots of modern snails do today).
Posted by: pjsouza
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May 27, 2010 2:01 PM
I'm not buying it. So the cephalopods were unshelled, developed a shell, internalized it and got rid of it again...
If one follows the stars within Conchifera, there's a different story to be told.
Also, cephalopods start with the mantle cavity almost completely occluded, then open it, then close it again?
btw, why are the monoplacophorans outisde Conchifera?
http://en.wikipedia.org/wiki/Conchifera
But whatever, monoplacophorans kick the first record of mineralization for the unnamed clade (between arrows 1 and 2) way back...
Posted by: Martin Smith
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May 27, 2010 3:08 PM
Those of you who have noted similarities between Nectocaris and anomalocaridids might also be interested in a review of convergence between cephalopods and fish, located (unfortunately behind a paywall) at http://dx.doi.org/10.1111/j.1469-185X.1972.tb00975.x.
Petalilium is (we believe) synonymous with the material described as Vetustovermis by Chen et al (2005), freely available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1559895/
And for those tempted to tell a story based on the molluscan family tree, do remember that the groupings within the molluscs are not very well resolved at all -- especially when it comes to placing the monoplacophora ( http://en.wikipedia.org/wiki/Mollusca#Phylogeny gives a brief idea of some of the uncertainty). I personally feel that molecular data suggests quite strongly that the shell evolved multiple times -- see a brief summary at http://en.wikipedia.org/wiki/Mollusc_shell#Evolution .
Posted by: amphiox
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May 27, 2010 4:17 PM
Just a random thought here, but it would seem to me that on first principles mineralized shells of the type found in molluscs would not be a very hard thing to evolve for a lineage of animals that presumably already had a mantle as one of its defining body-plan characteristics. And similarly, such shells would not be difficult to lose. The molluscan shell isn't as intimately associated with the fundamental physical structure of the animal as the exoskeleton of an arthropod, or the axial skeleton of a chordate/vertebrate, for instance.
So there's nothing a priori unlikely or unexpected about the possibility that molluscs have evolved and lost shells multiple times over their evolutionary history, in multiple lineages.
Posted by: Vidar
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May 27, 2010 5:01 PM
Maybe cepholapod evolution went something like this:
group of 4 Nectocaris: "Wonder Quadruplets Powers Activate: Take form of 8 Armed Mutant Cepholapod Octopus!"
group of 5 Nectocaris: "Oh yeah, Take this!"
Nec 1: "Tentacles!"
Nec 2: "More Tentacles!"
Nec 3: "Yet more Tentacles!"
Nec 4: "Even more Tentacles!"
Nec 5: "And even, Appendages!"
Combined cepholapod: "By your powers combined, I am CUTTLEFUSH, Defender of Squid!
Then the conquest of all parts of earth ensued, as long as it was submerged.
Posted by: pjsouza
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May 27, 2010 8:31 PM
WADR, I remain unconvinced. The similarities with anomalocaridids are too many and too evident to be dismissed as convergent, including the position of the putative siphon, and its continuation as a tube (oesophagus?) that runs through the head [supplementary fig.4]. Compare it with this:
http://www.trilobites.info/WandB1985sm.gif
And if I may be so bold as to interpret that axial cavity as the gut, and the dig (fig. 1e) as diverticula, Nectocaris becomes very similar to this:
http://www.trilobites.info/anocanrecon1.gif
But I'm only a retiring malacologist, and a rather unpublished one, but I suspect and hope that this hypothesis won't remain unchallenged by more competent colleagues. And if it stands and Nectocaris is indeed a cephalopod (or a sister-group), then cephalopod philogeny is in for a tumble.
Cheers,
Paulino
Posted by: jeff
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May 27, 2010 9:58 PM
To pjsouza:
I am also unconvinced, but I have no expertise or qualifications. I think that the changes to the reconstruction of cephalopod phylogeny are radical, and need more support. But I don't think, from the single new fossil image I've seen, that those lines match diverticulae, as seen in anomalocaridids.
I would like to see something more specific about a mouth, but if the stalked eyes are not compound, that would be pretty key against close arthropod affiliation.
