Dailyatia bacata scleritome reconstruction

The camenellans, consisting of the genera ''Camenalla'', ''Dailyatia'', ''Kennardia'', ''Kelanella'', ''

Wufengella ''Wufengella'' is a genus of extinct camenellan " tommotiid" that lived during the Early Cambrian (Stage 3). Described in 2022, the only species ''Wufengella bengtsonii'' was discovered from the Maotianshan Shales of Chiungchussu (Qiongzhusi) F ...

'' and ''Lapworthella'', are a (probably

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

) group of

Tommotiid Tommotiids are an extinct group of Cambrian invertebrates thought to be early lophophorates (the group containing Bryozoa, Brachiopoda, and Phoronida). The majority of tommotiids are mineralised with calcium phosphate rather than calcium ca ...

invertebrates from the

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

period, reconstructed as sister to all others (plus

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...

s and

phoronids Phoronids (scientific name Phoronida, sometimes called horseshoe worms) are a small phylum of marine animals that Filter feeder, filter-feed with a lophophore (a "crown" of tentacles), and build upright tubes of chitin to support and protect thei ...

). They are primarily known from isolated

sclerite A sclerite ( Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonl ...

s, but are believed to have a scleritomous, ''

Halkieria The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the smal ...

''-like construction.Skovsted, C. B., Betts, M. J., Topper, T. P. & Brock, G. A. The early Cambrian tommotiid genus ''Dailyatia'' from South Australia. Mem. Assoc. Australas. Palaeontol. 48, 1–117 (2015).Murdock, D. J. E., Donoghue, P. C. J., Bengtson, S. & Marone, F. Ontogeny and micro-structure of the enigmatic Cambrian tommotiid ''Sunnaginia'' Missarzhevsky, 1969. Palaeontology 55, 661–676 (2012). This was confirmed by the discovery of ''

,'' known from articulated remains, which showed camenellans to be mobile, worm-like animals. ''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.Devaere, L. & Skovsted, C. B. New early Cambrian sclerites of ''Lapworthella schodakensis'' from NE Greenland: advancements in knowledge of lapworthellid taxonomy, sclerite growth and scleritome organization. Geol. Mag. (2016). doi:10.1017/S0016756816000698 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 Laurie, 1986: three sclerite morphs, one of which (conventionally termed the A morph) is bilaterally symmetrical, the other two occurring in

sinistral and dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

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:

References

Prehistoric protostomes Cambrian invertebrates Paleozoic life of New Brunswick Paleozoic life of Newfoundland and Labrador Paleozoic life of Nova Scotia {{Palaeo-protostome-stub Cambrian genus extinctions