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):
Acron- Pr**	none	none	none	none
Segment #1- De**	*Ý chelicerae	antennae	first antennae	antennae
Segment #2- Tr**	* pedipalps/legs	* legsÝ Ý	second antennae	(lost)***
Segment #3	legs	legsÝ Ý	* mandible	* mandible
Segment #4	legs	legsÝ Ý	first maxilla	maxilla
Segment #5	legs	legsÝ Ý	second maxilla	labium/maxilla
Segment #6	legs	thoracic legs	thoracic legs	thoracic legs
Segment #7	abdomen limbs (if present)	thoracic legs	thoracic legs	thoracic legs
MOUTH LOCATION	(*= location of mouth; A= acron; 1,2, etc.= segment number):
in embryo	A*1	1*2	1*2	1*2
in adult:	A*1 or 1*2	1*2	2*3	1*3
.	Ý mouth position in Pycnogonida only	Ý Ý thoracic-like.	.	*** transitory in Symphyla

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