Two new Howesia specimens fail to reveal that rhynchosaurs are really lepidosaurs

Wednesday, September 16, 2026 16:01

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Following academic traditions
going back to Benton 1985, Spiekman et al 2026 reported, “Rhynchosaurs are unusual archosauromorph reptiles…”.

This is incorrect. Back in the days before software, rhynchosaurs used to be ‘considered’ lepidosaurs arising from Rhynchocephalia = Sphenodontia.

Benton 1985 (in the earliest days of software-assist analysis) used too few taxa and nearly all were suprageneric to move rhynchosaurs to archosauromorphs. Not good.

Gauthier 1986 likewise allied pterosaur lepidosaurs with archosauromorphs with too few taxa.
Benton 1999 did likewise with pterosaurs with too few taxa.

Here in the large reptile tree (2011 to 2026, LRT, 2340 taxa, rhynchosaurs are still lepidosaurs arising from Sphenodontia.

Spiekman et al 2024 also mistakenly allied tanystropheid lepidosaurs with archosaurormorphs due to too few taxa. None of the above academics show any interest in adding pertinent taxa to their cladograms. Is this a lack of curiosity? Not a good trait for a scientist.

Figure 1. Rhynchocephalian and Rhynchosaur palates. That’s Priosphenodon in the middle leading to Mesosuchus and Howesia, to Trilophosaurus and Azendohsaurus and rhynchosaurs. That’s where the palatine grows as large as and alongside the maxilla. In derived taxa these two bones fuse creating the illusion that the maxilla has the entire tooth pad. Look at those palatine stems on Priospbenodon, which really come out on rhynchosaurs.

Rhynchocephalia leading to rhynchosaurus
have unusual palates and tooth rows (Fig 1) not found otherwise in tetrapods, along with a long list of cranial and post-cranial traits.

Figure 2. This cladogram goes back to 2016. Subset of the large reptile tree, the Rhynchocephalia. This clade also includes Rhynchosauria, Azendohsaurus and Trilophosaurus.

Figure 2. Howesia now nests with Priosphenodon = Kaikaifilusaurus in the LRT, taxa not mentioned in Spiekman et al 2026. Taxon exclusion is a common problem in paleontology.

Dilkes 1995
published a line drawing of a reconstruction based on two specimens of Howesia (Fig 3). Note the traditionally and typically wide skull and strong tooth plates. These specimens (SAM 5884 and SAM 5885) were not added to the LRT, but the palate is shown in figure 1.

Figure 3. The original skull of Howesia from Dilkes 1995. Note the traditionally and typically wide skull and strong tooth plates. Compare to figure 4.

Spiekman et al 2026
published µCT scans from two newer specimens the authors attributed to Howesia. The more complete specimen, SAM-PK-K10180, is shown in figures 4–6) and this is the one scored for the LRT.

Figure 4. The 10180 specimen of Howesia from Spiekman et al 2026 in frame 1 with arrows and abbreviations. Frame 2 removes the arrows and abbreviations. Frame 3 changes the colors to standard DGS colors. Frame 4 moves the disarticulated squamosal and quadratojugal back to the temple and cheek. Note the narrow skull and loss of almost all marginal and palatal dentition. Compare to figures 1 and 3.

Distinct from other rhynchosaurs and their outgroups
Howesia has a tall narrow skull (Figs 4, 5) and the marginal and palatal teeth are reduced to vestiges = barely present.

Figure 5. The dorsal view of the skull of Holmesina in this jpeg, easier to spend time with as only one frame is shown. Note the narrow skull and virtual lack of teeth, different from other rhynchosaurs (Fig 1).

Missing from Spiekman et al 2026
is the pre-rhynchosaur Priosphenodon (Fig 6) a taxon described in 2003. so unknown by Dilikes 1995. In the LRT Howesia nests with Priosphenodon.

According to Wikipedia,
“Priosphenodon is an extinct, large herbivorous eilenodontine rhynchocephalian known from the Early Cretaceous (Albian) of Argentina. It is one of the largest known sphenodontians.”

See any confusion here? Any taxon exclusion? The remedy is easy.

The LRT needs to be tested by adding taxa. This list is shown in figure 3.

Figure 6. Middle Triassic Howesia to scale with its Early Cretaceous sister, Priosphenodon, a 2993 taxon not mentioned by Spiekman et al 2026,

This appears to be a novel hypothesis of interrelationships
prompted by the vacuum left behind in the taxon exclusion found in Spiekman et al 2026.

References
Benton MJ 1985. Classification and phylogeny of diapsid reptiles. Zoological Journal of the Linnean Society 84: 97-164.
Benton MJ 1999. “Scleromochlus taylori and the origin of dinosaurs and pterosaurs”. Philosophical Transactions of the Royal Society B: Biological Sciences. 354 (1388): 1423–1446.
Broom R 1905. Preliminary notice of some new fossil Reptiles collected by Mr. Alfred Brown at Aliwal North, S. Africa. Records of the Albany Museum. 1 (4): 269–275.
Dilkes D 1995. The rhynchosaur Howesia browni from the Lower Triassic of South Africa”. Palaeontology. 38: 665–685.
Gauthier J 1986. “Saurischian monophyly and the origin of birds”. In Padian, K (ed.). The Origin of Birds and the Evolution of Flight. Memoirs of the California Academy of Sciences. Vol. 8. San Francisco: California Academy of Sciences. pp. 1–55.
Spiekman SNF.et al (6 co-authors 2024. A redescription of Trachelosaurus fischeri from the Buntsandstein (Middle Triassic) of Bernburg, Germany: the first European Dinocephalosaurus-like marine reptile and its systematic implications for long-necked early archosauromorphs. Swiss Journal of Palaeontology. 143 (1): 10. doi:10.1186/s13358-024-00309-6
Spiekman SNF et al (7 co-authors) 2026. Micro‐CT informed cranial anatomy of the early rhynchosaur Howesia browni, with implications for rhynchosaur skull evolution. Papers in Palaeontology. 12 (4). doi:10.1002/spp2.70105. ISSN 2056-2799