New Mexico Geological Society Annual Spring Meeting — Abstracts

We document a new occurrence of Walpia White, 1929, an invertebrate ichnogenus that has not previously been reported from New Mexico. The specimen (New Mexico Museum of Natural History, NMMNH P-63036) is from NMMNH locality 8278, which is in the upper part of the Early Permian (Wolfcampian) Abo Formation (Cañon de Espinoso Member) of the Cerros de Amado area in Socorro County. NMMNH P-63036 consists of several horizontal burrows preserved in positive epirelief on a slab of reddish-brown, very fine grained sandstone. The burrows display raised nodular margins and an open medial depression. The medial depression is irregularly filled by nodules in some few places along the burrow courses. The nodules are smooth, rounded, 1-3 mm across, and identical in composition to the surrounding matrix. The burrows are 1-2 mm below the bedding surface, and burrow widths are typically about 10 mm. The burrow courses are mostly straight with gentle curves, and maximum burrow length is 19 cm. Branching and intersecting of burrows are seen. The upper surface of the specimen slab shows, in addition to the burrows, incipient desiccation cracks and small, subhorizontal root traces.

The Abo Formation material differs from the Walpia type material of the Early Permian Hermit Shale of the Grand Canyon, Arizona, by displaying a medial depression. We therefore provisionally assign the burrows to Walpia cf. W. hermitensis pending further study. Walpia is a monospecific, poorly known, and rarely reported ichnotaxon that is probably the shallow foraging burrow of an early beetle. There is a range of morphological variation within Walpia , such as the medial depression seen in the Abo Formation burrows, which was not recognized in the original diagnosis. It is therefore important to document any new records of Walpia.