Skip to main content
    • Aa
    • Aa

Endemic thelodonts (Vertebrata: Thelodonti) from the Lower Silurian of central Asia and southern Siberia

  • Živilė Žigaitė (a1) (a2)

New fossil vertebrate microremains from the Lower Silurian of NW Mongolia, Tuva and S Siberia have been discovered, and previous collections of thelodonts (Vertebrata: Thelodonti) from this region re-studied, figured and described, following recent advances in morphology and systematics of thelodont scales. As a result, six thelodont species are described here and attributed to two families and three genera. An emended diagnosis is given for each species. Morpohological scale varieties of each species are revised, and the squamation types are introduced to the species descriptions, resulting in newly grouped morphological sets of scales. The previously monotypic genus Talimaalepis Žigaitė, 2004, is proposed to contain two different species; therefore, two new combinations of morphological scale sets of two species are described for the first time. Both of them show transitional scale structure between the genera Loganellia (family Loganellidae) and Helenolepis (family Phlebolepididae). Two of the thelodont genera, Angaralepis and Talimaalepis, as well as all the six species, are endemic and not known anywhere else in the world. They are accompanied by a variety of other peculiar early vertebrates, such as mongolepids, two endemic genera of acanthodians, and putative galeaspids. This work enhances our knowledge of early Silurian vertebrate diversity, and provides evidence of regional palaeoenvironmental conditions and palaeogeographical relationships of the Siberia and Tuva terranes.

Hide All
O. Afanassieva & P. Janvier 1985. Tannuaspis, Tuvaspis and Ilemoraspis, endemic osteostracan genera from the Silurian and Devonian of Tuva and Khakassia (USSR). Geobios 18(4), 493506.

L. R. M. Cocks & T. H. Torsvik 2002. Earth geography from 500 to 400 million years ago: a faunal and palaeomagnetic review. Journal of the Geological Society 159(6), 631–44.

L. R. M. Cocks & T. H. Torsvik 2007. Siberia, the wandering northern terrane, and its changing geography through the Palaeozoic. Earth-Science Reviews 82, 2974.

D. Fredholm 1990. Agnathan vertebrates in the Lower Silurian of Gotland. Geologiska Foreningens i Stockholm Forhandlingar 112, 6184.

V. Hairapetian , H. Blom & G. C. Miller 2008. Silurian thelodonts from the Niur Formation, central Iran. Acta Palaeontologica Polonica 53(1), 8595.

V. N. Karatajūtė-Talimaa & M. M. Smith 2003. Early acanthodians from the Lower Silurian of Asia. Transactions of the Royal Society of Edinburgh: Earth Sciences 93(for 2002), 277–99.

T. Märss 1986. Squamation of the thelodont agnathan Phlebolepis. Journal of Vertebrate Paleontology 6(1), 111.

T. Märss & C. G. Miller 2004. Thelodonts and distribution of associated conodonts from the Llandovery-lowermost Lochkovian of the Welsh Borderland. Palaeontology 47(5), 1211–66.

T. Märss & A. Ritchie 1998. Articulated thelodonts (Agnatha) of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 88(for 1997), 143–95.

R. S. Sansom 2009. Endemicity and palaeobiogeography of the Osteostraci and Galeaspida: a test of scenarios of gnathostome evolution. Palaeontology 52(6), 1257–73.

H. C. Stetson 1931. Studies on the morphology of the Heterostraci. Journal of Geology 39, 141–54.

Ž. Žigaitė , V. N. Karatajūtė-Talimaa & A. Blieck 2011. Vertebrate microremains from the Lower Silurian of Siberia and Central Asia: palaeobiodiversity and palaeobiogeography. Journal of Micropalaeontology 30, 97106.

Ž. Žigaitė & A. Blieck 2006. Palaeobiogeographical significance of Early Silurian thelodonts from central Asia and S Siberia. GFF 128, 203–06.

Ž. Žigaitė & D. Goujet 2012. New observations on the squamation patterns of articulated exoskeletons of Loganellia scotica (Vertebrata: Thelodonti) from the Lower Silurian of Scotland. Geodiversitas 34(2), 253–70.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Earth and Environmental Science Transactions of The Royal Society of Edinburgh
  • ISSN: 1755-6910
  • EISSN: 1755-6929
  • URL: /core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh
Please enter your name
Please enter a valid email address
Who would you like to send this to? *



Full text views

Total number of HTML views: 4
Total number of PDF views: 4 *
Loading metrics...

Abstract views

Total abstract views: 85 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 17th October 2017. This data will be updated every 24 hours.