Crinoid

Alcimocrinus cf. A. ornatus

• Pennsylvanian
• Graford Formation
• Wise County, Texas, USA

Size: 4.5 cm crown

This crinoid crown was unidentified when I acquired it, but strongly resembles the genus Alcimocrinus with its low cup with strong basal concavity, symmetrical junction between the radials and first primibrachs, and uniserial arms with an initial isotomous branch on the second primibrach followed by endotomous branching starting on the secondibrachs. There are two species of described Alcimocrinus: Alcimocrinus ornatus from the Mississippian of Oklahoma and Alabama, and Alcimocrinus girtyi from the Pennsylvanian of Oklahoma. Despite being Pennsylvanian-aged, this piece actually seems to resemble the Mississippian A. ornatus more closely in its lower number of arm branching and the similar-thickness of its main arm trunks and inner arms. In any case, a very interesting specimen which may be a new occurrence of Alcimocrinus from the Pennsylvanian of Texas and possibly a new species of Alcimocrinus entirely.



This specimen is from the collection of renowned crinoid specialist Gary Webster.