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Pete Buchholz
wrote-
Although the analysis that I ran
including Jeholosaurus came up with this
result, I don't think it's correct. T. dossi comes out as more basal than T. tilletorum because of this single character: T dossi has a single set of premaxillary teeth. The analysis additionally was only skull data. A full analysis with postcranial data demonstrates that Tenontosaurus is probably monophyletic. Hmm. According to Winkler et al. (1997), Tenontosaurus dossi is more primitive than T. tillettorum in several aspects- premaxillary teeth present (although only the root of one tooth is preserved, weathering of the bone makes it uncertain how many more were originally present); longer postpubis; larger metatarsal IV; brevis shelf absent; less cheek teeth; less denticulated predentary; less everted premaxilla; single ventral predentary process. The synapomorphies making Tenontosaurus monophyletic seem very questionable to me- tall snout; square orbit; 12-16-5-60 vertebral count; 2-3-3-1-1 manual phalangeal formula. The first two seem quite vague. Only relatively complete manus of "Yandusaurus" multidens, Hypsilophodon and ankylopollexians are known among ornithopods, so many taxa (Rhabdodon, Dryosaurus, etc.) could have had such a formula. The distal caudals of T. dossi are unknown, and the dorsal and sacral counts are identical to Camptosaurus. This leaves the presence of twelve cervicals as the diagnostic part of this character. I'm not all too impressed with the evidence T. dossi belongs in Tenontosaurus. Mickey Mortimer
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