Allonnia, Dore and Reid, 1965

Bengtson, S & Collins, D, 2015, Chancelloriids of the Cambrian Burgess Shale, Palaeontologia Electronica 10 (14), pp. 1-67 : 20-21

Genus ALLONNIA Doré and Reid, 1965

Type Species. Allonnia tripodophora Doré and Reid, 1965 (based on isolated sclerites).

Species Known from Scleritome Preservation. Allonnia phrixothrix Bengtson and Hou, 2001

(junior synonym: Allonnia junyuani Janussen et al. 2002 ); Allonnia tintinopsis n.sp.

Diagnosis. Chancelloriids with 3+0 sclerites having long, apically directed rays. Modified sclerites around the apical orifice form a palisade-like tuft.

Remarks. The type species, Allonnia tripodophora Doré and Reid, 1965 , was based on isolated sclerites from the Lower Cambrian of Carteret (Manche, Normandy). As discussed above, the sclerites are difficult to distinguish morphologically from those of species known from whole-body preservation in shales. Moore et al. (2014) noted that sclerites of Al. tripodophora may have had all three rays protruding from the body surface, which might set them apart from more bilaterally symmetrical sclerites of Al. phrixothrix (and, by implication, those of Al. tintinopsis ), the latter having one strongly protruding ray (the ascending ray) and two (lateral) rays closer to the body surface. They established a sclerite-based species, Archiasterella charma , dominated by 3+0 sclerites, and implied that Al. phrixtothrix should possibly be reassigned to Archiasterella . We leave this proposal open and acknowledge that further studies of the variability and distribution of sclerites in assemblages and full-body preservation will be necessary to resolve the taxonomic issue.

Allonnia junyuani Janussen et al., 2002 was established on material from the same section as Al. phrixothrix Bengtson and Hou, 2001 . Janussen et al. (2002) discussed two forms previously figured by Chen et al. (1996) as Form A and Form B. They stated that Al. junyuani “definitely represents” Form A, and chose as holotype the specimen figured by Chen et al. (1996, p. 91) as “Type A, new Chancellorid gen. et sp. nov. ” They further included in the species the “Chancelloriid, genus, species uncertain” figured by Hou et al. (1999, p. 155, figure 225) and used this specimen to reconstruct the body plan of Al. junyuani . The specimen is the holotype of Al. phrixothrix . Consequently, Al. junyuani Janussen et al., 2002 is a junior synonym of Al. phrixothrix Bengtson and Hou, 2001 .

Kloss et al. (2009) discussed the validity of the names and concluded that “it is possible that only Form B is A[l]. junyuani , whereas Form A is simply a synonym for A[l]. phrixothrix . ” As the holotype of Al. junyuani according to its original authors belongs to Form A ( Janussen et al., 2002), the conclusion that the species are different is untenable.