Archive for April, 2008

Enigmatic Triassic Hellasaur Thursday – part the fifth or so… Outcopping again

24 April 2008

I was in fact hoping to blog about the enigmaticist hellasaur of them all, but I took an unexpected trip to the Berkeley MVZ yesterday and spent all day squinting at squamate skulls and now there is this recently deceased meter+ long water monitor thawing in the fume hood and I have this huge seastar/snail ecology dataset to analyze and we had this freak freeze that killed half of our tomato plants and…well I could go on, but I’ll spare you.

Never fear however! I’ve picked a only marginally less enigmatic hellasaur to introduce you to, one which has the decided advantage of being rather poorly known and very lightly published about.

Vancleavea osteoderm from Parker and Irmis (2005).

Vancleavea campi is largely known from isolated bony plates (osteoderms) like that shown in the picture above. A handful of partial skeletons are known, but they have yet to be fully described. Hopefully this will change soon and we’ll finally have an answer to the burning question of whether this creature was a kickass archosauriform or merely a lame old archosauromorph.

Here’s what we know about Vancleavea at present:

  1. About 220 million years ago or so, it was skulking around the floodplains of Southwest Laurentia that have since become the famous Chinle Formation–stomping grounds of the infamous non-hellasaur Coelophysis and, more recently, Georgia O’Keefe.
  2. Judging from the bony-plates and skeleton it probably looked kinda crocodiley, and judging from the teeth and skeleton it may have led a similar lifestyle (i.e. a semiaquatic predator).

And now to follow the grand Enigmatic Triassic Hellasaur tradition here are some pictures ganked from the Hairy Museum of Natural History showing an artist’s rather Hensenesque reconstruction of Vancleavea.

Vancleavea reconstruction by Phil Bircheff – Photo Matt Celeskey.

See you next week, I have a monitor to skin…

refs-

Parker, William G. and Randall B. Irmis 2005 “Advances in Late Triassic Paleontology based on new material from Petrified Forest National Park, Arizona” in Vertebrate Paleontology in Arizona New Mexico Museum of Natural History and Science Bulletin No. 29. Heckert, AB, and Lucas, SG, eds. [pdf]

Enigmatic Triassic Hellasaur Thursday: Part the, um fourth?, Kyrgyz Kameleon

17 April 2008

If you’re hoping to make it into the fossil record, being a small, arboreal insectivore is probably not the best way to go. Forest soils are veritable compost heaps: acidic and crawling with critters and fungi that would happily mill your remains to humus given half a chance. And your scrawny, flexible skeleton is highly unlikely to endure the vicissitudes of long distance transport to some more suitable sedimentary environment.

Of course if you’re reading this blog chances are good that you’ve already been born so it may be too late to fix this. But don’t worry–there is a back up plan: find a lake, and fall in. Hey, it worked for Longisquama and Sharovipteryx, though a case could be made that they would have saved everyone a lot of trouble if they had just rotted on the forest floor like a respectable forest dweller.

Landsat

The Triassic Madygen Formation of Kyrgyzstan is among the most important sources of Triassic insect fossils in the world (Fraser 2006). In fact, I’d almost rather write about the titanoptera, an “enigmatic” insect group which included the 30-cm wing-spanned Gigatitan vulgaris that may have looked something like the result of an unholy love-affair between a coackroach and a mantis…on crack. But this is “Hellasaur” Thursday so I’d better stay focused.

Left: LANDSAT image of Madygen Formation outcrops – de.wikipedia

In fact, it was the search for insect fossils that led to the discovery of two the Triassic’s more problematic hellasaurs. The first, Sharovipteryx mirabilis, is bad enough, what with its bizarre hind-limb “delta wing” and its purported link to pterosaur evolution despite its patagium-backward construction. We’ll leave Sharovipteryx be for now because our topic at hand is going to require the full bottle of Excedrin.

Longisquama insignis type specimen.

Behold, Longisquama insignis, “remarkably long-scaled” as the rather prosaic scientific name would have it. “Remarkable” is certainly *one* way to describe Longisquama. Whether the protarded 10 to 15 cm long structures which appear to project from its back are scales is (as Zach noted in the comment to a previous post) up for debate.

Some argue that the strange frond-like structures are the foliage of some unknown plant. They do look vaguely vegetative, although other plant matter on the slab appears to show a very different style of preservation and Fraser notes that they have “a peculiar venation pattern that is inconsistent with any known Triassic foliage types. The structures certainly appear to be physically associated with the skeleton itself, and most who have examined the fossil seem to accept that they belong to the skeleton, though the ‘consensus’ ends abruptly there.

