Above the ‘Wasserfallschichten’ [Waterfall Beds] (c. 8.8 m; Rieber 1963, text-fig. 2) follows the ‘sandige Tonmergel’ [Sandy Clay-Marls] (8.6 m) with the ‘Zopfplatten’ [Gyrochorte Beds] (4–4.5 m); the latter are positioned in the upper half of the ‘sandige Tonmergel’ (Fig. 2).

Untere Wilflingen-Bank [Lower Wilflingen Bed] (= uWB; c. 1.6 m; = Comptum-Bank sensu Rieber 1963)

The Untere Wilflingen-Bank (formerly: Comptum-Bank, see Dietze et al. 2021a) consists of a chamosite-oolitic, gray-green to dark brown marly limestone, partly rich in fossils. In our excavation sites at the southern hillside of the Wochenberg, most ammonites occurred in the well-lithified beds uWB-4 and uWB-7. The thicknesses and lithologies of individual beds are almost identical in both sections. In other outcrops at the headwaters of the Schörzinger Starzel River, the Untere Wilflingen-Bank has an overall similar thickness, but at each section it shows some variation in respect of the thickness and lithology of individual beds. Like in our two excavation sites at the Wochenberg hill, the ammonites occur in two layers located in more or less the same position within the Untere Wilf­lingen-Bank. The frequency of ammonites in both fossiliferous horizons varies at the various localities.

• Bed uWB-1 (0.15 m): arenaceous clayey marls with weathered lithified limestone portions, yellow to beige.
• Bed uWB-2 (0.15 m): arenaceous marly limestone, occasionally with lithified portions of strongly weathered marly limestone, rusty.
• Bed uWB-3 (0.15 m): clayey marl, gray in its upper part; with a yellow-beige layer in its middle.
• Bed uWB-4 (0.4–0.5 m): lithified calcareous marl, partly chamosite-oolitic, partly arenaceous, with abundant ammonites and bivalves.

Bivalves: Isocardia cordata Buckman, Gresslya sp., Clavitrigonia brodiei (Lycett), Cl. sp. (small-sized), Pholadomya fidicula Sowerby, Entolium demissum (Phillips), Astarte elegans Sowerby, Inoperna sowerbyana (d’Orbigny), Parvamussium pumilus (Lamarck). Ammonites are concentrated slightly above the middle of the bed. Occasionally with a poorly lithified marly limestone layer (0.05 m) located slightly below the middle of the bed. In the latter case, the ammonites occur in the lower part of the bed.

Ammonites: Leioceras crassicostatum [M], L. goetzendorfense [M], L. paucicostatum [m], L. striatum [m]

• Bed uWB-5 (0.1–0.2 m): lithified calcareous marl, more marly developed at its base.
• Bed uWB-6 (0.08–0.1 m): unconsolidated, rusty calcareous marl.
• Bed uWB-7 (0.4–0.5 m): chamosite-oolitic or arenaceous, very hard bluish-gray calcareous marl, which splits into three separate beds when weathered. The bluish-gray calcareous marls exhibit a brown-beige weathering rim. Fossils are extremely rare. Above the basal layer (c. 0.1 m) follows a thin rusty layer. Usually, the only ammonites occur c. 0.15–0.2 m below the top of the bed within a 0.01 to 0.1 m thick layer of shell debris separating the two upper partial beds.

Ammonites: L. goetzendorfense [M], L. paucicostatum [m], L. striatum [m]

• Bed uWB-8 (0.1 m): lithified calcareous marl.
• Bed uWB-9 (0.3 m) arenaceous clayey marl.

Ammonites: L. goetzendorfense [M]

• Bed uWB-10 (0.1 m): nodular calcareous marl.

Tonmergel [Clay-Marl] (c. 3.2–4 m): this unit was not exposed and could not be studied. At the southern hillside of the Wochenberg we measured a vertical distance of c. 12–13 m between the top of the Untere Wilflin­gen-Bank (= Comptum-Bank sensu Rieber 1963) and the top of the Staufensis-Bank. This is in contrast to Rieber (1963, text-fig. 2, Profil c), who reported a much greater thickness of c. 24 m for this interval. After our new measurements, the vertical distance between the basis of the Obere Wilflingen-Bank [Upper Wilflingen Bed] and the top of the Untere Wilflingen-Bank [Lower Wilflingen Bed] is only 3.2–4 m (variable in different sites along the southern escarpment) and not 17.5 m as mentioned by Rieber (1963, text-fig. 2, Profil c Wochenberg). Rieber (1963) interpolated the distance between the „Comptum“-Bank up to the Staufensis-Bank across the Wochenberg hill from the northern to the southern hillside in several steps; this procedure may have resulted in significant measurement errors.

Obere Wilflingen-Bank [Upper Wilflingen Bed] (1.6–1.7 m; Fig. 3)

In one of his sections, Rieber (1963, text-fig. 2, Profil c) showed a separate bed with a maximum thickness of 1 m that follows at a vertical distance of 14 m above the Untere Wilflingen-Bank. It seems that this obviously discontinuously developed bed may reach even greater thicknesses at some places of the Wochenberg hill. In the Katzensteige section near Gosheim, Rieber (1963 text-fig. 2, Profil b) termed a c. 1.45 m thick bed following 3.3 m above the „classical“ ammonite-bearing “Comptum”-Bank [“Comptum”-Bed] (= Untere Wilflin­gen-Bank) as well as “Comptum”-Bank. This is why we refer to the higher bed as ‘Obere Wilflingen-Bankʼ.

• Bed oWB-1 (0.3 m): the 0.2 m thick lower part of this bed (oWB-1a) consists of brown arenaceous calcareous marl with bluish-gray hard limestone lenses. The upper 0.1 m thick portion of the bed (oWB-1b) consists of a brown to brick-red marly limestone with abundant compressed ammonites.

Ammonites (bed oWB-1b): Ancolioceras sp. [M], Leioceras sp. [M]

• Bed oWB-2 (0.25 m): same lithology as bed oWB-1a; from a calcareous lense within this bed, a single specimen of Ancolioceras subfalcatum was recovered.

Ammonite: Ancolioceras subfalcatum [M]

• Bed oWB-3 (0.3 m): marly limestone, gray, brown in weathered state, with layers of compressed ammonites.

Ammonites: Ancolioceras sp. [M], Leioceras sp. [M]

• Bed oWB-4 (0.05 m): clayey marl, gray.
• Bed oWB-5 (0.05–0.1 m): lithified marly limestone, brown.

Ammonites: Leioceras sp. [?M]

• Bed oWB-6 (0.2–0.25 m): marly limestone, weakly lithified, brown, with small limestone nodules (diameters 0.01–0.02 m). In its upper part layers with mostly compressed ammonites.

Ammonites: Leioceras evertens [M], L. goetzendorfense [M], Ancolioceras subfalcatum [?m]

• Bed oWB-7 (0.1–0.13 m): marly limestone, weakly lithified, with lenses of gray, hard limestone with a brownish weathering rim. Most of the limestone lenses did not contain fossils; a few of them contained shell fragments, and only a single one yielded a couple of ammonites.

Ammonites: Ancolioceras noszkyi [M], A. viallii [M]

• Bed oWB-8 (0.1–0.15 m): clayey marl, gray in unweathered state; compressed ammonites occur frequently in layers.

Ammonites: Leioceras goetzendorfense [M], Ancolioceras sp. [M]

• Bed oWb-9 (0.1–0.2 m): the lithology of this bed changes significantly within distances of a few metres. At the left side of our excavation at the southern hillside of the Wochenberg it is developed as a brown calcareous marl (0.1–0.13 m), partly rusty, containing hard, splintery gray limestone nodules almost lacking fossils, only occasionally with shell debris (up to 0.3 m in diameter), with a rusty-brown weathering rim. In the opposite side of our excavation, this bed is thicker (0.2 m) and there, the upper c. 0.05 m of the bed, which is developed as a densely packed bivalve shell bed, are commonly split off. The lower part of the bed (c. 0.15 m) is a gray-bluish limestone. Most ammonites occur in the marginal part of the nodules or of the limestone bed and reach at least partly the rusty oxidation zone; only few ammonites occurred in the centre of the limestone nodules or in the centre of the bed. Apart from a few marly layers with a relatively rich ammonite content, the majority of ammonites from the Obere Wilflingen-Bank originates from bed 9. In all other parts of the Obere Wilflingen-Bank ammonites are extremely rare. Only bed oWB-9 could be intensively sampled.

Ammonites: Ancolioceras aff. subacutum [M], A. citaae [M], A. viallii [M], A. cf. viallii [M], A. krymholzi [M], A. subfalcatum [M], A. aff. substriatum [m], Leioceras goetzendorfense [M], L. capillare [M], L. striatum [m].

Marly limestone (1.9 m): brown, c. 0.2–0.3 m above its basis with a layer of small gray limestone nodules (c. 0.05–0.1 m in diameter) surrounded by layered rusty weathering rims; numerous burrows.

Ammonites: Ancolioceras sp.

Limestone / marly limestone (c. 0.8 m; = ? Sinon-Bank sensu Rieber 1963, text-fig. 2, Profil c): At the very steep southern hillside of the Wochenberg which is thickly covered with soil and talus, this interval could only be localized at two small places. We did not find any ammonites there, but an intensive sampling of this bed was hampered by the steep slope. It is possible that a small sample of well-preserved ammonites from the Wochenberg hill in the G. and U. Bayer collection (SMNS) originates from this interval; however, the exact position of these ammonites (which are preserved in a shelly matrix) within the section, is unknown.

• (0.05–0.1 m): hard, splintery, laterally thinning lenses of gray limestone with pyrite, no macrofossils recorded.
• (0.0–0.2 m): weakly lithified marly limestone, brown.
• (0.6 m): alternation of limestone, calcareous marl and marly limestone.

• 0.1–0.2 m: limestone, mainly consisting of fine bivalve shell debris.
• 0.02–0.04 m: weakly lithified marly limestone, brown, partly pinching out.
• 0.1–0.12 m: splintery limestone, gray, no macrofossils recorded.
• 0.25–0.3 m: several gray, irregularly thinning platy limestone benches with small lithoclasts, separated by lithified brown marly limestone. Between the limestone benches Zoophycos burrows occur. A massive bed in fresh state.

Clayey marl (c. 1.1–1.3 m): clayey to marly limestone, brown (not studied in detail).

Arenaceous limestone (0.9 m) [= Sehndensis-Knollenlage sensu Rieber 1963, text-fig. 2, Profil c): at our excavation site, this interval was developed as uniform bed. In fresh state, the bluish to brown bed is splintery hard and apparently lacking macrofossils. In weathered state, it splits into several smaller beds. No ammonites were found.

Ammonites: Staufenia “sehndensis” [after Rieber 1963; SMNS, ex coll. G. and U. Bayer]

Clayey marl (0.8–0.9 m): arenaceous, thin-bedded, brown-yellow, with rare reworked limestone pebbles, ichnofossils (Zoophycos) and occasional bivalves (Pholadomya sp.). The lowermost 0.1 m are lithified and amalgamated with the underlying calcareous marl.

Staufensis-Bank (sensu Rieber 1963; 1.2–1.6 m): The thicknesses of individual beds within the Staufensis-Bank varies significantly over short distances. However, this variation does not hamper the recognition and correlation of these beds. Contrary to Rieber (1963), our new observations revealed that the uppermost layers are completely eroded at the Wochenberg hill. Since the lithostratigraphic term ‘Staufensis-Bankʼ is defined in the wider area as the uppermost thicker set of limestones following below the Concava-Bank, we used the term Staufensis-Bank despite of this erosional lack of its uppermost part which otherwise yields the name giving index fossil Staufenia staufensis. The shell beds mainly contain small-sized ammonites, occasionally also larger-sized ones. Most specimens occur on the surfaces of several smaller beds into which the Staufensis-Bank can be split.

• Bed St-B 1 (0.1–0.2 m): soft, marly limestone, brown-yellowish, rusty, lacking macrofossils.
• Bed St-B 2 (0.05–0.1 m): soft, either an arenaceous marly limestone, or developed as a hard limestone with a bluish core; the only recorded macrofossil is the ichnofossil Zoophycos. Together, beds St-1 and St-2 have a constant thickness of 0.2 m.
• Bed St-B 3 (0.05–0.1 m): marly limestone with poorly preserved, compressed Staufenia sp. Complete phragmocones are often locally accumulated, but nearly absent at other places.

Ammonites: Staufenia latiumbilicus [M]

• Bed St-B 4 (0.1–0.15 m): flaser-bedded calcareous marl, arenaceous, in the centre more calcareous and of bluish colour, marginally brown; poorly fossiliferous, rare accumulations of nuclei of Staufenia, bivalves and shell debris.

Ammonites: St. latiumbilicus [M]

• Bed St-B 5 (0.25–0.35 m): irregularly flaser-bedded arenite layers separated by platy shell beds with abundant bivalves (Mytiloceramus sp., Meleagrinella elegans (Munier-Chalmas)) and ammonites (almost exclusively St. latiumbilicus, only very rare fragments of Ludwigia), partly chamosite-oolitic.

Ammonites: St. latiumbilicus [M and m], Ludwigia aff. crassa [M], L. armipotens [M], L. cf. subtuberculata [m]

• Bed St-B 6 (0.05–0.15 m): arenaceous marly limestone, occasionally weathered with a rusty rim and a soft, ochre-coloured core. With lenses of bivalve shell debris containing small ammonites (almost exclusively Staufenia).

Ammonites: St. discoidea α [M and m], Ludwigia tuberata [M], Brasilia howarthi [M]

• Bed St-B 7 (0.05–0.15 m): soft marly limestone with burrows, compressed Pholadomya sp., belemnites, very rare ammonites (three specimens).

Ammonites: St. discoidea α [M], Ludwigia murchi­sonae [M], L. subtuberculata [m]

• Bed St-B 8 (0.4–0.6 m): compact, partly arenaceous marly limestone divisible into three subunits:

• Bed St-B 8a (0.1 m): irregularly flaser-bedded arenaceous marly limestones; with platy or rusty layers at the very base. Ludwigia spp. locally very abundant, with large-sized specimens over 20 cm in diameter, accompanied by nuclei and phragmocones of Staufenia, rarely with complete bodychamber.

Ammonites: St. discoidea α [M and m], Ludwigia depilata [M], L. cf. depilata [M], L. tuberata [M], L. armipotens [M], L. reflua [M], L. murchisonae [M], L. subtuberculata [m], Brasilia theobaldi [M], B. elmii [M], B. falcatiformis [M]

• Bed St-B 8b (0.1–0.25 m): arenaceous marly limestone, intercalated with layers of shell debris; bivalves (Mytiloceramus sp., Meleagrinella elegans (Munier-Chalmas)) and ammonites are abundant. Staufenia is common, partly preserved with bodychamber; Ludwigia spp. are rarer than in bed St-B 8a.

Ammonites: St. discoidea α [M and m], Ludwigia depilata [M], L. tuberata [M], L. murchisonae [M], L. armipotens [M], L. reflua [M], L. subtuberculata [m], Brasilia baldii [M], B. theobaldi [M], B. falcatiformis [M], B. howarthi [M]

• Bed St-B 8c (0.15–0.25 m): occasionally, the top of the Staufensis-Bank is formed by an up to c. 8 cm thick marly limestone; sometimes this bed is platy or arenaceous. In most other cases, it was formed by a 2–3 cm thick bed. Most ammonites were recovered from a discontinuous bivalve shell bed that occurred in the uppermost 10–15 cm of the Staufensis-Bank.

Ammonites: St. discoidea β [M and m], Ludwigia aff. murchisonae [M], L. fueloepi [M], L depilata [M], L. reflua [M], L. gradata [M], Brasilia bradfordensis [M], B. elmii [M], Planammatoceras aff. planinsigne [M]

Clayey marl (0.05–0.1 m).

Clayey marl (0.1 m): with scattered siderite concretions, often rusty weathered.

Quaternary cover (0.3–0.8 m): up to the surface c. 0.3–0.8 m talus, loam and soil.

The beds of the Concava-Bank and the Sowerbyi-Oolith (Rieber 1963) should be expected in a distance of c. 2 m above the top of the Staufensis-Bank; however, these beds were not present at our excavation sites. We were even unable to locate these beds anywhere else at the Wochenberg hill, except of its northern hillside, beyond the road L 435.

Within Graphoceratidae, the Staufenia lineage is easily divisable into a succession of only moderately variable chronospecies. In contrast, the taxonomy of Leioceras/Ancolioceras and Ludwigia/Brasilia is much more complex. There are no focussed evolutionary trends observable, and some morphologies can reappear independently multiple times. Moreover, ammonites of these groups vary considerably within a single biohorizon. Plenty of the recorded morphologies are not restricted to a single biohorizon, but range within several succeeding ones. Finally, from some well-sampled Aalenian beds such as the Scissum Bed of southern England (Buckman 1887–1907) or the Lower/Upper Aalenian transition of Bakonycsernye in Hungary (Géczy 1967) an extremely large number of potentially valid taxa were formally described. However, few or no nominal taxa of this time interval were reported from other regions. The distinction of these nominal taxa is difficult. Considering the great variation within this group of ammonites, both in coeval beds as well as in a succession of beds, it is disputable whether to assign a specimen to a taxon described from a stratigraphically older or younger bed. Adding new taxa would even complicate this taxonomic maze. Therefore, both in Leioceras/Ancolioceras and Ludwigia/Brasilia new species should be only introduced based on very strong arguments in favour. Fortunately, this was not necessary in the course of this study.

Despite the partly large samples recovered by bed-by-bed sampling it was often impossible to identify corresponding macroconchs (M) and microconchs (m) – females and males – with accuracy. Specimens of the Tethyan genera Planammatoceras and Tmetoceras are very rare.

The ammonite fauna of the Untere Wilflingen-Bank (formerly: “Comptum-Bank”) in the western Swabian Alb was described by Rieber (1963) in great detail. He determined coarsely ribbed and broad macroconchiate specimens as L. crassicostatum Rieber; all other macroconchs were assigned to L. comptum (Reinecke). In the microconchs, the coarser ribbed forms were distinguished as L. paucicostatum Rieber (the holotype of the latter species originates from the Wochenberg hill), and the weakly sculptured ones as L. striatum (Buckman). Concerning the microconchs, we follow the classification and determinations by Rieber (1963). For the sake of completeness, we here illustrate one example of L. striatum (Fig. 4.5) and one of L. paucicostatum (Fig. 4.9). It is remarkable that at the Wochenberg hill and in the headwaters of the Schörzinger Starzel River microconchs are significanthy more common than in the sections at Gosheim located only a few kilometres farther to the southwest. A possible reason for this variation might be that both living and preservational conditions for microconchs had been more favorable in the present day Wochenberg area due to a calmer environment (Rieber 1963). In Gosheim, macroconchiate specimens of Leioceras with a better rounded bodychamber are more common than at the Wochenberg hill. Thus, we cannot exclude a slight difference in age of the Untere Wilflingenbank at both places; however, this difference is below the biostratigraphical resolution. The former determination of the macroconchs as ‘L. comptumʼ must be rejected since the rediscovered holotype of Reinecke´s Nautilus comptus was found to be a latest Toarcian Pleydellia (Chandler and Callomon 2010). The Leioceras specimens illustrated in Fig. 4 provide an overview on the great variation within adult macroconchs from the Wilflingen-Bank at the Wochenberg hill. We assigned them to the two morphospecies L. crassicostatum Rieber (Fig. 4.1a, b) and – following Chandler and Callomon (2010) – L. goetzendorfense (Dorn) (Fig. 4.2a–4b, 8a, b, 10a, b). Extreme morphologies are very rare (Fig. 4.1a, b [broad section, extremely coarse-ribbed → transitional to Ludwiga]; Fig. 4.10a, b [high section → transitional to Ancolioceras]). In contrast to the illustrated material, most macroconchiate graphoceratids from the Wilflingen-Bank are juveniles. They still lack the typical rounded venter, which is only well developed on the bodychamber of adults. However, the bulk of our specimens is close to the morphology of the specimen illustrated in Fig. 4.4 (compare the specimens in Rieber 1963, pl. 1, figs 2–4, 8, 9, 12, 14).

Tmetoceras scissum (Figs 4.6a, b, 7a, b; Rieber 1963) is a rare Tethyan immigrant in the Jurassic of Swabia (Dietze and Schweigert 2020). Unfortunately, a perfectly preserved specimen of c. 45 mm diameter was lost during preparation.

The taxonomy and determination of the ammonites from the Obere Wilflingen-Bank is extremely complicated, since the stratigraphical position of this fauna is transitional between formally named taxa from older horizons of the Bifidatum Subzone (Opalinum Zone) and younger ones of the Haugi Subzone (Murchisonae Zone), similarly to the recently described case of the slightly younger subfalcatum biohorizon (Dietze et al. 2021b). Usually, the ammonites of the (Untere) Wilflingen-Bank both, in the eastern and western Swabian Alb, are classified in a few macroconchiate and microconchiate taxa (L. “comptum”, L. evolutum, L. crassicostatum and L. striatum, and L. paucicostatum, respectively) (Rieber 1963; Dietze et al. 2021a). By contrast, in Ancolioceras from the Haugi Subzone of the Wutach area and the eastern Swabian Alb plenty of nominal species and varieties are distinguished (Horn 1909; Dietze et al. 2021b). There is a gradual transition between the (morpho-)genera Leioceras and Ancolioceras (see Dietze et al. 2021b). The ammonites from the Obere Wilflingen-Bank exhibit numerous combinations of characters of nominal species, which hampers the determination of individual specimens. We classified all graphoceratid ammonites from the Obere Wilflingen-Bank either as Leioceras Hyatt, 1867 or Ancolioceras Buckman, 1899 [in Buckman 1887–1907] and considered further taxa mostly introduced by Buckman (1887–1907) (e.g., Cypholioceras, Cylicoceras, Geyerina, Hyattina, Mansellia, etc.) as subjective younger synonyms. Their continuous usage would make ammonite taxonomy from the Lower/Upper Aalenian transitional beds extremely complicated.

A relatively small ammonite with a ventrally rounded bodychamber bearing a prominent ribbing (Fig. 5.4) is determined as Leioceras evertens (Buckman, 1899 [in Buckman 1887–1907]). Several ammonites with a rounded bodychamber are assigned to Leioceras goetzendorfense (Dorn, 1935) (Figs 5.8, 6.6); they are morphologically indistinguishable from ammonites of the Untere Wilflin­gen-Bank of the western Swabian Alb. Two relatively involute L. capillare (Buckman, 1928 [in Buckman 1909–1930]) are poorly sculptured and exhibit only a weakly developed ventral shoulder (Figs 5.10, 5.15). Similarly, two microconchiate L. striatum (Buckman, 1899 [in Buckman 1887–1907]; Figs 5.9, 5.16) are mophologically almost identical with specimens of the Untere Wilflingen-Bank.

Due to the gradation from the genus Leioceras into the genus Ancolioceras, some specimens cannot be assigned with confidence to the one or the other genus. Specimens closely resembling L. goetzendorfense (compare Rieber 1963, pl. 1, fig. 12), but with a more regular ribbing than developed in most graphoceratids from the Untere Wilf­lingen-Bank and showing a fastigate venter until the aperture (Figs 5.3; 6.4, 6.5), are included in Ancolioceras viallii (Géczy, 1967). One specimen exhibits the typical ribbing style of A. viallii, but has a very broad section with a rounded venter on the bodychamber (Fig. 6.2); it is clearly intermediate between the genera Leioceras and Ancolioceras and here determined as A. cf. viallii (Géczy). A. noszkyi (Géczy, 1967) (Fig. 5.5) has a very fine ribbing. Specimens determined as A. krymholzi (Géczy, 1967) (Fig. 5.6) and A. subfalcatum (Buckman, 1899 [in Buckman 1887–1907]) (Figs 5.1, 5.11; 5.13) are close to the majority of ammonites of the subfalcatum biohorizon (Dietze et al. 2021b). A. citaae (Géczy, 1967; Fig. 6.1) is recorded from the subfalcatum biohorizon as well. There is a striking resemblance of the latter with the holotype of Cylicoceras undatum Buckman, 1899 [in Buckman 1887–1907]; however, the latter originates from much older beds (opaliniformis hemera) at Haresfield Hill in South England. A. citaae differs from L. crassicostatum Rieber, 1963 by its more slender whorl section, a more involute umbilicus and a slightly higher whorl section. These three species (C. undatum, A. citaae and L. crassicostatum) represent morphological extremes within the intraspecific variation of the respective chronospecies (Dietze et al. 2021a). In lateral view, Ludwigia praecursor Rieber, 1963 looks very close to A. citaae, however, it is distinguished by its ventrally forwardly bended ribs. A very involute, high-sectioned and large-sized specimen (Fig. 6.3) with a sharp venter and a uniform ribbing style is close to A. subacutum (Buckman, 1899 [in Buckman 1887–1907]). Our specimen differs from the latter by a higher number of intercalatory ribs; hence, we prefer a determination in open nomenclature as A. aff. subacutum. A. costatum (Buckman, 1888 [in Buckman 1887–1907]) is another similar form which exhibits characteristic shovel-like thickenings of the ribs on the bodychamber. Two microconchiate specimens (Figs 5.12, 5.14) are assigned to A. aff. substriatum (see Dietze et al. 2021b, pl. 5, fig. a1, 2), since A. subfalcatum is based on a macroconch.

In our stratigraphical analyses, we focus on the beds of the Achdorf Formation and the directly overlying Sowerbyi-Oolith of the Wedelsandstein Formation.

North Germany: Hoffmann (1913) described a rich ammonite fauna from the Aalenian of Sehnde near Hannover. The Sehndensis-Subzone of North Germany includes time-equivalent strata of the latiumbilicus biohorizon, and the Discoidea-Subzone strata of the discoidea α and β biohorizons.

SW Germany: The crassicostatum biohorizon is widespread in the western Swabian Alb (Rieber 1963). A set of beds occurring a few metres above the (Untere) Wilflin­gen-Bank in a section at the Wilflinger Steige near Gosheim contain ammonites which could represent the viallii biohorizon; their description is still in progress. In 2020, the discoidea α biohorizon was recorded by the first author for the first time in Gosheim within a c. 1 m thick, probably only locally developed set of arenaceous limestone beds which were temporarily exposed along the connectiong road to the industrial area Sturmbühl. The somewhat deeper occurring “Schichten mit Staufenia sehndensis” [“beds with Staufenia sehndensis”] at Gosheim (Rieber 1963; Dietze 1989a, b), which are very rich in ammonites and shell detritus, are slightly older than the latiumbilicus biohorizon. Since bed-by-bed collections from further localities of the Swabian and Franconian Alb as well as from the Wutach area and the Upper Rhinegraben valley are still lacking, further correlations at the level of biohorizons are impossible.

France (Franche-Comté): Contini (1969, Tableau I) correlated the ammonite successsion of the French Jura Mountains with the successions of North Germany (Hoffmann 1913) and SW-Germany (Rieber 1963). This correlation was later adopted and revised by Contini et al. (1997, Tableau Va) in a rather confusing way. Different zonal schemes were used for the so-called “biome franco-germanique” [partly inluding the French Jura Mountains] on the one hand and the Submediterranean and Subboreal provinces on the other. Most strangely, the discoidea-Horizont sensu Rieber was totally ignored within these “horizons” of the “biome franco-germanique”. The stratigraphic position of the “Horizon à Sehndensis” [biome franco-germanique] was placed between the “Horizon à Obtusiformis” and the “Horizon à Murchisonae” [of the Submediterranean/Subboreal provinces] in Tableau Va; however, in the corresponding text it was explained that the faunas of the “Horizon à Sehndensis” in the French Jura Mountains and in SW Germany [biome franco-germanique] are identical with the fauna of the “Horizon à Obtusiformis” [Submediterranen/Subboreal provinces].

This is why we prefer the more consistent and reproducable subdivision of Contini (1969) for our correlation between SW Germany and the French Jura Mountains. Continiʼs “Horizon à Staufenia sehndensis” with St. sehndensis und Ludwigia obtusiformis is slightly older than the latiumbilicus biohorizon at the Wochenberg hill, where L. obtusiformis has not been recorded yet. At Gosheim, only a few kilometres south of the Wochenberg hill, L. obtusiformis is recorded and co-occurs with smaller-sized St. “sehndensis” (Dietze 1989a, p. 125 figure bottom right, 1989b, p. 172 top left); hence, we suspect these beds correlate with the French Horizon à Sehndensis. The discoidea α und discoidea β biohorizons correspond to the Horizon à Murchisonae of the French Jura Mountains.

South England (Dorset): Despite of numerous previous studies (Buckman 1887–1907; Callomon and Chandler 1990; Chandler 1982, 1997), a correlation between SW Germany and S England remains problematic. The main reasons are that Staufenia discoidea and St. staufensis do not occur in S England and the corresponding faunas with Ludwigia spp. from England are generally more weakly sculptured and more rounded in ventral aspect than those of SW Germany (Chandler et al. 2012). The faunal horizon of Ludwigia obtusiformis with St. sehndensis, L. obtusiformis and Ancolioceras spp. (Chandler 1982, 1997; Callomon and Chandler 1990, 1997) must be slightly older than the latiumbilicus biohorizon based on the same arguments as explained above for our correlation with the French Jura Mountains. For a correlation of the faunal horizon of L. patellaria only its index L. patellaria can be used (Callomon and Chandler 1990). Since specimens of Ludwigia are extremely rare in the latiumbilicus biohorizon of SW Germany, it is impossible to decide whether both horizons could be time-equivalent or which one is the older. Possibly, the latiumbilicus biohorizon is the younger one of the two, since the few Ludwigia specimens already show a smooth band along the keel; this is not the case in L. obtusiformis. The discoidea α und β biohorizons correlate with the faunal horizon of L. murchisonae. The newly introduced viallii biohorizon is either slightly older or coeval with the comptocostosum horizon of Chandler and Callomon (2010).

Scotland (Isle of Skye): Morton and Hudson (1995) divided the rock succession at the type locality of Ammonites murchisonae Sowerby, 1827 – the type species of Ludwigia Bayle, 1878 – into the same faunal horizons as in South England (Callomon and Chandler 1990). The beds O 7–O 11 of the Ollach Sandstone Member were assigned to the Murchisonae Subzone, with the two faunal horizons of L. patellaria and L. murchisonae. These beds correlate with the latiumbilicus, discoidea α und discoidea β biohorizons in the Wochenberg section.

Switzerland (Central Swiss Jura): Christ (1999, 2000) divided the rock in the central Swiss Jura Mountains into a succession of several ammonite faunas; however, his study is merely hypothetical since it is mostly based on imprecisely collected museum material (collection Lieb/Bodmer). His fauna 6 “murchisonae und ssp.” approximately correlates with the discoidea α und β biohorizons.

In the Aalenian of Luxembourg, Sadki et al. (2020) divided the Murchisonae Subzone into biohorizons; however, the few specimens of Ludwigia spp. presented in their study do not allow a precise correlation. A high-resolution correlation with further European regions is impossible due to the lack of published data.