Detailed examination of bicuspid hooks in Hoploscaphites cf. nebrascensis using µCT and neutron tomography
Hausmann IM, Schulbert C, Schillinger B, Matouskova J, Achterhold K (2026)
Publication Language: English
Publication Type: Conference contribution, Abstract of lecture
Publication year: 2026
Pages Range: 181
Conference Proceedings Title: Paleo4Alps 2026: Joint Meeting of the Italian, German, Austrian and Swiss Paleontological Societies – Book of Abstracts
Event location: Bozen
Abstract
Direct evidence of ammonoid brachial crowns has never been found. The only indication are hook-like structures found associated with scaphitid ammonites. They are thought to have functioned as grasping structures on tentacular clubs and therefore allow first insights into the brachial crown organisation of scaphitids. These hooks have been intensively studied in the species Rhaeboceras halli and are also known and described in the genus Hoploscaphites. Hooks in R. halli consist of variable morphological types which differ from those in Hoploscaphites and it is thought that Hoploscaphites hooks are very similar to each other in morphology and size. However, detailed analyses as in R. halli are still missing for Hoploscaphites. Therefore, we are examining a well preserved specimen of Hoploscaphites cf. nebrascensis using a complementary approach of µCT and neutron tomography data. The fossil is from the Late Cretaceous Pierre Shale Formation deposited in the Western Interior Seaway and was collected in Meade County (South Dakota, USA). It is a macroconch measuring c. 14 cm in maximum extent. Some of the embedded hooks are visible in the broken body chamber. Tomography data are currently being investigated and preliminary results show that around 20 hooks are contained, many of them fully hidden by sediment. Since the body chamber is incomplete, an originally higher number of hooks can be expected. All hooks are hollow structures with a wall thickness of approximately 200 µm. They consist of a round open base and two cusps which are bent into one direction. Size and morphology are more variable than previously thought and will be described using landmark analysis. Hook size can differ by approximately a factor of five. Although generally both cusps on a single hook bend in the same angle from the base to one direction, we also found in one hook different bending angles of the cusps.
Authors with CRIS profile
Involved external institutions
Technische Universität München (TUM)
Germany (DE)
Staatliche Naturwissenschaftliche Sammlungen Bayerns (SNSB)
Germany (DE)
Czech Technical University in Prague / České vysoké učení technické v Praze
Czech Republic (CZ)
Germany (DE)
Staatliche Naturwissenschaftliche Sammlungen Bayerns (SNSB)
Germany (DE)
Czech Technical University in Prague / České vysoké učení technické v Praze
Czech Republic (CZ)
How to cite
APA:
Hausmann, I.M., Schulbert, C., Schillinger, B., Matouskova, J., & Achterhold, K. (2026, July). Detailed examination of bicuspid hooks in Hoploscaphites cf. nebrascensis using µCT and neutron tomography. Paper presentation at Paleo4Alps 2026, Bozen, IT.
MLA:
Hausmann, Imelda M., et al. "Detailed examination of bicuspid hooks in Hoploscaphites cf. nebrascensis using µCT and neutron tomography." Presented at Paleo4Alps 2026, Bozen Ed. Evelyn Kustatscher, Gianmarco Tavilla, Marie Hörnig, Vanessa Roden, Camilla Wellstein, 2026.
BibTeX: Download