A. parallelus is smaller (narrower) than most other Arthrophycus (3.5–4.5 mm for A. parallelus vs. 10–20 mm for other Arthrophycus; Table 2), but falls within the upper range given for A. minimus (1.8–4.8 mm) recently described by Mángano et al. (2005). A. parallelus differs from A. minimus in having a more restricted range in trace width. A. parallelus also has much wider, more pronounced annulations that are clearly visible to the unaided eye, in contrast to the annulations of A. minimus that are “most visible under magnification” (Mángano et al., 2005, p. 182). Seilacher (2007) distinguished Arthrophycus from Phycodes on the basis of size (diameter) and stratigraphic range. He characterized Arthrophycus burrows as centimeters in diameter and Phycodes as a few millimeters, and noted that Phycodes appeared to be restricted to the Ordovician. On this basis he informally referred A. minimus to Phycodes. However, neither size nor geologic age are reliable ichnotaxobases (Bertling et al., 2006; Bertling, 2007), and the typical Phycodes morphology takes the form of broom-like branching from a central burrow and in that way differs significantly from typical Arthrophycus morphology. Therefore, we endorse Mángano et al. (2005) in their original assignment of their specimen to Arthrophycus, and we consider both A. minimus and A. parallelus to represent valid ichnospecies of Arthrophycus that are significant in extending the size range of this ichnogenus to include millimeter-diameter burrows.
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Full reference: D.S. Brandt, M. Seitz, V. McCoy, J. Csonka, J. Barringer, E. Holmquist, S. Kraig, R. Morgan, J. Myers and L. Paquette. 2010. A new ichnospecies of Arthrophycus from the Late Carboniferous (Pennsylvanian) of Michigan, USA. Ichnos 17:12-19
Belongs to Arthrophycus according to D.S. Brandt et al. 2010
Sister taxa: Arthrophycus brongniartii, Arthrophycus harlani, Arthrophycus lateralis, Arthrophycus minimus
Type specimen: UMMP 73822
Distribution: found only at Eaton Rapids ( of Michigan)
Specimen images are retrieved through the ePANDDA API.
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