تويت
http://blogs.unimelb.edu.au/musse/fi...ird_edited.JPG
Nearest relatives
Ever since moa were revealed to European scientists in 1840, the question of the bird’s closest relative has been debated. Many people assumed that it was the kiwi because the birds lived in the same area. Some researchers still believe this. However, kiwi have wings and moa did not. Others argue that moa are more closely related to emus and cassowaries.
Certainly, moa are distantly related to the other ratites and have had an independent lineage for millennia. The moa ancestor was probably on the land that became New Zealand when it separated from the supercontinent Gondwana, some 85 million years ago. Moa evolved to become unlike any other bird, so comparisons are difficult. They differ genetically from other ratites
http://www.teara.govt.nz/en/moa/page-1
Research published in 2010 has found that the moa's closest cousins are small terrestrial South American birds called the tinamous which are able to fly.[7] Previously, the kiwi, the Australian emu, and cassowary[8] were thought to be the closest ancestors
wikipedia
http://www.teara.govt.nz/en/moa/page-1
Research published in 2010 has found that the moa's closest cousins are small terrestrial South American birds called the tinamous which are able to fly.[7] Previously, the kiwi, the Australian emu, and cassowary[8] were thought to be the closest ancestors
wikipedia
فهل هناك مثلا مصطلح convergent devolution أي تطور عكسي يمكن ان يفسر هذه الظاهرة؟؟؟!!...
اذ يبدو- بزعم الدراونة -انه ثمة عدة طيور اصبح لديهـا أجنحة ضامرة من عدة أسلاف طائرة؟؟!!!
وفي ورقة علمية بعنوان Independent origins of New Zealand moas and kiwis
ورد ما يلي:
.Contrary to
expectation, the phylogenetic analysis shows that the kiwis are
more closely related to Australian and African ratites than to
the moas. Thus, New Zealand probably was colonized twice by
ancestors of ratite birds
http://www.pnas.org/content/89/18/8741.full.pdf
The most surprising result of the phylogenetic analysis is that
the two groups of New Zealand ratites have different origins,
the moas representing an earlier divergence among ratites,
whereas the kiwis more recently shared an ancestor with the
ostrich and Australian ratites.
It has been claimed that the ancestor of modern ratites was
flightless (27) and that the major ratite groups evolved due to
the break-up of Gondwanaland. However, the fact that moas
and kiwis do not constitute a monophyletic group is incompatible
with the view that all branching events between major
groups of ratites were caused by continental break-ups.
Under the assumption of a flightless ratite ancestor, the
moas, which represent an early divergence among the ratites,
and the kiwis, which represent a later divergence, must have
been isolated together when New Zealand was separated
from Australia at approximately 80 million years ago (28, 29).
A more unlikely alternative would be that a kiwi ancestor
arrived later by swimming
. On the other hand, if the ratiteancestor was flying and flightlessness evolved several times
among ratites, the kiwis can be assumed to have arrived later
than the moas on New Zealand. Such an ancestral flying kiwi
may have been related to the approximately 50- to 60-millionyear-
old flying birds with archaic palates that have been
found in North America and Europe (1, 2). The idea that birds
can lose flight capacity and change their morphology in
adaption to a ground-dwelling existence over a short time
span has support from island faunas on New Zealand (21) and
elsewhere (30, 31). Further work on the rate of evolution of
the 12S rRNA gene in birds is necessary to clarify this point.
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