Talk:Phylogenetic bracketing

EPB

Cool; I was a bit asleep at the switch last night. Besides, when I think of Witmer and bracketing, I usually think of EPB. J. Spencer 13:14, 21 June 2007 (UTC)

A really bad example

The section Example of bracketing with one extinct and one extant group claims to infer characteristics of Jurassic mammals by bracketing between Thrinaxodon and modern shrews and marsupial mice. The conclusion drawn is that the Jurassic mammals were "small, nocturnal, insectivorous dwellers of the undergrowth".

There is good fossil evidence that Jurassic mammals were small, nocturnal, and insectivorous. To evaluate the inference in the article, we need to pretend to be ignorant of this evidence and consider just what phylogenetic bracketing can tell us. Can we conclude that they were small and insectivorous? Hardly, because the modern-day mammals being considered were chosen just because they are small and insectivorous. We could as easily decide that the Jurassic mammals were large herbivores because they are phylogenetically bracketed by Exaeretodon and oxen. If there is enough variation in reference taxa, one can show just about anything.

And nocturnal? Is there is any evidence that Thrinaxodon was nocturnal? Endocast evidence on the sizes of the olfactory regions of the animals' brains favors nocturnality for Jurassic mammals but not for Thrinaxodon.

"Dwellers of the undergrowth"? If there is one thing we do know about Thrinaxodon, it is that the animal was fossorial, not an inhabitant of the undergrowth. Some shrews are fossorial as well. This one is a nonstarter.

Suggestions for better examples are welcome. It has occurred to me that, while there is no direct evidence of hair in any Triassic mammal, the fact that Tikitherium is phylogenetically bracketed by Castorocauda and modern mammals makes a Triassic origin of hair quite probable. If it's in the literature, this would be a nice case.

Peter M. Brown (talk) 16:44, 4 August 2012 (UTC)

Agreed, I kind of drew the current one out of my hindquarters so to speak. Petter Bøckman (talk) 18:39, 5 August 2012 (UTC)