New material supports a description and taxonomic revision of Holoptychius ? radiatus (Sarcopterygii, Tristichopteridae) from the Upper Devonian Catskill Formation in Pennsylvania, USA

ABSTRACT. New material from the Upper Devonian (Famennian) Catskill Formation of Pennsylvania, USA, reveals anatomical details previously lacking from the enigmatic fossil species that Newberry (1889, U.S. Geological Survey Monograph 16:1–228) named Holoptychius ? radiatus. The original material (scales and lepidotrichia) was attributed to Holoptychius (Sarcopterygii, Porolepiformes) according to the ridged ornament on the exposed portion of the scales. Scale and cranial anatomy revealed by the new material supports a reassignment of the species to Langlieria (Sarcopterygii, Tristichopteridae). The emended diagnosis of the new combination includes the grooved scale ornament that was noted, though described differently by Newberry, and a posterior oblique pitline groove of the parietal that extends to the caudal margin of the element. Along with Hyneria lindae and Eusthenodon sp. indet., there are now at least three known species of Tristichopteridae from the Catskill Formation. Temporal/spatial separation of these species, along with supporting anatomical characteristics, suggests that tristichopterids commonly filled the ecological niche of top predator in the Famennian-age nonmarine ecosystems of the Catskill Delta Complex. The presence of a Langlieria species in the Catskill Formation lends further support to a biogeographic connection between Pennsylvania, USA, and Belgium during the Famennian Stage of the Upper Devonian.