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Soft-bodied fossils from the upper Valongo Formation (Middle Ordovician: Dapingian-Darriwilian) of northern Portugal

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Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here, a new deposit preserving soft-bodied fossils is reported from the Middle Ordovician (Dapingian-Darriwilian) upper Valongo Formation of northern Portugal. The deposit contains the first known occurrences of soft-bodied fossils from the Middle Ordovician (Dapingian-Darriwilian) of Portugal and is the first Ordovician example of soft-tissue preservation involving carbonaceous films from the Iberian Peninsula. It also represents the lone deposit of soft-bodied fossils from the Middle Ordovician of northern Gondwana. Thus temporally, it lies between the exceptional deposits of the Lower Ordovician of Fezouata (Morocco) and the Upper Ordovician of the Soom Shale (South Africa); it also serves as a biogeographic link between these and the various Ordovician soft-bodied deposits in Laurentia. The soft-bodied fossils come from the deep-water slates of the upper part of the Valongo Formation and include a discoidal fossil questionably referable to Patanacta, wiwaxiid sclerites, and a possible pseudoarctolepid arthropod.
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ORIGINAL PAPER
Soft-bodied fossils from the upper Valongo Formation (Middle
Ordovician: Dapingian-Darriwilian) of northern Portugal
Julien Kimmig
1
&Helena Couto
2
&Wade W. Leibach
1
&Bruce S. Lieberman
1,3
Received: 3 December 2018 /Revised: 20 April 2019 /Accepted: 9 May 2019
#Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Soft-bodied preservation is common in the Cambrian but comparatively rare in the Ordovician. Here, a new deposit preserving
soft-bodied fossils is reported from the Middle Ordovician (Dapingian-Darriwilian) upper Valongo Formation of northern
Portugal. The deposit contains the first known occurrences of soft-bodied fossils from the Middle Ordovician (Dapingian-
Darriwilian) of Portugal and is the first Ordovician example of soft-tissue preservation involving carbonaceous films from the
Iberian Peninsula. It also represents the lone deposit of soft-bodied fossils from the Middle Ordovician of northern Gondwana.
Thus temporally, it lies between the exceptional deposits of the Lower Ordovician of Fezouata (Morocco) and the Upper
Ordovician of the Soom Shale (South Africa); it also serves as a biogeographic link between these and the various Ordovician
soft-bodied deposits in Laurentia. The soft-bodied fossils come from the deep-water slates of the upper part of the Valongo
Formation and include a discoidal fossil questionably referable to Patanacta, wiwaxiid sclerites, and a possible pseudoarctolepid
arthropod.
Keywords Soft-tissue preservation .Discoidal fossils .Wiwaxia .Bivalved arthropod .Ordovician .Portugal
Introduction
Deposits preserving soft-bodied fossils are critical for under-
standing the diversity and origins of early animals, as they
preserve organisms that are prone to decay and would usually
not be preserved in the fossil record (e.g., Butterfield 1990;
Schiffbauer et al. 2014; Muscente et al. 2017; Daley et al.
2018). These deposits are most common in Cambrian Series
2 and 3 (Conway Morris 1989;Gaines2014; Robison et al.
2015;Kimmigetal.2019), and their record declines
subsequently (e.g., Lerosey-Aubril et al. 2018), with only a
few deposits known from the Ordovician (Allison and Briggs
1993; Butterfield 1995; Gaines 2014;VanRoyetal.2015;
Briggs et al. 2018). The most diverse Ordovician Burgess
Shale type (BST) deposit known to date is the Lower
Ordovician Fezouta biota of Morocco (Van Roy et al. 2010,
2015; Martin et al. 2016). Other deposits preserving soft-
tissue remains include the Lower Ordovician Afon Gam
Biota of Wales (Botting et al. 2015); the Middle Ordovician
Winneshiek Lagerstätte of Iowa (Liu et al. 2006,2009;Briggs
Communicated by: Matthias Waltert
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00114-019-1623-z) contains supplementary
material, which is available to authorized users.