Posted by: Sven DiMilo
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May 27, 2010 10:19 PM
Opinion.
What? The siphon (if that's what it is) would be connected only to the mantle cavity, not an esophagus.
Here's another perspective: As the cephalopod tentacle apparatus is derived from and homologous with the muscular foot of other mollusks, then as bilaterally symmetric animals, it makes perfect sense that the first satge in tentacle evolution was division of the foot into two bilaterally symmetrical halves, the stage that seems to have been preserved here. Loss of the shell is not that surprising in a small nektonic animal either. I have no trouble accepting it as a basal cephalopod. The similarity to anomalocaridids is superficial; the Great Appendages of anomalocaridids being arthropod appendages (perhaps homologous to chelicerae), and the tentacles of this here item being a split molluscan foot.
Or not. Who knows?
Posted by: monad
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May 27, 2010 11:07 PM
@ Martin Smith #36:
That's an interesting idea. At first glance it seems like it's really only focusing on differences, the way mouthpart details were used to argue for arthropod polyphyly, but I am certainly no expert.
Without the other data, though, it doesn't seem like this reconstruction of Nectocaris should reveal much about that one way or another. We know mollusks have lost shells several times among cephalopods and gastropods, so this works well either way.
Thank you very much for sharing about this. I, for one, will be watching for further developments.
Posted by: David Marjanović
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May 28, 2010 8:29 AM
I've got the paper now (thanks again to the first author), but still haven't read it...
That pair is not biramous.
No. There's no evidence that the nectocaridids are ancestors of anything known. They're the sister-group of the rest of Cephalopoda.
Oops. Looks like the authors forgot what "crown-group" means.
...if you lump enough clades into that horribly paraphyletic assemblage.
Never in the last few billion years has all of the Earth been submerged.
I agree – except that the current ideas about cephalopod phylogeny are hardly any better supported! For instance, it took till 200-fucking-7 till someone published a proof-of-concept paper showing their colleagues that, yes, cladistics can be done on ammonites at all. Not one professional had tried to do anything but cladistics to figure out Mesozoic dinosaur phylogeny for something like 10 years by then.
The hypotheses of cephalopod phylogeny presented by Wikipedia and its sources all strike me as scenario-based, as "cladistics with two characters". It's a mess.
Why actually? Spider eyes aren't compound either.
Posted by: pjsouza
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May 28, 2010 12:59 PM
@Sven
When one is dealing with a .5 billion year old impression of a macerated soft bodied animal, I think most of what we are dealing here are opinions at best and wild speculation at worst.
Exactly! but where is the mantle edge? this tube connects to the ventral surface of the head.
Check the supplementary info, fig. 4:
http://www.nature.com/nature/journal/v465/n7297/abs/nature09068.html#supplementary-information
You'll notice that from the posteiror end of the "siphon" there's a tube that passes through the head, and connects with the "axial cavity", that happens to be full of lateral diverticula.
This reminds me of that medical maxim "if you hear clopping down the street, don't assume it's a zebra", or a unicorn.
@David
Here's what the authors say:"we suggest that nautiloids evolved from a nonmineralized, coleoid-like ancestor related to the nectocaridids."
I think it'd be unnecessary to go into a hairsplitting exercise, at this point anyway.
What's horribly paraphyletic? Monoplacophorans or Conchifera? I agree if you are talking about the former, but not the latter. Still monoplacophorans kick mineralization for the whole clade, way back in time.
@everybody
In the end it all amounts to parsimony x sensation. I love and am susceptible to sensation just as everybody else. And just as everyone else I was elated by Gould's Wonderful Life, and the myriad of phyla it presented. Just remember Hallucigenia.
Posted by: David Marjanović
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May 28, 2010 1:24 PM
Of course.
Never forget! :-)
Posted by: Franklin Percival
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July 31, 2010 7:46 PM
Sorry folks, your words are pure poetry to me, but understanding eludes me. I'll have to go to the library to check out your terminology - and no, I have not yet trusted the inter-webby-type-thing as the final arbiter of anything. Just too old, I suppose.
Luv,
f.