HIERARCHICAL CLASSIFICATION OF THE SUBPHYLUM CHELICERIFORMES (SCHRAM AND HEDGEPETH 1978)
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SUBPHYLUM CHELICERIFORMES LINKS
| This taxonomic system comes from Brusca and Brusca (2003), but it is fairly typical of modern taxonomic treatments. The question of the relationship of the Pycnogonids with the Chelicerates has yet to be resolved, and they may be separated into different subphyla. Also, the chelicerata may be a sister group to the trilobites. |
- CLASS CHELICERATA
- The chelicerate body is made of two major body regions: the prosoma (cephalothorax) and opisthosoma (abdomen). The prosoma is usually covered by a carapace-like shield with simple median eyes and compound lateral eyes. Opisthosoma up to 12 segments with a terminal telson. The prosoma bears 4 pairs of uniramous, multiarticulate walking legs. Modified appendages include chelicerae and pedipalps.
- SUBCLASS MEROSTOMATA (2 ORDERS; 1 EXTANT ORDER)
- Marine; heavy exoskeleton; prosoma with large horseshoe-shaped carapace, separated from opisthosoma by hinge; telson forms long tail spine; 2 lateral compound eyes and 2 median ocelli; chelicerae small; pedipalps leg-like, chelate; walking legs chelate, except last pair; last pair with leaf-like processes used for burrowing; spiny gnathobases of limbs macerate food; 1st pair of opisthosomal appendages form flap over reproductive openings; 2nd-6th pairs of opisthosomal appendages form swimming and gaseous exchange organs; opisthosoma unsegmented, with lateral spines; excretory organs coxal; fertilization external; with a “trilobite” larva, benthic.
- Limulus, Carcinoscorpius, Tachypleus.
- Eurypterus, Pterygotus.
- Marine; heavy exoskeleton; prosoma with large horseshoe-shaped carapace, separated from opisthosoma by hinge; telson forms long tail spine; 2 lateral compound eyes and 2 median ocelli; chelicerae small; pedipalps leg-like, chelate; walking legs chelate, except last pair; last pair with leaf-like processes used for burrowing; spiny gnathobases of limbs macerate food; 1st pair of opisthosomal appendages form flap over reproductive openings; 2nd-6th pairs of opisthosomal appendages form swimming and gaseous exchange organs; opisthosoma unsegmented, with lateral spines; excretory organs coxal; fertilization external; with a “trilobite” larva, benthic.
- SUBCLASS ARACHNIDA (11 ORDERS)
- Essentially terrestrial; exoskeleton light to heavy; prosoma wholely or partly covered by a carapace; opisthosoma basically of 13 segments plus telson, often reduced; respiratory organs book lungs or tracheae; without compound eyes; abdominal appendages highly modified or absent; consume liquid (usually pre-liquified animal) food using a pumping pharynx; young stage sometimes with 3 pairs of legs.
- Aponomma, Argas, Boophilus, Dermacentor, Ixodes, Ornithodorus, Zeroseius, Demodex, Halotydeus, Penthaleus, Scirus, Tydeus, Acanthophrynus, Damon, Heterophrynus, Stegophrynus, Tarantula, Hepathela, Liphistius, Cyclocosmia, Ummidia, Atypus, Acanthoscurria, Aphonopelma, Diplura, Loxosceles, Argyrodes, Episinus, Latrodectus, Ulesanus, Hyptiotes, Nephila, Uloborus, Araneus, Argiope, Cyrtophora, Mastophora, Pasilobus, Zygiella, Dolichognatha, Eucta, Leucauge, Meta, Pachygnatha, Clubiona, Erigone, Dicymbium, Linyphia, Agelena, Coelotes, Argyroneta, Lycosa, Pardosa, Pirata, Dolomedes, Pisaura, Oxyopes, Thomisus, Xysticus, Heteropoda, Portia, Salticus, Dinopis, Scytodes, Caddo, Leiobunum, Trogulus, Allokoenenia, Eukoeninia, Koeninia, Leptokoeninia, Prokoeninia, Chelifer, Chitrella, Chthonius, Dinocheirus, Garypus, Menthus, Pseudogarypus, Cryptocellus, Pseudocellus, Ricinoides, Agastoschizomus, Megaschizomus, Nyctalops, Protoschizomus, Schizomus, Androctonus, Bothriurus, Buthus, Centuroides, Chaerilus, Diplocentrus, Hadrurus, Hemiscorpion, Nebo, Parabuthus, Paruroctonus, Tityus, Vaejovis, Biton, Branchia, Dinorhax, Galeodes, Solpuga, Abaliella, Chajnus, Mastigoproctus, Charinus, Thelyphonus, Miranda, Latrodectus, Eremobates, Galeodes, Phalangium, Leioburnum, Trombicula.
- Essentially terrestrial; exoskeleton light to heavy; prosoma wholely or partly covered by a carapace; opisthosoma basically of 13 segments plus telson, often reduced; respiratory organs book lungs or tracheae; without compound eyes; abdominal appendages highly modified or absent; consume liquid (usually pre-liquified animal) food using a pumping pharynx; young stage sometimes with 3 pairs of legs.
- SUBCLASS MEROSTOMATA (2 ORDERS; 1 EXTANT ORDER)
- The chelicerate body is made of two major body regions: the prosoma (cephalothorax) and opisthosoma (abdomen). The prosoma is usually covered by a carapace-like shield with simple median eyes and compound lateral eyes. Opisthosoma up to 12 segments with a terminal telson. The prosoma bears 4 pairs of uniramous, multiarticulate walking legs. Modified appendages include chelicerae and pedipalps.
- CLASS PYCNOGONIDA (1 ORDER) INCERTAE SEDIS
- Marine; opisthosoma very small, unsegmented; prosoma divided into a head with cylindrical proboscis and 3 pairs of appendages (chelicerae, pedipalps, ovigerous legs – non-ambulatory legs used for carrying eggs), and a segmented trunk of 4-6 segments each with one pair of legs borne on the end of large lateral trunk processes; legs often very long with a span of 75 cm; 2 pairs of eyes on rounded tubercle on posterior head region; lateral gut caeca and parts of gonads extend into legs; without excretory or respiratory organs; haemocoel divided into upper and lower sections by horizontal membrane; nervous system not concentrated; eggs brooded by male and hatch as protonymphal larval stage with 3 pairs of appendages.
- Acheilia, Ascorhynchus, Austrodecus, Colossendeis, Delcopoda, Nymphon, Nymphopsis, Pycnogonum, Tanystylum.
- Marine; opisthosoma very small, unsegmented; prosoma divided into a head with cylindrical proboscis and 3 pairs of appendages (chelicerae, pedipalps, ovigerous legs – non-ambulatory legs used for carrying eggs), and a segmented trunk of 4-6 segments each with one pair of legs borne on the end of large lateral trunk processes; legs often very long with a span of 75 cm; 2 pairs of eyes on rounded tubercle on posterior head region; lateral gut caeca and parts of gonads extend into legs; without excretory or respiratory organs; haemocoel divided into upper and lower sections by horizontal membrane; nervous system not concentrated; eggs brooded by male and hatch as protonymphal larval stage with 3 pairs of appendages.
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| By Jack R. Holt and Carlos A. Iudica. Last revised: 02/04/2012 |
