Sunday, 30 December 2018

CALYCOCERAS TARRANTENSE

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

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’ve 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 for 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 AAS are providing hints at a more complete ecosystem, preserving similar patterns of change to what we see in the west.

The AAS 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.

The AAS has 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.

Saturday, 22 December 2018

PHASIANUS CHOLCHICUS

Common Pheasant, Phasianus Cholchicus
These playful lovelies are beautiful examples of the Common Pheasant, Phasianus Cholchicus. We associate them with tweet shorn English aristocrats jauntily going about the hunt on horseback. Pheasants build their nests on the ground and can fly for short distances. They spend their days searching around field and stream looking for tasty insects, seeds and grain.

Friday, 21 December 2018

PUMA CONCOLOR

Cougars are meat-eating mammals (primarily dining on deer) who boast being the most widely distributed land mammal in the Western Hemisphere. They are impressive athletes, able to leap 18 feet or more straight upward from a sitting position.

They lead solitary lives and are excellent at avoiding humans for the most part. Cougars have a massive range which runs from the mountainous Canadian Rockies in northwestern Canada all the way down to Patagonia in South America. These cats make their dens in mountain graggs, along rocky ledges, in dense woodland areas and under uprooted trees and debris.

Sunday, 2 December 2018

HOLCOPHYLLOCERAS

Amazing suturing on this lovely ammonite, Holcophylloceras mediterraneum, (Neumayr 1871) from Late Jurassic (Oxfordian) deposits near Sokoja, Madagasgar.

The shells had many chambers divided by walls called septa. The chambers were connected by a tube called a siphuncle which allowed for the control of buoyancy with the hollow inner chambers of the shell acting as air tanks to help them float.

We can see the edges of this specimen's shell where it would have continued out to the last chamber, the body-chamber, where the ammonite lived. Picture a squid or octopus, now add a shell and a ton of water. That's him!