Ninumbeehan: a new basal tetrapod with side-by-side anterior nares

So et al 2024 wrote,
“Here, we present Ninumbeehan dookoodukah gen. et sp. nov., an early amphibian with specialized adaptations for seasonal estivation from the upper Jelm Formation of the Late Triassic of Wyoming, USA. Ninumbeehan are found in an association of vertebrate  estivation burrows across a locally dense horizon, offering insights into the evolution and ecology of vertebrates amid the challenging conditions of low-latitude Late Triassic ecosystems.”

The phylogenetically odd placement and orientation of the anterior nares appears to have been overlooked. I want to draw your attention to it (Fig 1).

Instead the authors wrote, “expanded posterolateral portion of the premaxilla at the lateral margin of the naris.”

Same thing, essentially.

So et al wrote:
“Here, we describe an unusually dense association of vertebrate estivation burrows from the early-Late Triassic (ca ≥231 Ma) upper Jelm Formation of Fremont County, Wyoming. Burrows contain well-preserved skeletal remains of a new species of stereospondyl amphibian with specialized adaptations for burrowing, unambiguously identifying these amphibians as the tracemakers.”

The published cladogram by So et al
(Fig 2) disassociates Acroplus from Ninumbeehan (Fig 1) despite their similarities (other than the migration of the nares). In the large reptile tree (LRT, 2330 taxa) these two nest together as derived taxa in the Gerrothorax clade = Plagiosaurids. That is one of the most basal tetrapod clades in the LRT.

Cladograms can be like a spectrum: running from red through the colors to purple, magenta and back to red. In this case (So et al, Fig 2) this appears to be what happened.

I’ve seen similar spectra in which basal taxa show up as highly derived.
Something to watch out for.

Pre-lungfish, like Early Devonian Youngolepis
(Fig 3), also survived dry periods by estivating in baked mud burrows. Note the anterior placement of the nares, convergent with Late Triassic Ninumbeehan (Fig 1).

The publication of Ninumbeehan
prompted the reevaluation of Rileymillerus (Fig 1), another small tetrapod that entered the LRT in 2017. The nares are missing, unfortunately, but at least were separated from the lacrimal (tan) by the nasal (pink) as in Ninumbeehan.

Caecilians
The addition of Ninumbeehan and rescoring of Rilleymillerus moved caecilians (Fig 4) to a more basal node within Tetrapoda. We’ll reexamine caecilians tomorrow.

So et al wrote,
“The mandibular ramus of Ninumbeehan bears a secondary tooth row formed by the complete coronoid series lingual to the marginal dentition of the dentary, similar to that observed in Chinlestegophis and caecilians, though the identity of the elements bearing the lingual row of teeth in caecilians is disputed.”

A second row of dentary teeth is not scored in the LRT.

References
So C et al (10 co-authors) 2024. Fossil amphibian offers insights into the interplay between monsoons and amphibian evolution in palaeoequatorial Late Triassic systems. Proc. R. Soc. B 291: 20241041.   https://doi.org/10.1098/rspb.2024.1041

wiki/Ninumbeehan
wiki/Rileymillerus

Source: https://pterosaurheresies.wordpress.com/2025/01/04/ninumbeehan-a-new-basal-tetrapod-with-side-by-side-anterior-nares/