Something my body needs anyway…I like that.

As you’ll note from the logo over there, this marks the first issue of “blogger half-assedly opining about peer-reviewed publications when, really no one asked in the first place anyway.”  I’ll use this logo whenever I…well you get the picture.  Feel free to borrow the logo for your own half, or even whole-assed efforts.

Invert-workers are always carping¹ about vertocentrism, and of course they have a point: tardigrades are like a gajillion times radder than tyrannosaurs and it’s a shame that Discovery Channel programming doesn’t reflect this fact.  I guess they’re busy vetting questions for Cash Cab or whatever.  But it occurs to me: it’s actually unfair to resent vertebrates as a whole for this injustice because, let’s face it, aside from lamnids no one gives a swimming crap about fish.

I know, I know, cladistically speaking, tetrapods like Sue and me are just aberrant terrestrial fish. Aside from our freakish lineage however, the silent majority of “values” vertebrates (i.e fish) might as well be ostracods for all the press attention they get.  I mean, ostracodes. Whatever.  (Actually ostracods/es have a pretty good PR person these days).

A few cases in point²: Funisia, an ediacaran with all the charisma of a sodden mop head, got major press attention thanks to some good old fashion sexing up by the media.  Likewise, Martialis heureka, the recently discovered basal ant, is already generating major buzz³ well before the peer-reviewed paper announcing the discovery has even hit the presses.  And don’t get me started about Aptostichus stephencolberti.

Meanwhile, the discovery of a new and extraordinarily bizarre fossil fish, Hsianwenia wui, announced in last week’s issue of PNAS (Chang et al. 2008), sank with less of a splash than a 49 kg Chinese diver making a perfect entry⁴.  And that’s unfortunate, because if the public has an inordinate fondness for things with hydroxylapatite endoskeletons, well Hsianwenia is about as bony as they come.

Hsianwenia (which I’m pronouncing “shee-An-Wen-ya” until someone corrects me) was discovered in Pliocene lake sediments from the Qaidam basin on the north side of the Tibetan plateau.  Hsianwenia belongs to the largest family of freshwater fishes the Cyprinidae which also includes minnows, carp and goldfish among many others.  The uplift of the Tibetan plateau over the past several million years has created multiple small, isolated lakes and waterways.  This in turn has driven the evolutionary radiation of an endemic suite of Cyprinids.  These 100 or so species in 15 genera are grouped together the subfamily Schizothoracinae, known to the more poetically-minded as “snow trout” or “snow carp” (Qi et al. 2006).

While FishBase reports that the flesh of living schizothoracines is “much relished”, eating Hsianwenia would have been a chore.  That’s because unlike its relished relatives, Hsianwenia is characterized by a peculiar thickening of the skeleton.    This “pachyostosis” is so extreme that the authors state that the bones appear to leave little room for muscle.

Hsianwenia wui from Chang et al. (2008).

While no known living fish possess a similar super-skeleton, another extinct fish, Aphanius crassicaudus—from Miocene sediments on the northern margins of the Mediterranean—apparently independently evolved extremely thick bones.  Multiple specimens from both species demonstrate that the pachyostosis is not evidence of disease or disorder, but was a natural feature in each fish.  More over, this condition was amplified through the course of ontogeny with fish becoming progressively stouter as they aged.

What factors could have selected for this unusual evolutionary quirk not once but twice?  The sediments containing the two fish species—though separated by space and time—share some provocative mineralogical clues: gypsum and calcium carbonate.  Both of these minerals are calcium salts and their presence as inorganic precipitates suggests that the bodies of water these fish lived in had extraordinarily high concentrations of dissolved calcium and other minerals.

The authors of the recent paper suggest that the hypertrophied skeleton of Hsianwenia (and Aphanius) was a novel solution for ridding the body of excess calcium⁵.  By thickening their bones, these fish were able to sequester calcium before it built up to toxic levels within its tissues.  Chang et al. also speculate that the saline waters were toxic to other vertebrate species given the absence of other vertebrate fossils.  So, these strange fishes may have had no need to escape from predators and could afford to reduce muscle space and add bulky bone.  Pollen and, yes, ostracods/es provide circumstantial support for generally arid and saline conditions in and around the lake while the fish were thriving.

