Re: Why deuterostomes?

On 3/7/24 8:10 AM, Ted wrote:

John Harshman wrote:
 

On 3/6/24 10:44 AM, Ted wrote:

I recently read about the difference between protostomes and
deuterostomes. Are there any ideas why they reversed the order?
 

 

None to my knowledge. Nor do we know which came first. And there
are at least two separate groups with the deuterostome condition,
since brachiopods do.

 
 
Thanks John. Wow. Then the deuterostomes arose twice?
 

Technically, no. The deuterostomes are a monophyletic taxon that
includes chordates, echinoderms, and hemichordates. It's just that
other groups also have the blastopore give rise to the anus. You
wouldn't say that birds arose twice because bats have wings. And it
might also be that deuterostomy is primitive, so that it's protostomy
that arose more than once.