The nomenclature of skull bones in primitive lungfish

Campbell, Barwick and Pridmore 1995
labeled the many small bones of the lungfish skull in response to perceived nomenclature issues.

Unfortunately,
the authors continued the traditional practice of labeling the skull bones with letters and numbers (Fig. 1), thereby ignoring homologies with other vertebrates in which the skull bones have traditional names, like maxilla, frontal, etc.

Their abstract:
“An attempt is made to examine the problem of the nomenclature of the roofing bones in the most primitive dipnoans, which is still a matter of contention. The letter and number system that has been in use for the last half century was based on Dipterus, a Middle Devonian genus that has a reduced number of bones and a greatly shortened cheek in comparison with the Early Devonian Dipnorhynchus. Several attempts have been made to expand the Dipterus nomenclature to accommodate the more primitive condition in Dipnorhynchus and Uranolophus, but none has yet been generally accepted. The most recent attempt by Westoll (1989), which involves errors of reconstruction and interpretation, is discussed in this paper. The matter is of importance because assessment of the relationships of primitive dipnoans to other groups depends to a substantial extent upon these homologies.”

Figure 1. The Middle Devonian lungfish, Howidipterus, with subdivided skull bones colorized here to match those in the placoderm Entelognathus (Fig. 2).

Figure 1. The Middle Devonian lungfish, Howidipterus, with subdivided skull bones colorized here to match those in the placoderm Entelognathus (Fig. 2).

Schultze 2008 responded by
homologizing the skull bones of actinoperygians with those of sarcopterygians (as I just found out… learning as I go.) Not sure what the latest practice is.

Figure 4. Subset of the LRT updated with new basal vertebrates.

Figure 4. Subset of the LRT updated with new basal vertebrates.

We’ve already seen the breakup of skull bones in lungfish
into many little bones. These need to be homologized with those of other vertebrates, as shown at ReptileEvolution.com and at this prior blogpost. The way to do this is by way of phylogenetic bracketing.


References
Campbell KSW, Barwick RE and Pridmore PA 1995. On the nomenclature of the roofing and cheekbones in primitive dipnoans. Journal of Vertebrate Paleontology 15(1):28–36.
Schultze H-P 2008 (2007). Nomenclature and homologization of cranial bones in actinopterygians. Nomenclature and homologization of cranial bones in actinopterygians. In Mesozoic Fishes 4 – Homology and Phylogeny. Editors: Arratia G, Schultze H-P and MVH Wilson, Verlag Dr. F. Pfeil.

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