Rising above the modern town of Nurata, in Navoiy Province, eastern Uzbekistan is the ancient fortress of Alexander the Great, built as part of Alexander's campaigns to subjugate the Persian‐speaking Sogdian peoples that lived in this province of the Persian Empire in the 4th Century bc. Alexander passed this way in 327 bc, marching his ancient army through this beautiful but desolate landscape, and conquering all before him. His fortress was built in a strategic place at the boundary between fertile agricultural lands and a dry and uncompromising vastness of steppe that lies to the east. From Nurata, about one hour drive by car along a road that cuts eastwards across the desert, is the sleepy town of Jo'sh. In the mountains beyond Jo'sh sits the hamlet of Kanda, a few mud‐brick houses nestling at the head of a small valley where a spring emerges miraculously from a bone‐dry landscape. Hereabouts are telltale signs of ancient marine deposits yielding graptolites from rocks of the Silurian system. And in these rocks are the fossils of tiny arthropods that mark a fundamental shift in the marine arthropod zooplankton 425 million years ago. It is these fossils that we have chased halfway across the world to the steppe of Central Asia.
The region of Kyrgyzstan, Tajikistan and Uzbekistan includes five first-order tectonic units with an Early Palaeozsoic sedimentary record, comprising North Tien Shan, Karatau Naryn, Turkestan - Alai, Zeravshan - Hissar and the Central Pamirs. Available palaeobiogeographical and palaeomagnetic data suggest that these were widely dispersed in the Ordovician. North Tien Shan, Karatau Naryn, Turkestan - Alai were separate microcontinents located in the low southern latitudes throughout the Ordovician in relative proximity to the western Gondwana margin. Zeravshan - Hissar and the Central Pamirs were also parts of the Gondwana supercontinent but were located in temperate latitudes. The geological literature on the Ordovician of the region is assessed to provide an updated palaeontological record, outline of lithostratigraphy, and biostratigraphic correlation based on the International Chronostratigraphical Chart. The Ordovician biostratigraphy of Central Asia is mainly graptolite-based; however, that record is discontinuous and the absence of detailed faunal logs and lack of monographic studies causes difficulty in precisely locating system and stage boundaries. Although an extensive faunal record has been documented, often it is based on preliminary taxonomical identifications which are not reliable for high-resolution biostratigraphy and tracing biodiversity patterns.
Four species of myodocope ostracod are documented from the Silurian Ludlow Series of the Aburtkan gorge on the southern slope of Dzhalpak Mountain, Uzbekistan: namely, Parabolbozoe bohemica (Barrande, 1872), Bolbozoe anomala Barrande, 1872, Silurocypridina calva Perrier, Vannier and Siveter, 2011 and Richteria migrans (Barrande, 1872). These species have a palaeogeographically widespread trans-oceanic distribution, which supports the notion that Silurian myodocopes signify the earliest zooplanktonic ostracods. Richteria migrans (Barrande, 1872), in particular, provides a precise intercontinental biostratigraphic marker that identifies rocks of the upper Gorstian to upper Ludfordian stages.
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