Megalograptidae

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Megalograptidae
Temporal range:
Ma
Megalograptus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Order: Eurypterida
Infraorder: Diploperculata
Superfamily: Carcinosomatoidea
Family: Megalograptidae
Caster & Kjellesvig-Waering, 1955
Genera

Megalograptidae are a family of

chelicerate arthropods
commonly known as "sea scorpions".

The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. All known members of the Megalograptidea are from the Late Ordovician of Laurentia[1] with the exception of the large Pentecopterus from the Middle Ordovician.

Description

Megalograptids are characterized by large exoskeletons with ovate to triangular scales. The prosoma (head) is subquadrate, with a tonguelike anterior process bearing marginal spines, and compound eyes on the top front of the head. The chelicerae (claws in front of the mouth) are small and short. The first and third pairs of walking legs are short, with diverging or closely spaced spines. The second pair of walking legs is enormously developed, with long paired spines. The fourth pair of walking legs are nearly spineless. The preabdomen, the front portion of the body, is narrow with axial furrows, while the postabdomen is moderately narrow with broad, flat and curved appendages on the last body segment. The telson is short and lanceolate.[2]

Classification

The Megalograptidae are thought to be relatively primitive (between the genus

Mixopteroidea since the sixth podomere in the swimming leg resembles the reduced podomere found in the Mixopteridae.[1]

Genera

Family Megalograptidae Caster & Kjellesvig-Waering, 1955

See also

  • List of eurypterids

References

  1. ^
    PDF
    )
    on 2011-07-18.
  2. ^ Størmer, L 1955. Merostomata. Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata, P36.