Camenellan

The camenellans, consisting of the genera "Camenalla", "Dailyatia", "Kennardia", "Kelanella" and "Lapworthella", are a (probably monophyletic) group of Tommotiid invertebrates from the Cambrian period, reconstructed as sister to all others (plus brachiopods and phoronids). They are known from isolated sclerites, but are believed to have a scleritomous, "Halkieria"-like construction.
"Dailyatia" and "Camenella" have distinct dorsal (symmetrical) and lateral (asymmetric) sclerite morphologies.
The same has been asserted for "Lapworthella" even though that has not always been the common perception.
It has been argued that "Camenella", "Kelanella" and "Lapworthella", assuming a slug-like anatomy, had an anterior 'head valve' followed by pairs of asymmetric valves running in pairs along their dorsal surface.
The 'head valve' in "Lapworthella" - that is the bilaterally symmetric Morph A valve - is thought to have fused from two ontogenetically separate sclerites. Dailyatia has a similar double-mounded structure at the tip of its A type sclerites.
Growth rings in all are marked out by prominent external ridges.
Taxonomy.
Two families:
Kennardiidae : three sclerite morphs, one of which (conventionally termed the A morph) is bilaterally symmetrical, the other two occurring in sinistral and dextral variants. Includes "Kennardia" and "Dailyatia", and questionably "Shetlandia"
Lapworthellidae: sclerites occur in something of a morphological continuum, but essentially form a single type with a sinistral and dextral version, possibly with the anterior-most pair of sclerites fusing into a single bilaterally-symmetrical, dual-tipped sclerite.
"Dailyatia" species: