Revision of the disparid Stylocrinus (Crinoidea) from the Devonian of Europe, Asia and Australia

Authors


Abstract

Abstract:  The discovery of new specimens and the restudy of known collections result in revision of the diagnosis and the stratigraphic distribution of the disparid crinoid genus Stylocrinus, from the Middle and Upper Devonian of Europe, Asia and Australia. The consistent development of three basal plates, the atomous arms with internally inclined edges adjoining laterally with adjacent brachials in an interlocking network and an apparently rudimentary pinnulation is recognised. The high ecophenotypic plasticity of the common species S. tabulatus negates the validity of several former subspecies and demonstrates the general morphologic variability of the aboral cup proportions. This contrasts with the low morphological spectrum of rarer stylocrinid species. With exclusion of ‘S. elimatus’ (Silurian) from Stylocrinus, the genus is limited to the Devonian. A neotype is proposed for the lost holotype of S. tabulatus. Stylocrinus prescheri sp. nov. is described from the Eifelian to Givetian of Europe and Asia. The first evidence of the gastropod grazing trace fossil Radulichnus on a crinoid aboral cup (S. tabulatus), the post-mortem incurred ossicular-boring of radial and basal plates as well as the post-mortem encrusting by a rugose coral are further observations on Stylocrinus aboral cups.

T he Devonian crinoid genus StylocrinusSandberger and Sandberger, 1856, is characterised by relatively simple crown construction with eight plates within the monocyclic aboral cup (three basals and five radials) followed by five atomous arms. Isolated aboral cups have been reported from Europe (e.g. Goldfuss 1839; Sandberger and Sandberger 1849–1856; Müllerin Zeiler and Wirtgen 1855; Schultze 1866), Asia (Reed 1908; Dubatolova 1971) and Australia (Jell and Jell 1999). Schultze (1866) and Sandberger and Sandberger (1849–1856) also described partly preserved crowns from Germany, where the genus is most abundant within the Eifelian and Givetian deposits of the Rhenish Massif (Eifel and Lahn-Dill vicinity). The Eifel Synclines contain the most famous localities of this low diversity but highly variable crinoid genus.

Since the nineteenth century, stylocrinids have been assigned to several genera, including Platycrinites (Goldfuss 1839), Hexacrinus (Reed 1908), Symbathocrinus (Müllerin Zeiler and Wirtgen 1855) or Scytalocrinus (Wachsmuth and Springer 1886). But the simple construction of the aboral cup, defined by Goldfuss (1839, p. 345) and Sandberger and Sandberger (1856, pp. 399–400), allows an unquestioned identification, with the exception of the arms, which were incorrectly described as ‘additional, elongated radials’ by Sandberger and Sandberger. Following the revised diagnosis given herein, three species are recognised, S. tabulatus (Goldfuss, 1839), S. granulatusHauser, 1997, and S. prescheri sp. nov., based on differences in the skeletal features and plate sculpturing.

Stylocrinus tabulatus has high ecophenotypic plasticity expressed as morphological variability of the aboral cup. The length and width proportions of c. 1500 aboral cups have been analysed and interpreted. As a result, S. tabulatus altus and S. t. depressus both (Müllerin Zeiler and Wirtgen, 1855) are rejected. Therefore, the subspecies S. tabulatus tabulatus is redundant.

Rare crowns (Text-figs 1, 2A–C, E–F) and several isolated brachials (Text-fig. 3A–N) represent an extraordinary construction of the atomous stylocrinid arms. They have internally inclined edges adjoining laterally with adjacent brachials in an interlocking network and an apparently rudimentary pinnulation (Text-fig. 3C, E), arising from irregularly arranged lateral notches, which are diagonally positioned to each other. This construction potentially affords feeding without totally opening the arms in an unprotected position.

Figure TEXT‐FIG. 1..

Stylocrinus tabulatus (Goldfuss, 1839), well-preserved crown, no. GIK-2275 (leg. Fiscus), atomous arms showing internally inclined edges meeting laterally with adjacent brachials in an interlocking network. The specimen is embedded in a thin layer of a clay-rich mudstone that is dominated by diverse fenestrate bryozoans; ×2.9.

Figure TEXT‐FIG. 2..

 A–F. Stylocrinus tabulatus (Goldfuss, 1839), lateral views. A, GIK-2001 (leg. Leunissen), juvenile crown, part of stem preserved; ×6.2. B–C, GIK-2003 (leg. Prescher), partly preserved crown, atomous arms showing internally inclined edges meeting laterally with adjacent brachials; ×4.3. D, GIK-2004 (leg. Schreuer), aboral cup with preserved proximal arms; ×4.5. E–F, MWNH-306a, original of Sandberger and Sandberger (1856, pl. 35, fig. 12a), figured as Stylocrinus scaber, Goldf. sp., partly preserved, juvenile crown, atomous arms showing internally inclined edges meeting laterally with adjacent brachials in an interlocking network; ×6.8.

Figure TEXT‐FIG. 3..

 A–N. Stylocrinus tabulatus (Goldfuss, 1839), isolated brachials. A, GIK-2018, lateral view; ×8.2. B, GIK-2019, interior view showing inordinately distributed lateral notches (possibly for rudimentary pinnulation?), which are diagonally positioned to each other; ×9.4. C–D, GIK-2020, interior and facet view, lateral notches and possibly one preserved rudimentary pinnule(?) (upper right); ×7.4/7.7. E, GIK-2012, interior view with well preserved lateral notches and one rudimentary pinnule(?) (right centre); ×7.8. F, GIK-2021, lateral view; ×7.6. G, GIK-2013, lateral view of a plate with well-developed lateral notches; ×8.0. H, GIK-2014, interior view of proximal brachials with well-developed lateral notches; ×6.1. I, GIK-2015, interior view of proximal brachials with well-developed lateral notches; ×5.7. J–K, No. GIK-2022, lateral and lateral–facet view of proximal plates; ×6.8/6.5. L, GIK-2023, interior view of a weathered proximal plate; ×6.8. M, GIK-2016, lateral view of a plate with well-developed lateral notches; ×7.7. N, GIK-2017, interior view; ×7.0.

Morphologic details of stylocrinids require further research. One fossil aboral cup of S. tabulatus represents the first evidence of the radular grazing ichnogenus RadulichnusVoigt, 1977, on a crinoid cup (Text-fig. 4). Isolated radial and basal plates have post-mortem borings of unknown organisms (Text-fig. 5A–T). Furthermore, other skeletal modifications, such as an aboral cup with an additional fourth basal plate (Text-fig. 6A–B) and the post-mortem skeletal encrusting by a rugose coral (Text-fig. 7A–B), are discussed.

