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RE: The New Paper at the End of the Universe (Was: Hitchhiker's New Papers to the Galaxy)



Generally good paper, but Rose doesn't seem to understand the meaning of "phylogenetically informative" in the sense of characters in phylogenetic analyses. He states-

"Repeating the PAUP analysis with the latter character excluded does not alter the topology of the three most parsimonious cladograms. Thus, the ratio of transverse breadth to craniocaudal length in cranial caudal neural spines may be a phylogenetically uninformative character for sauropods.

Two characters in the phylogenetic analysis describe the number of presacral vertebrae in sauropods.
The amount of homoplasy in the character state distributions may, in part, be a function of missing data in the character matrix as a whole. More likely it indicates that these characters are also phylogenetically uninformative; deleting these characters from the analysis has no effect on the topology of the most parsimonious cladograms."


The ability to remove a character from an analysis and get the same tree does not indicate the character is phylogenetically uninformative. It merely shows other characters exist to compensate for its loss. You could remove the character "feathers" from a vertebrate analysis, and coelurosaurs would still strongly clade together. But feathers are certainly a phylogenetically informative character.

Similarly, a high amount of homoplasy does not indicate a phylogenetically uninformative character. Toothlessness is very informative in that it helps group ornithomimids, caenagnathids, confuciusornithids and neornithines in their clades, even though it is convergent between these four clades.

In fact, the only time a character is technically phylogenetically uninformative is when it has no homoplasy - when it is only present in one included taxon, so that by itself it has no effect on tree topology. This either means it's an autapomorphy of an ingroup taxon or a synapomorphy of the ingroup only missing in the outgroup.

Mickey Mortimer


From: Mike Taylor <mike@indexdata.com>
Reply-To: mike@indexdata.com
To: jharris@dixie.edu
CC: DINOSAUR Mailing List <dinosaur@usc.edu>
Subject: The New Paper at the End of the Universe (Was: Hitchhiker's New Papers to the Galaxy)
Date: Wed, 15 Aug 2007 12:20:34 +0100


Jerry D. Harris writes:
 > Hi All -
 >
 > Before we get to the juicy stuff, here's some new things:
 > [snip]

But, Jerry, you missed the highlight: a new, and well-represented
brachiosaurid!

        Rose, Peter J.  2007.  A new titanosauriform sauropod
        (Dinosauria: Saurischia) from the Early Cretaceous of central
        Texas and its phylogenetic relationships.  Palaeontologia
        Electronica 10 (2): 8A.
        http://palaeo-electronica.org/2007_2/00063/

ABSTRACT

A collection of primitive titanosauriform sauropods from the Jones
Ranch locality, Early Cretaceous Twin Mountains Formation (~112 Ma),
central Texas, represents one of the richest accumulations of sauropod
bones in North America. Autapomorphic characters of the taxon include
cranial and mid-caudal neural arches with distinct
intraprezygapophyseal laminae (tprl), accessory vertebral laminae on
cranial dorsal neural arches, and dorsal neural spines that lack a
postspinal lamina.

Non-vertebral skeletal elements referred to the genus Pleurocoelus
from the Arundel Formation of Maryland and Virginia possess some
diagnostic morphological characteristics and can be compared with the
Jones Ranch sauropod. The latter differs from Pleurocoelus in the
shape of the caudoventral margin of the maxilla, the shape of the
distal scapular blade, and the shape of the proximal condyle of the
tibia. The Jones Ranch sauropod is also morphologically distinct from
all other sauropods described and named from the Early Cretaceous of
North America.

Cladistic analysis places this sauropod within Titanosauriformes. The
Texas sauropod does not possess synapomorphies of Somphospondyli, and
derived characters that have been used to define the Titanosauria are
also absent, affirming its placement as a basal titanosauriform. The
new taxon from Texas is known from more material than any other North
American Early Cretaceous sauropod. Description of the taxon increases
the diversity of sauropods in North America during the Early
Cretaceous and provides more complete, associated material that can be
compared to new discoveries from this time period.

_/|_ ___________________________________________________________________
/o ) \/ Mike Taylor <mike@indexdata.com> http://www.miketaylor.org.uk
)_v__/\ Archosaurs rule!