Fauna and Predator-Prey Relationships of Ettling, an Actinopterygian Fish-Dominated Konservat-Lagerstätte from the Late Jurassic of Southern Germany

The newly recognized Konservat-Lagerstätte of Ettling (Bavaria), field site of the Jura-Museum Eichstätt (JME), is unique among Late Jurassic plattenkalk basins (Solnhofen region) in its abundant, extremely well preserved fossil vertebrates, almost exclusively fishes. We report actinopterygians (ginglymodins, pycnodontiforms, halecomorphs, aspidorynchiforms, “pholidophoriforms,” teleosts); turtles; and non-vertebrates (echinoderms, arthropods, brachiopods, mollusks, jellyfish, sponges, biomats, plants) in a current faunal list. Ettling has yielded several new fish species (Bavarichthys incognitus; Orthogonikleithrus hoelli; Aspidorhynchus sanzenbacheri; Macrosemimimus fegerti). Upper and lower Ettling strata differ in faunal content, with the lower dominated by the small teleost Orthogonikleithrus hoelli (absent from the upper layers, where other prey fishes, Leptolepides sp. and Tharsis sp., occur instead). Pharyngeal and stomach contents of Ettling fishes provide direct evidence that Orthogonikleithrus hoelli was a primary food source during early Ettling times. Scarcity of ammonites and absence of vampyromorph coleoids at Ettling differ markedly from the situation at other nearby localities in the region (e.g., Eichstätt, Painten, Schamhaupten, the Mörnsheim beds), where they are more common. Although the exact biochronological age of Ettling remains uncertain (lack of suitable index fossils), many Ettling fishes occur in other plattenkalk basins of Germany (e.g., Kelheim) and France (Cerin) dated as Late Kimmeridgian to Early Tithonian (eigeltingense horizon), suggesting a comparable geologic age. The Ettling deposits represent an independent basin within the larger Upper Jurassic “Solnhofen Archipelago”, a shallow subtropical sea containing scattered islands, sponge-microbial and coral reefs, sandbars, and deeper basins on a vast carbonate platform along the northern margin of the Tethys Ocean.


Introduction
The Upper Jurassic Plattenkalk region of Bavaria, Germany is famous for its well preserved fossils [1], [2], including numerous vertebrates (notably Archaeopteryx, [3]). The Upper Kimmeridgian to Lower Tithonian limestones of this area formed on the floor of a shallow, subtropical carbonate sea containing scattered islands, sponge-microbial and coral reefs, carbonate sandbars, and deeper basins, on a vast carbonate platform (the "Solnhofen Archipelago") along the northern margin of the Tethys ocean [1], [2]. Paleogeographically, these plattenkalks or lithographic limestones formed in small (under 10 km in diameter) basins (German: "Wannen" [4], [5]) on the carbonate platform, in the midst of a surrounding shallow epicontinental sea [5], [6], [7], [8]. Although traditionally the basins were considered to have been surrounded by large reefs, later hypotheses have suggested that they were often surrounded not by spongealgal or coral reefs but by buildups of carbonate sands, which periodically became partially exposed subaerially to form islands ( [1], [2], [5]). The closest mainlands were the Rhenish Massif to the north and the Bohemian Massif to the west [1], [2]. Recent studies (see [9], [10], [11]) show that depositional conditions differed between the individual basins, indicating that a generalized approach to depositional setting is insufficient and that each basin should instead be studied on an individual basis to determine its paleoenvironment and depositional setting. This work includes documentation of the Ettling fossil fauna and comparison of the fossil faunas in each basin, which can shed light on paleoenvironmental conditions (e.g., salinity and water depth).
The recently discovered Konservat-Lagerstätte of Ettling (Markt Pförring, Bavaria, Germany; Fig. 1), located approximately 50 km E-SE of the village of Solnhofen, is unusual for its excellent preservation and abundance of actinopterygian fishes, which comprise 96% of the total fauna (Tables 1-2). This fish assemblage included several new species (Orthogonikleithrus hoelli Arratia, 1997 [12]; Aspidorhynchus sanzenbacheri Brito and Ebert, 2009 [13]; Macrosemimimus fegerti Schröder et al., 2012 [14]) and even new genera (i.e., Bavarichthys incognitus Arratia and Tischlinger, 2010 [15]). Several taxa (e.g., O. hoelli; A. sanzenbacheri; B. incognitus, M. fegerti) are currently unique to Ettling and unknown elsewhere. The majority of fossil fishes from Ettling are small forms, with the lower part of the quarry dominated by the small teleost Orthogonikleithrus hoelli. Most Ettling species are early teleosts, which first radiated during the Late Jurassic at the time when the Ettling plattenkalks were being deposited. The Ettling locality is therefore of potential importance in understanding the early evolution of modern actinopterygians. The excellent preservation at Ettling also permits answering a variety of important questions regarding paleobiology of fossil actinopterygians, as well as their biogeographical distribution (providing new insight into the breakup of Pangaea) [16][17][18][19][20].