Figure TEXT‐FIG. 4..

Stylocrinus tabulatus (Goldfuss, 1839), isolated, strongly weathered aboral cup GIK-2069, representing the first crinoid evidence of the radular grazing trace fossil ichnogenus RadulichnusVoigt, 1977 on two radials (framed); ×11.9.

Figure TEXT‐FIG. 5..

 A–S. Stylocrinus tabulatus (Goldfuss, 1839), post-mortem borings on isolated radials (A–F, I–T) and on one basal plate (G–H). A, GIK-2050, lateral view with one endolithic boring trace (B); ×7.5. C, GIK-2051, interior view with one endolithic boring trace (D); ×9.3. E, GIK-2052, lateral view with one external(?) boring (F) (compared to Figs K–L); ×7.4. G, GIK-2046, also figured in Text-figure 9Y, lateral view with one meandering boring trace (H); ×9.1. I, GIK-2053, lateral view of a fractured ossicle with one endolithic boring trace (J); ×7.7. K, GIK-2054, interior view with one external(?) boring trace (L) (compared to Figs E–F); ×9.1. M, GIK-2055, lateral view with one endolithic boring trace (N); ×6.5. O, GIK-2056, lateral view of a fractured ossicle with two endolithic boring traces (P); ×9.2. Q, GIK-2057, interior and facet views of an ossicle with numerous endolithic borings (R–S) at the ossicular facets; ×8.3.

Figure TEXT‐FIG. 6..

 A–B, Stylocrinus tabulatus (Goldfuss, 1839), abnormal aboral cup, GIK-2005 (leg. Schreuer), with four basal plates. A, Lateral view. B, Aboral view; ×5.0.

Figure TEXT‐FIG. 7..

 A–B, Stylocrinus tabulatus (Goldfuss, 1839), isolated aboral cup, GIK-2011; ×1.7 (A)/5.5 (B). The aboral cup was overgrown post-mortem by a rugose coral. The base of the rugose also encrusted a tabulate coral.

A neotype is proposed for the lost holotype of S. tabulatus.

Material and methods

In addition to a detailed analysis of previously published data and original material, this study focuses on the endoskeletal morphology of the aboral cup and brachials, mainly observed in newly discovered crinoids from the Rhenish Massif. They were prepared using micro sand-streaming methods, as well as fine pneumatic probes, and studied via binocular and scanning electron microscopic analyses (SEM). Photographs of crinoids coated with ammonium chloride were arranged using digital image-editing software.

Approximately 1500 aboral cups, one completely preserved and three partly preserved crowns, as well as one abnormal individual of S. tabulatus, were analysed. Additionally, 35 aboral cups of S. granulatus and 25 aboral cups of S. prescheri sp. nov. were studied.

Higher classification of stylocrinids follows Simms and Sevastopulo (1993). Morphologic dimensions are given in length and width as defined by Webster and Jell (1999).

The capitalisation of the Givetian subdivisions follows Becker (2005, 2007).

Geographical and stratigraphical occurrences of the genus and assigned species

Europe.  European Stylocrinus occurrences are mainly located within the Eifelian to Givetian deposits of the Rhenish Massif (Germany). The most prolific localities are in the Eifel Synclines and in the vicinity of Lahn-Dill (Text-fig. 8).

Figure TEXT‐FIG. 8..

 Geological overview of the Rhenish Massif (A), showing the studied area (red rectangle) (modified from Korn, 2008 after Walter, 1995) and detailed view of the Eifel Synclines (B) with the fossil localities 1–10 (modified after Struve 1996).

Localities within the Eifel (Rhineland-Palatinate, Germany), especially the middle Eifelian to lowermost Lower Givetian of the Hillesheim, Gerolstein and Prüm synclines, yielded the highest recorded species diversity. The generally common species S. tabulatus is geographically and stratigraphically widespread, but the rarer species occurred locally within shorter stratigraphical intervals. S. tabulatus was recovered from the Nohn Formation (lower Eifelian) to the Cürten Formation (Lower Givetian), whereas S. granulatus is limited to the Freilingen Formation (Eifelian), and S. prescheri sp. nov. occurred at the Eifelian/Givetian boundary.

