Tube foot preservation in the Devonian crinoid Codiacrinus
from the Lower Devonian Hunsr€
uck Slate, Germany
WILLIAM I. AUSICH, CHRISTOPH BARTELS AND THOMAS W. KAMMER
Ausich, W.I., Bartels, C. & Kammer, T.W. 2013: Tube foot preservation in the
Devonian crinoid Codiacrinus from the Lower Devonian Hunsr€
uck Slate, Germany.
Lethaia, Vol. 46, pp. 416–420.
Fossilized tube feet are described on Codiacrinus schultzei Follmann from the Lower
Devonian Hunsr€
uck Slate of Germany. This is the first definitive proof of tube feet on
any fossil crinoid. Three lightly pyritized, flattened tube feet are preserved in a single
interray of this cladid crinoid. The tube feet were at least 7 mm long. Their preservation is very similar to the tube feet reported previously from a Hunsr€
uck ophiuroid,
except that the Codiacrinus tube feet have small papillae, similar to living crinoids. □ Echinodermata, Crinoidea, soft-tissue preservation, pyritization.
William I. Ausich [[email protected]], School of Earth Sciences, The Ohio State
University, 155 South Oval Mall Columbus 43210, OH, USA; Christoph Bartels [[email protected]], German Mining Museum, Am Bergbaumuseum 28,
Bochum D-44791, Germany; Thomas W. Kammer [[email protected]], Department of
Geology and Geography, West Virginia University, Morgantown 26506-6300, WV, USA;
manuscript received on 26/02/2012; manuscript accepted on 08/04/2013.
Preservation of soft tissue in fossil echinoderms is
exceedingly rare, and most reports of such preservation have been questioned or disproven. As discussed in Glass & Blake (2004), the Lower Devonian
Hunsr€
uck Slate (lower Emsian) of southwestern
Germany is the principal occurrence from which soft
tissues have been reported in fossil echinoderms.
Glass & Blake (2004) presented clear evidence of
pyritized tube feet in the Hunsr€
uck Slate ophiuroid
Bundenbachia beneckei St€
urtz 1886. Subsequently,
Glass (2006) reported pyritized tube feet in an Upper
Ordovician ophiuroid, Protasterina flexuosa (Miller
& Dyer 1878). The older Ordovician asteroid, Siluraster caractaci (Spencer 1916) was also interpreted to
have preserved tube feet (Gale 1987; fig. 7F). Herein,
we report the exquisite preservation of very well-preserved, pyritized tube feet on the crinoid Codiacrinus
schultzei Follmann 1887 from the Hunsr€
uck Slate.
This is the only confirmed occurrence of tube foot
preservation among the Crinoidea.
pure iron filings are used at low pressures (see discussions in Bartels et al. 1998; Glass & Blake 2004).
This method allows for very precise removal of
matrix with minimal or no damage to the fossil. The
specimen reported here was prepared by C.B. using
this technique and is deposited in the German Mining Museum, Bartels Collection (GMMBC HS 902).
The Hunsr€
uck Slate is an informal stratigraphical
term to include the Lower Devonian roofing slates
from the Rhenish Massif of Germany (Schindler
et al. 2002; Sutcliffe et al. 2002). The specimen in
question was collected from the Obereschenbach
Quarry at Bundenbach. It is from the Wingertshell
Member of the middle Kaub Formation (lower Emsian), which is near the top of the roofing slate outcrops at Bundenbach and close to a change from
muddy to more sandy sedimentary rocks.
Methods, materials and geological
setting
Verified examples of soft-tissue preservation are
exceedingly rare among fossil echinoderms. Glass &
Blake (2004), Glass (2006) and Kammer & Ausich
(2007) summarized various examples of reported
echinoderm soft-tissue preservation. Apart from
organic films, the only recognized soft-tissue preservation in crinoids is the uncalcified hind-gut of Tubulosocrinus (Kammer & Ausich 2007), potentially a
pyritized mid-gut and hind-gut within the calyx of
C. schultzei (S€
udkamp 2011, p. 252) and the tube
feet documented herein.
