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| Anatomy of Mirasaura from Spiekman et al. (2025). Note the integumentary appendages in a, d, e and f, as well as the skeletal in h. |
Mirasaura grauvogeli is a new species of unique Middle Triassic diapsid from France, named and described by Spiekman et al. (2025). The most obvious and striking feature of Mirasaura are the tall integumentary appendages running across its back – a feature seen in the equally bizarre Longisquama of Kyrgyzstan, which has been known since the 1970s.
What's with the crest?
The function of these integumentary appendages (which together form a 'crest') in Mirasaura and Longisquama is still quite a mistery. Sharov (1970) proposed that the appendages in Longisquama could've helped it slow down its fall when jumping from branch to branch or to the ground. This idea isn't brought up by Spiekman et al. (2025), however they themselves consider a kind of visual communication most likely, ruling out flight, thermal insulation (also proposed by Sharov) and any kind of mimicry or camouflage. Spiekman et al. (2025) also suggests that, unlike often depicted in paleoart, the appendages of Mirasaura and Longisquama probably couldn't have lowered down posteriorly across the body in a kind of 'resting' position.
Phylogenetic implications
Using the data matrix of Pritchard et al. (2021), Mirasaura and Longisquama were both found as sister taxa within Drepanosauromorpha with drepanosauromorphs subsequently being found as non-saurian diapsids. Little support was found for an archosauromorph position, which would imply Longisquama and Mirasaura are the first (and currently only) reptiles outside Avemetatarsalia to have preserved integumentary structures. The paper already noted how such integumentary structures can theoretically evolve in any amniote, thus it wouldn't be surprising if more reptiles with similar structures and integuments were found in the future.