One camp holds that they are feathers (which are, of course, modified scales) (Jones et al. 2000)! If this were true it might seriously upset the notion that birds are derived theropod dinosaurs. However, this view is a decided minority and a vast array of other skeletal evidence as well as the preservation of far more convincing feathers on some theropod fossils weigh heavily in favor of the birds-as-dinosaurs hypothesis. That is, unless maniraptoran theropod “dinosaurs” are secondarily flightless birds that merely look like dinosaurs….

Oregon State University

Anyway, if the nature of these structures remains contentious, then establishing their function has basically been an interpretive free-for-all. A number of authors have tried to turn them into a parachuting or gliding apparatus of some sort. However, unless they supported a membrane, or were filled with helium, it’s hard to imagine how this would have worked. That said, a recent phylogenetic analysis suggests Longisquama may have been closely related to Coelurosauravus a Permian diapsid with a slightly more (though perhaps not altogether) convincing gliding membrane projecting from its sides.

Left: Longisquama as plumulus glider – Oregon State University.

Display –either to attract mates or perhaps to scare off potential predators or intraspecific rivals—is another popular explanation and probably a more convincing one. Elongate plumes in birds are exclusively a sexual selection affair; in fact their value as a sexual symbol may be directly linked to their hindrance to locomotion.

Scissor-tailed FlycatcherTyrannus forficatus

Another, admittedly fanciful, scenario is that the resemblance to a plant frond is not-coincidental. Could the scales of Longisquama be some extreme cryptic adaptation? Perhaps they hid the animal from predators or provided cover allowing Longisquama to ambush its supposed insect prey? Structural mimicry of plants is rampant among arthropods and in addition to more familiar cryptic coloration patterns, a number of land vertebrates use posturing as well as modified skin surfaces to blend into their surroundings

While sexual advertising and cryptic camouflage would appear to be at odds with one another there are animals well-equipped for both. Notably, for our purposes, chameleons, who are at once exceptionally cryptic and at the same time often sport elaborate sexual signaling structures like horns and crests. While chameleons probably don’t adjust their colors to match their background as popularly believed, color switching does allow them to temporarily display their mood to another individual then switch back to their more cryptic “normal” coloration when the mood has passed.

Oregon State University

To continue our cautious, chameleon-like walk out on a very thin limb, it’s interesting to note that Longisquama’s skull, as figured by Senter (2004) (shown left), bears a remarkable superficial similarity to that of a chameleon [Note that other, very bird-like reconstructions of the skull out there are probably inaccurate, especially with regards to the supposed antorbital fenestra which is likely a preservational artifact]. The skull of Longisquama’s cousin Coelurosauravus is perhaps even more chameleon like. I’m not prepared to make an argument for functional convergence here, but to me the resemblance is quite striking.


Longisquama by Matt Celeskey

Longisquama is certainly not closely related to chameleons, but its probable close relatives the enigmatic hellasaurs known as drepanosaurs, have been inferred to have had a chameleon-esque lifestyle. One wonders if this interpretation might be extended to Longisquama. Was it lurking in the Triassic treetops, flashing chromatophoric signals across its crazy dorsal scales and snagging titanopterans with a ballistic tongue?

Left: Longisquama by Matt Celeskey

Or, have I just been out in the sun to long?

refs-

Fraser, Nicholas 2006. Dawn of the Dinosaurs Indiana University Press

Jones, Terry D. et al. 2000. “Non-avian Feathers in a Late Triassic Archosaur.” Science 23 June 2000:
Vol. 288. no. 5474, pp. 2202 – 2205 DOI: 10.1126/science.288.5474.2202

Senter, Phil 2004. “Phylogeny of Drepanosauridae (Reptilia: Diapsida).” Journal of Systematic Palaeontology 2: 257-268 DOI: 10.1017/S1477201904001427

Enigmatic Hellasaur Thursday, er Friday, er whatever…

11 April 2008

Raeticodactylus as played by Bela Lugosi, as seen at the newly revamped Hairy Museum of Natural History.

I mean, is anyone really surprised? It’s taken me almost two years to thrash myself halfway through a measly list of 10 beautiful birds, what were the chances that I might actually be able to successfully kick off a weekly feature?

So, it turns out, bizarrely, that I actually have a lot more to say about Longisquama than I thought, despite the fact that everyone and their mom has speculated the crap out of it already. So, look for the dreadfully detailed post next week…I guess.

In the meanwhile I wanted to flesh out that crack about Raeticodactylus, preying on baby placodonts. I know you all thought I was kidding…but check out this quote from Giovanni Pinna (1991).

