Showing papers by "Per Ahlberg published in 2008"

Furongian Series (Cambrian) biostratigraphy of Scandinavia - a revision

Abstract: The Cambrian System is currently undergoing substantial revisions with regards to its biostratigraphy and chronostratigraphy. This is evident in the recent ratification of the Cambrian Furongian Series, the Paibian Stage (Peng et al. 2004), the Drumian Stage (Babcock et al. 2004, 2007), and international agreement on a chronostratigraphic framework comprising four series and ten stages, as opposed to the traditional tripartite subdivision (Fig. 1; Babcock et al. 2005; Peng et al. 2006; Zhu et al. 2006). The overall program of the International Subcommission on Cambrian stratigraphy is to develop a global stage-level chronostratigraphic framework for the whole Cambrian System. This is welcome but obviously requires that regional stratigraphic schemes (Babcock et al. 2007) be revised.

Bradoriid Arthropods from the Lower-Middle Cambrian of Scania, Sweden

Abstract: Three species of bradoriid arthropods from the lower to middle Cambrian transitional interval of Scania, southern Sweden, are described and illustrated: Beyrichona tinea from the top of the traditional lower Cambrian (Gislov Formation; Ornamentaspis? linnarssoni Zone), and Hipponicharion eos and Alutella sp. from the basal portion of the traditional middle Cambrian (lowermost part of the Alum Shale Formation). The bradoriid fauna compares most closely with others previously described from western and eastern Avalonia (New Brunswick and England). The record of B. tinea suggests a correlation between the “Protolenus Zone” (Hupeolenus Zone) of western Avalonia and the O.? linnarssoni Zone of Scandinavia. Hipponicharion eos appears to be a fairly long-ranging species as it has previously been recorded from upper lower Cambrian or lower middle Cambrian strata in New Brunswick, Poland, and probably Sardinia. The record of H. eos from the lowermost part of the Alum Shale Formation suggests that this largely unfo...

Iconography : Taxonomy of Ptychagnostus atavus : A key trilobite in defining a global Cambrian stage boundary

Abstract: The taxonomy of Ptychagnostus atavus (Tullberg, 1880) and Ptychagnostus intermedius (Tullberg, 1880) has been confused, in part at least, because of inadequate or erroneous illustrations of specimens from syntype series. From further examination and new illustrations we conclude that those series are conspecific and that P. atavus is the senior synonym of P. intermedius. Laurentian agnostoids previously assigned to P. intermedius are reassigned to Ptychagnostus sinicus Lu, 1957. As revised, P. atavus is a common, globally distributed species in open-marine lithofacies. Clarification of its taxonomy is important because its first appearance datum (FAD) will likely define the base of a new global Cambrian stage.