Paleozoic origins of cheilostome bryozoans and their parental care inferred by a new genome-skimmed phylogeny

Phylogenetic relationships and the timing of evolutionary events are
essential for understanding evolution on longer time scales. Cheilostome
bryozoans are a group of ubiquitous, species-rich, marine colonial
organisms with an excellent fossil record but lack phylogenetic
relationships inferred from molecular data. We present genome-skimmed data
for 395 cheilostomes and combine these with 315 published sequences to
infer relationships and the timing of key events among c. 500 cheilostome
species. We find that named cheilostome genera and species are
phylogenetically coherent, rendering fossil or contemporary specimens
readily delimited using only skeletal morphology. Our phylogeny shows that
parental care in the form of brooding evolved several times independently
but was never lost in cheilostomes. Our fossil calibration, robust to
varied assumptions, indicates that the cheilostome lineage and parental
care therein could have Paleozoic origins, much older than the first known
fossil record of cheilostomes in the Late Jurassic.