Research Article |
Corresponding author: Werner Schwarzhans ( wwschwarz@aol.com ) Academic editor: Oliver Rauhut
© 2022 Werner Schwarzhans, Helmut Keupp.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Schwarzhans W, Keupp H (2022) Early teleost otolith morphogenesis observed in the Jurassic of Franconia, Bavaria, southern Germany. Zitteliana 96: 51-67. https://doi.org/10.3897/zitteliana.96.81737
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The otoliths described in this study are from the late Pliensbachian of the Buttenheim clay pit near Bamberg, Franconia, northern Bavaria, and represent one of the earliest teleost otolith assemblages known so far. A total of 351 otoliths have been recovered, many of which are well-preserved and of sizes that indicate they originated from adult specimens and can be considered morphologically mature. The assemblage contains seven species, four of them stem teleosts of the genus Leptolepis and three from the enigmatic otolith-based genus Archaeotolithus, which cannot be attributed to a firm systematic position. We describe three species as new: Leptolepis buttenheimensis sp. nov., Leptolepis steberae sp. nov. and Archaeotolithus doppelsteini sp. nov. In addition, we review 49 otoliths from the original material of
Early Jurassic, Middle Jurassic, Leptolepididae, Leptolepis, Archaeotolithus, review
Jurassic otoliths have rarely been studied.
The taxonomic identification of Jurassic otoliths meets certain problems besides a lack of comparability with otoliths of crown teleosts. One of the principal problems is their low level of morphological diversity. Other problems concern uncertainties in the level of inter- and intraspecific variations expected in the otoliths of these early bony fishes. Weiler (
Here we describe a large collection from the Early and Middle Jurassic of Franconia composed from two sources. The first is a collection of 351 otoliths of the latest Pliensbachian from the Buttenheim clay pit. The other contains 86 otoliths from the type-material of
The otoliths described in this study were collected in Upper Franconia, northern Bavaria, Germany, in a clay pit near Buttenheim, southeast of Bamberg. Specimens described by
The section is divided by four thin beds representing short phases of reworking by high water energy resulting from low-stand sea levels that caused winnowing of small grain sizes and enrichment of the reworked concretions (see
The condensed sections between the first three reworking horizons are fossil rich and comprise mass occurrences of ammonites and other fossils. They represent sea level highstands with reduced sedimentation rates and some faunal immigration from the Tethyan Ocean in the south (see
Most of the material described by
A good proportion of Schröder’s type-material was recovered from the collection of the Geological Institute of the University of Erlangen, mostly from Kremmeldorf and Pünzendorf. The type specimens, including holotypes, were recovered from 14 out of 16 species described by Schröder and from otoliths he placed in Otolithus cf. ornatus Weiler, 1953. Not accounted for are the specimens pertaining to Otolithus liasicus and Otolithus kolbi. Most of Schröder’s otoliths are rather small (< 1.5 to 1 mm in length) and, therefore, pose problems for reliable identification, as we discuss in the descriptive section. Other specimens are incomplete, have encrusted surfaces, or are otherwise damaged; thus, we found that only a relatively small fraction of otolith specimens was preserved well enough to serve as type specimens. The registration numbers on the recovered microslides do not match the numbers assigned in Schröder’s publication. However, a comparison of the specimens with his drawings allowed for reliable correlation. In addition, Schröder apparently colored in red the labels of the specimens that are denoted in his work as holotypes. Thus, now only the Jurassic otoliths described by Weiler (
The otolith terminology follows
The Leptolepis-pattern is characterized by a straight sulcus with a widened ostium, which is poorly defined against the cauda, and a vague, undifferentiated, and often poorly discernable colliculum. The rostrum is massive and long while the antirostrum is minute. The ostium opens to the anterior-dorsal rim along the entire stretch of the rostrum, but its colliculum is often separated from the predorsal rim of the otolith by a shallow ridge, which
The Archaeotolithus-pattern differs considerably and is characterized by a triangular otolith shape and an eccentrically positioned, dorsally shifted sulcus with vague margins and unclear distinction into ostium and cauda. The sulcus is often curved anteriorly and posteriorly in a manner that makes measuring difficult. Furthermore, the sulcus is open anteriorly and posteriorly it reaches very close to the posterior tip of the otolith; therefore, measurements of the length of the sulcus do not contain diagnostic value and are omitted. The length of the ostium and cauda (OsL and CaL) can be measured but is not very accurate, so the absolute values should be regarded with some caution. This leaves only OL, OH and OT as reliable measurements in these otoliths.