*Julien Kimmig
jkimmig@ku.edu
Helena Couto
hcouto@fc.up.pt
Wade W. Leibach
wade.leibach@ku.edu
Bruce S. Lieberman
blieber@ku.edu
1
Biodiversity Institute, University of Kansas, Lawrence, KS 66045,
USA
2
Department of Geosciences, Environment and Spatial Planning/ICT,
University of Porto, Faculty of Sciences, Rua do Campo Alegre 687,
4169-007 Porto, Portugal
3
Department of Ecology and Evolutionary Biology, University of
Kansas, Lawrence, KS 66045, USA
The Science of Nature (2019) 106:27
https://doi.org/10.1007/s00114-019-1623-z
et al. 2018) and Llanfallteg Formation in Wales (Hearing et al.
2016); and the Upper Ordovician Beechers Trilobite Bed of
New York (Briggs et al. 1991), Big Hill Formation of
Michigan (Lamsdell et al. 2017), Martinsburg Formation of
Pennsylvania (Meyer et al. 2018), BUpper Ordovician
Lagerstätten^from Manitoba, Canada (Young et al. 2007,
2012), Bardahessiagh Formation of Ireland (MacGabhann
and Murray 2010), and Soom Shale of South Africa
(Aldridge et al. 1994;Gabbott1998). The information pre-
served in these Ordovician exceptional deposits has greatly
improved knowledge on the expansion of biodiversity during
the Great Ordovician Biodiversification Event (GOBE)
(Webby et al. 2004; Servais and Harper 2018). These deposits
have also revealed that several clades of soft-bodied taxa once
thought to have gone entirely extinct during the Cambrian in
fact survived into the Ordovician (e.g., Van Roy et al. 2010;
Botting et al. 2015; Hearing et al. 2016).
Here, we report on the first Middle Ordovician (Dapingian-
Darriwilian) soft-bodied fossils from northern Gondwana.
They are preserved in the upper Valongo Formation of north-
ern Portugal (Fig. 1), which is famous for its trilobite diversity
(Delgado 1908; Romano and Diggens 1974; Romano 1991),
as well as diverse nautiloids, gastropods, and echinoderms
(Delgado 1908; Couto et al. 1997;Ausichetal.2007; Couto
2013). The soft-bodied fossils comprise a discoidal fossil,
possible wiwaxiid sclerites, and an arthropod carapace.
Soft-tissue preservation, and especially BST preservation,
is well documented in deposits of Cambrian age (Conway
Morris 1989; Allison and Briggs 1993; Butterfield 1995;Orr
et al. 1998;BriggsandFortey2005;Gaines2014), but there
are far fewer deposits known from the Ordovician (Van Roy
et al. 2015; Muscente et al. 2017). This is partially due to
alterationof ocean pH and Eh; oxygenation of upper sediment
layers by increasing and deeper bioturbation; and major ero-
sional and facies differences related to global tectonics, which
altered chemical availability for cement formation and
changed ocean shelf areas (Gaines et al. 2012a,b;Daley
et al. 2018). Another reason for the sparse preservation of
these organisms is their delicate nature and their tendency to
decompose before preservation. In most early Paleozoic cases,
these organisms are preserved as two-dimensional carbon or
aluminosilicate films in carbonaceous shales (Gaines 2014;
Muscente et al. 2017). The best-known Ordovician deposits
with soft-tissue preservation in a plethora of taxa are the
Lower Ordovician Fezouta Lagerstätte in Morocco (Van
Roy et al. 2015;Martinetal.2016) and the Upper
Ordovician Soom Shale of South Africa (Gabbott 1998;
Gabbott et al. 2017). These two Lagerstätten allow snapshots
Fig. 1 aGeological map of the Valongo Anticline area, northern
Portugal, showing the locations of study specimens, indicated by the
stars (S. Pedro da Cova, 41° 9N, 8° 29W; Belói 41° 8N, 8° 29W)
(modified from Couto et al. 2013). A, Cambrian: SJF, Santa Justa
Formation; VF, Valongo Formation; SF, Sobrido Formation; B, Silurian
to Carboniferous. bGeneralized lithostratigraphic column of the
Paleozoic succession in the study area: 1, quartzites; 2, slates; 3,
diamictites; 4, slates and siltstones; 5, conglomerates; 6, acidic volcanics;
7, basic volcanics (modified from Couto and Roger 2017)
27 Page 2 of 13 Sci Nat (2019) 106:27
into the biodiversity of the Ordovician and show the changes
that happen during this period. The Fezouata Lagerstätte has
yielded several clades of typical Cambrian taxa (i.e.,
radiodonts, and marellomorphs) together with typical mem-
bers of later Paleozoic faunas (Van Roy et al. 2015). The
Soom Shale in contrast is dominated by typical Paleozoic
animals (i.e., conodonts, orthoconic nautiloids, brachiopods)
and has few survivors of the Cambrian radiation (Gabbott
et al. 2017).
