Permian–Triassic Extinction Event - Biotic Recovery

Biotic Recovery

Earlier analyses indicated that life on Earth recovered quickly after the Permian extinctions, but this was mostly in the form of disaster taxa, such as the hardy Lystrosaurus. The most recent research indicates that the specialized animals that formed complex ecosystems, with high biodiversity, complex food webs and a variety of niches, took much longer to recover. It is thought that this long recovery was due to the successive waves of extinction, which inhibited recovery, and prolonged environmental stress to organisms, which continued into the Early Triassic. Recent research indicates that recovery did not begin until the start of the mid-Triassic, 4 million to 6 million years after the extinction; and some writers estimate that the recovery was not complete until 30M years after the P–Tr extinction, i.e. in the late Triassic.

A study published in the journal Science found during the Great Extinction, the oceans' surface temperatures reached 40°C, which serves as an explanation for such a large time frame for recovery. Simply, it was too hot for life to survive.

During the early Triassic (4–6 million years after the P–Tr extinction), the plant biomass was insufficient to form coal deposits, which implies a limited food mass for herbivores. River patterns in the Karoo changed from meandering to braided, indicating that vegetation there was very sparse for a long time.

Each major segment of the early Triassic ecosystem—plant and animal, marine and terrestrial—was dominated by a small number of genera, which appeared virtually worldwide, for example: the herbivorous therapsid Lystrosaurus (which accounted for about 90% of early Triassic land vertebrates) and the bivalves Claraia, Eumorphotis, Unionites and Promylina. A healthy ecosystem has a much larger number of genera, each living in a few preferred types of habitat.

Disaster taxa (opportunist organisms) took advantage of the devastated ecosystem and enjoyed a temporary population boom and increase in their territory. Microconchids are the dominant component of otherwise impoverished Early Triassic encrusting assemblages. For example: Lingula (a brachiopod); stromatolites, which had been confined to marginal environments since the Ordovician; Pleuromeia (a small, weedy plant); Dicroidium (a seed fern).