(the sea spiders) Sea spider, class Pycnogonida , from Pratt, 1923.
Despite their common name, sea spiders are not true spiders. This is an unusual group that has been known for a long time, but it has been difficult to place relative to other arthropod groups. Pycnogonids are currently thought to probably represent an early divergence from the evolutionary line leading to the other Chelicerates . There are approximately 1,000 species of Pycnogonids , all of them found in the marine environment. They are distributed worldwide, including polar regions. Although commonly found in the intertidal they are also found at depths up to 7,000 meters. Most pycnogonids are about 1 cm. or less in size, but some deep sea forms reach up to 70 cm. across between leg tips. They have a unique "proboscis " which they use to pierce and suck liquid from seaweeds and various animals such as hydroids , seaweeds, bryozoans , ascideans , and other invertebrates.
Despite their common name, sea spiders are not true spiders. This is an unusual group that has been known for a long time, but it has been difficult to place relative to other arthropod groups. Pycnogonids are currently thought to probably represent an early divergence from the evolutionary line leading to the other Chelicerates . There are approximately 1,000 species of Pycnogonids , all of them found in the marine environment. They are distributed worldwide, including polar regions. Although commonly found in the intertidal they are also found at depths up to 7,000 meters. Most pycnogonids are about 1 cm. or less in size, but some deep sea forms reach up to 70 cm. across between leg tips. They have a unique "proboscis " which they use to pierce and suck liquid from seaweeds and various animals such as hydroids , seaweeds, bryozoans , ascideans , and other invertebrates.
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