Saturday 20 April 2024


This inky beauty is Prolyelliceras ulrichi (Knechtel, 1947) a fast-moving nektonic carnivorous ammonite from Cretaceous lithified, black, carbonaceous limestone outcrops in the Pongo de Manseriche gorge in northwest Peru. 

If you look closely, you can see that this specimen shows a pathology, a slight deviation to the side of the siphonal of the ammonite. We see Prolyelliceras from the Albian to Middle Albian from five localities in Peru.

The canyons of the Amazon River system in the eastern ranges of the Andes of Peru are known by the Indian name pongo

The most famous of these is the Pongo de Manseriche, cut by the Marañon River through the eastern range of the Andes, where it emerges from the cordillera into the flat terrane of the Amazon Basin. The fossil exposures here are best explored by boat. The reality of the collecting is similar to the imagined. I was chatting with Betty Franklin, VIPS, about this. They float along and pick up amazing specimen after amazing specimen. When the water rises, the ammonites are aided in their erosion out of the cliffs.  

The Pongo de Manseriche lies nearly 500 miles upstream from Iquitos, and consequently nearly 3,000 miles above the mouth of the Amazon River. It is situated in the heart of the montaña, in a vast region the ownership of which has long been in dispute between Peru and Ecuador, but over which neither country exercises any police or other governmental control. There is an ancient tradition of the indigenous people of the vicinity that one of their gods descended the Marañón and another ascended the Amazon to communicate with him. Together they opened the pass called the Pongo de Manseriche.

Reference: M. M. Knechtel. 1947. Cephalopoda. In: Mesozoic fossils of the Peruvian Andes, Johns Hopkins University Studies in Geology 15:81-139

W. J. Kennedy and H. C. Klinger. 2008. Cretaceous faunas from Zululand and Natal, South Africa. The ammonite subfamily Lyelliceratinae Spath, 1921. African Natural History 4:57-111. The beauty you see here is in the collection of the deeply awesome José Juárez Ruiz.