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Sunday, December 18, 2011

Mokele-Mbembe is alive... or not...

Today sees the publication of what is surely the century's most significant zoological discovery. After decades of searching, Africa's mystery Congolese swamp monster, the Mokele-Mbembe, has been discovered - it is a living sauropod dinosaur, and it radically alters our understanding of archosaur phylogeny, sauropod biology and diversity, and indeed the evolutionary process as a whole.
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As is fitting for the discovery of a brand new, extant, hitherto cryptic megabeast represented by complete carcasses, the Mokele-Mbembe - officially christened Chipekwe lackadaisicalus Brill et al., 2011 - is described in a two-page, 1000-word paper.
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Previous expeditions to search for the Mokele-Mbembe have been unsuccessful, at most involving fleeting glimpses and indeterminate photos of the beast. A 2010 research effort based at Mazylacrony, Republic of the Congo, led by E. J. Brill of the University of Leiden, initially resulted in still-photo images obtained by camera-traps. Two of the better of these photos (one showing an adult in its aquatic habitat [above] and one showing a juvenile) are featured here (more camera-trap images are included below). Camera-trap data shows that Mokele-Mbembes are herbivores, and that (despite their size: upwards of 15 m) the females dig burrows in river-banks where they give birth to a single, slow-growing baby. All of the previously established ecological and behavioural traits (Mackal 1987, Heuvelmans 1995) of the Mokele-Mbembe are true. Oh, and Bakker was right about sauropods being viviparous. Huh.
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Further exploration at Mazylacrony a week later resulted in the fortuitous discovery of not one, but two Mokele-Mbembe carcasses. I was lucky enough to participate in the expedition set up to retrieve information from the carcasses, and was joined by an elite international team of scientists and explorers including Rachael Allen of Saint Xavier University, Max Blake of the University of Bristol, Markus Bühler of the University of Tübingen, Andrea Cau of the Museo Geologico e Paleontologico "Giovanni Capellini", Roger Close of Monash University, Marcus Good, Phil Hore of Prehistoric Times, David Hubble of The Open University, Ted R. Kahn of the Neotropical Conservation Foundation, Bevin Kelley of Brown University, Hanneke Meijer and Jorge Moreno-Bernal of The Smithsonian Institution, Daniel Najib of St. John's University, Joy Reidenberg of Mount Sinai School of Medicine, Blake Smith of Kennesaw State University, and a shitload of others; jesus, the number of people involved became ridiculous after a while (for a complete list see the authorship on the paper).... oh, and Sean Young, the actress who played Rachel in Blade Runner - yeah, she came along as well.

The two Mokele-Mbembe carcasses - representing an adult and juvenile - died in close association, perhaps due to lightning strike, perhaps due to ingestion of toxic algae, or perhaps due to the hail of gunfire put in their general direction by our research team. Their skulls were unfortunately lost during this "collection procedure". Despite the similarity of the animals to the stocky, fat-legged, rubber-necked brontosaurs depicted in Peter Jackson's King Kong, it was immediately obvious that they represented a new species of extant sauropod. [Images below show neck structure in juvenile specimen; read on].
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We were inspired in our quest for the Mokele-Mbembe by Jonathan Kingdon's book Island Africa (Kingdon 1990): after all, doesn't he say that little chunks of habitat in tropical Africa have remained unchanged since the Mesozoic?*. In discussing the cichlids of Lake Malawi, Kingdon noted that English-speaking scientists rightly acknowledged the names used for these fish by local people. We wanted to do the same for the Mokele-Mbembe, so officially named it the Mokele-Mbembe. We used one of many local names for the creature - Chipekwe - in the binomial.

* He categorically and certainly did not, but let's not let the details get in the way.

