Laelaps

ResearchBlogging.org

When it comes to aliens, Hollywood really does not have much imagination. Most extraterrestrials that have appeared on the big screen look very much like us, or are at least some kind of four-to-six-limbed vertebrate, and this says more about out own vanity than anything else. It would be far more interesting, I think, to take the weird and wonderful organisms of the Cambrian as inspiration for alien life forms, and two new critters have just been added to the odd Cambrian menagerie.

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A restoration of Herpetogaster collinsi by Marianne Collins. From Caron et al, 2010.

What was three centimeters long, had bilateral symmetry, and grew tentacles out of its head? According to paleontologists Jean-Bernard Caron, Simon Conway Morris, Degan Shu, it was Herpetogaster collinsi, the latest fossil to be named from the famous 505 million year old Burgess Shale of Canada. As described in PLoS One, this small invertebrate may have attached itself to sponges by way of a structure called a stolon, and there it waited for tiny prey to drift into its tentacles. The fact that so many have been found in close association suggests that they often lived in close proximity, so perhaps sponges were the hot hangout for this strange suspension feeder.

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Hypothetical positions of Herpetogaster collinsi and its relatives to other organisms. From Caron et al, 2010.

But just what kind of animal was Herpetogaster? It shows some resemblance to both an enigmatic Cambrian animal from China’s Chengjiang fauna named Phlogites and members of another group called eldoniids, but this is not especially helpful since these previously-known forms have been just as tricky to interpret. According to Caron, Conway Morris, and Shu Herpetogaster and its relatives could be closely related to echinoderms (sea stars, sandollars, and the like), hemichordates (worm-like organisms such as acorn worms), or then then again may be close to the common ancestor of both groups. At present it is difficult to test these competing hypotheses, but regardless of where Herpetogaster ultimately falls in the evolutionary tree it was certainly a fantastic creature.

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Two computer-generated restorations of Kiisortoqia soperi (above- a view of its underside; below-a view from the side). From Stein, 2010.

The other newly-announced Cambrian creature, described by Martin Stein in the Zoological Journal of the Linnean Society, is quite different from the small suspension feeders scrutinized by Caron and colleagues. Found in the Early Cambrian (~540-510 million years ago) rocks of North Greenland, Kiisortoqia soperi was an arthropod with a simple head shield, a segmented body, and two long appendages sticking out in front of it. As bizarre as it was, however, Kiisortoqia had affinities to both “true” arthropods and a group of marine predators called anomalocaridids, all of which had modified versions of the same grasping appendages. As yet the exact feeding habits of Kiisortoqia are unclear, but if it was anything like its relatives it probably snatched prey out of the water with its appendages. The spikes along the structures would have helped to impale prey, and as they coiled around the food item it would have been brought back to the mouth of Kiisortoqia.

Caron, J., Conway Morris, S., & Shu, D. (2010). Tentaculate Fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) Interpreted as Primitive Deuterostomes PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009586

STEIN, M. (2010). A new arthropod from the Early Cambrian of North Greenland, with a ‘great appendage’-like antennula Zoological Journal of the Linnean Society, 158 (3), 477-500 DOI: 10.1111/j.1096-3642.2009.00562.x

Comments

  1. #1 Canadian Curmudgeon
    March 12, 2010

    Always fascinating and demonstrating how out of date my 18 year old course invertebrate phylogeny is.

    Also, the perennial juvenile mind quickly jumps to the evolutionary advantages if human males had developed appendages such as this. Would have had extreme negative effects on the sex-toy industry.

  2. #2 Lenoxus
    March 12, 2010

    To be fair to Hollywood, it’s maybe not so much vanity as lack of imagination (and lack of Cambrian actors for the rubber suits and motion capture).

    Regarding the new finds, remember this: If you can’t place those creatures on the phylogenetic tree in the next thirty minutes, that means evolutionary biology is overturned once and for all.

  3. #3 Laelaps
    March 12, 2010

    Sometimes a cambroernid is just a cambroernid.

  4. #4 iambilly
    March 12, 2010

    Regarding the new finds, remember this: If you can’t place those creatures on the phylogenetic tree in the next thirty minutes, that means evolutionary biology is overturned once and for all.

    Herpetogaster collinsi carries its own tree with it.

    I also had a Freudian (and juvenile) response to the life restoration of H. collinsi.

  5. #5 Jared
    March 12, 2010

    Anomalocaridids are a really cool group of predators… “weird shrimp” indeed does not do justice to how strange these creatures really were. I picture them moving and swimming slowly like squid or cuttle fish while not using the siphon, just hovering and looking for organisms in the sediment with vision similar to that of the mantis shrimp…

    Sorry for the digression, I actually had a comment on the actual post which was derailed at the mention of Kiisortoqia soperi being similar to anomalocaridids.

