EVENTS AND APPROXIMATE DATES IN EARLY DIPLOPOD EVOLUTION
(adapted from Shelley & Golovatch, 2011, Insecta Mundi 0158, Table 6, pp.
1. (Diagram 1). 524 ma (million years ago).
Paleozoic Era, Mid-Cambrian Period. Evolution begins as ancestral form(s)
crawl onto still attached Avalonia Terrain, disperse onto Gondwana proper, and
radiate explosively into empty terrestrial environments in absence of predators
and with all niches vacant and unoccupied.
2. 524-480 ma. Paleozoic, Mid-Cambrian-Early Ordovician.
Penicillata/Chilognatha, Pentazonia/Helminthomorpha, Colobognatha/Eugnatha,
Julida/ Nematophora/Merocheta diverge. Polyxenida, Polyzoniida,
Siphonocryptida, Spirostreptida s. l./Cambalidea, Chordeumatida, Siphoniulida,
and Polydesmida arise and spread between Avalonia and Gondwana proper.
3. (Diagram 2). 480 ma. Paleozoic, Early Ordovician.
Ancestral populations of Pentazonia, Colobognatha, Eugnatha, Nematophora,
and the existing orders Polyxenida, Polyzoniida, Siphonocryptida,
Spirostreptida s. l./ Cambalidea, Chordeumatida, Siphoniulida, and
Polydesmida are partitioned between Avalonia & Gondwana as Avalonia rifts
from latter and begins drifting towards Baltica.
4. 480-450 ma. Paleozoic, Ordovician. Glomeridesmida,
Sphaerotheriida, Siphonophorida, Spirobolida, Epinannolenidea, Spirostreptidea,
Stemmiulida arise and disperse on Gondwana; partitioned Gondwanan populations
of Polyxenida, Polyzoniida, Siphonocryptida, Cambalidea, Chordeumatida,
Siphoniulida, Polydesmida evolve and disperse farther as Avalonia drifts
northward towards Baltica; probably little to no divergence, dispersal, or
advancement among partitioned populations confined to Avalonia due to its
relatively small size and limited number of niches.
5. (Diagram 3). 450 ma. Paleozoic, Late Ordovician. As
land masses collide, forms confined to Avalonia for 30 my disperse onto Baltica
and radiate explosively into its empty terrestrial environments with all niches
vacant; probable burst of evolution and origins of orders Glomerida,
Platydesmida, Julida, Callipodida; divergences and dispersals continue among
forms remaining on Gondwana.
6. (Diagram 4). 440 ma. Paleozoic, Early Silurian. As
land masses collide to form Euramerica, forms on Baltica + Avalonia disperse
onto Laurentia, again radiating explosively into its empty terrestrial
environments with all niches vacant; probable second burst of evolution further
differentiating Glomerida, Platydesmida, Julida, Callipodida, and possibly
Cambalidea and Polydesmida; divergences and dispersals continue among forms
remaining on Gondwana.
7. 415 ma. Paleozoic, Late Silurian. Spirobolidan
population on Gondwana partitioned as North China terrane rifts from
proto-Australia region and begins northward transit to Siberia (+
Kazakhstania); forms on Euramerica differentiate and disperse farther into it,
Archidesmus macnioli fossilized in Proto-Scotland; divergences and
dispersals continue among forms remaining on Gondwana.
8. 400 ma. Paleozoic Era, Early Devonian Period.
Forms on Gondwana further partitioned as South China and Southeast Asia
terranes rift from proto-Australia region and begin northward transits to
Siberia (+ Kazakhstania); spirobolidans on drifting North China terrane
continue passive transit northward; divergences and dispersals continue among
forms on Euramerica and those remaining on Gondwana.
9. 356 ma. Paleozoic, Early Carboniferous. After
collision, forms on Euramerica spread into Siberia + Kazakhstania, which
merged Late Devonian (370 ma). Spirobolidans on North China terrane and
forms on South China and Southeast Asia terranes continue passive transits
northward. Dispersals continue among forms remaining on Euramerica and
10. (Diagram 5). 306 ma. Paleozoic, Late Carboniferous.
Collision of Euramerica + Siberia + Kazakhstania with proto-South
America/Africa part of Gondwana, forming West Pangaea, allows separately evolving
northern and southern diplopod faunas to mix for first time. Proto-South
American forms of Glomeridesmida, Siphonophorida, Spirobolida, Spirostreptidea,
Stemmiulida spread directly into proto-Mexico and then into proto-southwestern
US. US/Illinois oniscomorph pentazonian fossilizes. Spirobolidans on North
China terrane and forms on South China and Southeast Asia terranes continue
passive transits northward. Dispersals continue among forms remaining on
Euramerica and Gondwana.
17. 94 ma. Mesozoic, Late Cretaceous.
Proto-North American part of western Laurasia completely divided by marine
embayment; Glomerida, Platydesmida, Julida, Callipodida partitioned into
separate eastern & western populations. Formerly continuous European/ North
African populations of Glomerida, Platydesmida, Julida, Chordeumatida
partitioned as is continuous stemmiulid fauna through west Africa and eastern
Brazil as Africa rifts from South America. Continuous Indian and Madagascan
faunas partitioned as land masses split. Continued southeast- and northwestward
dispersals on proto-SE Asia part of eastern Laurasia; continued dispersals onto
Gondwanan fragments. Spirobolidan, Gobiulus sabulosus fossilizes in
proto-Mongolia part of eastern Laurasia.
18. 66 ma. Mesozoic/Late Cretaecous-Cenozoic/Paleocene.
Formerly continuous (eastern) North American/European populations of Glomerida,
Platydesmida, Julida, Cambalidea, Chordeumatida, Polydesmida partitioned
(European Cambalidea becoming extinct in Oligocene). South American populations
of Glomeridesmida, Siphonophorida, Spirobolida, Epinannolenidea,
Spirostreptidea, Stemmiulida, Polydesmida partitioned between South America and
19. 50 ma. Cenozoic, Eocene. After collision generates
Himalayan orogeny, faunas of Asia and Indian subcontinent mix; populations of
Siphonophorida, Siphonocryptida, etc., become isolated by rise of Himalayas. As
embayment fully closes, populations of Julida and Callipodida begin dispersing
into and filling void in central North America generating continuous faunas of
today and spreading southward into Mexico/ northern Central America. Glomerida,
Platydesmida, Polyzoniida, Cambalidea, Chordeumatida, Polydesmida spread
southward into Mexico/Central America. Australia + New Guinea split from
Antarctica + South America, partitioning formerly continuous fauna.
20. 14 ma. Cenozoic, Late Miocene. Continued
dispersals north- and southward of Glomeridesmida, Siphonophorida, Spirobolida,
Cambalidea, Chordeumatida, Stemmiulida, Polydesmida in Central America. Antillean
Arc fragments, trapping some forms on different individual islands. Antarctica
becomes an island after rifting from South America then freezes and glaciates,
eradicating all diplopods thereon. Arabian peninsula begins rifting from
Africa, thus partitioning continuous spirostreptidean fauna. Formerly
continuous East Indian/ Southeast Asian faunas partitioned as Indonesian
islands now isolated by water.