Research Article |
Corresponding author: Franz-Josef Scharfenberg ( mowoscha@gmail.com ) Corresponding author: Helmut Keupp ( keupp@zedat.fu-berlin.de ) Academic editor: Alexander Nützel
© 2022 Franz-Josef Scharfenberg, Helmut Keupp, Johann Schobert.
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:
Scharfenberg F-J, Keupp H, Schobert J (2022) A possible terrestrial egg cluster in driftwood from the Lower Jurassic (Late Pliensbachian) of Buttenheim (Franconia, Germany). Zitteliana 96: 135-143. https://doi.org/10.3897/zitteliana.96.84493
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Our paper shows several clusters of circular fossil egg capsules from the Franconian Amaltheenton Facies (Lower Jurassic, Upper Pliensbachian), mostly found in the clay pit south of Buttenheim. The egg capsules are scatteredly and irregularly arranged on various substrates like calcareous nodules, mollusk shells, or sunken driftwoods. Marine gastropods have been presumed as their producers spawning their eggs autochthonous. Only one specimen exhibits a regular honeycomb-like pattern of small pyritized eggs deposited seemingly within driftwood but originally lead in a small deadwood break. We interpret it as representing a possible allochthonous insect spawn drifted off from the about 70 km removed coastal region.
Liassic, egg capsules, gastropods, insects
In the fossil record, non-vertebrate eggs have been described in all ages (for review, see
Beside the below mentioned findings in the clay pit south of Buttenheim, fossil record of gastropod egg capsules is “extremely poor due to their low fossilization potential” (
Analysis of fossil evidence for insect oviposition has shown that “almost all fossil structures on plants, which have been identified as oviposition, are of the endophytic mode” (
In our paper, we summarize previous findings of autochthonous non-vertebrate eggs in the clay pit south of Buttenheim (Lower Jurassic, Germany), describe new egg findings, and discuss their relevance for the fossil record of non-vertebrate eggs.
Lower Jurassic strata occur in northern Bavaria along the mountainside of the Franconian Alb. The clay pit of the LIAPOR Company Altendorf south of Buttenheim (49°47'34"N, 11°02'30"E) lies about 8 km south-eastwards of Bamberg and crop out both, the Lower Jurassic Amaltheenton Formation (Upper Pliensbachian) and the Posidonia Shale (Lower and Middle Toarcian) (Fig.
The second report is given by
The third report presented two additional findings (
Autochthonous clusters of probable gastropod spawns with pyritized egg capsules, each of about 1 mm in diameter, found in the Late Pliensbachian claystones (Amaltheenton Facies) of Buttenheim. A, B: Attached on the surface of a carbonatic concretion of the EPH (from
First, a pyritized 88 mm long piece of driftwood shows a spawn of about 16 scatteredly arranged circular egg capsules of about 0.9 mm diameter. The three-dimensional preserved pyritized eggs are partly shrunk, partly hemispherical with smooth surfaces (Fig.
Second, one of us (J. S.) found an additional hitherto unpublished specimen from the Amaltheenton facies from Buttenheim. A cluster of pyritized egg capsules attached to the inside of a small, 3 mm long pectinid bivalve fragment has been identified among the sieve residues of micropaleontological samples of the EPH (Fig.
Third, one of us (F.-J. S.) identified adhesive rings of scatteredly arranged egg capsules inside a Pleuroceras body chamber from the Late Pliensbachian Amaltheenton facies (Fig.
We conclude that the dimensions of presumed gastropod egg capsules found in Late Pliensbachian marine sediments differ between 0.35 and 1.5 mm. Their shape is primarily hemispherical with or without a visible central pore. They are always arranged scatteredly, touch each other only occasionally, and do not exhibit any regular geometrical patterns.
Hitherto unpublished presumed gastropod spawn (red arrow) from the Late Pliensbachian of the clay pit south of Buttenheim (leg. J. Schobert, SNSB-BSPG 2011 XI 1334) fixed on the surface of 88 mm long driftwood piece (left). Right: Irregular cluster of pyritized, circular, and scatteredly arranged egg capsules of about 0.9 mm diameter.
In 2008, one of us (F.-J.S.) found a non-bed-by-bed collected piece of a fossil driftwood in the Amaltheenton facies of the LIAPOR Company’s claypit south of Buttenheim. The about 80 × 30 mm large wood fragment is preserved partly as black glittering jet coal, partly pyritized exhibiting excellent cellular structures (Fig.
Basal surface of the honeycomb-like arranged pyritized egg capsules cluster enclosed in driftwood from Late Pliensbachian of Buttenheim (SNSB-BSPG 2022 I 1). A: Complete crescent-sized cluster. The original wood basis changed due to fossilization processes into jet coal (on the picture above left). B: On the egg bases, the fine wood fibers of the original basement are preserved by bioimmuration and, therefore, visible. C: The molds of broken-out egg capsules exhibit their smooth surfaces with a small central pore. Scale bars 500 µm.
The new finding differs from the hitherto described presumed gastropod spawns from Late Pliensbachian strata of Buttenheim and other localities for three reasons (
Deposition of egg capsules on the driftwood could have happened on land, during marine drifting or after they sank on the ground. Besides of gastropod eggs, only few reports exist about fossile egg clusters of other marine non-vertebrate animals. Etches et al. (
The oviposition within a small deadwood break by marine gastropods would be very unusual because all hitherto known egg clusters have been laid on open surfaces (e.g., mollusk shells) and larger cavities respectively (e.g., ammonite body chambers).
On the other hand, regular patterns of epiphytic oviposition are well known and widely distributed among fossil and modern insects, particularly roaches and many butterflies. Roaches (Blattodea) are one of the oldest insect orders known since the Carboniferous, while the radiation of Lepidoptera started during the Late Triassic (
The producer of the regular honeycomb-like pattern of egg capsules found within a Pliensbachian piece of driftwood from Buttenheim (Figs
The specimens figured on Fig.
We would like to thank Bernd Doppelstein, Berlin, for providing the specimens figured on Fig.