Colombophiloscia, Leistikow, 2001

Leistikow, Andreas, 2001, A new species of Caraiboscia Vandel, 1968 from South America, and a type species for Colombophiloscia gen. n. (Crustacea: Oniscidea: Crinocheta), Journal of Natural History 35 (4), pp. 497-514 : 513

Relationships of Caraiboscia Vandel, 1968 and Colombophiloscia gen. n.

Both Caraiboscia and Colombophiloscia are known to live in the upper layers of the soil, they are adapted to this endogeous way of life. These adaptations are similar in both genera and may support a sister group relationship of the two genera, with the following apomorphic characters:

E modi®ed tricorn-like setae on the dorsum: leaēt scales,`BlaÈttchenschuppe’ of Schmalfuss (1978) [tricorn-like seate with simple cuticular scale];

E compound eyes reduced to four ommatidia [compound eyes consisting of about ten ommatidia];

E antennula with a single row of erected aesthetascs [antennula with aesthetascs paired in medial line];

E lateral endite bearing mostly simple teeth [teeth of inner set cleft].

In particular, the presence of leaēt scales on the dorsum is a character found in several other genera of Crinocheta and is most likely to have evolved several times. In Pentoniscus vargasae Leistikow, 1998 , structurally diOEerent leaēt scales can be found as an adaptation to an endogeous life. They might work as devices to prevent staining of the tegument with soil particles and therefore can be found in many endogeous, pigmentless species, i.e. in members of Colombophiloscia Vandel, 1968 and Troglophiloscia Brian, 1929 , in Pentoniscus vargasae Leistikow, 1998 and in Trichorhina Budde-Lund, 1908 and other Platyarthrida e ( Schmalfuss, 1978). These so-called`soies-eÂcailles’ ( Vandel, 1968) are derived tricorn-like setae. This manner of protection is rather diOEerent to the tergal humps of several endogeous Synocheta as described by Schmalfuss (1977). In contrast to other, reductive characters of these ground-dwellers (reduction of pigment and number of ommatidia), the evolution of specialized tricorns is complex but does not support monophyly of all endogeous taxa, since the ®ne structure of the leaēt scales is diOEerent in the taxa mentioned above. Moreover, Caraiboscia and Colombophiloscia diOEer in the shape of the antennula, the structure of the molar penicil, the dentation of the maxillula from both Troglophiloscia and Pentoniscus . From the platyarthrid taxa, they can be distinguished in having a three-articulate antennal ¯agellum instead of a two-articulate one.

Simple teeth on the maxillula are found in the genera Araucoscia VerhoeOE, 1939 and Pseudophiloscia Budde-Lund, 1904 ( Leistikow, 1998b,c), but the disposition of these teeth is diOEerent and more derived from the well-known 41 6 pattern which can be found in Caraiboscia and Colombophiloscia . The arrangement of the aesthetascs on the antennula is characteristic for the two genera and unique among the Oniscidea yet known, they are set upright and form a cockscomb when seen from a more lateral direction. This arrangement is good evidence for the sister group relationship of the two genera, since it is quite complex and unique among South American crinochete terrestrial isopods of philosciid facies.