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Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany
Journal Pre-proof Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany Sven Sachs, Daniel Madzia, Tobias Püttmann, Benjamin P. Kear PII:
S0195-6671(19)30492-6
DOI:
https://doi.org/10.1016/j.cretres.2020.104406
Reference:
YCRES 104406
To appear in:
Cretaceous Research
Received Date: 8 November 2019 Revised Date:
17 January 2020
Accepted Date: 25 January 2020
Please cite this article as: Sachs, S., Madzia, D., Püttmann, T., Kear, B.P., Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany, Cretaceous Research, https://doi.org/10.1016/ j.cretres.2020.104406. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Ltd. All rights reserved.
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Enigmatic plesiosaur vertebral remains from the middle
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Turonian of Germany
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Sven Sachsa, b *, Daniel Madziac, Tobias Püttmannd, Benjamin P. Keare
5 6
a
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Bielefeld, Germany
8
b
9
c
Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602
Im Hof 9, 51766 Engelskirchen, Germany
Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00-818 Warsaw,
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Poland
11
d
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Greiff-Str. 195, 47803 Krefeld, Germany
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e
Geologischer Dienst Nordrhein-Westfalen (Geological Survey of North Rhine-Westphalia), De-
Museum of Evolution, Uppsala University, Norbyvägen 18, SE-752 36 Uppsala, Sweden
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*Corresponding author.
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E-mail addresses: [email protected] (Sven Sachs), [email protected] (Daniel
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Madzia), [email protected] (Tobias Püttmann), [email protected]
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(Benjamin P. Kear)
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ABSTRACT
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The Turonian (93.9–89.8 Ma) was a key transitional interval of plesiosaur evolution, during
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which pliosaurid apex predators (dominant since the Middle Jurassic) rapidly declined, and
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polycotylids correspondingly radiated as middle trophic-level pursuit hunters. Paradoxically,
26
however, the fossil record of Turonian plesiosaurs is globally sparse, especially in continental
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Europe where only a handful of fragmentary specimens have been recovered from localities in
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the Czech Republic, Germany and Poland. Here, we report on a new European Turonian
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plesiosaur occurrence from the Bochum Grünsand Member of the Duisburg Formation in the
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city of Unna, northwestern Germany. These remains comprise a series of eight mid-series
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cervical vertebrae with articulated ribs that can be precisely correlated to the lower middle
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Turonian UC8a–UC8b calcareous nannofossil biozones. The vertebrae display a distinctive
33
character state combination, including transversely broad lozenge-shaped centra that are
34
anteroposteriorly compact, bear amphicoelous articular surfaces, inset lateral sides, and large
35
zygapophyses that are broader than the corresponding centra. Although phylogenetically
36
inconclusive, these features are compatible with coeval polycotylids. The Bochum Grünsand
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Member vertebrae thus augment the currently scant knowledge of Turonian plesiosaurs from
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Europe, and support assertions that the regional assemblage was taxonomically diverse at that
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time.
40
41
Keywords:
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Plesiosauria 2
43
Polycotylidae
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Brachaucheninae
45
Late Cretaceous
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Münsterland Basin
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48
1. Introduction
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The latest mid-Cretaceous (Turonian, up to ~90 Ma) was a timeframe of wholesale
50
ecological restructuring amongst Mesozoic marine reptile communities (e.g., Polcyn et al.,
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2014; Fischer et al., 2016). Plesiosaurs, which had constituted a dominant faunal component
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during the Late Jurassic–Early Cretaceous (Zverkov et al., 2018), underwent marked faunal
53
turnover with the extinction of pliosaurid apex predators during the middle Turonian (Zverkov
54
et al., 2018; Madzia et al., 2019; although Madzia [2016] reported possibly younger
55
occurrences), and the simultaneous diversification of polycotylid middle trophic-level pursuit
56
hunters (Fischer et al., 2018). Unfortunately, both the stratigraphic and geographic distribution
57
of Turonian plesiosaur fossils is incomplete, especially in continental Europe, where the
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currently documented record comprises only a handful of isolated teeth and bones from the
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laterally continuous Bohemian Cretaceous, and Saxonian Cretaceous basins of the Czech
60
Republic (Kear et al., 2014) and Germany (Sachs et al. 2016; Sachs et al. 2017), together with
61
the Anröchte region in the southern Münsterland Basin of Germany (Sachs, 2000), and the
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Opole region of Poland (Sachs et al., 2018). Most of these specimens are non-diagnostic beyond 3
63
deeper clade levels, but had been attributed to the dubious pliosaurid taxon ‘Polyptychodon’
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(Sachs, 2000; Kear et al., 2014; Madzia 2016), as well as indeterminate elasmosaurids (Kear et
65
al., 2014; Sachs et al. 2016; Sachs et al. 2017), and extremely rare polycotylids (Kear et al., 2014;
66
Sachs et al. 2016; Sachs et al. 2017). Here, we supplement the meagre historical accounts of
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European Turonian plesiosaurs with a new occurrence from the Bochum Grünsand Member of
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the Duisburg Formation in northwestern Germany. We identified this specimen (RE
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551.763.320 A0166) during research surveys in the palaeontological collections at the Ruhr
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Museum in Essen, but the fossil was originally found in the now decommissioned Alter Hellweg
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coal mine in the city of Unna some time prior to 1945. RE 551.763.320 A0166 was previously
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figured by Wittler and Roth (2004, p. 90), who identified it as belonging to a plesiosaur of
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around 8–10 m in length. We formally describe and phylogenetically assess the remains herein,
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and suggest possible polycotylid affinities based on a unique combination of vertebral character
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states.
76 77 78
1.1 Institutional abbreviations GDNW: Geologischer Dienst Nordrhein-Westfalen (Geological Survey of North Rhine-
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Westphalia), Krefeld, Germany. RE: Ruhr Museum, Essen, Germany. SMNK: Staatliches
80
Museum für Naturkunde Karlsruhe, Germany.
81 82
2. Geological setting and age
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2.1. Lithostratigraphy
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The disused Alter Hellweg mine workings are located in the current city area of Unna near
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the southern margin of the Münsterland Basin in northwestern Germany (Fig. 1). The strata
86
comprise approximately 100 m of Upper Cretaceous marine deposits that unconformably
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overlie coal-bearing deposits of late Carboniferous age; these crop out as surface exposures ~5
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km further to the south in the Rhenish Massif. The Cretaceous sequences follow a proximal–
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distal transect from the southwest to the northeast (Hiss, 1995; Dölling et al., 2014) that
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reflects an Albian–Cenomanian transgression from the north across the Rhenish Massif. This
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seaway incursion laid down silts and sands, glauconitic marls and limestones that today form
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the Cenomanian Essen Grünsand (or “Essen Greensand”: see Reiss et al., 2019 for a recent
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description) and Baddeckenstedt formations. Peak transgression during the early Turonian is
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evidenced by marls and limestones of the Büren Formation (Hiss, 1995; Wilmsen et al., 2019).
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This in turn is overlain by highly glauconitic sand- and silt-rich marlstones of the middle
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Turonain Bochum Grünsand Member, and finally, the upper Turonian Soest Grünsand Member
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of the Duisburg Formation (Dölling et al., 2018); this interfingers with less glauconitic
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marlstones and limestones of the Oerlinghausen and Salder formations that constitute a distal
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facies equivalent in the northeast (Dölling et al., 2014). The Turonian successions are
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discontinuously followed by alternating marl and limestone beds of the lower Coniacian Erwitte
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Formation. Increased subsidence during the middle Coniacian−Campanian led to the deposition
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of sand-rich marls constituting the Emscher Formation, which reaches a maximum thickness of
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1500 m in the northern Münsterland Basin (Dölling et al. 2014); however, widespread Cenozoic
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erosion has limited exposure of the mid-Santonian−Campanian successions to the northern and
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western-most parts of the basin. 5
106
107 108
2.2. Nannofossil biostratigraphy Dölling et al. (2018) and Püttmann et al. (2018) recently compiled a detailed
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biostratigraphic scheme for the Münsterland Basin using calcareous nannofossils. We adopted
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this framework to determine the lithostratigraphic provenance of RE 551.763.320 A0166, which
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can be correlated with the Upper Cretaceous (UC) biozonation proposed by Burnett (1998), and
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as modified for the upper Turonian by Lees (2008). Three separate sediment samples (A0166-1,
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A0166-2, A0166-3) were extracted from the matrix encasing RE 551.763.320 A0166, and
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screened via five or more transects across smear-slides (see Perch-Nielsen, 1985) viewed under
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an Olympus BH-2 light microscope at 1250x magnification. All of these slides are stored at the
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GDNW.
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Samples A0166-2 and A0166-3 produced inadequate nannofossil remains. However,
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sample A0166-1 yielded upwards of 35 identifiable taxa (Fig. 2), including Quadrum garnteri,
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which marks the base of the lower Turonian UC7 biozone, and Eiffellithus eximius which
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delimits the lower middle Turonian UC8a boundary. A single example of Lucianorhabdus cf.
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quadrifidus (together with E. eximius) could indicate a range extension into the upper middle
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Turonian UC8b, but this specimen was too poorly preserved for definitive identification. The
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absence of any upper Turonian index taxa, such as Lithraphidites septenarius and Broinsonia
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parca expansa (Burnett, 1998; Lees, 2008), in conjunction with recognized abundance of
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glauconite grains, thus suggests a most plausible assignment of RE 551.763.320 A0166 to the
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Bochum Grünsand Member of the Duisburg Formation, which is early middle Turonian in age.
6
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128
3. Systematic palaeontology
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Sauropterygia Owen, 1860
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Plesiosauria de Blainville, 1835
131
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?Polycotylidae indet.
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134 135
3.1. Referred material RE 551.763.320 A0166, a series of eight cervical vertebrae with associated ribs.
136 137 138
3.2. Locality and horizon RE 551.763.320 A0166 was recovered from Upper Cretaceous marine strata, likely
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representing the Bochum Grünsand Member of the Duisburg Formation, which overlies
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Carboniferous coal-producing sequences in the disused Alter Hellweg coal mine in the city of
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Unna, northwestern Germany. We correlate the source stratum with the lower middle Turonian
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UC8a−UC8b biozones (sensu Burnett, 1998).
143
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4. Description
7
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RE 551.763.320 A0166 consists of eight incomplete cervical vertebrae, herein designated
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C1−C8 for descriptive purposes (sequence shown in supplementary figure 1), with the anterior-
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most C1−C5 preserved in articulation but displaced from their original anatomical positions (Fig.
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3A, B). All of the vertebrae are damaged (possibly during excavation) but show little evidence of
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diagenetic distortion. The C1−C5 centra are conspicuously wider than long/high (maximum
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width ~80 mm extrapolated from C5), with amphicoelous articular surfaces that are clearly
151
traceable in lateral cross-section (Fig. 3A). The exposed posterior articular surface of C5 is
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delimited by a raised rim, and has an indented central area that surrounds the notochordal pit
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(Fig. 4A). The complete ventral edge of the articular surface on C5 is also truncated and straight,
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implying an atypically broad, lozenge-shaped outline (Fig. 4A). The intact left lateral side is
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inset, and the neurocentral suture is V-shaped in profile (Fig. 4B). The ventral face of the
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centrum has a low midline ridge that intersects between the large, circular nutrient foramina;
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these are best exposed on the eroded C7 centrum (Fig. 4C).
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The neural canal of C8 is sub-triangular in outline (Fig. 4D), and enclosed by thick pedicles
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that are fully fused to the centrum, and directly abut the anterior articular surface (as seen in
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C6), but are inset relative to the posterior articular surface (Fig. 4E). Both the
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pre/postzygapophyses (variously preserved on C4, C6 and C8) are very large (56/52 mm long in
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C6) and exceed the width of the corresponding centrum (Figs 3B, 4D); they also project far
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beyond the centrum articular surfaces (Fig. 4E). The prezygopophyseal articulations are
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obliquely oriented and concave, whereas the postzygapophyses are oblique but more planar
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(Fig. 4E). The virtually complete neural spine of the isolated neurapophysis adjacent to C6 is 106
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mm high, and has an upright rectangular profile that was clearly greater than the height of the 8
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centrum (Fig. 4E). The anterior edge of the neural spine is sharply tapered, and its apex is
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squared off without any significant expansion.
169
Fused cervical ribs are present on C5 and C7 (Fig. 4A, F); they are situated low on the
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centrum sides and seem to have been backswept (Fig. 4A). The intact right cervical rib on C7 is
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64 mm long with a constricted mid-section and anteroposteriorly expanded distal extremity
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(Fig. 4F). The left rib head on C5 appears to have been dorsoventrally tall compared to its length
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(Fig. 4A, B).
