Research Article |
Corresponding author: Ulrich Kotthoff ( ulrich.kotthoff@uni-hamburg.de ) Academic editor: Martin Husemann
© 2018 Jason A. Dunlop, Ulrich Kotthoff, Jörg U. Hammel, Jennifer Ahrens, Danilo Harms.
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:
Dunlop JA, Kotthoff U, Hammel JU, Ahrens J, Harms D (2018) Arachnids in Bitterfeld amber: A unique fauna of fossils from the heart of Europe or simply old friends? Evolutionary Systematics 2: 31-44. https://doi.org/10.3897/evolsyst.2.22581
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Bitterfeld amber, sometimes referred to as Saxon or Saxonian amber, is a potentially significant but poorly known source of arthropod data for the Palaeogene of northern Europe. An important aspect is a long-standing controversy about the age of this amber: namely whether it is equivalent to, and perhaps merely a southerly extension of, the better-known Baltic amber, or whether it is a unique and geological younger deposit sampling a different fauna. Here, we briefly review the Bitterfeld arachnids with particular emphasis on how these data could be used to elucidate the age of this deposit. Five arachnid orders have been recorded from Bitterfeld amber: spiders (Araneae), acariform mites (Acariformes), parasitiform mites (Parasitiformes), harvestmen (Opiliones) and pseudoscorpions (Pseudoscorpiones). This is a lower diversity than Baltic amber, where scorpions (Scorpiones) and camel spiders (Solifugae) have also been recorded. Spiders are the most comprehensively studied group, with more than 75 described species. Other groups such as pseudoscorpions and mites appear to be very diverse, but are virtually undescribed. Morphological overlap is apparent in the arachnid fauna and 40 species are currently shared between Baltic and Bitterfeld amber whilst 50 species are unique to the Bitterfeld deposit. At the family level overlap is even higher, but in all groups Baltic amber appears more diverse than Bitterfeld. This overlap may be interpreted as evidence for temporal conspecifity of the Baltic and Bitterfeld ambers, albeit with the Bitterfeld and Baltic ambers possibly representing independent localities within a larger Eocene European amber area which also included the Rovno amber from the Ukraine. However, caution should be exercised because the taxonomic foundation for such assumptions is far from comprehensive, most of the material remains to be studied in detail using modern techniques of morphological reconstruction. There are further issues with date estimates because some arachnid groups show extraordinary morphological stasis over time, even at species level, which may bias the analyses available. Here, we review the available knowledge on Bitterfeld arachnids and discuss how a detailed assessment of this fauna, and other arthropod taxa, could be generated. Several natural history museums – including Hamburg and Berlin – as well as private collectors host major assemblages of Bitterfeld fossils which may help to clarify the debate about the age and provenance of the material, and the extent to which (morpho)-species were maintained both over geographical distances and potentially geological time.
Arachnida Fossil Palaeogene Sachsen-Anhalt Faunal comparison
Bitterfeld amber originates from near the town of the same name in the eastern state of Sachsen-Anhalt in Germany. It is sometimes referred to as Saxon or Saxonian amber. For general overviews see, e.g.,
Alternative hypothesis stressed the uniqueness of the Bitterfeld deposit, dating its inclusions to a younger Oligocene or even Miocene age. Geochemical data now clearly indicate that Bitterfeld and Baltic amber are not identical (e.g.
History. Early reports of ‘Saxon’ amber were reviewed by
Most of the current Bitterfeld amber material (see also Geological Setting) originates from a former open-cast ‘Braunkohle’ mine at Goitsche near Bitterfeld; a historical overview of which can be found in
During this time, it also became apparent that, like Baltic amber, Bitterfeld amber also contained animal and plant inclusions. Many specimens were transferred from Ribnitz-Damgarten to the Museum für Naturkunde Berlin (W. Mey, pers. comm.), and further co-operations with the Geiseltal Museum in Halle and the Museum of the Earth in Warsaw were undertaken (
Geological setting and dating controversy. “Bitterfeld amber” originates from Lagerstätten in Eastern Germany, of which the Goitzsche Lagerstätte is the most important (see above). Stratigraphically, the horizons comprising amber pieces are of Upper Oligocene Age (Chattian, 23.0–28.1 Ma;
Paleogeographic map of Europe during the early to middle Eocene. Yellow areas indicate the position of the present-day amber Lagerstätten at Bitterfeld, Gdansk and Rovno. Modified after
While both Baltic and Bitterfeld amber consist of succinite, their chemical signatures differ (Vávra 2008).
In general, the age of any given amber is notoriously difficult to determine because the amber pieces themselves cannot be dated, only the sediments in which they are found. The option to use sporomorphs, particularly pollen, to biostratigraphically date amber pieces is hampered since they cannot easily be extracted from amber, which may explain that there are not yet many related studies for both Baltic and Bitterfeld amber. The question remains: Has older amber become reworked into younger strata? This is a particular problem at Bitterfeld, such that as mentioned above, three alternative ages can be gleaned from the contemporary literature: namely Eocene (e.g.
The earliest works on the inclusions (e.g.
Summary of the forty species of arachnid described from both Bitterfeld and Baltic amber. Sequence of families largely follows the most recent phylogenetic hypotheses.
Taxon | Source reference |
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OPILIONES | |
CADDIDAE | |
1. Caddo dentipalpus (C. L. Koch & Berendt, 1854) |
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PHALANGIIDAE | |
2. Dicranopalpus ramiger (C. L. Koch & Berendt, 1854) |
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3. Lacinius bizleyi Mitov, Dunlop & Penney, 2015 |
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SCLEROSOMATIDAE | |
4. Leiobunum longipes Menge in Koch & Berendt, 1854 |
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NEMASTOMATIDAE | |
5. ?Histricostoma tuberculatum (C. L. Koch & Berendt, 1854) |
|
PSEUDOSCORPIONES | |
CHEIRIDIIDAE | |
6. Cheiridium hartmanni (Menge in Koch & Berendt, 1854) | Judson in |
ACARIFORMES | |
SMARIDIDAE | |
7. Fessonia grabenhorsti Barthel et al., 2015 |
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8. Fessonia wunderlichi |
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ARANEAE | |
DIPLURIDAE | |
9. Clostes priscus Menge, 1869 |
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TELEMIDAE | |
10. ?Telema moritzi Wunderlich, 2004b |
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SEGESTRIIDAE | |
11. Vetsegestria quinquespinosa Wunderlich, 2004b |
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OONOPIDAE | |
12. Orchestina (Baltorchestina) brevis Wunderlich, 2008a |
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CYATHOLIPIDAE | |
13. Balticolipus kruemmeri Wunderlich, 2004j |
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14. Succinilipus abditus Wunderlich, 2004j |
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SYNOTAXIDAE | |
15. Acrometa cristata Petrunkevitch, 1942 |
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16. Succinitaxus brevis Wunderlich, 2004k |
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THERIDIIDAE | |
17. Balticoridion dubium Wunderlich, 2008b |
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18. Episinus balticus Marusik & Penney, 2004 |
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19. Euryopis bitterfeldensis Wunderlich, 2008b |
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20. Euryopis streyi Wunderlich, 2008b |
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21. Hirsutipalpus varipes Wunderlich, 2008b |
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22. Kochiuridion scutatum Wunderlich, 2008b |
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23. Lasaeola infulata (C. L. Koch & Berendt, 1854) |
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24. Spinitharinus bulbosus Wunderlich, 2008b |
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25. Spinitharinus cheliceratus Wunderlich, 2008b |
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26. Succinobertus adjacens Wunderlich, 2008b |
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27. Ulesanis ovalis Wunderlich, 2008b |
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28. Ulesanis parva Wunderlich, 2008b |
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29. Unispinatoda aculeata Wunderlich, 2008b |
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ANAPIDAE (see notes on Comaromidae in text) | |
30. Balticoroma ernstorum Wunderlich, 2004h |
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31. Balticoroma gracilipes |
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32. Balticoroma serafinorum Wunderlich, 2004h |
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33. Flagellanapis voigti Wunderlich, 2004h |
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34. Saxonanapis grabenhorsti Wunderlich, 2004h |
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MYSMENIDAE | |
35. Eomysmenopsis spinipes Wunderlich, 2004h |
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36. Mysmena groehni Wunderlich, 2004h |
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ZOROPSIDAE | |
37. Succiniropsis kutscheri Wunderlich, 2004o |
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HAHNIIDAE | |
38. Cymbiohahnia parens Wunderlich, 2004n |
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DICTYNIDAE | |
39. Balticocryphoeca curvitarsis Wunderlich, 2004n |
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LIOCRANIDAE | |
40. Apostenus bigibber Wunderlich, 2004q |
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As pointed out by
Raw data on arachnid species numbers were drawn from the summary lists by
Several previous studies have imaged Baltic amber inclusions using computer tomography (µ-CT), including
Arachnid fossils in Bitterfeld amber are actually not so rare and five of the nine orders that occur naturally in Europe today have been recorded: spiders (Araneae), acariform mites (Acariformes), parasitiform mites (Parasitiformes), pseudoscorpions (Pseudoscorpiones), and harvestmen (Opiliones) (Fig.
