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Euhelopodidae (was Re: Long Necks)



Wish I had the refs in front of me so I could give you more details, but I'm at home and most of my refs are at the university. Anyway, Paul Upchurch has done some excellent phylogenetic work on sauropods: a paper in 1995 with 174 osteological characters, a paper in 1998 with over 200 characters, and a paper this year on the relationships between the Nemegtosauridae and the diplodocids and titanosaurids.

Unlike most other sauropod workers, Upchurch avoided higher lever taxa (Family level and higher) and instead put genus-level taxa into his cladograms (i.e., instead of taxon Camarasauridae, taxa Camarasaurus, Brachiosaurus, Mamenchisaurus, etc.). When I get back to the university on Monday, I'll provide everyone with the exact refs and some more details, but here is the gist of his studies. Again, I emphasize that I will fill in details later, so please don't write to tell me I have no details to back this stuff up! =)

Upchurch has concluded that there is something like the Euhelopodidae, and that all the Chinese sauropods are more closely related to one another than they are to other neosauropods. Independent analysis of neck lengths in sauropods by my advisor, Mike Parrish, has shown that when you plot out neck length to body size, the Chinese sauropods cluster together as outliers to the general trend, and this would help add some weight to Upchruch's analysis.

Furthermore, Upchurch has shown that inclusion or exclusion of a single sauropod taxon can upset portions of a cladogram or change higher taxa relationships, hence his reason for using as many singular taxa as possible. Even with the missing skeletal parts of sauropods, the consistency index of his cladograms are pretty decent (around .50, which is good considering how partial and scrappy some sauropod taxa are).

All things being equal, I tend to fall on the side of Upchurch with regard to Chinese sauropods -- they do share a number of characters that would place them closer together than to other sauropods and Upchurch has tentatively suggested that perhaps some of this was due to a kind of geographic isolation which he did not elaborate on. Unlike Wilson and Sereno (1998) he included Mamenchisaurus in his data set. As Upchurch has pointed out, because our record of sauropod material belowe higher level taxa is full of conspicuous absences, there is bound to be controversy over sauropod relationships for quite a while. However, he feels that including as many taxa as possible, even while producing an incomplete data matrix, provides a clearer understanding of sauropod relationships. And, hey, it's the best we've got right now anyway.

Matt Bonnan

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