This is Mazon Monday post #219. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Figure 51.1, Myriacantherpestes sp.; modified after Shabica and Hay (1997). Scale bar = 10 mm.
Last Friday (Fossil Friday #215), we highlighted a stunning millipede from the Pennsylvanian of Kansas. That's wasn't the first millipede from Kansas that made it to Fossil Friday, as Fossil Friday #134 was about the same genus of millipede, Myriacantherpestes. Both animals came from the same quarry in Hamilton, Kansas. The Hamilton Quarry is famous for the well preserved fossils of plants, vertebrates, and invertebrates, including large winged insects, water scorpions, and, of course, millipedes. The strata exposed at that locality date to around 295 million years ago, which is about 12 million years younger than Mazon Creek. The depositional environment at Hamiliton indicates it to have been a river estuary.
Mazon Creek also features millipedes of the genus Myriacantherpestes, which is related to the more common Euphoberia (Mazon Monday #23). The Mazon Creek Myriacantherpestes are classified as Acantherpestes. The genus Acantherpestes was erected by Fielding B. Meek and Amos H. Worthen in 1868 in Part II of the Geological Survey of Illinois. It was described from a fossil from Mazon Creek. Meek and Worthen figure prominently in the early history of Mazon Creek, having named numerous animals. Worthen was the first curator of the Illinois State Museum. His extensive collection now resides at the Prarie Research Institute Center for Paleontology at the University of Illinois.
In 1975, the genus Myriacantherpestes was proposed by J.J. Burke of the Cleveland Museum of Natural History in "A new millipede genus, Myriacantherpestes (Diplopoda, Archipolypoda), and Myriacantherpestes bradebirksi, new species, from the English UK Coal Measures", which was published in Kirtlandia. In the discussion, he details the differences between Myriacantherpestes and Acantherpestes.
The overall surface is rugose, markedly so in the dorsal portion. There are definite angular depressions in the region of the genae. In restoring the antennae, I have placed them in these depressions. Except for two, or at best three, rather stout proximal antennomeres, the antennae of Myriacantherpestes are unknown. I am restoring them as stout, somewhat flattened, and capable of being recessed. In both Euphoberia and Acantherpestes the antennae are more rounded and fairly slender.
But the lateral spines and spinelets of these English taxa, and all other species of Myriacantherpestes as well, contrast sharply with those of Euphoberia and Acantherpestes. Neither of the latter genera display the elongate lateral spine of Myriacantherpestes, which in all species of the genus spreads widely enough to have covered and protected the legs. Except for M. hystricosus, in which this spine has undergone considerable modification, all show the characteristic anterior and posterior prongs. In Euphoberia and Acantherpestes the posterior spinelet is relatively prominent; in Myriacantherpestes ferox and M.bradebirksi it is very small, and even in the American species, where the anterior and posterior spinelets approach each other in size, the posterior spinelet is the smaller of the two. However, the major difference between Myriacantherpestes and the other two euphoberid genera lies in the total absence of the anterior spinelet in the latter two taxa.
Both Acantherpestes and Myriacantherpestes are discussed in the Richardson's Guide to the Fossil Fauna of Mazon Creek on page 177 in the Chapter "Myriapods and Arthropleurids".
Genus Acantherpestes
This large euphoberiid ranges in size to about 300 mm (12 in.). It bears lateral spines, lacking small anterior spines, and has simple paramedian spines. The holotype of Acantherpestes major (Meek and Worthen) has been restudied by Burke (1973) and is illustrated here as Figure 13.8. Many of the well-known specimens of A. major were removed from the genus Acantherpestes by the actions of Burke (1979) when he erected the new genus Myriacantherpestes.
Burke (1973, p. 22) hypothesized that "protected from most predators by sheer size, Acantherpestes was probably able to move about freely" and that it may have "ventured into open areas of the lowlands bordering the Carboniferous swamps." He also suggested that this form may have been carnivorous.
Genus Myriacantherpestes
This medium-sized to large euphoberiid has very long lateral spines, anterior spines, and simple paramedian spines or nodes. It can be distinguished from Euphoberia and Acantherpestes by the presence of anterior spines (Burke, 1979, p. 16). One of the largest species of this genus is Myriacantherpestes hystricosus (Scudder), which may have reached 300 mm (12 in.) in length.
Burke (1979) found this form to be adapted to a "bulldozer" function, akin to that of some modern millipedes that push through the leaf litter of forests. This is unlikely, however, as the large spines of the animal would have made this practically impossible (W. Shear, personal communication, 1992). It probably lived in more open habitats.
Myriacantherpestes appears on page 51 of Jack Wittry's "The Fossil Fauna of Mazon Creek".
Myriacantherpestes could reach 30 cm in length and, with their spines, over 4 cm wide. This animal was first described as being amphibious; its forked spines were considered to be used as paddles when needed. It now is thought that Myriacantherpestes likely lived in a more open terrestrial environment due to the fact that its spines were so prominent they easily could have become entangled in ground clutter.
Acantherpestes is another member of Euphoberiida that has been reportedly found in the Mazon Creek area. It is similar but lacks the anterior spines found only on Myriacantherpestes specimens. Many reported examples of Acantherpestes therefore needed to be reassigned after Myriacantherpestes was erected. The presence of valid examples of Acantherpestes in the Mazon Creek Fauna is now in doubt.
Specimens
Holotype of Acantherpestes major
From Witty, Myriacantherpestes
From Hamilton, Kansas - Paul Demkovich
From Hamilton, Kansas - Doug DeRosear
