Discriminant analysis morphospace plot comparing Limiavipedidae (<i>Wupus</i> and <i>Limiavipes</i>) to prints of small- and medium-sized theropods and large wading birds.

<p>Discriminant analysis scatterplot comparing log₁₀-transformed and mean removed linear data (footprint length, FL; footprint width, FW; digit II length, DLII; digit IV length, DLIV; pace length, PL; stride length, SL) and mean removed angular data (total divarication, DIVTOT; pace angulation, PA) of Limiavipedidae (<i>Wupus agilis</i>, dark blue; <i>Limiavipes curriei</i>, dark brown) to ichnotaxa of Cretaceous theropods (black), Mesozoic avians (green), Cenozoic avians (pink), and traces of extant avians (orange). The scatterplot shows that Limiavipedidae, as well as the Cenozoic avian ichnotaxa and ichnites from extant avians, do not share morphospace with Cretaceous theropod tracks. Axis 1 is interpreted as the size–total divarication axis; as size and pace angulation increase (as the size of the trackmaker increases and as the trackway narrows), total divarication decreases. This is consistent with the observations of theropods having a smaller total divarication, as well as a larger size and narrower trackway. Theropods group positively along Axis 1, while birds, with their smaller size and higher total divarication, and more “toed-in” footprints, group negatively along Axis 1. Axis 2 is interpreted as the relationship between FW and the lengths of the lateral digits to FL, PL, and SL; footprints with longer lateral digits (DII, DIV) are relatively shorter in length, and are found in trackways with shorter PL and SL. Avian prints are interpreted to have subequal lateral digits and a higher L/W ratio, and the discriminant analysis correlates with the interpretation that avian prints belong to trackways with a relatively shorter pace length (Tables <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124039#pone.0124039.t004" target="_blank">4</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0124039#pone.0124039.t005" target="_blank">5</a>).