2026 cephalaspid study includes too few outgroup taxa

El Fassi El Fehri et al 2026 described
the taxonomy and phylogeny of British ‘cephalaspids’. Amin El Fassi El Fehri is an up and coming vertebrate palaeontologist from Morocco, based in Zurich who studies early fishes. Mike Benton is a senior co-author from Bristol and a text book author. Joe Keating is the sole corresponding author. He reported, “I’m interested in the transition from jawless to jawed vertebrates, modelling anatomical trait evolution, and methods for reconstructing evolutionary trees with different types of data.”

From the abstract:
“Osteostracans are considered the sister group of jawed vertebrates and are phylogenetically the earliest branching vertebrate lineage to exhibit true paired fins with endoskeletal support. This means they take centre stage in understanding the jawless-to-jawed transition and the origin of paired appendages. Unfortunately, their macroevolutionary significance is obscured by current rudimentary understanding of their taxonomy and phylogenetic relationships.”

“Are considered” = the consensus view = no one in Academia has actually tested this, but this guess is currently acceptable to editors and referees. Perhaps this why the authors confessed to “current rudimentary understanding“.

That’s a good sign. The authors realize there’s no where to go but up from their current nadir.

Figure 1. The osteostracan Cephalaspis (above) compared to the sturgeon Pseudoscaphorhynchus (below). The similarities of these armored morphologies have been overlooked previously. In both cases the jawless or tubular mouth is below the skull, the former towards the front, the latter below the eyes. ” data-image-caption=”

Figure 1. The osteostracan Cephalaspis (above) compared to the sturgeon Pseudoscaphorhynchus (below). The similarities of these armored morphologies have been overlooked previously. In both cases the jawless or tubular mouth is below the skull, the former towards the front, the latter below the eyes.

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg?w=584″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg?w=584″ alt=”Figure 1. The osteostracan Cephalaspis (above) compared to the sturgeon Pseudoscaphorhynchus (below). The similarities of these armored morphologies have been overlooked previously. In both cases the jawless or tubular mouth is below the skull, the former towards the front, the latter below the eyes.” class=”wp-image-41401″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg?w=584 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg?w=108 108w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg?w=215 215w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/12/cephalaspis_pseudoscaphorhynchus588-1.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

In their analysis the authors included too few taxa
(= 86 taxa, 112 characters). They reported, “The strict consensus topology… is very poorly resolved… most branches are collapsed.”

Adding taxa usually resolves cladograms.

Meanwhile
in the large reptile tree (LRT, 2349 taxa, 238 multi-state characters) Hemicyclaspis (Fg 2) and the osteostracans are derived from Early Silurian Thelodus (Fig 2) and basal only to sturgeons (Fig 2), which have also have ventral extensible tubes rather than jaws in adult basal taxa.

The fish portion of the LRT is highly resolved, taking 3 seconds to complete an analysis of 506 taxa.

While it’s good enough in 2026
to focus on separating cephalaspid specimens from one another, it’s not too late to confirm, refute or modify hypothetical interrelationships of cephalaspids as a clade recovered earlier in the LRT in order to elevate current understanding in a wider gamut view.

Figure 1. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor. ” data-image-caption=”

Figure 1. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor.

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg?w=584″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg?w=584″ alt=”Figure 1. Top to bottom: Thelodus a soft jawless fish with a ventral oral opening and gill slits, perhaps a hint of diamond-shaped armor laterally. Hemicyclaspis, adds extensive armor. Acipenser, a sturgeon with a protrusible tube for a mouth and reduced armor.” class=”wp-image-44936″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg?w=584 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg?w=150 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg?w=300 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/05/origin_of_sturgeons588-3.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

From the abstract,
“Here, we perform a geometric morphometric analysis to assess the morphological disparity of ‘cephalaspid’ osteostracans from the Midlands Valley and the Anglo-Welsh Basin”.

A morphometric analysis is a scattergram of dots on an X-Y axis chart
rather than phylogenetic analysis, the ‘gold standard’ of paleontology.

Contra current understanding found in textbooks,
cephalaspids are not extinct. They live on in the form of sturgeons. Ancestors go back to the Cambrian.

References
El Fassi El Fehri A et al (4 co-authors) 2026. The taxonomy and phylogeny of British ‘cephalaspids’. Palaeontology 69(4): e70080.

wiki/Cephalaspidomorphi