Jethro and Joel were a Choristodere (not a dinosaur)

22 December 2006

Unpublished preliminary sketch for Jethro and Joel Were a Troll by Disney animator and prolific artist/author Bill Peet (Buy the book).



Two-headed choristoderan fossil from Lower Cretaceous rocks in China, from Buffetaut et al. (2006).

The recent publication of the astonishing fossil shown above would seem the perfect end-note to a year packed with crazy, beautiful and marvellous fossils. Axial bifurcation (i.e. two-headedism) in reptiles, especially snakes, is hardly unknown1, but this very young (possibly embryonic) aquatic reptile marks the first recognition of axial bifurcation in the reptile fossil record.

I came across the story over at yet another paleoid blog, Kyle Lindsey’s Παλαιός βίος (that would be “Palaeos Bios” for those of you who went to a school with a draconian anti-Greek policy). Reading the BBC story that Kyle posted first agitated, then exasperated and finally enraged me. Let’s take a moment to tear into the horrendously misleading story, shall we?

Palaeontologists have unveiled the fossilised skeleton of a two-headed dinosaur that roamed the earth about 100 million years ago (MYA).

Nope. Not a dinosaur, Hyphalosaurus (the likely identity of the fossil), was a long-necked aquatic reptile superficially similar to a miniature pleisosaur or a nothosaur but was most closely related to the champsosaurs. The (effing)-champsosaurs were a group of generally large crocodile-esque predatory reptiles that showed up in the Mesozoic and persisted well into the Cenozoic, somehow escaping the K-T(or K-P if you’d rather) mass extinction.

This is not simply a semantic distinction. “Dinosaurs” were a distinct group (or possibly two or more distinct groups) that shared a set of features not found in other Mesozoic reptiles. Any writer covering paleontology should take the time to figure this out. Would editors tolerate a journalist who lazily referred to all legislative bodies as “The U.S. Senate” or called Cambodians “Chinese”?

While the exact age of the formation this fossil came from is in debate, it’s probably more like 120 million years old, but who’s counting? Unfortunately the BBC article gets worse:

But before it is added to the pantheon of prehistoric beasts occupied by luminaries such as Tyrannosaurus Rex and Triceratops, scientists point out the dinosaur was only 70mm tall and died at a very young age.

What does this have to do with anything? Only large taxa earn a place in “the pantheon”? I won’t even waste time on the misformatting of the scientific binomials, but it should be “Tyrannosaurus rex and Triceratops”.

Publishing their findings in the Royal Society journal, the Chinese palaeontologists discovered the specimen in the famed dinosaur-stamping grounds of Yixian Formation in the north-east of the country, with its mixture of volcanic and sedimentary rocks an ideal place for fossils to be preserved.

Okay maybe a run-on sentence, but I’m probably not one to throw stones here. There certainly are fantastic dinosaur fossils from the Yixian although in this context describing the Yixian formation as “dinosaur-stamping grounds” probably perpetuates the misidentification.

They explain that the fossilised remains of the infant, possibly an aquatic diapsid such as Sinohydrosaurus lingyuanensis or Hyphalosaurus lingyuanensis, is the first time that axial bifurcation – where reptiles develop two heads and necks – has been observed in dinosaurs.

Still not a dinosaur. And given that Sinohydrosaurus is regarded as junior synonym for Hyphalosaurus2, it’s either Hyphalosaurus or something else. Worth noting, is that Hyphalosaurus is a relatively abundant vertebrate fossil, widely (and illegally) exported from China for purchase by private collectors. The fossils range in size from a few centimeters to over a meter, apparently representing the organism at all stages of development. Many of the fossils, like Jethro and Joel, appear to be juveniles or even embryos.

It’s rare to get such a complete growth series in fossil vertebrates, making Hyphalosaurus a wonderful candidate a detailed analysis of growth and development patterns (someone may well be working on this already). It’s even plausible that other malformed specimens might be out there. Moving along…

The condition occurs relatively commonly in turtles and snakes as a result of the species’ regenerative qualities when suffering an embryonic lesion.

Most explanations of axial bifurcation in reptiles cite an incomplete duplication of the embryo, similar to mechanism that yields conjoined twins in humans. This is the first I’ve read of lesions, but it’s an interesting idea. I’d like to know more.

Many extraordinary fossils from the Yixian Formation have later been exposed as fakes, but the scientists from the Shenzen Palaeontological museum insist the fossilised remains of the infant, which would have grown to 1m long, are genuine.

While a heavy dose of skepticism is appropriate for such a bizarre fossil, this closing paragraph is not just misleading, it provides (possibly unknowingly) some prime creationist fodder. As far as I know only one fossil from Liaoning was exposed as a chimerical forgery, the infamous Archaeoraptor. That’s hardly “many” and calling it a “fake” obscures the fact that the theropod-half of Archaeoraptor a.k.a. Microraptor is both real and exceptionally important to science (as is the bird-half Yanornis).

Perpetuating the misconception that paleontologists are frequently duped by abundant fossil forgeries is inexcusable.

While Archaeoraptor was cobbled together from pieces of different animals, Jethro and Joel appear to be in one piece of matrix and the close association of the necks and heads strongly suggest it to be genuine.

Okay, so that was an exercise in futility. Is it too much to ask that journalists covering science to at least a little bit of background research? A simple scanning of the Wikipedia Hyphalosaurus entry would have made it apparent that the animal wasn’t a dinosaur. And turing one fossil forgery into “many fakes” is both foolish and dangerous.

Well, at least I put off Christmas shopping for a few more hours. Maybe I’ll just order one of these for everyone on my list:

Postscript: HMNH has a brilliant P. T. Barnum-style post on Jethro and Joel. The Neurophilosopher uses J&J as the jumping off point for a fascinating account of lab-made double-headers, go read it now.

 

1– While I’m generally very wary of mixing science and mythology (it seems generally to wind up doing a disservice to both), it seems at least plausibile that bicephalic snakes or lizards might have been the inspiration for various multi-headed reptiles of myth, like Lotan, Orochi, the Lernaean Hydra and the Dragon of Revelation. Then again, maybe the seven-headed Dragon described in Revelation 12:3 is the E.U., or Russia or China or whatever (and maybe Mongolia is the dreaded Turquoise Pupa of Evil).

2– The double-naming of Hyphalosaurus is an interesting story. Two different groups of Chinese researchers simultaneously described (apparently unknowingly) the part and counter-part of the same fossil thus generating two competing names. The charmingly straight-forward Sinohydrosaurus (literally “Chinese water lizard”) was published slightly later and thus yields to the slightly more prosaic Hyphalosaurus (“submerged lizard”). A brief technical account from the of the mix-up from the Journal of Vertebrate Paleontology is available as a pdf, Smith and Harris (2001) .

One Response to “Jethro and Joel were a Choristodere (not a dinosaur)”


  1. […] Update 12/23: A nice article on this and other Chinese choristoderes is up at microecos. File under Recent Discoveries, Cretaceous. Posted by Matt Celeskey round about 12:14 am. […]


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