Taphonomic feedback is the idea that accumulation of organic remains either enhances the habitat for some organisms (positive taphonomic feedback), and/or degrades the habitat for others (negative taphonomic feedback). Examples of epibionts living on skeletal remains are direct evidence of positive taphonomic feedback. Disruption of infaunal burrowing activities by skeletal fragments is an example of negative taphonomic feedback; direct fossil evidence of this phenomenon has not been documented previously. Infaunal organisms are vulnerable to exhumation or entombment during storms, but organisms that burrow can also re-establish viable life positions subsequently. For example, when modern lingulids re-burrow after exhumation, they first dig downward and then turn upward, forming a U-shaped burrow. If entombed, they burrow upward. Lingulid escape burrows previously documented date only to the Triassic, and, like modern lingulids, appear to have been restricted to fine siliciclastic sediments. In contrast, an Upper Ordovician occurrence from Ohio contains hundreds of articulated cf. Pseudolingula sp. clustered beneath dozens of disarticulated, concave-down Rafinesquina shells in a storm-reworked shell gravel. Serial sectioning reveals the complex burrows of these lingulids deflecting around shell-fragment obstacles. Burrows also show that when the lingulids encountered the Rafinesquina valves, they followed the concave surface upward toward the highest point, thereby lodging themselves beneath the domed shell. The entrapment of cf. Pseudolingula sp.beneath Rafinesquina demonstrates that lingulid brachiopods have long had the ability to burrow upward and re-establish themselves after burial by a storm event, and is direct evidence of a negative taphonomic feedback mechanism by which infaunal escape behaviors were rendered ineffective by the presence of skeletal debris.
- Environmental Engineering,
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