As happens for living young sea turtles, young placodonts were caught by pterosaurs on the seashore after they had hatched In this way it is possible to explain the early ossification of the armour that occurs in the representatives of the species, in contrast with the slower [i.e. later] armours’ ossification that occours [sic] in earlyer [sic] species living in times lacking in flying reptiles.

Pterosaurs prey on living sea turtles!? Okay, okay, I know he’s analogizing to gulls or whatever, but still I began flipping about madly trying to find some concrete evidence for this scenario…Then I stumbled across the disclaimer which I had somehow missed on the previous page:

“The following reconstruction is obviously highly hypothetical and incomplete…”

Ah ha…

Still, maybe there’s something to it. While I’m basically desperate to turn Eudimorphodon into an insectivore, we apparently have some good evidence that it was probably foraging in the marine realm (e.g. fish scales in the gut). The qunti-cuspid teeth of Raeticodactylus don’t look especially piscivorous to me (though neither do those of Eudimorphodon so, shows what I know), but maybe they would have been good for crunching through fish covered with heavily ossified scales. And they actually do kinda look like a baby “walrus-turtle’s” worst nightmare…if you squint just so.

In fact, why not, I’ll go one further and assert that the nasal protuberance and the bizarre ventrally deflected retroarticular process are adaptations for excavating buried placodont nests to get at the eggs. Hey man, put those eyebrows down. You wanna take this outside?

And watch this: for bonus points, I think we just solved the mystery of what juvenile Tanystropheus was eating too…hanging out on the shore crunching on baby placo-nuts till it was ready to swim with the big boys.

Snap!

Reference:

Pinna, G. 1991 “The norian reptiles of northern Italy” in Evolution, Ecology and Biogeography of the Triassic Reptiles edited by Mazin and Pinna.

Enigmatic Triassic Hellasaur Thursday…wait, what day is it?

9 April 2008

LOL! j/k but, seriously what the eff was Raeticodactylus chomping with those whackjob quinticuspid teeth? Um, doy! Baby placodonts!

Sorry.

POSTSCRIPTO!

Turns out the feet may have been involved too, we await further details….

Totally Tubular!

7 April 2008

…with apologies to my former classmate Daniel Garson

So, I was going to spend the afternoon creating a logo for Bloggers Half-Assedly Opining about Peer Reviewed Research Even Though Nobody Asked Them in the First Place (or BH-AOPR2ETNATFP) but I decided to devote the time to making this kick-ass band logo instead!

Of course that’s not going to stop me from posting the latest entry in our occasional series where I hastily comment on a slightly stale arm-waving brevium and then we sit back and wait for Catalogue of Organisms’ own Christopher Taylor to come along and straighten us out.

This week we take on Droser and Gehling (2008). Their brief report “Synchronous Aggregate Growth in an Abundant New Ediacaran Tubular Organism” appeared in Science a few weeks ago although, judging from the popular press accounts at least (which, of course are invariably cut-and-paste jobs from the University PR release) might have been better titled “Ropey Sea-Creatures were Sexing it up 570 million years ago…I swear!” From the press release:

Droser and Gehling observed that Funisia appears as 30 cm-long tubes in the fossils. They also observed that the tubes commonly occur in closely-packed groups of five to fifteen individuals, displaying a pattern of propagation that often accompanies animal sexual reproduction.

“In general, individuals of an organism grow close to each other, in part, to ensure reproductive success,” said Droser, the first author of the research paper and the chair of the Department of Earth Sciences. “In Funisia, we are very likely seeing sexual reproduction in Earth’s early ecosystem – possibly the very first instance of sexual reproduction in animals on our planet.

Um, okay, that’s a pretty freaking bold claim. Well, first off, as Larry Moran notes, bacteria do it, yeast do it, even educated peas do it, so sex itself is certainly a larger, longer, deeper and much slimier affair than might be given by an overly credulous reading of that quote. But even accepting for a moment Dr. Droser’s “animal” caveat lets review the evidence shall we?

Funisia fossils from Droser and Gehling 2008

First, the authors noted the occurrence of dense clusters of this tubular problematicon which they interpret as “spat falls”, e.g. multiple individuals which settled onto a substrate after planktonic larval dispersal around the same time. In modern organisms the formation of these aggregations are sometimes seen as a reproductive strategy. Animals which spend their adult life attached to the bottom improve their chances of finding a matching gamete for the sperm or egg they dump into the sea by being close to a member of the opposite sex.

