The Lilliput effect in crinoids at the end of the Oceanic Anoxic Event 2: a case study from Poland

Abstract

The Cretaceous Period (145–66 Ma) consisted of several oceanic anoxic events (120–80 Ma), stimulated by global greenhouse effects. The Oceanic Anoxic Event 2 (OAE2) occurred worldwide from the late Cenomanian to the early-middle Turonian, causing a significant faunal turnover, mostly in marine biota, pushing some species to the brink of extinction. Some organisms also underwent morphological changes, including reduction in size. This anoxic event drove other changes—e.g., in habitats or strategy of life. We show that stalkless crinoids (comatulids) from the Turonian of Poland adapted to unfavorable environmental conditions by reducing their body size. Furthermore, at the moment when environmental factors became favorable again, these crinoids regained their regular (pre-event) size. This phenomenon likely illustrates the so-called dwarfing mode of the Lilliput effect.

Body size changes in bivalves of the family Limidae in the aftermath of the end‐Triassic mass extinction: the Brobdingnag effect

“…; Brom et al . ) and may have played a role in the initially small size of bivalves after the end‐Triassic mass extinction. A productivity crash has been postulated for this crisis (Ward et al .…”

Body size trends and recovery amongst bivalves following the end-Triassic mass extinction

“…The causes and nature of size changes during mass extinction events have been much debated Brayard et al, 2010;Brom et al, 2015;Chen et al, 2019;Harries and Knorr, 2009;Metcalfe et al, 2011;Sogot et al, 2014;Song et al, 2011;Twitchett, 2007;Wiest et al, 2018). Species that survive mass extinctions are often unusually small and are termed "Lilliput taxa" (Urbanek, 1993), although the more general term "Lilliput Effect" is used to describe the prevalence of smaller species at this time.…”

Environmental control on shell size of Middle Triassic bivalve Plagiostoma

“…In case of sea regression, decreasing living space may lead to the disappearance of a species and even to its total extinction. Living organisms could therefore turn towards a decrease in average body size, in order to reduce their nutritional requirements and accommodate less space, both shortages supplying an advantage in the "arm race" for environmental resources (BORTHS & AUSICH, 2011;BROM et al, 2015b).…”

“…Change in body size of P. striatum, population dwindling and/or blanking in time of unfavorable environmental conditions point out the fourth type of Lilliput Effect (decrease in body size with LAZARUS gaps; BORTHS & AUSICH, 2011). Small-sized organisms have a relatively higher chance of survival in a less-stable environment due to their lower metabolic requirement and earlier onset of sexual maturity (BORTHS & AU-SICH, 2011;BROM et al, 2015b). Moreover, organisms from oligotrophic environments react in a similar way by decreasing their body size since the probability of finding food availability is relatively lower (BROM et al, 2015a).…”

“…These changes have a direct and/or indirect impact on living organisms, forcing them to adapt to changing environment (BENTON, 2009). One of the major reasons affecting body size in marine animals is the onset of anoxic events (OAEs), e.g., WADE and TWITCHETT (2009); BORTHS and AUSICH (2011); BROM et al (2015b). Several such events were recorded during the Mesozoic, though none of them were documented in the Middle Triassic (HALLAM, 1997).…”