Panderichthys

Panderichthys is a genus of extinct sarcopterygian (lobe-finned fish). It lived in the late Devonian period, about 380 mya. Possible tetrapod tracks dating back to before the appearance of Panderichthys in the fossil record were found. This suggests that Panderichthys is not a direct ancestor of tetrapods. It shows the traits which evolved during the fish-tetrapod evolution. Niedzwiedzki, G., Szrek, P., Narkiewicz, K., Narkiewicz, M and Ahlberg, P., Nature 463(7227):43–48, 2010, Tetrapod trackways from the early Middle Devonian period of Poland, 7 January 2010.Clack, Jennifer A. "Devonian climate change, breathing, and the origin of the tetrapod stem group." Integrative and Comparative Biology 47.4 (2007): 510-523. 

Decreased oxygen in the atmosphere would have caused the oxygen concentrations in water to decrease. This  would have caused any aquatic animal which could breathe air to have an advantage, and be more likely to thrive.  

In addition to its ability to swim in water, Panderichthys could also breathe air. Its strong pectoral fins might allow it to prop up its head in shallow water and take a breath.

 Description 
Panderichthys is a 1.5–2 m (4 ft 11 in6 ft 7 in) long fish with a large tetrapod-like head that is flattened, narrow at the snout and wide in the back. 

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. 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". 

 The humerus 
One of the features of Panderichthys is its humerus. Due to a complex process, early tetrapods have an L-shaped humerus. Another unique feature is that the humeral ridge doesn't go into the entepicondyle.

 Respiration 
Panderichthys could breathe air. The opercular series in Panderichthys was shorter than in other species of osteolepiforms.

 Gallery 

 References 

 Other websites 

 https://www.nature.com/articles/nature07339

Category:Lobe-finned fish
Category:Extinct fish
Category:Devonian