GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 88-5
Presentation Time: 9:15 AM


KEYES, Richard, P.O. Box 21061, Huntsville, AL 35813

Crinoids are a fundamental part of the rich diverse marine biota of invertebrates and vertebrates that flourished during the lower Bangor interval, middle Chester, upper Mississippian, in northwest Alabama. The class Crinoidea Miller, 1821 is represented by 49 species from 33 genera (22 genera of Eucladida Wright, 2017, 2 genera of Flexibilia, 9 genera of Camerata) in the preserved portions of the communities from a set of diverse paleo-environments. Most complete crinoids along with the associated fauna were normally found in transported event lenses, but are rarely preserved where they lived. They were typically preserved in a calcareous clay/silt/sand to silty/sandy limestones. The community could be composed almost entirely of crinoids to a trivial part, and fenestrate bryozoans, Archimedes, were common in many lower Bangor paleo-communities. The crinoids in the community were consistently dominated by 1 to 3 genera (normally 70-90%), the other genera present were normally only minor elements. Significant variations in the composition of these preserved crinoids in the communities occur, with nearly half the identified species (24) known to be the dominant crinoid species preserved in a given community. Eucladids dominated nearly all the crinoids in the communities by number of specimens and species present during the middle Chester. Overall, the most common eucladid crinoids are Aphelecrinus randolphensis (Worthen, 1873), Pulaskicrinus popensis (Worthen, 1882) n. comb., Phanocrinus cf. P. maniformis (Yandell and Shumard, 1847), Zeacrinites wortheni (Hall, 1858), and Dasciocrinus florialis (Yandell and Shumard, 1847). At times (uncommon), Camerates were the dominant crinoid type, even though they were generally smaller in size and represented by far fewer species than eucladid crinoids. The camerate crinoids Camptocrinus Wachsmuth and Springer, 1897, Acrocrinus shumardi Yandell, 1855, and Hyrtanecrinus pentalobus (Casseday and Lyon, 1862) were prolific in the lower Bangor of north Alabama, and each has been observed as the dominant crinoid present in the preserved portion of a community. Camptocrinus cf. C. cirrifer (Wachsmuth and Springer, 1897) is known to be the sole dominate genus on one particular shoal, comprising 95%± of the many preserved communities.