Some New Refs

["Jerry D. Harris" <jharris@dixie.edu>]

Hi All -

   More new papers pouring in...

Hwang, S. H. 2005. Phylogenetic patterns of enamel microstructure in 
dinosaur teeth. Journal of Morphology 266(2):208-240. doi: 
10.1002/jmor.10372.

   ABSTRACT: The tooth enamel microstructure of all the dinosaur taxa that 
are adequately represented in the American Museum of Natural History 
collections were analyzed using scanning electron microscopy. This study 
aims to determine whether or not better sampling within a major nonmammalian 
amniote (hereafter referred to descriptively as reptile) clade will unearth 
phylogenetic patterns in enamel microstructure in addition to those dictated 
by tooth function. While interest in reptile enamel microstructure has 
increased in the past few years, intensive sampling focused on just one 
monophyletic reptile clade was not previously implemented. This study 
reveals that phylogenetic constraints play a larger role in shaping enamel 
microstructure in reptiles than previously thought. Within many monophyletic 
dinosaur clades the combination of enamel types and enamel features within a 
tooth - the schmelzmuster - is the same in all the taxa due to their common 
ancestry, and their schmelzmusters are diagnostic of their respective 
clades. While distantly related taxa with similar teeth and diets have 
similar schmelzmusters due to functional constraints, phylogenetic 
constraints keep those schmelzmusters distinct from one another. An 
interesting finding of this analysis is that the enamel complexity of a 
taxon does not necessarily coincide with the position of the taxon on a 
phylogenetic tree; more derived taxa do not necessarily have more derived 
enamel and more primitive taxa do not necessarily have more primitive 
enamel.

**********

Tanimoto, M. 2005. Mosasaur remains from the Upper Cretaceous Izumi Group of 
southwest Japan. Netherlands Journal of Geosciences 84(3):373-378.

   ABSTRACT: Until recently, mosasaur remains from the Izumi Group (Upper 
Cretaceous) in southwest Japan comprised only scattered finds; now a richer 
material is available. From the upper Campanian Hiketa Formation in Kagawa 
Prefecture, _Kourisodon_ sp. has just been recorded, on the basis of 
portions of skull and mandible which has small and laterally compressed 
teeth. A few teeth of the same or similar type have previously been 
described from the Maastrichtian Mutsuo Formation in Osaka Prefecture. A 
report of _Mosasaurus_ sp. A, which resembles _M. missouriensis_ and _M. 
dekayi_, is based on some cranial and mandible remains, inclusive of 
numerous teeth and a few well-preserved cervical and two incomplete dorsal 
vertebrae, from the Maastrichtian Mutsuo Formation in Osaka Prefecture. A 
slender tooth of _Mosasaurus_ sp. from the Mutsuo Formation has since been 
reassigned to _Platecarpus_ (Plioplatecarpinae); yet, this may indeed by a 
species of _Mosasaurus_, here listed as _Mosasaurus_ sp. B. To date, smaller 
specimens of mosasaurids have been shown to be abundant in the Izumi Group, 
which suggests two possible explanations. Either most of these represent 
juveniles, or smaller-sized, _Kourisodon_-like animals flourished here. 
Finds of _Kourisodon_ sp. from the upper Campanian Hiketa Formation and the 
Maastrichtian Mutsuo Formation suggests the second explanation is the more 
likely one.

**********

Müller, K. F. 2005. The efficiency of different search strategies in 
estimating parsimony jackknife, bootstrap, and Bremer support. BMC 
Evolutionary Biology 2005(5):58. doi: 10.1186/1471-2148-5-58.  (Available 
free on-line at: 
http://www.biomedcentral.com/content/pdf/1471-2148-5-58.pdf)

   ABSTRACT: Background: For parsimony analyses, the most common way to 
estimate confidence is by resampling plans (nonparametric bootstrap, 
jackknife), and Bremer support (Decay indices). The recent literature 
reveals that parameter settings that are quite commonly employed are not 
those that are recommended by theoretical considerations and by previous 
empirical studies. The optimal search strategy to be applied during 
resampling was previously addressed solely via standard search strategies 
available in PAUP*. The question of a compromise between search 
extensiveness and improved support accuracy for Bremer support received even 
less attention. A set of experiments was conducted on different datasets to 
find an empirical cut-off point at which increased search extensiveness does 
not significantly change Bremer support and jackknife or bootstrap 
proportions any more.
   Results: For the number of replicates needed for accurate estimates of 
support in resampling plans, a diagram is provided that helps to address the 
question whether apparently different support values really differ 
significantly. It is shown that the use of random addition cycles and 
parsimony ratchet iterations during bootstrapping does not translate into 
higher support, nor does any extension of the search extensiveness beyond 
the rather moderate effort of TBR (tree bisection and reconnection branch 
swapping) plus saving one tree per replicate. Instead, in case of very large 
matrices, saving more than one shortest tree per iteration and using a 
strict consensus tree of these yields decreased support compared to saving 
only one tree. This can be interpreted as a small risk of overestimating 
support but should be more than compensated by other factors that counteract 
an enhanced type I error. With regard to Bremer support, a rule of thumb can 
be derived stating that not much is gained relative to the surplus 
computational effort when searches are extended beyond 20 ratchet iterations 
per constrained node, at least not for datasets that fall within the size 
range found in the current literature.
   Conclusion: In view of these results, calculating bootstrap or jackknife 
proportions with narrow confidence intervals even for very large datasets 
can be achieved with less expense than often thought. In particular, 
iterated bootstrap methods that aim at reducing statistical bias inherent to 
these proportions are more feasible when the individual bootstrap searches 
require less time.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

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from outer space would say "I want to
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