Members of the Aspidorhynchidae, an extinct family of ray-finned fish (Actinopterygii) are amongst the most common larger predatory fish in the Late-Jurassic Solnhofen Archipelago. Aspidorhynchids from these localities have yielded specimens with prey fish stuck in their mouths and stomachs. We report here on isolated skulls and, in one case, a body fragment of Aspidorhynchus with attached gastrointestinal tract, whereas all other parts of the body of these specimens are missing.

These extraordinary fossils are probably feeding-remains left over by larger predators, apparently unique in the fossil record and even for the Solnhofen Archipelago something special that is hardly known. As proof that these diffuse appendices to the cranium are gastrointestinal tracts, we show here for the first time prey fish and, in one case, a crustacean visible in some of these gastrointestinal tracts.

ancient ecology, Aspidorhynchiformes, fish stomach or gut contents, fossilisation, soft body preservation, taphonomy

Aspidorhynchiformes Bleeker, 1859 with a single family, the Aspidorhynchidae Nicholson & Lydekker, 1889 are predatory Teleosteomorpha (Arratia 2001), which are known from the Jurassic (Aspidorhynchus Agassiz, 1833; Belonostomus Agassiz, 1834) to the Cretaceous (Vinctifer Jordan, 1920, Richmondichthys Bartholomai, 2004, Jonoichthys Gouiric-Cavalli, 2015 and Pseudovinctifer Arratia, 2015). The earliest records of Aspidorhynchus are from the Mid-Jurassic (Bathonian of Stonesfield Slate, Oxfordshire, England) and the genus became extinct in the Late Jurassic (last record: Purbeck of Swanage, Dorset, England) (Brito 1997).

In the larger (and deeper) Plattenkalk basins of Eichstätt and Solnhofen, Aspidorhynchus is amongst the most common larger predatory fish (approximately 4% of the total known fish fauna), reaching up to 1 m total length (Ebert 2024). In smaller basins of the Solnhofen Archipelago with close proximity to coral reefs (Ettling, Kelheim, Painten or Zandt) and in Cerin (France), the more slender genus Belonostomus is more common than Aspidorhynchus, but the latter is still present (Ebert 2024).

Aspidorhynchiformes are elongated fishes with comparatively large caudal fins. Together with their posteriorly positioned dorsal and anal fins, they must have been able to acquire high speed propulsion to catch their prey in open water (Kogan and Licht 2013). Apparently, Aspidorhynchus fed on small fish, which they swallowed whole, which unfortunately is rarely visible being obscured by the thick body squamation of the predator; at least in larger specimens of more than 20 cm. Whether or not Aspidorhynchus with their elongated premaxillae hunted like modern marlins can only be speculated, but it seems a reasonable assumption. Thus far, five specimens of the pterosaur Rhamphorhynchus have been found adjacent to the rostrum of large Aspidorhynchus specimens leading to the interpretation that the pterosaurs accidentally and fatally collided with large Aspidorhynchus during their hunt for smaller fish, both genera attacking fish shoals – the pterosaurs from above, Aspidorhynchus from below (Frey and Tischlinger 2012).

There are two distinct functional groups of piscivorous fishes, engulfers and grabbers, exhibiting different feeding strategies (Mihalitis and Bellwood 2021; Muruga et al. 2022). Engulfers (like the here described Aspidorhynchus) overwhelm their prey whole and head- first, whereas grabbers seize their prey tail-first and crippling or even killing it by means of vehement headshakes and bites. They then let go of their prey, recapture it and swallow it head first or process their prey by biting it into smaller pieces for ingestion (Muruga et al. 2022). Although thus far, we have no evidence of bite marks, we suggest that the isolated heads of Aspidorhynchus were detached from the body by such a grabber, possibly an ichthyosaur or a large shark. The most nutritious parts requiring the least amount of processing are eaten first, leaving the head, which may rapidly sink out of sight into the hostile bottom zone of the Plattenkalk basins. In modern fishing, the gastrointestinal tract remains attached to the skull when a special cut is used to separate the skull from the body; for example, in herring during traditional matjes (soused herring) production (Klinkhardt 2023) or for scientific gut contents analysis “cut the head at the dorsal connection with the spine then pull the head off and the guts come with it” (David Bellwood personal communication, 28 May 2025).

After death, fish guts tend to rot extremely quickly due to a combination of autolysis and bacterial decomposition. Thus, head and guts must have been separated from the rest of the carcass immediately after death – the process may indeed have been the cause of death, as argued above – and promptly sank into the hostile bottom zone of one of the Plattenkalk basins within the Solnhofen Archipelago where they were covered with sediment. Only when we have a hostile bottom zone and the dead bodies are reasonably quickly covered by sediment, soft body preservation – gastrointestinal tracts still attached to the skull – can be expected to be found. Soft body preservation is common in many Plattenkalk fossils especially in the Late Jurassic of the Solnhofen Archipelago. In Actinopterygii, we have preservation of skin, muscle fibres and in situ gastrointestinal tracts, including stomach and gut contents.

