25 Refining the Cambrian—Biotas, Multiproxy Correlations, Workable Global Divisions, and Paleogeography: Discussions in Honor of Fred Sundberg

Eumetazoan diversification and origin of relatively modern marine ecosystems make the Cambrian a key Phanerozoic interval. This session focuses on the correlation significance of improved chemostratigraphic, biostratigraphic, astrochronologic, atmospheric, and oceanic syntheses; geochronology; and new paleogeographic and paleoclimatologic work.

Sunday, 19 October 2025
8:00 AM - 12:00 PM
HBGCC, 305

Asaphiscus and Glyphaspis, iconic Laurentian middle Cambrian macropygous ptychopariids, are not congeneric; and, Blainia is not their senior synonym. Classical typology is sometimes necessary, even in the age of cladistics

Paper number: 25-4
Program: Technical Sessions
Time: 8:55 AM – 9:10 AM

Authors

Abstract

Three macropygous, middle Cambrian (Miaolingian) ptychopariid genera: Asaphiscus and Glyphaspis, respectively from the Marjuman Wheeler Shale in Utah and the Topazan Wolsey Shale in Montana; and Blainia, from Marjuman beds in the Conasauga Formation in Alabama, were placed in synonymy by Bordonaro et al. (2013). This taxonomic revision was based on morphologically variable specimens from the Precordillera of Argentina, which were claimed to incorporate the range of morphologies of species attributed to these three Laurentian genera. The same revision also erected Blainia as the senior synonym.  It will be shown here that: whereas Asaphiscus and Blainia are, in fact, congeneric, but with Asaphiscus the senior synonym by publication precedence; the generotype species Glyphaspis capella is morphologically and temporally distinct from holotypical Asaphiscus wheeleri and Blainia gregaria.  Much of the taxonomic complication stems from the literal dozens of species referred to Glyphaspis, not all of which may be correct and obscure the original generic concept; as well as preservational issues in the type series of Blainia and the use of incomplete individuals in the attempt at taxonomic revision.

New specimens from localities proximal and correlative to the type locality for Blainia gregaria reveal that one notable morphology featured in both Walcott (1916) and Bordonaro et al. (2013), a medial pygidial notch, is completely absent in better specimens. In addition, new, complete specimens of Glyphaspis capella from the Conasauga Formation in Georgia, show numerous morphologies notably distinct from any referred species of Asaphiscus or Blainia; including much wider pygidia borders,  subcircular rather than ogival pygidial margin, elongate rather than absent or very short genal spines, and significantly larger size. The synonymy of these three common genera also obscures their separate chronostratigraphic occurrences, with Glyphaspis capella in the Topazan, whereas holotypical Asaphiscus wheeleri and Asaphiscus (Blainia) gregarius come from the Marjuman. Correctly classified, these are biostratigraphically significant diferences.    

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412723

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