Plus ammonites dans le sud de l'Espagne

[phylloceras]

Bonjour.

Je demande de l'aide pour ces ammonites que je ne peux pas classer correctement. La première ammonite appartient à la partie supérieure du Tithonien inférieur, on me dit que peut-être un Sutneria sp. mais je ne suis pas clair. La seconde appartient certainement au sommet de la Tithonien supérieur, je pense que c'est une Neocomitidae mais ne peux pas trouver dans le travail que j'ai sur le Tithonien. Le troisième est aussi de la partie supérieure du Tithonien supérieur, et je pense qu'il appartient à la famille Himalayitidae. Le quatrième, je pense peut appartenir à Jurassique supérieur, mais inconnu à l'étage. Et le dernier, appartenant peut-être à la base du Barrémien inférieur, ou le haut de l'Hauterivien supérieur, Je doute entre Acrioceras tabarelli et Acrioceras meriani. Il mesure 90 mm​​.

Merci à l'avance

1

2

3

4

5

[Berriasien]

1- Probably, a Simocosmoceras sp.

2- Himalayitidae indet., i personally found similar specimens in the upper part of the Tithonian in Southeast France. I currently work on them.

3- This specimen is a gracile morphotype of Protacanthodiscus andreaei

4- We need a ventral view, but i don't think it is a Tithonian form.

5- The trituberculation is only well-marked on the coil, but it exists several bullae on the bend which are not observed in "true" A. meriani, and the growth is more acrioceratic. This specimen is called by Thomel (1990) Acrioceras cf. meriani.

[phylloceras]

Thank you very much.

I see you have much control over Tithonian and Lower Cretaceous ammonites.

The first does not appear in the thesis of Federico Oloriz (Kimmeridgian-Lower Tithonian), but I just saw an article in a Simocosmoceras very similar to my specimen. On the same level I found many Burckhardticeras peroni, Simoceras (Lytogyroceras) subbeticum, Phylloceras saxonicum, Haploceras indet. and other simoceratidae and perisphinctidae. With the second I was wrong then, I was convinced it was a Neocomitidae. The third had also thought Protacanthodiscus but clueless me shallow navel. Nearby I found a Protacanthodiscus I have classified as P. darwini of Durangites zone. The fourth is not mine but I'll try to get a ventral view. In the area where I was found I think is the Upper Jurassic, but I will try to get more information. And the last I'll change the classification to Acrioceras cf. meriani.

That said, thank you very much.

I put a photo of another Protacanthodiscus, I have classified as P. darwini but without much security.

[phylloceras]

Indeed, in the second photo of the second ammonite, corresponds to the left. The ammonite is right is a Himalayites sp.

And this other specimen, it could also be classified as Simocosmoceras sp.?

[Crio]

For the n°5, in true A. meriani trituberculation can only be seen in the initial part of coil, and effectively the form is more aspinoceratic. I think that this one is a lower Barremian form, close to A. tabarelli. Tuberculation on the shaft is difficult to see, maybe due to the preservation...

[Berriasien]

- In my point of vue, Protacanthodiscus darwini is a robust morphotype of the higly variable Protacacanthodiscus andreaei species. In a comteporaneous population, i already collected all the transient forms.

-I think it is also an another specimen of Simocosmoceras. But this determination needs other confirmation, because my Lower Tithonian knowledged is very limited.

- In any case, the exact determination between true A. meriani or A. tabarelli is a subjective systematic choice. A continuous chain can also be collected between the Upper Hauterivian and lowermost Barremian. For me, the acrioceratic-like form is more closely related to A. tabarelli. But as i said, Thomel preferentially used cf. meriani.

[phylloceras]

Ok, a specialist in the Lower Cretaceous ammonites classified it as A. Tabarelli by the presence of some nodules on the bend, while a paleontologist I know (Miguel Company) classified it as A. Meriani. So doubted between these two species.

Thank you both for the help

[Crio]

Ok, a specialist in the Lower Cretaceous ammonites classified it as A. Tabarelli by the presence of some nodules on the bend

In this case, this specimen effectively probably belong to A. tabarelli.

In my opinion, the distinction between tabarelli and meriani is not so subjective : their morphology are recognizable (aspinoceratid vs acrioceratid coiling, very feeble tuberculation in meriani) and they have different stratigraphic positions : upper Hauterivien, Baleare zone for meriani, and lower Barremian, mainly Hugii and Nicklesi zones for tabarelli. Maybe that some transitional forms exist in the uppermost Hauterivian...

For the specimen called Acrioceras cf. meriani by Thomel (1990), it is a little strange interpretation, this specimen is really different of the lectotyp of the specie...

[phylloceras]

Thank you again. Unfortunately I didn't find it in situ, but I found very near some specimens of Taveraidiscus hugii, Avramidiscus kiliani and a fragment of Emericiceras of the group emerici / thiollierei, this fauna appears if I am not mistaken in Hugii zone, so the Acrioceras could belong to this zone.