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Re: Sauropods and Endothermy



Lawrence Kashdan (Kashman7@aol.com) wrote:

<I'm sure you read about "Willow?" The dinosaur with a heart?>

...

<With Willow Dale Russell has discovered what is probably the only known
fossilized heart of a dinosaur.>

  While Fisher, Russell, and the others theorized that this ironstone
concretion was unique shaped and structure to be a heart, others have
found this to be a sedimentary deposit, and actually infer the nature of
such a deposit in other forms (Rowe et al., "Such concretions are commonly
found in Upper Cretaceous fluvial sediments of the North American western
interior, often in association with dinosaur bones.").

http://www.sciencemag.org/cgi/content/full/291/5505/783a

  which is freely available online, as are are thing from _Science_ after
one year's time (except Reports), and especially _all_ Technical Comments.

  Specifically, Rowe et al. find most damaging: "Although CT imagery of
the concretion has revealed internal cavities reminiscent of the
ventricular chambers of a four-chambered heart, the object exhibits none
of the other anatomical structures of an actual heart. Its supposed
ventricular portion engulfs the eleventh rib and lies partly outside of
the thoracic cavity. The right cavity interpreted by Fisher et al. as a
ventricle is almost completely closed; only its "interventricular" wall is
penetrated, by complex fractures containing lower density materials. Their
shape and position are entirely unlike the single, oval foramen of
Panizzae of extant crocodilians, which affords a pulmonary shunt during
prolonged periods underwater. There are no atria, coronary arteries,
cardiac veins, pulmonary vessels, or vena cavae." They go on to show how
the "aorta" is blind, rather than continuous, and merges into its own
wall, along with the lumen.

  This is clearly not a heart. Now, that specimen, Willo, is the best
preserved "thescelosaur" known, and has a complete skull, and this is
perhaps more newsworthy if the popular press knew what it was like to not
have such a complete specimen at their disposal.

  Fisher et al. also reply:

  "Rowe et al. suggest that the object we have interpreted as a heart is
instead an ironstone concretion. Irregular, poorly delimited ironstone
concretions containing abundant plant debris can indeed be found at a
horizon several meters above the one at which the thescelosaur skeleton
was found; no such concretions occur in strata adjacent to the skeleton,
however. By contrast, the concretion studied by Fisher et al. is
intimately associated with the skeleton, in a manner unlike that of any
other concretion in the vicinity of the site or reported from Upper
Cretaceous strata elsewhere in the western interior of North America. A
rib in the front of the chest, on the undersurface of the skeleton as
buried, contacts the concretion and is partly embedded in it."

  But they cannot get by the formation of the deposit around a rib. Their
point about supposedly hollow structures (or very light material infilled
into the ironstone) without any apparent plant material is telling in some
manner, and Rowe et al. did not explain the process by which such a
structure could have formed. However, it is my opinion that Fisher et al.
jumped the gun when they called this a heart, rather than remarking on the
morphology and deposition of the structure. They came at this running with
a heart, and may just be juggling a common fluviatile structure.

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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