Gastropod evidence against the Early Triassic Lilliput effect

Abstract

Size reduction in the aftermath of the Permian-Triassic mass extinction event has repeatedly been described for various marine organisms, including gastropods (the Lilliput effect). A Smithian gastropod assemblage from Utah, USA, reveals numerous large-sized specimens of different genera as high as 70 mm, the largest ever reported from the Early Triassic. Other gastropods reported from Serbia and Italy are also as large as 35 mm. Size frequency distributions of the studied assemblages indicate that they were not unusually small when compared with later Mesozoic and modern faunas. The occurrence of large-sized gastropods less than 2 Ma after the Permian-Triassic mass extinction refutes the Lilliput hypothesis in this clade, at least for the last ~75% of the Early Triassic.

Gastropods from the Early/Middle Jurassic transition of Franconia (Southern Germany)

“…The small size of most of the gastropods from Mistelgau is not result of stunting or dwarfism. Most of the species are primarily small as is the case in the majority of modern snails (e.g., Brayard et al 2010).…”

Environmental and scale-dependent evolutionary trends in the body size of crustaceans

“…[14]), dwarfing ('Lilliput effect') following mass extinctions (e.g. [15,16]; but see [17]), changes in body size as a function of niche availability [18], long-term trends driven by climate change (e.g. [19]) and taxon-specific intrinsic constraints [20].…”

An Early Triassic (Dienerian) microgastropod assemblage from the Salt Range, Pakistan and its implication for gastropod recovery from the end-Permian mass extinction

“…The small size of these gastropods is no evidence for the Liliput Effect which proposes a generally small adult size after the extinction event (see e.g. Fraiser & Bottjer 2004;Fraiser et al 2005Fraiser et al , 2011Brayard et al 2010Brayard et al , 2011Brayard et al , 2015.…”