Zoology 250 Lecture 26 ARTHROPODA (IV):
Subphyla Chelicerata, Trilobotimorpha, Uniramia
- 1) Subphylum CHELICERATA (sea spiders, horseshoe crabs, spiders, mites)
- a) 2 tagmata, bear chelicerae in place of 1st antenna, uniramous legs
- b) Cl. Pycnogonida: 1 pr ovigers, 4 pr walking legs, tiny abdomen
- c) Cl. Merostomata: 'living fossils' because 400 million-year old fossils very similar to living forms, only 4 living species; 5 pr walking legs (first 4 with claws), abdominal book gills, tail spine
- d) Cl. Arachnida: most diverse class; 1 pr pedipalps, 4 pr walking legs, abdomen lacks walking legs, compound eyes lost,
- 2) Subphylum TRILOBITOMORPHA (extinct trilobites)
- a) 3 tagmata; head with 1 pr antennae & 4 pr legs like thoracic legs
- b) variable number of thoracic segments with similar biramous limbs
- c) variable number of abdominal segments fused as pygidium
- 3) Subphylum UNIRAMIA (myriapods & insects)
- a) 2nd antennae lost, uniramous limbs, spiracle/trachea system
- b) SupCl. Myriapoda: 2 tagmata, trunk with many similar legs, compound eyes lost
- Cl.Chilopoda: 15 - 177 pr of legs; 1st pr bear poison claws; mostly predatory
- Cl. Diplopoda: 100 - 700 pr of legs; adjacent trunk segments fuse yielding 2 pr legs per body unit (diplopodia); mostly herbivorous
- c) SupCl. Hexapoda: 3 tagmata, 2nd maxillae fuse as labium, thorax with 3 pr walking legs, abdomen lacks limbs
- Cl. Apterygota: insects lacking wings
- Cl. Pterygota: winged insects
- SubCl. Exopterygota: hemimetabolous life history
- SubCl. Endopterygota: holometabolous life history
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(revised Jan. 14, 1999)