| | Protostome Did You Mean protostome (Site not responding. Last check: 2007-11-07) |
 | | The branch that was leading to protostome development must have continued to be deuterostomes a while after the split, until some remote ancestor evolved into the first protostome which gave rise to all the other present and extinct species and groups within this highly successful group. |
 | | The only surviving "non-protostomian" group from the ancient deuterostomian lineage that would eventually resulted in the protostomes would have been the ancestors of the Chaetognatha (arrow worms), which still has a deuterostomian development. |
 | | Evolving a different gastrulation and another way to turning the blastopore into a new individual, which is both backwards and upside down compared to how the blastopore evolved in their ancestors, would have been very difficult for the modern and advanced species of today to do. |
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