1. As I said, all known diapsids have irreversibly lost ureotelism. Diapsids are also uricotelic. But the ability to excrete urea is universal among amniotes (it probably evolved in the amniotic egg as a means to conserve water), so uricotelism is not the synapomorphy of the diapsids and their descendants (the birds). The lost of ureotelism is perhaps a lot like the lost of limbs in tetrapods: in neither case is there evidence that it can re-evolve once it is lost. Therefore the defining synapomorphy of the diapsids (besides the skull openings) is the irreversible lost of ureotelism. Turtles are probably not diapsids because they do not share this synapomorphy.

2. Many of Gauthier's ideas (that the synapsids split off first, that Reptilia should include birds, and that birds are descendants of a highly derived theropod) appear to have become cladistic dogma. Many cladists are defending these ideas using unparsimonious and/or scientifically untenable arguments, such as the idea that feathers may have evolved twice or that flight evolved from the ground up. Some of Gauthier's analyses have been criticized as being based on known symplesiomorphs and are therefore unreliable. Groups that are united on the basis of ancestral characters may be polyphyletic, as Gould pointed out in Wonderful Life.

3. Not so. The two mammalian lineages should form a single lineage. Take a look at Rodriguez-Robles et al.'s (2001, Mol. Phylogenetics and Evol. 18(2):227-237) cladogram, for example. The outgroup species they choose do not form an unresolved polytomy with the rubber boa at the base of the tree, unlike Rest et al.'s study.

4. Adding an amphibian would provide an unequivocal outgroup. It would result in a more robust phylogeny. Right now the choice of two mammals as outgroup may have resulted in the erroneous coding of some molecular synapomorphies as symplesiomorphs. Rest et al. would have eliminated the possibility that they had chosen a member of the ingroup as an outgroup by picking an amphibian (Lissamphibian) as an outgroup, even if they are confident that they did not owing to their belief that Gauthier's original analysis is unchallengeable scientific fact. They may have been tripped up by cladistic dogma.

5. Indeed, if the addition of an amphibian as outgroup changes the ingroup relationships, then turtles may not come out as descendants of a diapsid. If it does not change the topography of the cladogram, then it would lend support to the results. As it stands, the results appear unreliable. Either way, the results would be more reliable if an amphibian is picked as the outgroup.

6. Darwin emphatically rejected cladism when he i) championed character analysis (i.e ascertaining character goodness and homology) and ii) showed with an example how he would classify on the basis of not only branching order but morphological disparity. Darwin showed us how he would delimit taxa so that the resultant taxa may be paraphyletic if the descendants differ greatly from the parental taxa and how he would place the descendants in the same genus as the ancestor if little evolutionary change had taken place in a lineage. The cladists differ from Darwin and the Darwinians by ignoring morphological disparity in their classifications and by their intolerance of paraphyletic taxa.

7. Your declaration that Feduccia is "wrong" is little more than a re-assertion of current cladistic dogma, which has now been disproven by the discovery of Longisquama feathers. The likelihood that feathers evolved twice is even lower than the likelihood that limbs can reappear after it has been lost in a lineage. Feathers unequivocally evolved in the Triassic, well before the bird-like theropods evolved. Gauthier's cladogram requires not only that bird-like dinosaurs evolved not later than the Jurassic and then remain undetected in the fossil record until the late Cretaceous. But since the result of Gauthier's analysis has become cladistic dogma, the cladists will simply ignore the "mountain of evidence" that the opponents of the theropod origin of birds have accumulated in the past few decades. It takes an irrational person to believe that evolution is not a fact. It would take an equally irrational person to believe that birds evolved from a theropod, given the fact that many well preserved theropod skins show no evidence of feathers but the feathers of Longisquama display many of the unmistakable anatomical and developmental details of bird feathers.

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