ARTHROPODA (III): General features (cont.) (Crustacea study images,
other arthropod study images;
|
Trait | Chelicerata | Trilobitomorpha | Crustacea | 'Uniramia' |
---|---|---|---|---|
2: cephalothorax (=prosoma*),
abdomen (=opisthosoma*) |
3: head, thorax, abdomen (=pygidium*) |
2: head, trunk (primitive) or
3: head, thorax, abdomen (derived) |
2: head, trunk (Myriapoda) or
3: head, thorax, abdomen (Insecta) | |
Acron- Pr++ | # none | # none | # none | # none |
Segment #1- De++ | # (lost) | # antenna | # first antenna | # antenna |
Segment #2- Tr++ | # * chelicerae + | # * head leg** | # second antenna | # (lost)*** |
Segment #3 | # * pedipalps/legs | # head leg** | # * mandible | # * mandible |
Segment #4 | # oviger/legs | # head leg** | # first maxilla | # maxilla |
Segment #5 | # legs | thoracic leg** | # second maxilla | # labium/maxilla |
Segment #6 | # legs | thoracic leg | thoracic leg | thoracic leg |
Segment #7 | # legs | thoracic leg | thoracic leg | thoracic leg |
Segment #8 | abdomen limbs
(if present) |
thoracic leg | thoracic leg | thoracic leg |
in embryo | A*2 | 1*2 | 1*2 | 1*2 |
in adult: | A*2+ or 2*3 | 1*2 | 2*3 | 1*3 |
+ mouth site in
Pycnogonida only |
** thoracic-like | *** transitory in Symphyla |
Copyright (c) 2017 by A. Richard Palmer. All rights reserved.
(revised Dec. 19, 2016)