Table 1.   The fossil localities and stratigraphic position of the studied crinoids.
No.LocalityUTMStratigraphy
GIK-2001Agricultural area, to the west of Schwirzheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)UnknownHönselberg Member, upper part of the Heinzelt Subformation, Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2002Schwirzheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)UnknownHönselberg Member, upper part of the Heinzelt Subformation, Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2003‘Hartelstein’, NE–Schwirzheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)UnknownHönselberg Member, upper part of the Heinzelt Subformation, Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2004Brühlborn (Prüm Syncline, Eifel, Rhenish Massif, Germany)UnknownKlausbach Member, lowermost part of the Heinzelt Subformation, lowermost part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2005Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)UnknownKlausbach Member, lowermost part of the Heinzelt Subformation, lowermost part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2006SW-’Hönselberg’, to the east of Loogh, south of Niederehe (Hillesheim Syncline, Eifel, Rhenish Massif, Germany)50°18′09.55″N/6°44′51.65″EEilenberg Member, lower part of the Freilingen Formation (upper Eifelian, Middle Devonian)
GIK-2007 to GIK-2010Pelm, to the east of Gerolstein (Gerolstein Syncline, Eifel, Rhenish Massif, Germany)UnknownLoogh Formation (Lower Givetian, Middle Devonian)
GIK-2011 to GIK-2017W-housing subdivision ‘Unterm Sportplatz’ of village Schwirzheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°13′50.53″N/6°31′08.72″EHönselberg Member, upper part of the Heinzelt Subformation, Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2018 to GIK-2057‘Mühlenwäldchen’, SW-Gerolstein (Gerolstein Syncline, Eifel, Rhenish Massif, Germany)50°13′16.14″N/6°39′01.00″EBaarley Member, lower part of the Loogh Formation (lowermost Lower Givetian, Middle Devonian)
GIK-2058600 m SE of Ahrdorf (Ahrdorf Syncline, Eifel, Rhenish Massif, Germany)UnknownEilenberg Member, lower part of the Freilingen Formation (upper Eifelian, Middle Devonian)
GIK-2059 to GIK-2060SW-housing subdivision of village Gondelsheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°13′58.85″N/6°29′52.50″ENims Member, lower part of the Grauberg Subformation, upper part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2061E-Niederehe (Hillesheim Syncline, Eifel, Rhenish Massif, Germany)50°18′46.72″N/6°46′13.74″EKlausbach Member, lowermost part of the Heinzelt Subformation, lowermost part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2062W-industrial area, SE of Weinsheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°13′32.14″N/6°28′42.97″EUpper part of the Rech Member, upper part of the Loogh Formation (Lower Givetian, Middle Devonian)
GIK-2063 to GIK-2066SW-housing subdivision ‘Im Leimenpeschen’ of village Schwirzheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°13′47.54″N/6°31′17.35″EHönselberg Member, upper part of the Heinzelt Subformation, Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2067 to GIK-2068W-Gondelsheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°14′03.31″N/6°29′50.47″EKlausbach Member, lowermost part of the Heinzelt Subformation, lowermost part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2069 to GIK-2071‘Mühlenwäldchen’, SW-Gerolstein (Gerolstein Syncline, Eifel, Rhenish Massif, Germany)50°13′16.14″N/6°39′01.00″EBaarley Member, lower part of the Loogh Formation (lowermost Lower Givetian, Middle Devonian)
GIK-2072 to GIK-2074Abandoned quarry ‘Weinberg’, NW of Kerpen (Hillesheim Syncline, Eifel, Rhenish Massif, Germany)50°18′54.47″N/6°42′53.63″EBohnert Member, upper part of the Freilingen Formation (upper Eifelian, Middle Devonian)
GIK-2075‘Auf den Eichen’, NE of Nollenbach (Hillesheim Syncline, Eifel, Rhenish Massif, Germany)50°19′45.81″N/6°44′38.33″EBohnert Member, upper part of the Freilingen Formation (upper Eifelian, Middle Devonian)
GIK-2076 to GIK-2077Agricultural area, to the west of Gondelsheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°13′58.95″N/6°29′44.73″ENims Member, lower part of the Grauberg Subformation, upper part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2078 to GIK-2086Slope of the former planned roadwork extension of federal road ‘B51’, south of Brühlborn, Northeast of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°12′27.14″N/6°27′37.45″EOlifant Member, lower part of the Müllert Subformation, Ahbach Formation (lowermost Lower Givetian, Middle Devonian)
GIK-2087 to GIK-2102Slope of the former planned roadwork extension of federal road ‘B51’, south of Brühlborn, northeast of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°12′24.88″N/6°27′38.58″ENims Member, lower part of the Grauberg Subformation, upper part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
GIK-2275Slope of the former planned roadwork extension of federal road ‘B51’, south of Brühlborn, northeast of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°12′24.88″N/6°27′38.58″ENims Member, lower part of the Grauberg Subformation, upper part of the Junkerberg Formation (upper middle Eifelian, Middle Devonian)
MWNH-306a to MWNH-306bWeilburg-Odersbach, NE of Limburg an der Lahn (Lahn-Dill Syncline, Rhenish Massif, Germany)UnknownLowermost part of the Middle Givetian (Middle Devonian) ‘Roteisenstein’
MWNH-306e to MWNH-306fWeilburg-Odersbach, NE of Limburg an der Lahn (Lahn-Dill Syncline, Rhenish Massif, Germany)UnknownLowermost part of the Middle Givetian (Middle Devonian) ‘Roteisenstein’
SMF-75408Slope of the former planned roadwork extension of federal road ‘B51’, south of Brühlborn, northeast of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany)50°12′27.14″N/6°27′37.45″EOlifant Member, lower part of the Müllert Subformation, Ahbach Formation (lowermost Lower Givetian, Middle Devonian)

Within the vicinity of Lahn-Dill, stylocrinids occur in deposits younger than the Eifel. S. tabulatus and, rarer, S. prescheri sp. nov. were found within the lowermost Middle Givetian ‘Roteisenstein’ near Weilburg-Odersbach, NE of Limburg an der Lahn (Hesse, Germany).

Asia. Reed (1908) reported an aboral cup of Hexacrinus aff. pyriformis from the Devonian of the Northern Shan States (Burma). The figured aboral cup (1908, p. 40, pl. 5, fig. 13) can clearly be assigned to S. tabulatus and is recognised as the first report of the genus from Asia.

Stylocrinids are also known from the Asian part of Russia. As documented by Dubatolova (1971), the genus occurs within the Eifelian deposits of NE Salair, near Gur’evsk (Kemerowo, Siberia, Russia; western part of the central Kusbass). The figured aboral cups can be assigned to S. prescheri (1971, pl. 1, fig. 5a–b) and S. tabulatus (1971, pl. 1, figs 6a–b, 7a–b; pl. 2, figs 1a–c, 2a–b).

Australia. Jell and Jell (1999) reported aboral cups of S. tabulatus from the Frasnian part of the Sadler Limestone (lower Upper Devonian); this is the youngest report of the genus. The silicified aboral cup (1999, pp. 229–230, fig. 26A–D) was found SW of ‘Wade Knolls’ in ‘Paddy’s Valley’ of Western Australia.

Repository.  Type specimens are deposited in the Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt am Main, Germany (SMF), the Steinmann-Institut für Geologie, Mineralogie und Paläontologie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Germany (IPB), and the Naturhistorische Landessammlung, Museum Wiesbaden, Germany (MWNH). Additional specimens are stored in the collections of the Institut für Geologie und Mineralogie der Universität zu Köln, Germany (GIK), and the Queensland Museum, Queensland (QMF).

Systematic Palaeontology

Subclass DISPARIDA Moore and Laudon, 1943
Superfamily BELEMNOCRINOIDEA Miller, 1883
Family SYNBATHOCRINIDAE Miller, 1889

Genus STYLOCRINUS Sandberger and Sandberger, 1856

Type species. Platycrinites tabulatusGoldfuss, 1839, from the Middle Devonian of the Eifel (Germany).

Description.  Crown slender, long and lanceolated, with an unsculptured or typically pustulated surface (S. tabulatus, S. prescheri sp. nov.) or, rarely, sculptured by unoriented ridges, crinkles and tubercles (S. granulatus), sometimes moderately facetted parallel to the radial flanges (S. tabulatus, S. prescheri sp. nov.); stem narrow, circular in cross section, with one central, pentalobate axial canal; monocyclic aboral cup with highly variable morphology, typically bowl shaped, frequently transitions between cone, bowl and globe shape (S. tabulatus, S. granulatus), but inverted ‘pear-shaped’ in S. prescheri sp. nov.; aboral cup of S. tabulatus three times wider than long, as long as wide to three times longer than wide; aboral cup composed of three basals, forming a convex base, and five radials with plenary radial facets with a distinct transverse ridge; atomous arms; the brachials are rectilinear in external view; strongly convex transversely, straight longitudinally; internally inclined edges adjoined laterally with adjacent brachials in an interlocking network; irregularly distributed notches occur laterally, diagonally positioned to each other, bearing obviously rudimentary arm appendages (pinnules?).

