Abstract

The Parareptilia are a small but ecologically
and morphologically diverse clade of Permian and Triassic
crown amniotes generally considered to be phylogenetically
more proximal to eureptiles (diapsids and their kin) than
to synapsids (mammals and their kin). A recent supertree
provides impetus for an analysis of parareptile diversity
through time and for examining the influence of the end-
Permian mass extinction on the clade’s origination and
extinction rates. Phylogeny-corrected measures of diversity
have a significant impact on both rates and the distribution
of origination and extinction intensities. Time calibration
generally results in a closer correspondence between
origination and extinction rate values than in the case of
no time correction. Near the end-Permian event, extinction
levels are not significantly higher than origination levels,
particularly when time calibration is introduced. Finally,
regardless of time calibration and ⁄ or phylogenetic correction,
the distribution of rates does not differ significantly
from unimodal. The curves of rate values are discussed in
the light of the numbers and distributions of both range
extensions and ghost lineages. The disjoint time distributions
of major parareptile clades (e.g. procolophonoids and
nycteroleterids-pareiasaurs) are mostly responsible for the
occurrence of long-range extensions throughout the Permian.
Available data are not consistent with a model of sudden
decline at the end-Permian but rather suggest a rapid
alternation of originations and extinctions in a number
of parareptile groups, both before and after the Permian ⁄
Triassic boundary.