Prey items in the stomachs of fossil fishes are known from many localities worldwide (Viohl 1990, table 23). Wilby and Martill (1992, p. 25) even refer to fossil fish stomachs as “a microenvironment for exceptional preservation”.

However, all these fish stomachs have previously been described within complete fish (for Aspidorhynchus see examples below; for the smaller Aspidorhynchidae genus Belonostomus see Suppl. material 1: table S1). We now describe for the first time isolated skulls of Aspidorhynchus and, in one case, a feeding residue of the anterior body with attached gastrointestinal tract containing prey, whereas all other parts of the body of these specimens are missing.

Examples of Aspidorhynchus skulls with attached gastrointestinal tract

The first to report a specimen of Aspidorhynchus with attached gut was Walter (1904, p. 178) who mentioned that Aspidorhynchus was rare at Solnhofen, Langenaltheim and Daiting and “often only the head with attached intestine is preserved” (translated from German).

Unfortunately, we do not know to which particular specimens Walter (1904) was referring. Often, two strands of the gastrointestinal tract are visible (Figs 1A, 2, 6B,C). Possibly, this represents a large stomach that ends blindly posteriorly and a thinner intestinal canal that attaches to the anterior region of the stomach. A similar gastrointestinal tract is described by Nybelin (1958) for the Upper Jurassic teleost genus Thrissops.

Figure 1. 

Skull with attached gut of Aspidorhynchus acutirostris (SNSB-BSPG 1964 XXIII 140) from the Eichstätt Basin (Schernfeld), Bavaria, Germany with a folded, juvenile Eryonid, presumably Knebelia schuberti in the gut (G. Schweigert, pers. comm. Mai 2025). A. Complete Aspidorhynchus fragment; B. Enlargement of Eryonid in normal light; C. Enlargement of Eryonid in UV-light (photos M. Ebert).

Figure 2. 

Skull with attached gut of Aspidorhynchus acutirostris (SMF P6331a, b) from the Eichstätt Basin (Blumenberg), Bavaria, Germany with two prey fishes in the stomach. A, B. Part and counterpart of preserved fossil; C. Enlargement of prey fishes marked in the rectangular of Fig. 2A; D. Enlargement of the prey fish marked in the rectangle of Fig. 2B with rough sketch of the prey fish; E. Enlargement of the prey fish marked in the rectangle of Fig. 2B (photos M. Ebert).

Janicke and Schairer (1970) figured (fig. 7) one specimen of Aspidorhynchus (SNSB- BSPG 1964 XXIII2; see Fig. 6B) and mentioned a second (SNSB-BSPG 1964 XXIII140; Fig. 1), both from the collection in Munich.

“The Bavarian State Collection, Munich, owns two heads of Aspidorhynchus (1964 XXIII 2 and 140), with which narrow, tubular impressions are associated. These are evidently remnants of soft tissue that, during decomposition and decay, detached from the rest of the body along with the head. Near the point of detachment, food remains (Saccocoma, crustacean remains, fish remains) can still be seen. According to a kind verbal communication from Dr. F. Terofal, Bavarian State Collection, Munich, the appendages can be explained as pharynx and remnants of the intestinal tract” (Janicke and Schairer 1970, p. 458–459; translated from German). We have examined these specimens as part of the present study.

However, we have been unable to discern any Saccocoma in the gastrointestinal tract of these two specimens; only the crustacean residue can be confirmed in SNSB-BSPG 1964 XXIII140 and SNSB- BSPG 1964 XXIII 2 contains some microscopic phosphate residue which most likely represents incompletely digested fish remains.

Specimen SNSB-BSPG 1964 XXIII140 from Blumenberg (Eichstätt Basin) has indeed a food bolus containing a small crustacean in the gastrointestinal tract (Fig. 1A–C) and it is the only member of the Aspidorhynchidae thus far in which crustaceans have been identified as food. G. Schweigert interprets this small crustacean as a single folded, juvenile Eryonid (Fig. 1B, C), presumably Knebelia schuberti (pers. comm. May 2025). At present, we offer no explanation as to how or why a predator, normally hunting small fish, encountered this unusual dietary component. However, although adult Knebelia were benthic decapods, their juveniles may have been able to swim.

