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Craniofacial Allometry is a Rule in Evolutionary Radiations of Placentals

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It has been suggested that larger species of mammals tend to become long-faced when they diverge in size during an evolutionary radiation. However, whether this allometric pattern, reminiscent of ontogenetic changes in skull proportions, is indeed a rule has yet to be thoroughly tested. Using ~ 6000 adult specimens from 14 phylogenetically well separated and ecomorphologically distinctive lineages, 11 orders, and all superorders of the placentals, I tested each group for positive craniofacial allometry (CREA). The evidence supporting CREA is overwhelming, with virtually all analyses showing proportionally longer faces in bigger species. This corroborates previous studies in other groups, consolidates CREA as a pervasive morphological trend in placental evolution and opens important research avenues for connecting micro- and macro-evolution. If found in even more lineages of non-placental mammals, confirmed in birds, and possibly discovered in other tetrapods, CREA could become one of the most general rules of morphological evolution in land vertebrates.

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New data, which are published for the first time in this paper, were collected at Museo Civico di Storia Naturale di Milano, Natural History Museum Vienna, National Museum Prague, Museum für Naturkunde, Museum National d’Histoire Naturelle, Hungarian Natural History Museum, Naturhistoriskariksmuseet. I owe a huge thank to all curators, collection managers and staff, including the SYNTHESYS administrators, whose help and support was fundamental. I am also deeply grateful to a number of colleagues who provided technical help and advice. With anticipated apologies for certainly forgetting to explicitly mention several of the many people whom I am in debt with, as well as for listing names in quasi-random order, I would like to thank a lot: Wim Wendelin, Emmanuel Gilissen, Giorgio Bardelli, Görföl Tamás, Gabor Csorba, Virginie Bouetel, Aurelie Verguin, Frank Zachos, Alex Bibl, Krapf Andrea, Petr Benda, Karel Kaderàbek, František Vacek, Manja Voss, Christiane Funk, Detlef Willborn, Mayer Frieder, Daniela Kaltoff, Irene Bisang, Emily Dock Åkerman, Jessica Joganic, Aurélie Siberchicot, David Katz, Mike Collyer, David Warton, Sara Taskinen, Paul O’Higgins, Sarah Elton, David Polly, Krish Seetah, Dan Franklin, Carlo Meloro, Diego Fontaneto and Alessandro Minelli. A special thank also to the greatly missed Colin Groves, for his fundamental contribution to interpreting the preliminary analyses of wild asses, and to Anderson Feijó, who helped with species identification of some of the armadillos. My gratitude goes also to the American Society of Mammalogists, for inviting me to present the preliminary results of this study at their annual conference and for covering all the costs of my trip to the US. This paper is dedicated to the memory of Mario Zambarbieri and Paolo Tongiorgi, my greatest mentors and friends, as well as to that of Colin Groves, a most extraordinary mammalogist, and of Leonard Radinsky, first discoverer of CREA, whose important role I would have acknowledged well before, had I found earlier his surprisingly little cited and yet fundamental contribution on patterns in mammalian morphological evolution. Finally, I am greatly in debt to Julien Claude, an anonymous reviewer and the Editor-in-Chief Benedikt Hallgrimsson, for their most helpful review and appreciation of my work.


Data collection was funded by SYTHESYS (BE-TAF-2861, SE-TAF-4409, AT-TAF-4816, CZ-TAF-4817, HU-TAF-4818, DE-TAF-4819, FR-TAF-4820) for all lineages except most primates, that were measured for a previous project with Sarah Elton, funded by the Leverhulme Trust (F/00128/T).

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This study was designed, all data were collected, analyses done, and the paper written by CA.

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Correspondence to Cardini Andrea.

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Andrea, C. Craniofacial Allometry is a Rule in Evolutionary Radiations of Placentals. Evol Biol 46, 239–248 (2019).

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