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Defunct Genera and Ceratospids



Tim Williams wrote:

<<_Brachyceratops_ and _Monoclonius_ (for the
Centrosaurinae)>>

David Marjanovic wrote:

<What have these been sunk into, and why?>

  Presumably, it has been suggested that *Monoclonius*
be dropped as a nomen dubium without validity and
largely incomparable to other ceratopsids. Most
species have been removed into *Centrosaurus* and
*Styracosaurus.* It has also been suggested (no cites
right now) that *Monoclonius* and *Centrosaurus*
represent the same taxon. However, the type for *m.
crassus,* type species, is distinct from all other
centrosaurs and chasmosaurs except for possibly
*Brachyceratops* itself. I belive there was also a
suggestion that Brachy and Monoclone are sympatric and
therefore synonymous. But that may be due to
plesiomorphy. *Brachyceratops* and *Monoclonius*,
according to Dodson (1996: _Horned Dinosaurs_),
Penalski and Dodson (1999: _JVP_), do possess some
autapomorphies that would be valid relative to the
ontogeny of ceratopsids. This in support of the
position of *Avaceratops* as a valid taxon in the
basal centrosaurine lineage, to which both the
preceeding taxa and also possibly *Ceratops* could
pertain. Anyway, there's extensive literature out on
this, and Dodson's book is a good place to start from
with regard to references and discussion, though it
may not be the most authoritarian volume.

  A new centrosaurine from the Oldman Formation (_JVP_
19(suppl. to 3)) without caudal hooks and unusual
ornamentation may help resolve this position.
 
<<and _Maleevosaurus_ and _Nanotyrannus_ (for the
Tyrannosauridae) are four more genera who have bit the
dust, and to me their passing seems justified: the
most parsimonious explanation appears to be that their
"diagnostic" characters are juvenile/subadult traits. 
This only becomes apparent after comparison with
species for which growth series are known.>>

<<...and I have doubts about whether _Jurapteryx_ is a
young _Archaeopteryx lithographica_.>>

<Why?>

  Read Howgate, 1984, 1985 (_Beginnings of Birds_,
Viohl et al., (eds)), on the Eichtätt *Archaeopteryx*
which he first distinguished as a new species, *A.
recurva* then as a new genus *Jurapteryx recurva.*
Limb proportions do not appear to reflect trends in
ontogeny of the other specimens, suggesting separation.

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