All otoliths were studied with a reflected-light microscope. Photographs were taken remotely controlled from a computer with a Canon EOS 1000 mounted on the phototube of a Wild M400 photomacroscope, and were captured at regular field-of-depth levels for each view. The individual photographs of each view were stacked using Helicon Soft’s Helicon Focus software. The continuously focused pictures were digitally processed with Adobe Photoshop to enhance contrast, balance exposition, or retouch small inconsistencies, such as sand grains, incrustations, or pigmentation spots, insofar as doing so without altering the otolith morphology was possible.
Types, other photographed specimens, along with a selection of additional specimens, are deposited in the Staatliche Naturwissenschaftliche Sammlungen Bayerns, Bayrische Staatssammlung für Paläontologie und Geologie in München. Schröder’s collection is cataloged under SNSB-BSPG 2022 III 1–62, and the Buttenheim collection is cataloged under SNSB-BSPG 2022 IV 1–18. Other specimens are kept in the private collection of B. Doppelstein, Berlin, B.Steber, Leibersdorf and in the collection of the senior author.
Remarks. The description of fossil otolith-based taxa principally represents a parataxonomy with taxa established by articulated skeletons. The risks of parataxonomy actually occurring varies greatly in the fossil record. For instance it is low for many young Cenozoic strata, for regions such as New Zealand where there is an abundance of otolith data but very few articulated skeletons, and for certain systematic groups such as the Ophidiiformes where fossil otolith data significantly prevail over skeletal material. In the case of Jurassic teleosts, however, there is a considerable wealth of skeletal data and relatively limited data of otoliths. The cause for this discrepancy may be the adverse effects of diagenesis over a long period of geological time for aragonitic fossils such as otoliths.
One aspect hampering the identifications of Jurassic otoliths is the fact that only a single case exists in which otoliths of fishes where were found in situ, namely in Leptolepis normandica (see
The following section complements the review of Jurassic to early Cretaceous otoliths by
Subclass Actinopterygii sensu Goodrich, 1930
Division Teleostei Müller, 1885
Order Leptolepidiformes s.l. Nicholson & Lydekker, 1889
Family Leptolepididae s.l. Nicholson & Lydekker, 1889
1956 Otolithus cf. ornatus Weiler, 1953 - Schröder: pl. 6, figs 1–3.
1956 Otolithus opalini - Schröder: pl. 6, fig. 9 (non figs 7–8).
1956 Otolithus cristatus - Schröder: pl. 6, figs 13–14.
1956 Otolithus vastus - Schröder: pl. 7, figs 36–38.
1956 Otolithus (Lycopteridarum?) brevis - Weiler: pl. 3, figs 16–19.
1965 Otolithus (Lycoperidarum?) brevirostris - Weiler: pl. 3, figs 20–23.
?1965 Otolithus (Lycopteridarum?) elegans - Weiler: pl. 3, figs 24, 25, pl. 4, fig. 26.
1965 Otolithus (Lycopteridarum?) similis - Weiler: pl. 2, figs 10–13, pl. 3, figs 14–15.
1997 Leptolepis normandica Nybelin, 1962 - Delsate: figs 1–5, pl. 1, fig. 4, pl. 2, figs 5–9 (otoliths in situ).
2013 Leptolepis normandica Nybelin, 1962 - Nolf: pl. 6.
2014 Otolithus (Lycopteroidarum?) similis Weiler, 1965 - Hesse: fig. 18A–G.
2014 Otolithus (Lycopteroidarum?) brevis Weiler, 1965 - Hesse: fig. 19A–F.
2014 Otolithus (Lycopteroidarum?) ornatus Weiler, 1953 - Hesse: fig. 20A–D.
2014 Otolithus (inc. sed.) sp. 1 - Hesse: fig. 21A–C.
?2014 Otolithus (inc. sed.) sp. 2 - Hesse: fig. 22A–B.
