Distribution and Paleoecology of Gloitidia Inexpectans Olsson, 1914 (Brachiopoda: Lingulidae)

Abstract

The lingulid brachiopod Glottidia inex­pectans, previously known from the Yorktown Formation in Virginia, is here, reported from the Early Pliocene beds of South Carolina and Florida.  Glottidia inexpectans differs from intertidal to shallow subtidal Recent species in apparent habitat bathymetry.  In Virginia, the associated molluscs indicate water depths of 40 to 60 meters, the fishes somewhat deeper.  Associated taxa in Florida apparently lived in subtidal habitats to 20 meters. The proclivity of G. inexpectans for shell degradation parallels the taphonomic destruction patterns of the more thoroughly studied Recent species.  Preservation of specimens in any numbers must combine structural integrity with protection from chemical deterioration.  The 155 pairs of juvenile G. inexpectans here reported from Carter's Grove, Zone 1, Yorktown Formation, and the smaller population reported by Olsson (1914) were preserved within closed valves of Chesapecten jeffersonius, a large species of scallop with thick, well-inflated valves. These two pop­ulations probably represent single spatfalls of Glottidia larvae which settled in gaping scallop shells partially filled with sediment.  They then died of starvation or oxygen deprivation after the valves closed by relaxation of the ligament or by burial.  The physical protection afforded by this micro-habitat appears essential for preser­vation of fragile subadult shells.  Interpreting this assemblage prompted a review of the systematics, ecology, distrib­ution, and taphonomy of Glottidia.