The purpose of the present paper is to provide an overview of the Ettling quarry and a complete list of the Ettling fauna known to date; to present a preliminary investigation of predatorprey relationships and trophic hierarchies during early and late Ettling times based on direct fossil evidence from stomach and pharyngeal contents; and to discuss the potential systematic and paleoecological implications of these new findings.

Geological setting
Overview of the Ettling quarry. The village of Ettling (Markt Pförring) is located on the southernmost rim of the southern Franconian Alb (Fig. 1A) (N 48°49' 3'', E 11°39' 34''). The quarry (Fig. 1B), west of the village, was considered devoid of fossils [21] (except ichnofossils, [22]) until fossil fishes were recently reported by private collectors [25]. A preliminary investigation by JME personnel (2005)(2006) revealed numerous diverse actinopterygians, and in 2007 a Fauna and Predator-Prey Relationships of Ettling contract was made with the local community granting the JME permission to conduct scientific excavations at Ettling.
The Ettling quarry exposure is approximately 33.5 m in vertical height and dissected by numerous vertical tectonic faults (with displacement of up to 30 cm) and joints. The stratigraphic sequence is coarsely subdivided by four slump units (Fig. 2, central column). The lowermost plattenkalk layer (Plattenkalk I: Fig. 2) is approximately 1.5 m thick and located immediately beneath the lowermost slump unit (which is 1 m thick). Immediately above the lowermost slump unit are Plattenkalks II and III (approximately 10 m thick), containing bands of massive limestone beds up to 5 cm in thickness and spaced approximately 20-60 cm apart (e.g., Fig. 2, left column, A-N). These bands can be mapped continuously throughout the quarry and act as useful marker horizons. The second, thin slump unit, which divides Plattenkalks II (below) and III (above), is situated in the middle of this 10 m stack of plattenkalk. The upper boundary of Plattenkalk III is formed by the very conspicuous third slump unit, which is up to 2 m thick (Fig. 2, central column). Following above this upper slump unit are additional plattenkalk layers (Plattenkalk IV) harder than those in the lower part of the quarry. Towards the top of the sequence, the intercalated layers of homogeneous, massive limestone beds increase in thickness and number until the plattenkalk eventually grades into thickly bedded, homogeneous limestone, with individual beds up to 60 cm thick and sometimes separated by millimeter-thin layers of greenish clay. Thin plattenkalk layers (Plattenkalk V) are present within the thickly bedded limestone in the uppermost part of the quarry profile (Fig. 2). Between the massive limestone beds of various thickness, within a space of about half a meter, eight layers of plattenkalk are visible (see detailed profile, Fig. 2, right column), each between a few millimeters and a few centimeters thick. Approximately four meters above the upper layers of Plattenkalk V is a fourth slump unit, before the profile is truncated by the modern soil horizon.
Plattenkalks IV-V (Fig. 2) differ notably in faunal content from Plattenkalks I-III, suggesting a major paleoecological change that took place in what is now a few meters of sediment. The difference is most pronounced in the most common fishes of Plattenkalks I-III vs. Plattenkalks IV-V. Whereas the lower plattenkalks (I to III) are vastly dominated by the small teleost Orthogonikleithrus hoelli, this fish is absent from Plattenkalks IV and V, where the genera Leptolepides, Allothrissops and Tharsis (all absent from Plattenkalks I-III) are most common (Tables 1-2; Fig. 3). To reflect this major difference in faunal content, we subdivide the Ettling sequence into a lower part (Plattenkalks I-III) and an upper part (Plattenkalk IV-V). Although Plattenkalk IV (Fig. 2) remains poorly known due to inaccessibility of the steep quarry face, there is thus far no evidence of O. hoelli in this layer, whereas Leptolepides and Allothrissops already occur near its lower boundary.
Despite the vast numbers of Orthogonikleithrus hoelli within Plattenkalks I-III, these specimens appear randomly distributed, and there are no examples of 'Fischleinflinze' (mass accumulations of individuals, of similar sizes, confined to a particular horizon). This finding suggests that they did not result from sudden events resulting in widespread die-offs. This is unlike the situation in the Eichstätt/Solnhofen region, where numerous examples of 'Fischleinflinze' are present (e.g., JME-SOS8059). At Ettling, multiple specimens of Orthogonikleithrus hoelli are rarely found close to each other on a single bedding plane, and when this does occur the individuals are generally of different sizes, suggesting that they were not members of a single shoal that died simultaneously (unlike the situation in Leptolepides sprattiformis from Eichstätt/Solnhofen described by Viohl [23]).
Preliminary sedimentological research in the lower part of the quarry (Plattenkalks I to III) indicates a calcite-dominated primary sediment, suggesting calcitic whitings within a secluded basin ( [24], [25]). This distinguishes the lower Ettling plattenkalks from those deposited in the Eichstätt/Solnhofen region [26], [24] (defined as the area containing the Eichstätt and Solnhofen basins [27]). In Plattenkalk V, however, intense pitting of the microspar crystals indicates a higher aragonite content in the initial sediment compared to Plattenkalks I-III (Fellner, pers. comm. 2011; [24]). This slight shift in mineralogy suggests a gradual opening of the basin and greater exposure to influx of external sediments. Unlike the basins of Eichstätt and Solnhofen, there is no evidence at Ettling of differential diagenesis [26], [24]. The diagenetic recrystallization common in plattenkalks from Eichstätt and Solnhofen is not observed in the Ettling plattenkalks [26]; [24], contributing to the higher quality preservation of the Ettling fishes. At Ettling, there is also no evidence of concretions beginning to form around the fossils, a process which leads to the so-called "pedestal and socket preservation" ("Sockel-Erhaltung"; [2]: figs. 6.5 and 6.6) typical at Eichstätt. Most Ettling fishes lie completely flat within the bedding plane.
