TY - JOUR AU - Piñeiro, Graciela Helena AU - Marchetti, Lorenzo AU - Marmol, Sebastián AU - Celio, Antonella AU - Xavier, Pedro Luis AU - Francia, Martin AU - Schultz, Cesar Leandro PY - 2022/05/27 Y2 - 2024/03/28 TI - Enigmatic wood and first evidence of tetrapods in the Yaguarí Formation (Middle-Late Permian), Uruguay JF - Agrociencia Uruguay JA - Agrocienc Urug VL - 26 IS - NE1 SE - DO - 10.31285/AGRO.26.504 UR - https://agrocienciauruguay.uy/index.php/agrociencia/article/view/504 SP - e504 AB - <p>This article describes an intriguing fossil material recently found in the fine-grained sandstone levels from the upper section of the Yaguarí Formation of Uruguay. The nature of this specimen and its relationships were, initially, not easy to determine with confidence although it was subjected to several analyses, such as morphological and comparative examination complemented with preparation of thin sections and microanatomical and chemical studies under SEM. However, the anatomical structure shown in the performed transversal thin sections allowed solving the issue on the different animal or plant interpretations of the fossil specimen, which was finally discerned in favor of the latter. Therefore, after a detailed comparative study of the thin sections, we concluded that the specimen is a wood fragment related to the <em>Dadoxylon-Araucarioxylon</em> complex. Moreover, in order to provide a better biostratigraphic calibration for these deposits until now devoid of fossils, we include a preliminary description of recently found fossil footprints, which represent the first evidence of the presence of tetrapods in levels of the Yaguarí Formation (<em>sensu</em> Elizalde <em>et al.</em>, 1970), below the conglomerates that have yielded the Colonia Orozco Fauna. The footprints were preliminary assigned to the ichnotaxa cf. <em>Karoopes </em>isp, cf. <em>Capitosauroides </em>isp., and cf<em>. Pachypes </em>isp<em>.</em>, suggesting the presence of gorgonopsids and therocephalian therapsids and pareiasauromorphs, respectively. The Middle-Late Permian age recently suggested for the Yaguarí Formation based on paleomagnetic and radioisotopic studies is here supported by the described fossils, which thus constitute preliminary but nonetheless relevant discoveries for deposits whose fossiliferous potential has yet to be explored.</p> ER -