NEOICHNOLOGY OF COSTA RICAN BATS: TRACK MORPHOLOGY AND TRACKMAKING ABILITY OF PHYLLOSTOMID AND EMBALLONURID BATS

Of the four groups of animals to have developed powered flight, only bats are unknown from the trace fossil record. In comparison, pterosaurs, flying quadrupeds like bats, are recognized from at least three valid ichnogenera that are known from every continent except Antarctica. With a body fossil record of over 52 million years combined with the rapid colonization of most continents, bats are ideal candidates to have produced trace fossils. Modern bats display a wide range of terrestrial abilities, from aerial insectivores, to those that forage for insects and other arthropods on the ground, to the New Zealand short-tailed bat and common vampire bat that possess a suite of terrestrial behaviors including running and hopping. We present the first broad survey of trackmaking ability in an ecologically diverse family of Neotropical bats, the Phyllostomidae, as well as representatives from another New World family, the Emballonuridae. In late June and early July 2014, trackmaking trials were conducted with members of the five Costa Rican subfamilies of Phyllostomidae: Carollia perspicillata and C. sowelli (Carollinae), Lonchorhina aurita and Micronycteris microtus (Phyllostominae), Demanura phaeotis and Artibeus lituratus (Stenodermatinae), Desmodus rotundus (Desmodontinae), and Hylonycteris underwoodi (Glossophaginae), and the emballonurid Saccopteryx bilineata. These bats represent different ecological niches and hindlimb morphologies resulting in differing terrestrial behaviors and track morphology. Most bats were limited to an uncoordinated terrestrial gait that we have termed the breaststrokelike crawl, while a few, notably Desmodus, proved terrestrially adept. Tracks produced corresponded primarily to the forelimbs, while hindlimb tracks were much less likely to be preserved. Various track morphologies produced include linear and arcuate tracks corresponding to digit one of the manus, and isolated and clustered pedal traces featuring four or five subparallel digit impressions. Only Desmodus produced definitive trackways. This research will better illuminate what bat tracks and trackways may look like in the rock record, and future research will address how trackways, such as those produced by Desmodus, compare to pterosaur trackways.