Crussoliceras ammonites ID

[RuMert]

I once stumbled on a group of small kimmeridgian ammos which were all later IDed as Crussoliceras spp. The genus is very rare and poorly known here. Do you have any suggestions about species? Thanks

@Ludwigia

 

 

 

 

Edited July 8, 2021 by RuMert

[FossilDAWG]

Sorry I can't help with the ID, but those are beautiful!

Don

[Tidgy's Dad]

Yeah, can't help but lovely specimens. 

[piranha]

The following papers have numerous figured specimens of Crussoliceras:  

 

Rogov, M.A., Wierzbowski, A., Shchepetova, E. 2017

Ammonite Assemblages in the Lower to Upper Kimmeridgian Boundary Interval (Cymodoce to Mutabilis Zones) of Tatarstan (Central European Russia) and their Correlation Importance. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 285(2):161-185  PDF LINK

 

Rogov, M.A. 2017

Ammonites and Infrazonal Stratigraphy of the Kimmeridgian and Volgian Stages of Southern Part of the Moscow Syneclise.
Transactions of the Geological Institute, 615:7-160  PDF LINK

[Ludwigia]

Do you know where they are from? Divisum zone?

[RuMert]

7 hours ago, piranha said:

The following papers have numerous figured specimens of Crussoliceras

4 hours ago, Ludwigia said:

Do you know where they are from? Divisum zone?

Thanks, I've seen them and talked to Prof. Rogov. Unfortunately this genus is understudied and usually not present in our deposits (boreal and subboreal). The Divisum zone doesn't exist here, instead there are Cymodoce-Mutabilis-Autissiodorensis. But due to the migration ammonites from the Divisum zone were also present for a short time (see below). In an extensive study Rogov and others mention two species: C. atavum and C.Lacertosum. Probably both are here. The location is close to those described in the paper, but the preservation is somewhat different. Abstracts from the paper to spare your time:

 

"This assemblage consists mostly of the Submediterranean representatives of the genus Crussoliceras – C. atavum (Schneid) [M] and C. lacertosum (Fontannes) [m], representing possibly a dimorphic pair. The occurrence of these forms in the described ammonite succession is indicative of the Divisum Zone of the Submediterranean zonal scheme; and the occurrence of C. atavum suggests additionally the upper part of this zone (e.g., Schick 2004)"

 

"numerous Submediterranean Crussoliceras occurrences were discovered in the upper part of the Cymodoce Zone of the whole area, whereas younger assemblages yielded Boreal Amoebites and/ or Subboreal Rasenioides followed by Aulacostephanoides with some addition of Aspidoceras and Orthaspidoceras above. Mass immigration of the Submediterranean ammonites Crussoliceras into the Subboreal Russian Sea resulted in their short-time dominance over a wide area. This “Crussoliceras event”, which is well-recognized in Submediterranean areas, as well as the subsequent expansion of Zenostephanus, both correspond to a sea-level high-stand, which resulted in faunal mixing of ammonites indicative of different bioprovinces. They provide key correlative levels which can be recognized around the Lower/Upper Kimmeridgian boundary, especially in the ecotone area of the Russian Sea"

 

"The most carefully studied was a specimen from locality T1 – member 1 (0.35 m above the base; Fig. 6A). It attains about 270 mm in diameter; the coiling is evolute (at D = 210 mm, Wh = 28; Ud = 54); the ribbing is fairly dense on the inner whorls and consists of numerous, prominent, almost rectiradiate primary ribs which are regularly bifurcated; PR equals 40 at D = 90 mm, and 43 at D between 120-160 mm, and markedly decreases thereafter, attaining about 35 at D = 200 mm. The ribs on the outer whorl are swollen, initially branched high on the whorl side into three secondaries, then becoming simple. The specimen shows marked similarities to the type specimens of Crussoliceras atavum (Schneid) as illustrated and described by Schneid (1915: 94-95, pl. 2, fig. 2; pl. 9, fig. 1) which corresponds strictly to Ammonites divisum coronatus of Quenstedt (1888, pl. 106, figs. 6-8), a very characteristic species showing the dense biplicate ribs on the inner whorls, and the polygyrate and single ribs on the outer whorl with a coronate whorl section (see Geyer 1961; Schick 2004)"

[Ludwigia]

Yes, I've just studied Rogov's papers and am familiar with all that you have written, so as you will understand, it's difficult to make comparisons, since my samples from the Danube Valley  are all Submediterranean and belong to other species than those mentioned by Rogov. C. atavum can however be found in a somewhat younger horizon at the quarry in Geisingen and it is comparable to those which you are showing. As far as I know, C. lacertosum has not been found in this area.

[RuMert]

Thanks for the info