AA << found that just three traits explained most variation in diversification and species numbers among phyla: the most successful phyla have a skeleton (either internal or external), live on land (instead of in the ocean), and parasitize other organisms. >>
<< Other traits, including those that might seem more dramatic, had surprisingly little impact on diversification and species numbers: evolutionary accomplishments such as having a head, limbs, and complex organ systems for circulation and digestion don't seem to be primary accessories in the evolutionary "dress for success." >>
<< "Parasitism isn't correlated with any of the other traits, so it seems to have a strong effect on its own," said Wiens [John Wiens]. >>
How to be winner in the game of evolution. Jan. 13, 2017
https://m.phys.org/news/2017-01-winner-game-evolution.html
Tereza Jezkova, John J. Wiens. What Explains Patterns of Diversification and Richness among Animal Phyla? The American Naturalist (2017). DOI: 10.1086/690194
http://www.journals.uchicago.edu/doi/10.1086/690194