Sea scorpions (eurypterids), extinct giant aquatic arthropods, were apex predators. New research suggests that early species of the scorpion-like carcinosomatoid eurypterids, with spiny limbs, fed on trilobites and later species preferred armoured fishes. Carcinosomatoids evolved into scorpions but giant 400 million year old scorpions like Praearcturus and Brontoscorpio, as featured in Walking with Monsters (TV series), were probably crustaceans.
Sea scorpions (eurypterids) were ancient aquatic creepy-crawlies (arthropods, with a segmented body, exoskeleton and jointed limbs) that lived from 467 Million years ago (Ma) to ca. 253 Ma.
Some pterygotid eurypterids grew to nearly 2.6 m long, the biggest bugs that ever lived. Eurypterids also include the predatory carcinosomatoids, i.e. megalograptids, carcinosomatids and mixopterids, with long spiny limbs, that grew up to 2 m long.
Carcinosomatoids used their long spiny limbs to capture and hold prey and for mud-grubbing. Computer modelling indicates they were slow swimmers, preferring life near the seafloor as ambush predators.
A new review of the fossils found alongside megalograptids suggests that they mainly associate with trilobites (diverse extinct marine arthropods).
Carcinosomatids tend to associate with lightly armoured phyllocarid crustaceans and lingulid brachiopods (lamp shells).
Mixopterids tend to associate with more heavily armoured fishes, like thelodonts, osteostracans, and pteraspids.
Fossil faeces (coprolites) confirm that they ate trilobites, armoured fishes and even their own kind (as cannibals).
The suggestion that eurypterids influenced the evolution of armoured fishes in a predator: prey arms-race, is often dismissed.
This research suggests that mixopterids and pterygotids did have some influence on their evolution (and our own very ancient ancestors).
Megalograptus is interpreted as more basal than previously thought, which means that the diversity of early (Ordovician) eurypterids has…
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