This is Mazon Monday post #139. What's your favorite Mazon Creek fossil? Tell us at email:[email protected]. Thanks!
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For this week's Mazon Monday, we have Lepidocystis sp., which is a type of spore packet associated with the cone genus Polysporia. Early Mazon Creek collectors referred to this as "cockroach egg sacs". This is known to be false as Mazon Creek cockroaches are not cockroaches, but roachoid. Additionally, egg sacs in true cockroaches didn't evolve until the late Mesozoic. Lepidocystis is considered uncommon. It was described in by Leo Lesquereux in 1879-1880.
Lepidocystis sp. appears in Jack Wittry's book "A Comprehensive Guide to the Fossil Flora of Mazon Creek" on page 39.
Lepidocystis sp. Lesquereux, 1879
1879-80. Lepidocystis Lesquereux: p. 454, pl. 69, figs. 3-7
1966. Isolated Lycopod Sporangia Crookall: p. 522, pl. 99, figs. 6-8
1969. Lepidocystis Lesquereux; Darrah: p. 183, pl. 51, fig. 2DESCRIPTION: Lepidocystis has a sac-like structure that is often compressed and wrinkled in various ways mak- ng no two appear exactly alike. The structures are generally elongated and more rounded on one end than the other. Their outer surfaces appear dull black and may be either smooth if filled with microspores or bumpy when still filled with megaspores. When their contents are exposed (see Fig. 2), large numbers of megaspores or microspores are seen. These are often a golden color, uncompressed, and loose. Generally, only megaspore sporangia are found open with visible spores. The microspore versions are mostly found unopened or as smooth and empty outer shells.
REMARKS: Lepidocystis is uncommon. They are considered to be the sporangia attributable to the cone genus Polysporia. This type of cone fragmented easily, making any direct connections between Lepidocystis species and cones species difficult. At this time, only one species of Polysporia (P. mirabilis) is recognized in the Mazon Creek flora. It is unknown if all Lepidocystis species belong to this one species or to several as-yet-undiscovered Polysporia cone types.
This form had often been called a "cockroach egg sac" by early collectors. The cockroaches found in the Mazon Creek fauna are not true cockroaches and are now referred to as roachoids (Grimaldi and Engel, 2005). The roachoids deposited eggs directly into the soil. Egg sacs in true cockroaches do not clearly appear until the late Mesozoic.
The genus Schopfia (Janssen, 1940) was erected on forms similar to Lepidocystis and described as being comparable fertile plant structures. They have also been referred to as "seed attachments" (Langford, 1958). Its various species are now believed to be different parts of large arthropods (Lemay and Hannibal, 2002), such as Arthropleura. Schopfia has unequal and straight sides with sharp corners (see Fig. 3) compared with the more rounded and oblong Lepidocystis. They are brought together here for the purpose of comparison only.
Specimens
From "A Comprehensive Guide to the Fossil Flora of Mazon Creek"
From the Field Museum
From ESCONI member Rich Holm