Re: Sereno's (2005) new definitions

["Jaime A. Headden" <qilongia@yahoo.com>]

David Marjanovic (david.marjanovic@gmx.at) wrote:

<I never said any such thing. What I said was that we can be sure that the
holotype tooth of *T. formosus* belongs somewhere inside the clade currently
called Troodontidae (and not very close to its root).>

  My bad, #1. An earlier email I had chosen not to reply to specifically had
mentioned this, and it seems it may have been a reply to a statement by Mickey.
Nonetheless, I have answered this extensively elsewhere.

<If we use *Saurornithoides mongoliensis* but not *Troodon formosus* as an
internal anchor, the name should be Saurornithoididae and not Troodontidae.>

  Indeed.

<Do you mean Coelurosauria instead of Tetanurae, or ceratosaurs instead of
carnosaurs?>

  Yes, my bad #2.

  Here's some personal suggestions:

  Theropoda = {Megalosaurus + Passer not Cetiosaurus, not Iguanodon}

  Neotheropoda = {Passer + Ceolophysis/Ceratosaurus}

  Ceratosauria = {Ceratosaurus + Coelophysis + Abelisaurus not Passer}
[conditional]

  Coelophysoidea = {Coelophysis not Ceratosaurus}

  [I am sure that a conditional clade can be provided should Coelophysidae have
more than *Coelophysis* in it, but given some plausible placement for
*Dilophosaurus* closer to birds than is *Coelophysis*, but not as close as
*Ceratosaurus*, we may need to simply restrict it to ...

  Coelophysidae = {Coelophysis + Segisaurus not Dilophosaurus, not
Ceratosaurus}

  Neoceratosauria = {Ceratosaurus + Abelisaurus, not Coelophysis} [conditional,
I am not sure if this should not also exclude Dilophosaurus]

  Ceratosauridae = {Ceratosaurus not Abelisaurus, not Coelophysis}

  Abelisauria = {Abelisaurus + Elaphrosaurus + Noasaurus}

  Abelisauroidea = {Noasaurus + Abelisaurus, not Elaphrosaurus}

  Abelisauridae = {Abelisaurus not Elaphrosaurus, not Noasaurus}

  Noasauridae = {Noasaurus, not Abelisaurus, not Elaphrosaurus}
  [Conditional, the topology (Abelisaurus (Noasaurus, Elaphrosaurus)) is also
possible]

  [I would recognize two more "families" here, for *Elaphrosaurus* and another
abelisaur and their allies, where allies of these taxa appear to indicate they
are more robust than simply terminal outgroups, but this is pending a thourough
review of ceratosaur phylogeny and anatomical study, which is only partially
complete by myself, and virtually complete by Carrano et al., and Sereno et
al.]

  Tetanurae = {Passer not Ceratosaurus, not Ceolophysis, not Abelisaurus}

  Neotetanurae = {Passer + Megalosaurus, not Baryonyx/Spinosaurus}

  Avetheropoda = {Allosaurus + Passer}

  Carnosauria = {Allosaurus, not Passer, not Megalosaurus, not
Baryonyx/Spinosaurus}

  Allosauroidea = {Allosaurus + Carcharodontosaurus + Sinraptor}
  [It is possible to avoid "idae" ir "inae" issues by also naming "ia" clades
for each specifier here, if they are not monotypic]

  Coelurosauria = {Passer not Allosaurus, not Carcharodontosaurus}

  There is no reason to be overly complex, but sometimes it seems important to
do so. Topologies within Coelurosauria fluctuate depending on the analysis,
more than any other (Holtz's 1999 "rule" of clades beginning with T), and we
may want to name some conditional clades for some of these, or define names in
odd new names for this. I think Tyrannoraptora is just as useful as a
Compsognathidae, *Compsognathus* + *Passer* clade, and so forth. I think a
tyrant dinosar clade name for the stem of Tyrannosauroidea is useful, as well.
As for the commonly accepted clade names for names ending in -idae which are
commonly used as specifiers before the last few years, we can use the eponymous
internal specifier, and at least two external specifiers, including *Passer
domesticus* Linnaeus, and one other suggested specifier given topological
variation. Other clade names, we may need to specify, for some, three or more
external specifiers, such as Therizinosauroidea, Bullatosauria,
Arctometatarsalia, Ornithomimoidea, which have debated contents.
Deinonychosauria will have a conditional definition so that it only exists,
rather than being a heterodefinitional synonym, in a given situation, such that
*Troodon* (or an adequant exception) and *Dromaeosaurus* share an ancestor
exclusive to birds, while a clade name can be coined for the *Dromaeosaurus*
stem leading from birds, which can be highly useful rather than using
Dromaeosauridae for that stem, as this now appears problematic with
Microraptoria and Unenlagiinae.

  But this is the familiar ground for many of us. More problems increase with
less familiar sauropods, which around the Neosauropoda and Eusauropoda tend to
be very variable in topology, as well as basal Titanosauriformes and
Titanosauria.

  In ornithischians, the problem drastically increases, not just because of the
lack of familiarity among most of us, but because the main "suborders" are not
entirely consistent in arrangement, and a big culprit may very well be
*Heterodontosaurus*. Another curiousity is the apparent artifacts in producing
either stewise advancement of ornithopods towards hadrosaurs, withc each new
taxon a step out from a more inclusive grouping, in a successively nested
arrangement, versus sets of pairs or more of taxa. Is there a
Hypsilophodontidae? A Tenontosauridae? A Rhabdodontidae? A Rhabdomorpha? An
Iguanodontidae? A Probactrosauridae? Hadrosauridae is so substantially diverse,
along with Ankylosauridae that convention is likely all that keeps it from
staying an -idae, along with perhaps Ceratopsidae (that and relative
postcranial similarity or ignorance).

  We have a long way to go before we start simply decided we are ata a state to
propose EASY definitions. I claim, as does Sereno, that we need TIME to work
the bugs, and not just declare a system that will avert many systematists from
using phylogenetic nomenclature.

  Cheers,

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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