Hsianwenia’s solution to it’s hard-water environment worked pretty well for 200,000 years or so, allowing it to thrive in waters where no other fish could.  Of course, Mother Nature’s a vindictive bitch, and all evolutionary solutions are by definition, temporary.  A thick evaporite deposit capping the fish-bearing layers speaks to our tale’s tragic end: the aridification of the Qaidam basin continued, the lake dried up, the freaky thick-boned fish died, the end.

So there you have it: tectonics, climate, aqueous geochemistry, evolution, morphological novelty and million-year-old fossil fish bones scattered across the high desert.  A fish story worth telling.

And you thought fish were boring.

REFERENCES

Chang, M. et al. 2008.  “Extraordinarily thick-boned fish linked to the aridification of the Qaidam Basin (northern Tibetan Plateau).” PNAS 105: 13246-13251.

Porter, S. M. 2007.  “Seawater Chemistry and Early Carbonate Biomineralization.” Science 316: 1302.

Qi, D. et al. 2006. “Mitochondrial cytochrome-b sequence variation and phylogenetics of the highly specialized schizothoracine fishes (Teleosti: Cyprinidae) in the Qianghai-Tibet Plateau.” Biochemical Genetics 440: 270-285.

¹ As we’ll soon see, this is a hilarious pun.
² There is one, sort of.  Be patient.
³ I suppose I’m mixing hymenopteran metaphors here.
⁴ Credit where it’s due: a German science blogger has already written about Hsianwenia here (in German).
⁵ One hypothesis to explain the “explosive” evolution of organisms with hard parts in the Cambrian holds that changes in seawater chemistry (perhaps linked to tectonic activity) drove organisms to begin precipitating minerals to prevent toxic buildup inside their cells.  Subsequently these structures were exapted into shells and carapaces and bones and teeth ultimately triggering an adaptive arms race.  While this hypothesis is speculative and controversial recent research does support the importance of seawater chemistry in setting the patterns of biomineralization among various lineages (Porter 2007).

Enigmatic Trassic Hellasaur Thursday — The mostest unkindestest cut

Venom–toxic fluid injected to subdue prey or deter potential predators–is widespread in the animal kingdom, from jellyfish to scorpions to platypodes. A case could even be made that stinging nettle is an example of a venomous plant, since it injects its toxin into victims. However, most toxic plants, as well as toxic animals and fungi that rely on passive delivery of toxins (e.g. newts) are considered poisonous but not venomous.

Snakes are one of the most familiar groups of venomous animal although a majority of snakes lack venom. Most people are also aware of the venomous beaded lizards (or, “gila monsters”) in the genus Heloderma. Far less well known is that varanid monitor lizards and bearded dragon, Pogona, popular in the pet trade, also possess a mild venom. We’re talking real venom here, not the bacterial brew that produces the much discussed septic bite of some varanid lizards. In fact, the discovery that venom occurs in reptiles aside from snakes and Heloderma was made only a few years ago and has forced us to rethink the evolutionary origins of venom among squamates (Fry et al. 2006).

So, what does any of this have to do with enigmatic Triassic hellasaurs?

Enigmatic Triassic Hellasaur Thursday…who’s counting anway? — The Duck-billed Ichthyopus

When George Shaw received the first platypus skin to make it to England in 1789, he took a pair of scissors to it to look for stitches, or so the story goes. “It is impossible not to entertain some doubts as to the genuine nature of the animal,” wrote Shaw. Surgeon, and racist, Henry Knox argued that the Asian itinerary by which the specimen had traveled was, “sufficient to rouse the suspicions of the scientific naturalist, aware of the monstrous impostures which the artful Chinese had so frequently practiced on European adventurers.” Of course, the reality of this chimerical creature has long since been recognized, and, as of this week, we have the unique genome to prove it.

More recently the “Archaeoraptor” scandal raised echoes of Knox’s Sinophobia, and this weeks’ hellasaur is certainly enough to raise eyebrows. Hupehsuchus nanchangensis, has that “designed by committee” look, with the limbs of a basal ichthyosaur, the dorsal armor of a placodont and the bill of a…well, duck. But the fossils indeed check-out: this is no “monstrous imposture”, just one freaky-ass (or if you rather, enigmatic-ass) hellasaur.

