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Lumping Taxa -- Part One: Introduction



  Lumping taxa: An inelegant name for a neccessary
practice.

  1. Introduction
  ---------------

  Taxonomic paradoxes usually involve nomina dubia and
whatnot. With new forms being described around the
globe in what seem like a faster and faster rate as
the months go by, we wonder if maybe some new genera
will be sunk into older genera. This is the problem
with either incomplete comparison, the rush to
publish, or a brevity in understanding of the
material. If people wonder why some studies take so
long to publish, involving new taxa that "I just want
to see it, 'cause I'm tired of waiting" -- Sheesh. My
hair ain't going grey anytime soon -- they should sit
back and look at the time it has taken some studies to
publish and find out how well-done they were. For
instance, taxa being described now or in the near
future may be held back to await forthcoming studies.

  Recently, problems involving the possible lumping of
coelophysids, baryonychine spinosaurids,
velociraptorines, dicraeosaurines, oviraptorids, etc.
has met with some fright. Usually arguments for
support of multiple monospecific genera in one small
select group have met with some dismay, and are based
on a few characters suggested as having great weight,
or on the geographic separation for the type. Unusual
regional diversifaction in modern animals is
occasionally reflected in the fossil record, and
fossil subspecies have been named in partial
reflection of this. Fossil Mesozoic mammals of the
Upper Cretaceous (Senonian) North American and
Mongolian formations in particular demonstrate often
minute specializations in the braincase that can be
telling in many ways of a true diversity that would
somehow warrent giving the form a new name. Take a
form that exhibits very similar morphology, and you
might describe a new species. As recent paleontology
has shown, however, more new genera with new species
are being described than just species, or just genera.
Even distinghuishing a particlar species from a
multispecies assemblage may not always be justifiable,
if the type of the genus is scrappy, in site of the
better new genus material.

  *Megalosaurus* and *Titanosaurus*, the two most
infamous dinosaurian "trash-bin" taxa, have had a
great deal of different sub-taxa named, under the
principle of generalization. Now this is all fine and
dandy: some of the forms described under these genera
have proven to be wildly different forms in the
phylogenetic sense. Brachiosaurids and so on have been
removed from *Titanosaurus,* dilophosaurs and
abelisaurs from *Megalosaurus,* even the spinosauroid
*Eustreptospondylus.* But more recently, numerous taxa
are named from forms that do not in fact display such
morphological diversity, under the general premise
that some small variation might justify generic-level
distinction.

  Examples in the coelophysoids include a grand total
of 7 species cannot be extremely separated from
*Coelophysis bauri,* and are inferred as general
coelophysids. The spinosaurid problem is another
interesting scenario, where geographical separation is
a major issue, but forms may imply one genus of
baryonychine, perhaps three genera of spinosaurine.
Velociraptorine dromaeosaurids are distinguished one
from another often on the basis of proportions and
details that, to the larger extent, may be inferred as
functional characters, feeding adaptations, etc., and
are highly subject to change even within
tightly-restricted genomic populations, like *Homo
sapiens sapiens*. The recent discussion on
dicraeosaurines has brought to the fore the subject of
genetic parenting and paraphyly in natural groups, and
distinghuishing taxa from within parent-daughter
groups. Oviraptorids are like crocodiles in that they
exhibit extreme morphological variation in rather
short space and time, but may constitute a remarkable
case of convergence towards various evolutionary
selective pressures.

  Ankylosaurs are often diagnosed on osteodermal
bones, the position of certain nerve openings in the
braincase, proportions of the head, etc. In theropods
and other archosaurs, including crocodiles, this is
often insufficient evidence to consider entire generic
assignments for partial braincases in ankylosaurids
like *Nodocephalosaurus,* etc. Iguanodonts are perhaps
well-lumped, but recent distinguishing features have
separated *Probactrosaurus* and *Ouranosaurus* as
hadrosaur-like; and more recent data place new taxa
along the series. Iguanodontidae may be nothing but a
grade. I will not approach hadrosaurids or other
sauropod without a more comprehensive understanding of
the forms, and unless Weishampel, Horner, and the
Argentine crew descend from Fossil-land on rays of
actinofibrils, I probably won't anytime soon.

  I will try to summarize my premise in parts:

Contents

1. Introduction

2. Discussion of Taxa

  A. Saurischians
    i. Coelophysoids
    ii. Spinosaurids
    iii. Velociraptorines
    iv. Dicraeosaurines
    v. Oviraptorids
  B. Ornithischians
    i. Ankylosaurs: case study, Shamosaurines
    ii. Iguanodonts

3. Summary and Concensus

----------------

  This is an extensive series on my part, and I
probably won't finish anytime soon; this may take me
over a week to fully write and post. I am very
opinionated on this subject ;) Try not to reply to
this intro unless you feel I should elaborate on the
general premise. I have previously written to the list
on some taxa above, on others not due to reference
gathering and reading. I've been catching up on my
thoeries of evolution and applied taxonomy, so I'm
feeling a little brave.

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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