Some of the most common soft-bodied fossils in the
Ordovician are discoidal fossils. They have been described
from the deposits of Ordovician age (Fig. 2and Suppl. 2)that
otherwise contain minimal to no other instances of soft-tissue
preservation, including New York State (Discophyllum
peltatum Hall 1847), Sweden (Patanacta pedina Cherns
1994), Ireland (Septus pomeroii MacGabhann and Murray
2010), and Morocco (D. peltatum;BEldonia^). The Valongo
Formation of northern Portugal preserves a diverse well-
skeletonized fauna (Delgado 1908;Coutoetal.1997;
Ausich et al. 2007; Couto 2013), but the herein described
associated soft-bodied fauna is sparse and usually poorly pre-
served. The only previously described soft-bodied fossil from
the Lower Ordovician of Portugal is a discoidal fossil referred
to as Discophyllum plicatum Hall 1847 by Delgado (1892)
from the slightly older Armoricain Quartzite Formation of
Buçaco (Central Portugal), which is coeval with the Santa
O
r
d
o
v
i
c
i
a
n
Hirnatian
Katian
Sandbian
453.0 ± 0.7
445.2 ± 1.4
443.8 ± 1.5
458.4 ± 0.9
467.3 ± 1.1
470.0 ± 1.4
477.7 ± 1.4
485.4 ± 1.9
Darriwilian
Dapingian
Floian
Tremadocian
Early
Middle
Late
Armoricain Quartzite Formation [France, Portugal]
Trenton Group [USA - New York]
Tafilalt Biota [Morocco]
Upper Tiouririne Formation [Morocco]
Stony Mountain Formation, Williams Member [Canada - Manitoba]
Big Hill Formation [USA - Michigan]
Tamadjert Formation [Algeria]
Grindstone Range Sandstone [Australia]
Dol-cyn-Afon Formation [Wales]
Valongo Formation [Portugal]
Bardahessiagh Formation [Ireland]
Unidentified lime and mudstones [Sweden]
Šárka Formation [Czech Republic]
Floresta Formation [Argentina]
Letná Formation [Czech Republic]
Fenxiang Formation [China]
Fezouata Formation [Morocco]
St. Peter Formation [USA - Iowa]
Llanfallteg Formation [Wales]
Martinsburg Formation [USA - Pennsylvania]
Red River Formation, Cat Head Member [Canada - Manitoba]
Churchill River Group? [Canada - Manitoba]
Lorraine Group [USA - New York]
Soom Shale [South Africa]
Fig. 2 Stratigraphic chart showing the occurrences of soft-bodied fossils in the Ordovician. Deposits with soft-bodieddiscoidal fossils are shown in bold
Sci Nat (2019) 106:27 Page 3 of 13 27
Justa Formation from the Valongo Anticline (Tremadocian-
Floian, the fossils are from the Floian interval), but the spec-
imen is currently reported missing.
