CONLINOCERAS TARRANTENSE

Previously Calycoceras Tarrantense, this ammonite is now called Conlinoceras tarrantense after J.P. Conlin, a famous early 20th-century fossil collector from Texas, USA.

Ammonite expert Bill Cobban used this collection to describe many Texas Cretaceous ammonites species including this species from Tarrant County, Arlington, Texas.

He was a surveyor by training and kept incredibly detailed notes on the context of his fossils.

Conlin donated his collection to the USGS and we have learned much by studying it along with other specimens from the Lone Star State. Almost a quarter of Texas is covered by Cretaceous strata, much of it fossiliferous. If we stepped back 95 million years, the world and what we now call Texas was a very different place.

95 million years ago, during the Late Cretaceous, a shallow seaway separated North America into separate eastern and western landmasses. We have a pretty complete picture in the fossil record of the western groups of species but relatively little in comparison to their cohorts in the east.

At the time this fellow was swimming our ancient seas, he was sharing the Earth with carnivorous dinosaurs, duck-billed dinosaurs, mammals, crocodilians, turtles, a variety of amphibians, prehistoric bony fish, oddly prolific sea cucumbers, various invertebrates and plants. Many of these sites are just being written up now and contain new species just being discovered.

During the Late Cretaceous Period, a shallow seaway separated North America into separate eastern and western landmasses. The Woodbine Formation in Texas preserves a rare fossil record of this time for the east, but many of these fossils are isolated and incomplete, making interpretations more difficult. Preliminary excavations at the Arlington Archosaur Site (AAS) are providing hints at a more complete ecosystem, preserving similar patterns of change to what we see in the west.

The Arlington Archosaur site contains an extraordinary diversity, abundance, and quality of fossil material, preserving one of the most complete terrestrial ecosystems known for this time period and area.

These outcrops and the fossils they contain have a lot to tell us about Late Cretaceous life in the east. Over 2200 individual specimens have been found belonging to numerous groups including carnivorous dinosaurs, duck-billed dinosaurs, crocodilians, turtles, mammals, amphibians, sharks, bony fish, invertebrates, and plants.

Many of the fossils found here represent brand new species and studying these fossils will help to establish the geographic and environmental forces that shaped Cretaceous ecosystems in North America by providing a necessary comparison to the fossil record of the west.

VOAY ROBUSTUS

This big beastie is Voay robustus. You likely met him first as Crocodylus‭ (‬C.‭ ‬robustus‭) from his original naming by Grandidier and Vaillant in‭ 1872. 

Looking more closely at his remains revealed that he is nearer in design to the dwarf crocodile Osteolaemus. 

The type series cannot be identified, but the original description includes details consistent with known specimens that almost certainly pertain to the same species. 

It had a prominent triangular ‘horn’ on the posterolateral corner of each squamosal; near-exclusion of the nasals from the external naris; constricted supratemporal fenestral rims; a dorsoventrally deep snout; a constricted external mandibular fenestra in which the surangular–angular suture emerges from the posterior rather than posteroventral margin; and robust limb and limb-girdle elements. 

It shares with Osteolaemus, and with several extinct crocodylids from the Neogene of Africa, a depressed surface of the pterygoid around the internal choana forming a choanal ‘neck’. It cannot be referred to as Crocodylus and a new praenomen, Voay, was established for its reception. 

In 2007, Christopher‭ ‬A.‭ ‬Brochu created a new genus, Voay, and this fellow became Voay robustus. Christopher published his work in the Zoological Journal of the Linnean Society in Volume 150, Issue 4, August 2007, Pages 835-863. Voay lived into the Holocene of Madagasgar, perhaps meeting some of our relatives 2,000 years ago. Voay was replaced by Crocodylus niloticus in Madagascar as they moved into the niche left by Voay's ultimate demise. 

https://doi.org/10.1111/j.1096-3642.2007.00315.x

WHALER

 

INKY BEAUTY: AMMONITE OF PONGO DE MANSERICHE

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.