the size of the spiracular chamber and its opening to the outside. Compared to Eusthenopteron, the spiracular chamber of Panderichthys is greatly expanded and the hyomandibula is shorter compared to those in fish. The opercular series was also shorter compared to other osteolepiforms. Panderichthys also has a single external nasal opening and a palatal choana. In contrast to earlier osteolepiforms, the palatal choana is elongated and the nariochoanal lamina is narrow. Along with the spiracular chamber, this feature in Panderichthys can be considered transitional during the evolution from fish to tetrapods. Sarcopterygians such as Panderichthys can be considered at least facultative air breathers and demonstrate an intermediate form as air breathing was becoming more abundant. Classification In January 2010, Nature reported well-preserved and "securely dated" tetrapod tracks from Polish marine tidal flat sediments approximately 397 million years old. These fossil tracks suggest that a group of two meter long tetrapods lived in the fully marine intertidal or lagoonal areas on the south coast of Laurussia during the time elpistostegids were living. This implies that Panderichthys is not a transitional fossil and represents its own adaptive morphology. Therefore, Panderichthys can only be a "late-surviving relic", showing traits that evolved during the transition from fish-like creatures to tetrapods, but whose date does not reflect that transition. The tracks "force a radical reassessment of the timing, ecology and environmental setting of the fish–tetrapod transition, as well as the completeness of the body fossil record." Palaeoecology Panderichthys was alive during the late Devonian (Frasnian) in Lode, Latvia. Lode is known to be a marginal marine environment and it has been hypothesized that Panderichthys was adapted for movement in shallow and debris filled waters. Panderichthys was collected in deposits that were formerly believed to be from a calm freshwater basin, but have proven to be from shallow tidal flats or an estuary. The Lode Formation, where P. rhombolepis was found, occurs within a 200-meter thick layer composed of fine grained sandstone and clay along with finely dispersed clays. Nearly every major taxa of late Devonian vertebrates are represented within the Lode Formation. Most of the specimens are well preserved due to anaerobic substrate conditions as well as rapid burial in depressions on the submarine delta slopes. P. rhombolepis was discovered in the Gauja Regional formation within the lower Frasnian section. Taphocoenosis was characterized as in finely displaced clay and silty clay as well as low