Here's a later update on the Crittenden Springs ammonoids, from Revue de Paléobiologie Vol. spécial 8 (2000):
"The relationships of color patterns and habitat for Lower Triassic Ammonoids from Crittenden Springs, Elko County, Nevada
Glen E. GARDNER, Jr. & Royal H. MAPES
Abstract
The Lower Triassic Crittenden Springs ammonoid fauna from Nevada is extremely diverse, with thirty-two species. Of the twenty-nine taxa represented in the Ohio University collection, fifteen show evidence of having color patterns or some kind of shell coloring in life. There are three types of color patterns exhibited in the ammonoid fauna. These three types are as follows: 1) monochromatic (Preflorianites toulai, Arctoceras sp., Flemingites russelli), 2) transverse bands (Owenites koeneni, Paranannites aspensis, P. mulleri, Prosphingites slossi, Juvenites septentrionalis, and J. thermarum), and 3) longitudinal stripes (Dieneroceras knechti, D. spathi, D. subquadratum, Kashmirites sp., Wyomingites whiteanus, and Xenoceltites sp.). After the color pattern documentation, all the Crittenden Springs taxa were integrated into the WESTERMANN (1996) paleoecological ammonoid habitat model.
After integration, all of the ammonoid taxa having transverse color patterns (six taxa) clustered in the planktonic-vertical migrator habitat of the basin biofacies at depths of less than 450 meters. With one exception, all of the ammonoid taxa having longitudinal color bands (six taxa) clustered in the planktonic-drifter habitat of the inner slope and platform biofacies at depths of less than 125 meters. And, all three of the monochromatic taxa clustered in the nektonic and demersal-nektonic habitats of the inner slope and basin at depths no greater than 125 meters. The taxa without observed color patterns also clustered in these latter two habitats.
Thus, within our limited data set, the consistent distributions of species with and without color patterns provide independent support for the habitat divisions within the WESTERMANN Model. Also, the consistent similarities in coloring pattern distribution as compared to shell form and habitats indicate that type of color pattern and habitat are closely related paleobiological phenomena for Lower Triassic ammonoids."