Late Pennsylvanian fish assemblage from the Robledo Mountains and new records of Paleozoic chondrichthyans in New Mexico, USA

Abstract

at several localities across New Mexico, USA (Zidek & Kietzke 1993; Lucas & Estep 2000; Ivanov et al. 2009; Lucas et al. 2011; Hodnett & Lucas 2015, 2017; Itano & Lucas 2018). But, despite extensive field study, extremely diverse assemblages of fossil fishes with numerous isolated microand rare macroremains have proven to be elusive. This has been changed by the discovery of fish fossils in a conglomerate bed (so called “shark bed”) of the Horquilla Formation in the Robledo Mountains of Doña Ana County, southern New Mexico, USA (Fig. 1). The chondrichthyan remains here described from this bed are isolated teeth of bransonelliforms, symmoriiforms, a ctenacanthiform, a jalodontid, a euselachian, indetermi n ate protacrodontid and hybodontiform, anachronistid neoselachians, an orodontiform, a helodontiform, a euge neo dontiform, indeterminate petalodontiform, psepho dontid and euchondrocephalian; as well as the buccopharyngeal denticles of symmoriiforms; and scales of various types. Rare acanthodian scales, and several actino pterygian teeth and scales also occur in this assemblage. Besides the diverse fish assemblage from the Horquilla Formation of the Robledo Mountains, some new records of Paleozoic chondrichthyans in New Mexico that were not included in recent reviews (Hodnett & Lucas 2015, 2017) are also documented here. These new occurrences increase the taxonomic diversity in the fish assemblages, and represent some taxa that are recorded in New Mexico for the first time: the fin spine of Ctenacanthus in the Upper Devonian and the teeth of Bransonella and Sphena­ canthus in the Middle Pennsylvanian.