174
175
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5. Phylogenetic placement We used the phylogenetic dataset of Madzia et al. (2019) to infer the affinities of RE
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551.763.320 A0166 (see Supplementary information for matrix and character descriptions). RE
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551.763.320 A0166 was designated as the ‘Unna specimen’, and the following taxon
179
additions/state coding modifications were included: Wintrich et al. (2017) — incorporating the
180
expanded outgroup sample of Neusticosaurus pusillus and Nothosaurus marchicus, with re-
181
scores for Yunguisaurus liae and Pistosaurus, which was treated as a single species-level
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hypodigm; Páramo-Fonseca et al. (2018) — integration of the Cretaceous pliosaurids
183
Sachicasaurus vitae and ‘Kronosaurus’ boyacensis; Fischer et al. (2018) — inclusion of new
184
scores for the polycotylids Thililua longicollis, Eopolycotylus rankini, Manemergus anguirostris,
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Dolichorhynchops tropicensis, Georgiasaurus penzensis, Dolichorhynchops sp. (specimen ROM
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29010), Dolichorhynchops herschelensis, Sulcusuchus erraini, and Mauriciosaurus fernandezi;
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Morgan and O’Keefe (2019) — score amendments to the polycotylids Trinacromerum 9
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bentonianum, Dolichorhynchops osborni, Dolichorhynchops bonneri, Mauriciosaurus fernandezi,
189
and Polycotylus latipinnis. Neusticosaurus pusillus was designated as the outgroup following
190
Wintrich et al. (2017).
191
Our analyses were conducted in TNT 1.5 (Goloboff et al., 2008a; Goloboff and Catalano,
192
2016; version last updated on September 25, 2019) with multistate characters ‘ordered’ (as in
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Madzia et al., 2019) and maxtrees set at 10,000. Neusticosaurus pusillus was designated as the
194
user-defined outgroup in all analyses (sensu Wintrich et al., 2017). An initial ‘new technology’
195
search was conducted with 50 addition sequences and default settings for sectorial searches,
196
ratchet, drift, and tree fusing. A ‘traditional search’ was subsequently performed on trees saved
197
to RAM with tree bisection-reconnection (TBR) branch-swapping. Given the recognized
198
pervasive homoplasy in plesiosaur phylogenies (Fischer et al., 2017; Fischer et al., 2018), we
199
also experimented with implied weighting (Goloboff, 1993, 1995; Goloboff et al., 2008b;
200
Goloboff et al., 2018); this compared results from an initial analysis using prior weights (UWPa)
201
against a succession of implied weights (IW) incrementally increasing K-values from 6 (IWPa6),
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to 9 (IWPa9), and 12 (IWPa12), respectively (see, e.g., Madzia and Cau 2017 for discussion).
203
Bremer support was calculated with TBR and suboptimal trees (up to 10 steps in UWPa and 0.3
204
in IWPa6–12) retained.
205
The ‘new technology’ UWPa search returned 24 most parsimonious trees (MPTs) with a
206
best score of 1793 (CI=0.221; RI=0.686). The subsequent ‘traditional search’ reached maximum
207
memory (10,000 MPTs max memory), and failed to resolve RE 551.763.320 A0166 (Fig. 5).
208
Likewise, the IWPa6 (19 MPTs; best score=121.74361; CI=0.220; RI=0.684), IWPa9 (9 MPTs; best
10
209
score=95.61986; CI=0.220; RI=0.684), and IWPa12 (21 MPTs; best score=78.94531; CI=0.220;
210
RI=0.685) analyses with subsequent ‘traditional search’ again reached maxtrees (10,000 MPTs
211
in all three runs), but placed RE 551.763.320 A0166 within a polytomy containing the
212
rhomaleosaurids Rhomaleosaurus, Borealonectes, Maresaurus, and Meyerasaurus (Fig. 6).
213
Considering that the stratigraphically youngest demonstrable rhomaleosaurid fossils are Middle
214
Jurassic in age (Benson et al., 2015), we interpret our results as most likely indicative of
215
homoplasy and/or missing data. We therefore further inspected consensus cross-sections of
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the various MPTs, which revealed alternative nesting of RE 551.763.320 A0166 amongst either
217
basally branching thalassophonean pliosaurids, or advanced polycotylids, such as
218
Dolichorhynchops.
219
220
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6. Character state comparisons Given the uncertain phylogenetic relationships of RE 551.763.320 A0166, we compared the
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remains with a range of approximately coeval Turonian plesiosaur taxa to infer its possible
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classification. Firstly, RE 551.763.320 A0166 can be readily differentiated from elasmosaurids,
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as typified by the paradigm taxon Libonectes (Sachs and Kear, 2015, 2017), because of its
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anteroposteriorly compact amphicoelous centra. Marked reduction of the cervical centrum
226
lengths also occurs in brachauchenine pliosaurids, such as Brachauchenius (Albright et al.,
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2007a), and is a distinguishing trait amongst some polycotylids, including Trinacromerum
228
(Carpenter 1996; Storrs 1999). However, the transversely broad lozenge-shaped centrum
229
articular surface in C5 of RE 551.763.320 A0166 is reminiscent of elasmosaurids (see Sachs and 11
230
Kear, 2017. p. 212, fig. 4H, I), and contrasts with the more circular articular surfaces otherwise
231
characterising polycotylids, such as Thililua (Fischer et al., 2018) and Dolichorhynchops (Morgan
232
and O’Keefe, 2019).
233
The lateral sides of the centrum in C5 of RE 551.763.320 A0166 are inset, again like those of
234
polycotylids (Morgan and O’Keefe, 2019), but there are no lateral longitudinal ridges as
235
described in Thililua (Fischer et al., 2018), or the classic diagnostic condition of elasmosaurids
236
(Sachs and Kear, 2015; although, this is ontogenetically variable and may be incipient in some
237
atypical taxa: Brown, 1981; Kear, 2002; Sato et al., 2003; Gasparini et al., 2003). In addition, the
238
ventral nutrient foramina in C7 unequivocally distinguish RE 551.763.320 A0166 from
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brachauchenines, such as Brachauchenius (Albright et al., 2007a; Druckenmiller and Russel
240
2008), and potentially also the isolated pliosaurid-like vertebrae associated with
241
‘Polyptychodon’ that lack ventral nutrient foramina (see Kear et al., 2014, p. 190, fig. 3k).
242
The reduced ventral midline keel on C5 potentially positions the RE 551.763.320 A0166
243
vertebral sequence within the mid-cervical series, because the ventral midline keel becomes
244
progressively lower and more rounded throughout the mid-column cervicals of polycotylids
245
(e.g., Dolichorhynchops and Mauricosaurus: Schmeisser McKean 2012; Frey et al., 2017).
