The Obolellata are a class of Rhynchonelliform brachiopods with two orders, Obolellida and Naukatida. They are essentially restricted to the lower-middle Cambrian.
[Streng, M., A. D. Butler, J. S. Peel, R. J. Garwood, and J.-B. Caron. 2016. A new family of Cambrian rhynchonelliformean brachiopods (Order Naukatida) with an aberrant coral-like morphology. Palaeontology, 59:269–293.]
Obolellida
Obolellida is a small, extinct order of
inarticulate brachiopods that existed from the early to middle
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...
period. The relationship of the Obolellida with other inarticulates is unclear, and were previously grouped together with the
Siphonotretacea, before being given their own order.
One representative, ''
Mummpikia'', has been linked to the origin of calcitic shelled brachiopods more generally, hinting that obolellids may be paraphyletic.
Trematobolidae includes taxa such as ''
Alisina'', whose soft-part anatomy is partly known.
Anatomy
The shell is typically
impunctate,
biconvex, and oval or subcircular in shape. They are like other inarticulates in that, as with the
lingulids, the shell has no hinge, at least in the earliest examples. It is thought they may have used a hydraulic mechanism. However they later seem to develop a primitive articulation, in which some used a levator mechanism for opening the shell. At the posterior is a ventral valve with a defined flat-shelf. The
pedicle
Pedicle or pedicel may refer to:
Human anatomy
*Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures
...
opening can be positioned at various positions.
Naukatida
Some of these are coral-like creatures.
References
Key reference:
{{Taxonbar, from=Q7075263
Prehistoric brachiopod orders
Cambrian first appearances
Cambrian extinctions