Apateon 2026: Neotony vs Peramorphosis

Schoch et al wrote in their abstract:
“The small, gill-bearing branchiosaurids were the most abundant tetrapods in the Late Palaeozoic of Europe. Other than its mostly microvorous relatives, the 12-cm-long Apateon caducus (v. Ammon 1889) was a small predator in some of the nutrient-rich lakes of the Saar-Nahe Basin in Western Germany. This is the first survey of the entire material which accumulated in the last 130 years. The sample includes 221 specimens from nine different black shale deposits, and it covers a size range from 2 to 33 mm skull length. Unlike often co-occurring Apateon pedestris, A. caducus developed stronger, conical teeth and a firmly sutured upper jaw at smaller size. Gut contents evidence that it fed on small branchiosaurid larvae, most often plankton-feeding Apateon pedestris. In the studied rock sequence, slight morphological differences are recognized from oldest to youngest, and as far as they are consistent, suggest minor evolutionary changes.”

If you want to learn about Apateon (Fig 1) this is the paper for you.

Figure 1. Apateon overall and the skull in palatal and dorsal views. Note the lack of ossification at carpus and tarsus. ” data-image-caption=”

Figure 1. Apateon overall and the skull in palatal and dorsal views. Note the lack of ossification at carpus and tarsus.

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg?w=584″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg?w=584″ alt=”Figure 1. Apateon overall and the skull in palatal and dorsal views. Note the lack of ossification at carpus and tarsus.” class=”wp-image-95265″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg?w=584 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg?w=112 112w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg?w=224 224w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/apateon588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

However,
if you want to learn how Apateon fits into phylogeny of tetrapods, no analysis is provided in the Schoch et al paper. Sister taxa recovered by the large reptile tree (LRT, 2340 taxa) are mentioned in the text.

In the LRT Apateon is a lissamphibian derived from Doleserpeton and basal to frogs (Figs 2,3) + salamanders.

Figure 2. Skull of the frog, Rana ” data-image-caption=”

Figure 2. Skull of the frog, Rana

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg?w=584″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg?w=584″ alt=”Figure 2. Skull of the frog, Rana” class=”wp-image-54441″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg?w=584 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg?w=150 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg?w=300 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/03/rana_skull588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

Schoch et al found
“external larval gills even in the largest individuals’.

So, let’s put that into context with regard to frogs, which have external larval gills in the immature tadpole stage, prior to metamorphosis. Same for most salamanders.

Peramorphosis
causes an organism to grow past the normal adult stage and develop hyper-mature or extra physical traits.

Not sure where normal development stops and peramorphosis starts.

Apateon seems to be a perpetual neonate
By contrast, frogs and salamanders continue to mature into adulthood, like other tetrapods, resorbing the external gills and ossifying the carpals and tarsals. So frogs and salamanders are back on the ‘normal’ ontogenetic trajectory, other than frogs going through a greater metamorphosis from juvenile to adult.

References
Schoch R, Proust M and Mujal E 2026. The branchiosaurid temnospondyl Apateon caducus from the Early Permian of Germany Rainer Palaeodiversity 19 (1), 91-112, (7 August 2026) https://doi.org/10.18476/pale.v19.a4

wiki/Apateon