Data from: Exceptions to the temperature-size rule: No Lilliput effect in end-Permian ostracods (Crustacea) from Aras Valley (NW Iran)

The body size of marine ectotherms is often negatively correlated with
ambient water temperature, as seen in many clades during the hyperthermal
crisis of the end-Permian mass extinction (c. 252 Mya). However, in the
case of ostracods, size changes during ancient hyperthermal events are
rarely quantified. In this study, we evaluate the body size changes of
ostracods in the Aras Valley section (NW Iran) in response to the drastic
warming during the end-Permian mass extinction at three taxonomic levels
(class, order, species). On the assemblage level, the warming triggers a
complete species turnover in the Aras Valley section, with larger, newly
emerging species dominating the immediate post-extinction assemblage for a
short time. Individual ostracod species and instars do not show dwarfing
or a change in body size as an adaptation to the temperature stress during
the end-Permian crisis. This may indicate that ostracods might be
exceptions to the temperature-size rule (TSR), using an adaptation
mechanism that does not involve a decrease in body size. Many recent
experimental studies show that accelerated development without size
changes is a common response of modern ostracods to thermal stress.