Perisphinctes?

[Ramon]

This fossil is an Ammonite which I think is Perisphinctes. This fossil came from the santiago formation in San Luis Potosi, Mexico, which is middle Oxfordian.The sanTiago formation is below the Taman formation which is were the Ochetoceras came from. There has been fossil coming out of the formation which are Perisphinctes (Middle Oxfordian ammonite biostratigraphy of the Lower Santiago Formation at Taman, San Luis Potosi, Mexico — with notes on Mexico–Caribbean ochetoceratins) or Bioestratigrafía de amonitas del Oxfordiano medio de la parte basal de la Formación Santiago en Tamán, San Luis Potosí, México – con notas sobre ochetoceratinos de México y el Caribe, in Spanish. 

 

Here's photos of my specimen 

 

 

Close up of the fossil

 

 

[Pemphix]

Maybe Ludwigia can help - he knows good about ammonites.

But i am afraid it will be difficult to tell because it's poorly preserved and the photo seems somehow a little blurry, too.

 

Best regards,

Pemphix

[ynot]

@Ludwigia

[abyssunder]

Sure could be a Perisphinctes sp., although is hard to tell because of his preservation status. According to the cited reference Olóriz, Federico; Villaseñor, Ana B.; López-Palomino, Isabel. 2008. Middle Oxfordian ammonite biostratigraphy of the Lower Santiago Formation at Tamán, San Luis Potosí, Mexico — with notes on Mexico-Caribbean ochetoceratins. Revista Mexicana de Ciencias Geológicas, vol. 25, núm. 2, pp. 261-283. there are a few species described from the Santiago Formation, as shown in this excerpt :

 

[Ludwigia]

I agree with our Romanian friend. It appears to be a Perisphinctes, but in my opinion the preservation isn't good enough to be able to determine the species. You'd need to know the exact horizon in order to even make a guess, since there are a large number of species belonging to this genus to choose from. Just call it Perisphinctes sp. It's really not necessary to give everything a species name.

[FossilDAWG]

I thought that in Perisphinctes the ribs bifurcated or trifurcated about mid-flank.  I don't see any evidence for that, even despite the poor preservation of the specimen.  

 

Don

[abyssunder]

6 hours ago, Ludwigia said:

... You'd need to know the exact horizon in order to even make a guess, since there are a large number of species belonging to this genus to choose from.

That's the reason I've put the stratigraphical section in front of the request. Sometimes, the specimens considered as 'type' specimens are in a worst preservation than the ulterior ones discovered by others (not in all cases). I could see the bifurcated character of the ornamenting ribs in some of the regions of the outer whorl, although the whole ammonite is strongly weathered, unfortunately. , but it is an interesting one.

[Ludwigia]

13 hours ago, FossilDAWG said:

I thought that in Perisphinctes the ribs bifurcated or trifurcated about mid-flank.  I don't see any evidence for that, even despite the poor preservation of the specimen.  

 

Don

 

They mostly bifurcate just slightly below the venter which is why the forks are usually not visible on the inner whorls. This specimen is so weathered or damaged that the bifurcation on the outer whorls also isn't clearly visible, but in my opinion it shows enough traits to at least merit an educated guess.

[FossilDAWG]

Thanks Roger.  You're the "go-to" person for Jurassic ammonites so I'll defer to your judgement.

 

Don

[Ramon]

My fossil looks like (h) in the following photo. It is labeled as, Perisphinctes (Otophinctes) paturattensis. The name of the article is 

"Middle Oxfordian ammonite biostratigraphy of the Lower Santiago Formation at Taman, San Luis Potosi, Mexico — with notes on Mexico–Caribbean ochetoceratins". 

 

Edited January 14, 2017 by Ramon