Previously Calycoceras Tarrantense, this ammonite is now 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 currently being explored with new species shedding additional light year upon year on these ancient ecosystems.
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.