Pentamerida is an order of biconvex, impunctate shelled, articulate brachiopods that are found in marine sedimentary rocks that range from the Middle Cambrian through the Devonian.Moore, Lalcker and Fischer, 1952, Invertebrate Fossils, McGraw-Hill Pentamerids are characterized by a short hinge line where the two valves articulate, inner areas above the hinge line that slope inwardly from the beak of each valve, and a well-developed spondylium on the pedicle valve. The spondylium is a raised platform for muscle attachment found in the middle of the interior pedicle valve, generally toward the hinge and beak. The pedicle valve is the one that the pedicle, or hold-fast stalk, attaches to. The brachidia, which hold the lophophore, the ciliated feeding arms, are looped, as in the

Orthida Orthida is an extinct order of brachiopods which appeared during the Early Cambrian period and became very diverse by the Ordovician, living in shallow-shelf seas. Orthids are the oldest member of the subphylum Rhynchonelliformea, and is the ord ...

. The Short hinge line helps distinguish the pentamerids from the ancestral orthids from which they are obviously derived. The hinge line is not as short as found in the

Rhynchonellida The taxonomic order Rhynchonellida is one of the two main groups of living articulate brachiopods, the other being the order Terebratulida. They are recognized by their strongly ribbed wedge-shaped or nut-like shells, and the very short hing ...

Athyridida Athyridida is an order of Paleozoic brachiopods included in the Rhynchonellata, which makes up part of the articulate brachiopods. The Athyridida are the Rostrospracea of R.C Moore, 1952,Moore, Lalcker and Fischer, 1952, Invertebrate Fossils, McG ...

. In the older classification of Moore, Lalicker and Fischer, 1952, the Pentamerida was regarded as simply an order in the Class Articulata and divided into two suborders, the Syntrophiacea and the Pentameracea, presented with superfamily endings of the time. The treatise on Invertebrate Paleontology, Part H Brachiopida (revised)Classification des Brachiopoda
/ref> now places the Order Pentamerida in the Class Rhynchonellata and divides it into the suborders Syntrophiidina and Pentameridina. The Syntrophiidina are the more primitive of the two.

References

The Paleobioloy Database Pentamerida entry
Prehistoric brachiopods Prehistoric animal orders Brachiopod orders Cambrian first appearances Late Devonian animals Late Devonian extinctions Rhynchonellata {{paleo-protostome-stub