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Preliminary discussion of Omnivoropteryx & Scansoriopteryx
Mickey Mortimer's interesting, rather thorough
exegesis of the two specimens addresses the question
of osteological comparisons to similar taxa. However,
Scansoriopteryx is presumed to be a 2-3 week old baby,
and my query for Mickey: does this alter the
hypothetical analysis? I have, e.g., compared a
skeleton of a week old human with a full-grown adult
--both are H. sapiens, but the differences (especially
in the skull) are startling. If Scansoriopteryx is an
infant, then how can comparisons be made to other taxa
for which growth series are not known?
I have before the J.M. Starck/R.E. Ricklefs 1998
compendium, Avian growth & development: evolution
within the altricial-precocial spectrum (Oxford
University Press), a volume Stephen Czerkas is,
judging by his interpolations, not familiar with. It
is a volume with should be in anyone's library who is
interested in dinosaur growth patterns.
Chapter 11 of the Starck/Ricklefs volume is a
useful analysis of what is known about extant dinosaur
growth rates. Added to my comments the other day about
Stephen Czerkas's factually unsupportable claims re:
Scansoriopteryx, origins of flying dinosaurs, etc.,
one can add some preliminary addenda to Mickey
Mortimer's osteological observations.
Allow me to recapitulate some of their
extrapolations. A large, feathered dinosaur will have,
in its first few weeks of life,a slower growth rate
than a smaller taxon, but tissue functionality will be
more mature. An infant taxon as small as
Scansoriopteryx will, thus, have a tiny digestive
system, and inner organs would be tiny relative to a
small skeleton. And the small skeleton is the key, as
Mickey Mortimer, as mentioned previously, is analyzing
an infant relative to other taxa; with growth,
increased self-maintenance, thermoregulation, activity
in the nest, epithelial tissue energy consumption, the
size of the animal changes. In other words, all of the
bodily systems of the infant Scansoriopteryx would be
constrained, basal metabolic rates and skeletal growth
slower. Mickey Mortimer can describe what the infant
specimen reveals, but, I must stress, a "diagnosis" of
an infant is on nebulous foundations, and while
superficial similarities are noted by him to more
adult specimens, I would prefer further, older
specimens of the taxon before formulating a
phylogenetic analysis. I appreciate Mickey's thorough
comments, to be sure. We do not know which of these
feathered dinosaurs were precocial (able to run about
after hatching) or altricial (nest bound). The latter
may have had relatively faster growth rates, ensuring
parenting success (the ability to renest in the same
season) if the cellular growth of the infants was
compable to adult stages.
Larger, altricial feathered dinosaurs may have
been limited on the number of times of breeding during
a year, growth rates slowing during maturation. If the
nestlings have little sibling competition, energy
requirements would, similarly, be reduced. And, if
these dinosaurs had, at times, poor nutrient intake,
energy requirements, then infant mortality in the
nests could have occurred. With precocial dinosaurs
(flightless or not), the constraints would not exist,
simply because they would be able to find some food.
Growth rates would be variable, tissue morphogenesis
have a discernable effect on skeletal proportions.
One morphological feature I looked for: indication
of skeletal morphology relative to its inner organs,
especially the digestive tract, the largest organ
system in the dinosaur at such an age, and digestive
tract size would determine the metabolizable energy
derived from nutrients of the taxon. I am speaking of
biosynthesis of dinosaurs.
I shall return to this discussion later today.
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