Examples of arachnids preserved in Bitterfeld amber. A) harvestman Siro platypedibus (Museum für Naturkunde Berlin Coll, No. MB.A. 1086); B) ?Lacinius erinaceus (Museum für Naturkunde Berlin Coll. No. MB.A. 1661); C) undescribed mite species (CeNak Coll. No. BIBS00265); D) a second undescribed mite species (CeNak Coll. No. BIBS00244); E) undescribed pseudoscorpion in the family Chthoniidae (Grabenhorst Coll. No. PS-6); F) first record of the family Pseudogarypidae in Bitterfeld amber (Grabenhorst Coll. No. PS-17); G) undescribed crab spider in the family Thomisidae (CeNak Coll. No.BIBS0433); H) a second undescribed crab spider in the family Thomisidae (CeNak Coll. No. BIBS0481).
Harvestmen. The harvestmen fauna in Bitterfeld amber was described by
In detail (see also Table
The fifty arachnid species so far restricted only to Bitterfeld amber. † indicates an extinct family; sequence of families phylogenetic as above.
Taxon | Source reference |
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OPILIONES | |
SIRONIDAE | |
1. Siro platypedibus Dunlop & Giribet, 2003 |
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PHALANGIIDAE | |
2. Amilenus deltshevi Dunlop & Mitov, 2009 |
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NEMASTOMATIDAE | |
3. ?Mitostoma gruberi Dunlop & Mitov, 2009 |
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ARANEAE | |
PHOLCIDAE | |
4. Paraspermophora bitterfeldensis Wunderlich, 2004b |
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SEGESTRIIDAE | |
5. Ariadna defuncta Wunderlich, 2004b |
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LEPTONETIDAE | |
6. Eoleptoneta curvata Wunderlich, 2004b |
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7. Eoleptoneta kutscheri Wunderlich, 1991 |
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OONOPIDAE | |
8. Orchestina (Baltorchestina) angulata Wunderlich, 2012 | Wunderlich (2011, |
9. Orchestina (Baltorchestina) bitterfeldensis Wunderlich, 2008a |
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10. ?Stenoonops rugosus Wunderlich, 2004b |
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ARCHAEIDAE | |
11. ?Archaea bitterfeldensis Wunderlich, 2004c |
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12. Saxonarchaea dentata Wunderlich, 2004c |
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13. Saxonarchaea diabolica Wunderlich, 2004c |
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SPATIATORIDAE † | |
14. Spatiator bitterfeldensis Wunderlich, 2017 |
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ULOBORIDAE | |
15. Hyptiomopes bitterfeldensis Wunderlich, 2004d |
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CYATHOLIPIDAE | |
16. Spinilipus bispinosus Wunderlich, 2004f |
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17. Spinilipus curvatus Wunderlich, 2004f |
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18. Succinilipus aspinosus Wunderlich, 2004f |
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19. Succinilipus saxoniensis Wunderlich, 1993 |
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20. Succinilipus similis Wunderlich, 2004f |
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SYNOTAXIDAE | |
21. Chelicerinus abnormis Wunderlich, 2008a |
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22. Cornuanandrus bifurcatus Wunderlich, 2004k |
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23. Cornuanandrus bitterfeldensis Wunderlich, 2004k |
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24. Eosynotaxus bitterfeldensis Wunderlich, 2004k |
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NESTICIDAE | |
25. Eopopino rudloffi Wunderlich, 2004l |
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THERIDIIDAE | |
26. Lasaeola bitterfeldensis Wunderlich, 2008b |
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27. ?Lasaeola sigillata Wunderlich, 2008b |
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THERIDIOSOMATIDAE | |
28. Eotheridiosoma tuber Wunderlich, 2004g |
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29. Eotheridiosoma volutum Wunderlich, 2004g |
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30. Spinitheridiosoma bispinosum Wunderlich, 2004g |
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ANAPIDAE | |
31. Balticonopsis bitterfeldensis Wunderlich, 2004h |
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32. Balticonopsis ludwigi Wunderlich, 2017 |
