Trait	Chelicerata	Trilobitomorpha	Crustacea	Uniramia
# of TAGMATA
	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)
ANTERIOR LIMBS (*= mouth lies just anterior to this segment in adult):
	| prosoma]	| head]	| head]	| head]
Acron- Pr**	| none	| none	| none	| none
Segment #1- De**	| (lost)	| antennae	| first antennae	| antennae
Segment #2- Tr**	| *+ chelicerae	| * head leg**	| second antennae	| (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
MOUTH LOCATION (*= location of mouth; A= acron; 1,2, etc.= segment number):
in embryo	A*2	1*2	1*2	1*2
in adult:	A*2+ or 2*3	1*2	2*3	1*3
	+ mouth position in Pycnogonida only	** thoracic-like		*** transitory in Symphyla

** segment homology based on brain regions: Pr- Protocerebrum, De- Deuterocerebrum, Tr- Tritocerebrum (Harzsch 2004. Evol. and Devel. 6:303)