Named By: Miller - 1974.
Classification: Arthropoda, Merostomata, Eurypterida, Megalograptoidea, Megalograptidae.
Species: M. welchi (type), M. alveolatus, M. ohioensis, M. shideleri, M. williamsae.
Size: About 1.2 meters long from the head to the tip of the telson (final segment of the tail).
Known locations: USA.
Time period: Mid to late Ordovician.
Fossil representation: Many individuals, but often of partial remains.
mistaken for a graptolite thanks to only a very spiny leg being
discovered, Megalograptus is now known to have been a large
colloquially known as a ‘sea scorpion’.
Megalograptus is the type genus of the Megalograptoidea, a group of
eurypterids which are primarily identified by the arrangement of spikes
on their third pair of legs. It is thought that the large spines on
the various appendages helped Megalograptus to locate prey hidden
within the soft sediments, and hidden from sight. Like all
eurypterids Megalograptus had a telson, the final segment of the tail
that is analogous to the ‘sting’ we can see on modern land
scorpions. However in Megalograptus this is not expected to have
formed a venomous sting, and instead Megalograptus probably just
ripped prey apart as it ate.
Megalograptus Approached the larger end of the eurypterid scale though larger eurypterids are known, and these in turn may have hunted Megalograptus, especially if they had recently shed their skin and their new exterior had not yet hardened. Other possible predators may have included large orthocones such as Cameroceras. Like with other cephalopods, these would have had hard keratinous beaks capable of crunching through even the hardened exoskeletons of eurypterids
- Merostomata - Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata, P36. - L. Stormer - 1955.