This is Mazon Monday post #145. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Anthracaris gracilis was described by 1865 by F.B. Meek and A. H. Worthen as Anthrapalaemon gracilis. It is very similar to Mamayocaris jaskoskii. While M. jaskoskii is known from Pit 11, A. gracilis is known from the more terrestrial localities like the Mazon River. Both animals were bottom dwelling scavengers. George Langford referred to it as Anthrapalaemon gracilis.
Fielding Bradford Meek and Amos Henry Worthen were both prolific in describing new species in the middle 1880's. They collaborated on many papers. Meek worked at the USGS, while A.H. Worthen was the second state geologist of Illinois and the first curator of the Illinois State Museum. He had an extensive fossil collection, which now resides at the Prairie Research Institute (PRI) at the University of Illinois.
Fielding Bradford Meek via Wikipedia
Amos Henry Worthen via Wikipedia
The genus Anthracaris was erected in 1962 by Harold Kelly Brooks in his seminal work "THE PALEOZOIC EUMALACOSTRACA of NORTH AMERICA".
Genus ANTHRACARIS, new genus
The singular nature of the species described as Anthrapalaemon gracilis by Meek and Worthen is herein proven. The species has affinities with the fossils assigned to Pygocephalus Huxley (1857) and its synonym Anthrapalaemon Salter (1861); however, it is distinguished (Text Pl. 2) by the presence of a pair of spines on the hepatic region of the carapace, the sympod of the first thoracic appendage is not unlike those succeeding. There are large endites on the sympods of both the first and second thoracic appendages, the endopod of the third thoracic appendage is not fully developed as a pereiopod, and there is an absence of oostegites. A large seminal receptacle is present on the last thoracic sternite of the females of both genera. The generic name Anthracaris is proposed to distinguish this crustacean; the incongruity of which was noted by Packard (1885 b) in proposing the family Anthracaridae. From the many excellent specimens now available in the concretions from Mazon Creek, Illinois, the type species, Anthrapalaemon gracilis Meek and Worthen, will be described in detail.
Anthrapalaemon gracilis Meek and Worthen, 1865, p. 50-51.
Anthrapalaemon gracilis, Meek and Worthen, 1866, p. 406-408, pl. 32, fig. 4.
Anthrapalaemon gracilis, Meek and Worthen, 1868 b, p. 554, figs. a, b. Anthrapalaemon gracilis, White, 1884, p. 180, pl. 38, figs. 8, 9.
Anthrapalaemon gracilis, Packard, 1885 b, p. 880-881.
Anthrapalaemon gracilis, Packard, 1886 c, p. 135-140, pl. 7, figs. 3, 3 a, 4, 4 a 5, 6.
Anthrapalaemon gracilis, Van Straelen, 1931, p. 24.
The "Richardson's Guide to the Fossil Fauna of Mazon Creek" mentions A. gracilis on Page 161 in Chapter 12 "Crustacea", written by Frederick R Schram, W.D. Ian Rolfe, and Andrew A. Hay.
Anthracaris gracilis Meek and Worthen, 1865
Figures 12.16, 12.17Carapace with well-developed branchial region covering the gills, anterolateral spines large and followed by a row of eight or more marginal serrations, hepatic and gastric spines present, arms of the cervical groove meeting in the mid- line; tailfan with well-developed flaplike uropods, exopodal ramus (outer branch), with two segments and the joint between the two (diaresis) diagonally directed; telson truncated at the point of attachment of the caudal furca (tail lobes), which are in turn posteriorly directed, accessory projection of telson directed over the lobate caudal spine.
This pygocephalmorph mysidacean is a characteristic component of the Braidwood biota. It is rarely found in Essex localities. Like its close relative, Mamayocaris jaskoskii, this creature was a bottom-dwelling scavenger.
Specimens
From the "Richardson's Guide to the Fossil Fauna of Mazon Creek"
From ESCONI member George Witaszek