Then they make a logical leap:

Among living organisms, spat production is almost ubiquitously the result of sexual reproduction but is known to occur rarely in association with asexual reproduction. (Droser and Gehling 2008)

That might be compelling circumstantial evidence, if we had any clue what Funisia was. However, like most other Ediacaran animals Funisia might as well be jam on toast for all we know about it’s ecology, life history or evolutionary relationships. Did that make any sense? Good. The author’s themselves note:

The phylogenetic affinity of F. dorothea is problematic. The morphology is consistent throughout all well-preserved specimens and serial units are a 3D character rather than features of external ornamentation. However, the lack of evidence for polypoid openings or pores in the body wall limits our understanding of its taxonomic affinities. Although it is difficult to place these fossils within Metazoa, the morphology and ecology are suggestive of stem-group cnidarians or poriferans.

Speaking of cnidarians…the first thing I thought of when I read the paper was Anthopleura elegantissima the so called “aggregating anemone.” While Anthopleura is capable of sexual and asexual reproduction it forms dense mats of asexually cloned individuals. Perhaps “spat” like clustering of similarly sized individuals isn’t necessarily linked to sexual reproduction.

At any rate, any insight into the Ediacaran ecosystem, however provisional, is certainly significant. Unfortunately, once again a University PR department eager for novelty and newsworthiness has muddied the water around a thought-provoking paper and fed more fuel to the “those crazy paleontologists what will they prove/disprove next?!” fire.

Droser, ML and JG Gehling 2008 – Synchronous Aggregate Growth in an Abundant New Ediacaran Tubular Organism — Science 319:5870 1660-1662

Enigmatic Triassic Hellasaur Thursday – Part the first

3 April 2008

The Triassic Period (ca. 250 – 200 million years ago) is familiar to most as the “dawn of the Age of Dinosaurs.” It’s true that the first dinosaurs appeared in the Triassic, along with a staggering number of other familiar animal groups including turtles, “modern” amphibians (lissamphibians), “modern” sharks (neoselachians), pterosaurs, lizards, mammals, “modern” corals (scleractinians), several important plankton lineages (coccolithophores, radiolarians, possibly diatoms) and I could go on and on.

But Triassic ecosystems were also filled a variety of ridiculous, absurd and downright protarded creatures that would (and probably have) make Dougal Dixon weep. In the technical literature these bizarre animals, frequently of dubious affinity, are often saddled with the diplomatic label “enigmatic.” Enigmatic, you know, like your cousin Larry with all of the Happy Meal toys in their original wrappers.

Starting, uh I guess next week (kinda boxed myself in with the series title there didn’t I?), we’ll take a closer look at some of these creatures. Beginning with this jaunty fellow:

Woah.

1 April 2008

Crazy story in Science Daily today about a paper recently published in the Bulletin of the Society of Historical Integrative Tautology. The paper describes Protardosuchus incendiensis, an extinct fossil reptile whose remains were recently discovered in Holocene beach sands outside San Francisco.

The authors suggest that the strange hollow, procumbent dentition were able to expel a pair of reactive fluids which, when mixed together in the presence of atmospheric oxygen would combust. Abundant charcoal in the beach sediments which yielded the sub-fossil are seen as strong circumstantial evidence for this novel adaptation.

Some carabid beetles have developed a similar, though scaled down chemical defense mechanism while among reptiles, a number of species of cobra can spray venom from their fangs. Protardosuchus’ pyrotechnic display was apparently far more impressive. As the Science Daily piece notes, the author’s aren’t certain if this behavior was defensive or related to prey-capture:

“Seriously, dude we have no effing clue,” says Melchior Neumayr, lead researcher on the new study. “It was probably all like ‘fffshhhh’ and then all like ‘BOUSCH!’ And then, then you’re like totally toast brohan. No thanks man, thanks, but no thanks.”

Most interestingly, this discovery marks the first post-Cretaceous occurrence of a hellasaurid hellasauroid hellasauriform in North America (while most authorities consider “Ogopogo” to be a “hellasaur” sensu lato, it’s almost certainly not a true hellasauroid). It’s tempting to imagine that the mythical “dragons” of Eurasian folklore were inspired by extinct old-world protardosuchians whose remains have yet to be discovered. In fact this pan-Pacific distribution would almost certainly confirm McCarthy’s (2003) argument that the Pacific basin didn’t open until the Mesozoic. Dude, seriously.

andrew-attacked.jpg
An artist’s reconstruction of Protardosuchus.
Refs:
Dennis McCarthy (2003) “The trans-Pacific zipper effect: disjunct sister taxa and matching geological outlines that link the Pacific margins” Journal of Biogeography 30 (10)
Neumayr, M et al. (2008) “Expirational autocombustion in a recently extinct Hellasaur from coastal California” Bull. Soc. Hist. Int. Taut. 56 (9 or 10)