Coral biodiversity from Morocco after the End-Triassic mass extinction

Each new coral-bearing outcrop found in Lower Jurassic strata is useful to understand the evolution of corals between the end-Triassic mass extinction and the Toarcian anoxic event. Here we provide new taxonomic data on corals issued from fieldwork on four outcrops from the region of Amellagou, in the High Atlas Mountains, Morocco. A set of 157 coral specimens have been collected from a small biostrome, a giant reef and two olistholiths, spanning from Hettangian − Sinemurian time interval to early Pliensbachian. These corals are distributed in 14 families, 22 genera and 27 species. Among these species, two are new: <i>Lepidophyllia (Heterastraea) microcalix</i> sp. nov., represented enough to allow a population study and <i>Paracuifia castellum</i> sp. nov. The study extends the last appearance datum of several genera known only in the Triassic till now, namely: <i>Parastraeomorpha, Araiophyllum, Paracuifia, Pinacophyllum</i> and, possibly, <i>Paravolzeia</i> . For this reason, the severity of the end-Triassic mass extinction is questioned in comparison to the extinction events that happened around the Pliensbachian-Toarcian boundary. For this reason, moreover, the phyletic discontinuity between some Triassic and Jurassic taxa is also addressed. Some Lazarus taxa known from Triassic and Pliensbachian remain absent in Hettangian and now, at a lesser degree, in Sinemurian. That is why we assume that the absence of these taxa is only due to the poor preservation of coral environments during these times. This study also changes our view on the first appearance datum of several genera that were known in Jurassic strata, namely <i>: Proleptophyllia, Vallimeandropsis</i> and, possibly, <i>Lochmaeosmilia.</i> A special attention is given to the distribution of colonial arrangements and points to the important proportion of cerioid and solitary corals. Additionally, the study highlights the existence of significant proportions of thamnasterioid and meandroid forms. The presence of corals with such a level of integration, together with the occurrence of two species that show platy to ramose transition in their colony shape, namely <i>Hispaniastraea murciana</i> and <i>Chrondrocoenia clavellata</i> , stresses the effectiveness of a photosymbiosis in these Early Jurassic coral communities. Lastly, the proportion of solitary specimens increased over time, revealing the uniqueness of coral assemblages during the Pliensbachian.