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Half-a-dactylus?



On February 11th David Peters wrote:


<I've matched 60 pterosaur taxa against 170 characters and PAUP came up
with a single tree.>

An analysis of this size, based on a character data set with (I presume) 
substantial missing data, and it produces a single tree? Is that an alarm bell 
I can hear?


Subsequently Peters wrote:

<One of the interesting things to emerge was this:
Cearadactylus, known only from a skull sans cranium, came out as the
sister taxon to Arthurdactylus, known only from post-crania.>

And in this single tree two taxa that do no share any overlapping elements, and 
thus no directly observable/scorable synapomorphies, are paired together. Hmmm, 
the alarm bell is ringing so loudly its about to fly right off the wall. 

Arthurdactylus, which may well belong to the same taxon as the superb 
'tree-biting' skull from the Crato Limestone Formation (now in Karlsruhe and 
will be described as a new genus and species of ornithocheirid by Frey et al. 
later this year in the Geol. Soc. volume edited by Buffetaut) is fairly 
certainly an ornithocheirid. By contrast, Cearadactylus from the rather 
(perhaps up to 10 million years) younger Santana Formation shares several 
characters in common with other ctenochasmatoids (see Unwin, 2002). So, under 
any circumstances, the synonomy of Cearadactylus and Arthurdactylus implied by 
the heading 'The head of Arthurdactylus?' seems unlikely. Cearadactylus can be 
forced into Ornithocheiroidea, or even Ornithocheiridae, but this generates a 
lot of homoplasy, which brings us back to that alarm bell again. 

Dave, at the heart of Old Europe


Unwin, D. M., 2002. On the systematic relationships of Cearadactylus atrox, an 
enigmatic Early Cretaceous pterosaur from the Santana Formation of Brazil. 
Mitteilungen Museum für Naturkunde Berlin, Geowissenschaftlichen Reihe, 4, 
237-261. 

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David M. Unwin PhD

Institut fur Palaontologie, MUSEUM FUR NATURKUNDE 
Zentralinstitut der Humboldt-Universitat zu Berlin
Invalidenstrasse 43, D-10115 Berlin, GERMANY

Email: david.unwin@rz.hu-berlin.de

Telephone numbers:
0049 30 2093 8577 (office)
0049 30 2093 8862 (department secretary)
0049 30 2093 8868 (fax)
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