In addition to the finely laminated plattenkalk layers, there are two layers (each up to 1 cm thick) with a chaotic internal structure, marked in the quarry profile as "bioturbated beds" (Fig. 2). These are clearly distinguishable from the layer with Thalassinoides burrows (Fig. 2), which can traverse beds several centimeters in thickness without affecting the surrounding rock. There are also irregularly spaced, greenish clay beds of up to 1 mm in thickness that can be mapped throughout the quarry (the most prominent of these are marked in Fig. 2).
Although most bedding planes are completely flat and nearly smooth, a few contain macroscopic sedimentary structures. Three bedding planes with current indicators (e.g., drag marks and roll marks not caused by ammonites) are present (Fig. 2). Microscopic examination shows that such bedding planes (Fig. 2, left column between H and I) sometimes also contain numerous microscopic echinoderm fragments (ophiuroid sclerites and/or echinoid fragments), small gastropod molds (under 0.5 mm), or microscopic fish remains. A single bedding plane containing completely disarticulated Orthogonikleithrus hoelli (a small teleost) has also been observed. Numerous microbial mats (hundreds if not thousands) are distributed throughout the quarry plattenkalks, and are especially prominent on several bedding planes (see Fig. 2).
Fossils and taphonomic features. The majority of Ettling fossils are nearly complete fishes preserved in lateral view. Much of the phosphatic skeletal material from Ettling is extremely well preserved, and undisturbed by recrystallization, calcite precipitation, or dendrite formation (typical in fossils from other Solnhofen Plattenkalk localities, e.g., Eichstätt). Large calcite crystals, often observed contacting fish fossils and coprolites from Eichstätt and Solnhofen, are absent in Ettling fossils, and silicification (typical at the nearby locality of Schamhaupten) is   Fauna and Predator-Prey Relationships of Ettling also absent. Dendrites are much smaller and rarer than in rocks from the Eichstätt/Solnhofen region. Geological age. The Ettling quarry is part of a larger plattenkalk basin (which has been previously referred to as the "Hartheim Basin", [21]; see also [28], [29]), whose exact morphology and extent of contact with other plattenkalk basins is unknown [30], [31]. The margins of this larger basin may have been formed at least in part by coral reefs, particularly in the north and east ( [7]; Fig. 1). Approximately 1 km north of the quarry the facies grade into reef dolomite; however, presence of a loess cover makes precise mapping of these rocks difficult. A survey of other quarries in the vicinity of Ettling shows that the fish-bearing plattenkalk is restricted to the Ettling quarry. Towards the east these specific beds have been lost due to erosion, and towards the south and west, they are covered by the homogeneous thicker limestone beds that dominate the upper part of the Ettling profile. In other quarries within the Hartheim basin (such as the quarry south of Hagenstetten), these homogeneous thick limestone beds may reach several tens of meters (e.g., 25 m in the infilled quarry of Unterdollig, [21]), interrupted by a number of synsedimentary slump units. The homogenous, thick limestone beds are capped by occasionally bituminous finely bedded marls and marly limestone beds. Such bituminous marls are currently exposed at the quarry of Pettling, where preliminary research shows numerous small teleosts (Leptolepides sp.), and more rarely, invertebrates such as brachiopods and ophiuroids (M. Ebert, pers. obs.).

Fossil assemblage
Coprolites and ichnofossils. Coprolites (Fig. 4) are numerous at Ettling. In Plattenkalks IV-V, only approximately 50% of the coprolites are calcium phosphate, with the other half comprising crushed echinoids and ophiuroids (Fig. 4A). All examined coprolites from Plattenkalks I-III at Ettling (Fig. 4B) contain only fish remains, and over 99% are preserved as calcium phosphate. Their phosphatic composition results in the same dark coloration seen in the vertebrate fossils, making the contents easily observable. A few of these coprolites contain minute teeth of actionopterygian fishes (e.g., pycnodontids: JME-ETT1895; small teleosts: JME-ETT2545). Thalassinoides ichnofossils (formed by crustaceans), and other ichnofossils of unknown origin, are known from Plattenkalk II (Fig. 2). Presence of Thalassinoides indicates a shallow marine setting ( [39]: p. 62).
Non-vertebrate fossils. Non-vertebrates from Ettling include arthropods (insects, horseshoe crabs, and crustaceans), brachiopods, mollusks, echinoderms, jellyfish, sponges, biomats, and plant fragments (Tables 1-2; Fig. 5). Unlike fishes, most are poorly preserved. Mollusks are rare. Cephalopods comprise only 29 ammonites (impressions in matrix referred to Oppeliidae and Perisphinctoidea, from both the upper and lower Plattenkalk series), and one belemnite with an intact phragmocone (Hibolites, from Plattenkalk II). Ammonite aptychi are unknown at Ettling, unlike Eichstätt where they are often found in situ. Bivalves and gastropods are infrequent and poorly preserved, and are known from both Plattenkalks I-III and IV-V. Small gastropods (under 1 cm) occur as molds, and larger specimens (1-2 cm) as impressions in matrix.
Arthropods from Ettling comprise insects (Coleoptera: small beetles, and Odonata: dragonflies resembling the genus Stenophlebia from Plattenkalks I-III), xiphosurans (horseshoe crabs), and crustaceans. The latter are represented at Ettling by at least three decapod genera (Pseudastacus sp., Mecochirus sp., and a specimen resembling Aeger from Plattenkalks I-III; and a Decapoda indet. from Plattenkalks IV-V; G. Schweigert, pers. comm.), poorly preserved ostracods (from Plattenkalks I-III), and one indeterminate isopod (also from Plattenkalks Fauna and Predator-Prey Relationships of Ettling I-III). Three specimens of the xiphosuran genus Mesolimulus have been found, thus far limited to Plattenkalks IV-V. They are juvenile specimens ranging from one to five cm body length.
Echinoderms are very rare in the lower plattenkalks (I-III) at Ettling, and thus far include only one identified echinoid (Phymosoma sp.) and a small Ophiuroidea indet. In Plattenkalks IV-V complete echinoids and ophiuroids are also rare, but here they are often found as fragments within coprolites (see above). The high-magnesium calcite of echinoderms is well Fauna and Predator-Prey Relationships of Ettling preserved. Presence of echinoderms indicates normal marine salinity ( [40]: p. 223). Other nonvertebrates from Ettling include brachiopods (several terebratulids from Plattenkalks I-III and IV-IV; one rhynchonellid belonging to Lacunosella sp. from Plattenkalk II), sponges (Plattenkalk I), and jellyfish (Plattenkalk V). Microbial biomats are also present ( Fig. 2; and see above). Because previous research has shown that such microbial mats can play an essential role in taphonomy and preservation of fossils (as fossils trapped by them are often preserved in pristine condition) [41], the role of biomats at Ettling remains an important topic for future research. Plant fossils thus far comprise two clear leaf imprints of the pteridosperm (seed fern) genus Cycadopteris (one from Plattenkalk I and the other from Plattenkalk V), and five poorly preserved imprints of conifer twigs (genus Brachyphyllum, from Plattenkalks I-III and IV-V).
Vertebrates. Poorly preserved fragments of an adult turtle were found in Plattenkalk II. A well-preserved juvenile (JME-ETT115, Fig. 6; approximately five centimeters long, with an unossified carapace) was found in Plattenkalk I and tentatively referred to Eurysternum sp. [42] (which can attain an adult shell length of over 30 cm).
Halecomorphs. Four halecomorph species are currently known from Plattenkalks I-III: one amiid (Amiopsis lepidota, Fig. 9), two ophiopsids (Ophiopsis sp. [46]; Furo muensteri, [45]), and Ionoscopus sp. (the latter known only from fragments). The exceptional preservation of the new Amiopsis material reveals the presence of fringing fulcra on the dorsal lobe of the caudal fin ( [17]: fig. 17), a feature previously unknown in Amiopsis and described as absent in amiids (e.g., [52]: p. 847; [53]: p. 583). With sharp, elongate teeth and streamlined fusiform bodies adapted for rapid swimming, halecomorphs such as Furo muensteri and Amiopsis lepidota were likely among the major predators at Ettling. There is evidence that caturids may also have been present in early Ettling times (represented by a single tooth approximately 1.5 cm in height, JME-ETT231; and a fragmentary specimen in a private collection; both from Plattenkalks I-III), although additional material is needed to confirm this.
Teleostei. Early teleosts first appeared in the Late Triassic [12], [56], [57], [60]. They radiated in the Jurassic to produce numerous new taxa, and now comprise approximately 96% of extant fish species [67]. The Ettling fauna adds to knowledge of this important period in teleost evolution by contributing several new taxa.
Teleostei (sensu Arratia, 2013 [60]) from Plattenkalks I-III comprise Orthogonokleithrus hoelli Arratia, 1997 (Euteleostei, Orthogonikleithridae; Fig. 12); at least two new species of    Fig. 14). Orthogonikleithrus hoelli is represented by numerous adult and juvenile specimens [20]. Specimens of Thrissops cf. formosus show variations in morphology and color pattern, and include an ontogenetic series ranging in length from 4.3 cm (in a largely unossified juvenile; Fig. 12) to a maximum of 55 cm. Arratia and Tischlinger [15] described the new species Bavarichthys incognitus from Ettling, representing the earliest crossognathiform fish known from Europe. Crossognathiforms (an extinct order of basal teleosts) are otherwise known in Europe only from the Cretaceous. Older Jurassic crossognathiforms are known from Chile and Cuba. A faunal exchange between areas so widely  Fauna and Predator-Prey Relationships of Ettling separated during the Jurassic (the Caribbean/South America and the northern margin of the Tethys) would have been possible via the young Mid-Atlantic [15], [19].

Fossil Actinopterygians from Plattenkalks IV-V
Ginglymodins. Two macrosemiids (one new species of Macrosemius, and Notagogus cf. denticulatus) occur in Plattenkalk V. Each taxon is known only from a single specimen (Table 2).
Halecomorphs. Two halecomorphs are present: a single specimen of Ophiopsis procera (a different species form from that found in the lower part of the quarry; [46]) from Plattenkalk V, and a single specimen of Furo muensteri from Plattenkalk IV ( [30], [45]).
Pycnodontiforms. Two pycnodontiforms, Proscinetes bernardi (Fig. 10C) and Turbomesodon cf. relegans, are known from Plattenkalk V (each from a single specimen; Table 2). The specimen of Proscinetes is extremely well preserved, and represents the largest individual of this genus yet known from the Late Jurassic of southern Germany. The specimen of Turbomesodon (JME-ETT145), albeit fragmentary, is the largest representative of its genus yet known (at approximately 25 cm in length). Fauna and Predator-Prey Relationships of Ettling "Pholidophoriforms". A third new "pholidophoriform" species (which differs from the two species occurring in Plattenkalks I-III) appears in Plattenkalk V (currently under study by G. Arratia).

Fossil evidence of predation in Ettling fishes
A total of 59 actinopterygian fish specimens from Plattenkalks I-III from the JME excavations at Ettling contain fossil prey items. Of these, 20 specimens contain prey lodged in the pharynx, and 39 specimens contain prey in the stomach (Tables 3-4). In all specimens the prey items consisted entirely of fishes, with Orthogonikleithrus hoelli confirmed as prey in 53 cases and considered probable prey (based on vertebral morphology) in five of the remaining six cases. Only one specimen, JME-ETT11 (Table 4), contains a prey fish other than O. hoelli.
Twenty out of a total 3,000 specimens of Orthogonikleithrus hoelli contain smaller conspecific individuals as stomach or pharyngeal contents, indicating occasional cannibalism (Fig. 13). Even juveniles (e.g., JME-ETT2642, a specimen of 2.2 cm total length) are found containing smaller fish as prey. In contrast to Orthogonikleithrus, specimens of Leptolepides sprattiformis, the most common small teleost in the Eichstätt/Solnhofen area, have not been found containing prey items. Fossil evidence from Ettling shows that predators of O. hoelli included an additional new species of Orthogonikleithrus (G. Arratia, pers. comm.) that is larger than O. hoelli (reaching up to 13 cm in length; Fig. 13A). Another small teleost (Teleostei n. sp. 1, Arratia, in progress), which has large teeth, often (in about 15% of all known specimens) contains partially digested or half-swallowed specimens of Orthogonikleithrus hoelli (Fig. 14B). In the majority of specimens with pharyngeal contents prey is orientated headfirst (the preferred orientation for gape-limited fish predators; [67]: p. 328; [68]). Specimens with prey lodged in the pharynx are common in the fossil record, and represent occasional errors in judgment by the predators (i.e., selection of too-large prey), resulting in death by choking [23]; [67][68][69][70].
Approximately 50% of adult specimens of Orthogonikleithrus n. sp. 1 from Ettling, and 67% of adult specimens of Teleostei n. sp. 1, contain prey in the pharynx or stomach. Stomach contents of a single individual sometimes contain more than one Orthogonikleithrus hoelli of different sizes and ages (see Fig. 14B; Table 4). The holotype and only specimen of Bavarichthys  [43], which at 55 cm in length is among the largest predatory fishes from this locality, have also been found with Orthogonikleithrus hoelli as stomach contents. This predatory species has very small teeth, consistent with a diet of small prey fishes. A small juvenile specimen of Thrissops cf. formosus with stomach contents (JME-ETT 166; total length 13 cm) also contains O. hoelli. Although stomach contents are rarely visible in Fauna and Predator-Prey Relationships of Ettling fishes with ganoid scales (due to their thickness and opacity), a juvenile Belonostomus cf. kochi from Ettling is preserved with an Orthogonikleithrus hoelli lodged in the pharynx ( Fig. 11; [16]: Fig. 8) and two other specimens were found with O. hoelli in the stomach (see Table 4). These are among the first documented examples of piscivory in Belonostomus from Bavaria ( [23]: tab. 1).