246
Similarly, the fused neural arches and cervical ribs suggest that RE 551.763.320 A0166 was an
247
osteologically mature individual (sensu Brown, 1981); however, the distinct ‘V-shaped’
248
neurocentral sutures resemble those of the ‘juvenile’ holotype (SMNK-PAL 3861) of the
249
polycotylid Manemergus (Buchy et al., 2005). Despite this, the oblique zygapophyseal articular
12
250
surfaces (best exemplified in C6 of RE 551.763.320 A0166) contrast with those of Manemergus,
251
which are otherwise horizontally oriented (Buchy et al. 2005).
252
The tall and transversely compressed neural spine on C6 of RE 551.763.320 A0166 is
253
certainly polycotylid-like (Carpenter 1996), but lacks the posterior inclination and curving
254
profile evident in Eopolycotylus (Albright et al., 2007b), Mauricosaurus (Frey et al., 2017) and
255
Thililua (Fischer et al. 2018); C6 also lacks the longitudinal clefts reported on the neural spines
256
of Eopolycotylus and other polycotylids (Albright et al., 2007b; Fischer et al., 2018), together
257
with the transversely expanded dorsal spine apices described in Dolichorhynchops (Sato 2005).
258
Lastly, the cervical rib in C8 closely resembles those of Mauricosaurus, which are constricted
259
along their mid-length (Frey et al., 2017, p. 102, fig. 6).
260
261
7. Conclusions
262
Although fragmentary, RE 551.763.320 A0166 is important because it constitutes a novel
263
addition to the rare record of Turonian plesiosaur fossils from Europe. Moreover, despite being
264
phylogenetically ambiguous, the specimen manifests a unique character state combination that
265
serves to differentiate it amongst coeval plesiosaur taxa: the presence of transversely broad
266
lozenge-shaped centra with amphicoelous articular surfaces, inset lateral sides, and large
267
zygapophyses that are broader than the corresponding centra. Based on these, and other key
268
states — including anteroposteriorly compact centra that lack lateral longitudinal ridges
269
(precluding affinity with elasmosaurids: Sachs and Kear, 2015, 2017), and the presence of
270
expansive ventral nutrient foramina (which differs from brachauchenine pliosaurids that lack 13
271
foramina on the ventral surface of the cervicals: Albright et al., 2007a; Druckenmiller and Russel
272
2008) — we provisionally conclude that RE 551.763.320 A0166 shows closest compatibility with
273
polycotylids. If correct, this assignment is significant because it constitutes the first discovery of
274
polycotylid skeletal remains from the Turonian of continental Europe (previous accounts have
275
otherwise only reported isolated teeth: Kear et al., 2014; Sachs et al. 2016; Sachs et al. 2017).
276
We additionally estimate that RE 551.763.320 A0166 derived from an ‘adult’ plesiosaur of
277
around 4 m maximum snout-tail length (approximated from comparative measurements in
278
Schmeisser McKean, 2012; Schumacher and Martin, 2016), which is a substantial reduction
279
from previous calculations (Wittler and Roth, 2004) but confirms that European Turonian
280
plesiosaur assemblages incorporated both larger-bodied brachauchenine pliosaurids as apex
281
predators, as well as elasmosaurids and smaller-bodied polycotylids, which would have
282
constituted middle trophic-level feeders within the local ecosystem.
283
284
Acknowledgements
285
Achim Reisdorf (Ruhr Museum Essen) and Udo Scheer (formerly Stiftung Ruhr Museum Essen)
286
generously assisted with access to specimens and information. Jörg Mutterlose (Ruhr-
287
Universität Bochum) provided equipment for processing and analysis of nannofossil samples,
288
and Bettina Dölling (GDNW) contributed to our geological interpretations. Finally, our
289
manuscript benefited from constructive comments by Eduardo Koutsoukos (Chief Editor,
290
Cretaceous Research), Rodrigo Otero (Universidad de Chile) and a second anonymous reviewer.
291 14
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the role of organic and inorganic carbon fluxes. Palaeogeography, Palaeoclimatology,
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skeleton and bone histology inform on evolution of a unique body plan. Science Advances
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Wittler, Roth (2004) Dortmund zur Zeit der Saurier. Museum für Naturkunde Dortmund, Dortmund. 95 pp. Zverkov NG, Fischer V, Madzia D, Benson RBJ. 2018. Increased pliosaurid dental disparity across the Jurassic–Cretaceous transition. Palaeontology 61: 825–846.
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Figure captions
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Figure 1. Paleogeographic maps of Turonian marine basins both (A) globally (sensu Scotese,
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2014), and (B) within Europe showing position of the Alter Hellweg mine locality along the
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northern Rhenish Massif (modified from Voigt, 2000; Vejbaek et al., 2010).
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Figure 2. Selected calcareous nannofossils from sample A0166-1. A: Biscutum constans. B:
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Biscutum melaniae. C: Braarudosphaera bigelowii. D-E: Eiffellithus eximius. F: Eprolithus floralis.
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G: Gartnerago segmentatum. H: Helicolithus turonicus. I: Kamptnerius magnificus. J:
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Lucianorhabdus cf. quadrifidus. K-L: Quadrum gartneri. M: Tranolithus orionatus. N:
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Watznaueria barnesiae. O: Zeugrhabdotus bicrescenticus. Scale bar for all specimens = 5 µm.
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Figure 3. Cervical vertebrae of RE 551.763.320 A0166 shown in (A) right, and (B) posterior
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views. Abbreviations: cr - cervical rib, cv - cervical vertebra, df - dorsal foramen, nc - neural
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canal, ns - neural spine, prz - prezygapophysis, poz - postzygapophysis. Scale bar = 50 mm.
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Figure 4. Cervical vertebra C5 of RE 551.763.320 A0166 shown in (A) posterior, and (B) lateral
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views. (C) Weathered internal surface of vertebra C7 exposing the nutrient foramina. (D)
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Vertebra C8 in posterior view with intact postzygapophysis. (E) Neural arch of vertebra C6 in
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lateral view. (F) Cervical rib of vertebra C7 in medial view. Abbreviations: ap - anterior process
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of cervical rib, cr - cervical rib, df - dorsal foramen, nc - neural canal, ncs – neurocentral suture,
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ns - neural spine, prz - prezygapophysis, poz - postzygapophysis, pp - posterior process of
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cervical rib. Scale bars = 20 mm.
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Figure 5. Strict consensus tree produced by the unweighted parsimony analysis (UWPa). Decay
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Index values (Bremer support) are indicated at each node.
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Figure 6. Strict consensus tree produced by analyses with implied weighting (IWPa)
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incrementally increasing K-values from (A) IWPa6, (B) IWPa9, and (C) IWPa12. Decay Index
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values (Bremer support) are indicated at each node.
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Supplementary figure 1. Sequence of cervical vertebrae used in the text for descriptive
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purposes.
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All authors Conceptualization, Methodology, Validation, Formal analysis, Investigation, Resources, Writing Original Draft, Writing, Review & Editing
There are no conflicts of interest
S0195-6671(19)30492-6
DOI:
https://doi.org/10.1016/j.cretres.2020.104406
Reference:
YCRES 104406
To appear in:
Cretaceous Research
Received Date: 8 November 2019 Revised Date:
17 January 2020
Accepted Date: 25 January 2020
Please cite this article as: Sachs, S., Madzia, D., Püttmann, T., Kear, B.P., Enigmatic plesiosaur vertebral remains from the middle Turonian of Germany, Cretaceous Research, https://doi.org/10.1016/ j.cretres.2020.104406. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Ltd. All rights reserved.
1
Enigmatic plesiosaur vertebral remains from the middle
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Turonian of Germany
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Sven Sachsa, b *, Daniel Madziac, Tobias Püttmannd, Benjamin P. Keare
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a
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Bielefeld, Germany
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b
9
c
Naturkunde-Museum Bielefeld, Abteilung Geowissenschaften, Adenauerplatz 2, 33602
Im Hof 9, 51766 Engelskirchen, Germany
Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00-818 Warsaw,
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Poland
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d
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Greiff-Str. 195, 47803 Krefeld, Germany
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e
Geologischer Dienst Nordrhein-Westfalen (Geological Survey of North Rhine-Westphalia), De-
Museum of Evolution, Uppsala University, Norbyvägen 18, SE-752 36 Uppsala, Sweden
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*Corresponding author.
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E-mail addresses: [email protected] (Sven Sachs), [email protected] (Daniel
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Madzia), [email protected] (Tobias Püttmann), [email protected]
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(Benjamin P. Kear)
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1
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ABSTRACT
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The Turonian (93.9–89.8 Ma) was a key transitional interval of plesiosaur evolution, during
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which pliosaurid apex predators (dominant since the Middle Jurassic) rapidly declined, and
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polycotylids correspondingly radiated as middle trophic-level pursuit hunters. Paradoxically,
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however, the fossil record of Turonian plesiosaurs is globally sparse, especially in continental
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Europe where only a handful of fragmentary specimens have been recovered from localities in
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the Czech Republic, Germany and Poland. Here, we report on a new European Turonian
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plesiosaur occurrence from the Bochum Grünsand Member of the Duisburg Formation in the
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city of Unna, northwestern Germany. These remains comprise a series of eight mid-series
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cervical vertebrae with articulated ribs that can be precisely correlated to the lower middle
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Turonian UC8a–UC8b calcareous nannofossil biozones. The vertebrae display a distinctive
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character state combination, including transversely broad lozenge-shaped centra that are
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anteroposteriorly compact, bear amphicoelous articular surfaces, inset lateral sides, and large
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zygapophyses that are broader than the corresponding centra. Although phylogenetically
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inconclusive, these features are compatible with coeval polycotylids. The Bochum Grünsand
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Member vertebrae thus augment the currently scant knowledge of Turonian plesiosaurs from
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Europe, and support assertions that the regional assemblage was taxonomically diverse at that
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time.
40
41
Keywords:
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Plesiosauria 2
43
Polycotylidae
44
Brachaucheninae
45
Late Cretaceous
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Münsterland Basin
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48
1. Introduction
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The latest mid-Cretaceous (Turonian, up to ~90 Ma) was a timeframe of wholesale
50
ecological restructuring amongst Mesozoic marine reptile communities (e.g., Polcyn et al.,
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2014; Fischer et al., 2016). Plesiosaurs, which had constituted a dominant faunal component
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during the Late Jurassic–Early Cretaceous (Zverkov et al., 2018), underwent marked faunal
53
turnover with the extinction of pliosaurid apex predators during the middle Turonian (Zverkov
54
et al., 2018; Madzia et al., 2019; although Madzia [2016] reported possibly younger
55
occurrences), and the simultaneous diversification of polycotylid middle trophic-level pursuit
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hunters (Fischer et al., 2018). Unfortunately, both the stratigraphic and geographic distribution
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of Turonian plesiosaur fossils is incomplete, especially in continental Europe, where the
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currently documented record comprises only a handful of isolated teeth and bones from the
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laterally continuous Bohemian Cretaceous, and Saxonian Cretaceous basins of the Czech
60
Republic (Kear et al., 2014) and Germany (Sachs et al. 2016; Sachs et al. 2017), together with
61
the Anröchte region in the southern Münsterland Basin of Germany (Sachs, 2000), and the
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Opole region of Poland (Sachs et al., 2018). Most of these specimens are non-diagnostic beyond 3
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deeper clade levels, but had been attributed to the dubious pliosaurid taxon ‘Polyptychodon’
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(Sachs, 2000; Kear et al., 2014; Madzia 2016), as well as indeterminate elasmosaurids (Kear et
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al., 2014; Sachs et al. 2016; Sachs et al. 2017), and extremely rare polycotylids (Kear et al., 2014;
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Sachs et al. 2016; Sachs et al. 2017). Here, we supplement the meagre historical accounts of
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European Turonian plesiosaurs with a new occurrence from the Bochum Grünsand Member of
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the Duisburg Formation in northwestern Germany. We identified this specimen (RE
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551.763.320 A0166) during research surveys in the palaeontological collections at the Ruhr
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Museum in Essen, but the fossil was originally found in the now decommissioned Alter Hellweg
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coal mine in the city of Unna some time prior to 1945. RE 551.763.320 A0166 was previously
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figured by Wittler and Roth (2004, p. 90), who identified it as belonging to a plesiosaur of
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around 8–10 m in length. We formally describe and phylogenetically assess the remains herein,
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and suggest possible polycotylid affinities based on a unique combination of vertebral character
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states.
76 77 78
1.1 Institutional abbreviations GDNW: Geologischer Dienst Nordrhein-Westfalen (Geological Survey of North Rhine-
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Westphalia), Krefeld, Germany. RE: Ruhr Museum, Essen, Germany. SMNK: Staatliches
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Museum für Naturkunde Karlsruhe, Germany.