It was always predicted (Naish 2000, 2002) that - when the inevitable discovery of modern-day sauropods occurred - the cutting up of a dead one would pose great problems. The sheer size of such a beast renders dissection difficult, especially when (as is the case here) the animals had been decomposing in a humid, tropical environment. Remember that many aspects of whale and elephant anatomy remain controversial or scarcely known due to the practical difficulties associated with their dissection, and these animals are known from hundreds of specimens and have been the subject of scientific attention for centuries. In a desperate but text-book example of 'smash and grab' dissection, salient details were recorded or hastily ripped from the carcasses prior to the confiscation of our team's equipment and belongings by Congolese biologist and competing Mokele-Mbembe investigator Dr Aarcellin Magnagna and Danish author and scientist Dr Lars Thomas. We are pursuing legal action against these individuals.
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Due to the healthy bushmeat trade flourishing across tropical Africa we were, however, able to smuggle out part of the smaller individual (the thorax and neck) and later dissect them in the laboratory. Various of our dissection photos and resulting anatomical diagrams are shown here (for more, see the online supplementary info, currently of unknown whereabouts). We started by CT-scanning the carcass: one of the resultant images is shown above. As you can see from the dissection pics shown above, the dorsal surface of the ribcage exhibits the strongly corrugated morphology seen elsewhere in birds. An enlarged resonating chamber at the base of the neck indicates an ability to generate loud, low-frequency (possibly infrasonic) noises of the sort recorded by Herman Regusters during his 1981 expedition to Lake Tele. We were able to answer most of the questions people have posed about the soft-tissue anatomy of sauropod necks, but don't plan to publish them for a few decades, if at all.
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As you can see from the adjacent image, the cervical vertebrae ofChipekwe are bizarre in being amphicoelous, rather than opisthocoelous as is typical for sauropod necks. Lacking the ball-and-socket joints of other sauropod vertebrae, it might be predicted that Mokele-Mbembe has a less flexible neck than Mesozoic sauropods, but this is not supported by compelling eyewitness accounts of Mokele-Mbembe behaviour. Sean Young is helpfully holding the vertebrae for the photo. Since she stars in both Dune and Blade Runner - where she plays the seductive replicant Rachel - her involvement in the 2010 expedition seemed only natural. She was brilliant in the field and proved a dab hand at fixing jeep axles and outboard motors. Did I mention that she played Rachel in Blade Runner?

Phylotardation in extant sauropods

The great surprise about the anatomy of these animals is that they are highly anachronistic- or phylotarded - compared to Mesozoic sauropods. In fact, Mokele-Mbembe more resembles artistic restorations of sauropods from the decades preceding the 1960s. The skin of Chipekwe lackadaisicalus is smooth and devoid of both the vertebral spines present in fossil diplodocoids and the dermal ossicles and spines present in titanosaurs. The articulated limb skeletons of Mesozoic sauropods, combined with many thousands of well-preserved trackways, show that these animals had columnar hands where the back of the hand was concave. Claws were absent but for a single thumb claw, and even this was absent in many titanosaurs. Meanwhile, the oval feet had three (occasionally two, occasionally four) large, curved claws.
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In contrast, Chipekwe lackadaisicalus has huge, rounded, spreading, semi-plantigrade hands and feet, with four large claws on both [as is obvious in the image above of the larger Mazylacrony carcass]. And while osteological evidence shows that Mesozoic sauropods typically held their tails in a horizontal pose (or even with an elevated tail-base in some species), the tail of the Mokele-Mbembe slants down towards the ground in true, phylotarded fashion. The animal looks fat, rubbery, bulky, and altogether way less cool than those kickass sauropods shown kicking the shit out of unfortunate theropods, or rearing up bipedally to nibble at pine needles, or box with one another, or whatever. [Below: 'modern' sauropod rendition on the left from dontmesswithdinosaurs.com; more realistic phylotarded version on right from Roy Mackal's classic, perceptive work A Living Dinosaur? In Search of Mokele-Mbembe].
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Chipekwe preserves no evidence of feathers nor of a semi-lunate carpal bone in the wrist and therefore verifies previous observations based on the skin of the Cretaceous ceratopsian Psittacosaurus and ornithopod Edmontosaurus that such features were absent in dinosaurs (Lingham-Soliar 2008). It therefore makes a mockery of the Hollywood-inspired idea that dinosaurs had feathers, or evolved into birds. The 'birds are dinosaurs' movement is evidently kept alive by museum staff who need to remain employed, especially during these desperate economic times.
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Several possibilities might account for the anatomic phylotardation present in this animal. The first - that our modern conception of Mesozoic sauropod anatomy is wrong, and that Zdeněk Burian was right on the money in 1955 - is unlikely to be correct, since it's generally admitted that, by now, we know what we're doing. I mean, come on, Greg Paul is far cleverer than Zdeněk Burian or Charles Knight. A second possibility is that the lineage including Chipekwe lackadaisicalus was subject to wholesale taxic atavism of the sort seen elsewhere in gharials (Gatesy et al. 2003). In other words, the animal's phenotype and, oh yeah, genotype have gone all atavistic on us: just what this means, if anything, for its essence/soul is uncertain, but we remain confident that, at its core, the animal is Mesozoicy. A third possibility is that the ACF (= aesthetic coolness factor) of the characters concerned is low, and hence subject to deletion during phylogeny. We didn't explore that last option since it would have meant adding an extra paragraph to our paper.