Paleoecological comparison of Ettling with other plattenkalk basins
Ettling differs notably in its faunal composition from other well-known plattenkalk localities of the region (e.g., Eichstätt, Wattendorf, Schamhaupten). At Ettling the fauna is predominantly (96%) actinopterygian fishes (Fig. 7), and fossil stomach contents as well as coprolites from Plattenkalks I-III comprise only fish remains (Tables 3-4; Fig. 4B; [16]). In contrast, at Eichstätt invertebrates (e.g., the nektonic to planktonic crinoid Saccocoma and small ammonites) are the predominant fossils, so common that some beds are virtually covered with specimens. Saccocoma ([2]: p. 74) and aptychi are also common in coprolites from Eichstätt. The Eichstätt basin is additionally characterized by vampyromorph coleoids (e.g., Plesioteuthis, Trachyteuthis, Leptoteuthis, Muensterella, Palaeologio) [71]) and a diverse arthropod fauna (as well as fish taxa), whereas at Ettling arthropods and ammonites are much rarer, and Saccocoma and vampyromorph coleoids are absent. The Ettling fauna also differs from that of Schamhaupten and Wattendorf, which (unlike Eichstätt) have been the sites of recent scientific studies ( [72], [73]; Fig. 7). Unlike Ettling, the fauna at Schamhaupten is 69.6% mollusks (e.g., ammonites), with fishes as a minority (representing 14.2% of known specimens) [72].Vampyromorph coleoids are also present at Schamhaupten (where some specimens contain fish remains as stomach contents [72]). At Wattendorf, invertebrates also outnumber fishes, with brachiopods representing 50% of total specimens (whereas fishes represent 5% of total specimens) [73]. Although a comprehensive statistical comparison of the Ettling fauna with that of other German plattenkalk basins is beyond the scope of this paper, compilation of a database for future statistical analysis has already begun (Ebert and Kölbl-Ebert, in progress).
In addition to its overall faunal composition, the fish fauna at Ettling also differs from that of other plattenkalk localities of the region. For example, in the Eichstätt basin the teleosts Leptolepides Nybelin, 1974 [78], Tharsis Giebel, 1848 [79], and Allothrissops Nybelin, 1964 [80] are the most common fishes. At Ettling, these genera occur in the upper part of the quarry (Leptolepides and Allothrissops are relatively common in Plattenkalk V, and also occur in Plattenkalk IV), but not in Plattenkalks I-III. Additionally, the species of Tharsis and Leptolepides from Ettling are distinct from those found at Eichstätt (Arratia, in progress). The teleost species Orthogonikleithrus hoelli is thus far unique to Ettling, and only found in Plattenkalks I-III. This species (so abundant in the lower part of the quarry) is not found above the slump unit underlying Plattenkalk IV.
Predator-prey relationships at Ettling, and the role of Orthogonikleithrus hoelli. Konservat-Lagerstätten such as Ettling, with their excellent preservation and abundance of fossils, provide a rare glimpse into predator-prey relationships and trophic structure of ancient aquatic communities. Although a complete paleoecological investigation is beyond the scope of the present paper, Maisey [81] showed that much information regarding trophic structure in aquatic paleocommunities can be gleaned from investigating the stomach and pharyngeal contents of fossil fishes. He also outlined the reasons why specimens containing prey items in the pharynx and/or stomach are generally rare in the fossil record [81].
Maisey [81] used the criteria of Boucot [82] to classify the different types of evidence that can be applied to paleoecological studies of fossil fishes. Of these, 'Category 1' evidence (the most reliable) comprises 'frozen behavior' (e.g., one fish eating another). 'Category 2' evidence (slightly less reliable) comprises 'Category 2A' (close association but not in position, e.g., presence of both a predator and its presumed prey in the same strata) and 'Category 2B' (functional interpretation of morphology, e.g. large robust teeth of a presumed predator). Categories 3, 4, and 5, considered by Boucot [82] to be progressively more speculative, include trace fossils of unknown origin (e.g., trackways). Maisey [81] placed 'isolated bone balls' of presumably digested or regurgitated prey (not directly associated with remains of a specific predator) in this category.
Because scientific fieldwork at Ettling was begun only recently (in 2007), it will be some time before a complete picture of its paleoecology can be reconstructed (requiring the discovery of additional fossil specimens and detailed investigation of macroinvertebrates, palynology, data from microfossils, etc.). However, there is already an abundance of reliable 'Category 1' [81], [82] evidence of predator-prey relationships (numerous specimens with stomach and pharyngeal contents), from which we can begin to reconstruct fish trophic structure in the Ettling paleocommunity (see Tables 3-5). 'Category 2' evidence is also present (for example, Category 2A: presence of Thrissops and Leptolepides together in Plattenkalk V, two genera previously known from direct evidence to have been predator and prey, respectively, at other plattenkalk localities: [81]; Category 2B: presence of large, robust, sharp teeth in Furo muensteri suggesting that it was a major predator: [45]).
The large number of fossil actinopterygians in the lower part of the quarry (Plattenkalks I-III) containing the small teleost Orthogonikleithrus hoelli as prey (Tables 3-4) provides direct 'Category 1' evidence proving that this fish was a major food source during the early period of deposition at Ettling. Furthermore, the extreme abundance of this species at Ettling (representing 91% of fish specimens from Plattenkalks I-III) strongly suggests that its population was large at the time of deposition of the lower Ettling strata, outnumbering other fish taxa by far. These two factors, combined with its size (the smallest known fish species in the Solnhofen Archipelago, at 5.5 cm maximum length [12]), are consistent with placing O. hoelli near the bottom of the documented trophic hierarchy of fishes during early Ettling times. The discovery of several specimens of O. hoelli containing conspecific individuals suggests that this species had at least a partly piscivorous diet (occasionally engaging in cannibalism), whereas its predation on organisms at lower trophic levels remains undocumented.
