Biogeography of East African montane forest millipedes - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 112

Mazumbai, but many of the forest isolates in both
ranges are sill totally unknown.
Of the 13 or 14 Usambarian genera presumed
to be 'montane', at least six are strictly endemic.
The two harpagophorid genera, Obelostrptus and
Apoaenophora, are of unknown geographic ainiy;
they seem to have little in common with the South
African taxa and may represent a little known (or
largely exinct) Ethiopian fauna. The endemic
genus and species Elythesmus enghoffi (Cryp-
todesmidae: Thelydesminae) is known only from
Amani, and is interesing in showing similariies
with the Liberian genus heyesmus; related taxa
may later be found in Cenral Africa. The ai-
niies of the two gomphodesmid genera Gom-
phoesmus and Us ambaranus are not yet
established, but presumably lie with some other
(probably lowland) regional taxa. These two
genera (each monotypic) are of interest in that the
first occurs in the easten segment, the latter in
the westen, of the Usambaras: vicariaion at the
generic level paralleling the situaion in Apoc-
tenophora in which two species represent the
genus in the two regions. With respect to
oydesmids, it is singular that no species of
Lyoesmus have yet been ound. This family is
exclusively represented by Ceratoesmus, with two
taxa only in the easten range, and seven in the
westen, and every indicaion that many others
will be discovered in unsampled forest isolates.
Three species may be ound at a single localiy;
one species (. ansatus) has local races in both the
East and West Usambaras and n he Ngurus;
subspeciaion may occur between adjacent iso-
lates in the West range (e.g. . coiaius); one
species pair (. msuyai and . eburatus) links the
Usambaras with Pongwe Mountain far to the
south. There is some reason to believe that speci-
aion in Ceratoesmus was already well advanced
before development of the savanna biome con-
densed the genus back into the mountains where
it is now mostly confined. Biogeographically there
are few connecions between the Usambaran mil-
lipede fauna and that of the Ulugurus. One
spirostrepid genus (undescribed!) is represented
in both ranges as well as the Uzungwas, but it has
lowland species as well and is probably not a rain
forest obligate.

Ceratodesmus

Rhododesmus

lringius

Figure 6.1. Modificaions in the male genitalia of three
related oxydesmid genera associated with the Easten Arc
Mountains. All four of the distal processes labelled a, b,

and d
are present, but represented by diferent coniguraion.
Cratoesmus (upper right), associated with the Usambara and
Nguru mountains, has process b enlarged and modified into a
hoodlike sucture and process

c

enlarged and shieldlike.
Rhooesmus (lower right), occurring in the Uluguru and
norhen Uzungwa ranges, has process d shortened and dis-
tally concave with laciniate edges, process b elongated and
falcate, process

c

added. In this
drawing of the enire gonopod, C indicates the unit homolo-
gous to the coxa of the walking legs, P idenifies the prefemur,
and F he femur. More distal elements cannot be confidently
homologised. linius (lower left) of he Uzungwa Mountains
has process

reduced in size, and process

c e

enlarged and parly concealing the bases of the
others, which are reduced in size.
All three of the genera have one or more lowland species,
but are considered neoendemics of the range indicated, poss-
ibly evolving from a widespread common ancesral orm. Of
he three, Cratosmus and linius appear to be most closely
related even hough neither occurs in the Ulugurus. However,
either, both, or some intermediate taxon may be epected to
occur in the Rubeho and Ukaguru mountains. Numbers
beside the outlined areas indicate how many species of each
genus are known rom each.

c