Data from: A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology

Tomteluva perturbata gen. et sp. nov. and Nasakia thulensis gen. et sp.
nov., two new rhynchonelliformean brachiopod taxa, are described from
carbonate beds from the lower middle Cambrian (Series 3, Stage 5) basinal
Stephen Formation, Canada, and the upper lower Cambrian (Series 2, Stage
4) Henson Gletscher Formation, North Greenland, respectively. The two taxa
are characterized by an unusual coral-like morphology typified by a high
conical ventral valve with an anteriorly curved umbo and a tube-like
structure inside the ventral valve, interpreted as pedicle tube. Both
resemble the problematic late middle Cambrian (Drumian) species
Anomalocalyx cawoodi Brock from Australia, whose systematic affiliation is
controversial. Together, the three genera are interpreted as
representatives of a new family of rhynchonelliformean brachiopods, the
Tomteluvidae fam. nov., which is interpreted as an aberrant or derived
taxon within the Order Naukatida. Convergence between the Tomteluvidae and
the coralla of small solitary Cambrian coralimorphs, as well as the late
Palaeozoic reef-building richthofenioid brachiopods, might indicate
adaptation to a similar life habits and environments. However, their small
size (length 4 mm), well-developed pedicle and perfect morphological
symmetry make it more likely that tomteluvids lived attached to frondose
algae or sponges, above the seafloor, in a similar fashion to the
acrotretoid brachiopods with which they show a high degree of
morphological convergence. Morphological features of the pedicle tube of
N. thulensis suggest that the tomteluvid pedicle is homologous to that in
modern rhynchonelliformean brachiopods. This is the first evidence of the
pedicle type within the Naukatida and represents the oldest confirmation
of a rhynchonellate pedicle.