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PROTHERIDIIDAE † | |
33. Protheridion bitterfeldensis Wunderlich, 2004i |
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LINYPHIIDAE | |
34. Custodela acutula Wunderlich, 2004m |
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35. Custodela bispina Wunderlich, 2004m |
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36. Custodela bispinosa Wunderlich, 2004m |
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37. Custodela curvata Wunderlich, 2004m |
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38. Custodela femurspinosa Wunderlich, 2004m |
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39. ?Custodela parva Wunderlich, 2004m |
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40. Custodela stridulans Wunderlich, 2004m |
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41. Custodelela hamata Wunderlich, 2004m |
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42. Paralabulla bitterfeldensis Wunderlich, 2004m |
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TETRAGNATHIDAE | |
43. Anameta distenda Wunderlich, 2004e |
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ARANEIDAE | |
44. Eonephila bitterfeldensis Wunderlich, 2004f |
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45. Eustaloides bitterfeldensis (Wunderlich, 2004e) |
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DICTYNIDAE | |
46. Eocryphoeca bitterfeldensis Wunderlich, 2004n |
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47. Mastigusa bitterfeldensis Wunderlich, 2004n |
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48. Mastigusa magnibulbus Wunderlich, 2004n |
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EPHALMATORIDAE † | |
49. Ephalmator bitterfeldensis Wunderlich, 2004o |
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SALTICIDAE | |
50. Almolinus bitterfeldensis Wunderlich, 2004r |
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Pseudoscorpions. Pseudoscorpions in Bitterfeld amber are likely to represent a diverse fauna which, to date, remains largely undocumented. The fossil history of pseudoscorpions was recently reviewed by
We note that no pseudoscorpion species have yet been formally described from Bitterfeld amber and it is not known whether the samples in various collections represent new species, species that are already known from Baltic and/or Rovno amber, or a mix of both. A shared Baltic/Bitterfeld pseudoscorpion (Pseudoscorpiones) Cheiridium hartmanni (Cheiridiidae) was listed by
Examples of behavioral traits preserved in Bitterfeld amber: A) complete spider exuvia of an unidentified species (CeNak Coll. No. BIBS0514); and B) evidence of a lithobiomorph centipede preying on a pseudoscorpion (Grabenhorst Coll. No. My-1).
The Bitterfeld amber pseudoscorpions shown in Figs
Mites. The mite fauna preserved in Bitterfeld amber appears diverse, both at the generic and species level, and for both of the mite groups that are currently suggested by molecular analyses (Parasitiformes and Acariformes). Two species of smaridid mites in the parasitengonid genus Fessonia have been described (Table
Spiders. As noted above, the vast majority of the fossil arachnids in Bitterfeld amber are spiders (e.g. Fig.
Some of the described spiders are of considerable biogeographical interest such as the pelican spiders (Archaeidae) (
In detail, thirty-two spider species have been described from both Baltic and Bitterfeld amber. Among the mygalomorph spiders there is one common species in the genus Clostes (Dipluridae). For Synspermiata there is one shared species in Telema (Telemidae), one in Vetsegestria (Segestriidae) and one Orchestina (Onopidae). Among entelegyne spiders, there is one common Balticolipus and one Succinilipus (both Cyatholipidae), one Acrometa and one Succinitaxus (both Synotaxidae). There is one Balticoridion, one Episinus, two Euryopis, one Hirsutipalpus, one Kochiuridion, one Lasaeola, two Spinitharinus, one Succinobertus, two Ulesanis, and one Unispinatoda (all Theridiidae). There is one shared Flagellanapis and one Saxonanapis, three Balticoroma (all Anapidae; although Wunderlich recognised a family Comaromidae including Balticoroma), and one Eomysmenopsis and one Mysmena (both Mysmenidae). In the derived ‘RTA clade’ group there is one Succiniropsis (Zoropsidae), one Cymbiohahnia (Hahniidae), one Balticocryphoeca (Dictynidae), and one Apostenus (Liocranidae).
