A NEW OCCURRENCE OF THE MILLIPEDE PALAEOSOMA (ARCHIPOLYPODA) IN THE CARBONIFEROUS OF SILESIA, POLAND, AND ITS IMPLICATIONS FOR THE DISTRIBUTION OF MILLIPEDE GENERA IN THE TROPICS OF EUROAMERICA DURING THE PENNSYLVANIAN

Palaeosomatids are very large Carboniferous millipedes with relatively simple dorsal morphology. These millipedes are less well know than are the spiny euphoberiids or the gigantic arthropleurids also found in Carboniferous rocks of the Euroamerican coal belts. Yet, one of the first described specimens belonging to this genus is 195 mm long, making it about equal in size to the larger Euphoberiidae (“giant spined millipedes”).

Palaeosomatids have been described previously from the coal-measures of Sparth Bottoms (Westphalian A), Lancashire, England. Here we report on Palaeosoma associated with plant material and trigonotarbid arthropods, from the Carboniferous (Namurian) of Silesia. The millipede is similar in morphology to the congeneric specimens described from England. The occurrence of congeneric forms of Palaeosoma in Silesia and England provide further evidence of the broad distribution of millipede genera in the Euroamerican tropics, previously demonstrated by the occurrences of euphoberiid, amynilyspedid, arthropleurid, and other millipede taxa.

Palaeosomatids, contrary to previous reports, are not spinous, but do share a number of characters with spinous archipolypods. Like the eurphoberiids, palaeosomatids reached a large size, and have their body ring divided into two basic parts: a pleurotergite composed of a fused tergite and pleurite (a common arrangement in some types of millipedes); and what appear to be broad sternites. The millipedes were protected by ozopores (repugnatorial pores), located on lateral nodes. Palaeosomatids do not fit into any millipede orders as presently diagnosed.

Based on the presence of lateral expansions of the pleurotergites, Palaeosoma was previously determined to be a flat-backed millipede. Palaeosoma, however, may have been more subrounded in cross-sectional shape, with a ring-structure somewhat like that of the Euphoberiidae.