Sunday, 21 June 2020

CADOCHAMOUSSETIA OF RUSSIA

Cadochamoussetia tschernyschewi 
A lovely chunky example of the macroconch, Cadochamoussetia tschernyschewi (Sokolov, 1912) from Jurassic, Lower Callovian, Elatmae Zone, Subpatruus Subzone, Stupachenkoi Horizon, Unzha River, Makarev-Manturovo, Kostroma Region, Russia.

This beautiful — fully Бомба — specimen is courtesy of Emil Black and one of the finest in his collection. It has a chunkiness that reminds me of the Cadoceras we find in the Pacific Northwest, particularly the macroconch Cadoceras comma from the Callovian Mysterious Creek Formation near Harrison Lake in British Columbia.

In the last decade, the Siberian zonal scale of the Callovian has been considerably revised because of new ammonite collections from the Callovian reference sections in Siberia. Species of Cadoceratinae thought of as exclusively European were recorded for the first time in Siberia. 

Both these newly recovered specimens and recent studies have considerably expanded our knowledge on the taxonomic composition of genera and species of Callovian ammonites and revision of the generic classification and stratigraphic position of genera and species of the family Cardioceratidae. The proposed Lower Callovian ammonite scale largely coincides with the East European scale and correlates with the scales of East Greenland, Arctic Canada, and Alaska (Kniazev et al., 2009, 2010, 2011, 2015; Nikitenko et al., 2013).

Cadochamoussetia tschernyschewi 
Jurassic deposits crop out on the right bank of the
Anabar River between the mouths of the Srednyaya
and Sodiemykha rivers, over a length of about 24 km.

During recent fieldwork at the Middle-Upper Jurassic of the Anabar River basin, a lovely representative ammonite collection was assembled, amongst which was the Early Callovian genus Cadochamoussetia (Mitta, 1996). 

Cadochamoussetia is widespread in East European sections but these beauties were the first recorded specimen of this chunky species from the Anabar.

The genus Cadochamoussetia (Mitta, 1996) was established in European Russian (Gerasimov et al., 1996) and later in England (Navarro et al., 2005).

In the lower Callovian of European Russia, beds with Cadochamoussetia were originally considered part of the Cadochamoussetia subpatruus upper subzone of the Cadoceras elatmae Zone (Mitta, 2000). 

In 2005 and 2009, proposals were made to move these beds from subzone to zone (Gulyaev, 2005, 2009). However, the Unified Regional Stratigraphic Scheme of Jurassic Deposits of the East European Platform (2012), suggested it remained a subzone. The Anabar section contains two species of Сadochamoussetia, which were used as the basis of the Сadochamoussetia tschernyschewi Zone.

In previous papers (Kniazev et al., 2010), considered the composition of the genus Cadoceras as it was interpreted in (Treatise, 1957). Several groups of species are now recognized within the genus: Cadoceras elatmae group, including C. frearsi, C. harveyi, C. sublaeve, including species widespread in the Arctic C. tolype, C. emelianzevi, C. septentrionale, C. durum, etc. Kniazev et al. proposed assigning a group of Bathonian species Catacadoceras laptievi, C. barnstoni, C. perrarum, C. subcatastoma, and C. nageli.

Photos: Cadochamoussetia tschernyschewi (12 cm) graciously shared by the deeply awesome of Emil Black. Спасибо, мой друг. Spasibo, moy drug!

References:

The Early Callovian genus Сadochamoussetia (Ammonoidea, Cardioceratidae) in the lower reaches of the Anabar River, Northern Central Siberia; Original Russian Text © V.G. Kniazev, S.V. Meledina, A.S. Alifirov, B.L. Nikitenko, 2017, published in Stratigrafiya, Geologicheskaya Korrelyatsiya, 2017, Vol. 25, No. 4, pp. 26–41.

Kniazev, V.G., Meledina, S.V., Alifirirov, A.S., and Kutygin, R.V., The Middle Callovian stage of evlution of Siberian cardioceratids, in Sovremennye problemy izucheniya golovonogikh mollyuskov. Morfologiya, sistematika, evolyutsiya, ekologiya i biostratigrafiya. Vyp. 4 (Current Problems in Study of Cephalopods: Morphology, Systematics, Evolution, Ecology, and Biostratigraphy. Iss. 4), Moscow: Paleontol. Inst. Ross. Akad. Nauk, 2015, pp. 40–45.

Meledina, S.V, Correlation of the Bajocian and Bathonian zones in light of new paleontological data, Stratigr. Geol. Correl., 2014, vol. 22, no. 6, pp. 594–605.

Kniazev, V.G., Meledina, S.V., Alifirirov, A.S., and Kutygin, R.V., The Middle Callovian stage of evlution of Siberian cardioceratids, in Sovremennye problemy izucheniya golovonogikh mollyuskov. Morfologiya, sistematika, evolyutsiya, ekologiya i biostratigrafiya. Vyp. 

If you do not speak Russian that roughly translates to: Current Problems in Study of Cephalopods: Morphology, Systematics, Evolution, Ecology, and Biostratigraphy. Iss. 4, Moscow: Paleontol. Inst. Ross. Akad. Nauk, 2015, pp. 40–45.

Meledina, S.V, Correlation of the Bajocian and Bathonian zones in light of new paleontological data, Stratigr. Geol. Correl., 2014, vol. 22, no. 6, pp. 594–605.

Treatise on Invertebrate Paleontology. Pt. L. Mollusca 4, Cephalopoda, Ammonoidea, N.Y. Lawrence: Geol. Soc. Amer., Univ. Kansas Press, 1957, vol. 4. TSCreatorProvisualization of Enhanced Geologic Time Scale 2004 database (Vers. 6.2, 2014). http://www.tscreator. org, 2014.

Treatise on Invertebrate Paleontology. Pt. L. Mollusca 4, Cephalopoda, Ammonoidea, N.Y. Lawrence: Geol. Soc. Amer., Univ. Kansas Press, 1957, vol. 4. TSCreatorProvisualization of Enhanced Geologic Time Scale 2004 database (Vers. 6.2, 2014). http://www.tscreator. org, 2014.