Some uncommon to rare Anisian Ammonites from Nevada

[old digger]

The Anisian (Middle Triassic) ammonite faunas of Nevada have long been known to provide the most complete sequence for this stage in the world, with many genera such as Gymnotoceras, Frechites, and Nevadites being represented in abundance at classic sites such as Fossil Hill in the Humboldt Range.  Here I will illustrate three  less common to rare forms that are also present in Middle Anisian strata in Nevada.

 

Unionvillites hadleyi (Smith)

Provenance: Humboldt Range, Congress Canyon near Unionville

Age: Middle Anisian, Hyatti Zone, Hadleyi Subzone

A well-preserved specimen showing the braided keel.

Reference: Bucher, H., "Ammonoids of the Hyatti Zone and the Anisian Transgression in the Triassic Star Peak Group, Northwestern Nevada, USA" (Palaeontographica 223, pp. 137-166, Stuttgart, 1992).

This keeled, tuberculate form has been reported from a few localities in the Humboldt Range.

 

 

Semibeyrichites sp.

Provenance: Humboldt Range, Big Canyon north of Unionville

Age: Middle Anisian, Hyatti Zone, Mctaggarti Subzone

Reference: Bucher (1992) above.

Bucher reported two specimens from the Humboldt Range as the first occurrence of this genus in the western hemisphere.  This specimen was found very close to Bucher's locality.

 

 

Chiratites bituberculatus Monnet and Bucher

Provenance: south of Favret Canyon, Augusta Mountains

Age: Middle Anisian, Shoshonensis Zone, Mojsvari Subzone

Reference: Monnet, C. and Bucher, H., New Middle and Late Anisian (Middle Triassic) ammonoid faunas from northwestern Nevada (USA): taxonomy and biochronology (Fossils and Strata, 52, 2005).

Monnet and Bucher proposed this species on the basis of a single specimen from the Augusta Mountains.  I have since discovered about six specimens at another nearby locality.

 

[old digger]

That should be, "Some Uncommon to Rare Anisian Ammonites," sigh.

[Ludwigia]

Thanks for posting these Rare (I figured that was a typo ) Ammos. I'm sure that @andreas would be interested in seeing this.

[JohnJ]

5 hours ago, old digger said:

That should be, "Some Uncommon to Rare Anisian Ammonites," sigh.

 

Corrected.  

[FossilDAWG]

Thanks for showing these to us.  Maybe one day I'll get the chance to visit some of the Nevada Triassic sites.  Until then, thanks for the chance to experience these fossils vicariously if not in hand.

 

Don

[Tidgy's Dad]

Really nice to see these specimens. 

We don't see Triassic ammonoids often enough.