Occurrence.  Middle to Upper Devonian. Eifelian: Asia (Salair, Kemerowo, Siberia, Russia). Eifelian–Givetian: Europe (Germany). Frasnian: Western Australia. Slightly modified from Webster (2003).

Remarks.  The features of the plenary radial facets of the disparid Stylocrinus, as well as all other members of the Synbathocrinidae, correspond to those defined for cladids by Webster (2007, pp. 325–328).

The crinoid described by Strimple (1963, pl. 1, figs 6–8) as Stylocrinus elimatus (also see Webster 1973, p. 247; 2003) does not belong to Stylocrinus. Presumably, S. elimatus probably belongs to the Pisocrinidae Angelin, 1878 (own observation). In contrast to the diagnosis of Stylocrinus published by Strimple (1963; also inMoore et al. 1978, p. T560), the aboral cup of Stylocrinus consistently possesses three, not five, basal plates. This is a constant feature present on all of the approximately 1500 aboral cups studied.

The recently published drawing of a Stylocrinus model (Hauser 2008, p. 25, fig. 48) is erroneous. Incorrect aspects of the model are as follows: (1) a circular, instead of a pentalobate axial canal; (2) five instead of three basals; and (3) the brachials lack the internally inclined edges adjoined laterally with adjacent brachials in an interlocking network (see Revised diagnosis).

Because Polyarnaya (1986) designated S. scaber as a junior synonym of P. tabulatus, the type species of StylocrinusSandberger and Sandberger, 1856, is Platycrinites tabulatusGoldfuss, 1839, not ‘Stylocrinus scaberSandberger and Sandberger, 1856’, as stated inMoore et al. (1978, p. T560) and Hauser (2008, p. 25).

The occurrence of Stylocrinus within the Silurian deposits of the United States (Strimple 1963) is rejected based on the revised diagnosis presented here.

Stylocrinus tabulatus (Goldfuss, 1839)
Text-figures 1–7, 9–10

Figure TEXT‐FIG. 9..

 A–AC, Stylocrinus tabulatus (Goldfuss, 1839), isolated radials (A–X) and basals (Y–AC) in lateral (A–U, W–AB) and facet views (V, AC). A, GIK-2024; ×6.1. B, GIK-2025; ×7.1. C, GIK-2026; ×5.3. D, GIK-2027; ×5.6. E, GIK-2028; ×6.3. F, GIK-2029; ×5.4. G, GIK-2030; ×8.2. H, GIK-2031; ×6.1. I, GIK-2032; ×7.6. J, GIK-2033; ×6.0. K, GIK-2034; ×5.6. L, GIK-2035; ×8.0. M, GIK-2036; ×8.7. N, GIK-2037; ×5.6. O, GIK-2038; ×8.6. P, GIK-2039; ×8.1. Q, GIK-2040; ×5.2. R, GIK-2041; ×8.3. S, GIK-2042; ×8.4. T, GIK-2043, interior view; ×6.4. U–V, GIK-2044, interior side and view of plenary radial facets; ×6.1/6.8. W–X, GIK-2045, interior view; ×6.7/6.2. Y, GIK-2046, also figured in Text-figure 5G–H; ×7.5. Z, GIK-2047, interior view; ×7.2. AA, GIK-2048; ×7.6. AB–AC. GIK-2049; ×6.4/10.4.

Figure TEXT‐FIG. 10..

Figure TEXT-FIG. 10..

 A–AN, Stylocrinus tabulatus (Goldfuss, 1839), the transitions between the different morphologies of the aboral cup and variations of plate sculpturing (A–Q and S–AN lateral view, R aboral view). A, GIK-2007; ×3.8. B, GIK-2008; ×5.4. C, GIK-2087; ×4.7. D, GIK-2089; ×4.0. E, GIK-2060; ×3.2. F, GIK-2076; ×3.2. G, GIK-2090 (leg. Schreuer), one columnal preserved; ×3.6. H, GIK-2068; ×3.7. I, GIK-2092; ×6.7. J, MWNH-306e, one columnal preserved; ×3.5. K, GIK-2009; ×4.4. L, GIK-2067; ×2.7. M, GIK-2006; ×2.0. N, GIK-2058 (leg. Hein), one columnal preserved; ×2.6. O, GIK-2091 (leg. Hein); ×3.4. P, GIK-2077; ×2.8. Q, GIK-2010; ×3.4. R–S, GIK-2002 (leg. Leunissen), aboral cup with atypical narrow basis; ×4.0. T, GIK-2059; ×3.6. U, GIK-2093 (leg. Schreuer); ×3.5. V, GIK-2094 (leg. Schreuer); ×3.5. W, GIK-2063 (leg. Schreuer); ×3.5. X, GIK-2064 (leg. Schreuer); ×3.3. Y, GIK-2065 (leg. Schreuer); ×3.8. Z, GIK-2095; ×3.8. AA, Proposed neotype, IPB-Bohatý-10; ×3.1. AB, GIK-2096 (leg. Schreuer); ×3.4. AC, GIK-2098; ×2.9. AD, GIK-2097 (leg. Schreuer); ×4.2. AE, GIK-2099 (leg. Schreuer); ×3.1. AF, GIK-2100 (leg. Schreuer); ×3.1. AG, GIK-2061; ×4.0. AH, GIK-2070; ×2.4. AI, GIK-2071; ×2.1. AJ, GIK-2066 (leg. Schreuer); ×2.8. AK, GIK-2101 (leg. Schreuer); ×2.9. AL, GIK-2062 (leg. Hein), part of stem preserved; ×2.7. AM, MWNH-306f; ×4.5. AN, GIK-2088 (leg. Hein); ×2.9.

  • 1839  Platycrinites tabulatus Goldfuss, p. 345.

  • 1849–1856 Stylocrinus scaber Sandberger and Sandberger, p. 400, pl. 35, fig. 12.

  • 1852  Platycrinus tabulatus (Goldfuss, 1839); Quenstedt, p. 618, pl. 54, figs 25a–c.

  • 1855  Symbathocrinus tabulatus (Goldfuss, 1839); Müllerin Zeiler and Wirtgen, p. 19, pl. 4, figs 4–5.

