[TN-Bird] Off topic Harvard research indicates birds may be juvenile dinosaurs
- From: Viclcsw@xxxxxxx
- To: tn-bird@xxxxxxxxxxxxx
- Date: Thu, 31 May 2012 15:42:54 -0400 (EDT)
Harvard research published in the journal Nature indicates birds may be
"juvenile dinosaurs". LA Times summarizes here:
_http://www.latimes.com/news/science/sciencenow/la-sci-sn-birds-dinosaurs-20
120529,0,7306734.story?track=rss_
(http://www.latimes.com/news/science/sciencenow/la-sci-sn-birds-dinosaurs-20120529,0,7306734.story?track=rss)
Birds may be dinosaurs that never grew up
A modern chicken and a baby dinosaur are surprisingly closely related.
(Illustration by Frank Ippolito, American Museum of Natural History / May 29,
2012)
* ALSO
*
(http://www.latimes.com/news/nationworld/nation/la-sci-dinosaur22-2009oct22,0,1635147.story)
_Fossils of North America's smallest dinosaur
identified_
(http://www.latimes.com/news/nationworld/nation/la-sci-dinosaur22-2009oct22,0,1635147.story)
*
(http://www.latimes.com/news/science/la-sci-dinosaur-methane-20120508,0,5712036.story)
_Dinosaurs' digestive gases linked to global warming_
(http://www.latimes.com/news/science/la-sci-dinosaur-methane-20120508,0,57120
36.story)
By Thomas H. Maugh II
May 29, 2012, 10:46 a.m.
Modern day birds may simply be dinosaurs that never grew up, researchers
say. A comparison of fossilized skulls of juvenile dinosaurs with those of
birds shows remarkable similarities, adding further evidence to the growing
consensus that birds are evolutionary descendants of dinosaurs. A team from
Harvard University _reported _ (http://www.nature.com/nature) online in
the journal Nature that for some as-yet-unknown reason, some dinosaur infants
began to mature much more rapidly than normal. That rapid maturation
altered the expression of_genes_
(http://www.latimes.com/topic/health/human-body/genes-chromosomes-HHA000024.topic)
, changing the physical characteristics
of the animals and keeping them much smaller in size. Those changes allowed
the development of a relatively bigger brain and the development of
flight.
A variety of evidence suggests an evolutionary link between the two
species. At least 22 bones are found only in birds and dinosaurs, and in no
other
animals. Researchers have found fossils of feathered dinosaurs, fossils of
dinosaurs with other bird-like features, and fossils of primitive birds
with dinosaur-like features.
Evolutionary biologist Arkhat Abzhanov of Harvard University noted an
apparent resemblance between the skulls of juvenile dinosaurs and adult birds
and decided to do a more comprehensive study. With graduate student
Bhart-Anjan Bhullar, he used CT scanners to examine dozens of skulls,
including
modern birds, theropods -- the dinosaurs most closely related to birds -- and
earlier dinosaur species. By identifying various landmarks on the skulls,
they were able to track how the skull shapes had changed over the years.
"We examined skulls form the entire lineage that gave rise to modern
birds," Abzhanov said. "We looked back approximately 250 million years, to the
Archosaurs, the group which gave rise to crocodiles and alligators as well
as modern birds. Our goal was to look at these skulls to see how they
changed, and try to understand exactly what happened during the evolution of
the
bird skull."
What they found was surprising. Early dinosaurs underwent vast
morphological changes as they aged. Among other things, their snouts grew
longer and
their heads grew flatter. The skulls of juvenile and adult birds, in
contrast, are remarkably similar. They concluded that the evolutionary changes
that produced birds were a phenomenon known as paedomorphosis. "We can see
that the adults of a species look increasingly like the juveniles of their
ancestors," Abzhanov said. In the case of birds, he added, the phenomenon is
caused by a process called progenesis, in which the descendants reach sexual
maturity earlier. Birds can take as little as 12 weeks to reach maturity,
while dinosaurs required months or years. Concluded Abzhanov: "When we look
at birds, we are actually looking at juvenile dinosaurs."
LATimesScience@xxxxxxxxx
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