Supplementary data from: Additions and revisions to the inflated Pachydiscidae from the Campanian (Upper Cretaceous) strata of Denman and Hornby islands, British Columbia, Canada; taxonomic implications and insights into mode of life

Anapachydiscus (Anapachydiscus) haegerti n. sp., an ammonite belonging to
the Pachydiscidae, is reported for the first time from the upper Campanian
Northumberland Formation of Hornby Island, British Columbia. Thirty-five
specimens have allowed for the complete ontogenetic reconstruction of the
taxon as well as thanatocoenosic (death assemblage) observations with
paleoecological implications for ammonoid early life. Although isolated
juvenile specimens occur, instances of concretions containing a multitude
of individuals are typical. One concretion yielding twenty-six early-stage
juveniles lends support to a mode of preservation reflective of life
association through a taphonomic process of capture and burial. The new
species presents age-diagnostic utility as a distinct fossil within the
molluscan assemblage of the Nostoceras (Didymoceras?) adrotans regional
subzone; a highly constrained interval of the upper Campanian in the
eastern North Pacific. A specimen attributed to Anapachydiscus
(Anapachydiscus) cf. A. (A.) fascicostatus from the upper
Campanian of the Cedar District Formation on Denman Island is also
described, and the genus Anapachydiscus is retained with an emended
diagnosis. Additional collections have enabled revised conceptualizations
of Pachydiscus (Pachydiscus) hornbyense and Pachydiscus (Pachydiscus)
ootacodensis, accounting for the spectrum of variance within these
species. Recognition of an upper Campanian P. (P.)
ootacodensis-Pachydiscus (Pachydiscus) suciaensis Concurrent-range Zone is
proposed for the eastern North Pacific to assist broader efforts of
interregional biostratigraphic correlation given the endemic limitation of
the latter taxon.