2014 Otolithus (inc.sed.) sp. 3 - Hesse: fig. 23A.
2014 Otolithus (inc. sed.) sp. 5 - Hesse: fig. 25A.
?2014 Leptolepis sp. - Hesse: fig. 32 (otolith in situ).
2018 Leptolepis normandica Nybelin, 1962 - Schwarzhans: fig. 1C–H.
2021b Leptolepis normandica Nybelin, 1962 – Keupp: fig. 9.3 B.
264 specimens: 251 specimens from the late Pliensbachian of Buttenheim: 8 specimens Apyrenum subzone (figured specimen SNSB-BSPG 2022 IV 1, Plate
Otoliths of Leptolepis normandica are more compressed than other coeval species of Leptolepis with an OL:OH ratio of 1.25–1.45 (vs. >.1.5), but less compressed than that of L. steberae sp. nov. (1.1–1.25). The rostrum is shorter than that of L. buttenheimensis sp. nov. ranging from about 30 to 36% of OL (vs. 37–45%), but longer that those of L. steberae sp. nov. (12–25%). The short postdorsal rim is higher than that of L. curvisulcatus and L. kremmeldorfensis and longer than that of L. kremmeldorfensis. The ostium tends to be wider in L. normandica than in coeval Leptolepis species except of L. steberae sp. nov. (OsH:CaH = 1.5–2.2 vs 1.25–1.6).
Leptolepis normandica
is the most common otolith-based species so far recognized in the Early Jurassic and the early Middle Jurassic (Pliensbachian to Aalenian). Its distinction from coeval species is not always easy to determine, particularly regarding L. curvisulcatus, and transitional forms exist. The type specimens of the synonymized species of Weiler (
Otoliths of Leptolepis normandica and L. curvisulcatus. figs 1–15: Leptolepis normandica Nybelin, 1962; 1–11: From late Pliensbachian of Buttenheim, 1–8, 11: EPH horizon (SNSB-BSPG 2022 IV 3); 9: “Quellhorizon” (SNSB-BSPG 2022 IV 2); 10: Apyrenum subzone (SNSB-BSPG 2022 IV 1); 12: paratype of Ot. cristatus Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 5); 13: paratype of Ot. opalini Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 20); 14: paratype of Ot. vastus Schröder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 34); 15: holotype of Ot. vastus from Peulendorf (SNSB-BSPG 2022 III 30). figs 15–19 Leptolepis curvisulcatus (Schröder, 1956); 15: paratype of Ot. opalini Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 17); 16: holotype of Ot. curvisulcatus Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 42); 17: holotype of Ot. schattenbergi Schröder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 2); 18: paratype of Ot. schattenbergi Schröder, 1956 from Kremmelsdorf (SNSB-BSPG 2022 III 47); 19: holotype of Ot. opalini Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 16).
1956 Otolithus curvisulcatus - Schröder: pl. 7, figs 25–27.
1956 Otolithus opalini - Schröder: pl. 6, figs 7–8 (non fig. 9).
1956 Otolithus schattenbergi - Schröder: pl. 6, figs 10–12.
2018 Leptolepis ornatus (Weiler, 1953) - Schwarzhans: fig. 1I–J, ?K.
15 specimens from Schröder’s collection from the late Toarcian to early Aalenian: holotype of Ot. curvisulcatus from Kremmeldorf (SNSB-BSPG 2022 III 42, Plate
Leptolepis curvisulcatus is slightly more elongate than L. normandica with an OL:OH ratio of 1.4–1.6 (vs. 1.25–1.45), which is mainly caused by a relatively low postdorsal rim, which is also more rounded. Other proportions and characteristics are shared with L. normandica. Leptolepis curvisulcatus also differs from L. normandica in its longer ostium as compared to the length of its cauda, but because of the gradual transition from ostium to cauda, this feature cannot be measured unequivocally. The rounded and short postdorsal rim distinguishes L. curvisulcatus from the coeval L. kremmeldorfensis.
