Bluefieldius, a tiny Mississippian cheirolepid, enters the LRT

Mickle 2018 described an exquisite, tiny,
Upper Mississippian fish from West Virginia. Bluefieldius mercerensis (Mickle 2018, Late Mississippian, KUVP 155843;  Figs. 1, 2) was originally described without a phylogenetic analysis.

Figure 1. Bluefieldius in situ from Mickle 2018 shown many times larger than life size.

Figure 1. Bluefieldius in situ from Mickle 2018 shown many times larger than life size.

From the abstract
“The description of this new taxon represents the first actinopterygian and the first vertebrate body fossil described from the Bluefield Formation and the second actinopterygian taxon described from the Mauch Chunk Group in West Virginia.”

Figure 2. The skull in situ and diagram of Bluefieldius from Mickle 2018, Colors added here to match tetrapod homologs.

Figure 2. The skull in situ and diagram of Bluefieldius from Mickle 2018, Colors added here to match tetrapod homologs.

Mickle 2018 reports,
B. mercerensis n. gen. n. sp. differs from other Carboniferous fishes in specific cranial characteristics. Lower actinopterygian fishes are characterized by a great deal of anatomic and taxonomic diversity that is not well understood. We have neither a stable classification scheme nor strongly supported hypotheses of relationships for lower actinopterygian fishes.”

That was true back then in 2018. Now that the LRT includes a wide gamut of fish taxa the LRT provides that stable classification scheme.

Figure 5. The genus Cheirolepis by Pearson and Westoll 1979 (line drawing) compared to DGS skull tracing. Evidently these were two different specimens based on scale alone.

Figure 3. The genus Cheirolepis by Pearson and Westoll 1979 (line drawing) compared to DGS skull tracing. Evidently these were two different specimens based on scale alone.

Mickle did not perform a phylogenetic analysis,
but preferred to list traits that marked this taxon. As you know, this is called, “Pulling a Larry Martin,” Some traits were mismarked by Mickle 2018 (Fig. 2) relative to traits traced here based on tetrapod homologs.

Figure x. Subset of the LRT focusing on fish.

Figure x. Subset of the LRT focusing on fish.

Here
in the large reptile tree (LRT, 1742+ taxa, Fig. x) Bluefieldius nests basal to the Cheirolepis (Fig. 3) clade.


References
Mickle KE 2018. A new lower actinopterygian fish from the Upper Mississippian Bluefield Formation of West Virginia, USA. PeerJ 6:e5533; DOI 10.7717/peerj.5533

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