was prompted by running across the above headline and website.
Reported by Anietra Hamper in 2019 under the title:
“Fish Finds: Uncovering the Origins of the Catfish Family Tree” and the subhead: “How evolutionary biologists are using nearly 50-million-year-old fossils for insight into the origins and evolution of catfish.”
The featured taxon
was Middle Eocene Hypsidoris farsonensis (Lundberg and Case 1970, Figs 1, 2), which was subsequently added to the large reptile tree (LRT, 1227 taxa). Unlike many catfish, Hypsidoris retains a toothless bit of loose maxilla.
Figure 1. Hypsidoris in situ. Average length = 20cm.
The featured expert
was Dr Lance Grande, Field Museum, Chicago, USA, who redescribed Hypsidoris in 1986.
Figure 2. Closeup of Hypsidoris skull. Colors and restoration added here. Maxilla is green and lacks teeth.
Hamper et al. 2019 reported,
“The telltale characteristics of catfish – peculiar denticular pectoral and dorsal spines, the lack of scales on the body, cat-like whiskers, the lack of maxiilary teeth in most species, and exceptional sensory ability, fascinate evolutionary biologists as much as they do the passionate anglers who are drawn to the living versions of catfish today.”
Be careful. Taxa are defined by their phylogenetic ancestors, not their traits.
“The only other catfishes that have a well-developed maxilla with teeth today are species in the South American family, Diplomystidae.”
With that bit of info, Diplomystes (Figs 3, 4) was likewise added to the LRT.
Figure 3. Diplomystes in vivo.
Teeth on the maxilla
sounds like it should be primitive. That makes sense, but it’s “Pulling a Larry Martin.“
Figure 4. From Digimorph.org, the skull of Diplomystes camposensis (Arratia 1987).
nests Middle Triassic Robustichthys (Figs 6, 7) as the last common ancestor of catfish AND the Early Carboniferous Eurynotus clade AND the Late Devonian Campbellodus clade. So catfish likely go back to the Late Devonian based on chronological bracketing.
Figure 5. Subset of the LRT focusing on catfish and their relatives. Here Hypsidoris and Diplomystes are not primitive despite retaining maxillae. Currently Middle Triassic Robustichthys is the last common ancestor of all known catfish.
According to the LRT
(Fig 5) the toothy catfish, Diplomystes (Figs 3,4) is not the most primitive catfish. Rather, with the presently tested list, toothless, maxilla-less catfish that more closely resemble Robustichthys are more primitive. Flatter, bottom dwellers are more derived.
Figure 6. Skull of Robustichys, the Middle Triassic ancestor of catfish.
It is possible
that teeth re-evolved in toothy catfish. More likely: catfish had a long ghost lineage back to the Late Devonian not currently represented in the fossil record. Those catfish clades radiated in the meantime.
Figure 7. Middle Triassic Robustichthys diagram. Not the toothless bottom-dweller yet. Shown 90% life size.
(Xu et al. 2014; Xu 2019; Middle Triassic) was described as the largest holostean fish of the Middle Triassic. Seven prior studies attempted to nest Robustichthys on short taxon lists. Taxon exclusion marred all of them. The most recent, Xu 2019, nested Amia, the bowfin, as a highly derived taxon, just the opposite of the LRT which tests many more fish. Xu and all prior authors had no idea that bony fish split shortly after the moray eel, Gymnothorax, itself derived from hybodontid sharks. In the LRT the clade Holostei is polyphyletic and Robustichthys nests with Hoplosternum, the armored catfish (Fig 8).
Figure 8. Hoplosternum in vivo. You can see the armor/bone beneath its shiny skin. Overall it looks more like (= shares more traits with) Robustchthys (Figs 6,7) than toothy catfish (Figs 3,4).
The LRT documents the ancestry of all included taxa
back to Ediacaran worms. Adding taxa resolves all phylogenetic problems.
If you go to university
you will learn exactly what they teach out of an approved, but outdated textbook.
Instead, if you want to learn as much as you can about evolution,
do the work. Build your own LRT. Learn the way things really are and were. Workers won’t like your independence, and you may be ostracized, but you’ll sooner or later understand what they don’t and won’t teach at the university level.
The top six problems in paleontology:
Number one: taxon exclusion.
Number two: borrowing untested cladograms.
Number three: trusting genomic results.
Number four: trusting textbooks and academic traditions.
Number five: freehand reconstructions.
Number six: “Pulling a Larry Martin” = focusing on one to a dozen traits, rather than a complete suite.
Solution: Keep adding taxa to your own trait-based cladogram. Trace specimens with transparent colors and from those tracings create more accurate and verifiable reconstructions.
Grande L 1986. Redescription of Hypsidoris farsonensis (Teleostei: Siluriformes), with a reassessment of its phylogenetic relationships. Journal of Vertebrate Paleontology 7:24–54.
Lundberg JG and Case GR 1970. A New Catfish from the Eocene Green River Formation, Wyoming. Journal of Paleontology. 44 (3): 452.
Xu G-H 2019. Osteology and phylogeny of Robustichthys luopingensis, the largest holostean fish in the Middle Triassic. PeerJ doi: 10.7717/peerj.7184. eCollection 2019.
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