Article: Mantle canal patterns in Schizophoria (Brachiopoda) from the Lower Carboniferous of New South Wales

The brachiopod Schizophoria verulamensis Cvancara, from the Lower Carboniferous of the Gresford district, New South Wales, has distinctive mantle canal patterns in small, medium, and large specimens. The different patterns are interpreted as stages in the ontogeny and are thought to result mainly from the growth and enlargement of the genitalia.Changes in the morphology of the canals in pedicle valves throughout six horizons in the Lower Carboniferous sequence show a trend, probably genetically controlled, towards the earlier maturity of the genitalia. The super-imposition of larger or mature mantle canal systems on smaller or immature systems indicates that the canals are impressed by periodic resorption, and it is argued that this probably took place during the winter when there was a stable mantle canal system and little shell deposition. In large specimens there are connexions between the vascula genitalia, vascula media, and lateral canals in the pedicle valve, and between the vascula genitalia and vascula myaria in the brachial valve. It is suggested that the connexions may have increased the amount of oxygenated coelomic fluid circulating over the gonads, possibly causing them to ripen earlier.Pathological variations in the mantle canals are described, and it is shown that the canals are able to adjust to injuries or defects in the shell.