Time: Carboniferous, Westphalian Stage
mm = 1 inch): Fossil is 25 mm on a 45 mm by 24 mm nodule pair
Mazon Creek, Francis Creek Shale, Braidwood, Illinois
The Mazon Creek deposits of the region near Braidwood, Illinois rival
the other famous Lagerstatten of the Burgess Shale, Solnhofen, and
Liaoning for the variety of detailed life preserved. Many exquisitely-preserved
specimens are found in the ironstone nodules that make up the deposits.
example is of the lamprey Maymyzon, and comes from Mazon Creek itself.
Since there is no bony tissue, preservation was difficult. Notice
the presence of the eye, gills and what seems to be preserved chromatophores
in the miniscule dots that can be seen. There is one repaired crack
to one side, but it does little to detract from this exceptional specimen.
Other than an example from the Mississippian Bear Gulch fauna, this
is the only fossil lamprey known. I have recently been able to procure
specimens from a family who has been collecting this material in the
field for three generations, and will continue posting material as
it becomes available to me.