Table 2.

Compositional Properties of Most Frequently Sampled Metazoan Phyla

Group	Number of Collected Genomes	GC Mean	GC Min	GC Max	GC Skew	AT Skew
Annelida	13	34.95	27.82	44.57	−0.45	−0.06
Arthropoda, Arachnida	41	27.87	15.73	36.8	−0.09	−0.01
Arthropoda, Insecta	193	23.64	12.59	37.6	−0.18	+0.06
Chordata, Actinopterygii	612	44.89	36.82	53.22	−0.25	+0.04
Chordata, Amphibia	155	37.45	30.92	45.1	−0.25	+0.04
Chordata, Aves	110	45.4	42.3	49.51	−0.38	+0.12
Chordata, Mammalia	312	40.13	30.9	45.94	−0.32	+0.09
Chordata, Squamata	101	40.82	35.43	48.46	−0.35	+0.12
Chordata, Testudines	30	38.83	37.29	41.52	−0.35	+0.13
Cnidaria	36	35.39	22.43	49.76	+0.17	−0.16
Echinodermata	22	38.18	26.74	43.66	−0.04	−0.1
Mollusca	75	34.02	21.88	44.98	+0.04	−0.08
Platyhelminthes	32	32.39	25.95	48.31	+0.39	−0.32
Porifera	29	34.76	27.97	43.98	−0.05	0.16

Note.—Data have been downloaded from Mitozoa database vrs. 6 (Lupi et al. 2010) and contain reference and nonreference complete mtDNA sequences.