Definitions

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Pereon

Anterior portion of trunk with thoracopods, exclusive of maxillipedal somites and appendages.
(syn. paraeon, pereion) [McLaughlin, 1980]
Term referring to the free (unfused) thoracomeres posterior to the maxilliped-bearing thoracomeres in malacostracans. [Brusca and Brusca, 2002]
That portion of the thorax not fused to the head (when such fusion occurs). [Brusca and Brusca, 2002]
Thoracic division of body, comprising six free pereonites (thoracomeres) and bearing uniramous appendages. [Holdich and Jones, 1983]
Thoracic segments 2-8 bearing the locomotory appendages, or pereopods. (Thoracic segment 1 is part of the cephalon and bears the maxilliped.). [Wilson, 1989]
(Taxon-specific: Order Cumacea) Division (tagma) of body between head (cephalon) and abdomen (pleon) or, more accurately, between cephalothorax and abdomen. Consists of five somites (pereonites), each bearing appendages (pereopods). Morphologically not equivalent to thorax (with a total of eight somites) because first three somites are fused to cephalon (i.e., cephalothorax). [Stachowitsch, 1992]
(Taxon-specific: Order Tanaidacea) Division (tagma) of body between head and abdomen (pleon). Morphologically not equivalent to thorax (with a total of eight somites) because first thoracomere (bearing maxillipeds) is fused to head, the second being covered by and fused to carapace; accordingly, pereon can be considered to consist of seven or six segments (pereonites).
(syn. peraeon, pereion) [Stachowitsch, 1992]
(Taxon-specific: Order Amphipoda) Division (tagma) of body between head (cephalon) and abdomen (pleon) or more accurately between cephalothorax and abdomen. Consists of four to seven segments (pereonites), each bearing appendages (pereopods). Morphologically not equivalent to "thorax" because first (and occasionally second) thoracic segment (bearing maxilliped) is fused to cephalon.
(syn. peraeon, pereion, mesosome) [Stachowitsch, 1992]
(Taxon-specific: Order Isopoda) Middle or thoracic region of the body, consisting of seven segments or pereonites, first fused with cephalon in isopods. [Kensley and Schotte, 1989]
(Taxon-specific: Order Isopoda) Second and largest division (tagma) of body between head (cephalon) and abdomen (pleon) or more accurately between cephalothorax and pleon. Typically consists of seven segments (pereonites); morphologically not equivalent to thorax because first (and occasionally second) thoracic segment (bearing maxillipeds) is fused to cephalon.
(syn. peraeon, pereion) [Stachowitsch, 1992]
(Taxon-specific: Order Isopoda) Those thoracic segments not fused to the cephalon. [Wetzer et al. 1997]
(Taxon-specific: Order Mysida) Term occasionally applied to that part of thorax not fused with head, i.e., second (or third) through eighth thoracomeres.
(syn. peraeon) [Stachowitsch, 1992]
(Taxon-specific: Subclass Branchiura) Region of body comprising three free thoracic somites (the first thoracomere being fused to head). [Stachowitsch, 1992]
(Taxon-specific: Order Thermosbaenacea) In one interpretation of main body regions, division between cephalon (head + first thoracic somite) and abdomen. Accordingly, pereon consists of seven somites (pereonites), their appendages being termed pereopods.
(syn. pereaon, pereion) [Stachowitsch, 1992]