This is Mazon Monday post #257. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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ESCONI has played a significant role in the study of the Mazon Creek fossil biota. Its members have authored at least nine books on the subject, beginning with George Langford, Sr. in the late 1950s and early 1960s, followed by the ESCONI Keys and Creature Corner books of the 1980s and 1990s, and most recently, the excellent works of Jack Wittry. Members have also contributed specimens—ranging from individual fossils to entire collections—to renowned institutions such as the Field Museum in Chicago, the Smithsonian in Washington, D.C., and other prestigious museums worldwide. In addition to these contributions, ESCONI members have dedicated their time to educating the public about the significance of Mazon Creek and science as a whole. Their efforts have earned ESCONI widespread recognition, including the honor of having two animal species named after the organization.
The first species named for ESCONI was Esconichthys apopyris by the late Dave Bardack in 1974. Dave worked at the University of Illinois at Chicago and the Field Museum. Dave was a specialist on fishes and was responsible for naming and describing many of the fishes of the Mazon Creek biota, including early hagfish and lamprey. He wrote Chapter 17 "Fishes: Agnatha, Acanthodii, and Ostreichthyes" of the Richardson's Guide to the Fossil Fauna of Mazon Creek".
E. apopyris was described in "A Larval fish from the Pennsylvanian of Illinois" in the Journal of Paleontology. The classification of this species is somewhat problematical. It's a cordate of some type, some have proposed a larval lungfish, but a larval amphibian has also been discussed. Collectors have referred to these fossils as the "Blade". There is some new exciting reseach on E. apopyris so stay tuned!
The description of E. apopyris from the Richardson's Guide.
Esconichthys apopyris Bardack
Specimens are preserved dorsoventrally or later-ally compressed as well as partially twisted. Lat-erally compressed specimens typically show 25 to 30 myomeres (body muscle segments). There are two pairs of elongate, external gills; the pos-terior pair is usually half the length of the body. Each gill bears numerous fine filaments along the distal half of the gill bar. Two pairs of hard structures that cannot be identified (they are not otoliths) as specific parts of the skull lie posteromedially to the eyes. These specimens are probably larval based on the lack of ossification, presence of gills, and simple myomeric development. Taxonomic assignment of Esconichthys to a group of vertebrates is difficult.
Bardack (1974) suggested reasons why it might be a larval lungfish, and Schultze (1977) argued that it is probably not a lungfish or an amphibian without providing an alternative placement. This form, commonly called by collectors "blades," "grasshoppers," or "tadpoles" based on their preserved shapes, is the most common vertebrate in the Mazon Creek fauna, even if one counts all of the lungfish scales. All specimens are from the Essex fauna.
Specimens
The second species named for ESCONI is Esconites zelus. It was described in 1977 in a paper by Ida Thompson and Ralph Johnson. "New Fossil Polychaete from Essex, Illinois" was published in Fieldiana, a journal of the Field Museum of Natural History in Chicago, IL.
Esconites zelus is an extinct species of polychaete worm found only in the Mazon Creek biota, Essex fauna. A nice drawing from the paper...
And, the dedication to ESCONI in the paper.
The resurrection of the species described above has been greatly aided by two groups: collectors in the northern Illinois area and colleagues at Field Museum. We dedicate this new species, Esconites zelus, to the members of the Earth Sciences Club of Northern Illinois (ESCONI) in gratitude for their valuable co-operation in making their collections available for study, in lending specimens to Field Museum, and in donating particularly valuable specimens. Special thanks go to Mr. and Mrs. Ted Piecko, Mr. and Mrs. Francis Wolff, and Mr. and Mrs. Calvin George for generous donations of specimens. At Field Museum, Dr. Rainer Zangerl provided the genial matrix within which this study was made and Dr. Eugene S. Richardson, Jr., established valuable liaisons with collectors and gave advice and help generously.
The following appeared in Creature Corner by Andrew A. Hay and Don Auler. The article was published in the November 1987 issue of the ESCONI Bulletin "The Earth Science News" and was later included in the book Creature Corner published in 2001.
Discoveries at Pit 11 of hitherto rare and/or unknown marine, near-shore invertebrates alerted investigators to the probability of finding annelid type worms among the Essex Fauna. They were not disappointed. Over 20 worm-like species have been described, 2/3 of which have been classified as polychaetes.
The polychaete structures preserved with the best detail are the jaws (mandibles), setae, and cirri (bristles and hairs/tentacles). One of the most common Essex polychaetes, Esconites zelus, also possessed the most visible and largest mandibles.
E. zelus has a long (5 and ½ inches in some specimens) narrow body outline. The number of body segments, 20 to 80, increase with length. Commonly the body outline is seen as a difference in color on the concretion surface. In other specimens, the fine detail visible is remarkable. Jaw apparatus is the most obvious feature. These large, prominent, wing-like mandibles are dark brown to black carbon films.
Body segments bear parapodia (fleshy protrusions/stump feet) on each side. Parapodia are equipped with bristles and hairs, used to propel these predaceous, free-swimming annelids. Occasionally, the branchia (gills) can be seen among the setae and cirri that adorn the parapodia. The "head" is equipped with long tentacles and a "tail" with several long hairs. Well preserved jaws and long body configuration are the best field marks.
Specimens
