Devonian Cheirolepis has a living deep water sister

The traditional ancestor of all ray-fin fish,
Cheirolepis (Fig. 1), is no longer alone in its family and order.

Figure 1a. Cheirolepis fossils.

Figure 1a. Cheirolepis fossils.

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 1b. 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.

According to Wikipedia
“Cheirolepis (‘hand fin’) is an extinct genus of ray-finned fish that lived in the Devonian period of Europe and North America. It is the only genus yet known within the family Cheirolepidae and the order Cheirolepiformes. It was among the most basal of the Devonian actinopterygians and is considered the first to possess the “standard” dermal cranial bones seen in later actinopterygians.”

Actually,
the Late Silurian basal placoderm Entelognathus, and its extant catfish sister, Clarias, have the ‘standard’ dermal cranial bones see in actinopterygians and tetrapods…

…but let’s get back to our headline.

Figure 3. Malacosteus niger in lateral view.

Figure 3. Malacosteus niger in lateral view.

Now an overlooked deep water cheirolepid, the stoplight loosejaw,
Malacosteus (Fig. 2; 25cm; Ayres 1848), nests with Cheirolepis in the large reptile tree (LRT, 1521 taxa). Malacosteus is considered a dragonfish and a variety of living dragonfish are known.

Figure 5. Malacosteus skull with colors added.

Figure 5. Malacosteus skull with colors added. This is a sister to Cheirolepis.

According to Kenaley 2007
“This genus is diagnosed within the Stomiidae by having enormous jaws, a single circular nostril on each side of the snout, a large tear-shaped accessory orbital photophore, serial photophores reduced in size and number, and intramandibular membrane, hyoid barbel, and palatine teeth absent.”

Notably,
the accessory orbital photophore (bright green) replaces a missing ventral jugal.

Figure 3. Subset of the LRT focusing on bony ray fin fish and kin. Here Devonian Cheirolepis nests with extant deep sea Malacosteus.

Figure 3. Subset of the LRT focusing on bony ray fin fish and kin. Here Devonian Cheirolepis nests with extant deep sea Malacosteus.

This appears to be a novel hypothesis of interrelationships.
Please let me know if Cheirolepis has been linked to Malacosteus in the academic literature so I can provide the citation.


References
Ayres WO 1848. pp. 64–73. In: Proceedings of the Boston Society of Natural History, Vol. 3. Proceedings of the Boston Society of Natural History, Boston.
Ayres WO 1849. Description of a new genus of fishes, Malacosteus. Boston Journal of Natural History 6:53–64.
Kenaley CP 2007. Revision of the Stoplight Loosejaw Genus Malacosteus (Teleostei: Stomiidae: Malacosteinae), with Description of a New Species from the Temperate Southern Hemisphere and Indian Ocean. Copeia. 2007 (4): 886–900. doi:10.1643/0045-8511(2007)7[886:

wiki/Cheirolepis
wiki/Malacosteus

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