THE FIRST OCCURRENCE OF A LEPOSPONDYL AMPHIBIAN IN THE PENNSYLVANIAN CONCRETIONS OF KNOB NOSTER, MISSOURI

The concretions found at Knob Noster in Johnson County, Missouri contain a diverse assemblage of terrestrial and brackish water flora and fauna from the Upper Carboniferous in a manner that is similar in both preservation and composition to the Braidwood fauna of the famed Mazon Creek lagerstӓtte of Illinois. Since the discovery of the site around 1990, a significant assemblage of invertebrates including myriapods, brachiopods, insects and crustaceans has been described. Vertebrate finds have included scales and egg cases belonging to a variety of osteichthyes and the chondrichthyan egg case, Palaeoxyris. There has not been a documented occurrence of a tetrapod within the Knob Noster faunal assemblage. Described herein are the first tetrapod remains discovered at Knob Noster. Persevered within a small concretion little more than five centimeters across are two articulated groups of vertebrae constituting the partial vertebral column of a limbless amphibian. Six articulated trunk vertebrae are present positioned adjacent to five articulated caudal vertebrae. The slender, lepospondylous vertebrae are indicative of an animal belonging to the Aϊstopoda, in this case with affinities to the genus Oestocephalus (Cope 1868). The discovery of a tetrapod at Knob Noster offers new implications for the paleobiology of the locality and opens up the possibly of finding more tetrapod remains.