Inarticulate brachiopods
Dignomia lepta Locality: Rabbit Ridge Although brachiopods are some of the most common marine invertebrates known from fully marine deposits of the Cape Supergroup, prior to 2016 they were unknown from the Witpoort Formation. On Rabbit Ridge however, lingulid brachiopods are extremely common within one laterally extensive mudstone horizon in the lower Witpoort Formation (Harris and Gess, in prep). Lingulid brachiopods are inarticulate brachiopds, meaning that their two shells are joined by a soft muscular articulation rather than an interlocking shelly joint. Detailed analysis of the brachiopods has shown that they all belong to one species, which is tentatively designated as Dignomia lepta. With an early Famennian age, this probably represents the youngest record of the genus Dignomia. The lingulids are infaunal (burrow living) filter feeders which are remarkably tolerant to environmetal stresses. Their presence in the deposit has some interesting implications for the ecology of the Witpoort Formation (see Rabbit Ridge). |