The distinctions among the three nominal late Toarcian to Aalenian species L. normandica, L. curvisulcatus, and L. kremmeldorfensis are all very subtle and it is possible that with more material becoming available from this time interval their nature and validity may have to be revised again. This is also because most specimens so far known from L. curvisulcatus and L. kremmeldorfensis are smaller than 1.5 mm in length and, therefore, cannot be considered morphologically mature.
The best-preserved and largest specimen that we attribute to L. curvisulcatus is a paratype of Schröder’s Otolithus opalini of 2.55 mm in length (Plate
2021b Leptolepis ornatus (Weiler, 1953) – Keupp: fig. 9.3 A,C.
Named after the type-locality Buttenheim near Bamberg, Franconia.
SNSB-BSPG 2022 IV 4 (Plate
11 specimens: 10 specimens same data as holotype (SNSB-BSPG 2022 IV 5, Plate
48 specimens: same location as holotype, 45 specimens from the EPH horizon, 3 specimens from the Apyrenum subzone.
OL:OH = 1.55–1.75; OH:OT = 4.0–5.0. Rostrum length 37–45% of OL. Ventral rim of ostium shallow and fading, and ostium relatively narrow; OsH:CaH = 1.25–1.6.
Slender, thin otoliths up to 3.25 mm in length (holotype 2.65 mm). Ventral rim relatively shallow, regularly curved, deepest at or behind middle, and smooth to irregularly undulating. Rostrum very long, nearly half of otolith length. Dorsal rim behind ostial opening short, moderately elevated, broad and irregularly undulating. Posterior rim broadly rounded.
Inner face very slightly bent with distinctly supramedian sulcus. Ostium long, not expanding backward from rostrum and antirostral notch, about as long as cauda but separation poorly defined. Ventral margin of ostium indistinct, gradual, and shallow, resulting in relatively narrow ostium. Cauda very slightly flexed, terminating close to posterior tip of otolith. Dorsal depression very small, restricted to position above anterior part of cauda. No ventral furrow. Outer face flat to slightly concave with particularly thin and delicate rostrum, smooth dorsally and few indistinct furrows ventrally. Shallow umbo positioned near dorsal rim opposite to dorsal field of inner face.
Leptolepis buttenheimensis
is readily recognized by its elongated shape, extremely long rostrum, and very thin and delicate structure. However, a few morphologically transitional specimens exist with L. normandica in specimens smaller than about 2.2 mm in length, which are not considered to be fully morphologically developed. Another distinctive feature is the shallow and fading lower margin of the ostium as seen in figures 1a, 2, 3a, 4a, 5 and 7a on Plate
Leptolepis buttenheimensis is known only from the upper Pliensbachian of the type locality where it represents the second most common species.
Otoliths of Leptolepis buttenheimensis and L. steberae. figs 1–7 Leptolepis buttenheimensis sp. nov. from the late Pliensbachian of Buttenheim; 1: holotype SNSB-BSPG 2022 IV 4, EPH horizon; 2–7: paratypes SNSB-BSPG 2022 IV 5–6; 2–5, 7: EPH horizon; 6: Apyrenum subzone. figs 8–12: Leptolepis steberae sp. nov. from the Pliensbachian of Buttenheim, EPH horizon; 8: holotype SNSB-BSPG 2022 IV 13; 9–12: paratypes SNSB-BSPG 2022 IV 14.
Named after Birgit Steber (Leibersdorf), who has intensely collected from the Buttenheim clay pit and provided specimens of this species which were instrumental for its recognition.
SNSB-BSPG 2022 IV 13 (Plate
9 specimens same data as holotype (SNSB-BSPG 2022 IV 14, Plate
OL:OH = 1.1–1.25. Rostrum short, its length 12–25% of OL. Ventral and dorsal rims regularly curving. Ventral rim of ostium shallow, often fading, no or very weak distinction of ostium and cauda.
Nearly round, thin otoliths up to 2.5 mm in length (holotype 2.2 mm); OH:OT = 3.5–4.5. Ventral rim deeply and regularly curved, and smooth or intensely and finely crenulated. Rostrum short, blunt. Dorsal rim behind ostial relatively long, elevated, rounded, broad and irregularly undulating. Posterior rim broadly rounded.
