Terebratalia transversa

Terebratalia transversa adults can grow up to an average of 50 millimeters long. They have a distinctive, thin two-layer calcitic shell.[5] Like most invertebrates, this species cannot survive in water temperatures higher than 35°C.[5]

Most of the known morphology of T. transversa comes from research based in confocal laser scanning microscopy (CLSM) in conjunction with both scanning and transmission electron microscopy.[6] Juveniles development quickly after their A-P axis emerges due to Hox gene expression with this event being referred to as "metamorphosis." Two days after this metamorphosis, T. transversa display adult morphology. The point at which they are referred to as adults is when they have a clearly separated body from their old two-valved juvenile shell attached via a posterior pedicle.[6] T. transversa has musculature that composes their intestine and have tentacles of which contain multiple striated muscle fibers.[7] They contain no anus nor an articulated valve-hinge.[6]

T. transversa has a nervous system that consists up a brain neuropile found dorsally to a slit found on the surface of their bodies. Their musculature consists of rudiments of pedicle adjustors, shell diductors and shell adductors. It is noted that in recently metamorphic juveniles, musculature can remodel variably. The most significant muscle morphology on the species is referred to as the mantle margin, the tissues responsible for the development of their adult shell.[6]

The larvae are lecithotropic and typically spend four days as juveniles until they undergo metamorphosis. In past studies it appeared that the ideal temperature for T. transversa development is 11°C. The first muscles to develop on the species are the pedicle and mantle muscles. Shortly after, they develop four setae pouches which later connects to their developing circular mantle.[7] In late-stage larvae, the species has their pedicle muslces connected to their central mantle which then is connected to the setae pouches along with an apical musculature. At this point the species is referred to as a three-loved larvae.[7]

Significant populations of Terebratalia transversa are located in the waters near the Pacific Northwest in the United States. Specifically, scientists have collected the species by dredging in the area around the San Juan Channel off the coast of Washington, USA.[3]

As Terebratalia transversa belongs to the phylum Brachiopoda, they share typical characteristics of the classification. Brachiopods are marine invertebrates that developed in the Phanerozoic age known for them developing shells made of calcite.

Due to the very thin calcitic shell of Terebratalia, the primary layer of these shells very rarely fossilize.[5] The shells of the species, when fossilized, help researchers find preserved isotopic signals that aid in uncovering molecular compositions of an old Paleozoic ocean.[5]