Lissodesmus Chamberlin, 1920

Mesibov, Robert, 2005, The millipede genus Lissodesmus Chamberlin, 1920 (Diplopoda: Polydesmida: Dalodesmidae) from Tasmania and Victoria, with descriptions of a new genus and 24 new species, Memoirs of Museum Victoria 62 (2), pp. 103-146 : 108-109

Lissodesmus Chamberlin, 1920

Lissodesmus Chamberlin, 1920: 135 .— Attems, 1940: 490.— Jeekel, 1970: 336.— Jeekel, 1983: 150.— Jeekel, 1984: 89.— Mesibov, 2003b: 198.

Pseudoprionopeltis (Australopeltis) Johns, 1964: 47 .

Australopeltis Hoffman, 1980: 184.— Shelley et al., 2000: 86.

Type species. Lissodesmus modestus Chamberlin, 1920 , by original designation.

Diagnosis. Small to medium-sized dalodesmids (11–23 mm long, 1.2–2.2 mm vertical diameter) with head + 20 segments, normal pore formula (except L. perporosus ), well-developed paranota with long posterior corner seta, spiracles well-separated on diplosegments and without emergent hair-like structures. Telopodite with small mesal or anteromesal solenomere and tibiotarsus, small to large lateral or anterolateral femoral process and large central prefemoral process; solenomere arising at one-third to one-half the telopodite height. Prefemoral process tip typically undivided; in L. orarius divided apically into two posteriorly directed branches.

Remarks. Chamberlin (1920) erected the monotypic genera Lissodesmus and Tasmanodesmus for the Tasmanian species L. modestus and T. hardyi . The two genera were ignored by Verhoeff (1932, 1936) on the grounds that Chamberlin had published no illustrations, and were regarded as genera of uncertain family placement by Attems (1940). Chamberlin believed the two genera were closely related, but as shown in a recent redescription ( Mesibov, 2004b) T. hardyi is substantially different in gonopod structure from all other Tasmanian dalodesmids, and the posterior corner seta in T. hardyi is short and inconspicuous.

Pseudoprionopeltis martini Carl, 1902 from Melbourne was included by Johns (1964) in his revision of New Zealand Pseudoprionopeltis . He erected the subgenus Australopeltis for P. martini and illustrated the anterior segments and gonopod of a specimen from Cockatoo Creek in the Museum Victoria collection. One of the characters used by Johns to diagnose the new subgenus was the posterior corner seta, which he described as “a long seta inserted just anterior and dorsal of the [posterior paranotal] tooth” ( Johns, 1964: 47).

In his reclassification of the Diplopoda, Hoffman (1980) raised Australopeltis to a genus. Although Chamberlin (1920) had provided a verbal description of the L. modestus gonopod, Hoffman (1980: 150) regarded the gonopod structure of Lissodesmus as “still unknown”. Nevertheless, he placed both Australopeltis and Lissodesmus in Dalodesmidae Cook, 1896 . In doing so, Hoffman formalised the observation by Brolemann (1916) that the circular gonopod aperture in P. martini indicated an affinity between that species and Semnosomidae Brolemann, 1916, which Hoffman (1980) considered a synonym of Dalodesmidae .

Jeekel (1983) made Australopeltis a synonym of Lissodesmus after examining fresh material of Victorian L. martini and Tasmanian L. modestus . Both species had been collected by Jeekel during a 1980 field trip to Australia. Jeekel did not redefine Lissodesmus in the 1983 paper, instead referring the reader to “a previous paper”, then in press, which actually appeared the following year (see below). However, Jeekel (1983) gave a detailed description and clear illustrations of a male of L. martini from Ferntree Gully National Park.

In 1984, Jeekel redescribed L. modestus from topotypical material and added four new Tasmanian species to the genus: L. adrianae , L. alisonae , L. margaretae and L. perporosus . In his key to the genera of Tasmanian Polydesmida , he noted that Lissodesmus could be separated from Tasmanodesmus by the presence in the former of “a long hair mesad of caudal edge of paranota” ( Jeekel, 1984: 89), i.e. the posterior corner seta. L. margaretae Jeekel, 1984 was recently removed from Lissodesmus and placed with three new Tasmanian species in the new genus Dasystigma ( Mesibov, 2003b) .

As delimited here, Lissodesmus is what remains of the group of south-eastern Australian dalodesmids with a head + 20 segments and a long posterior corner seta after exclusion of Dasystigma (spiracles with hair-like structures, wide separation between solenomere and tibiotarsus origins, complex femoral process) and Tasmanopeltis gen. nov. (spiracles with hair-like structures, relatively long unbranched portion of telopodite, mesal “shoulder” process on prefemoral process). Lissodesmus is thus a product of “taxonomic erosion” of a group of similar taxa and is not defined by a set of unique character states. However, it is readily distinguished from the other regional H+20 dalodesmids Atalopharetra Mesibov, 2005 , Bromodesmus Mesibov, 2004 , Gasterogramma , Gephyrodesmus , Tasmanodesmus and Victoriombrus Mesibov, 2004 by its possession of a long seta at the posterior corner of each paranotum and by the gonopod structure shown schematically in Fig. 2 .

To avoid repetition in the species descriptions below, I have omitted mention of the nearly constant non-sexual features which can be seen in the detailed accounts given by Jeekel (1983; 1984) of L. adrianae , L. alisonae , L. martini , L. modestus and L. perporosus . Note that the male antennae are separated by about twice a socket diameter unless otherwise specified.

Distribution. Throughout Tasmania, and in parts of Victoria with annual rainfall over c. 800 mm.

Figures

Figure 2. Diagrammatic posteromesal view of the right gonopod telopodite of a member of the Lissodesmus group. f = femoral process, pf = prefemoral process, s = solenomere, tt = tibiotarsus, u = uncus.