Hupehsuchus nanchangensis by Zach Miller

And the more you look, the weirder it gets…more tomorrow!

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

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.

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….

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 Flycatcher - Tyrannus 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.

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 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

Woah.

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.

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)

Smells like Shrew Spirit

Star-nosed Mole (Condylura cristata) “sniffing” underwater

from Catania 2006

The kind of thing to drive any formerly self-respecting paleontologist nuts: underwater olfaction in mammals. Smell is an important sense for mammals, no surprise to anyone who has stepped into a Sephora outlet recently. Though we are generally far more conscious of sight and sound, we’re still led around by the nose far more than we would guess…especially when it comes to eating and mating.

And other mammals, especially those who have stuck to more respectable mammalian lifestyles (i.e. grubbing around for worms and bugs at night), put humans to shame in the olfaction department. Still, the announcement that some specialized “insectivorans” (or soricomorphs if you’re T.C. like that) are able to smell underwater came as a surprise - to me at least.

As seen in the photo above, this amazing feat is accomplished by expiring a small bubble of air then re-inspiring it. This allows these air-breathing mammals to safely search for odors underwater as they search for prey. Notably, many other aquatic mammals rely exclusively on other senses especially hearing and touch; whales have apparently little or no sense of smell judging from their brains.

A detailed analysis of the tactile and olfactory abilities of the American Water Shrew (Sorex palustris) in PNAS, expands upon the initial report of underwater smelling by shrews and moles. Like the previous Nature paper there are awesome photos and slow-mo videos documenting this amazing behavior, highly recommended.

The elaborate experiments by Catania and co. showed that S. palustris uses a combination of tactile (via whiskers) and olfactory clues to evaluate potential prey items. One video shows a shrew puzzled by an artificial cricket which apparently “feels” right but “smells” wrong. They also used experiments to rule out echolocation or electroreception - strategies employed by other mammals that forage underwater.

As for the paleontological lament: it took a serendipitous flash of insight plus the availability of high speed cameras and infrared lighting to bring this interesting behavior to light. One has to wonder how many strange behaviors among fossil taxa, peculiar and mundane, have yet to and may never be guessed at.

Interestingly, aquatic olfaction has been suggested in plesiosaurs based upon skeletal evidence, but I suspect we’ll be waiting awhile for the slow-mo vid.

Er…How about Mink-tailed Muntjac with Marfan’s?

Okay, I’m going on record in defense of our favorite AP word-smith, science writer Seth Borenstein.

In a nice blogpost on Indohyus, [the sexiest new raoellid on the block] Brian takes Borenstein to task for some awkward animalian analogizing:

writer Seth Borenstein can’t seem to figure out just what Indohyus is. His confusion is apparent from the first line of the article;

It sounds like a stretch, but a new study suggests that the missing evolutionary link between whales and land animals is an odd raccoon-sized animal that looks like a long-tailed deer without antlers. Or an overgrown long-legged rat.

Borenstein scrabbles¹ to lump Indohyus in with some modern animals in a feeble attempt to get people to understand the fossil find, but I can’t help but wonder if such a comparison does more harm than good.

As I noted in a comment on Brian’s blog however, Borenstein cribbed his ungainly comparison from the lead author on the Indohyus paper Hans Thewissen, at least in part:

“The earliest whales didn’t look like whales at all,” Thewissen said. “It looked like a cross between a pig and a dog.” They lost their legs and ability to walk on land about 40 million years ago, he said.

And the Indohyus? “A tiny little deer maybe the size of a raccoon and no antlers,” Thewissen said. He said it most resembles the current African mousedeer, which has a rat-like nose and “when danger approaches, it jumps in the water and hides.”

Sure, maybe it’s a misleading oversimplification to cast the cetacean ancestry debate as a war between the “racoon-deer campus” and the “hippo campus².” Sure, trying to shoehorn every strange animal into this or that familiar category or combo of categories is a dubious (though longstanding and universal) habit. But, as long as we’re not ‘calling whale evolution into question’ hey, I’m pretty happy.

Sometimes, words just fail. Good thing we have Carl Buell. Check out Buell’s awesome reconstruction on Laelaps.

¹ - Note the awesome verbing of the word “scrabble”.
² - sorry.