Other small fishes that preyed on Orthogonikleithrus hoelli during early Ettling times included at least one of two other species of Orthogonikleithrus (Orthogonikleithrus n. sp. 1), and a small undescribed teleost (Teleostei n. gen. n. sp. 1). Mid-size and larger predators known from 'Category 1' evidence to have preyed on Orthogonikleithrus hoelli during the early period of Ettling deposition included Thrissops cf. formosus, Belonostomus cf. kochi and Bavarichthys incognitus. Interestingly, among the species known from direct evidence to have preyed on O. hoelli are those with the highest relative abundances at Ettling. Excluding the 3,000 known specimens of Orthogonikleithrus hoelli itself, these are: Teleostei n. gen. n. sp. 1 (comprising 29% of remaining fish specimens); Orthogonikleithrus n. sp. 1 (19%); Thrissops cf. formosus (14%); and Belonostomus cf. kochi (6%) (see Table 1). However, it is also possible that this is an artifact of preservation (because chances of finding examples of 'frozen behavior' increase as more specimens are found).
In addition to direct 'Category 1' fossil evidence, 'Category 2A' evidence [82] (presence of both predator and presumed prey, based on evidence from other localities) is also available for Ettling. In the Eichstätt/Solnhofen region, Leptolepides sprattiformis is the most common small fish species, and was placed near the bottom of the Solnhofen trophic hierarchy of fishes (with Tharsis) by Maisey [81]. Whereas at Eichstätt and Solnhofen Thrissops preyed on Leptolepides, in Plattenkalks I-III at Ettling Thrissops preyed on Orthogonikleithrus hoelli. It is unknown what Leptolepides preyed on at Ettling (as its stomach and pharyngeal contents remain unknown), although this taxon has been considered by previous authors as a plankton feeder that swam in large shoals. The lack of fine, long gill rakers and other filter-feeding adaptations suggests that fishes such as Leptolepides, Orthogonikleithrus hoelli, and Tharsis were not filterfeeders, but rather micro-carnivores/visual zooplanktivores and opportunistic piscivores (e.g., Orthogonikleithrus hoelli) that selected individual prey items in the water column and engulfed them using oral suction (M. Wilson, pers. comm.).
Of the genera illustrated by Maisey [81] in his Solnhofen trophic web, two (Thrissops and Aspidorhynchus) are present in the lower part of Ettling, and four (Thrissops, Allothrissops, Leptolepides, and Tharsis) are present in the upper part. Thrissops likely occupied an intermediate trophic level at Ettling, as in other Solnhofen localities (e.g., [81], [83]). According to Maisey [81], Thrissops and Allothrissops preyed on Leptolepides at Solnhofen localities, and this may also have been the case in the upper period at Ettling, although this is not yet proven by direct ('Category 1') evidence.
Although evidence of caturids from Ettling is currently limited to an isolated tooth and a fragmentary specimen, these large, sharp-toothed fishes were top predators in other localities within the Bavarian Upper Jurassic [81], [83] including Eichstätt, Solnhofen, and Painten, where they consumed the intermediate-sized fishes Anaethalion, Pholidophorus, Ascalabos, Eichstaettia, and the small teleost Leptolepides [81], [83]. However, due to the poverty of fossil evidence, it is unknown if caturids played as significant a role in the Ettling food web as they did at other localities in the region.
'Category 2B' evidence [82] (i.e., evidence inferred from tooth morphology) is also present at Ettling. Pycnodontiforms were present in both early and late Ettling times, and possessed a battery of crushing teeth appropriate for feeding on hard-shelled prey (e.g., mollusks). There is evidence that pycnodontiforms preyed on ammonites at some localities [84]. There is also direct evidence that pycnodontiforms preyed on corals, echinoids, bivalves, gastropods, decapods, and small actinopterygians ( [47], [54], [85], and M. Ebert, pers. obs), although some taxa were apparently highly specialized to certain prey items. This could be inferred to provide 'Category 2A' evidence for similar habits among pycnodontiforms at Ettling. Echinoids, brachiopods, bivalves, gastropods, decapods, and small fishes were certainly present at Ettling, although which of these formed the primary diet of the Ettling pycnodontiforms has not yet been indicated by 'Category 1' evidence. Corals were presumably present in the nearby reefs, but no coral remains were found in any coprolites. However, crushed echinoid and ophiuroid remains are abundant in coprolites from Ettling Plattenkalk V. That pycnodontids were preyed on at Ettling is indicated by the discovery of at least one small coprolite (JME-ETT1895) containing the toothed prearticular of a pycnodont resembling Turbomesodon relegans.
