Merostomata is a class of chelicerate arthropods that contains the extinct Eurypterida (sea scorpions) and the extant Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended …

giant water scorpion, any member of the extinct subclass Eurypterida of the arthropod group Merostomata, a lineage of large, scorpion-like, aquatic invertebrates that flourished during the Silurian Period (444 to 416 million years ago). Well over 200 species have been identified and divided into 18 families.

Xiphosura were historically placed in the class Merostomata, although this term was intended to encompass also the eurypterids, whence it denoted what is now thought to be an unnatural (paraphyletic) group (although this is a grouping recovered in some recent cladistic analyses). [3]

The major chelicerate classes are the Merostomata (horseshoe crabs), which are the closest living relatives of the trilobites (Shuster, 1982), the Pycnogonida (sea spiders), and the Arachnida. The latter is divided into seven minor, and three major, orders, the latter being: Scorpiones (scorpions), Araneae (spiders), and Acari (mites and ticks).

May 29, 2020 · The Class Merostomata (Horseshoe Crabs) are an ancient class of animals who evolved in the early Cambrian (570 million years ago) and were a dominant life-form in the seas and oceans of the world until the Permian 310 MYA. Now, they are a very small group consisting of only 4 species in 3 genera and one order (or subclass) Xiphosura.

Merostomata By Phil Myers (horseshoe crabs, eurypterids) The Merostomata includes two rather different groups of marine organisms, the eurypterids and the horseshoe crabs.

Horseshoe crabs are classified into a single order (Xiphosura) and family (Limulidae). Four species are recognized. Many scientists now categorize Merostomata as a class rather than a subclass. The body of a horseshoe crab is covered by a …

The Merostomata are among the oldest living animals, with fossils (FAH-suhls), the remains of ancient animals, dating back 350 million years. Horseshoe crabs are the only living members of the subclass, which includes the now extinct giant water scorpions, or giant sea scorpions.

Merostomata is a class of sub-phylum Celicerata of Phylum Arthropoda. They include extant horseshoe crabs and extinct sea scropions. Systematic Position. Ø Includes extinct sea scorpions (Eurypterida) and extant Horseshoe crabs (Limulus) Ø Marine aquatic forms. Ø Limulus is an example for a living fossil. Ø Prosoma with six pairs of appendages.

Merostomata is the name given to a grouping of the extinct Eurypterida (sea scorpions) and the Xiphosura (horseshoe crabs). The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups.