New records of ostracods and ammonites from the Aalenian (mainly Concavum Zone) of the Zollernalb (Swabian Alb, SW Germany)

The lithostratigraphy and ammonite/ostracod biostratigraphy and the accompanying fauna of several sections and outcrops around the Hohenzollern (Zollernalb, SW Germany), ranging from the topmost Opalinuston Formation (uppermost Lower Aalenian) to the basal Wedelsandstein Formation (lowermost Lower Bajocian) are described and analyzed. The study of ostracods from 41 samples from the Aalenian and Lower Bajocian of the Heiligenbach, Hausterberg and Roschbach sections has yielded approximately 4,100 specimens. Significant changes in the ostracod assemblage occur at the base of the Lower Aalenian “Comptum” Subzone, at the Bradfordensis/ Gigantea subzonal boundary, at the Bradfordensis/Concavum zonal boundary and at the Aalenian/Bajocian boundary (Concavum/ Discites zones). A minor change occurs above the Calceola-Bank within the Concavum Zone. The following new ostracod species are described: Cytheropterina crassicostata sp. nov., Eucytherura eberti sp. nov. and Eucytherura foveolata sp. nov. In addition, 15 presumably new species are briefly described; 10 ‘incertae sedis’ taxa are figured, but left in open nomenclature. The ammonite faunas of the Inopernabank and Konglomeratbank beds (Upper Aalenian, Bradfordensis Zone, Gigantea Subzone) as well as the ammonite faunas from the Calceolabank and Rostrote Kalkbank beds (Upper Aalenian, Concavum Zone, Concavum Subzone, cavatum biohorizon) are described and correlated with those of other areas.


Introduction and previous studies
In the context of the field works on the occasion of the investigation of the lithostratigraphy as well as the ammonite and ostracod biostratigraphy of the "Unterer Wedelsandstein" and "Sowerbyi-Oolith" members (Wedelsandstein Formation; Lower Bajocian) of the Zollernalb (Dietze et al. 2019), the survey of the sections was expanded to the underlying beds of the Achdorf Formation (uppermost Lower and Upper Aalenian). Surprisingly, some of these beds yielded a rich ammonite fauna. This was quite unexpected, since Hahn (1975) mentioned that ammonites are very rare in the Upper Aalenian of this area. The microfauna samples are very rich in ostracods. Therefore, we decided to publish the lithostratigraphical and biostratigraphical results regarding the Achdorf Formation and parts of the Opalinuston Formation in a separate publication, which is presented here.

Eastern tributary of the Heiligenbach coming from the Sießenwald, approx. 30 m east of the "Hunnengrab"
In the river bed there is a light grey, hard limestone bed (0.15 m) with a rust-coloured rim and many burrows. Its lithology resembles the lower bed of the Rostrote Kalkbank from the Mühlbächle section at Jungingen. An indeterminable ammonite fragment. A larger Euaptetoceras sp.

Bisingen-Thanheim (Heiligenkopf)
Since we did not find Aalenian ammonites in this outcrop, we here refer to Dietze et al. (2019) for the description of the section.

Methods
For the present study, a total of 41 samples were taken in September 2018 and September 2019. Individual samples, which were already taken in 1988 at the Heiligenbach, were included in the investigation. Microfossils have been extracted by first drying the samples (0.5-1 kg), breaking them down with the aid of hydrogen peroxide (3% solution of H 2 O 2 ) and then sieving them under water. The residues were then cleaned by boiling them for 15 minutes in a moderately concentrated sodium chloride solution (3 teaspoons NaCl / 0.25 l water). From the fractions > 0.5 mm and > 0.315 mm of the residues, 3-5 trays were examined. From the fractions > 0.2 mm and > 0.15 mm we examined 3 trays.
Photographs were taken using SEM in Stuttgart (SMNS).

Results
Introductionary remark: The investigation of the Geisingen clay pit (Franz et al. 2018) has considerably increased the knowledge about the ostracod fauna of the Aalenian of SW Germany. The present investigation of approximately the same part of the section showed very good agreement in the Opalinum zone. However, several species are much rarer in the sections studied herein. In addition, strong changes in thicknesses and facies are noticeable. The vertical distribution of the species first described in Franz et al. (2018)  The 41 samples yielded a total of 4,149 specimens, ranging from 0 to > 700 specimens per sample. For a semi-quantitative analysis of the composition of the ostracod assemblages the greater numbers of single (right or left) valves were counted as 1, resulting in a total of 2.758 individuals.
A total of 108 species were identified, 329 specimens remained undetermined. From 34 species of the Upper Opalinuston Formation, 22 do not cross the boundary to the overlying Achdorf Formation. The Achdorf Formation yielded a total of 82 species including the 12 already known from the Opalinuston Formation. In the Lower Wedelsandstein Formation 4 new species appear, 11 persist from the Aalenian.
At zone or subzone level, two relative maxima in the total number of species are recorded in the Opalinum Subzone and Concavum Zone (Table 4). The highest number of species in the Concavum Zone correlates with the highest number of newly reported species as well as the total number of genera and families.
Short descriptions of new species of cytherurids (Eucytherura sp. 3-11, Procytherura sp. 2, P. sp. 5, Procytheropteron sp. 1) in our material are excluded. Ten presumably new species were found only in numbers of one to five specimens and could not be assigned to any known genus. For this reason, these taxa were left in open nomenclature. In the samples of the fine sandy layers, the ostracods are partly covered by remnants of sediment (mainly quartz grains) and/or fragmentarily preserved.

Systematic descriptions
In the following, the ostracod taxa that were found in the studied sections are listed in systematic order with information on their known occurrence. For detailed lists of synonyms, reference is made to Franz et al. (2018).  Material. 30 C, 585 RV, 517 LV in samples He19-14-28, Mue19-1, Ha19-2-5 and Ro19-1-2.
Remarks. This ?subspecies was first described and figured from Thanheim (Dietze et al. 2019).
Remark. The specimen is very small and preserved in pyrite and could therefore not be assigned with certainty to any species.
Description. A species of Praebythoceratina which is distinguished by the combination of the following features: an U-shaped lobe with an irregularly reticulate spine in the ventro-central area. Its anterior branch is strongly convex and irregularly reticulate, with dominant subvertical ridges. The posterior branch is broad and gently arched and covered with irregular pores. Along the anterior margin there is a pronounced bulge, which is also irregularly reticulate.

Genus "Monoceratina" Roth, 1928
Remarks. This genus is in need of a revision and currently of unclear composition (Brand 1990. Type locality. Heiligenbach valley near Hechingen-Beuren (SW Germany).
Diagnosis. Medium size. Subtriangular outline, with broad, rounded irregular ribs; the underside of the alate extension being smooth except for its posterior part.
Description. Carapace medium-sized, subtriangular. Right and left valve (identical in outline and ornamentation): Anterior margin symmetrically rounded. The dorsal margin is straight, medianly slightly concave. The ventral margin converges, partly straight or in a slight curve, to the acuminate posterior end. The ventral margin is obscured by a broad triangular wing. The anterior and posterior marginal zones are covered with roundish pits. The anterior marginal zone is offset with a small, asymmetrically rounded step against the lateral surface. A broadly rounded, mediodorsally-anteroventrally running rib forms a second step running diagonally over the anterior half of the valve. From this rib another broad rib branches off slightly below the middle, running subvertically towards the edge of the wing. The adjoining surface, which ends in the symmetrically rounded tip of the broad wing, is characterised by three wide, flat, bulbous elevations separated by wide furrows and pits. The furrows and pits as well as the ribs and depressions are covered with roundish secondary pits. Posteriorly, this area is bounded by a slightly curved, subvertical, rounded rib that tapers from dorsal to ventral. The posterior marginal zone is offset with a further, almost straight, subvertical step. Marginal zone wide anteriorly ( Fig. 10: 13). The underside of the wing, which in ventral view forms a rectangular triangle, is smooth, except for its posterior third. A triangular area is covered by small grooves which are most prominent along the posterior margin of the wing. Hinge and other internal details are not observed.
Comparisons. Cytheropterina crassicostata resembles in outline Cytheropterina bicuneata (Braun) as reported by Franz et al. (2018) from the Aalenian and Lower Bajocian of SW Germany, and Cytheropterina cribra Fischer, 1962 (p. 339, Fig. 25: 8-11) from the Toar-cian to Bajocian. The main differences are the coarse, softly rounded ornamentation, the smooth underside of the wing and the bigger size.
Distribution. Lower Toarcian to Upper Bajocian; France, Germany, Ireland, Spain, N Switzerland. Material. 2 RV in samples He19-12 and from the Geisingen clay pit.
Description. Very small, subovoidal outline in lateral view. Lateral surface with five broadly rounded ribs, subhorizontal in the midventral to posteromedian area; in the anterior half of the valve bent anteroventrally. Roughly reticulated in the region of these ribs by subvertical transverse ribs. Description. Very small, subtriangular outline in lateral view. Lateral surface weakly ornamented by two fine longitudinal ribs delimiting a spindle-shaped field, posteriorly rounded and anteriorly pointed. Parallel to the anterior margin there is a third, also very fine rib. Another middorsal-midanterior rib halves the acute-angled triangular field between the frontal rib and the upper longitudinal rib.

Genus Eucytherura Müller, 1894
Eucytherura eberti sp. nov. Etymology. In honour of the German palaeontologist Martin Ebert, who initiated the investigation of the Geisingen clay pit with his extensive preliminary work.

Diagnosis.
A new species of Eucytherura with broad, smooth posterodorsal, frontal and ventral ribs. Intercostate areas weakly reticulate.
Description. Very small, subrectangular. Left valve slightly larger than right with anterodorsal and posterodorsal overlap. Anterior margin weakly rounded with extremity below mid-height; posterior margin pointed in right and bluntly rounded in left valve, apex above mid-height. Posterior cardinal angle pronounced in both valves; anterior cardinal angle more rounded in right than in left valve. Dorsal margin slightly convex to straight; ventral margin medianly slightly convex. Greatest height at anterior cardinal angle; greatest width antero-ventral-ly; greatest length above mid-height. Ornament consists of a series of broad longitudinal ribs and swellings, and with weakly reticulate intervening areas. A broad, posteriorly weakly alate rib extends from a postero-ventral position across the ventro-lateral surface of the valve, terminating antero-ventrally. A similar broad rib extends mid-posteriorly to mid-dorsally. The eye tubercule is well developed and is connected to a narrower frontal rib, which parallels the anterodorsal margin. A less prominent second rib or elongate swelling parallels the latter mid-anteriorly. Intercostate areas are weakly reticulate, with a characteristic row of small elongate pits above the muscle-scar field. 3-4 small marginal denticles occur anteriorly. Normal pores few and wide-spaced. Internal details not observed.
Comparisons. Euytherura eberti closely resembles Eucytherura scottia Whatley, 1970 from the Callovian and Oxfordian of Scotland. It differs mainly in the length of the dorsal rib, the absence of the anterior tubercles, being replaced by two parallel ribs and the pits above the musclescar-field.
Diagnosis. A small-sized species of the genus Eucytherura with the following characteristics: pitted lateral surface with a fine median rib.
Description. Very small, subrectangular. Left valve slightly larger than right with dorsal overlap. Anterior margin rounded with extremity slightly below mid-height; posterior margin pointed in right and bluntly rounded in left valve, apex above mid-height. Posterior cardinal angle rounded; anterior cardinal angle pronounced in both valves, slightly more rounded in right valve. Dorsal and ventral margins slightly convex in both valves. Greatest height at Material. 25 C, 4 RV, 4 LV in samples He19-6-18 and from the Geisingen clay pit.
Description. Very small, subrectangular. Left valve slightly larger than right with dorsal overlap. Anterior margin rounded with extremity slightly below mid-height; posterior margin pointed in right and bluntly rounded in left valve, apex above mid-height. Posterior cardinal angle rounded; anterior cardinal angle pronounced in both valves, slightly more rounded in right valve. Dorsal margin straight in right valve and slightly convex in left valve. Greatest height at anterior cardinal angle; greatest length above mid-height. Shell surface regularly reticulate with rounded meshes of uniform size. Hemispherical eye-tubercle well developed. Starting from the eye-tubercle, a fine frontal rib, straight in the left valve, convex in the right valve, runs parallel to the anterodorsal margin. A second rib runs subvertically from the eye-tubercle and then bends mid-anteriorly to the anterior margin. A ventral rib starts posteroventrally and ends midventrally with its anterior end slightly ascending towards the ventromedian side. A short subvertical ridge is located at the posterior cardinal angle. Internal details not observed. Material. 1 C in sample He19-19; 5 RV, 1 LV from the Geisingen clay pit.
Description. Very small, subovoidal. Anterior margin asymmetrically rounded with extremity below mid-height; posterior margin pointed, apex above mid-height. Posterior cardinal angle rounded; anterior cardinal angle pronounced in both valves. Dorsal margin slightly convex, ventral margin convex. Greatest height at anterior cardinal angle; greatest length above mid-height. Shell surface irregularly and coarsely reticulated. The most striking feature is the gently undulating surface with slight anterodorsal, middorsal and anteroventral depressions. The eye-tubercle is fused with a short, indistinct frontal rib. A short bulge-like rib is located at the posterior cardinal angle. Internal details not observed. Occurrence. Upper Aalenian, Bradfordensis Zone (Gigantea Subzone) to Concavum Zone; SW Germany.

Eucytherura sp. 10
Description. Very small, subovoidal. Anterior margin asymmetrically rounded with extremity below midheight; posterior margin rounded, apex above midheight. Anterior and posterior cardinal angles rounded; both slightly more pronounced in right valve. Dorsal margin slightly concave in ther right valve, slightly convex in the left one. Greatest height at anterior cardinal angle; greatest length above mid-height. Shell surface reticulate, with wide rectangular to polygonal meshes. Eye-tubercle absent.
Right valve: A long, well-defined frontal rib runs from the anterior cardinal angle to the anteroventral margin. The lateral surface is characterized by three fine ribs, the first of which starts in the median region, runs a short distance towards the anterior cardinal angle, then bends perpendicularly towards the anterior margin and after a second 45° bend towards the anteroventral margin. The median rib starts mid-posteriorly above mid-height and ends anteromedianly below mid-height. A long, upwardly curved ventral rib runs from the posteroventral margin to the anteroventral region. One (or two) ribs parallel the ventral rib on the ventral side of the valve.
Left valve: The frontal rib is slightly curved (preservation?) and only weakly developed. The (dorso) median -mid-anterior rib meets the ventral rib at an 60° angle. The median rib starts mid-posteriorly above midheight and ends anteromedianly at mid-height. Two ribs parallel the ventral rib on the ventral side of the valve. Further, especially internal details were not observed, partly for preservation reasons.
Description. Very small, subrectangular to subtriangular. Anterior margin rounded with extremity slightly below mid-height; posterior margin pointed, apex above midheight. Posterior cardinal angle rounded; anterior cardinal angle pronounced in both valves, slightly more rounded in left valve. Dorsal straight to slightly concave, ventral margin straight to slightly convex. Greatest height at anterior cardinal angle; greatest length above mid-height. Shell surface strongly reticulate, including the anterior and posterior margins. The coarse-meshed, very prominent reticulation is divided by three ribs, which in the median area delimit an approximately circular area. A middorsal -anteromedian rib, a second middorsal -posteromedian rib, and a ventral rib that is strongly curved up in the anterior midventral section towards the anteromedian region. Another rib starting at the anterior cardinal angle parallels the anterior edge of that circular area approximately halfway to the anterior margin. Eye-tubercle absent; internal details not observed. Remark. The single (juvenile ?) specimen is only tentatively placed in this genus due to its small size and poor preservation.
Description. Very small, triangular. Anterior margin rounded with extremity slightly below mid-height; posterior margin pointed, apex below mid-height. Cardinal angles rounded in left valve, cardinal angles pronounced in right valve.
Right valve: Dorsal margin straight, medianly slightly convex, ventral margin slightly convex, medianly partly obscured by a median overhang of the lateral curvature. The punctate shell surface is longitudinally and vertically strongly curved with a ventral overhang. The curvature is concavely recessed in the uppermost area along a sharp oval bend, ending in a weak anteromedian lobe. A narrow anterodorsal depression parallel to the anterior margin is limited by a short, slightly curved frontal rib, ending above mid-height.
Left valve: Dorsal margin strongly convex, otherwise identical to the right valve.
Hinge due to poor preservation not clearly visible, possibly merodont; other internal details not observed.

Remarks.
Our specimens resemble Procytheropteron gramanni Brand, 1990 (plate 9: 10) from the Upper Bathonian of NW Germany; they differ in age and in the coarser ornamentation and reticulation. Material. 2 LV in sample He19-24 and from the Geisingen clay pit.
Description. Very small, ovoidal. Anterior margin almost symmetrically rounded; posterior margin pointed, apex at mid-height. Cardinal angles rounded in the left valve.
Dorsal margin straight to slightly convex, ventral margin convex, medianly partly obscured by a median overhang of the lateral curvature. The complete lateral surface is decorated with vertical, broadly rounded ribs. The ribs in the median part of the valve are irregular, interrupted at about mid-height, and offset laterally against each other. The vertical ribs are framed by a curved ventral rib, which is also rounded, and a similar dorsal rib, which almost touch each-other mid-posteriorly.
Internal details not observed.
Remark. Ohmert (2004) mentioned this species as a probable ancestor of Aphelocythere recta from the top of the Concavabank.
Description. Very small, subrectangular. Anterior margin rounded with extremity slightly below mid-height; posterior margin rounded, apex above mid-height. Cardinal angles rounded in both valves, slightly more pronounced in left valve. Dorsal margin straight, ventral margin slightly convex. The shell surface is smooth, with a number of pits, which are difficult to recognize due to bad preservation. Internal details not observed.
Remark. Vernoniella ? caytonensis was described from the Blagdeni Subzone in England; our specimen comes from the Concavum Zone and therefore has been tentatively placed in this species.

Remark.
We have set Asciocythere in quotation marks, because the generic assignment of this species is doubtful.
Remark. The specimens from the Roschbach section closely resemble Praeschuleridea subtrigona from the Upper Bajocian to Upper Callovian. It is only tentatively placed in this species because of the remarkable difference in age. Material. 1 C, 2 LV in samples He19- 17-25. Distribution. Toarcian to Aalenian; Germany, Ireland.
Description. Medium-sized, subovate. Left valve larger than right valve, overlapping along complete outline. Anterior margin slightly asymmetrically rounded, extremity just below mid-height. Posterior margin triangular, upper margin straight, lower margin convex, the two joining at an angle below mid-height. Dorsal margin convex, ventral margin convex with slight concavity in front of midlength in the right valve. Anterior cardinal angle rounded, posterior cardinal angle sloping straight to the posterior margin. Valve ventrolaterally swollen. Small-sized pits irregularly distributed over the anterior valve surface, significantly denser in the posterior third. A narrow channel with densely arranged pits parallels the anterior margin. Anteroventrally and posteroventrally there is a row of finest denticles.
The partly broken (? paleohemimerodont) hinge shows terminal serrated teeth and remains of teeth in the median hinge area of the right valve.
Remark. This specimen resembles Pleurocythere kirtonensis in the arrangement of the ribs. In contrast to P. kirtonensis the ribs are broad and rounded. Possibly the median rib touches the ventral rib anteroventrally. More material is required for clarification.
Remark. The two specimens may represent an ancestor of the genus Pleurocythere.
Remark. In addition to the differentiation from Acrocythere pumila in Plumhoff, 1963, it should be noted that the reticulation between the median rib and the ventral rib in the posterior section is alternating here, whereas it is clearly linear in A. pumila.
Description. Anterior margin broadly rounded, accompanied by a flat marginal bulge. The dorsal margin slightly convex, with the greatest height in front of midlength of the valve. Posterior end flat, with narrowly rounded posterior margin. Ventral margin obscured by the the overhanging ventro-lateral curvature. The central part of the valve is ventrally strongly inflated, and clearly set off against the anterior and posterior ends. Remnants of two ventral ribs are visible parallel to the ventral margin. The remaining part of the valve shows only weak hints of a very fine, irregular reticulation.
Occurrence. Lower Aalenian, Opalinum Zone; SW Germany. The evolution within the Graphoceratidae occurred in a chronocline ranging from the lowermost Aalenian (Opalinum Zone, Opalinum Subzone) to the lowermost Bajocian (Discites Zone), with an immense morphological variability within each of the temporally succeeding faunas. In this plexus, individual morphologies sometimes have a long temporal range, whereas the variability of the succeeding faunas as a whole shifts -that is the reason why we can distinguish and define faunal biohorizons. Faunal biohorizons reflect the change of variation in the course of evolution of ammonites, here of Graphoceratidae (e.g., Chandler 1997Chandler , 2019Chandler and Callomon 2009;Dietze et al. 2014Dietze et al. , 2017. There is a gradual change from one genus to the next, so that we can -e.g., in the case of the ammonites under study here -find Graphoceras morphologies together with Brasilia morphologies coeval in a single bed, accompanied by specimens showing a mixture of characters of both morphogenera. In the literature, there are many attempts to classify the plexus of the Graphoceratidae into categories (families, subfamilies, morphogenera, morphospecies). The results of these attempts and the erection of new genera and species depended often by chance, depending on where the author had material from, often without any accurate stratigraphy. The great number of genera and species described in the literature (e.g. Buckman 1887Buckman -1907Horn 1909;Hoffmann 1913;Althoff 1940;Rieber 1963;Géczy 1967;Contini 1969;Ureta Gil 1983;Henriques 1992;Chandler 1997;Howarth 2013) does by no means reflect the number of monophyletic genera and biological species, which was in fact much smaller (Chandler and Callomon 2009). These authors demonstrated the variation of a palaeobiospecies of the Leioceratinae, Leioceras comptocostosum, within one timeslice of the Scissum Zone (Lower Aalenian).

Gen. et sp. indet. 12
We here determined the ammonites conventionally as morphogenera and morphospecies, since we do not have enough material to describe these ammonites chrono-or (palaeo)biospecifically. However, it is most likely that all graphoceratid ammonites from the cavatum horizon described here represent a single palaeobiospecies.
The ammonites from the "Comptum" Subzone are represented by L. "comptum", L. crassicostatum, L. evolutum, L. paucicostatum and L. striatum. They are significantly smaller than the L. "comptum" faunas from the Wochenberg and Gosheim (western Swabian Alb) which comprise more evolute morphs. These ammonites will be described later in detail.

Family Hammatoceratidae Buckman, 1887, Subfamily Hammatoceratinae Buckman, 1887
A single record from the Inopernabank (Fig. 14: 1a-c) resembles in its nucleus Bredyia diadematoides (Mayer) as figured by Rieber (1963) from Kappishäusern near Metzingen (Rieber 1963); however, its body chamber recalls the slightly more evolute Planammatoceras planiforme Buckman (typical of the Lower and lower Upper Aalenian; Kovács 2009;Sandoval et al. 2020) or Pl. lep-siusi (Gemmellaro). Due to the combination of these characters we here determined this ammonite as Planammatoceras sp. Most of the few hammatoceratids from the cavatum biohorizon of the Concavum Subzone in the studied sections are rather large, with smooth, high-oval outer whorls, very complex suture lines and a narrow umbilicus on the inner whorls ( Fig. 14: 2a, b; Fig. 17: 4). The best match in literature we could find is with Euaptetoceras infernense sensu Buckman. The original type series of E. infernense (Roman) consists of small nuclei, which are very similar to the innermost whorls of the ammonite figured on Fig. 14: 2a, b. A more evolute variant is E. cf. kochi (Prinz) (Fig. 24: 1a, b). There is a striking homoeomorphy of this specimen with Brasilia decipiformis or Sonninia carinodiscus (Quenstedt [LT: Sonninia sowerbyi carinodiscus Quenstedt, 1886, p. 502, pl. 63 , Fig. 3]). A fragmentary E. cf. euaptetum (Fig. 23: 1a-c) recalls in its habitus already the slightly younger E. amplectens; however, the umbilicus of the latter is more involute. These smooth, large-sized hammatoceratids already resemble their presumed descendants, the Early Bajocian Fissilobiceras ovale (Quenstedt). A nearly complete compressed specimen from bed 49 of the Heiligenbach section (SMNS 70602) belongs to the genus Euaptetoceras as well; however, due to its bad preservation a specific determination is impossible.

Murchisonae Zone (samples He19-15-16)
The samples from the clays above the "Doppelbank" 20 + 21 yielded 126 specimens of 17 species, 12 of which were found in single specimens. Homocytheridea sp. 1 differs from Homocytheridea cf. punctulata from the Concavum Zone in the Geisingen clay pit. The stratigraphic distribution of Homocytheridea in the Upper Aalenian can be clarified only after investigation of further material.

Bradfordensis Zone, Bradfordensis Subzone (sample He19-17)
In this sample, we found 12 species (only 25 specimens), the majority of which are again represented by single specimens. Among the newly appearing species the solely abundant Progonocythere scutula (13 specimens) is particularly noteworthy. It was first described by Franz et al. (2018) from the Geisingen-Oolith (Gigantea Subzone). Progonocythere scutula and Gen. et sp. 9 Tesakova were observed in this sample only. A stratigraphical interpretation is not possible so far.
As already observed in Geisingen (Franz et al. 2018) and Thanheim (Dietze et al. 2018), Kinkelinella levata -contrary to Ohmert (2004) -already occurs in the Bradfordensis Zone. The lower boundary of the Levata ostracod zone must therefore be significantly shifted downwards.

Concavum Zone (samples He19-21-28, Mue19-1, Ha19-1-3, Ro19-3-5)
The Concavum-Zone comprises the claystones immediately below and above the Inopernabank up to the Sowerbyi-Oolith. Since the claystones above the Rostrote Kalkbank are not exposed along the Heiligenbach creek, their basal part was sampled at the Mühlbächle creek in Jungingen and, for comparison purposes, at the Roschbach in Balingen-Zillhausen. The 14 samples obtained there show ostracod (and foraminifers) assemblages relatively rich in species and individuals. The upper half of these claystones and the basal Wedelsandstein Formation were sampled in the Hausterberg section. The claystones in this level are fine sandy and very poor in microfossils. In some samples only one foraminiferal and one ostracod species were found in small (foram.) to very small (ostr.) numbers.
This assemblage (including the samples from the Roschbach valley) comprises 2,365 specimens from 58 species, 34 of which appear for the first time in this section. The two species of Cytheropterina are very conspicuous, but Cytheropterina alacostata is often represented by very small specimens.
Camptocythere pusilla, the index species of the Pusilla Ostracod Zone (Ohmert 2004), has been found here in large numbers. The very noticeable Plumhofficythere clavatoides, which also occurs in Northern Germany (Plumhoff 1963;Luppold 2003) and England (Bate 1963b), is obviously limited to the Bradfordensis Zone (Gigantea subzone) and Concavum Zone and would therefore also have stratigraphic significance.
Eucytherura eberti sp. nov., which has been found in rare specimens from the uppermost Opalinum Zone upwards, has its acme at this level. A number of further, mostly small species appear here for the first time. Although they are partly very conspicuous (e.g., ? Cytheropteron sp. 1, Eucytherura sp. 10), they are rather unsuitable for stratigraphic purposes due to their scarcity. Additionally, some of these rare species occur earlier elsewhere. A range chart for the Achdorf Formation is given in Appendix 2.

Opalinum Zone
Opalinum and "Comptum" subzones: The strata of the Opalinum Zone were not in the focus of this investigation. However, the Opalinum Subzone reaches at least up to the "Wasserfallschichten" in the area. About 8 m above the "Zopfplatten" of the Heiligenbach section the "Comptum" Subzone is verified by numerous small-sized ammonites of the L. "comptum" -L. evolutum group.

Murchisonae Zone
At present, we cannot confirm strata of this age with ammonites.

Bradfordensis Zone
Bradfordensis Subzone: Beds 20-22 in the Roschbach section and bed 2 of the Mühlbächle section belong to the Bradfordensis Subzone. Ammonites are Brasilia bradfordensis and Staufenia staufensis.
Gigantea Subzone: For the moment, we place the ammonite fauna of the Inopernabank bed into the uppermost Gigantea Subzone. The graphoceratid fauna of this bed itself is not diagnostic enough to decide definitely, if this bed should be placed in the youngest Gigantea Subzone (younger than decipiformis biohorizon) or in the oldest Concavum Subzone (older than cavatum biohorizon). However, the single Planammatoceras sp. is very close to some of the hammatoceratids from the decipiformis biohorizon (Gigantea Subzone) of Geisingen, but very different from the hammatoceratids of the cavatum biohorizon (Concavum Subzone). Hence, we tentatively assign these beds in the Gigantea Subzone. Ammonites: Brasilia decipiens, Graphoceras cavatum, G. cf. caduciferum, G. aff. fallax, Ludwigella tenuis, L. aff. tenuis, L. attenuata, L. attracta, Planammatoceras sp. Formosum Subzone: There is no evidence for this subzone in the Zollernalb.

Discites Zone
The Sowerbyi-Oolith bed belongs to the Discites Zone (see Dietze et al. 2019). 6. Correlation 6.1 Ostracods (M. Franz) As Plumhoff (1963: 59) already stated, species of the genera Cytherella and Cytherelloidea dominate in the Upper Aalenian of the Swabian Alb, while they are absent in NW Germany in sediments of the same age. Nevertheless, the correlation succeeds by means of the genera and species occurring at different frequencies in both parts of the basin as listed in Plumhoff (1963: 59). Additionally, Plumhofficythere clavatoides Luppold (= Cytheridae, n. gen. sp. nov. 1 in Plumhoff 1963) is now also known from several sections in SW Germany.

Opalinum Zone
Of the 34 species detected in the Heiligenbach section in the upper part of the Opalinuston Formation, 21 species are restricted to the Opalinum Zone or occur here for the last time. In accordance with the Geisingen clay pit (Franz et al. 2018 The ostracod assemblage of the upper Opalinuston Formation, Zillhausen Subformation (Franz and Nitsch 2009) can be well correlated with neighbouring regions. Although the zonal index Aphelocythere kuhni is missing here, Aphelocythere pygmaea, Acrocythere pumila and Metacytheropteron opalinum are also indicative for the upper Opalinum Zone in the Western and Middle Swabian Alb (Dilger 1963;Franz et al. 2018), Northern Germany and Northern Switzerland -there additionally Eucytherura plumhoffi and Cardobairdia tesakovae.

Opalinum Zone ("Comptum" Subzone) to Murchisonae Zone
(2018) mentioned also Praeschuleridea punctulata and Kinkelinella fischeri. The composition of the ostracod assemblage in northern Germany is very different. According to Ainsworth (1986), Cytherella apostolescui is already present in the Toarcian of the Fastnet Basin (off Ireland).

Bradfordensis Zone
The ostracod assemblage of this part of the section shows good accordance with that of the Geisingen section with 15 common species. In contrast, the similarities with Dilger (1963) are limited to Aphelocythere dilgeri and Cytherelloidea lordi.
Progonocythere scutula, first described from the Geisingen Oolite (Gigantea Subzone; Franz et al. 2018: 78), occurs in the Heiligenbach section only in sample 17 (below the Staufensisbank), which presumably corresponds to the Bradfordensis Subzone. Due to the rarity of this species, a further stratigraphic interpretation is not possible.
The samples following higher up yielded Balowella catena, an index species of the Ohmerti-catena assemblage (Franz et al. 2018: 82). The second index species, Pleurocythere ohmerti, occurs here only above the Konglomeratbank, in the Concavum Zone.
Apart from the zonal index species Camptocythere pusilla, Plumhofficythere clavatoides (Cytheridae, n. gen. sp. nov. 1 Plumhoff) is restricted to the Concavum Zone in northern Germany (Plumhoff 1963: 55). The latter occurs very rarely already in the Gigantea Subzone in Geisingen (Franz et al. 2018). Reisdorf et al. (2016) and Tesakova (2017) did not mention any of the characteristic species of the Concavum Zone, which is a very thin interval in Northern Switzerland.

Ammonites
Herein we focus on the ammonites from the Inopernabank up to the Rostrote Kalkbank.
SW Germany: From the few data available it is most likely that the ammonites from the Inopernabank and the Rostrote Kalkbank are slightly younger compared to the ammonites from the decipiformis biohorizon of Geisingen (westernmost Swabian Alb). The few Graphoceras specimens from the Inopernabank are slightly more depressed and more involute compared to the "Graphoceras-morphology" of B. decipiformis (in a chronospecific sense as described in Dietze et al. 2014). Furthermore, Euaptetoceras infernense sensu Buckman -typical of the Concavum Subzone (Chandler and Sole 1996) -is unknown from the decipiformis biohorizon at Geisingen, where the highly variable Bredyia diadematoides and Planammatoceras spp. are the most common hammatoceratids; the latter was also recorded in the Inopernabank. Very close in depositional age to the Inopernabank and to the Calceolabank is the "Concava-Bank" around Metzingen and Kappishäusern (Middle Swabian Alb) (Rieber 1963). However, these outcrops and their ammonite content is still under investigation. Possibly the sections around Metzingen and Kappishäusern are slightly condensed.
The cavatum biohorizon (index species: Graphoceras cavatum; Calceolabank and Rostrote Kalkbank) is younger compared to the decipiformis biohorizon of Geisingen (Diet ze et al. 2014) and younger than the ammonite faunas from the underlying Inopernabank and Konglomeratbank. The decipiformis biohorizon is characterised by smooth, large-sized Brasilia decipiformis, which occur only rarely in the cavatum biohorizon. The Brasilia fauna of the cavatum biohorizon consists of specimens with a smaller size, sometimes already showing the ribbing style of Graphoceras. The morphogenus Graphoceras is much more common in the cavatum biohorizon than in the decipiformis biohorizon, where most of the specimens belonging to the morphogenus Graphoceras are also less depressed. Variants of Bredyia diadematoides are abundant in the decipiformis biohorizon and not recorded in the cavatum biohorizon, where Euaptetoceras infernense sensu Buckman is common.
Ammonites of the Formosum Subzone occur in the "Bunte Mergel" and "Tonhorizont E1" of Ringsheim (Upper Rhine Valley) and in the Konglomeratbank/basal part of the Sowerbyi-Oolith near Achdorf (Wutach area). However, these beds are not yet subdivided into biohorizons.
SW England: The decipiens biohorizon (Bradfordensis Zone, Gigantea Subzone) is slightly older than the cavatum biohorizon of SW Germany, because therein occur Graphoceras and large-sized Brasilia (up to 0.4 m in diameter) in roughly equal numbers (Chandler 1997). The herein described cavatum biohorizon can be correlated with the cavatum biohorizon (Concavum Zone) of Dorset (Chandler 1997). 7. Additional macrofauna of the Upper Aalenian in the Zollernalb Besides the ammonites described and discussed above, the macrofauna of the Achdorf Formation is mainly composed of bivalves. Only two species, Gryphaea calceola (Quenstedt, 1843) and Inoperna sowerbyana (dʼOrbigny, 1850) are more abundant, especially the former, which oc-curs in masses, but only in a few beds. Gryphaea calceola ( Fig. 25: 1-4) was first described from the vicinity of Jungingen, which is hence considered the type locality. This small oyster is especially abundant in the name-bearing Calceolabank. The shells are embedded not in live position, but as isolated valves in a chaotic arrangement (Fig. 25: 1). In a few other beds only small-sized specimens occur ( Fig.  25: 3, 4). Probably these small specimens did not reach the maximum size due to less favourable life conditions and thus represent ecophenotypes, very similar to Early and Middle Jurassic species of Gryphaea (e.g., Bayer et al. 1985). Despite their smaller size they undoubtedly belong to the same taxon and should not be confused -as Quenstedt (1843) did -with a superficially similar small oyster, Ostrea calceola Zieten, 1833, described from Upper Aalenian beds in eastern Swabia (Aalen-Wasseralfingen). The identity of the latter was checked by topotypic material in the SMNS collection. Inoperna sowerbyana (dʼOrbigny, 1850) ( Fig. 25: 5) was already mentioned by Quenstedt (1857, as Modiola plicata) from the vicinity of Jungingen. In the studied sections, it is restricted to the Inopernabank, which is why we here name the bed after this bivalve. Ino perna was probably a shallow endobenthic sediment stacker (Fürsich and Werner 1988), very similar in its life-style to Pinna, which is rarely recorded as well (Fig. 25: 6). Isolated calcitic valves of Trigonia alemanica Rollier, 1912 (Fig. 25: 7) occur in the Calceolabank and were probably washed out of the sediment during storm events. This observation corresponds to the chaotic embedding of the above mentioned Gryphaea. Epibenthic bivalves do not occur earlier than in the Lower Bajocian Sowerbyibank. They are represented by fragments of thick-shelled oysters (Actinostreon sp.) and limids (Ctenostreon sp.). Deeper endobenthic taxa such as Pholadomya lirata (Sowerby, 1818) (Fig. 25: 8), Pholadomya fidicula (J. de C. Sowerby, 1826) ( Fig. 25: 9), Goniomya literata (Sowerby, 1819) ( Fig. 25: 10), and Pleuromya cf. uniformis (Sowerby, 1813) ( Fig. 25: 13), always preserved as steinkerns, are rare in the Upper Aalenian claystones.
Byssate bivalves are represented by isolated valves of Mytiloceramus polyplocus (Roemer, 1857), Oxytoma inaequivalvis (Sowerby, 1819) and the pectinids Propeamussium pumilum (Lamarck, 1819), Chlamys textoria (Schlotheim, 1820) and Entolium corneolum (Young & Bird, 1828). Mytiloceramus polyplocus (Fig. 25: 11) is a geographically wide-spread taxon, which was originally reported from the Aalenian of northern Germany. In the studied Aalenian sections of the Zollernalb, all records come from a single bed, the Rostrote Kalkbank (Mühlbächle, Starzel river near Killer), which is otherwise very poor in fossils. Possibly these bivalves lived attached to driftwood or empty ammonite shells and thus had a pseudoplanctic life-style. Propeamussium pumilum ( Fig.  15: 1) is rare in the area, probably because of unfavourable environmental conditions. In contrast, it is extremely common in various sandstones of the coeval Eisensandstein Formation of eastern Swabia. Chlamys textoria and Entolium corneolum are stratigraphically long-ranging and geographically widespread taxa (Johnson 1984). In the studied sections, however, they have been only recorded by a few specimens. Other determinable molluscs comprise a single belemnite rostrum (Fig. 25: 14) and a poorly preserved nautiloid (Cenoceras sp.), both from the Heiligenbach section.
Crinoid remains were noticed in the field in some beds of the Zillhausen Member and in polished sections of the Onkoidbank bed. Among arthropods, in the Upper Aalenian claystones of the Zollernalb occasionally tanaidacean remains occur. Specimens preserved in claystones had been originally misidentified and described as tiny salamanders by F. v. Huene (see Schweigert and Etter 2008). A well-preserved new record comes from a microfossil sample below the Konglomeratbank in the Heiligenbach section and will be described in another context elsewhere.
Finally, a single tooth of Asteracanthus personati (Quenstedt, 1857) Fig. 25: 15) is the only vertebrate remain from our studied sections and outcrops. It was found in a bed of the Zillhausen Member of the Starzel river.

Conclusions
The consideration of small species results in a much higher diversity of the ostracod fauna of the Upper Aalenian in SW Germany than previously known. The Heiligenbach section and the Geisingen clay pit (Franz et al. 2018) yielded a total of 115 species from the Upper Aalenian (including the species 'incertae sedis'), 31 of which were recorded in both sections.
The uppermost Lower Aalenian is well characterized by the presence of Aphelocythere pygmaea, Acrocythere pumila and Metacytheropteron opalinum. Eucytherura foveolata and Cardobairdia tesakovae have also only been found in this part of the section so far. Cytherella apostolescui appears for the first time at the base of the Achdorf Formation. Higher up in the Achdorf Formation, especially from the Gigantea subzone on, several stratigraphically important species appear like Balowella catena, Cytherelloidea lordi, Cytheropterina alacostata, Eucytherura eberti, Kinkelinella levata, Pleurocythere ohmerti, Procytherura multicostata, and Progonocythere scutula.
Among the ostracod assemblages, cytherurids show the most striking development with the first appearance of five species in the Gigantea Subzone and 14 species in the Concavum Zone. During the same period the total number of genera increases from 7 (from 5 families) in the Bradfordensis Zone to 20 (9 families) in the Gigantea Subzone and 29 (13 families) in the Concavum Zone.
The variation within ammonites of the family Graphoceratidae in southwestern Germany reflects the evolution of Graphoceratidae from the geisingensis biohorizon via the decipiformis biohorizon (uppermost Bradfordensis Zone; see Dietze et al. 2014) to the here newly introduced cavatum biohorizon (basal Concavum Zone). The faunas gradually change in the successive biohorizons from the morphogenus Brasilia to the morphogenus Graphoceras, with numerous transitional forms and a gradual shift towards smaller, more involute and slender shells. In each biohorizon, the ammonites of the family Graphoceratidae probably represent a single palaeobiospecies, the variation of which changes through time, whereas each morphospecies may range across several biohorizons. The integrative study of ammonite and ostracod faunas allows an excellent combination of both stratigraphic lines of evidence. This allows significantly improved correlations between sections and areas, where either ammonites or ostracods are absent or very rare.