New Mexico Geological Society Annual Spring Meeting — Abstracts

Pulchrilamina is a principal component of the bioherms of the Early Ordovician McKelligon canyon Formation of the El Paso Group. It was first assigned in the late forties to the stromatolitic algae. Later workers not only excluded it from the stromatolitic algae but also the stromatoporoids. In the late sixties it was classified as an uncertain affinity organism assigned to the hydrozoans·of the coelenterate phylum. Webby, in a recent, excellent reanalysis of the taxon, places it clearly within the labechiid stromatolites of the Phylum Porifera. Samples for this study which were taken, in part, from the McKelligon Canyon stratotype include a selection from Lechuguilla Mound where Toomey (1967) collected the holotype (USNM 155300) and fourteen paratypes.

These Early Ordovician stromatoporoid sponge bioherms are observed to occur in nineteen cycles at the stratotype in the southern Franklin Mountains, El Paso County, Texas. The organism acts most effectively as a dominant, laminated binder (bindstone-boundstone) in the stressed climax stage. Similar occurrences of Pulchrilamina are recorded by Toomey and Hamm (1967) in the Kindblade Formation of the Early Ordovician Arbuckle Group PreChazyan-WhiteRock, between the Pulchrilamina occurrences and the well-developed Middle and Upper ordovician stromatoporoid, are reported from North China and Malaysia.