Determination of Polarity
Determination of Polarity
How was character polarity determined? Shouldn't a stem-primate outgroup have been included, or was this implicit?
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The sentence after the one marked as #1 in "Discussion":
"Some characters may be noted as indeterminate for Darwinius because of evidence of convergence, for example, presence of tritubercular molars in extant and early Eocene representatives of Tarsioidea means quadrate molars evolved independently and convergently in Strepsirrhini and most later Haplorhini."
I would think that assigning it to subordor Euprimates it would make Haplorhini implicit (IMO).No competing interests declared.
ps
"Of particular importance to phylogenetic studies, the absence of a toilet claw and a toothcomb demonstrates that Darwinius masillae is not simply a fossil lemur, but part of a larger group of primates, Adapoidea, representative of the early haplorhine diversification." is explicit IMO.No competing interests declared.
Perhaps I wasn't clear. You can't tell which characters are plesiomorphies or apomorphies for crown-group primates without looking at stem-group primates. E.g., if crown-strepsirrhines have trait X and crown-haplorhines don't, that tells us nothing about X's polarity with regard to the primate crown group. We have to look at stem-primates -- if they have X, then it's (probably) a plesiomorphy and the loss of X is an apomorphy of crown-haplorhines. If they don't, then the lack of X is (probably) the plesiomorphy and its presence is derived in crown-strepsirrhines.
They mark "tooth comb of lower incisors-canines" and "loss of grooming all claws" as derived in Table 3. Presumably, then, there are stem-primates with grooming claws but not tooth combs, but I don't see where this is made explicit. Same question goes for all the other traits. Is the polarity just common knowledge for people who study non-simian primates, or am I missing something?
Also, that statement seems to me to contain an unwarranted assumption. If the tooth comb is a synapomorphy of crown-strepsirrhines, then that doesn't mean that tooth combs were present in all stem-strepsirrhines. That is, when the strepsirrhine and haplorhine lineages diverged, the first members of the strepsirrhine total group almost certainly didn't instantaneously develop tooth combs. So, that trait would just as easily agree with a stem-strepsirrhine position as a stem-haplorhine position. (The grooming claw, though, if it is a plesiomorphy for crown-group primates, would indeed agree better with a stem-haplorhine position.)No competing interests declared.
I think that is the bush they are beating around. This hints that it is close to the ghost lineage that Beard's talks about in his book "Hunt for the Dawn Monkey" and that a rewrite of the taxonomy for Euprimates is needed. Considering how long the Lemur lineage has been isolated from the rest of the primate lineage they may have to do a rethink of just how far this split occurred and what is the actual stem lineage. Beard disagrees that it even close to the Tarsier lineage and presents a credible argument for it in his book. To me this fossil lends credence to his argument.
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