New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico Museum of Natural History locality 4667 in the Upper Pennsylvanian (Missourian) strata of the Atrasado Formation of Socorro County contains a 4-m thick unit of thinlylaminated, dark gray shale that produces a moderately diverse fossil fish assemblage of acanthodians, actinopterygians and sarcopterygians. The material primarily consists of small groups of scales and isolated bones and teeth, which probably came from carcasses that decomposed while drifting in the water column. The most abundant elements are of palaeonisciforms, which are represented by flank and fulcral scales, skull bones of Elonichthyidae, Haplolepidae and a deep-bodied form (cf. Platysomidae). One well-preserved fragment consists of a palaeonisciform caudal fin with squamation and fin rays. Less common remains include osteolepiform scales resembling Megalichthyes or Greiserolepis; rhizodontiform scales, teeth and a cleithrum probably assignable to Strepsodus; as well as rare acanthodian fin spines and a scapula belonging to Acanthodes. Abundant ovoid coprolites and less common spiral coprolites and flat ground masses of probable fish origin occur with the fish remains. Other trace fossils are absent, which is likely due to anoxic bottom conditions during deposition. Terrestrial plants, syncarid crustaceans, insect wings, conchostracans, ostracods, a non-marine bivalve (Anthraconauta) and a single specimen of the problematic marine invertebrate Sphenothallus occur in the same unit as the fish remains. Deposition of this unit as indicated by the sediments, fauna and flora took place within a fresh to minimally brackish lacustrine setting with access to shallow marine conditions. The fish fauna at locality 4667 is similar to that reported from other Carboniferous lacustrine environments. This occurrence adds to the record of Paleozoic fishes from New Mexico, which is best known from the early Virgilian Kinney Quarry Lagerstätte.