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.
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.
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.
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
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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.
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.
Sometimes a cambroernid is just a cambroernid.
Herpetogaster collinsi carries its own tree with it.
I also had a Freudian (and juvenile) response to the life restoration of H. collinsi.
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.
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 âgreat appendagesâ 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.
Very cool; thanks, Brian.
Does anyone know whether the "great appendages" are still considered possibly homologous to chelicerae?
Sven; Yes, according to Stein that is still an open hypothesis. The paper states (references expunged for ease of reading):
"In megacheirans, the âshort great appendageâ 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 âshort great appendageâ, and all limbs posterior to the âshort great appendageâ are biramous. This configuration exactly mirrors the euarthropod head composition, and it is therefore most reasonable to assume homology between the âshort great appendageâ 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).
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.
Sorry, Brian's comment hadn't appeared yet when I started writing mine.
By the way, the paper is freely available here:
http://www.core-orsten-research.de/Publications/PDFs%20der%20Paper/pape…
This is pretty cool.
Reminds me of the Cambrian exhibit at Tyrell.
Got it, thanks.
Herpetogaster, common name: "Penis Fern"
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.
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?
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...
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!
Awwwesome!
Marianne Collins artwork is really nice. The Herpetogaster almost looks like it's performing a sexual display. Like a peacock.
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?
Gould's 'Wonderful Life' may be out of date but Cambrian lifeforms still appear to come from Wonderland.
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.