118 65


Journal of Paleontology 91(1):116–145 CAPE MANNING ? 60 55 ? cf. 50


S. turriculatus zones (lower Telychian) (e.g., Bouček andMünch, 1944;Münch, 1952; Schauer, 1971;Hutt, 1974; Bjerreskov, 1975; Rickards, 1976; Chen, 1984; Ge, 1990; Tomczyk et al., 1991; Loydell, 1993; Lenz et al., 2003), although Zalasiewicz et al. (2009) recorded a possible occurrence of Pseudoplegmatograpus from the S. sedgwickii Zone in UK (based on Hutt, 1974), and occurrences in the Stimulograptus halli Zone (uppermost Aeronian), continuing into the lower Telychian. In addition, Lenz (1982) reported Pseudoplegmatograptus obesus from the S. sedgwickii Zone in northwestern Canada, as well as a single unillustrated specimen assigned to P.cf. obesus from the L. convolutus Zone. Pseudoplegmatograptus obesus occurs in the lower


45


Telychian S. guerichi Zone in Arctic Canada and is, thus far, the only species of this genus recognized from the lower-mid Telychian strata in that region. We also report the occurrence of an incompletely preserved, unnamed species questionably assigned to Pseudoplegmatograptus in the L. convolutus Zone in Arctic Canada. Two other species of this genus were reported from the


40 m


interbedded calcareous shale and thin-bedded limestone


interbedded dolomitic shale and thin-bedded dolostone


carbonate concretion


med.-bedded dolostone


Figure 3. Lithological log through the upper Rhuddanian to mid-Aeronian part of the Cape Manning section, Cornwallis Island, showing graptolite zonation and stratigraphic levels of occurrence of graptolite taxa referred to in this study. Dashed line indicates approximate stratigraphic level of taxon occurring in an unmeasured reconnaissance sample collected at this locality (see Appendix 1).


Kozłowska-Dawidziuk, 2004, fig. 1), the previously known occurrence data summarized here point to the fact that this genus appeared within the lower Aeronian, but not at its base, and was relatively common in at least the mid and upper Aeronian globally. Our new data demonstrate that the Arctic Canadian


sequence yields several species of Pseudoretiolites occurring in the upper part of the lower and the mid Aeronian. In addition, we document one unnamed species assigned to Pseudoretiolites? from the lower Aeronian. It appears therefore, that Arctic Canada may be the only region globally where retiolitines can be confidently recognized from lowest Aeronian strata. Unfortunately, because only the early developmental stages of these earliest Arctic specimens are well preserved, positive determination of the genus and species is not possible.


Pseudoplegmatograptus.—The second long-known and globally widespread genus of the Aeronian-lower Telychian is Pseudoplegmatograptus Příbyl, 1948. This genus has been most commonly reported from strata no lower than the S. guerichi or


uppermost Telychian by Melchin (1989), although one of those species, Pseudoplegmatograptus giganteus, was named as the type species of a new genus, Giganteograptus, by Lenz and Kozłowska (2007). Li (1995) reported two species of Pseudoplegmatograptus


from strata assigned to the Coronograptus cyphus Zone in China. Although this zone is normally considered to be upper Rhuddanian in age, the co-occurrence of species of Petalolithus and Rastrites along with retiolitines indicates that at least part of this zone is Aeronian (but not lowest Aeronian) in age. Chen and Lin (1978) also reported specimens of Pseudoplegmatograptus from the lower Aeronian in China. Illustrations of the material assigned to Pseudoplegmatograptus by both Li (1995) and Chen and Lin (1978) show that the specimens are incomplete and not well preserved and they could represent specimens of Pseudoretiolites rather than Pseudoplegmatograptus (Loydell, 1993). Further study of these specimens is required.


Eorograptus.—Eorograptus Sennikov, 1984 was originally described from strata of the Spirograptus minor (=S. guerichi) Zone in Siberia (Sennikov, 1976, 1984). A new species of this genus is now recorded herein from the L. convolutus Zone in Arctic Canada.


Rotaretiolites.—Rotaretiolites, first identified as “Retiolites sensu lato sp.” by Hutt et al. (1970, pl. 1, figs. 19, 20) from Swedish material, was later named and described by Bates and Kirk (1992), based on different specimens from the same Swedish locality. This genus was subsequently illustrated from


Arctic Canada (see Kozłowska-Dawidziuk and Lenz, 2001, fig. 3.11). All reports of this genus, including the present material, are from the S. guerichi-S. turriculatus zonal interval.


Other taxa.—In this paper, we document one (possibly two) species of a new genus, Aeroretiolites, from the L. convolutus Zone, which bears many close morphological similarities with Rotaretiolites, and the two genera may represent part of the same lineage (see Phylogenetic analysis, below).


Rhuddanian cyphus


pectinatus- triangulatus


curtus orbitus convolutus


Aeronian


Hercograptus introversus Pseudoretiolites? sp. Pseudoretiolites decurtatus Pseudoretiolites hyrichus


Aeroretiolites cancellatus Aeroretiolites? sp.


Pseudretiolites cf. tianbaensis Pseudoretiolites perlatus Eorograptus spirifer


Pseudoplegmatograptus? sp. Paraplectograptus? sp.


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