Geological setting
The deposit described herein is located near the village of
S. Pedro da Cova, in northern Portugal. Placed in the
Central-Iberian Zone, it is part of the Valongo Anticline,
a major ante-Stephanian asymmetrical antiform anticline
trending NW-SE, whose axis plunges 5° to 15 ° to the
NW, with an axial plane 60° to the NE (Ribeiro et al.
1987). The anticline is surrounded by Variscan granites
(Fig. 1a). Lower Paleozoic metasediments in this region
rangeinagefromCambriantoDevonian(Fig.1b), and
at this locality, the Cambrian is represented by the
Montalto Formation which consists of interbedded slates,
quartzites, polygenic conglomerates, and volcanics (Couto
1993). Three Ordovician formations were defined by
Romano and Diggens (1974), later revised by Couto
(2013) and Couto et al. (2013). These are, in ascending
order, (1) the Santa Justa Formation (Tremadocian-
Floian), which is formed by volcanic rocks
(Tremadocian) and platform deposits, which lie below in-
terbedded fine-grained and coarse-grained clastic sedi-
ments and volcano-sedimentary layers, indicating subsid-
ing and tectonically unstable sedimentation conditions; (2)
the Valongo Formation (Dapingian-Darriwilian), which is
formed by fine-grained clastic sediments deposited in shal-
low to deep-water environments; and (3) the Sobrido
Formation (Hirnantian), which contains glacially influ-
enced marine rocks deposited on the north Gondwana
platform.
The Valongo Formation varies locally from 300 to 400 m
thick and consists of a succession of slightly metamorphosed
(greenschist facies) slates and siltstones (Fig. 1b). The base is
formed by fossiliferous pink siltstones, followed by dark gray
siltstones probably of Dapingian age. Gray siltstones and dark
gray fossiliferous shales of Dapingian-Darriwilian age overlay
these strata. These shales are gradually replaced by slates,
which host the soft-bodied fauna. These in turn are overlain
by fossiliferous light gray siltstones (Romano and Diggens
1974;Couto1993). Petrographic study of these
metasediments showed that they are mainly comprised of
chlorite and muscovite (Couto 1993). The exact beds that
preserve the soft-bodied fossils are uncertain, as all soft-
bodied fossils have been collected from the scree, but the
lithology corresponds to the slates in the upper part of the
Valo n go For mati on.
Fossils The Valongo Formation is one of the most fossiliferous
units in Portugal and comprises a diverse biota of benthic and
pelagic animals. In addition to the putative Patanacta,
wiwaxiid sclerites, and bivalved arthropod, the fauna includes
over 150 different species of trilobites, graptolites, brachio-
pods, gastropods, bivalves, cephalopods, echinoderms, and
several groups of uncertain affinity (Delgado 1892,1897,
1908; Thadeu 1949;Curtis1961;Romano1975,1976,
1980,1982a,b,1990,1991; Romano and Diggens 1974;
Romano and Henry 1982; Rábano 1989; Tauber and Reis
1994; Couto et al. 1997; Couto and Gutiérrez-Marco 1999,
2000; Ausich et al. 2007; Couto 2013). The assemblage is
dominated by taxa characteristic of Ordovician communities,
particularly trilobites and molluscs. The most common trilo-
bites in the Valongo Formation are Actinopeltis (Valongia)
wattisoni,Colpocoryphe rouaulti,Dionide mareki,
Eccoptochile almadenensis,Prionocheilus mendax,
Ectillaenus giganteus,Eodalmanitina macrophtalma,
Eodalmanitina destombesi,Eoharpes cristatus,Isabelinia
glabrata,Neseuretus tristani,Nobiliasaphus nobilis,
Nobiliasaphus hammanni,Parabarrandia crassa,
Phacopidina sp., Placoparia tournemini,Placoparia
(Coplacoparia) borni,Protolloydolithus sp., Salterocoryphe
salteri,Selenopeltis gallica,Uralichas hispanicus,
Zeliszkella toledana,andZeliszkella torrubiae (Delgado
1908;Romano1976; Couto et al. 1997). Among mollusk taxa
in the upper Valongo Formation, the most common are
Cameroceras sp., Cardiolaria beirensis,Clathrospira sp.,
Hemiprionodonta lusitanica,Praenucula costae,Redonia
deshayesi,Sinuites sp., Trocholites fugax, and various
orthoceratids as well as rostroconchs (Babin et al. 1996;
Couto and Gutiérrez-Marco 2000). Other taxa in the deposit
are hyolithids, machaeridians (Plumulites sp.), ostracods,
echinoderms such as Mitrocystella incipiens miloni, and rare
graptolites referable to Orthograptus calcaratus (Delgado
1908; Babin et al. 1996;Coutoetal.1997;Coutoand
Gutiérrez-Marco 2000; Gutiérrez-Marco et al. 2000). In addi-
tion to the body-fossil record, a diverse ichnofossil record is
present in the Valongo Formation, including burrows and
microbially mediated traces (Neto de Carvalho et al. 2016).
