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Date: Mon, 14 Sep 1998 15:26:31 PDT From: "Matthew Troutman" <m_troutman@hotmail.com> To: amaris@tin.it, forelf@internet19.fr Cc: dinosaur@usc.edu Subject: FEET OF EARLY BIRDS Message-ID: <19980914222631.2481.qmail@hotmail.com> <<<Does someone tell me what's means
that the Arctometatarsalian
condition is reversed in Archaeopteryx, Ornithurine and Enanthiornithine birds?>>> <<The arctometatarsalian condition is
'pinching' of the third metatarsal
(long bone of the foot) between the second and fourth metatarsals (Dr Holtz will explain this better than me). Your stating means that the common ancestor of *Archaeopteryx*, Ornithurae and Enanthiornithes had the arctometatarsalian condition, but that these taxa secondarily lost this feature.>> Well, in my recent trip
to the library, I gathered up an armload of books, hoping to "catch
up" on what I`ve missed in the past decade or so of dinosaur studies. I
happened to pick up a copy of Feduccia`s book "The Origen and Evolution of
Birds", and, though I don`t quite agree on his position, find that the book
is filled with some interesting facts! Perhaps to clarify some of the above
statements, here are some quotes...(preface viii) "The Mezozoic
era,....was a period of adaptive radiation.... Predominant in this radiation
were the recently discovered "opposite", or enantiornithine, birds, so
named because the three metatarsal bones fused from proximal to distal, the
opposite direction of that of modern, ornithurine birds." "These
opposite birds are included in the same subclass, the Sauriurae, with the
urvogel, Archaeopteryx...."
So, I assume that the
original statement,.. that the arctometatarsalian condition is " reversed
" in archaeopteryx, and enantiornithine (sp),.. dosen`t imply that it is in
the process of being undone, but that the condition, unlike the
arctometatarsalian, has the bones fused principally at the proximal end. The
Ornithurae would, as implied by Feduccia, have the arctometatarsalian condition,
and therefore shouldn`t be grouped with the other two.
As to what it all means
to evolutionary theory in general, I think Feduccia is implying that archie is
not to be considered as a direct link to the modern ornithurine
birds. Larry Febo (dinosaur researcher).
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