Trimerellida is an
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
of
craniate brachiopods, containing the
superfamily
SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...
Trimerelloidea and the
families Adensuidae,
Trimerellidae
Trimerellida is an extinct order of craniate brachiopods, containing the superfamily Trimerelloidea and the families Adensuidae, Trimerellidae, and Ussuniidae. Trimerellidae is a small but widespread family of warm-water brachiopods ranging f ...
, and
Ussuniidae
Ussuniidae is a monogeneric Family (biology), family of Ordovician brachiopods aligned with the Trimerellids, but showing additional similarities to the craniids and considered intermediate in Morphology (biology), morphology.
References
...
. Trimerellidae is a small but widespread family of warm-water brachiopods ranging from the mid
Ordovician (Llandeilo) to late Silurian (
Ludlow). Adensuidae and Ussuniidae are monogeneric families restricted to the mid to late Ordovician (Llandeilo to lower Ashgill) of
Kazakhstan.
Trimerellides were massive by the standards of early brachiopods. They had fairly smooth and unornamented shells which were probably
aragonitic
Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...
in composition. The shells were unequally biconvex (both
valves convex to different degrees), in some cases nearly spherical in shape.
There is no opening for the pedicle; individuals were free-living or clustered into congregations similar to modern
oyster reefs.
Trimerellides have some similarities to
rhynchonelliform (articulate) brachiopods, including mixoperipheral shell growth (where the rear of each valve converges towards each other) and the development a fixed hinge between a wide plate on the dorsal valve and a socket-like groove on the ventral valve. Like other craniate brachiopods, the
musculature consisted of two pairs of large and vertically-oriented
adductor muscles
The adductor muscles of the hip are a group of muscles mostly used for bringing the thighs together (called adduction).
Structure
The adductor group is made up of:
*Adductor brevis
*Adductor longus
*Adductor magnus
* Adductor minimus This is o ...
(which close the shell) alongside two pairs of horizontally-oriented oblique muscles (which slide each valve past each other). The inner (internal) pair of oblique muscles extend nearly straight back to the dorsal valve hinge plate, in contrast to craniids and craniopsids, where the oblique internals splay out and attach besides the posterior adductors. A shelf is usually present near the middle of each valve, in front of the anterior adductors
References
Bibliography
* Modzalevskaya, Tatyana Lvovna (2003). "Silurian and Devonian brachiopods from Severnaya Zemlya" (Russian Arctic). ''Geodiversitas'' 25 (1). pp. 73–107.
Prehistoric brachiopods
Prehistoric animal orders
Brachiopod orders
Craniata
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