Hi Brian,

I believe that the current consensus is that the common ancestor of bony fish and mammals probably resembled to Tiktaalik or the related species from middle-late devonian. AFAIK the first papers on this group where published in an issue of Nature in 2006:

Daeschler, Edward B., Neil H. Shubin, and Farish A. Jenkins. "A Devonian tetrapod-like fish and the evolution of the tetrapod body plan." Nature 440.7085 (2006): 757-763.

Shubin, Neil H., Edward B. Daeschler, and Farish A. Jenkins. "The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb." Nature 440.7085 (2006): 764-771.

Ahlberg, Per Erik, and Jennifer A. Clack. "Palaeontology: A firm step from water to land." Nature 440.7085 (2006): 747-749.

I have no real insights regarding sharks which common ancestrors with the fish/mammal lineage is somewhat older: around 460 million years.

Should you be (or any other reader of this post) interested in a more handy introduction to this question, I would suggest these two books:

Shubin, Neil. "Your inner fish: the amazing discovery of our 375-million-year-old ancestor." (2009). Penguin Books, London, UK.

Dawkins, R. "The Ancestor's Tale, A Pilgrimage to the Dawn of Evolution". 2004, Boston, MA: A Mariner Book.

Hope this helps,

Tito

Perhaps Zhu et al 1999 "A primitive fossil fish sheds light on the origin of bony fishes" from Nature? At least they discuss a 400 Myr fossil of the osteichthyan common ancestor... Otherwise, some of the articles citing this one may contain the information you seek (http://scholar.google.se/scholar?cites=11055936971078845820&as_sdt=2005&sciodt=0,5&hl=en)

Hi Joacim,

Zhu et al. paper is indeed a very interesting one. Among the papers citing it, I found this one particularly intersting (as a non-specialist in paleotology, just a fish ecologist interested in this issue):

Davis, S.P., Finarelli, J.A. & Coates, M.I. (2012) Acanthodes and shark-like conditions in the last common ancestor of modern gnathostomes. Nature, 486, 247–250.

But it somewhat puzzled me rather than clarifying things. I surely need to go deeper inside it.

Cheers,

Tito