First evidence of Lower–?Middle Ordovician (Floian–?Dapingian) brachiopods from the Peruvian Altiplano and their paleogeographical significance

Abstract

AbstractThe lower strata of the Umachiri Formation from the Altiplano of southeast Peru have yielded a brachiopod-dominated assemblage, containing representatives of the brachiopod superfamilies Polytoechioidea, Orthoidea, and Porambonitoidea, as well as subsidiary trilobite and echinoderm remains. Two new polytoechioid genera and species,Enriquetoechia umachiriensisnew genus new species andAltiplanotoechia hodginin. gen. n. sp. Colmenar in Colmenar and Hodgin, 2020, and one new species,Pomatotrema laubacherin. sp., are described. The presence ofPomatotremain the Peruvian Altiplano represents the occurrence at highest paleolatitude of this genus, normally restricted to low-latitude successions from Laurentia and South China. Other polytoechioids belonging toTritoechia(Tritoechia) andTritoechia(Parvitritoechia) also occur. Identified species of orthoids from the generaParalenorthis,Mollesella, andPanderina? occur in the Peruvian Cordillera Oriental and in the Argentinian Famatina Range. The only porambonitoid represented is closely related toRugostrophia latireticulataNeuman, 1976 from New World Island, interpreted as peri-Laurentian. These brachiopod occurrences indicate a strong biogeographic affinity of the Peruvian Altiplano with the Famatina and western Puna regions, suggesting that the brachiopod faunas of the Peruvian Altiplano, Famatina, and western Puna belonged to a well-differentiated biogeographical subprovince during the Early–Middle Ordovician on the margin of southwestern Gondwana. Links with peri-Laurentian and other low-latitude terranes could be explained by island hopping and/or continuous island arcs, which might facilitate brachiopod larvae dispersal from the Peruvian Altiplano to those terranes across the Iapetus Ocean. Brachiopods from the lower part of the Umachiri Formation indicate a Floian–?Dapingian age, becoming the oldest Ordovician fossils of the Peruvian Altiplano.UUID:http://zoobank.org/9670a000-260d-4d75-9261-110854c7afb8