Data from: Rise and diversification of chondrichthyans in the Paleozoic

The Paleozoic represents a key time interval in the origins and early
diversification of chondrichthyans (cartilaginous fishes), but their
diversity and macroevolution are largely obscured by heterogenous spatial
and temporal sampling. The predominantly cartilaginous skeletons of
chondrichthyans pose an additional limitation on their preservation
potential and hence on the quality of their fossil record. Here, we use a
newly compiled genus-level dataset and the application of sampling
standardization methods to analyze global total-chondrichthyan diversity
dynamics through time from their first appearance in the Ordovician
through to the end of the Permian. Subsampled estimates of chondrichthyan
genus richness were initially low in the Ordovician and Silurian but
increased substantially in the early Devonian. Richness reached its
maximum in the middle Carboniferous before dropping across the
Carboniferous/Permian boundary and gradually decreasing throughout the
Permian. Sampling is higher in both the Devonian and Carboniferous
compared with the Silurian and most of the Permian stages. Shark-like
scales from the Ordovician are too limited to allow for some of the
subsampling techniques. Our results detect two Paleozoic radiations in
chondrichthyan diversity: the first in the earliest Devonian, led by
acanthodians (stem-group chondrichthyans), which then decline rapidly by
the late Devonian, and the second in the earliest Carboniferous, led by
holocephalans, which increase greatly in richness across the
Devonian-Carboniferous boundary. Dispersal of chondrichthyans,
specifically holocephalans, into deeper water environments may reflect a
niche expansion following the faunal displacement in the aftermath of the
Hangenberg extinction event at the end of the Devonian.