  • 1855  Symbathocrinus tabulatus var. altaMüller, in Zeiler and Wirtgen, p. 19, pl. 6, fig. 5.

  • 1855  Symbathocrinus tabulatus var. depressaMüllerin Zeiler and Wirtgen, p. 19, pl. 6, fig. 4.

  • 1866  Symbathocrinus tabulatus var. depressa Mueller, J. in Zeiler and Wirtgen; Schultze, pp. 28–29, pl. 3, fig. 5a–b.

  • p. 1866 Symbathocrinus tabulatus (Goldfuss, 1839); Schultze, pp. 27–28 (pars), pl. 3, fig. 4h, non figs 4c (? = S. prescheri sp. nov.), 4d, g (=Crinoidea indet.), 4e–f (= Eohalysiocrinus sp.), 4i (= S. granulatusHauser, 1997).

  • 1866 Symbathocrinus tabulatus var. alta Mueller, J. in Zeiler and Wirtgen; Schultze, p. 27, pl. 3, fig. 4, 4a–b.

  • 1876  Platycrinus tabulatus variatio alta (Müller); Quenstedt, p. 558, pl. 109, fig. 47.

  • 1876  Platycrinus tabulatus variatio depressa (Müller); Quenstedt, p. 558, pl. 109, fig. 49.

  • 1876 Stylocrinus scaber Sandberger and Sandberger; Quenstedt, p. 558, pl. 109, fig. 50.

  • 1885 Platycrinites tabulatus Goldfuss; Quenstedt, p. 952, pl. 76, fig. 17.

  • 1908 Hexacrinus aff. pyriformis (Schultze); Reed, p. 40, pl. 5, fig. 13.

  • p. 1971 Stylocrinus tabulatus (Goldfuss, 1839); Miesen, p. 5, pl. 4, fig. 9g (undescribed), non fig. 9h (undescribed) (= S. granulatusHauser, 1997).

  • p. 1971 Stylocrinus tabulatus tabulatus (Goldfuss, 1839); Dubatolova, p. 19, pl. 1, figs 6–8, non fig. 5 (= S. prescheri sp. nov.), non fig. 9 (=Crinoidea indet.).

  • p. 1971 Stylocrinus tabulatus var. alta (Mueller); Miesen, pl. 3, figs 9, 9a–b, non pl. 4, fig. 9c (? = S. prescheri sp. nov.).

  • 1971 Stylocrinus var. depressa; Miesen, pl. 4, figs 10, 10a–b.

  • p. 1971 Stylocrinus tabulatus depressus (Müller, 1855); Dubatolova, p. 21, non pl. 1, figs 10–11 (= Crinoidea indet.); pl. 2, figs 1–2.

  • p. 1974 Stylocrinus tabulatus (Mueller); Miesen, p. 77, fig. 1, non figs 1a (=S. granulatusHauser, 1997), 1b (? = S. prescheri sp. nov.).

  • 1974 Stylocrinus tabulatus var. depressa (Müller, 1855); Miesen, pl. 77, figs 2 (unnumbered), 2a–b.

  • 1974 Stylocrinus tabulatus var. alta (Mueller); Miesen, pl. 76, figs 4, 4a–b.

  • 1978 Stylocrinus scaber Sandberger and Sandberger; Moore et al. p. T560, fig. 353: 2a–c.

  • 1986 Stylocrinus tabulatus altus (Müller, 1855); Polyarnaya, p. 77, unnum. pl., fig. 1; fig. 3.

  • 1986 Stylocrinus tabulatus depressus (Müller, 1855); Polyarnaya, p. 78, unnum. pl., fig. 2; fig. 2.

  • p. 1997 Stylocrinus tabulatus (Goldfuss, 1839); Hauser, p. 96, pl. 70, fig. 5 (not pl. 70, figs 1, 9 as given p. 96 (sic)), non figs 1–2 (= Phimocrinus laevisSchultze, 1866).

  • 1997 Stylocrinus tabulatus alta (Müller, 1855); Hauser, pp. 96, 98, pls 70, figs 6–7; 71, fig. 1.

  • 1997 Stylocrinus tabulatus depressa (Müller, 1855); Hauser, p. 97, pl. 71, figs 2, 8.

  • 1999 Stylocrinus tabulatus (Goldfuss, 1839); Jell and Jell, p. 229, fig. 26, nos. A–D.

  • 2001 Stylocrinus tabulatus (Goldfuss, 1839); Hauser, pp. 134–137, pl. 13, figs 5–6.

  • 2001 Stylocrinus tabulatus altus (Müller, 1855); Hauser, p. 135.

  • 2001 Stylocrinus tabulatus depressa (Müller, 1855); Hauser, p. 136.

  • 2001 Stylocrinus tabulatus depressus (Müller, 1855); Hauser, pp. 135–137, pl. 25, fig. 4.

  • non 2008 Stylocrinus tabulatus (Goldfuss, 1839); Hauser, p. 26, fig. 49 (= Stylocrinus prescheri sp. nov.) (described as Stylocrinus tabulatus depressusMüllerin Zeiler and Wirtgen, 1855 by Hauser, 2008, pl. 1, fig. 5 (sic)).

  • 2008 Stylocrinus scaber Sandberger and Sandberger; Hauser, p. 25, fig. 46.

  • non 2008 Stylocrinus tabulatus depressus (Müller, 1855); Hauser, pl. 1, fig. 5 (= Stylocrinus prescheri sp. nov.) (described as Stylocrinus tabulatus by Hauser, 2008, p. 26, fig. 49 (sic)).

Proposed neotype.  Aboral cup, no IPB-Bohatý-10 (Text-fig. 5AA).

Revised description.  Crown slender, long and lanceolated, with an unsculptured or typically pustulate or fine granulate surface, in some cases moderately faceted parallel to the radial flanges; stem narrow, circular in cross-section, with one central, pentalobate axial canal; aboral cup with highly variable morphology regarding length and width proportions (Text-fig. 10A–AN), typically bowl shaped, but also cone, bowl and globe shaped; aboral cup three times wider than long, as long as wide to three times longer than wide, widest lateral radius of aboral cup at the radial facets; aboral cup composed of three basals, forming a convex base, and five radials with plenary radial facets with distinct transverse ridges; atomous arms; the brachials are rectilinear in external view; strongly convex transversely, straight longitudinally; internally inclined edges adjoin laterally with adjacent brachials in an interlocking network (Text-figs 1, 2A–C, E–F); inordinately distributed notches occur laterally, diagonally positioned to each other (Text-figs 1, 3E, G–I, M–N), bearing obvious rudimentary arm appendages (pinnules?) (Text-fig. 3C, E).