Amongst the unidentified specimens in Frankfurt, we found a cranium with attached gastrointestinal tract (SMF P6331a, b; Fig. 2A–E) from Blumenberg (Eichstätt Basin) with at least two small, juvenile Teleostei (probably Leptolepides sprattiformis) in the stomach. It is interesting to note that the dorsal curvature of the prey fish, caused by the more recalcitrant tendons of the neural arch, apparently can also occur under the harsher chemical conditions present during digestion in the stomach.

In CM 15784, a specimen from “Solnhofen” (Fig. 3A), at least three small, juvenile teleostei (probably Leptolepides sprattiformis) can be seen in the posterior stomach region (Fig. 3B, C). In the anterior stomach region, there are several fragmentary sections of connected vertebral centra and parts of fins from similar juvenile teleostei. All these prey fish are more or less in the process of disintegration due to progressed digestion. All these prey fish are of similar size, supporting the assumption that Aspidorhynchus was feeding on shoals of fish.

Figure 3. 

Skull with attached gut of Aspidorhynchus acutirostris (CM15784) from “Solnhofen”, Bavaria, Germany with at least three prey fishes in the stomach. A. Complete Aspidorhynchus fragment; B. Enlargement of the three prey fishes marked in the rectangular of Fig. 3A; C. Enlargement of the fishes marked in the rectangular of Fig. 3A with sketch of the three prey fish (photos A. A. McAfee; B, C. M. Ebert).

The same conditions are found in USNM PAL 182209 from “Solnhofen” (Fig. 4); here too there are several fragments of similarly disintegrating juvenile Teleostei.

Figure 4. 

Skull with attached gut of Aspidorhynchus acutirostris (USNM PAL 182209) from “Solnhofen”, Bavaria, Germany with multiple fragments of prey fishes in the stomach. A. Complete Aspidorhynchus fragment; B. Enlargement of prey fishes marked in the rectangular of Fig. 4A; C. Enlargement of the fish marked in the rectangle of Fig. 4A with sketch of remains of at least five prey fish (the photo in Fig. 4A was composed by us from two photos of M. Miller).

Further Aspidorhynchus skulls with attached gastrointestinal tract, but without clearly recognisable prey are CM 4745 from “Solnhofen” (Fig. 5A) and JME-SOS2835 from Eichstätt (Fig. 5B), both with obscure, largely dissolved food residues in the gastrointestinal tract. SNSB-BSPG 1964 XXIII 2 from Schernfeld (Fig. 6B) shows some microscopic phosphate residues which are most likely almost fully digested fish remains, whereas JME-SOS2807 from Blumenberg (Fig. 6A) and JME-SOS3422 from Eichstätt (Fig. 6C), both from the Eichstätt Basin, lack residues in the gastrointestinal tract.

Figure 5. 

Skull with attached gastric tract of Aspidorhynchus acutirostris from the Solnhofen Archipelago, Bavaria, Germany with unidentifiable prey remains in the intestine. A. CM 4745 from “Solnhofen”; B. JME-SOS2835 from Eichstätt (photos A. A. McAfee; B. M. Ebert).

Figure 6. 

Skull with attached gastric tract of Aspidorhynchus acutirostris from the Solnhofen Archipelago, Bavaria, Germany. A. JME-SOS2807 from Blumenberg (Eichstätt Basin); B. SNSB-BSPG 1964 XXIII 2 from Schernfeld (Eichstätt Basin); C. JME-SOS3422 from Eichstätt (photos M. Ebert).

Examples of anterior body fragment of Aspidorhynchus with prey fish in the attached gastrointestinal tract

At Museum Bergér, we found feeding remains consisting of a fragmentary skull and scales of the anterior body of a large Aspidorhynchus with a posteriorly attached gastrointestinal tract containing two prey fish (Fig. 7A). Both prey fish are most likely juvenile specimens of the genus Tharsis, with ~ 6 cm in total length (Fig. 7B). The anterior of the two fish still retains its body shape, whereas the posterior one is coiled and in the early stages of disintegration. Possibly, this represents two temporally separated feeding events and the prey fish, which was in the gastrointestinal tract for a longer duration of time, has been digested to a greater degree.

Figure 7. 

Feeding remains of a large Aspidorhynchus with a posteriorly attached gastrointestinal tract containing two prey fish from the Museum Bergér. A. Body fragment with attached gastrointestinal tract; B. Enlargement of the two prey fish (photos M. Ebert).

Examples of completely articulated Aspidorhynchus with prey fish in the stomach

In articulated, adult specimens of Aspidorhynchus the scales are normally too opaque to observe the stomach contents. Only in some rare examples of Aspidorhynchus when the prey fish in the stomach is particularly large (Fig. 8B, C) or parts of the scales of the predator have been removed, are we able to see prey fish in the gastrointestinal tract.

Figure 8. 

