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Re: Monotreme-like spalacothere (today's Nature)



<snip>
important mammalian fossils of the past decade - notably a series of
feathered dinosaurs -
<snip>
didn't know feathered dinosaurs were therians :-o
Jean-Michel

----- Original Message -----
From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, January 11, 2006 9:46 PM
Subject: Monotreme-like spalacothere (today's Nature)


>
> The Yixian Formation coughs up another furball.  This one is named
> _Akidolestes cifellii_, and is based on a nearly complete skeleton with
fur
> impressions.
>
> Gang Li and Zhe-Xi Luo (2006).  A Cretaceous symmetrodont therian with
some
> monotreme-like postcranial features.  Nature 439: 195-200.
>
> Abstract: "A new spalacotheriid mammal preserved with a complete
postcranium
> and a partial skull has been discovered from the Yixian Formation of
> Liaoning, China.  Spalacotheroid symmetrodonts are relatives to modern
> therians (combined group of marsupials and placentals) and are
characterized
> by many skeletal apomorphies of therians.  But unlike the closely related
> spalacotheroids and living therians, this new mammal revealed some
> surprisingly convergent features to monotremes in the lumbar vertebrae,
> pelvis and hindlimb.  These peculiar features may have developed as
> functional convergence to locomotory features of monotremes, or the
presence
> of lumbar ribs in this newly discovered mammal and their absence in its
> close relatives might be due to evolutionary developmental homoplasy.
> Analysis including this new taxon suggests that spalacotheroids evolved
> earlier in Eurasia and then dispersed to North America, in concordance
with
> prevailing geodispersal patterns of several common mammalian groups during
> the Early Cretaceous period."
>
> "Etymology. _Akidolestes_: akido- (Greek) for point, for the pointed
rostrum
> of this new mammal; -lestes (Greek), for thief, a common suffix for the
name
> of fossil mammals; cifellii, in honour of Richard L. Cifelli, for his
> pioneering studies of symmetrodont mammals."
>
> >From the Editor: "The Yixian Formation in China has yielded some of the
most
> important mammalian fossils of the past decade - notably a series of
> feathered dinosaurs - and continues to produce fossils that challenge
> conventional wisdom about the evolution of early mammals.  The latest is a
> well preserved 'spalacotheroid symmetrodont', a relative of the modern
> therians (the marsupials and placentals).  Parts of its skeleton are very
> un-therian like: from lumbar vertebrae down to the ankle, this mammal is
> very like the platypus, perhaps as a result of functional convergence.
This
> new fossil is also of interest from the palaeobiogeography perspective.
> Like many other mammals in the Early Cretaceous, spalacotheroids seem to
> have evolved initially in Eurasia and then to have dispersed to North
> America."
>
> Cheers
>
> Tim
>
>
>
>