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.

厚壳菊石属（厚壳菊石亚属）Anapachydiscus (Anapachydiscus) haegerti 新种（Anapachydiscus (Anapachydiscus) haegerti n. sp.）隶属于厚壳菊石科（Pachydiscidae），此次为该物种首次在不列颠哥伦比亚省霍恩比岛的坎潘阶上部（upper Campanian）诺森伯兰组（Northumberland Formation）中被报道。本次研究基于35件标本，完成了该类群完整的个体发育重建（ontogenetic reconstruction），同时针对尸积群（thanatocoenosic，即死亡组合death assemblage）开展观察，为菊石早期生活史的古生态学研究提供了参考依据。尽管存在孤立的幼年标本，但产出包含大量个体的结核是该物种的典型特征。一件产出26枚早期幼年个体的结核，支持其保存模式反映了生物在生活状态下形成的群落组合，即经历捕获与埋藏的埋藏学过程。该新种作为软体动物组合（molluscan assemblage）中的特征化石，在Nostoceras (Didymoceras?) adrotans区域亚带中具备年代地层诊断价值；该亚带是北太平洋东部坎潘阶上部的一个高度限定的地层间隔。本文还描述了一件产自登曼岛锡达区组（Cedar District Formation）坎潘阶上部的、被归为厚壳菊石属（厚壳菊石亚属）比较型Anapachydiscus (Anapachydiscus) cf. A. (A.) fascicostatus的标本，并对厚壳菊石属（Anapachydiscus）的鉴别特征进行了修订。通过新增的标本收藏，学界对厚壳菊石属（厚壳菊石亚属）Pachydiscus (Pachydiscus) hornbyense与厚壳菊石属（厚壳菊石亚属）Pachydiscus (Pachydiscus) ootacodensis的认知得到修正，厘清了这两个物种内的形态变异谱系。鉴于后一分类单元的地方性分布局限，本文提议在北太平洋东部建立坎潘阶上部P. (P.) ootacodensis-厚壳菊石属（厚壳菊石亚属）Pachydiscus (Pachydiscus) suciaensis共存延限带（concurrent-range Zone），以助力更大范围的跨区域生物地层对比（biostratigraphic correlation）工作。