First discovery of the soft‐body imprint of an Oligocene fossil squid indicates its piscivorous diet

Abstract

The first well-preserved soft-body imprint of a fossil squid was discovered from the Lower Oligocene of the Krasnodar region, Russia. The squid is perfectly preserved, with many details of its body available for study, such as imprints of eyes and head, a pair of statoliths, jaws, and stomach contents. Statoliths of this squid are the first finds of in situ statoliths in fossil non-belemnoid coleoids, and their shape is characteristic of the genus Loligo (family Loliginidae). Although some Mesozoic coleoids were previously classified as teuthids, these finds remain controversial and the squid described herein is the first unquestionable representative of fossil Teuthida known to date. It should be noted that the squid is preserved not due to phosphatization, which is typical for fossil coleoids, but by pyritization and carbonization. Numerous fish remains in the stomach contents of the squid indicate its piscivorous diet. A small cutlassfish Anenchelum angustum, which was buried together with the squid and whose bones are located near the squid's jaws, sheds light on the circumstances of the death of this animal. Most likely, the squid suffocated in the anoxic bottom waters, where it drowned along with its last prey (distraction sinking).

‘Arm brains’ (axial nerves) of Jurassic coleoids and the evolution of coleoid neuroanatomy

“…The different facies and palaeogeographic setting of the La Voulte-sur-Rhône and Solnhofen regions reflect the contrasting depositional depths of the two localities: the complex bathymetry and mix of habitats at La Voulte-sur-Rhône, and the shallow platy limestones of the Solnhofen region were laid down in shallower water. In turn, this suggests a certain diversity in habitat depths of extinct vampyromorphs (e.g., Košťák et al, 2021 ; Klug et al, 2021b ), which is not surprising taking the higher diversity of Jurassic vampyromorphs (about four families with ten genera; see Fuchs et al, 2020 ) as opposed to the single living species into account.…”

“…Remains of arms and axial nerve cords were also discovered in other Fossillagerstätten such as the English sites of Christian Malford (Middle Jurassic), and the Late Jurassic coastline (this paper) or the Cenomanian of Lebanon (Larson et al, 2010 : figs. 3B and 5I) and, without axial nerves, in the Oligocene of Russia (Mironenko et al, 2021 ).…”

Anatomy and size of Megateuthis, the largest belemnite

“…Scarce direct evidence for belemnoid diet has been provided in recent years by Klaschka (2018), Jenny et al (2019), Hart et al (2020 and Klug et al (2021). In these cases, belemnoids have fishes and crustacean remains in their arm crowns (for a younger record of a coleoid catching a fish see Mironenko et al, 2021). In the upper Kimmeridgian Plattenkalk (platy limestone) of Nusplingen, an accumulation of small bitten aptychi (calcitic lower jaw element of ammonites) was associated with a belemnite rostrum and fossilized ink and is interpreted as its stomach content (Schweigert, 2018).…”