fossil millipedeFossil of the Orsadesmus rubecollus. Photo courtesy of Ted Daeschler ANS.

Orsadesmus rubecollus
(archipolypodan millipede)

Impression fossils of small millipedes 1-2 cm in length have been found in the Floodplain Pond facies at Red Hill. These specimens have recently been described and named Orsadesmus rubecollus. They belong to the family Zanclodesmidae and the order Archidesmida.

The fossil records of millipedes dates back to at least the Middle Silurian (late Wenlock to early Ludlow) and Lower Devonian (Lockhovia) of Scotland. The earliest North American record for millipedes comes from the Emsian (Middle Devonian) of eastern Canada. Later Devonian records come from localities in New York and eastern Pennsylvania. Millipedes —as well as virtually all other terrestrial arthropods— are essentially unknown for the Tournaisian (lowermost Carboniferous), but their record improves substantially by the Viséan and a variety of millipedes are known from the Late Carboniferous.

Millipedes belong to a group of myriapod arthropods called the Diplopoda (=double feet); the name comes from the presence of two pairs of feet per body segment. Most Paleozoic taxa had been placed in the Archipolypoda, a group once considered to be of equal taxonomic rank to the Diplopoda, but is now generally regarded as a subordinant taxon.

reconstruction of a millipede

Millipeds appear to have been among the earliest animals to exploit terrestrial ecosystems. Authorities have long suspected that early millipeds —unlike early chelicerate arthropods— were fully terrestrial early in their evolutionary history. However, morphological evidence of obligate terrestriality (i.e., the presence of respiratory spiracles) was, until recently, unknown in any milliped fossils older than the Carboniferous. It's now known that at least some species were fully terrestrial by the Middle Silurian, and quite probably well before that.

Modern millipedes typically inhabit damp terrestrial habitats and the overwhelming majority of them are detritivores. Presumably, many if not most of the Devonian forms were detritivores. Perhaps the most famous fossil milliped, Arthropleura (Late Carboniferous) is the largest known terrestrial arthropod. It attained a length in excess of 2 m.

Some other invertebrates have also been found at Red Hill. One of these, Gigantocharinus, is a new species of trigonotarbid arachnid. Other invertebrate fossils include an unidentified myriapod, the fragmentary remains of a scorpion and an arthropod trackway.

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Scientific Papers:
Wilson, H.M., Daeschler, E.B., and Desbiens, S., 2005, "New flat-backed archipolypodan millipedes from the Upper Devonian of North America" Journal of Paleontology, 79:738744
Web:
Myriapoda.org's website on millipeds:
www.myriapoda.org

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