QUENSTEDTOCERAS WITH PATHOLOGY

What you are seeing here is a protuberance extruding from the venter of Quenstedtoceras cf. leachi (Sowerby). It is a pathology in the shell from hosting immature bivalves that shared the seas with these Middle Jurassic, Upper Callovian, Lamberti zone fauna from the Volga River basin. The collecting site is the now inactive Dubki commercial clay quarry and brickyard near Saratov, Russia. 

The site has produced thousands of ammonite specimens. A good 1,100 of those ended up at the Black Hills Institute of Geological Research in Hill City, South Dakota. 

Roughly 1,000 of those are Quenstedtoceras (Lamberticeras) lamberti and the other 100 are a mix of other species found in the same zone. These included Eboraciceras, Peltoceras, Kosmoceras, Grossouvria, Proriceras, Cadoceras and Rursiceras. 

What is especially interesting is the volume of specimens — 167 Quenstedtoceras (Lamberticeras) lamberti and 89 other species in the Black Hills collection — with healed predation injuries. It seems Quenstedtoceras (Lamberticeras) lamberti are the most common specimens found here and so not surprisingly the most common species found injured. Of the 1,000, 655 of the Quenstedtoceras (Lamberticeras) lamberti displayed some sort of deformation or growth on the shell or had grown in a tilted manner. 

Again, some of the Q. lamberti had small depressions in the centre likely due to a healed bite and hosting infestations of the immature bivalve Placunopsis and some Ostrea. 

The bivalves thrived on their accommodating hosts and the ammonites carried on, growing their shells right up and over their bivalve guests. This relationship led to some weird and deformities of their shells. They grow in, around, up and over nearly every surface of the shell and seem to have lived out their lives there. It must have gotten a bit unworkable for the ammonites, their shells becoming warped and unevenly weighted. Over time, both the flourishing bivalves and the ammonite shells growing up and over them produced some of the most interesting pathology specimens I have ever seen.    

In the photo here from Emil Black, you can see some of the distorted shapes of Quenstedtoceras sp. Look closely and you see a trochospiral or flattened appearance on one side while they are rounded on the other. 

All of these beauties hail from the Dubki Quarry near Saratov, Russia. The ammonites were collected in marl or clay used in brick making. The clay particles suggest a calm, deep marine environment. One of the lovely features of the preservation here is the amount of pyrite filling and replacement. It looks like these ammonites were buried in an oxygen-deficient environment. 

The ammonites were likely living higher in the water column, well above the oxygen-poor bottom. An isotopic study would be interesting to prove this hypothesis. There's certainly enough of these ammonites that have been recovered to make that possible. It's estimated that over a thousand specimens have been recovered from the site but that number is likely much higher. But these are not complete specimens. We mostly find the phragmocones and partial body chambers. Given the numbers, this may be a site documenting a mass spawning death over several years or generations.

If you fancy a read on all things cephie, consider picking up a copy of Cephalopods Present and Past: New Insights and Fresh Perspectives edited by Neil Landman and Richard Davis. Figure 16.2 is from page 348 of that publication and shows the hosting predation quite well. 

Photos: Courtesy of the deeply awesome Emil Black. These are in his personal collection that I hope to see in person one day. 

It was his sharing of the top photo and the strange anomaly that had me explore more about the fossils from Dubki and the weird and wonderful hosting relationship between ammonites and bivalves. Thank you, my friend!

CADOCHAMOUSSETIA: FROM RUSSIA WITH LOVE

From Russia with love. This lovely inflated ammonite is the female macroconch, Cadochamoussetia tschernyschewi (Sokolov, 1912) from the 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).

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. He has shared many wonderful specimen photos and stories with me over the years and I am honoured by his generosity in doing so. It is because of him that I am able to share these with all of you! So a collective, Спасибо, мой друг. Spasibo, moy drug. 

I have placed views of this lovely Cadochamoussetia tschernyschewi into a teaching tool that includes the specimen name, length and provenance.

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.