The discovery of tube feet by Glass & Blake (2004)
and Glass (2006) was possible with the use of new
preparation techniques developed during the early
1990s (Bartels et al. 1998). This technique uses an
air abrasive unit modified in the manner in which
powders are introduced and with pressure hoses that
limit static electricity. With this modified devise,
Tube feet preservation in crinoids
DOI 10.1111/let.12023 © 2013 The Authors, Lethaia © 2013 The Lethaia Foundation
LETHAIA 46 (2013)
Devonian crinoid tube feet
417
B
C
A
D
Fig. 1. Tube feet in Lower Devonian and living crinoids. A–C, Codiacrinus schultzei. A, crown with attached column, X1.0 (enhanced
with only low angle light); B, enlargement of crown, note the preserved tube feet in the inter-ray exposed on the right, X2.0 (enhanced
with only low angle light); C, enlargement of tube feet, X5.0 (enhanced with a light coating of ammonium chloride and low angle light);
D, tube feet on the living crinoid, Florometra serritissima (Clark 1907); Ambulacral (food) groove (A) of a pinnule lined on both sides by
alternating lappets (L) and podial triplets in ‘rest’ postures. Bar = 500 lm. 1, 2, 3, indicating longest to shortest of the tube feet in a single triplet (reproduced from Byrne & Fontaine 1983, With kind permission from Springer Science and Business Media).
418
Ausich et al.
Sprinkle (1973) reported tube feet on the enigmatic Cambrian organism Echmatocrinus brachiatus
Sprinkle 1973;. The structures considered to be tube
feet on this organism are surely examples of softbodied preservation. However, Echmatocrinus has
subsequently been reclassified as an octocoral (Ausich & Babcock 1998, 2000; but see Sprinkle & Collins
1998, 2011). As an octocoral, the ‘arms with tube
feet’ are actually pinnate tentacles, which occur on
living octocorals (Hyman 1940; Ausich & Babcock
1998, 2000).
In the Hunsr€
uck Slate, potential tube feet of
Dictenocrinus semipinnulatus (Schmidt 1934) (ne
Bathericrinus), Imitatocrinus gracilior (Roemer 1862)
and Macarocrinus semelfurcatus Schmidt 1934; were
illustrated by Schmidt (1934), Pl. 14, fig. 2a, b; Pl.
18, fig. 2; and Pl. 19, fig. 1). These reports were
reviewed by Otto (2000) who concluded that these
putative tube feet were calcite plates. We agree with
the assessment of Glass & Blake (2004, p. 76) that
the features discussed by Schmidt (1934) and Otto
(2000) are pinnules. In 1997, S€
udkamp (p. 238)
identified tube feet and interplate muscles on the
Hunsr€
uck Slate crinoid C. schultzei. As pointed out
by Glass & Blake (2004), as a cyathocrine cladid,
Codiacrinus lacked muscles (see discussion in Ausich
& Baumiller 1993, 1998), so the identified structures
could only be ligamentary tissue. However, Glass &
Blake (2004) interpreted these structures as silicification features rather than any type of preserved soft
tissue. Further, S€
udkamp (2011) reviewed evidence
for Codiacrinus tube feet (S€
udkamp 1997) and concluded that tube feet were not preserved in his specimen. However, as mentioned above, S€
udkamp
(2011) did interpret structures within a Codiacrinus
calyx as parts of the mid-gut and hind-gut, based on
X-ray images.
Herein, a single specimen of C. schultzei
(GMMBC HS 902) is reported with preserved tube
feet. This specimen is an incomplete, crushed crown
with an incomplete column approximately 150 mm
in height (Fig. 1A). The tube feet project into an
interradial area from primibrachials and, perhaps,
the proximal-most secundibrachials (Figs 1B, C, 2).
The best-preserved and longest tube foot is elongate, flattened and folds over onto itself (Fig. 1C).
