Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Master of Science (MS)

Document Type

Master's Thesis


Arts and Sciences


Earth and Environmental Sciences (Geology)

First Advisor

Dr. Frank Ettensohn


New morphological observations of Edriocrinus Hall, 1858, enable a modern, holistic view of this unusual crinoid genus, previously included in the Superorder Flexibilia (Zittel, 1895) Wright et al., 2017. Re-analysis of Edriocrinus suggests that the genus should now be assigned to the Order ‘Dendrocrinida’ within the Magnorder Eucladida Wright, 2017 based on the five infrabasals, single radianal in the cup, absent anal sac, and non-pinnulate arms with rectangular uniserial brachials. Moreover, examination of the slight variations separating the current 14 Edriocrinus species indicates that these “species” are likely ecophenotypes. The current Edriocrinus species are revised based on firmly bound calyx plates; five high infrabasals; lack of patelloid processes; straight muscular radial articulations; brachials that are free above the radials; and muscular articulation between brachials and synonymized to four species, E. pocilliformis, E. sacculus, E. pyriformis, and E. dispansus. Edriocrinus is restricted to a ~25 Myr interval in the Early and Middle Devonian, a time of global eustatic and tectonic disruption, when its stemlessness provided an adaptive advantage throughout environments in the Old World and Eastern Americas realms. These realms were in subtropical to warm temperate climatic zones that encompassed the Rheic Ocean between 25°and 35⁰ south latitude. Edriocrinus is found in formerly adjacent parts of east-central North America, south-central Europe, southern England, and northern Africa. The genus persisted in south-central Europe until the Chotec Event in early Eifelian time and in North America until the Bakoven Event in mid-Eifelian time, when episodes of transgression and anoxia led to genus extinction.

Digital Object Identifier (DOI)

Funding Information

This study was supported by the University of Kentucky Earth and Environmental Sciences Department's Pirtle Fellowship for 2017 and 2018.