Based on the above categories of available evidence, as well as comparison with closest living relatives (e.g., Amiopsis/living Amia) and the few faunal studies from other plattenkalk basins (e.g., [81], [82], [83]), Table 5 summarizes the probable trophic levels and feeding strategies of the Ettling actinopterygians. 'High-level predators' are here interpreted as comparatively large fishes with large, sharp, robust teeth, large gape size, and containing fossil prey fishes. Large piscivorous predators from Ettling capable of attacking larger prey include Aspidorhynchus sanzenbacheri and the halecomorphs Amiopsis lepidota, Ionoscopus sp., Furo muensteri (although at Ettling these taxa have not yet been found with stomach or pharyngeal contents), and possibly caturids. 'Mid-level predators' are intermediate in these respects, with intermediate body size, sharp but comparatively smaller teeth, and containing fossil prey fishes. 'Low-level predators' have a small body size, small sharp teeth, and contain fossil prey fishes of small size. 'Durophages' have a grinding or crushing dentition, with rounded peg-like teeth anteriorly and broader, blunt, button-shaped teeth posteriorly. Where available, stomach contents include echinoderms and other invertebrate fragments. Fishes listed as 'Other' in Table 5 lack teeth, and fossil stomach contents are generally absent (although occasional cannibalism has been documented in Orthogonikleithrus hoelli [16]). These fishes (including O.hoelli, Leptolepides, Table 5. Probable trophic levels of actinopterygian fishes at Ettling. Other*: probable suction-feeding micro-carnivores/visual zooplanktivores and opportunistic piscivores.
Pachythrissops sp. and Tharsis) likely represent micro-carnivores/visual zooplanktivores and opportunistic piscivores, which captured individual small prey items using oral suction (M. Wilson, pers. comm.). A diet of mainly zooplankton and small soft-bodied invertebrates would explain the usual lack of visible fossil stomach contents in these taxa. Changes in the Ettling fauna through time. Geological and paleontological evidence from Ettling suggests that significant paleoecological changes occurred in the basin between the time of deposition of Plattenkalks I-III and that of Plattenkalks IV-V. Based on direct fossil evidence of predation, it can be inferred that Orthogonikleithrus hoelli was a major component of the fish trophic web in early Ettling times. In the lower part of the Ettling basin, Orthogonikleithrus hoelli appears to have populated the surface waters in great numbers, and was the main food source for a diverse array of large and small predatory fishes. The reason for the unusually high abundance of O. hoelli in the lower part of the Ettling quarry is unknown and remains an interesting topic for future research. By the time of deposition of Plattenkalks IV-V, O. hoelli had disappeared locally, and a new faunal assemblage more closely resembling that of the Eichstatt and Solnhofen basins had developed. This faunal change was accompanied by geological evidence indicating a change in depositional environment (i.e., from a calcite-based to a calcite-plus-aragonite-based primary sediment), suggesting an influx of outside sediment consistent with gradual opening of a previously isolated basin (Fellner, pers. comm., 2011; [24]).
Based on the evidence to date, Plattenkalk V also appears to contain a higher relative abundance of reef-dwelling fishes (e.g., pycnodontids, Macrosemius, Macrosemimimus) than do Plattenkalks I-III (Fig. 3, lower chart). In Plattenkalks I-III, approximately 1% of specimens (25% of species) are reef-dwellers, whereas at Plattenkalk V reef-dwellers comprise approximately 8.7% of specimens (30% of species). Numerous accumulations of disarticulated and broken echinoids and ophiuroids in the same beds (interpreted as coprolites or food remains; Fig. 4A) also suggest predation by durophagous reef-dwelling fishes (e.g., the pycnodontiforms Turbomesodon and Proscinetes; Table 5). Although these two genera also occur in Plattenkalks I-III, similar coprolites or food remains attributable to them are unknown there. The Ettling basin was surrounded by several coral reefs of unknown relative age, such as Großmehring (Late Kimmeridgian: G. Schweigert, pers. comm.), Oberdolling, Lobsing, Marching and Wackerstein [22], [32], which could be related to the occurrence of reef fishes. The occurrence of horseshoe crabs (e.g., Mesolimulus), and a more frequent occurrence of plant remains as well as brachiopods and bivalves, in Plattenkalk V (compared to the deeper quarry levels) is another marked difference between the upper and lower parts of the quarry, which could indicate increased proximity to land. The fossil record at Ettling, with its uniquely high proportion of actinopterygian fishes and well-preserved evidence of ancient predatory behavior, distinguishes this locality from other plattenkalk basins of the Upper Jurassic Solnhofen Archipelago and provides a rare glimpse into an ancient aquatic ecosystem of the Late Jurassic.

Materials and Methods
All necessary permits were obtained for the described field studies by the Jura-Museum Eichstätt from the Marktgemeinde Pförring (village council of Markt Pförring, Bavaria) and its mayor Bernhard Sammiller, owners of the Ettling quarry. Specimens described herein were collected at Ettling and are reposited in the JME collections. Nearly all specimens were hand-prepared by one of us (ME). Air-pressure vibration tools and acid preparation techniques were not used, as these are unsuitable for the soft and porous Ettling stone. Moreover, acid preparation can create an artificial bias in data on fossil stomach contents, as it destroys carbonatebased material (e.g., invertebrate shells) but preserves phosphate-based items such as bone [81].