Type locality.  The type locality within the Eifel was not given in the original description (Goldfuss 1839, p. 345). The type locality of the proposed neotype is the slope of the former planned roadwork extension of federal road B51, south of Brühlborn, north-east of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany); 50°12′24.88″N, 6°27′38.58″E.

Type horizon.  The type horizon within the Eifel was not given in the original description (Goldfuss 1839, p. 345). The type horizon of the proposed neotype is the Nims Member of the lower Grauberg Subformation, upper part of the Junkerberg Formation, late middle Eifelian (Middle Devonian); kockelianus Conodont Biozone.

Occurrence.  As for genus.

Discussion.  The high ecophenotypic plasticity and the resulting morphological variability of S. tabulatus aboral cups resulted in the subspecific differentiation by Müllerin Zeiler and Wirtgen (1855): Symbathocrinus tabulatus var. alta and S. t. var. depressa were established for short and long aboral cups. An analysis of approximately 1500 aboral cups in the present study demonstrates gradual transitions between the extremes of length and width proportions. Therefore, both subspecies are combined with S. tabulatus, whereby the nominal subspecies S. tabulatus tabulatus is discarded. Jell and Jell (1999, p. 229) assigned the stylocrinids that they described (with length = width intermediate between altus (length > width) and depressus (width > length)) to the broader species concept. Disregarding the nominal subspecies S. t. tabulatus, the attempt of Hauser (2001, p. 135) to interpret all with length > width as S. tabulatus and all the remainder as S. t. depressus is, therefore, irrelevant. This conclusion is confirmed by the identical brachials, the consistent morphology of the plenary radial facets of all S. tabulatus morphotypes and the same stem facet. Similarly, the development of plate sculpturing and the irregularly arranged lateral depressions of the brachials may vary both in short and long aboral cups. However, it should be noted that several S. tabulatus localities yield a relatively constant spectrum of either short or long aboral cups, whereas other places, like the new type locality, have the broad spectrum of gradual transitions. Likewise, the dimensions are regionally different. Very prolific localities are dominated by smaller individuals. Especially in the late middle Eifelian in the vicinity of Gondelsheim (Prüm Syncline, Eifel, Rhenish Massif, Germany; 50°13′58.95″N, 6°29′44.73″E and eastward to 50°13′58.85″N, 6°29′52.50″E), rare findings of large specimens are characteristic.

The atomous brachial construction, with interlocked lateral depressions, may support a sturdy resting or avoidance posture, which possibly affords heightened tolerance against hydrodynamic influences or predatory attacks. The lateral interlocking of atomous arms is also known in Australian cupressocrinitids (compare to Jell et al. 1988, p. 394, fig. 26H).

The strongly convex brachials have distributed notches, which occur laterally, diagonally positioned to each other (Text-figs 1, 3E, G–I, M–N). These notches bear an obvious rudimentary arm appendage (pinnules?) (Text-fig. 3C, E) that possibly could extend in a semiclosed arm-crown position and may have allowed feeding in a protected posture.

Stylocrinus granulatusHauser, 1997
Text-figure 11

Figure TEXT‐FIG. 11..

Figure TEXT-FIG. 11..

 A–D, Stylocrinus granulatusHauser, 1997, isolated aboral cups in aboral (A–B) and lateral view (C–D). A, GIK-2074, showing pentalobate columnal axial canal and typical wide base; ×4.6. B, GIK-2073, showing pentalobate columnal axial canal and typical wide base; ×5.4. C, GIK-2072, plate sculpturing well preserved; ×4.3. D, GIK-2075; ×3.7.

  • 1866 Symbathocrinus tabulatus (Goldfuss); Schultze, pl. 3, fig. 4i.

  • 1971 Stylocrinus tabulatus (Goldfuss, 1839); Miesen, pl. 4, fig. 9h.

  • 1974 Stylocrinus tabulatus (Mueller); Miesen, p. 77, fig. 1a.

  • * 1997 Stylocrinus granulatus Hauser, pp. 98–99, pl. 71, figs 3–4.

  • 1997 Stylocrinus granulosa (sic) Hauser; Hauser, pp. 14, 98–99.

  • 2001 Stylocrinus granulatus Hauser; Hauser, p. 193.

  • 2001 Stylocrinus granulosus (sic) Hauser; Hauser, pp. 137, 151.

Holotype.  Aboral cup, no. MB.E.-2580 (not MB.E.-2581 as wrongly stated by Hauser 1997, p. 98; C. Neumann, pers. comm. 2008).

Description.  A Stylocrinus with a medium-length cone shape and monocyclic aboral cup with subhorizontal to slightly depressed and wide base with narrow stem impression (Text-fig. 11A–B), all in all ‘flowerpot-like’ shape (Text-fig. 11C–D); aboral cup composed of three basals and five radials with plenary radial facets; plate boundaries notched; plates sculptured with rough, unaligned sculpturing (meandering crinkles and/or tubercles, Text-fig. 11A–D); widest lateral radius of aboral cup at the radial facet; stem narrow, circular in cross-section, with one central, pentalobate axial canal. Arms, complete stem and holdfast unknown.

Type locality.  ‘Auf den Eichen’, north-east of Nollenbach (Hillesheim Syncline, Eifel, Rhenish Massif, Germany); 50°19′45.81″N, 6°44′38.33″E.

Type horizon.  Bohnert Member of the upper part of the Freilingen Formation, upper Eifelian (Middle Devonian); kockelianus/ensensis Conodont Biozone.

Occurrence.  Type locality and abandoned ‘Weinberg Quarry’ near Kerpen (Hillesheim Syncline, Eifel, Rhenish Massif, Germany); 50°18′54.47″N, 6°42′53.63″E.

Discussion.  This rare species of Stylocrinus is characterised by rough plate sculpturing (Text-fig. 11C) and the wide base (Text-fig. 11B). The new localities yield a relatively low diversity of aboral cup morphologies in comparison with the common S. tabulatus, which is rarely associated with relatively small individuals. S. granulatus is a very constant form with the shortest stratigraphical range of all known stylocrinids. The species became established after a regional event at the threshold of the Junkerberg and Freilingen formations of the late middle to upper Eifelian (otomari Event sensuStruve et al. 1997, i.e. a transgression that resulted in sedimentary changes within the Eifel region). The occurrence of S. granulatus is strictly limited to the Bohnert Member (upper part of the Freilingen Formation, upper Eifelian). Apparently, the species was unable to survive the rapid sedimentary changes found in the overlying Ahbach Formation (Eifelian/Givetian boundary).

