Produced by the Population Genetics and Evolution class, Furman University

The Devonian: Panderichthyes
Panderichthys were lobe-finned fish that are considered to be one of the important transitional links between fish and amphibians (Morton 1997). The first specimens were excavated from the Frasnian deposits in Latvia (Murphy 2005). There are two species, P. stolbovi and P. rhombolepis (Murphy 2005). While P. stolbovi is known through only a few snout pieces and an incomplete lower jaw, P. rhombolepis has a number of complete specimens (Murphy 2005). This fish ranged in size from 90-130 cm and is characterized as having a large tetrapod-like head (Wikipedia 2009). The head of Panderichthys was wide in the back and narrow toward the snout and had a pair of external nostrils and a choana (hole between the nasal passage and mouth), which is missing in the all other lobe-finned fish (Morton 1997). Panderichthys also possessed lungs as well as gills (Morton 1997), and lacked dorsal and anal fins (Morton 1997). While these traits, alone, suggest some relationship with terrestrial tetrapods, the most remarkable characters are the forelimbs. Panderichthys had pectoral fins that matched the tetrapod forelimb pattern of a humerus, ulna, and radius; and had a tibia and fibula in the the posterior fins (Morton 1997). The pelvic girdle also displays derived and ancestral traits, further supporting that Panderichthys was a transitional genus (Wikipedia 2009). Finally, Panderichthys possessed the incipient structure that may have evolved into an inner ear bone found in mammals (Carey 2006). The spiracle, a small hole located behind the eye which opens to the mouth, is wider than in other lobe-finned fish and the hyomandibular bone is much smaller (Carey 2006). This enlarged spiracle may have formed the ear of land vertebrates. The hyomandibular bone evolved into part of the reptilian jaw, and then into the stirrup in the inner ear of mammals (Carey 2006).

Page by Chapin Hardy
Panderichthys. Photo credit: Vokrugsveta

Carey B. 2006. Human Ears Evolved from Ancient Fish Gills. LiveScience. Accessed February 22, 2010.

Morton GR. 1997. Fish to Amphibian Transition. California State University at Fullerton. Accessed February 22, 2010.

Murphy DC. 2005. Panderichthys spp. Devonian Times. Accessed February 22, 2010.

Wikipedia. 2009. Panderichthys. Accessed February 22, 2010.