COMPLEX EVOLUTION IN ALVAREZSAURIDAE: MINIATURIZATION, GIGANTISM AND ELEVATED MORPHOLOGICAL RATE EVOLUTION AND THEIR CAUSES AND IMPLICATIONS

JORGE GUSTAVO MESO; DIEGO POL; LUIS MARÍA CHIAPPE; ZICHUAN QIN; IGNACIO DIAZ-MARTINEZ; FEDERICO GIANECHINI; SEBASTIAN APESTEGUÍA; PETER MAKOVICKY; MICHAEL PITTMAN

Cladistics

Wiley Online Library

Año: 2024

Some of the smallest examples of dinosaurian body size are from alvarezsaurians, an enigmatic group of maniraptoran coelurosaurs with a peculiar combination of anatomical features unique among theropods. Despite the large number of alvarezsaurian species described and the increased anatomical understanding this has provided, their body size macroevolution has received little attention. Here we reconstruct and analyze directional trends of alvarezsaurian body size evolution through an integrated analysis of body mass, ontogenetic age and morphological rate data enabled by a comprehensively revised phylogenetic analysis. Our analyses identify 4 periods of high morphological rate evolution in the Bathonian-Callovian, Hauterivian-early Berriasian, early Cenomanian, and late Cenomanian-Turonian. Crucially, for the first time, we link this evolution to the key effects of animal miniaturization including morphological novelty, structural reduction and simplification, elevated homoplasy and behavioral changes, providing a holistic example of miniaturization in a Mesozoic vertebrate group that provides a framework for more detailed studies of body size evolution in disparate animal groups.