This is Mazon Monday post #269. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Belotelson magister is the most common crustacean/shrimp fossil in the Mazon Creek biota. Fossil preservation of Belotelson magister varies with the most common presentation being a molt. It was described as Acanthotelson magister by Alpheus Spring Packard (1839-1905) in 1885 in "On the Syncarida, a hitherto undescribed synthetic group of extinct malacostracous Crustacea ; II." He named it after the already erected Acanthotelson stimpsoni. Packard used a specimen from Mazon River sent to him by J.C. Carr of Morris, IL, who was a prolific collector of Mazon Creek fossils in the late 1800s. Until Pit 11 opened in the late 1950s, only three specimens of B. magister were known.
I have received from Mr. J. C. Carr, for examination, a specimen from Mazon Creek, collected at the same place as the nodules containing the Acanthotelson, showing the remains of a crustacean closely similar to, if not generically identical with Acanthotelson, Unfortunately the head and antennae are not preserved sufficiently well for description,.so that the following arcount should be regarded as provisional, until better-preserved specimens are found. As seen by the photograph (11. 11, figs. 4,5), the animal was of the same general shape as Acanthotelson in ; when it died the body was preserved on itself, so that the two longer antennae crossed the end of the abdomen with its appendages. The abdomen in its dorsal aspect, with the telson and last pair of uropoda, are tolerably well preserved. The faint traces of the head, unless we are mistaken, show that it was of the same general shape as in Acanthotelson. There are traces of two pairs of antennae: one fragment, the innerrmost, showing traces of six joints; and there are faint impressions, not showing the joints, of two long antennae, which are about half as long as the body. There are no traces of any thoracic or abdominal appendages except the last pair of uropoda.
Packard was an American entomologist and paleontologist. He described over 500 new animal species – especially butterflies and moths – and was one of the founders of The American Naturalist. He served as a professor at Brown University.
Packard circa 1888
Belotelson magister can be found on page 77 of "The Mazon Creek Fossil Flora" by Jack Wittry.
Belotelson magister Packard, 1886
Belotelson magister is a moderate to large lobsteroid crustacean first described in 1886. Prior to the opening of Pit 11, only three specimens of this genus were known, all from the Braidwood Fauna. Since then, it has become a far more commonly found crustacean.
The carapace is smooth and is about half the length of the animal, featuring an optic notch with stalked eyes. Its rostrum is prominent, averaging 60 percent of the total length of the carapace. The antennae are well-developed. The thoracopods are long, about equal in length, and well-developed for walking. The tail members form rather thin reinforced blades on the sides with a short, sharp spike for a telson.
Based on the spiky tail, this animal was likely a poor swimmer. However, having rather strong legs, it was probably an active scavenger/predator. B. magister occurs in the Carboniferous of North America and Europe.
Belotelson magister appears in Chapter 12 "Crustacea" in the "Richardson's Guide to the Fossil Fauna of Mazon Creek". Chapter 12 was written by Frederick R. Schram, W.D. Ian Rolfe, and Andrew A. Hay.
Order Belotelsonidea
Well-developed carapace and tailfan, all eight thoracic limbs as well-developed, uniramous walking legs.
Belotelson magister Packard, 1886 Figures 12.14, 12.15
Robust crustacean; rostrum long and robust; antennules and antennae large and well developed; carapace subrectangular in lateral outline, originally very well sclerotized and undecorated except for a small pore on the posterior midline; thoracic limbs large and composed of only a single branch or endopod; abdomen well developed, with pleural lobes set off and some-what pointed along their ventral margins; pleopods biramous and flaplike; tailfan well developed, uropods broadly rounded delicate flaps (except along the reinforced lateral margins of the exopods), telson large and subtriangular with terminal pair of moderately developed, delicate, lobate caudal furca.
This species was known originally from only three specimens in the Braidwood fauna but is by far the most common type of crustacean in the Essex fauna. The species is apparently distinguished by a great variety of types of preservation including juvenile and adult forms as well as a great variety of cast-off exoskeletons.
This lobsterlike form represents an extinct order of crustaceans that flourished during the Coal Age of Europe and North America. A second yet undescribed species, possibly related to B. magister, is common in Mazon Creek collections and has a slightly smaller size with an extremely long and rather delicate rostrum.
Specimens
From Packard
From Wittry.
ESCONI member Rich Holm
A molt
