Siphoniulida

Shelley, Rowland M. & Golovatch, Sergei I., 2011, Atlas of Myriapod Biogeography. I. Indigenous Ordinal and Supra-Ordinal Distributions in the Diplopoda: Perspectives on Taxon Origins and Ages, and a Hypothesis on the Origin and Early Evolution of the Class, Insecta Mundi 2011 (158), pp. 1-134 : 50

Order Siphoniulida incertae sedis ( Fig. 23 )

The rarest order, the monofamilial Siphoniulida are known from only two areas some 19,200 km (12,000 mi) apart on opposite sides of the world. It was first discovered on Sumatra at essentially the same site as Siphonocryptida , and there is a small area in southern Mexico / Guatemala ( Fig. 23 ) ( Pocock 1894; Hoffman 1979b, 1980a, 1999; Sierwald et al. 2003; Bueno-Villegas et al. 2004). All locations are tropical, that in Sumatra lying essentially on the Equator and the New World site being to the north; aside from the discoveries of the order and the holotype of Siphoniulus albus Pocock, 1894 , Siphoniulida have not been encountered again in the Old World. While additional populations may await discovery, the present limited and vastly disjunct occurrences indicate great age, relictual status, and decline toward extinction ( Golovatch and Kime 2010). The most informative works are Hoffman (1979b) and Sierwald et al. (2003); the latter readdressed affinities but could not resolve them. The combination of a juliformian body and colobognathan head suggests that Siphoniulida may be a remnant of an early intermediate lineage. Could Siphoniulida be the sole surviving remnant (a “living fossil”) of a transition stage between Colobognatha and Eugnatha? We have no answer but suggest that dissection and SEM examinations of siphoniulid mandibles, as well as molecular studies, might be meaningful.

Figures

Figure 23-25. Distributions. 23) Distribution of the “minor” orders. Star/Circled Areas, Siphonocryptida (Colobognatha); Dots, Siphoniulida (Helminthomorpha incertae sedis). 24) Known (solid lines) and projected (dashed lines) distributions of the Subterclass Eugnatha showing the locations of significant fossils. The arrow points to the Kodiak Island, Alaska, USA, record of Chordeumatida (Tingupidae). Inverted triangle, approximate location of Gobiulus sabulosus Dzik, 1975, the Cretaceous spirobolidan fossil from Mongolia; Asterisk, location of Protosilvestria sculpta, the Oligocene cambalidean fossil in Quercy, France (Mauriès 1992). 25) Known (solid lines) and projected (dashed lines) distributions of the Superorder Juliformia showing the locations of significant fossils. Parameters as in Fig. 1 except no records or samples are available from the dotted area in North America, the Great Basin Physiographic Province, western USA. Inverted triangle, approximate location of Gobiulus sabulosus Dzik, 1975, the Cretaceous spirobolidan fossil from Mongolia; Asterisk, location of Protosilvestria sculpta, the Oligocene cambalidean fossil in Quercy, France (Mauriès 1992). The question mark indicates the generalized record of Epinannolenidea from Northern Territory, Australia (Black 1997).