The Origin and Relationships of Early Chondrichthyans sensu Grogan et al. 2004

Grogan, Lund and Greenfest-Allen 2004
presented their hypothesis for the genesis of Chondrichthyes, the traditional clade of cartilaginous fish. In the large reptile tree (LRT, 2018+ taxa), ‘Chondrichthyes’ is either a paraphyletic grade, or it includes all descendants: bony fish, tetrapods and humans (Fig. 1) if monophyletic.

Both papers cherry-picked outgroup taxa.
Grogan, Lund and Greenfest-Allen 2004 wrote, “A zero-based hypothetical taxon, one acanthodian, one placoderm, and three osteichthyans serve as outgroups.”

Longtime readers know better than to do this.
Cherry-picking outgroup taxa is bad science. These authors thought they knew the correct outgroups. Turns out they did not. Do this instead: Include so many basal taxa that you can let your software tell you what the outgroup taxa are. Don’t cherry-pick. The LRT has outgroup taxa going back to Ediacaran worms.

These papers
listed several taxa that were not in the LRT, but were recently added, all without shifting the tree topology. More taxa are the key to understanding vertebrate interrelationships. What they teach in university level vertebrate paleontology textbooks is not up-to-date.

References
Grogran ED, Lund R and Greenfest-Allen E 2004. The origin and relationships of early chondrichthyans. Chapter 1 in Biology of Sharks and Their Relatives 2nd Ed. 2012 Carrier JC, Musick JA and Heithaus MB editors.
Lund R, Grogan ED and Fath M 2014. On the relationships of the Petalodontiformes (Chondrichtheys). Paleontological Journal 48(9):1015–1029.