Kokartus (Milner, 2000)

Skutschas, Pavel & Martin, Thomas, 2011, Cranial anatomy of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan, Zoological Journal of the Linnean Society 161 (4), pp. 816-838 : 819-821

KOKARTUS LOCALITIES AND ASSOCIATED VERTEBRATE ASSEMBLAGES

All Kokartus localities (Nichke 1, Kugart 1, and Kyzylsu 1, Fig. 1 ) are confined to the lower part of the Balabansai Svita, which is composed mostly by variegated (black, green, red) clays, shales, and claystones (for detailed geological setting see Kaznyshkin, 1988, 1990; Nesov & Fedorov, 1989; Nesov et al., 1994, 1996; Averianov, Martin & Bakirov, 2005). The Balabansai Svita has been dated as late Bathonian- Callovian based on plant assemblages and ostracods ( Burakova & Fedorov, 1989; Nesov et al., 1996). The lower part of the Balabansai Svita is composed mostly by grey to greenish deposits that were formed under a relatively humid climate ( Kaznyshkin, 1988). The red coloured deposits of the upper part of the Balabansai Svita were deposited under conditions of increasing aridity ( Kaznyshkin, 1988). The increasing aridity of the climate in Central Asia began in the Callovian ( Vakhrameev, 1991) and the Callovian age of the upper part of the Balabansai Svita was corroborated by this palaeoclimatic evidence, which is clearly expressed in the rocks of this unit ( Nesov & Fedorov, 1989). The lower part of the Balabansai Svita outcrops in the Kugart River Basin has been dated as Bathonian ( Burakova & Fedorov, 1989; Nesov & Fedorov, 1989) and was deposited partly in shallow water and partly under terrestrial conditions with soil horizons and plant roots ( Nesov et al., 1994). Vertebrate assemblages in the Kokartus localities indicate a freshwater rather than an estuarine environment.

Apart from Kokartus , the Nichke 1 locality has produced disarticulated remains of actinopterygian fishes, such as scales of Ptycholepididae indet., Coccolepididae indet., Pholidophoridae indet., Holostei indet., and isolated teeth of?Ichthyodectiformes indet. In addition, remains of conchostracans, ostracods, and indeterminate malacostracans have been found in this locality ( Nesov et al., 1996).

The Kugart 1 and Kyzylsu 1 localities have yielded similar vertebrate assemblages, which (besides Kokartus ) include hybodont sharks ( Polyacrodontidae indet), actinopterygian fishes (Holostei indet.), brachyopoid temnospondyls, turtles, and a poorly preserved molar of a possible docodont mammal ( Nesov et al., 1994, 1996; Averianov et al., 2008). The presence of sharks of the family Polyacrodontidae does not necessarily indicate an estuarine environment, as was suggested by Nesov et al. (1994), because hybodont sharks are known from different Asian localities that were formed under freshwater conditions ( Cuny, Suteethorn & Kamha, 2005).

The Kugart 1 and Kyzylsu 1 vertebrate assemblages contain remains of both non-lissamphibian temnospondyls and salamanders ( Averianov et al., 2008). The co-occurrence of salamanders and nonlissamphibian temnospondyls is very rare and is known only from two other Jurassic vertebrate assemblages: the Bathonian fauna of the Peski Quarry near Moscow, Russia ( Shishkin, 2000a; Alekseev et al., 2001; Gambaryan & Averianov, 2001) and the Oxfordian Qigu Formation in the southern Junggar Basin, China ( Skutschas, Martin & Ge, 2009).

Figures

Figure 1. Geographical position of the Kokartus localities (Kyzylsu 1; Kugart 1; Nichke 1) in the Kugart River Basin (asterisk) in the eastern part of the Fergana Depression (the upper map is redrawn from Averianov et al. 2005 and the lower map is modified from http://maps.google.ru/maps).