Inner face distinctly bent with slightly supramedian sulcus. Ostium short, indistinctly separated from cauda, slightly expanding backward from rostrum and antirostral notch, about as long as cauda. Ventral margin of sulcus often indistinct, gradual, relatively straight with no or very feeble indication of differentiation into ostium and cauda. Cauda straight, terminating close to posterior tip of otolith. Dorsal depression very small, restricted to position above anterior part of cauda. No ventral furrow. Outer face flat to slightly concave, with many short radial furrows particularly along ventral margin of otolith. No or very feeble postcentral umbo.
Leptolepis steberae is a relatively rare and small species in the late Pliensbachian of Buttenheim. It is recognized by its compressed, rounded outline with only a moderately projecting and rather blunt rostrum. Its OL:OH ratio is less than in contemporaneous congeners (1.1–1.25 vs. 1.25–175). The rostrum is shorter than in coeval Leptolepis species (12–25% of OL vs. 30–45%). Another typical characteristic is the nearly straight ventral margin of the sulcus, which is also often rather gradational.
1956 Otolithus kremmeldorfensis - Schröder: pl. 7, figs 34–35.
1956 Otolithus amygdalinus - Schröder: pl. 6, figs 4–6.
?1956 Otolithus bambergensis - Schröder: pl. 6, fig. 19, pl. 7, fig. 20.
?1956 Otolithus franconicus - Schröder: pl. 7, figs 31–33.
11 specimens from Schröder’s collection from the late Toarcian to early Aalenian: holotype of Ot. kremmeldorfensis from Kremmeldorf (SNSB-BSPG 2022 III 35, Plate
2 poorly preserved specimens from the late Pliensbachian of Buttenheim (SNSB-BSPG 2022 IV 15, Plate
Leptolepis kremmeldorfensis shares its otolith and sulcus proportions with the coeval L. curvisulcatus and differs in its flat, low, and relatively long postdorsal rim. However, small specimens below 1 mm in length, which have been described as Ot. bambergensis and Ot. franconcius, mostly show a more rounded postdorsal rim similar to the status in L. normandica. Therefore, they are only tentatively attributed and could in fact represent juveniles of any other Leptolepis species.
As with L. curvisulcatus, the validity of L. kremmeldorfensis should be regarded as provisional until larger otoliths have become available from the region and stratigraphic interval. Although a single larger otolith of nearly 3 mm in length, designated as Ot. amygdalinus by
Otoliths of Leptolepis kremmeldorfensis, L. inaequalis, L. macrocephalus, and Leptoelops rhenanus. figs 1–6: Leptolepis kremmeldorfensis (Schröder, 1956); 1: holotype of Ot. kremmeldorfensis Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 35); 2: paratype of Ot. kremmeldorfensis Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 36); 3: holotype of Ot. amygdalinus Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 14); 4: paratype of Ot. bambergensis Schröder, 1956 from Freiahorn (SNSB-BSPG 2022 III 10); 5: holotype of Ot. franconicus Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 24); 6: paratype of Ot. franconicus Schröder, 1956 from Kremmeldorf (SNSB-BSPG 2022 III 27). figs 7, 8: Leptolepis cf. kremmeldorfensis (Schröder, 1956), from the late Pliensbachian of Buttenheim, SNSB-BSPG 2022 IV 15. figs 9–11: Leptolepis inaequalis (Weiler, 1954); 9: holotype of Ot. puenzendorfensis Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 39); 10: holotype of Ot. calloviensis Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 8); 11: holotype of Ot. inaequalis Weiler, 1954 from the Callovian to Oxfordian of Kandern, Baden-Würtemberg (SMF P.3067). figs 12–13: Leptolepis macrocephalus (Schröder, 1956); 12: holotype of Ot. guttaeformis Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 6); 13: holotype of Ot. macrocephalus Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 1). figs 14–16: Leptoelops rhenanus (Weiler, 1954); 14: holotype of Ot. rhenanus Weiler, 1954 from the Callovian of well Bruchsal D 205 (core from 482 to 487 m) near Weingarten, Baden-Württemberg (SMF P.2953); 15: holotype of Ot. rectisulcatus Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 37); 16: holotype of Ot. scissus Schröder, 1956 from Pünzendorf (SNSB-BSPG 2022 III 40).