By contrast the forty-seven unique endemic spiders taxa (Table
In the last comprehensive survey of the faunal overlap between the two ambers,
Since Weitschat’s publication, other authors have commented on the insect fauna in particular to argue that the two ambers contain the same fauna. For example,
Unfortunately, there are no comprehensive published summaries of the number of endemic Bitterfeld insect species for comparison, but in contrast to the similarities observed by some authors,
Geographical distinctness. The most comprehensive study assessing geochemical data was presented by
The arachnid data from Bitterfeld amber certainly supports the insect data as Bitterfeld amber appears to have a lower arthropod diversity compared to Baltic amber, although both deposits may still be more diverse than the still rather poorly-known Rovno amber (
Yet before drawing too many conclusions, we need to keep several points in mind. First, Baltic amber has been collected and surveyed for more than 200 years and the sheer volume of amber and specimens available is much greater than the inclusions recovered from Bitterfeld. This inevitable collecting bias means that a richer Baltic amber fauna might be expected anyway, and also means that we must bear in mind that perhaps not all potential shared (or endemic) taxa for the Bitterfeld amber have been recorded. Second, at least half of the described Baltic/Bitterfeld amber spider species originated from a single author, Jörg Wunderlich, who often defined taxa based on minor differences. Thus, we suspect that the species diversity of at least the spiders may have been over-estimated, which would probably increase the relative percentages of both the shared and endemic species, but revisions of the described material are required to test this. Third, while shared taxa may be consistent with the hypothesis that we are sampling a common fauna, we lack independent data for whether (morpho)species can remain stable for millions of years and also to what extent they were geographically widespread during the Paleogene. Finally, we note that Bitterfeld amber has been considered by many workers as ‘just another’ deposit of Baltic amber and only relatively recently has its distinct nature been recognised. This means that many specimens (and potentially species) that actually come from Bitterfeld amber are currently mislabelled or misplaced in collections as Baltic amber taxa and need to be retrieved for further study.
New material. Significant collections of Bitterfeld arachnids (and other arthropods) are present in several museums in Germany and additional material is present in private collections which has never been studied in greater depth and, to a large degree, is unknown and undocumented. The spider fauna is moderately well documented, but needs to be reanalysed as noted above. Many additional specimens are also awaiting study, e.g. in the collections of the Berlin and Hamburg Museums of Natural History. The harvestmen fauna is well studied but many more fossils have become available since the last comprehensive review (
Future work. The identification of both fossil and living arachnids often relies on minute characters which can be hard to discern in amber fossils, such as chaetotaxy, trichobothria composition or the fine structure of male spider’s pedipalps. In general, the better the descriptions the more useful the data for comparative studies will be. Over the past couple of decades image stacking has improved the quality of photographs of amber inclusions, but the real breakthrough has been the application of tomography. We demonstrate here, using the example of two pseudoscorpions (Figure
This manuscript was reviewed externally by two reviewers. All authors declare that there is no conflict of interest.
We thank Manfred Barthel and Wolfram Mey (both Berlin) for discussions of the history of work at this site and Gerhard Schmiedl and Marc Theodor (both Hamburg) for animating discussion. We also thank Carsten Gröhn (Hamburg) and Heiner Grabenhorst (Wienhausen) for supplying Baltic and Bitterfeld amber fossils for scientific study, and Nadine Dupérrè (Hamburg) for assistance with curating this material. Thanks to our student assistents for supporting the synchrotron-based microtomography. The Deutsche Forschungsgemeinschaft funded the digitization of the amber collection at the University of Hamburg (Project KO3944/4-1). Jörg Wunderlich and an anonymous reviewer provided helpful comments on an earlier version of the typescript.