| Aasta | 1997 |
|---|---|
| Ajakiri | Modern Geology |
| Köide | 21 |
| Number | 1/2 |
| Leheküljed | 1-15 |
| Tüüp | artikkel ajakirjas |
| Keel | inglise |
| Id | 1787 |
Abstrakt
The taxonomy of loganiid thelodonts is specified. Three new genera are established. Sandivia gen. nov. from the Late Ordovician of the Timan-Pechora Province is the most ancient thelodont genus known to date. The genus Angaralepis gen. nov. is based on Logania moskalenkoae Karatajūtė-Talimaa 1978 from the Middle Llandovery the Siberian Platform. The body scales of the genera Sandivia and Angaralepis are characterised by peculiar morphology, with a posterior anchor-like section of crown and a base which is very low or absent. The genus "Logania", established by W. Gross in 1967, is subdivided into two genera: Loganellia Turner 1991 and Paralogania gen. nov. To the genus Loganellia are ascribed all species in which the crown of body scales is compact and consists of a central length-wise section and entire longitudinal ribs (up to 3 pairs). The 'break-up' (dispersion) of longitudinal ribs of crowns in longitudinal rows of thornlets (spines) is characteristic for body scales of the new genus Paralogania.