NEW RECORDS OF THE INVERTEBRATE ICHNOFOSSILS ROBLEDOICHNUS AND TONGANOXICHNUS FROM THE LOWER PERMIAN OF NEW MEXICO

Abstract

Tonganoxichnus robledoensis and Robledoichnus lucasi are ichnotaxa that have previously been reported only from single occurrences in Lower Permian strata of southern New Mexico. Here we record the first occurrence of these ichnotaxa outside of their type localities within the Robledo Mountains Formation, thus augmenting their distribution. Single specimens of each ichnotaxon occur in association on a slab that was collected from New Mexico Museum of Natural History (NMMNH) locality 5383 in the lower part of the Abo Formation in the Red Gap area of the Fra Cristobal Mountains in Sierra County, New Mexico. The specimens are from a 0.7-meter thick unit of thinly bedded, ripplelaminated sandstone. A low diversity tetrapod ichnofauna that is dominated by Batrachichnus occurs at this site. Several specimens of the invertebrate burrow Taenidium have also been found. The paleoenvironment was a fluvial sandflat on a coastal floodplain. symmetrical trace anterior, posterior, and terminal that ichnospecies. Lateral the Robledo Mountains Formation type the mid-line. two types within T. , variations in jumping behavior. three pairs of lateral imprints that anteriorly directed. Fra three pairs of lateral imprints in anterior imprints anteriorly directed, the medial imprints laterally directed, the posterior imprints are posteriorly directed. orientation similarly in T. , resting trace the Upper Carboniferous Two track rows of walking imprints are shown that contain a twoimprint arrangement comparable to the type specimen from the Shalem Colony section of the Robledo Mountains Formation. A separate landing trace is not preserved. The trackway is 7 cm long and 1 cm in external width. It is separated from P-40869 by a distance of 7 cm. The external width of the trackway coincides with the distal width of the leg appendage imprints seen on the associated T. robledoensis . Kozur and Lemone thought that the producer of R. lucasi flying insect. We propose R. lucasi produced by an apterygote monuran, the same Tonganoxichnus