Hederella carbonaria Condra & Elias, 1944 from the Roadian (middle Permian) of Mexico

Permian sclerobionts of brachiopods present in outcrops of clayey or silty limestones of the Paso Hondo Formation, in southern Mexico, include representatives of the enigmatic group Hederelloidea. This group, with uncertain affinities, has in the past generally been considered to be related to the Phylum Bryozoa but which, given its prismatic ultrastructure and larger size, is currently considered as an independent group of lophophorates. As with most sclerobiont faunas, the fossil record of hederelloids is abundant from the Silurian to Devonian, but they are very scarce in the Upper Paleozoic where they are restricted to subtropical paleolatitudes of moderate depth, calcareous shale or clay limestone facies. In particular, the genus Hederella has only been reported from the Carboniferous of North America and the United Kingdom and from the Permian (Sakmarian) of Siberia. The presence of hederelloids in the Paso Hondo Formation, which crops out in the State of Chiapas, on the border of Mexico and Guatemala, constitutes the first record of this group for Mexico, the youngest at a global level, and extends the temporal distribution of the Order Hederelloidea to the Roadian. The hederelloids present in the Paso Hondo Formation are attached to shells of rhynchonellid and athyridid brachiopods and associated with other sclerobionts, such as bryozoans of the orders Trepostomata and Cystoporata.