1954 Otolithus (inc.sed.) inaequalis - Weiler: pl. 4, fig. 170.
1956 Otolithus calloviensis - Schröder: pl. 6, figs 17–18.
1956 Otolithus pünzendorfensis - Schröder: pl. 7, fig. 39.
2018 Leptolepis inaequalis (Weiler, 1954) - Schwarzhans: fig. 2E.
4 specimens: Weiler’s holotype of Ot. inaequalis from the Callovian to Oxfordian of Kandern, Baden-Würtemberg (SMF P.3067, refigured in Plate
Leptolepis inaequalis is characterized by being very thin with nearly flat inner and outer faces. It shares these features only with L. macrocephalus (see below), from which it differs in its slightly slenderer shape (OL:OH = 1.5 vs. 1.35–1.4) and its shallow and rather long postdorsal rim (vs. rounded and expanded).
Due to the fragile nature of these thin and delicate otoliths, only one complete specimen of L. inaequalis is known: the holotype from Weiler. All three specimens from Schröder, which we synonymized with L. inaequalis, are incomplete because they lack the rostrum, but they do show the typical flat inner face in combination with the shallow and long postdorsal rim. Schröder’s drawing of the holotype of Ot. calloviensis indicates a complete specimen, but the one found in his collection is slightly damaged, which possibly happened after the drawing was made.
1956 Otolithus macrocephali - Schröder: pl. 7, fig. 40.
1956 Otolithus guttaeformis - Schröder: pl. 6, figs 15–16.
3 specimens from Schröder’s collection from the early Callovian of Pünzendorf: holotype of Ot. macrocephalus (emended spelling, SNSB-BSPG 2022 III 1, Plate
Leptolepis macrocephalus differs from the coeval L. inaequalis in its more compressed shape, which is exhibited by a deeper ventral rim and a more expanded postdorsal rim and is expressed in the OL:OH ratio of 1.35–1.4 (vs. 1.5). It shares with L. inaequalis completely flat inner and outer faces, features that distinguish both species from all other known Leptolepis otoliths.
Leptolepis macrocephalus and L. inaequalis form a small group of otoliths with a special trait of having flat inner and outer faces. They occur during the Callovian and possibly the early Oxfordian. Their attribution to the genus is therefore less certain than that of Leptolepis otoliths from the Early Jurassic (see above).
Family indet.
1954 Otolithus (Lycopteridarum?) rhenanus - Weiler: pl. 1, fig. 18.
1956 Otolithus rectisulcatus - Schröder: pl. 6, fig. 21.
?1956 Otolithus scissus - Schröder: pl. 7, figs 29–30.
2018 Leptoelops rhenanus (Weiler, 1954) - Schwarzhans: fig. 5O.
5 specimens: Weiler’s holotype of Ot. rhenanus from the Callovian of well Bruchsal D 205 (core from 482 to 487 m) near Weingarten, Baden-Würtemberg (SMF P.2953, refigured in Plate
(from
Leptoelops rhenanus is a very characteristic otolith that differs readily from Leptolepis otoliths in both its very slender shape and its absence of a ventrally widened ostium. Schröder’s holotype of Ot. rectisulcatus lacks the rostrum, but otherwise it largely resembles Weiler’s holotype of L. rhenanus. The specimens of Ot. scissus are also fragmentary, less well-preserved, and much smaller in size. They differ somewhat in the posteriorly elevated dorsal rim and a slight bend in the cauda. We consider these features aspects of an ontogenetical allometry, but we are aware that they could also indicate the presence of another species in the Callovian. We have therefore only tentatively attributed Ot. scissus to L. rhenanus, subject to finding additional and better-preserved specimens in the future.
Family indet.
Designated here as Archaeotolithus trigonalis Stolley, 1912.
