Complex sentence: Indeed, the entire phylogeny of the Ostariophysans (fishes possessing a Weberian apparatus) has yet to be conclusively settled, and until that phylogeny is settled, the opportunity for yet more upheavals within the taxonomy of the Characoid fishes is considerable.
Split into simpler sentences: Indeed, the entire phylogeny of the Ostariophysi-fishes possessing a Weberian apparatus-has yet to be conclusively settled. Until that phylogeny is settled, the opportunity for yet more upheavals within the taxonomy of the characoid fishes is considerable.