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2. Geological setting and age
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2.1. Lithostratigraphy
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The disused Alter Hellweg mine workings are located in the current city area of Unna near
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the southern margin of the Münsterland Basin in northwestern Germany (Fig. 1). The strata
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comprise approximately 100 m of Upper Cretaceous marine deposits that unconformably
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overlie coal-bearing deposits of late Carboniferous age; these crop out as surface exposures ~5
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km further to the south in the Rhenish Massif. The Cretaceous sequences follow a proximal–
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distal transect from the southwest to the northeast (Hiss, 1995; Dölling et al., 2014) that
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reflects an Albian–Cenomanian transgression from the north across the Rhenish Massif. This
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seaway incursion laid down silts and sands, glauconitic marls and limestones that today form
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the Cenomanian Essen Grünsand (or “Essen Greensand”: see Reiss et al., 2019 for a recent
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description) and Baddeckenstedt formations. Peak transgression during the early Turonian is
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evidenced by marls and limestones of the Büren Formation (Hiss, 1995; Wilmsen et al., 2019).
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This in turn is overlain by highly glauconitic sand- and silt-rich marlstones of the middle
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Turonain Bochum Grünsand Member, and finally, the upper Turonian Soest Grünsand Member
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of the Duisburg Formation (Dölling et al., 2018); this interfingers with less glauconitic
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marlstones and limestones of the Oerlinghausen and Salder formations that constitute a distal
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facies equivalent in the northeast (Dölling et al., 2014). The Turonian successions are
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discontinuously followed by alternating marl and limestone beds of the lower Coniacian Erwitte
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Formation. Increased subsidence during the middle Coniacian−Campanian led to the deposition
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of sand-rich marls constituting the Emscher Formation, which reaches a maximum thickness of
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1500 m in the northern Münsterland Basin (Dölling et al. 2014); however, widespread Cenozoic
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erosion has limited exposure of the mid-Santonian−Campanian successions to the northern and
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western-most parts of the basin. 5
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107 108
2.2. Nannofossil biostratigraphy Dölling et al. (2018) and Püttmann et al. (2018) recently compiled a detailed
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biostratigraphic scheme for the Münsterland Basin using calcareous nannofossils. We adopted
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this framework to determine the lithostratigraphic provenance of RE 551.763.320 A0166, which
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can be correlated with the Upper Cretaceous (UC) biozonation proposed by Burnett (1998), and
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as modified for the upper Turonian by Lees (2008). Three separate sediment samples (A0166-1,
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A0166-2, A0166-3) were extracted from the matrix encasing RE 551.763.320 A0166, and
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screened via five or more transects across smear-slides (see Perch-Nielsen, 1985) viewed under
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an Olympus BH-2 light microscope at 1250x magnification. All of these slides are stored at the
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GDNW.
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Samples A0166-2 and A0166-3 produced inadequate nannofossil remains. However,
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sample A0166-1 yielded upwards of 35 identifiable taxa (Fig. 2), including Quadrum garnteri,
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which marks the base of the lower Turonian UC7 biozone, and Eiffellithus eximius which
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delimits the lower middle Turonian UC8a boundary. A single example of Lucianorhabdus cf.
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quadrifidus (together with E. eximius) could indicate a range extension into the upper middle
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Turonian UC8b, but this specimen was too poorly preserved for definitive identification. The
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absence of any upper Turonian index taxa, such as Lithraphidites septenarius and Broinsonia
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parca expansa (Burnett, 1998; Lees, 2008), in conjunction with recognized abundance of
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glauconite grains, thus suggests a most plausible assignment of RE 551.763.320 A0166 to the
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Bochum Grünsand Member of the Duisburg Formation, which is early middle Turonian in age.
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3. Systematic palaeontology
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Sauropterygia Owen, 1860
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Plesiosauria de Blainville, 1835
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?Polycotylidae indet.
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134 135
3.1. Referred material RE 551.763.320 A0166, a series of eight cervical vertebrae with associated ribs.
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3.2. Locality and horizon RE 551.763.320 A0166 was recovered from Upper Cretaceous marine strata, likely
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representing the Bochum Grünsand Member of the Duisburg Formation, which overlies
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Carboniferous coal-producing sequences in the disused Alter Hellweg coal mine in the city of
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Unna, northwestern Germany. We correlate the source stratum with the lower middle Turonian
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UC8a−UC8b biozones (sensu Burnett, 1998).
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4. Description
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RE 551.763.320 A0166 consists of eight incomplete cervical vertebrae, herein designated
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C1−C8 for descriptive purposes (sequence shown in supplementary figure 1), with the anterior-
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most C1−C5 preserved in articulation but displaced from their original anatomical positions (Fig.
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3A, B). All of the vertebrae are damaged (possibly during excavation) but show little evidence of
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diagenetic distortion. The C1−C5 centra are conspicuously wider than long/high (maximum
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width ~80 mm extrapolated from C5), with amphicoelous articular surfaces that are clearly
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traceable in lateral cross-section (Fig. 3A). The exposed posterior articular surface of C5 is
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delimited by a raised rim, and has an indented central area that surrounds the notochordal pit
153
(Fig. 4A). The complete ventral edge of the articular surface on C5 is also truncated and straight,
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implying an atypically broad, lozenge-shaped outline (Fig. 4A). The intact left lateral side is
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inset, and the neurocentral suture is V-shaped in profile (Fig. 4B). The ventral face of the
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centrum has a low midline ridge that intersects between the large, circular nutrient foramina;
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these are best exposed on the eroded C7 centrum (Fig. 4C).
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The neural canal of C8 is sub-triangular in outline (Fig. 4D), and enclosed by thick pedicles
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that are fully fused to the centrum, and directly abut the anterior articular surface (as seen in
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C6), but are inset relative to the posterior articular surface (Fig. 4E). Both the
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pre/postzygapophyses (variously preserved on C4, C6 and C8) are very large (56/52 mm long in
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C6) and exceed the width of the corresponding centrum (Figs 3B, 4D); they also project far
163
beyond the centrum articular surfaces (Fig. 4E). The prezygopophyseal articulations are
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obliquely oriented and concave, whereas the postzygapophyses are oblique but more planar
165
(Fig. 4E). The virtually complete neural spine of the isolated neurapophysis adjacent to C6 is 106
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mm high, and has an upright rectangular profile that was clearly greater than the height of the 8
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centrum (Fig. 4E). The anterior edge of the neural spine is sharply tapered, and its apex is
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squared off without any significant expansion.
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Fused cervical ribs are present on C5 and C7 (Fig. 4A, F); they are situated low on the
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centrum sides and seem to have been backswept (Fig. 4A). The intact right cervical rib on C7 is
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64 mm long with a constricted mid-section and anteroposteriorly expanded distal extremity
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(Fig. 4F). The left rib head on C5 appears to have been dorsoventrally tall compared to its length
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(Fig. 4A, B).
