Campanian flint Ammonite from Israel, Help nedded

[ozrit]

Hi all,

This is from the central Negev area in Israe. About 30mm in diameter.

If needed I can upload more photos from different angles.

Many thanks,

Oz

 

[Fossildude19]

Pictures of the keel and of the opening might be helpful.

 

[ozrit]

I will take the photos and upload by Monday (hopefully on Sunday). Thank you!

Regards,

Oz

[abyssunder]

I think I have something for you, although, as Tim said, " pictures of the keel and of the opening might be helpful ".

 

 

" Level 2 is a phosphate bed (No. 0) at the base of the Phosphate Member of the Mishash Formation, overlying the Chert Member (Fig. 2). The upper part of the Chert Member in central and southern Israel consists of brecciated chert, exhibiting in places an irregular upper surface bored by bivalves (before silicification) and overlain by a conglomerate of chert pebbles cemented by phosphate (Lewy 1985). Thus the phosphate bed (No. 0) above the Chert Member represents shallow marine, high-energy conditions at the beginning of a relative sea- level rise. This phosphate layer was sampled 12 kms southwest of the Oron phosphate plant (Fig. 1; Israel grid coord. 1427/0268). (...)

 

Level 2 (Phosphate Bed No. 0) contains many Squalicorax pristodontus of small and medium size, whereas large Cretolamna teeth are missing. Although this assemblage can be easily distinguished from that of the other levels it does not contain age-indicative elements. Its Late Campanian age is indicated in other regions where the last Hoplitoplacenticeras marroti (Coquand) occurs just below this phosphate bed so that this level is of the same age as the lower Bostrychoceras polyplocum Zone of Europe. " - Lewy, Z., Cappetta, H. 1989. Senonian Elasmobranch teeth from Israel. Biostratigraphic and paleoenvironmental implications.  N. Jb. Geol. Palaont. Mh. (4): 212-222

 

Considering the above, this could be a preliminary or possibly assignment of the ammonite in question to the genus Hoplitoplacenticeras, maybe Hoplitoplacenticeras marroti (Coquand).

 

 

links: 1 and 2

 

 

[ozrit]

Thats great. I have a work from 1947 (Campanian of Mount Olives) and the author mentioned this species.

A few meters from the ammonite I have found another specimen which was covered in a hard layer which I can't remove. The details however 

are very persuasive towards H.marroti, so the flint specimen a good candidate to be representing the same species. Both are of about the same size also.

I will take good photos tomorrow at my office from the angles you mentioned and post here.

Thank you very much

[ozrit]

and here it is...

[abyssunder]

Whow, great work! Excellent images of a very nice specimen. It could be used as reference.

 

The more I look the more I'm convinced that it has a good resemblence with Hoplitoplacenticeras/H. marroti Coquand (= H. vari Schlüter) - Hoplitoplacenticeras howarthi Collignon; Klinger & Kennedy, considering also the possible dimorphism and intraspecific variation.

 

" As is the case in the family Placenticeratidae in general, (see e.g. Klinger & Kennedy 1989), but specifically in the genus Hoplitoplacenticeras, the material is extremely variable, both in terms of strength and density of lateral ornament and relative proportions of the shell. This is further complicated by the extreme changes in ornament in the transition from the phragmocone to the body chamber, as well as the effects of dimorphism. " (...)

Variation
In our material, extreme forms in ornament, size and whorl section in the later part of the phragmocone can be distinguished, but these features overlap to such an extent that they have to be considered as part of the intraspecific variation. (...)

Dimorphism
In discussions on the family Placenticeratidae, and specifically the genus Hoplitoplacenticeras several references have been made to dimorphism. The earliest reference to the presence of possible dimorphism in the genus was already made by Paulcke (1907 p. 52[218] in his discussion of H. (H.) plasticus. He suggested that the crassus-types, i.e. the inflated forms were females (macroconchs) and the compressed laevis-forms, male (i.e. microconchs). Subsequent references to dimorphism made mainly on differences in size (in Hoplitoplacenticeras) are found in e.g. Kennedy & Wright (1983, p. 868); Kennedy 1986, p. 63); Klinger & Kennedy (1989); Cobban & Kennedy (1993, p. 73); Kaplan et al. 1996) and Kaplan et al. (2005)
 We suggest that compressed forms mature at smaller diameters than forms with quadrate whorl sections, and are consequently tentatively referred to as micro- and macroconchs respectively. (...)

We suspect that all these ‘species’ fall within the variation of H. (H.) howarthi (see Klinger & Kennedy 1989, p. 360).
H. marrotti, H. cf. costulosum and H. besairiei of Collignon can be compared with the KwaZulu specimens with a compressed whorl section;
H. cf. dolbergense, H. trangahyense and H. antokazoense of Collignon correspond to the specimens with a quadrate whorl section, whereas the remaining Madagascan ‘species’ can be referred to those specimens with ‘intermediate’, slightly rounded whorl sections. As first revising authors, we choose the name H. (H.) howarthi Collignon for this variable Afro-Malagassy species. (...)

 

H. (H.) marroti (Coquand, 1859) (see Kennedy 1986, p. 70, pl. 2, figs 3–4; pl. 9, figs 1–8, 11–12; pl. 10, figs 1–12; pl. 12, figs 1–2) (here Fig. 15) has similar, though apparently denser lateral ornament than H. (H.) howarthi and differences between the two species are difficult to formulate. None of the known specimens of H. (H.) marroti are known to have as coarse ornament as some H. (H.) howarthi, (e.g. Figs 3D,G; 6A–B), or to grow to such large size, but some of the Madagascan specimens, e.g. Collignon’s (1970, p. 75, pl. 638, fig. 2342) (here Fig. 7A–B) or H. (H.) besairiei (Collignon 1970, p. 77, pl. 638, fig. 2349) (lectotype here designated; Fig. 7L–N) are impossible to distinguish from the French specimens of H. (H.) marroti figured by Kennedy (1986).

 

It is possible that, given more material, H. (H.) howarthi may eventually be merely regarded as a larger, more coarsely ornamented, South African-Malagassy subspecies of H. (H.) marroti. " - Klinger & Kennedy. 2011. Hoplitoplacenticeras (H.) howarthi Collignon, 1970 (Cephalopoda: Ammonoidea) from KwaZulu-Natal, South Africa and Madagascar; intraspecific variation, dimorphism and affinities. African Natural History, Volume 7

 

 

Hope all these help.

[goatinformationist]

They just don't come any better than this.

[ozrit]

Thank you very much abyssunder!