An experimental analysis to evaluate walking gaits in extinct South American ungulates

KRAPOVICKAS, VERÓNICA; VERA, ROCÍO BELÉN; FERNÁNDEZ PIANA, LUCAS; FARINA, MARTÍN EZEQUIEL; MARSICANO, CLAUDIA ALICIA; DE LA COLINA, ALICIA; KOELEWIJN, ANNE

Edimburgo

Congreso; SEB CENTENARY CONFERENCE 2023; 2023

Macraucheniids, robust quadrupedal ungulates with elongated necks and long limbs with threetoedautopodia, are the more diverse and frequently found group in Neogene successions insouthern South America. Their body plan is commonly compared to modern camelids. It has alsobeen proposed they used symmetric walking gaits, similar to modern camelids. Exceptionalmacraucheniid trackways were found in Neogene successions in Argentina, and can therefore beused as direct evidence for macraucheniid gaits. To evaluate the macraucheniid trackways andtheir putative gait, we used guanacos (Lama guanacoe) as the ungulate alive with the most similarbody plan, because macraucheniids have no living representatives´descendants. Eight femaleguanacos were trained to walk over a humid fine-grained sandy substrate at Temaikén Biopark(Buenos Aires, Argentina). Once a week from August to November 2021 (10 times), we filmed theirgait in slow motion using a lateral and a dorsal camera, while we also recorded their trackways viaphotogrammetry. We recorded 44 laps that were suitable and classified these as walking ortrotting. We compared trackway patterns of guanacos and macraucheniids visually using a newlyproposed methodology based on linear transformations and numerically using the mean andvariance of the distances between two consecutive foot impressions. We found that the mean andvariance of symmetric walking gaits are smaller than those of trotting and that macraucheniidsfootprint patterns are nested within the guanaco´s symmetric walking gaits, which further supportsthat macraucheniids walked symmetrically.