Vertebrate microremains from the Lower Silurian of Siberia and Central Asia: palaeobiodiversity and palaeobiogeography

Abstract

Abstract. The biostratigraphic and palaeogeographical distributions of early vertebrate microfossils from a number of Lower Silurian localities in northwestern Mongolia, Tuva and southern Siberia were reviewed. Vertebrate microremains showed high taxonomic diversity, comprising acanthodians, chondrichthyans, putative galeaspids, heterostracans, mongolepids, tesakoviaspids, thelodonts and possible eriptychiids. The majority of taxa have lower stratigraphic levels of occurrence compared to other Silurian palaeobiogeographical provinces, such as the European-Russian or Canadian Arctic. Vertebrate microremains are numerous within the samples, which may indicate warm-water low-latitude palaeobasins with rich shelf faunas. This disagrees with the recent interpretations of the territory as a northern high-latitude Siberian palaeocontinent. The palaeobiogeographical distribution of vertebrate taxa indicates an endemic palaeobiogeographical province of connected epeiric palaeoseas with external isolation during the early Silurian. In previous works separation between Tuvan and Siberian palaeobiogeographical provinces has been suggested. After careful revision of the vertebrate microfossil record of the region, we find that differences in a few vertebrate taxa do not provide not strong enough evidence to reliably distinguish these provinces. We therefore dispute the hypothesis of two biogeographical provinces in the early Silurian of the Siberian palaeocontinent, and propose a single unified Siberian–Tuvan palaeobiogeographical province.

Five hundred million years of extinction and recovery: a phanerozoic survey of large‐scale diversity patterns in fishes

“…sinocanthids) in the late Llandovery (Karatajute‐Talimaa, 1995; Janvier 1996; Sansom et al. 2005; Zhao and Zhu 2007; Žigaite et al. 2011), plus isolated placoderm plates and stem‐osteichthyan dermal bone fragments in Wenlock‐age faunas in China (Zhao and Zhu 2007; Qu et al.…”

“…An alternative explanation is that early jawed gnathostomes inhabited environments that either have been little sampled by palaeontologists or are poorly represented in the stratigraphic record. However, the abundance of gnathostome microfossils, and later macrofossils, in Silurian faunas bearing corals and other well‐sampled invertebrates, and aforementioned scarcity in preservational Lagerstätten of similar age suggests that sampling is not the main issue (Janvier 1996; Zhao and Zhu 2007; Žigaite et al. 2011).…”

The systematics of the Mongolepidida (Chondrichthyes) and the Ordovician origins of the clade

“…Mongolepids were first described by Karatajūtė-Talimaa et al ( 1990 ) and Karatajūtė-Talimaa ( 1995 ) from the Chargat Formation (Upper Llandovery–Lower Wenlock) in north-western Mongolia, together with a diverse assemblage of early vertebrates including pteraspidomorphs (V Karatajūtė-Talimaa, 2013, unpublished data), thelodonts ( Žigaitė , 2013 ; Žigaitė 2004 ; Žigaitė, Karatajūtė-Talimaa & Blieck , 2011 ), acanthodians ( Karatajūtė-Talimaa & Smith , 2003 ) and elegestolepids. The first erected species, Mongolepis rozmanae , was subsequently added to with the description of Teslepis jucunda Karatajūtė-Talimaa & Novitskaya ( 1992 ) and Sodolepis lucens Karatajūtė-Talimaa & Novitskaya ( 1997 ), also from the Chargat Formation.…”

Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China)

“…The material from the Tataertag and Ymogantau Formations has extended the overlap between the Tarim and South China constituents of the Zhangjiajie Vertebrate Fauna. These data further underscore the impoverished nature of the Zhangjiajie Fauna (mongolepids, sinacanthids and galeaspids) when compared with coeval sites from Siberia and Mongolia and their complement of mongolepids, acanthodians, thelodonts, eriptychiids and heterostracans [19,59].…”