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Other Devonian Tetrapod Projects
As well as Acanthostega and Ichthyostega, I have worked on a number
of other Devonian tetrapod taxa, in collaboration with colleagues.
Ymeria denticulata
Published with Per Ahlberg, Henning Blom and Sarah Finney
(Clack et al. 2012),
Ymeria
is a new taxon of tetrapod from the Devonian of East Greenland. It is
similar in some ways to
Ichthyostega, but is distinguishable mainly
on dentition. Its tooth shape is quite different from
Ichthyostega,
and it has areas of dense denticulation on its lower jaw, hence the specific
name.
It was found in 1947 by a Swedish-Danish expedition, and Jarvik did not think
it was a specimen of
Ichthyostega. Our studies showed his instinct was
correct. The name derives from Ymer Ø (Ymer Island) and also refers to the
ancient Norse god Ymer, the giant from whose body the world was created in
Scandinavian mythology. (The journal would not let us include this in the
etymology because Ymer is male and
Ymeria is female.)
Ventastega curonica
In 2008, I contributed to the description of new and exquisite material of the
Famennian tetrapod
Ventastega curonica from Latvia
(
Ahlberg et al. 2008). This new material
showed that
Ventastega retained a number of primitive features not seen
in other tetrapods, and that its spiracular region and posterior skull roof were
most closely similar to the near-tetrapod
Tiktaalik rosea. It appeared
to be the most primitive known tetrapod at the time of its publication.
Red Hill, Pennsylvania
With colleagues, Ted Daeschler and Neil Shubin (
Daeschler et al. 2009) I studied some of the
isolated bones recovered from the Famennian site of Red Hill, from which
specimens of
Hynerpeton and
Densignathus were found. Several taxa
appear to be represented among these elements, including a lacrimal bone that
most closely resembles that of the whatcheeriid
Pederpes. If this is
indeed the case, the whatcheeriids are the only clade known so far to cross
the Devonian/Carboniferous boundary.
South Timan, Russia
Ongoing discovery, collection, preparation and description is taking place of
beautiful new material from northern Russia of a tetrapod that may be even
more primitive than Ventastega. Funding has been secured from the
National Geographic Society for enlarged excavations of the riverside site
during the summer of 2012 or 2013. Per Ahlberg and I are working on this with
our Russian colleague Pavel Besnosov.