Sea scorpions (eurypterids), extinct giant aquatic arthropods, were apex predators. New research suggests that early species of the scorpion-like, spiny-limbed carcinosomatoid eurypterids fed on trilobites, while later species favored armored fish. Carcinosomatoids evolved into scorpions, but giant scorpions 400 million years old as Praearcturus and Brontoscorpionas stated in Monster walks (TV series), were probably crustaceans.
Reconstruction of Pentecopter (170 cm long), the earliest Ordovician (467 Ma) sea scorpion (eurypterid) from Iowa, USA. Image credit: John Alexander.
Sea scorpions (eurypterids) were ancient aquatic reptiles (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 in length, the largest bugs that ever lived. The eurypterids also include the carnivorous carcinosomata, i.e.
Carcinosomatoids used their long spiny limbs to capture and hold prey and to grab mud. Computer modeling shows they were slow swimmers, preferring life near the sea floor as ambush predators.
A new review of fossils found with megalograptids suggests that they are mainly associated with trilobites (a variety of extinct marine arthropods).
Carcinosomatids tend to be associated with lightly armored phyllocarid crustaceans and lingulid brachiopods (lamp shells).
Myxopterids tend to be associated with more heavily armored fish, such as thelodonts, osteostracans, and pteraspids.
Fossil droppings (coprolites) confirm that they ate trilobites, armored fish and even conspecifics (like cannibals).
The suggestion that eurypterids influenced the evolution of armored fishes into a carnivore: prey arms race is often dismissed.
This research suggests that myxopterids and pterygotids did have some influence on their evolution (and our own very ancient ancestors).
Megalograptus is interpreted to be more basal than previously thought, implying that the diversity of early (Ordovician) eurypterids is overestimated.
Scorpions probably evolved from a mixopteran-like ancestor by evolving claws (pedipalps), a stinger, and comb-like sensory pectines on their undersides.
Giant scorpions may be nightmares, but they actually existed during the Carboniferous period in Scotland: Pulmonoscorpius and Gigantoscorpion.
Reconstruction of Pulmonoscorpius, a giant (70 cm long) Carboniferous (330 Ma) scorpion from Scotland. Image credit: Junnn11 / CC BY-SA 4.0.
An even longer (1 m) scorpion, the so-called Praearcturusfrom Herefordshire in England, also claimed to have lived 412 Ma.
However, the indentations on its carapace, the pustular ornamentation, and the curved first body segment suggest that this is in fact a crustacean.
Benettartraof the same layer and region, may be related to (or slightly less than) Praearcturus.
Brontoscorpionproposed as an 86 cm long (400 Ma) scorpion as shown in the BBC TV series Monster walks, is known only from a small part of its claw and is probably a crustacean. Image credit: Impossible Photos.
Brontoscorpion (86 cm long), from Worcestershire in England (400 Ma), as featured in the award-winning BBC TV series Monster walks is also probably a crustacean.
Therefore, giant scorpions did not exist until the Carboniferous period, 70 Ma later, along with 2 m long monstrous millipedes and giant dragonfly relatives with a 75 cm wingspan.
Living scorpions gradually acquired their modern features. Early scorpions had more primitive legs and eyes and lacked a preoral cavity for feeding on land, so they were probably aquatic or amphibious.
The oldest scorpion was Parioscorpion from the Early Silurian (437 Ma) from Wisconsin, but has been reinterpreted as a trilobite-like arthropod.
The oldest known scorpion is now Dolichophonus (433-438 Ma) from Scotland.
This research was published in Neues Jahrbuch für Geologie und Paläontologie.
_____
Braddy, SJ 2024. Carcinosomatoid eurypterid paleoecology and phylogeny: ichnology and paleocommunities. Neues Jahrbuch für Geologie und Paläontologie; doi: 10.1127/njgpa/2024/1206
