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
Data files
Jul 09, 2025 version files 6.59 MB
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McLachlan_Supplementary_Data.pdf
2.04 MB
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Mclachlan_Supplementary_Data.xlsx
38.62 KB
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README.md
4.51 MB
Abstract
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.
https://doi.org/10.5061/dryad.qz612jmsg
Description of the data and file structure
Files: McLachlan_Supplementary_Data.pdf
Description: This file encloses all supplementary data associated with the following publication: McLachlan, S.M.S., 2025, 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. Journal of Paleontology. DOI: https://doi.org/10.1017/jpa.2025.10105
Page 1
Figures 1.1–1.3 — Sutural geometry tracings and measurements pertaining to the three ammonite species Anapachydiscus (Anapachydiscus) haegerti n. sp., Pachydiscus (Pachydiscus) hornbyense, and Pachydiscus (Pachydiscus) ootacodensis.
Figures 2.1–2.2 — Photograph and illustration of Anapachydiscus (Anapachydiscus) haegerti n. sp. conch cross-section.
Page 2
Table 1.1 — Specimen measurements and morphometrics for Anapachydiscus (Anapachydiscus) haegerti n. sp.
Table 1.2 — Specimen measurements and morphometrics for Anapachydiscus (Anapachydiscus) cf. A. (A.) fascicostatus (Yabe and Shimizu, 1926).
Table 1.3 — Specimen measurements and morphometrics for Pachydiscus (Pachydiscus) hornbyense Jones, 1963.
Page 3
Table 1.4 — Specimen measurements and morphometrics for Pachydiscus (Pachydiscus) ootacodensis (Stoliczka, 1865).
Page 4
Legend
n/a = data not available; e = estimate; ex = extrapolation; vol = volution; * = holotype; measurements given in mm. Conch morphometric indices follow those of Korn (2010).
Abbreviations: D = whorl volution diameter; Uw = umbilical width; UWI = umbilical width index obtained from Uw/D; CWI = conch width index calculated from Ww2/D; Wh = whorl height (umbilical margin to mid-venter); VX = vertical conch expansion rate determined from Wh2/Wh1; Ww = whorl width (flank to flank); LX = lateral conch expansion rate derived from Ww2/Ww1; WWI = whorl width index established from Ww/Wh; RI = rib index; the prominent rib count per one half volution between Wh1 and Wh2; FDI = suture fractal dimension index after Marriott and Chamberlain Jr. (2021).
Institutional Abbreviations: CDMPC: Courtenay and District Museum and Palaeontology Centre, Courtenay, BC, Canada; GSC: Geological Survey of Canada, Vancouver, BC, Canada; RBCM: Royal British Columbia Museum, Victoria, BC, Canada; NMNH: Smithsonian National Museum of Natural History, Washington, DC, USA
References
Jones, D.L., 1963, Upper Cretaceous (Campanian and Maestrichtian) ammonites from southern Alaska: United States Geological Survey Professional Paper, v. 432, p. 1–53, 41 pls.
Korn, D., 2010, A key for the description of Palaeozoic ammonoids: Fossil Record, v. 13, p. 5–12.
Lutz, T., and Boyajian, G., 1995, Fractal geometry of ammonoid sutures: Paleobiology, v. 21, p. 329–342.
Marriott, K., and Chamberlain Jr., J.A., 2021, Uses for incomplete ammonite sutures: Lateral lobe and second saddle as markers of sutural complexity: Geosciences, v. 11, 476.
Stoliczka, F., 1863–1866, The fossil Cephalopoda of the Cretaceous rocks of southern India. Ammonitidae with revision of the Nautilidae etc: Memoirs of the Geological Survey of India, v. 1; Palaeontologica Indica, v. 3, (1), p. 41–56 (1863), (2–5), p. 57–106 (1864), (6–9), p. 107–154 (1865), (10–13) p. 155–216 (1866).
Yabe, H., and Shimizu, S., 1926, A study of the genus “Parapachydiscus” Hyatt: Proceedings of the Imperial Academy of Japan, v. 2, p. 171–173.
Files: McLachlan_Supplementary_Data.xlsx
Description: This file encloses all supplementary data tables associated with the following publication: McLachlan, S.M.S., 2025, 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. Journal of Paleontology. DOI: https://doi.org/10.1017/jpa.2025.10105
Table 1.1 — Specimen measurements and morphometrics for Anapachydiscus (Anapachydiscus) haegerti n. sp.
Table 1.2 — Specimen measurements and morphometrics for Anapachydiscus (Anapachydiscus) cf. A. (A.) fascicostatus (Yabe and Shimizu, 1926).
Table 1.3 — Specimen measurements and morphometrics for Pachydiscus (Pachydiscus) hornbyense Jones, 1963.
Table 1.4 — Specimen measurements and morphometrics for Pachydiscus (Pachydiscus) ootacodensis (Stoliczka, 1865).
Legend
n/a = data not available; e = estimate; ex = extrapolation; vol = volution; * = holotype; measurements given in mm. Conch morphometric indices follow those of Korn (2010).
Abbreviations: D = whorl volution diameter; Uw = umbilical width; UWI = umbilical width index obtained from Uw/D; CWI = conch width index calculated from Ww2/D; Wh = whorl height (umbilical margin to mid-venter); VX = vertical conch expansion rate determined from Wh2/Wh1; Ww = whorl width (flank to flank); LX = lateral conch expansion rate derived from Ww2/Ww1; WWI = whorl width index established from Ww/Wh; RI = rib index; the prominent rib count per one half volution between Wh1 and Wh2; FDI = suture fractal dimension index after Marriott and Chamberlain Jr. (2021).
Institutional Abbreviations: CDMPC: Courtenay and District Museum and Palaeontology Centre, Courtenay, BC, Canada; GSC: Geological Survey of Canada, Vancouver, BC, Canada; RBCM: Royal British Columbia Museum, Victoria, BC, Canada; NMNH: Smithsonian National Museum of Natural History, Washington, DC, USA
References
Jones, D.L., 1963, Upper Cretaceous (Campanian and Maestrichtian) ammonites from southern Alaska: United States Geological Survey Professional Paper, v. 432, p. 1–53, 41 pls.
Korn, D., 2010, A key for the description of Palaeozoic ammonoids: Fossil Record, v. 13, p. 5–12.
Marriott, K., and Chamberlain Jr., J.A., 2021, Uses for incomplete ammonite sutures: Lateral lobe and second saddle as markers of sutural complexity: Geosciences, v. 11, 476.
Stoliczka, F., 1863–1866, The fossil Cephalopoda of the Cretaceous rocks of southern India. Ammonitidae with revision of the Nautilidae etc: Memoirs of the Geological Survey of India, v. 1; Palaeontologica Indica, v. 3, (1), p. 41–56 (1863), (2–5), p. 57–106 (1864), (6–9), p. 107–154 (1865), (10–13) p. 155–216 (1866).
Yabe, H., and Shimizu, S., 1926, A study of the genus “Parapachydiscus” Hyatt: Proceedings of the Imperial Academy of Japan, v. 2, p. 171–173.