Otoliths with a triangular shape that can reach about 7 mm in length. The three corners are the preventral, postventral and middorsal angles. Inner face convex; outer face flat, often with fine radial furrows starting from the middorsal angle. Otolith nucleus distinctly eccentric, visible on the outer face at the middorsal angle. Inner face with distinctly supramedian sulcus with often vague margins, particularly its ventral margin. Ostium and cauda intergrading and poorly distinguished. Ostium open anteriorly, its ventral margin deeply expanding downward. Cauda narrower, slightly downward-oriented toward posterior, and terminating close to posterior tip of otolith. No dorsal depression or ventral furrow.
Three species are referred here to Archaeotolithus: A. bornholmiensis (Malling & Grønwall, 1909) from the Pliensbachian of the isle of Bornholm, Denmark, and Franconia; A. doppelsteini sp. nov. from the late Pliensbachian of Franconia; and A. trigonalis Stolley, 1912 from the late Pliensbachian of Franconia and the Bajocian of northern Germany.
The relationships of Archaeotolithus are obscure. We are not entirely certain whether it represents a sagittal otolith, although this appears likely because of the presence of a sulcus on what is perceived as the inner face of the otoliths, or a lapillus. In any case its peculiar and highly characteristic morphology does not relate to that of any known teleost.
Three kinds of vaguely similar otoliths have also been reported from the Late Jurassic freshwater sediments of eastern Australia (
1909 Otolithus bornholmiensis - Malling & Grønwall: pl. 11, figs 14–16.
1912 Arcaeotolithus bornholmiensis (Malling & Grønwall, 1909) - Stolley: pl. 7, figs 4–5.
?2014 archaeotoliths group 1 - Hesse: fig. 28A–B.
1 specimen from the late Pliensbachian, Hawkerense subzone, of Buttenheim (SNSB-BSPG 2022 IV 7, Plate
Archaeotolithus bornholmiensis is the only species in the genus with almost no indication of a sulcus and further differs from its congeners in the more strongly convex inner face. It is thus also the one most resembling the characteristics of a lapillus.
Otoliths of Archaeotolithus. fig. 1: Achaeotolithus bornholmiensis (Malling & Grønwall, 1909), from the late Pliensbachian of Buttenheim, holotype SNSB-BSPG 2022 IV 7, EPH horizon. figs 2–4: Archaeotolithus doppelsteini sp. nov., from the late Pliensbachian of Buttenheim, EPH horizon; 2: holotype SNSB-BSPG 2022 IV 8; 3–4: paratypes SNSB-BSPG 2022 IV 9. figs 5–7: Archaeotolithus trigonalis Stolley, 1912, from the late Pliensbachian of Buttenheim, EPH horizon, figured specimens SNSB-BSPG 2022 IV 12.
2021b Lapillus unbekannter Zuordnung – Keupp: fig. 9.3 D.
Named after Bernd Doppelstein (Berlin), who has intensely collected from the Buttenheim clay pit and provided the largest specimen of this species.
SNSB-BSPG 2022 IV 8 (Plate
4 specimens same data as holotype (SNSB-BSPG 2022 IV 9, Plate
OL:OH = 0.9–0.93; OH:OT = 2.8–3.6. Ventral rim deeply curved, middorsal angle with small process. Outer face with complex pattern of subvertical furrows.
Very high-bodied otoliths up to 3.25 mm in length (holotype 2.2 mm) with rounded ventral rim and rounded postventral angle. Middorsal angle with small projection. Anterior and posterior rims smooth, ventral rim regularly and coarsely crenulated.
Inner face moderately convex with distinct supramedian positioned sulcus. Dorsal margin of sulcus relatively well-defined, ventral margin gradational and indistinct. Sulcus anteriorly open and ventrally widened, posteriorly curved slightly downward and terminating close to rounded postventral angle. Distinction in ostium and cauda indistinct or with broad shallow ventral bend at junction; OsL:CaL notably variable, ranging from 0.7 to 1.2. Outer face flat, with set of opposing subvertical furrows on pre- and postventral fields, diminishing in intensity with size.
The relatively small holotype is well preserved whereas the large figured paratype (Plate
1912 Archaeotolithus trigonalis - Stolley: pl. 7, figs 1–3.
2014 archaeotoliths group 2 - Hesse: fig. 29A–E.