    What, exactly, are the similarities between Kiisortoqia soperi and anomalocaridids? I’d read the paper myself, but I don’t have access…

    Tangentially, a well done PLoS ONE article always makes me happy.

  6. #6 Laelaps
    March 12, 2010

    Jared; The main point of resemblance discussed in the paper are the “great appendages” at the front of the body. Martin writes:

    The antennula of K. soperi gen. et sp. nov. share with the ‘great appendages’ of Anomalocaris saron and Amplectobelua symbrachiata, the composition of the peduncle, and about 15 massive, podomere-like articles armed with paired spines. The spines are more delicate in K. soperi gen. et sp. nov., and appear to be simple, whereas Anomalocaris canadensis and Anomalocaris saron have prong-like spines. The spine morphology seems, therefore, to be more plesiomorphic, yet the overall similarity is taken as a support for the homology of the structures.

    I will e-mail you the paper, as well.

  7. #7 Sven DiMilo
    March 12, 2010

    Very cool; thanks, Brian.

    Does anyone know whether the “great appendages” are still considered possibly homologous to chelicerae?

  8. #8 Laelaps
    March 12, 2010

    Sven; Yes, according to Stein that is still an open hypothesis. The paper states (references expunged for ease of reading):

    “In megacheirans, the ‘short great appendage’ pair is
    the most anterior of the four limb pairs incorporated
    into a simple head shield. Where eyes are known, they occur anterior to the ‘short great appendage’, and all limbs posterior to the ‘short great appendage’ are biramous. This configuration exactly mirrors the euarthropod head composition, and it is therefore most reasonable to assume homology between the ‘short great appendage’ and the deutocerebral antennula of Crustacea, and the chelicera of
    Chelicerata.”

    If the “great appendages” of anomalocaridids are homologous with the “short great appendage”, then both may be homologous with chelicera and atennula (in the appropriate invert groups above noted).

  9. #9 Lars Dietz
    March 12, 2010

    Sven: Yes, the new paper supports this idea. Chelicerae/chelifores are now generally thought to be homologous to the first antenna (antennula) of crustaceans, which is also the insect antenna. So if the great appendage is homologous to the antennula, it also is homologous to the chelicera. Stein notes in the paper that there are actually two kinds of “great appendage”, one in anomalocarids and the other one (the raptorial “short great appendage”) in the Megacheira (e. g. Yohoia, Leanchoilia), which are probably stem-group chelicerates.

  10. #10 Lars Dietz
    March 12, 2010

    Sorry, Brian’s comment hadn’t appeared yet when I started writing mine.

  11. #11 Lars Dietz
    March 12, 2010
  12. #12 Eric
    March 12, 2010

    This is pretty cool.

    Reminds me of the Cambrian exhibit at Tyrell.

  13. #13 Jared
    March 12, 2010

    Got it, thanks.

  14. #14 Jon H
    March 12, 2010

    Herpetogaster, common name: “Penis Fern”

  15. #15 Luna_the_cat
    March 12, 2010

    I have to admit, my thought was, “oh, a penis-maggot with parsley!”

    Thank you for this. It brightens my day, and gives me new fodder for weird-ass nightmares.

  16. #16 Thomas R.
    March 12, 2010

    What really catches my eye in this piece is the first guy, H. collinsi. What exactly is he? Was he a sort of transitional between sedentary tunicates and free-swimming creatures? Did he occupy the niche that sea anenomes do?

  17. #17 Jared
    March 12, 2010

    Thomas, as I point out to many people, many species undergo more transition during development than we often consider… For example, Hydra developmental stages differ considerably. Another example are the tunicates have a notochord as juveniles, but most species lose this as adults.

    Oh, and yes, it does look like a one-legged penis-maggot with parsley…

  18. #18 Monado, FCD
    March 13, 2010

    This is just a sample of divine frontloading so that you’ll be ready with an answer when a creationist asks why he’s never seen a carrot-shrimp!

  19. #19 Glendon Mellow
    March 13, 2010

    Awwwesome!

    Marianne Collins artwork is really nice. The Herpetogaster almost looks like it’s performing a sexual display. Like a peacock.

  20. #20 Andreas Johansson
    March 15, 2010

    I must be defect – the life restoration of Herpetogaster didn’t give me any dirty thoughts.

    But they’re nifty little critters – someone head over to Catalogue of Organsisms and nominate them for resurrection (I figure I’ve already done my quota with four different nominations).

    Over to the arthro’s, what’s the current view to the interrelationships of the crown group and the various “lobopodian” groups?

  21. #21 Rob Jase
    March 17, 2010

    Gould’s ‘Wonderful Life’ may be out of date but Cambrian lifeforms still appear to come from Wonderland.

  22. #22 prefabrik
    May 12, 2011

    as I know, however, this has not been done and so the show sometimes selectively matches some evidence to the story they wish to tell.

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