Portal de Periódicos da CAPES

A mid-Ordovician brachiopod evolutionary hotspot in southern Kazakhstan

2021; Wiley; Linguagem: Inglês

10.1002/9781119782377.ch1

2637-6032

Leonid E. Popov, L. Robin M. Cocks,

Geological Studies and Exploration

Chu-Ili, now in Kazakhstan, was a substantial independent equatorial microcontinental terrane in Ordovician times, with a small Precambrian core fringed by several island arcs. Its mid-Ordovician (late Darriwilian to early Katian) faunas were a major evolutionary hotspot within an equatorial archipelago at a period when Palaeozoic sea levels and temperatures were at their highest. As well as reviewing the previously described brachiopods from elsewhere in Chu-Ili, the mid-Ordovician brachiopods of the West Balkhash Region, which outcrops west of Lake Balkhash within Chu-Ili, are newly described here, mainly from the Berkutsyur and Baigara formations. Many represent the earliest occurrence of their lineages, notably the oldest member of the Order Atrypida. More than twelve brachiopod associations are defined, many for the first time and together hosting 73 genera and over 91 species. The new family Kellerellidae is erected within the superfamily Lissatrypoidea. New genera are Aploobolus (Obolidae), Doughlatomena (Rafinesquinidae), and Altynorthis , Lictorthis , and Baitalorthis (all Plectorthidae), Baitalorhynchus (Sphenotretidae), Lydirhyncha (Ancistrorhynchidae) and Costistriispira (Kellerellidae). Eleven new species, including Aploobolus ? tenuis , Doughlatomena splendens , Bimuria karatalensis , Apatomorpha akbakaiensis , Lepidomena betpakdalenis , Sonculina baigarensis , Altynorthis betpakdalensis , Altynorthis vinogradovae , Phaceloorthis ? corrugata , Batailorhyncha rectimarginata and Costistriispira proavia , and one new subspecies Sowerbyella ( Sowerbyella ) verecunda baigarensis are also erected. The global palaeogeographical affinities of all the Chu-Ili brachiopod faunas are discussed, as well as Chu-Ili's place within the peri-Gondwanan archipelago. Newly named stratigraphical units are the Berkutsyur (Darriwilian to early Sandbian) and overlying Kopkurgan (Sandbian to Katian) formations within West Balkhash, and the Tastau (Darriwilian) and Takyrsu (Darriwilian to early Sandbian) formations within the northern Betpak-Dala desert.