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Re: SICKLE-CLAWED DINOSAURS
>The Holtz paradigm has led to wide acceptance of the idea that
>troodontids are most closely related to ornithomimosaurs because both
>share an arctometatarsalian pes and an inflated parasphenoid capsule,
>among a few other things. The two groups are Holtz' Bullatosauria.
>But the Holtz paradigm is not necessarily correct, and other workers
>- most notably Hans Sues - support a troodont-dromaeosaurid
>relationship as a result of newer analyses. The idea that
>Deinonychosauria could be reinstated is therefore possible, but
Sues' conclusion should be taken with a grain of salt most
definitely. In the text of his paper he supports Russel and Dong's and
Clark et.al. conclusions of a clade of the Ornithomimosauria,
Troodontidae, Oviraptorosauria, and Therizinosauroidea. And he brings up
evidence published in Makovicky's MS thesis supporting this clade. But
in his cladogram he brings Dromaeosauridae into it and restricts
Ornithomimidae to a sister-group of the Dromaeosauridae, Troodontidae,
Oviraptorosauria, and Therizinosauroidea. I think the purpose of the
cladogram of the cladogram was to establish the relationship of the
Oviraptorosauria and Therizinosauroidea. Plus his characters are rather
weak and many are primitive.
>Finally, sickle-claws have evolved more times than the three
>radiations you cite: they are also seen in members of the
>seriema-phorusrhacoid clade. Some fossil phorusrhacoids, like Miocene
>_Psilopterus_, has what can be considered a sickle-claw, as do some
The seriema/phorusrhacid clade is one of the best supported clades
in Aves. Plus Chandler throwing in Musophagidae ( touracos ) and a
ciconiform ( new world vultures; Vulturidae ) relationship is simply
great. This is well supported.
>Also, how do you properly define a sickle claw? Cassowaries, as
>everyone on the list should now be aware, have an elongate, very
>sharp claw that they use as a slashing/stabbing weapon - it is not
>kept raised off the ground, and is not sickle-shaped. Meanwhile, a
>number of birds of prey (true raptors) have an enlarged,
>sickle-shaped claw on digit II. In falconids this is sometimes kept
>raised when the bird is perched.
What can be passed as a raised sickle-claw ( and this is refering
to previous posts by other authors ) in some passiriforms,
falconiformes, and other preching birds is a perching adaptation. Toes
balance the body best when they are medial.
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