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175
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5. Phylogenetic placement We used the phylogenetic dataset of Madzia et al. (2019) to infer the affinities of RE
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551.763.320 A0166 (see Supplementary information for matrix and character descriptions). RE
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551.763.320 A0166 was designated as the ‘Unna specimen’, and the following taxon
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additions/state coding modifications were included: Wintrich et al. (2017) — incorporating the
180
expanded outgroup sample of Neusticosaurus pusillus and Nothosaurus marchicus, with re-
181
scores for Yunguisaurus liae and Pistosaurus, which was treated as a single species-level
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hypodigm; Páramo-Fonseca et al. (2018) — integration of the Cretaceous pliosaurids
183
Sachicasaurus vitae and ‘Kronosaurus’ boyacensis; Fischer et al. (2018) — inclusion of new
184
scores for the polycotylids Thililua longicollis, Eopolycotylus rankini, Manemergus anguirostris,
185
Dolichorhynchops tropicensis, Georgiasaurus penzensis, Dolichorhynchops sp. (specimen ROM
186
29010), Dolichorhynchops herschelensis, Sulcusuchus erraini, and Mauriciosaurus fernandezi;
187
Morgan and O’Keefe (2019) — score amendments to the polycotylids Trinacromerum 9
188
bentonianum, Dolichorhynchops osborni, Dolichorhynchops bonneri, Mauriciosaurus fernandezi,
189
and Polycotylus latipinnis. Neusticosaurus pusillus was designated as the outgroup following
190
Wintrich et al. (2017).
191
Our analyses were conducted in TNT 1.5 (Goloboff et al., 2008a; Goloboff and Catalano,
192
2016; version last updated on September 25, 2019) with multistate characters ‘ordered’ (as in
193
Madzia et al., 2019) and maxtrees set at 10,000. Neusticosaurus pusillus was designated as the
194
user-defined outgroup in all analyses (sensu Wintrich et al., 2017). An initial ‘new technology’
195
search was conducted with 50 addition sequences and default settings for sectorial searches,
196
ratchet, drift, and tree fusing. A ‘traditional search’ was subsequently performed on trees saved
197
to RAM with tree bisection-reconnection (TBR) branch-swapping. Given the recognized
198
pervasive homoplasy in plesiosaur phylogenies (Fischer et al., 2017; Fischer et al., 2018), we
199
also experimented with implied weighting (Goloboff, 1993, 1995; Goloboff et al., 2008b;
200
Goloboff et al., 2018); this compared results from an initial analysis using prior weights (UWPa)
201
against a succession of implied weights (IW) incrementally increasing K-values from 6 (IWPa6),
202
to 9 (IWPa9), and 12 (IWPa12), respectively (see, e.g., Madzia and Cau 2017 for discussion).
203
Bremer support was calculated with TBR and suboptimal trees (up to 10 steps in UWPa and 0.3
204
in IWPa6–12) retained.
205
The ‘new technology’ UWPa search returned 24 most parsimonious trees (MPTs) with a
206
best score of 1793 (CI=0.221; RI=0.686). The subsequent ‘traditional search’ reached maximum
207
memory (10,000 MPTs max memory), and failed to resolve RE 551.763.320 A0166 (Fig. 5).
208
Likewise, the IWPa6 (19 MPTs; best score=121.74361; CI=0.220; RI=0.684), IWPa9 (9 MPTs; best
10
209
score=95.61986; CI=0.220; RI=0.684), and IWPa12 (21 MPTs; best score=78.94531; CI=0.220;
210
RI=0.685) analyses with subsequent ‘traditional search’ again reached maxtrees (10,000 MPTs
211
in all three runs), but placed RE 551.763.320 A0166 within a polytomy containing the
212
rhomaleosaurids Rhomaleosaurus, Borealonectes, Maresaurus, and Meyerasaurus (Fig. 6).
213
Considering that the stratigraphically youngest demonstrable rhomaleosaurid fossils are Middle
214
Jurassic in age (Benson et al., 2015), we interpret our results as most likely indicative of
215
homoplasy and/or missing data. We therefore further inspected consensus cross-sections of
216
the various MPTs, which revealed alternative nesting of RE 551.763.320 A0166 amongst either
217
basally branching thalassophonean pliosaurids, or advanced polycotylids, such as
218
Dolichorhynchops.
219
220
221
6. Character state comparisons Given the uncertain phylogenetic relationships of RE 551.763.320 A0166, we compared the
222
remains with a range of approximately coeval Turonian plesiosaur taxa to infer its possible
223
classification. Firstly, RE 551.763.320 A0166 can be readily differentiated from elasmosaurids,
224
as typified by the paradigm taxon Libonectes (Sachs and Kear, 2015, 2017), because of its
225
anteroposteriorly compact amphicoelous centra. Marked reduction of the cervical centrum
226
lengths also occurs in brachauchenine pliosaurids, such as Brachauchenius (Albright et al.,
227
2007a), and is a distinguishing trait amongst some polycotylids, including Trinacromerum
228
(Carpenter 1996; Storrs 1999). However, the transversely broad lozenge-shaped centrum
229
articular surface in C5 of RE 551.763.320 A0166 is reminiscent of elasmosaurids (see Sachs and 11
230
Kear, 2017. p. 212, fig. 4H, I), and contrasts with the more circular articular surfaces otherwise
231
characterising polycotylids, such as Thililua (Fischer et al., 2018) and Dolichorhynchops (Morgan
232
and O’Keefe, 2019).
233
The lateral sides of the centrum in C5 of RE 551.763.320 A0166 are inset, again like those of
234
polycotylids (Morgan and O’Keefe, 2019), but there are no lateral longitudinal ridges as
235
described in Thililua (Fischer et al., 2018), or the classic diagnostic condition of elasmosaurids
236
(Sachs and Kear, 2015; although, this is ontogenetically variable and may be incipient in some
237
atypical taxa: Brown, 1981; Kear, 2002; Sato et al., 2003; Gasparini et al., 2003). In addition, the
238
ventral nutrient foramina in C7 unequivocally distinguish RE 551.763.320 A0166 from
239
brachauchenines, such as Brachauchenius (Albright et al., 2007a; Druckenmiller and Russel
240
2008), and potentially also the isolated pliosaurid-like vertebrae associated with
241
‘Polyptychodon’ that lack ventral nutrient foramina (see Kear et al., 2014, p. 190, fig. 3k).
242
The reduced ventral midline keel on C5 potentially positions the RE 551.763.320 A0166
243
vertebral sequence within the mid-cervical series, because the ventral midline keel becomes
244
progressively lower and more rounded throughout the mid-column cervicals of polycotylids
245
(e.g., Dolichorhynchops and Mauricosaurus: Schmeisser McKean 2012; Frey et al., 2017).
