Alienacanthus malkowskii was a placoderm armored fish that lived in the seas covering what is now Europe and northern Africa during the late Devonian, about 365 million years ago.
First discovered in the 1950s, this species was originally known only from some strange elongated bony elements that were interpreted as fin spines. But more recent finds of near-complete skull material revealed a surprise — the “spines” were actually this animal’s extremely elongated lower jaw!
Around 2.5m long (~8’2″), it was probably a streamlined open ocean swimmer that may have used its bizarre underbite similarly to the snouts of modern billfish, slashing at and stunning soft-bodied prey.
References:
- Jobbins, Melina, et al. “Extreme lower jaw elongation in a placoderm reflects high disparity and modularity in early vertebrate evolution.” Royal Society Open Science 11.1 (2024). https://doi.org/10.1098/rsos.231747
- Kulczycki, Julian. “Upper Devonian fishes from the Holy Cross Mountains (Poland).” Acta Palaeontologica Polonica 2.4 (1957). https://www.app.pan.pl/article/item/app02-285.html
- Wikipedia contributors. “Alienacanthus” Wikipedia, 12 Jan. 2026, https://en.wikipedia.org/wiki/Alienacanthus