1186
Journal of Paleontology 91(6):1178–1198
Description.—Short, horizontal, bilobate trace consisting of few scratch marks (6–7) arranged transversely to the median furrow. Width is 23.8mm; maximum length preserved is 17.6mm. Preserved as positive hyporelief.
Remarks.—Rusophycus comprises several ichnospecies, including 21 listed just for the lower Cambrian (Mángano and Buatois, 2016); its type ichnospecies is Rusophycus biloba (Fillion and Pickerill, 1990). Rusophycus is distinguished from Cruziana by its length-to-width ratio; only specimens with the length-to-width ratio less than two are placed in Rusophycus (Keighley and Pickerill, 1996). The specimens analyzed here are similar to Rusophycus avalonensis Crimes and Anderson, 1985 because of the overall shape and the divided ridges, but the ridges are not arranged in bundles. Paleozoic marine Rusophycus are widely accepted as resting traces (cubichnia) made by trilobites (Osgood, 1970; Crimes, 1975).
Occurrence.—Upper Shale Member. Ichnogenus Treptichnus Miller, 1889
Remarks.—Treptichnus is a burrow consisting of segments connected at their ends, each one to the next, characteristically but not invariably in a zigzag pattern. At present, there are ten ichnospecies of Treptichnus: the type ichnospecies, T. bifurcus Miller, 1889; T. pedum (Seilacher, 1955); T. triplex Palij, 1976; T. coronatum (Crimes and Anderson, 1985); T. lublinensis Paczesna, 1986; T. pollardi Buatois and Mángano, 1993b; T. tripleurum (Geyer and Uchman, 1995); T. rectangularis Orłowski and Zylińska, 1996; T. meandrinus Uchman, Brom- ley, and Leszczyński, 1998; and T. apsorum Rindsberg and Kopaska-Merkel, 2005. Treptichnus is interpreted as feeding structures (fodinichnia) produced by vermiform animals or insect larvae, the latter in the case of non-marine occurrences (Uchman, 2005). Treptichnus has been recorded from non- marine (Buatois and Mángano, 1993a, 1993b; Buatois et al., 2000), marginal-marine (Archer and Maples, 1984; Buatois et al., 1998a), shallow-marine (Fedonkin, 1977; Geyer and Uchman, 1995), and deep-marine (Crimes et al., 1981; Uchman et al., 1998) environments. Treptichnus is considered to range in age from Cambrian to Holocene (Crimes, 1987; Geyer and Uchman, 1995; Muñiz-Guinea et al., 2014). However, reports of treptichnid trace fossils from terminal Ediacaran rocks in the Nama Group of Namibia and the GSSP section in Newfound- land suggest that Treptichnus may extend back into the late Ediacaran (Jensen et al., 2000; Gehling et al., 2001; Högström et al., 2013). Further work on the relationship between the so-called treptichnids and Treptichnus is pending.
Treptichnus pedum (Seilacher, 1955) Figure 5.1
Materials.—Five slabs (P3310.2, P3311.2, P3311.8, P3311.11, P3311.15,) containing nine specimens.
Description.—Straight or curved sets of individual burrows of similar length connected to one another at their lower parts. The burrows alternate in direction, forming a zigzag pattern; where
the burrows are arranged in a nearly straight succession, the segments generally are aligned, and the zigzag pattern is rarely developed. In curved portions of the burrow, the segments generally project outwards. Width is 2.9–6.7mm; maximum preserved length is 25.2mm. Preserved as positive hyporelief.
Remarks.—Treptichnus pedum was originally described as Phycodes pedum, but Osgood (1970) noted that P. pedum dif- fers from other ichnospecies of Phycodes, such as the type ich- nospecies Phycodes circinatum Richter, 1853, and that it merited a new ichnogeneric designation. Treptichnus pedum,as described by Seilacher (2007), includes straight, sinusoidal, curved, or looping burrows constructed from upward curving segments. Treptichnus pedum is a feeding burrow (Crimes et al., 1977) with several morphological variants (Seilacher, 2007), ranges in age from the early Cambrian to Holocene (Crimes et al., 1977; Muñiz Guinea et al., 2014), and is restricted to normal-marine salinity conditions (Buatois et al., 2013). There is general agreement that the T. pedum tracemaker was a motile bilaterian animal that lived below the sediment-water interface, propelling itself forward in upward curving projections that breached the sediment surface (Seilacher, 1955; Geyer and Uchman, 1995; Jensen, 1997; Dzik, 2005). Dzik (2005) argued that the T. pedum animal was a priapulid worm, a conclusion supported by Vannier et al. (2010) based on neoichnologic experiments. Although it is sometimes referred to as Tricho- phycus pedum (e.g., Geyer and Uchman, 1995; Peng et al., 2012a), the overall morphology of Trichophycus is remarkably different, consisting of a U-shaped burrow with a retrusive spreite (Mángano and Buatois, 2011). Treptichnus pedum has been reported as Trichophycus pedum from the Soltanieh Formation by CiabeGhodsi et al. (2006) and CiabeGhodsi (2007).
Occurrence.—Lower and Upper Shale members.
Treptichnus pollardi Buatois and Mángano, 1993b Figure 5.3
Materials.—Six slabs (P3318.1, P3311.6, P3311.16, P3311.18, P3311.20, P3313.01) containing ten specimens.
Description.—Horizontal, simple, straight burrows with knots or shafts at semi-regular intervals. Width is 1.3–4.6mm; indi- vidual segments length is 2.6mm. Spacing between segments is 7.5–15.9mm. The maximum number of burrow segments is six. Preserved as positive hyporelief.
Remarks.—Treptichnus pollardi is distinguished from T. bifurcus by the presence of surficial pits, absence of twiglike projections, more irregular pattern, and longer individual segments. Treptichnus pollard differs from T. lublinensis and T. triplex by the absence of terminations projecting past the zigzags, the presence of pits associated with the horizontal burrow segment, and its thinner segments (Buatois and Mángano, 1993b). Although distinction from the ichnogenera Saerichnites and Ctenopholeus may be unclear depending on preservation (e.g., Buatois and Mángano, 2004; Fürsich et al., 2006), the overall morphology of the Soltanieh Formation
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