The preserved portion would have been at least
7.0 mm if straight; and the maximum flattened
diameter is approximately 1.4 mm. Distally, the
tube foot tapers to a rounded tip. Each tube foot is
fragmented resulting in a ‘beaded’ appearance that
is identical to the Hunsr€
uck ophiuroid tube feet
illustrated by Glass & Blake (2004, fig. 2B). The
margins of the tube feet (Figs 2A, B) have small projections that correspond to the small papillae
LETHAIA 46 (2013)
reported on tube feet of living crinoids, such as Florometra serritissima (Clark 1907) (see Byrne & Fontaine 1983) (Fig. 1D). Two additional tube feet
presumably of the same approximate length are also
present, but these are not as well preserved
(Fig. 1C). Regardless, it is clear that each of these
additional long tube feet is also folded over onto
itself, indicating flexibility; and at least one of these
displays the remnants of papillae.
The only alternative interpretation for these tube
feet is that they could be preserved pinnules. This is
highly unlikely because, as noted above, Codiacrinus
is a cyathocrine cladid that lacks pinnules. Pinnules
are comprised of calcareous plates, which would
not fold over onto themselves and which are
A
B
Fig. 2. Hunsr€
uck tube feet, X7.5. A, enlargement of Fig. 1C; B,
interpretation of structures; br, brachials.
LETHAIA 46 (2013)
unknown to have the structures interpreted here as
papillae. Further, if Codiacrinus had pinnules, they
should be preserved elsewhere on the specimen and
on other specimens of this common Hunsr€
uck
crinoid.
A series of shorter and narrower structures projecting from the primibrachials but below the tube
feet occur on this specimen GMMBC HS902
(Fig. 1C). These smaller structures lack the ‘beaded’
texture of the longer crinoid and ophiuroid tube feet
(Glass & Blake 2004) and are present in a similar
position along other arms on this specimen. We
interpret these smaller structures as ambulacral
cover plates (S€
udkamp 1997, 2011) rather than preservation of any soft tissue, such as shorter tube feet.
Living crinoids have a triplet of tube feet preserved
associated with each lappet (cover plate) along the
arm (Fig. 1D). Each tube foot in this triplet is a different length and has a specialized function. Evidence of only the longer tube feet is preserved on
C. schultzei.
Specimen GMMBC HS 902 must have been rapidly buried in the fine-grained sediments of the
Hunsr€
uck Slate. This protected the specimen from
post-mortem disturbance and rapid decay of soft tissue to allow pyritization. The calcite plates of this
specimen range from not pyritized to slightly pyritized. Only a thin rind of pyritization preserves the
Codiacrinus tube feet. The method of pyritization
outlined in Briggs et al. (1996) is consistent with the
preservation of these tube feet. Flattening of the
Hunsr€
uck fossils was undoubtedly due to both
compaction of the shale and tectonic compression,
which yielded flattened tube feet and a flattened and
fragmented aboral cup (Bartels et al. 1998; K€
uhl
et al. 2012).
The proximal tube feet of C. schultzei were substantially longer (7.0 mm) than those reported for
F. serratissima (1.1 mm) by Byrne & Fontaine
(1983). More robust tube feet would be consistent
with the aerosol suspension feeding hypothesis for
crinoid feeding that predicts the relatively low
branching density of C. schultzei should have fed on
larger particles (Ausich 1980; Kammer 1985), most
likely zooplankton (Meyer 1979). The C. schultzei
tube feet are approximately the same length as the
ophiuroid tube feet reported by Glass & Blake
(2004).
Conclusions
Tube feet on the proximal arms of C. schultzei from
the Hunsr€
uck Slate of Germany are the first defini-
Devonian crinoid tube feet
419
tive proof of Palaeozoic crinoid tube feet. These
crinoid tube feet are of the same approximate size
and are preserved in a very similar manner to those
of the Hunsr€
uck ophiuroid B. beneckei reported by
Glass & Blake (2004). However, the Codiacrinus tube
feet also preserve fine-scale papillae, characteristic of
living crinoids.
Acknowledgements. – This research was supported by the
National Science Foundation who partially supported this work
(DEB 1036416 (WIA) and DEB 1036356 (TWK)). We thank M.
Byrne, the editors of Zoomorphology and Springer-Verlag for
permission to reproduce Figure 3D, herein; and A. Glass for help
with translations and for discussion on this article.
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