Pharyngula::Dinocephalosaurus

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Friday, September 24, 2004

Dinocephalosaurus

PZ Myers • 11 Comments

Here's a new fossil from the pages of Science, Dinocephalosaurus orientalis:

The Middle Triassic marine protorosaur D. orientalis is known from a skull [(bottom inset) IVPP fossil no. V13767] and a nearly complete skeleton (IVPP V13898). The structure of its hindlimb (top inset) documents fully aquatic habits.

The proportions on this guy are definitely odd: the body was about 1 meter long, while the neck was 1.7 meters long. The authors have a nice description of how the anatomy would have contributed to its behavior.

Contraction of muscles Eoriginating from cervical ribs and bridging the intervertebral joints would have rapidly straightened the neck while the ribs would have simultaneously splayed outward. The consequent increase of the esophageal volume would have created suction such that the animal would have essentially swallowed the pressure wave created as its head lunged forward. This would have resulted in an almost perfect strike at a prey item in water.

That's a problem modern fish also face, lunging the teeth forward without also generating a pressure wave that pushes the prey away. Putting ribs in the neck and coupling them to the extensor muscles so that a lunge generates compensating suction is a cunning idea.

Li C, Rieppel O, LaBarbera MC (2004) A Triassic aquatic protorosaur with an extremely long neck. Science 305:1931.

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Comments:

#6406: — 09/24 at 08:14 AM
What a clever idea that ol' Intelligent Designer had with that one. I wonder why he threw that design away. Must have made a mistake someone else in the design. But you would think he could have gotten it right by the time he (or it, or they) designed the modern fish.

#6412: — 09/24 at 08:56 AM
Neat...something new to draw! As far as "design" goes, even in the early Triassic there was nothing totally new under the sun except for the proportions of the same old bones.

#6414: Andrew Brown — 09/24 at 09:14 AM
Fish, presumably, get round it by expelling the water throough their gills when they lunge open-mouthed? I've never thought about it, though I know that some fish, such as (yellow) perch will engulf small prey by opening wide so that the victim is sucked in.

#6419: — 09/24 at 10:24 AM
Not cunning enough of an idea, apparently. It's extinct, after all.

#6421: PZ Myers — 09/24 at 10:32 AM
OGeorge: The accompanying article does talk a bit about strategies in proportions: some related critters lengthened individual cervical vertebrae, while keeping the numbers the same. This one lengthened by adding more vertebrae (25 total) to its neck.

Andrew: Yes. There's a whole set of muscular reflexes triggered in many fish when they go to bite something, including flaring of the opercula.

gwangi: That's what they're going to say about big brains someday, too.

PZ Myers
Division of Science and Math
University of Minnesota, Morris

#6427: — 09/24 at 11:07 AM
I look forward to reading the article Paul. New (more) cervical vertebrae yes, but still cervical vertebrae. There's amazing variety on the theme, but nothing uniquely new. Our old "creator" shows an incredible lack of imagination. Why not just one long flexible bone, or telescoping bones, or an accodian bone or....

#6435: — 09/24 at 03:53 PM
The contemporary mata-mata (Chelys fimbriata, as I recall) is a modern analogue - it expands the volume of its long neck rapidly and sucks in small prey items with the indraft. I don't believe that it has any cervical ribs - it's a turtle and these don't jibe with cervical retraction - and, while I've watched them catch prey this way in captivity (a huge deep Thunggg! and the fish disappears, the turtle subsequently blowing out a stream of scales and water), it's difficult to say, just from casual observation, exactly what the beast is doing to produce this effect. It's a slow-moving ambush predator, and so being kicked backwards isn't so much of a impediment, particularly as it is generally already braced on the bottom. It's also a pretty big turtle and not so subject to being displaced without some effort.

#6436: — 09/24 at 03:55 PM
Forgot to mention what I'd originally meant to post - the subheading for the article noting this discovery at the Science website is revealing - "ancient marine reptile really sucked" or words very much to that effect.

#6440: Matt McIrvin — 09/24 at 06:57 PM
"That’s what they’re going to say about big brains someday, too."

What will they think it with?

#6441: PZ Myers — 09/24 at 07:36 PM
Itty=bitty little brains. Or circuit boards.

PZ Myers
Division of Science and Math
University of Minnesota, Morris

#6446: — 09/25 at 05:44 AM
I'd also like to point out that if you translate the genus name, it could also count for another reason they did out - lack of successful courtship behaviours.

(Does this count for that whole "how many clades can we get dirty about?")

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Friday, September 24, 2004

Dinocephalosaurus

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