How the dragon got its frill

JUNE 25, 2019

by University of Geneva

The frilled dragon exhibits a distinctive large erectile ruff. This lizard usually keeps the frill folded back against its body, but can spread it as a spectacular display to scare off predators. Researchers at the University of Geneva (UNIGE), Switzerland, and the SIB Swiss Institute of Bioinformatics report in the journal eLife that an ancestral embryonic gill of the dragon embryo turns into a neck pocket that expands and folds, forming the frill. The researchers then demonstrate that this robust folding pattern emerges from mechanical forces during the homogeneous growth of the frill skin due to the tensions resulting from its attachment to the neck and head.

In Jurassic Park, while the computer programmer Dennis Nedry attempts to smuggle dinosaur embryos off the island, he is attacked and killed by a mid-sized dinosaur that erects a frightening neck frill. This fictional dinosaur is clearly inspired by a real animal known as the frilled dragon, which lives today in northern Australia and southern New Guinea. These lizards, also known as Chlamydosaurus kingii, have a large disc of skin around their head and neck. This frill is usually folded back against the body, but can spread in a spectacular fashion to scare off predators and competitors. Folding of the left and right sides of the frill occurs at three pre-formed ridges. But it remains unclear which ancestral structure evolved to become the dragon's frill, and how the ridges in the frill form during development.

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