Aspidorhynchus acutirostris from “Solnhofen”, Bavaria, Germany with prey fish. A. Skull of GZG.RF.998 with a Pholidophorid stuck in the mouth; B. Complete specimen (GZG.RF.999) with Allothrissops in the stomach; C. Enlargement of rectangular in Fig. 7B (photos M. Ebert).

In the stomach of a 56 cm long Aspidorhynchus (GZG.RF.999) from Solnhofen (Fig. 8B), we found a 16 cm long Allothrissops in the stomach (Fig. 8C).

Additionally, interesting in this specimen is the settling mark in the sediment above the back, which shows that this specimen arrived on the substrate with its belly facing upwards and only then tipped to its side (see Mayr (1967)). JME-SOS3519 from Wintershof (Eichstätt Basin) has a Teleost in the stomach (probably a juvenile Tharsis dubius).

Two further specimens (SHT 80/114; SHT82/3) from Solnhofen with small Teleostei (probably juveniles of Leptolepides sprattiformis) in the stomach are mentioned in Viohl (1987, fig. 6; 1990, table 22). MHNL 20015801 from Cerin has approximately five juvenile Orthogonikleithridae (probably of Orthogonikleithrus francogalliensis Konwert, 2016) in the stomach.

We compared the preservation status of 343 Aspidorhynchus specimens in the Eichstätt and Solnhofen Basins of the Solnhofen Archipelago (Table 1). Fifty percent were embedded as complete specimens, 15% are specimens that have been collected incompletely, thus they may or may not have been embedded as complete specimens, whereas 35% were embedded as remains of feeding or fragments of decayed specimens.

Interestingly, 65% of these remains of feeding or decayed specimens are remains from the anterior part of the body. If we count only the isolated heads, it is still 46% (or 16% of all recovered specimens). This leads us to believe that predators preferentially ate the postcranial body of Aspidorhynchus, leaving the severed heads behind. Predators (probably ichthyosaurs, other larger marine reptiles or larger sharks) ripped or shook the head off, then ate the rest of the body. The heads would have either sunk too quickly out of sight or they were rejected intentionally by the predator, as it might have been difficult to safely swallow a large Aspidorhynchus skull with its long and pointed premaxilla.

There may also have been a particular weakness in the connection between cranium and first vertebrae in the genus Aspidorhynchus leading to the high percentage of isolated skulls. Janicke and Schairer (1970, p. 459) even refer to this body region in Aspidorhynchus as “locus minoris resistentiae”. Unfortunately, we were unable to identify the two Aspidorhynchus specimens with heads resting detached next to the body, described by Janicke and Schairer (1970) in the SNSB-BSPG collection in Munich.

Aspidorhynchiformes do not have fully ossified vertebral centra, even in adult specimens. Their vertebrae consist of half centra which are only connected by cartilage or other connective tissue.

The Solnhofen Archipelago is known for its excellent fish preservation, but little was known about prey in Aspidorhynchus whose stomach contents are normally covered by thick ganoid scales. In this paper, we figure prey in isolated gastrointestinal tracts of Aspidorhynchus for the first time, in one case, a small crustacean, in four cases, several small juvenile teleostei.

Additionally, we only know of five cases of complete Aspidorhynchus specimens with prey fish. One with an Pholidophorid stuck in the mouth, one with a comparably large Allothrissops in the stomach and three specimens with a small number of juvenile Teleostei in the stomach. For specimens of Upper Jurassic Aspidorhynchidae with prey, see Suppl. material 1: table S1.

The high number of at least 16% isolated skulls indicates that larger predators often detach the head before swallowing their prey. In ten documented cases, the gastrointestinal tract remained attached to the cranium, a phenomenon that can also be observed in recent fish.

The newly-discovered Aspidorhynchus fragments with attached gastrointestinal tract not only provide insight into feeding behaviour of the genus Aspidorhynchus as well as that of larger predators, but also gives further insight into the exceptional preservation conditions of the Plattenkalk of the Solnhofen Archipelago.

We would like to thank G. Bergér (MBH); D. Berthet and D. Besson (MHNL); R. Brocke (SMF); A. Gehler (GZG); A. Henrici, L. Church, S. Davis and M. Lamanna (CM); Ch. Ifrim (JME); O. Rauhut (SNSB-BSPG); M. Wilmsen (MMG-SNSD); F Witzmann (MB) for providing access to the described specimens and A. Gehler (GZG); A. McAfee (CM); A. Millhouse and M. Miller (USNM) and H. Tischlinger for photos of Aspidorhynchus specimens of their collections. Additional thanks go to D. Bellwood for literature and helpful discussions and to G. Schweigert (SMNS) for the determination of the crustacean. Finally, we want to thank the editor F. Witzmann and reviewer Ch. J. Duffin and one anonymous reviewer of the manuscript.