quote:Does all the data contradict or support the conclusions, i.e., morphologically and molecularly, do they say the same thing? If not, is there something wrong with one methodology? Both? And what should be done next?
This seems to be the crux of the matter. It seems that convergent evolution may limit the construction of phylogenies by morphology alone. It would seem to me that molecular phyolgenies based on DNA studies would more accurately measure divergence times relative to different lineages. I would assumed that convergent evolution of morphology is much more common than two species developing the same exact mutations. Being that the two species were in different geographic areas, they may have evolved into similar niches through the same changes in morphology. However, speciation in the separate geographic areas should not involve the same mutations (but the same genes could have been affected).
My hypothesis is that ground sloths adapted to arboreal life styles among two different groups. This is a tough hypothesis to test, as I am guessing that the numerous genera mentioned in the column represent several fossil species. Further fossil finds may not differentiate Mylodon and Nothrotheriops, but the biogeographic isolation of the two groups may help to elucidate the problem somewhat. Nonetheless, a very muddled picture indeed.
quote:I'm not sure that it would be unreasonable to accept multiple independant development of behavior such as an aboreal life. After all there are numerous examples of multiple independant inventions nearly everwhere we look.
Totally agree (which I hope is apparent in my post). However, convergent morphology shouldn't be due to convergent mutations, which is why I think the DNA sequences are more accurate than phylogenies constructed from morphology.