The Holarctic chilopod subfamily Plutoniuminae Bellman, a corrected na
me for Plutoniinae, consists of two genera, Plutonium Cavanna and Thea
tops Newport, and six species; synapomorphies between them show that t
he subfamily is a monophyletic group and that the different number of
spiracles, 19 pairs in Plutonium and 9 pairs in Theatops, is only a ge
neric-level character. and P. zwierleini Cavanna occur in Sicily, Sard
inia, Napoli and Sorrento provinces in mainland Italy, and Granada Pro
vince, Spain. Theatops erythrocephalus (C. L. Koch) occurs along the e
astern side of the Adriatic Sea in the Balkan Peninsula. and in coasta
l Spain and Portugal. The other four species - T. posticus (Say), T. s
pinicaudus (Wood), T. phanus Chamberlin, and T. californiensis Chamber
lin - occur in the United States and northwestern Mexico. Theatops pos
ticus occupies a broad area east of the Central Plains from Connecticu
t and southern New York to the south Florida keys and eastern Texas; a
n allopatric western population extends from southwestern New Mexico a
nd western Chihuahua to the southern Great Basin, the California deser
t east of the Sierra Nevada, the Pacific Ocean in Baja California Nort
e, the Channel Islands off the southern California coast, and the east
ern slope of the Coast Range near the latitude of San Francisco Bay. T
heatops spinicaudus occurs sympatrically with T. posticus in two areas
of the east; the inner surfaces of its caudal legs possess variable s
eries of ridges and teeth. Theatops phanus occurs in epigean and subte
rranean environments in southern Texas and extends from east of highwa
y I-35 to west of the Pecos River; the inner surfaces of its caudal le
gs also possess variable series of ridges and teeth. The distribution
of T. californiensis, anatomically convergent with T. erythrocephalus,
is as described previously, but locality information is detailed, as
only one site, the type locality, is currently known. Relationships am
ong the plutoniuminine species are postulated as P. zwierleini + (T. s
pinicau-dus + (T. phanus + (T. erythrocephalus +(T. posticus + T. cali
forniensis)))). The Plutoniuminae and Cryptopinae logically share ance
stry, and the Scolopocryptopinae may warrant elevation to family statu
s.