Stylocrinus prescheri sp. nov.
Text-figure 12

Figure TEXT‐FIG. 12..

Figure TEXT-FIG. 12..

 A–P, Stylocrinus prescheri sp. nov., isolated aboral cups. A, GIK-2084 (leg. Prescher), lateral view of a typical aboral cup; ×3.3. B, GIK-2078, lateral view; ×3.6. C, GIK-2080 (leg. Leunissen), lateral view of a strongly sculptured aboral cup; ×3.5. D, GIK-2081 (leg. Schreuer), lateral view; ×4.6. E, Same as A, oral view; ×3.3. F, GIK-2079 (leg. Schreuer), oral view of a juvenile aboral cup; ×5.7. G, GIK-2082 (leg. Prescher), lateral view; ×2.7. H, Holotype, SMF-75408, lateral view of slightly compressed aboral cup; ×2.8. I, GIK–2085 (leg. Prescher), lateral view; ×3.4. J, GIK-2083 (leg. Prescher), lateral view; ×3.9. K, GIK-2086 (leg. Prescher), lateral view; ×5.0. L–P, MWNH-306b, unfigured original of Sandberger and Sandberger (1856); ×4.9 (L, aboral, M, lateral, N–O, lateral-oral and P, oral view).

  • ? 1866 Symbathocrinus tabulatus (Mueller); Schultze, pl. 3, fig. 4c.

  • 1971 Stylocrinus tabulatus tabulatus (Goldf.); Dubatolova, pl. 1, figs 5a–5.

  • ? 1971 Stylocrinus tabulatus var. alta (Mueller); Miesen, pl. 4, fig. 9c.

  • ? 1974 Stylocrinus tabulatus (Mueller); Miesen, p. 77, fig. 1b.

  • 2008 Stylocrinus tabulatus (Goldfuss, 1839); Hauser, p. 26, fig. 49 (also figured on pl. 1, fig. 5, described as Stylocrinus tabulatus depressusMüllerin Zeiler and Wirtgen, 1855 (sic)).

  • 2008 Stylocrinus tabulatus depressus (Goldfuss, 1839); Hauser, pl. 1, fig. 5 (also figured on p. 26, fig. 49, described as Stylocrinus tabulatusGoldfuss, 1839 (sic)).

Derivation of name.  In honour of Mr. Harald Prescher (Kerpen-Horrem, Germany), the discoverer of the fossil layer at the type locality.

Holotype.  Aboral cup, no. SMF-75408 (Text-fig. 12H).

Diagnosis.  A Stylocrinus with an inverted pear-shaped aboral cup (Text-fig. 12A), wider than long, composed of three basals, forming a convex base, and five radials with plenary radial facets, radials peltiform, with widest diameter at the lower edges, narrowing distally; the widest lateral radius of the aboral cup is close to the radial/basal boundary; radial circlet constricted (Text-fig. 12E–F, N–P); stem narrow, circular in cross-section, with one central, pentalobate axial canal. Arms, complete stem and root unknown. See Table 2 for dimensions of the holotype.

Table 2.   Dimensions (max.) of the Stylocrinus prescheri sp. nov. holotype.
Aboral cup no.Length/width of aboral cup (mm)Length/width of basalia (mm)Length/width of radialia (mm)Diameter of stem impression (mm)Diameter of stem facet (mm)
SMF-754089 × 13 (compressed)5.3 × 9.05.5 × 6.05.02.5

Description.  The aboral cup is inverted pear shaped (Text-fig. 12A), wider than long and has its widest lateral radius close to the radial/basal boundary. The stem impression is surrounded by a moderate concavity, which is surrounded by the lower rims of the three unequal basals, which formed a wide and convex base (Text-fig. 12L). All basals are sculptured by irregularly or slightly aligned coarser granules (Text-fig. 12C, I). The proximal part of the aboral cup is nearly as long as the radial circlet. Radials peltiform, with the widest diameter at the basal/radial boundary, constricted distally and also sculptured by mostly irregular arranged granules, or sculpturing arcuately arranged, parallel to the lower flange of the radials. The radials of adult aboral cups have arcuate sculpturing below the plenary radial facets, distal to a projecting stage (Text-fig. 12A). Stem narrow, circular in cross-section and penetrated by a single, small and pentalobate axial canal.

Type locality.  Slope of the former planned roadwork extension of federal road B51, south of Brühlborn, north-east of Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany); 50°12′27.14″N, 6°27′37.45″E.

Type horizon.  Olifant Member of the lower part of the Müllert Subformation, Ahbach Formation (lowermost Lower Givetian, Middle Devonian); hemiansatus Conodont Biozone.

Occurrence.  Mamontovsk’i Member, Pesterevsk’i Limestone (Middle Devonian, Eifelian), NE Salair, near Gur’evsk, Kemerowo, Siberia, Russia; western part of the central Kusbass, Asia. Lower part of the Ahbach Formation (upper Eifelian) to the upper part of the Ahbach Formation to (?)Loogh Formation (lowermost Lower Givetian), Prüm Syncline, Brühlborn/Rommersheim and Hillesheim Syncline, Ahütte, both Eifel, Rhenish Massif, Germany. Roteisenstein (lowermost Upper Givetian), Grube Lahnstein near Weilburg-Odersbach, NE of Limburg an der Lahn, Rhenish Massif, Lahn-Dill Syncline, Germany.

Discussion.  The inverted pear-shaped aboral cup clearly separates S. prescheri sp. nov. from all morphotypes of S. tabulatus and S. granulatus. A simplified model of the characteristic aboral cup morphologies, differentiating the new species from S. tabulatus and S. granulatus, is given in Text-figure 13.

Figure TEXT‐FIG. 13..

Figure TEXT-FIG. 13..

 Idealised sketches of the most characteristic morphological features, distinguishing Stylocrinus prescheri sp. nov. (A), S. tabulatus (Goldfuss, 1839) (B) and S. granulatusHauser, 1997 (C).

At all known S. prescheri localities, this rare stylocrinid is associated with S. tabulatus; an association of S. prescheri sp. nov. and S. granulatus was not observed. Within the Eifel Synclines, the new species is restricted to strata close to the Eifelian/Givetian boundary. The few localities within the Rhenish Massif yield a relatively low diversity of aboral cup morphologies in comparison with the more common S. tabulatus.

