Regurgitalites – a window into the trophic ecology of fossil cephalopods

Abstract

Fossil oral ejecta that exclusively contain bivalved calcitic lower jaws of ammonites (=aptychi) from Late Jurassic Solnhofen-type deposits of southern Germany are described. Based on the symphysis length of aptychi the ammonite shell diameters were reconstructed, ranging from 5 to 170 mm. To identify the potential ammonite predator published reports on stomach contents, coprolites and ammonite-palaeopathology were critically assessed. Implementation of the actualistic approach, together with some functional considerations, includes the identification of modern cephalopod predators with a focus on the modern Nautilus , and the distribution of vomiting behaviour among them. Stomach fluid pH is also important because species with an alkaline stomach pH are unable to dissolve calcareous hardparts and have to orally eject such material. Herein, we regard coleoids with an opportunistic diet as the most likely producers of the aptychi-bearing regurgitalites. This is based on finds of aptychi in the stomachs of the two coleoids Plesioteuthis and Trachyteuthis. They were likely fast, highly manoeuvrable swimmers. Both share a strong, triangular-shaped jaw apparatus that could possibly crush ammonite shells as well as arms equipped with suckers to hold their prey. Circumstantial evidence for coleoids as the producers comes from the alkaline pH of the stomach fluids of modern coleoids. Supplementary material: Data for lamellaptychi are available at https://doi.org/10.6084/m9.figshare.c.4695002

Bromalites from the Upper Triassic Polzberg section (Austria); insights into trophic interactions and food chains of the Polzberg palaeobiota

“…Cephalopods and arthropods noted from Polzberg section appear to be too small to produce these bromalites. Furthermore, these invertebrates have a rather alkaline gastric pH, and thus they produce regurgitates commonly containing specific hardparts (e.g., aptychi of ammonites) without etching-related features 43 .…”

“…There is evidence that Palaeozoic and Mesozoic shelled cephalopods have been preyed upon by sharks and actinopterygian fishes 41,[43][44][45] . Noteworthy, Recent sharks and actinopterygian fishes are known to attack on Nautilus 46 .…”

Pterosaurs ate soft-bodied cephalopods (Coleoidea)

“…A large number of taxa from the Solnhofen Archipelago, including 'fishes' and marine reptiles, supposedly fed on aquatic organisms such as cephalopods 4,9,[49][50][51][52] . The conical, slender and recurved shape of the tooth excludes several groups of fish and reptiles as possible culprits.…”

Can Cephalopods Vomit? Hypothesis Based on a Review of Circumstantial Evidence and Preliminary Experimental Observations

“…Additional indirect support for our hypothesis comes from a paper, published while this paper was initially under review, analyzing fossilized regurgitalites (orally ejected stomach contents) containing aptychi (calcitic lower jaws of ammonites) from 1 https://youtu.be/0tFz2ppx_DY; https://youtu.be/c02EZcjWNSE late Jurassic Solnhofen deposits (Hoffmann et al, 2019). From a detailed study of the regurgitalites, data on fossilized cephalopod digestive tract contents and other fossils found in the same or related deposits, the authors built a case (using some of the same literature reported here) that coleoid cephalopods and most likely vampyropods were the predators responsible for the origin of the regurgitated ammonite remains.…”