Rise of the Earliest Tetrapods: An Early Devonian Origin from Marine Environment

Abstract

Tetrapod fossil tracks are known from the Middle Devonian (Eifelian at ca. 397 million years ago - MYA), and their earliest bony remains from the Upper Devonian (Frasnian at 375–385 MYA). Tetrapods are now generally considered to have colonized land during the Carboniferous (i.e., after 359 MYA), which is considered to be one of the major events in the history of life. Our analysis on tetrapod evolution was performed using molecular data consisting of 13 proteins from 17 species and different paleontological data. The analysis on the molecular data was performed with the program TreeSAAP and the results were analyzed to see if they had implications on the paleontological data collected. The results have shown that tetrapods evolved from marine environments during times of higher oxygen levels. The change in environmental conditions played a major role in their evolution. According to our analysis this evolution occurred at about 397–416 MYA during the Early Devonian unlike previously thought. This idea is supported by various environmental factors such as sea levels and oxygen rate, and biotic factors such as biodiversity of arthropods and coral reefs. The molecular data also strongly supports lungfish as tetrapod's closest living relative.

First Articulated Phyllolepid Placoderm from North America, with Comments on Phyllolepid Systematics

“…A new chronology for tetrapod origins has been suggested based on the recent discoveries of putative tetrapod tracks and trackways in the basal Middle Devonian (Eifelian) of Poland (Niedźwiedzki et al, 2010). This chronology is further supported by recent analyses using molecular data from 13 proteins sequenced from 17 species to calculate divergence times (George and Blieck, 2011), and from statistical methods looking at predicted nodes for tetrapod divergence (Friedman and Brazeau, 2011). Both studies suggest an estimated Early Devonian time of origin for tetrapods.…”

Evolutionary processes involved in the diversification of chelonian and mammal polystomatid parasites (Platyhelminthes, Monogenea, Polystomatidae) revealed by palaeoecology of their hosts

“…1), we may argue that polystomes evolved from fish parasites that colonized terrestrial hosts during the ecological transition of vertebrates close to lungfish (Brinkmann et al, 2004;George and Blieck, 2011), in the Late Devonian (Carroll, 2001), or even earlier in the early Middle Devonian (Niedź wiedzki et al, 2010). Although polystomes of amphibians do not constitute a monophyletic group, i.e.…”

Annotation of the Nuclear Receptors in an Estuarine Fish species, Fundulus heteroclitus

“…However, recent phylogenetic data, examination of Saurapsid genomes such as reptiles and birds (76) and the lobe-finned fish Coelocanth indicates that CAR was lost in teleosts and PXR was lost in reptiles and birds (77). Therefore, it is thought that the lobe-finned fish that arose 400 million years ago during the Devonian period and are the ancestors of all tetrapods, contained CAR and PXR (78,79). …”