Late Ordovician brachiopods from Peru and their palaeobiogeographical relationships

Abstract

A Sandbian brachiopod association from the Calapuja Formation, in the Peruvian Altiplano, north‐west of Lake Titicaca, has allowed a re‐examination of the palaeobiogeographical relationships between Gondwana and Avalonia during the Late Ordovician, when the palaeocontinents are considered to be already very distant from one another. The brachiopod fauna includes the new species Onnizetina calapujensis sp. nov., Horderleyella chacaltanai sp. nov., Drabovinella minuscula sp. nov. and Tasmanella curtiseptata sp. nov., as well as Caeroplecia sp., Dinorthis cf. flabellulum and Tunariorthis cardocanalis. In addition, Colaptomena expansa expansa and Heterorthis retrorsistria, known from the British Burrellian Stage of the Caradoc Series (late Sandbian) in Wales and the Welsh Borderlands, have also been identified. The brachiopod collection is the most diverse known from a single locality in the whole Central Andean Basin. Within it, forms with clear Gondwanan links occur, such as the new species of Onnizetina, Drabovinella and Horderleyella, and typical representatives of the Avalonian faunas, such as the Welsh Colaptomena expansa expansa and Heterorthis retrorsistria. The brachiopod species exchange between the Proto‐Andean margin of Gondwana and Avalonia, now believed to be possible during the late Sandbian, allows a reconsideration of the global taxonomic affinities of both regions. With this in mind, detrended correspondence analysis (DCA) and cluster analysis have been applied to an updated rhynchonelliformean brachiopod matrix consisting of presence/absence data. The scatter plot resulting from the DCA allows a vivid visualization of the grouping and geographical trends of the South American localities with respect to Avalonia–Baltica and the Mediterranean margin of Gondwana during the Sandbian. Our results agree with previous palaeogeographical reconstructions, depicting Avalonia very close to Baltica and already distant from Gondwana. As a few brachiopod species, with low dispersal potential, would have been able to migrate between those distant palaeocontinents, the existence of intermediate islands in the Rheic Ocean, permitting the transit by island hopping of eurythermal species, must be considered.

New Late Ordovician cornulitids from Peru

“…Peru) was situated at intermediate latitude during the early Late Ordovician (Villas et al 2015). Avalonia and Baltica were located at a similar latitude in the Sandbian, and several "Celtic" brachiopod species have been identified recently in the typically Gondwanan assemblage of the Calapuja Formation (Villas et al 2015). Thus, it is interesting that the cornulitids from the Sandbian of Peru are different from those known from the Sandbian of Baltica (Vinn 2013) and the Late Ordovician of Avalonia (Schlotheim 1820, Murchison 1839 …”

“…The Proto-Andean Margin of Gondwana (i.e. Peru) was situated at intermediate latitude during the early Late Ordovician (Villas et al 2015). Avalonia and Baltica were located at a similar latitude in the Sandbian, and several "Celtic" brachiopod species have been identified recently in the typically Gondwanan assemblage of the Calapuja Formation (Villas et al 2015).…”

“…1). From the southern Calapuja inlier, the Totoracancha-Tilcara section provided abundant specimens, all coming from bed C3 of Villas et al (2015, figs 1 and 2), and two more from correlative strata occurring at the "Queñuane-west" section near the Queñuane ranch, ca 4 km south of Calapuja. From the Ayaviri inlier, several specimens were collected at the fossil locality "Punco creek" of Laubacher (1977, p. 38).…”

“…The Calapuja Formation sensu stricto, as revised by Klink et al (1986) and Palacios et al (1993), is a marine shale-sandstone succession with a maximum thickness of 4000 m. The base and the exact age of the formation are unknown, being usually equated with the Upper Ordovician. Several fossiliferous assemblages occurring in the lower third of the Calapuja Formation have been recently reviewed by Villas et al (2015) and placed in the upper Sandbian. North of the Ayaviri Fault, the outcrops of what was also considered to be Calapuja Formation near Ayaviri (Laubacher 1977(Laubacher , 1978 were recently reinterpreted as the western prolongation of the Sandia Formation of the Eastern Cordillera (Díaz-Martínez et al 2001).…”

“…-Totoracancha Villas et al 2015, fig. 1.B1), ca 2.5 km west of the town of Calapuja, Department of Puno, Peru: lat.…”