246
Similarly, the fused neural arches and cervical ribs suggest that RE 551.763.320 A0166 was an
247
osteologically mature individual (sensu Brown, 1981); however, the distinct ‘V-shaped’
248
neurocentral sutures resemble those of the ‘juvenile’ holotype (SMNK-PAL 3861) of the
249
polycotylid Manemergus (Buchy et al., 2005). Despite this, the oblique zygapophyseal articular
12
250
surfaces (best exemplified in C6 of RE 551.763.320 A0166) contrast with those of Manemergus,
251
which are otherwise horizontally oriented (Buchy et al. 2005).
252
The tall and transversely compressed neural spine on C6 of RE 551.763.320 A0166 is
253
certainly polycotylid-like (Carpenter 1996), but lacks the posterior inclination and curving
254
profile evident in Eopolycotylus (Albright et al., 2007b), Mauricosaurus (Frey et al., 2017) and
255
Thililua (Fischer et al. 2018); C6 also lacks the longitudinal clefts reported on the neural spines
256
of Eopolycotylus and other polycotylids (Albright et al., 2007b; Fischer et al., 2018), together
257
with the transversely expanded dorsal spine apices described in Dolichorhynchops (Sato 2005).
258
Lastly, the cervical rib in C8 closely resembles those of Mauricosaurus, which are constricted
259
along their mid-length (Frey et al., 2017, p. 102, fig. 6).
260
261
7. Conclusions
262
Although fragmentary, RE 551.763.320 A0166 is important because it constitutes a novel
263
addition to the rare record of Turonian plesiosaur fossils from Europe. Moreover, despite being
264
phylogenetically ambiguous, the specimen manifests a unique character state combination that
265
serves to differentiate it amongst coeval plesiosaur taxa: the presence of transversely broad
266
lozenge-shaped centra with amphicoelous articular surfaces, inset lateral sides, and large
267
zygapophyses that are broader than the corresponding centra. Based on these, and other key
268
states — including anteroposteriorly compact centra that lack lateral longitudinal ridges
269
(precluding affinity with elasmosaurids: Sachs and Kear, 2015, 2017), and the presence of
270
expansive ventral nutrient foramina (which differs from brachauchenine pliosaurids that lack 13
271
foramina on the ventral surface of the cervicals: Albright et al., 2007a; Druckenmiller and Russel
272
2008) — we provisionally conclude that RE 551.763.320 A0166 shows closest compatibility with
273
polycotylids. If correct, this assignment is significant because it constitutes the first discovery of
274
polycotylid skeletal remains from the Turonian of continental Europe (previous accounts have
275
otherwise only reported isolated teeth: Kear et al., 2014; Sachs et al. 2016; Sachs et al. 2017).
276
We additionally estimate that RE 551.763.320 A0166 derived from an ‘adult’ plesiosaur of
277
around 4 m maximum snout-tail length (approximated from comparative measurements in
278
Schmeisser McKean, 2012; Schumacher and Martin, 2016), which is a substantial reduction
279
from previous calculations (Wittler and Roth, 2004) but confirms that European Turonian
280
plesiosaur assemblages incorporated both larger-bodied brachauchenine pliosaurids as apex
281
predators, as well as elasmosaurids and smaller-bodied polycotylids, which would have
282
constituted middle trophic-level feeders within the local ecosystem.
283
284
Acknowledgements
285
Achim Reisdorf (Ruhr Museum Essen) and Udo Scheer (formerly Stiftung Ruhr Museum Essen)
286
generously assisted with access to specimens and information. Jörg Mutterlose (Ruhr-
287
Universität Bochum) provided equipment for processing and analysis of nannofossil samples,
288
and Bettina Dölling (GDNW) contributed to our geological interpretations. Finally, our
289
manuscript benefited from constructive comments by Eduardo Koutsoukos (Chief Editor,
290
Cretaceous Research), Rodrigo Otero (Universidad de Chile) and a second anonymous reviewer.
291 14
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Figure captions
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Figure 1. Paleogeographic maps of Turonian marine basins both (A) globally (sensu Scotese,
433
2014), and (B) within Europe showing position of the Alter Hellweg mine locality along the
434
northern Rhenish Massif (modified from Voigt, 2000; Vejbaek et al., 2010).
435
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Figure 2. Selected calcareous nannofossils from sample A0166-1. A: Biscutum constans. B:
437
Biscutum melaniae. C: Braarudosphaera bigelowii. D-E: Eiffellithus eximius. F: Eprolithus floralis.
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G: Gartnerago segmentatum. H: Helicolithus turonicus. I: Kamptnerius magnificus. J:
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Lucianorhabdus cf. quadrifidus. K-L: Quadrum gartneri. M: Tranolithus orionatus. N:
440
Watznaueria barnesiae. O: Zeugrhabdotus bicrescenticus. Scale bar for all specimens = 5 µm.
441
442
Figure 3. Cervical vertebrae of RE 551.763.320 A0166 shown in (A) right, and (B) posterior
443
views. Abbreviations: cr - cervical rib, cv - cervical vertebra, df - dorsal foramen, nc - neural
444
canal, ns - neural spine, prz - prezygapophysis, poz - postzygapophysis. Scale bar = 50 mm.
22
445
446
Figure 4. Cervical vertebra C5 of RE 551.763.320 A0166 shown in (A) posterior, and (B) lateral
447
views. (C) Weathered internal surface of vertebra C7 exposing the nutrient foramina. (D)
448
Vertebra C8 in posterior view with intact postzygapophysis. (E) Neural arch of vertebra C6 in
449
lateral view. (F) Cervical rib of vertebra C7 in medial view. Abbreviations: ap - anterior process
450
of cervical rib, cr - cervical rib, df - dorsal foramen, nc - neural canal, ncs – neurocentral suture,
451
ns - neural spine, prz - prezygapophysis, poz - postzygapophysis, pp - posterior process of
452
cervical rib. Scale bars = 20 mm.
453
454
Figure 5. Strict consensus tree produced by the unweighted parsimony analysis (UWPa). Decay
455
Index values (Bremer support) are indicated at each node.
456
457
Figure 6. Strict consensus tree produced by analyses with implied weighting (IWPa)
458
incrementally increasing K-values from (A) IWPa6, (B) IWPa9, and (C) IWPa12. Decay Index
459
values (Bremer support) are indicated at each node.
460
461
Supplementary figure 1. Sequence of cervical vertebrae used in the text for descriptive
462
purposes.
463
23
All authors Conceptualization, Methodology, Validation, Formal analysis, Investigation, Resources, Writing Original Draft, Writing, Review & Editing
There are no conflicts of interest