Ordovician – Silurian
Lichenocrinus is an extinct holdfast genus of stationary upper-level epifaunal suspension feeders
Identification in Hand Sample:
- A type of holdfast belonging to several crinoids
- Structures range in size from a few millimeters to more than 10 mm and may be either smooth or very nodose
- A plated upper surface, supported by numerous radiating lamellae
- Deep plated crater contains the distal extremity of the stem
- Disc composed of an indefinite number of polygonal plates
- Considered to be part of Ectenocrinus
- The unique, multiplated holdfast given the name “Lichenocrinus” in the older literature is another relatively common crinoid fossil. Despite the fact that generic and specific names have been assigned to these structures, the name is properly placed in quotations because it is not a valid biological name. Rather, it is a name for a type of holdfast belonging to several crinoids, including Ectenocrinus and Cincinnaticrinus. “Lichenocrinus” structures range in size from a few millimeters to more than 10 mm and may be either smooth or very nodose. They are found either on shells or on hardgrounds (limestone beds that lithified soon after deposition).
Treatise on Invertebrate Paleontology, Part T, Vol. 2(1) (1978):
- Comprises a plated upper surface, supported by numerous radiating lamellae, which rise vertically from a distinct floor plate; in the center of the upper surface, a deep plated crater contains the distal extremity of the stem
- The organism represented by Lichenocrinus consisted of a calyx, a column, and a basal body. Of the first, we have no examples whose relationship to Lichenocrinus is assured. Though in 1898, G. Ashmann, A. Albers and I found a colony of Lichenocrinus in the Economy of Plaineville, Ohio. All specimens had columns, some three inches in length, attached to the bases. Three of the specimens were complete with calyx, column, and basal body. One of the calyces had three arms consisting of elongated plates; none of the arms showed bifurcation.
- Description.-“Bodies parasitic on shells and other foreign substances. From discoid or depressed-convex, with a proboscidiform appendage rising from the center. Disc composed of
an indefinite number of polygonal plates and apparently have no distinct mode of arrangement. Proboscis perforate, and in the known species formed of five ranges of short plates alternating and interlocking at their margins.'”