Chelicerata


Chelicerata synapomorphies:
Body: cephalothorax (prosoma) + abdomen (ophistosoma)
Chelicers to handle food
Pedipalps as sense organs
Lacks antennae

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Pycnogonida
Sea spider

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Xiphosura
Horseshoe crab

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Eurypterida

Sea scorpion

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Arachnida

Araneae


Araneae synapomorphies:
Poisonous glands on chelicers
Silk glands
Male pedipalps modified for mating purposes

Arachnida - Araneae - Mesothelae
  Ryuthela secundaria

Opistothelae synapomorphies:
Posterior silk glands
Max 6 silk glands
Reduced body segmentation

Arachnida - Araneae - Mygalomorphae
Tarantula
Synapomorphy:
Middle silk glands missing

Arachnida - Araneae - Araneomorphae
Nephila inaurata
Synapomorphies:
Chelicers pointing downward
Cribellum

Arachnida - Scorpiones
Scorpion
Synapomorphy:
Pectin (comb-shaped chemical-sensing organ)

Arachnida - Opiliones
Daddy long legs
Synapomorphies:
Tubelike mating organ
Stink glands

Arachnida - Acari
Tick
 Mite
Synapomorphy:
Rutella (blade-like scrapers)

Arachnida - Solifugae
Sun spider
Synapomorphies:
Stout chelicers
Malleoli (flask-formed sense organs)

Arachnida - Pseudoscorpiones
Book scorpion
Synapomorphies:
Advanced nursing behaviour
Special structures in sperm cells

Arachnida - Ricinulei
Hooded tickspider
Synapomorphies:
Cucullus (plate covering the chelicers)
3 leg pairs used for mating purposes

Arachnida - Palpigradi
Microwhip scorpion
Synapomorphy:
Mouth placed anterior on cephalothorax

Arachnida - Amblypygi
Whip spider
Synapomorphy:
1 pair of legs used as sensing organs

Arachnida - Thelyphonida
Whip scorpion
Synapomorphies:
Anal glands with acetic acid
Camarostrum (joints that have grown together under the head)
Head to head, hooked together, when mating

Arachnida - Schizomida

Synapomorphies:
Prosoma in 3 parts
Short flagellum