2018 Archaeotolithus trigonalis Stolley, 1912 - Schwarzhans: fig. 8K.
25 specimens from the late Pliensbachian of Buttenheim: 2 specimens Apyrenum subzone (SNSB-BSPG 2022 IV 10), 1 specimen “Quellhorizon” (SNSB-BSPG 2022 IV 11), 22 specimens Hawkerense subzone (figured specimens SNSB-BSPG 2022 IV 12, Plate
Otoliths with nearly equilateral triangular shape similar to A. bornholmiensis but distinctly less high-bodied than A. doppelsteini. Archaeotolithus trigonalis differs from A. bornholmiensis in being thinner, having a smooth outer face with exposed growth rings (vs with fine radial furrows starting from the middorsal angle), and showing a clear sulcus. It differs from A. doppelsteini not only in the otolith proportions and shape but also in the very short and strongly ventrally extended ostium and the rather straight, inclined cauda.
Archaeotolithus trigonalis is the most common species of the genus in Buttenheim. It almost always shows some kind of incrustation on the inner face, which often obliterates the sulcus morphology. However, in some instances, such as the figured specimens, it can still be reliably identified. A similar incrustation is also seen on the large paratype of A. doppelsteini, which could have been caused by organic material that was attached to it during the early process of fossilization and mineralization.
The earliest teleost otoliths are known from the late Sinemurian (
The stratigraphic ranges and speciation levels vary considerably among the three morphotypes. Xenoleptolepis is known from two species: X. withersi from the Sinemurian and early Pliensbachian (Fig.
The situation is somewhat different for the Leptolepis morphotype. Initially, it occurs more or less in parallel with the two other morphotypes. During the early Jurassic it also shows limited diversity (Fig.
Unfortunately, we do not know how the beginning disparity during the Bathonian matches with the early separation of clades seen in the skeletal record (
Another question is whether the observed explosive burst of diversity associated with some degree of increase in disparity in the Bathonian otoliths represents a real evolutionary signal or is the result of a Lagerstätten effect.
The question is when the evolutionary event took place. Otolith data from the Toarcian, Aalenian and Bajocian are sparse. The largest otolith assemblage studied in this interval is probably the one from the latest Toarcian to early Aalenian that was originally available to Schröder and amounted to 55 specimens. Most of the specimens are relatively small and poorly preserved; nevertheless, they seem to represent only three teleost species. Therefore, it seems that the burst of diversity happened between the early Aalenian and the late Bathonian, over a time interval of about 7 mya. This observation would also indicate that the Bathonian speciation level actually represents a window into early teleost evolution from an otolith perspective. Conversely, the teleost otolith associations of the Pliensbachian and Toarcian are characterized by few common and long ranging species as would typically be expected during an early evolutionary phase. Combined, the now known otolith record from the early and middle Jurassic represents a first view into the early teleost otolith morphogenesis.
Paleogeographic map of Europe at 175 Ma based on
Stratigraphic chart depicting ranges of Early to Middle Jurassic otolith-based fish species. Red bars reflect ranges of localities from which otoliths have been studied for this article. The red asterisk indicates the stratigraphic position of the fishes with otoliths in situ described by
The knowledge of Mesozoic otoliths has steadily increased in recent years and the data of older works have been reviewed (
The key to a better understanding of Jurassic otoliths is the calibration of their morphology through finds of otoliths in situ, particularly as more otolith assemblages emerge and a denser stratigraphic and wider morphological spectrum becomes available. Unfortunately, only otoliths of Leptolepis and Cavenderichthys have so far been found in situ of any Jurassic fishes. We would therefore hope that our colleagues will be mindful of prospects for finding otoliths in situ so that more of the enigmatic otolith morphologies can in the future be tied to the skeleton-based record.
We are indebted to the private collectors Johann Schobert, Hirschaid, Bernd Doppelstein, Berlin, and Birgit Steber, Leibersdorf, for providing their material of otoliths from Buttenheim, and to Christian Schulbert and Axel Munnecke for providing the original material of Gert