Finding an extant member of a fossil group can really screw with your data

The enormous amount of skeletal, soft tissue and genomic data available from the Mazylacrony carcasses allows the construction of a new, massive character database; the information we now have available for the analysis of sauropod phylogenetics has just increased one-hundred-fold. Brill et al. (2011) approached this situation in an entirely novel way.
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As knowledge about organisms (modern and extinct) has increased, and as evolving software has allowed the rapid processing of ever-larger data sets, lists of characters and tabulations of character codings have grown and grown and grown. Many phylogeneticists now work with character lists that exceed or approach 1000 in number, and they've generated endless, boring pages of character states. This stuff is really, really boring, and - let me tell you - a real pain in the ass should you need to re-format it when re-submitting your rejected manuscript for another journal. While the phylogenetic analyses generated by these studies have produced well-resolved trees with good statistical support across nodes, and while independent teams of authors have increasingly converged on trees with similar topologies, it's been clear for, oh, a while now that things need to change: it's just all too complicated for anyone to keep track of [the adjacent image - from Sereno (1999) - shows a typical, run-of-the-mill, modern dinosaur cladogram. Do you realise how much work is involved in producing something like this?]. I mean, come on, there's no way any person could carry around all that information in their head and those tables of characters are just so boring.

Brill et al. (2011) employ a new phylogenetic method termed mihaldification. Inspired by the pioneering work of the great palaeozoologist Dean-Pierre J'Amour, this technique incorporates hundreds of taxa, but requires that just two or three characters - or perhaps even just one - are tabulated for each group. The new mihaldified data generated for Archosauria by Brill et al. (2011) indicates rampant phylotardation across Archosauria and reveals a few surprises, including non-monophyly of Dinosauria, non-monophyly of Saurischia, non-monophyly of Ornithischia, non-monophyly of Theropoda, non-monophyly of Coelurosauria but - oh - monophyly of Prosauropoda [see newly generated mihaldigram shown below]. Sauropoda in the mihaldified data set falls obviously and neatly into a broad-toothed, camarasaurish clade and a narrow-toothed, diplodocish clade (though with cetiosaurs, turiasaurs, mamenchisaurs, most titanosaurs and most Triassic and Lower Jurassic taxa being of unresolved position). The approximately 6000 phylogenetic studies published on sauropods in recent years, virtually all of which find sauropod phylogeny to be far more complex than thought prior to the 1980s, were dispensed with following our 'safe citation deletion' protocol. We admit that we also opted to employ 'safe citation deletion' when reviewing the work of others; an action required in order that we establish the novelty of our assertions.
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Anyone who's followed Mokele-Mbembe research will be familiar with the substantial creationist literature on this animal. Brave, plucky missionaries have done a sterling job in accurately collecting natural history data on this animal, and brilliant creation scientists have used the existence of the Mokele-Mbembe and other phylotards to poke holes in the increasingly weakly supported, flimsy, tissue-like tattered shred of a once-dreamt notion that is Mr Darwin's theory of Darwinian evolution.

So - does the existence of the Mokele-Mbembe verify one of the core creationist beliefs? Namely, that the very existence of such creatures nullifies the hundreds of independent, repeatable, testable, technically published, peer-reviewed observations and hypotheses that provide irrefutable support for evolutionary theory? Yes, it does. The existence of a kind of animal belonging to a group otherwise thought long-extinct demonstrates beyond question that evolution does not and cannot happen. The existence of sharks, crocodilians, lizards, frogs, salamanders, bats, ostriches, hoatzins, shellfish, coelacanths, crayfish, bush-babies, owls, pandas, the Okapi, moles, clouded leopards, ducks, monitor lizards, invertebrates, the Spangled drongo, the Brown antechinus, coelacanths, coelacanths, coelacanths, sharks, crocodilians, sharks, crocodilians, coelacanths, sharks, crocodilians and humans and coelacanths also provides damning evidence that animals known from the fossil record are more or less similar to the animals of today, and hence that living things do not change - or evolve - over generations, though obviously they do, quite a lot, if not loads, but not enough for us to worry about. Indeed this one single discovery has already sent ripples of shock and awe through the scientific community. "I guess we'll have to go back to the drawing board - looks like the creationists were right after all!", said noted phylogeneticist Dr Filo Genetissust.
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But - I hear you cry - how is the over-arching philosophy of scientific creationism consistent with our proposal of phylotardation? After all, scientific creationism (or intelligent design) proposes that living things sprung into existence by magic, not via some sort of process whereby heritable features, affected by external selection pressures, are passed down through the generations. The answer lies inretardosity, a previously overlooked phenomenon that works well when applied to mihaldified data sets. Using the repeatable procedure known as reliable inference, we found that phylotarded taxa could both spring into existence by magic and be linked to others by way of a mihaldified analysis involving single characters. The resultant clades evidently correspond to thebaramins defined with clarity in archaic sources.

So it's thanks to mihaldification, retardosity and creationism that we have finally ushered in a new age of enlightenment. As soon as our paper on the Mokele-Mbembe came out, I went and held a big bonfire of all my pro-evilution books. Of course, some of our colleagues say that the existence of Chipekwe lackadaisicalus is perfectly consistent with evolution and existing phylogenetic schemes published for Sauropoda, but, well, yeah, blah blah blah.

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