Pre- and post-mortem skeletal modifications of Stylocrinus

Premortem modifications

In spite of the very large number of aboral cups and in contrast to camerate and especially to cladid crinoids, premortem skeletal modifications of the disparid Stylocrinus are extremely rare and were observed on only two of approximately 1500 individuals.

The aboral cup no. GIK-2005 developed an anomalous, additional basal plate (Text-fig. 6A–B). This kind of pathology was recently classified in cupressocrinitids as ‘growth anomaly without recognisable external influences’ and was probably characterising ‘genetic abnormalities’ (Bohatý 2009, p. 53).

The aboral cup no. GIK-2002 has an uncommon base with a narrow stem insertion (Text-fig. 10R–S), which possibly is attributed to a skeletal regeneration(?) of the base. Skeletal anomalies in Devonian crinoids have recently been described in the cladid cupressocrinitids, gasterocomoids and bactrocrinids (Bohatý 2001, 2005a, b, 2006a, b; Bohatý and Herbig 2010), and in the camerate hexacrinitids (Bohatý 2001, 2006c, d, 2010). Bohatý (2009) presented an extensive discussion about pre- and post-mortem skeletal modifications of the cupressocrinitid skeletons.

Post-mortem modifications

Post-mortem skeletal modifications in the form of ossicular borings are common in stylocrinids. Almost 60 per cent of the specimens studied had been penetrated by two types of borings. One type is rectilinear or less meandering, endolithic borings of unknown affinity (Text-fig. 5A–F, I–T). Most likely, they were made after the disarticulation of the aboral cup, because the origin of most of these traces is at the radial or basal plate margins. The second type has radial and basal plates (Text-fig. 5G–J) that were affected by surficial meandering borings of an unknown organism. These types are more rare in comparison with the endolithic traces. Different pre- and post-mortem borings occurred as single and multiple borings observed in cupressocrinitid skeletons described by Bohatý (2009). They differ from the stylocrinid traces, which are related to the undescribed borings on the isolated radials of Edriocrinus sp. illustrated by Prokop and Petr (1995, pl. 1, figs 1–16). The ossicles, especially the radials, of both species have very similar morphologies.

One aboral cup of S. tabulatus represents the first nonplatyceratid gastropod trace fossil observed on a crinoid skeleton and was identified as the radular grazing trace fossil ichnogenus RadulichnusVoigt, 1977 (Text-fig. 4), recently detected on Eifelian Brachiopods from the Rhenish Massif (M. Grigo, pers. comm. 2008). These traces have been attributed to the activity of polyplacophorid and patellid gastropods (Voigt 1977), but their affinity remains unclear.

One isolated S. tabulatus aboral cup was overgrown post-mortem by a rugose coral, which attached to the oral side of the radial facets with its root-like basal extensions (Text-fig. 7A–B). The ossicles not covered by the coral (radials and basals) remained articulated during the growth of the coral and, therefore, were probably enclosed by the sediment.

Discussion

The present study shows that the aboral cup length/width proportions and plate sculpturing in Stylocrinus tabulatus are highly variable. The rarer species, S. granulatus and the new S. prescheri, are less variable. Also, former authors differentiated S. tabulatus into three subspecies (S. t. tabulatus, S. t. altus and S. t. depressus); the analysis of approximately 1500 aboral cups in varying between short and long aboral cups clearly demonstrates that the intraspecific morphological variability of the type species is a result of its ecophenotypic plasticity.

Within the Eifel, the stratigraphic distribution of the rarer taxa is confined to the Freilingen and Ahbach formations (upper Eifelian), whereas S. tabulatus is known from the lower, middle and upper Eifelian to the lowermost part of the Lower Givetian. The lowermost Upper Givetian S. tabulatus and S. prescheri from the Lahn Syncline are the youngest European occurrences. But the stylocrinids from Western Australia demonstrate that the genus continued from the lowermost part of the lower Eifelian (Middle Devonian) to at least the Frasnian (Upper Devonian).

Stylocrinus granulatus has the shortest stratigraphical range of all known stylocrinids. This ecologically highly adapted species became established after the otomari Event at the boundary of the Junkerberg and Freilingen formations (upper Eifelian) but became extinct by the first change of the postevent facies with the beginning of the superposed Ahbach Formation (Eifelian/Givetian boundary).

Several localities within the Eifel contain mass occurrences of S. tabulatus, for example within the Junkerberg Formation (Eifelian) of Schwirzheim and Rommersheim (Prüm Syncline, Eifel, Rhenish Massif, Germany); however, the findings are nearly completely restricted to isolated aboral cups. Post-mortem, the aboral cups were relatively robust in contrast to the mostly disarticulated brachials. Therefore, crowns are rare. The post-mortem stability of the aboral cup is also confirmed by the overgrowth of an adult rugose coral, using the aboral cup as hard ground during its growth, without disarticulation of the stylocrinid.

Considering the large number of stylocrinid aboral cups studied, it is also remarkable that, in contrast to cladid and camerate crinoids from the Eifel, only two abnormal individuals were recovered.

Acknowledgements.  I thank G. Fiscus (Alzey), H.-P. Hein (Wermelskirchen), U. Hein (Solingen), R. Leunissen (Wollersheim), H. Prescher (Kerpen-Horrem) and J. Schreuer (Bochum) for the recovery of the studied crinoids. H. Prescher kindly donated the type material to the Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt am Main, Germany. I also thank U. Hein and H. Prescher for their friendly support of preparing the images. D. Heidelberger (Oberursel/Ts.) and F. Geller-Grimm (Naturhistorische Landessammlung, Museum Wiesbaden, Germany) permitted access to the Sandberger collection. G. Heumann (Bonn) and C. Neumann (Berlin) permitted access to the Goldfuss-Museum der Rheinischen Friedrich-Wilhelms-Universität Bonn, Germany, and the Museum für Naturkunde der Humboldt-Universität zu Berlin, Germany. G. D. Webster (Washington State University) and W. I. Ausich (School of Earth Sciences, Ohio State University) thoughtfully revised a first manuscript version; I thank both for numerous important comments and their continuous encouragement.

The reviews of G. C. McIntosh (Rochester Museum and Science Center) and of an anonymous reviewer are gratefully acknowledged. Additional gratitude is extended to G. Sevastopulo (Trinity College Dublin) and to M. Grigo (Institut für Geologie und Mineralogie der Universität zu Köln). I thank H. Cieszyński (Institut für Geologie und Mineralogie der Universität zu Köln) for preparing the SEM images. Support of the Deutsche Forschungsgemeinschaft (DFG projects HE 1610/16-1 and -2) is gratefully acknowledged.

Editor. Svend Stouge

Ancillary