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Temporal range: Silurian
Slimonia acuminata 1.jpg
Slimonia acuminata
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Merostomata
Order: Eurypterida
Superfamily: Pterygotioidea
Family: Slimonidae
Genus: Slimonia
Page, 1856

See text

Slimonia is a genus of Silurian eurypterid roughly similar to the genus Pterygotus. Slimonia resembled Pterygotus, save that the former's telson is larger, and that its body was smaller and more slender than the latter. Unlike Pterygotus, which lived in estuaries, Slimonia species lived exclusively in freshwater environments. Slimonia preyed on smaller fish, such as heterostracans and early osteostracans by seizing and rending them with its large chelicerae. The largest species of Slimonia was extremely long, around two meters. It carried its body on spindly legs and was likely an ambush predator. The lungs of the species were located on the underside of the body in a series of folds.[1] Slimonia's telson was used much like that of a scorpion to subdue prey, but were scorpion tails flex upward and over when used in an attack, Slimonia's was seemingly more suited to flex from side-to-side. Using its small but powerful front limbs to hold its victims firmly, Slimonia would then slash and cut its victims with the spike on its telson to kill the intended prey item.[2]


Life reconstruction of Slimonia acuminata

Slimonia is distinguishable by its quadrate (roughly square) prosoma, or head, with small compound eyes on the front corners. They had large cordate bodies, with a narrow postabdomen and a telson with a "strongly expanded anterior half." Their chelicerae (claws) were small; their walking legs had denticles, but no spines. Genital appendages were long and narrow in both males and females.[3]


There are three species currently classified under Slimonia:

  • Slimonia acuminata Salter, 1856 - Silurian, Herefordshire, England
  • Slimona boliviana Kjellesvig-Waering, 1973 - Silurian, Cochambamba, Bolivia
  • Slimonia dubia Laurie, 1899 - Silurian, Pentland Hills, Scotland


  1. ^ Fortey, Richard A. (1998). Life: A Natural History of the First Four Billion Years of Life on Earth. New York: Alfred A. Knopf. pp. 146–7. ISBN 0-375-40119-9. 
  2. ^
  3. ^ Størmer, L 1955. Merostomata. Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata, P: 30.