Depositional environment The sedimentary rocks of the
Lower Ordovician of the study area (Fig. 1)weredeposited
in a shallow sea that formed due to rifting related to the open-
ing of the Rheic Ocean (Couto et al. 2014). The facies hosting
the soft-bodied (and biomineralized) fossils in the upper
Valongo Formation is comparable to those known from
Cambrian deep-water deposits containing BST fossils
(Powell et al. 2003; Gabbott et al. 2008; Kimmig and Pratt
2016), as they are mostly comprised of aluminosilicates, chlo-
rite and occasionally muscovite, and quartz (Couto 1993). In
contrast to some other BST deposits, which are interpreted as
having been deposited under oxic conditions (Powell et al.
2003; McKirdy et al. 2011;KimmigandPratt2016;
Sperling et al. 2018), the bottom waters of the Valongo
27 Page 4 of 13 Sci Nat (2019) 106:27
Formation have been interpreted as at least temporarily
dysoxic to anoxic based on ichnological information (Neto
de Carvalho et al. 2016).
The depositional environment of the Valongo Formation
appears to have been a relatively low energy setting, as there
are no indications of ripples. The biota also supports this, as
there are no putatively photosynthetic organisms preserved.
The soft-bodied fossils were likely not transported very far,
as the discoidal fossil and the wiwaxiids do not have any
apparent damage.
Material and methods
The fossil specimens are housed in the collection of the
Faculty of Sciences of the University of Porto, Department
of Geosciences, Environment and Spatial Planning, Portugal
(FCUP/DGAOT).
Elemental mapping utilizing energy-dispersive X-ray spec-
troscopy (EDS) was conducted at the University of Kansas
Microscopy and Analytical Imaging Laboratory using an
Oxford Instruments 80 mm
2
x-Max silicon drift detector
(SDD), mounted on an FEI Versa 3D Dual Beam. Analyses
used a horizontal field width of 2.39 mm, a kilovolt of 10, a
spot size of 4.5, and a 1000-μm opening (no aperture). EDS
maps were collected at a pixel resolution of 512 × 512 with a
total of 18 passes.
The fossils were photographed using a Canon EOS 5D
Mark II digital SLR camera with a 50-mm Canon macro lens.
The soft-bodied fossils (FCUP/DGAOT 3SPC and FCUP/
DGAOT 5SPC) were photographed submerged in alcohol.
The contrast, color, and brightness of the images were adjust-
ed in Adobe Photoshop.
Results
Systematic palaeontology
Cnidaria Verrill, 1865
Medusozoa Petersen, 1979
Patanacta Cherns, 1994
Type species.P. pedina
Diagnosis. Ovoid to circular disc, weakly concavo-convex
and with entire and distinct margin; convex and concave sur-
faces correspond closely. Circular central area, beyond which
coarse, shallow, radial ridges originate and traverse to reach
the margin, intersected by perpendicular, evenly spaced ridges
(amended from Cherns 1994).
Patanacta? sp. indet. (Fig. 3ae)
Material. Onespecimenindorsoventralview
(FCUP/DGAOT 3SPC)
Occurrence. Middle Ordovician slates of the upper part of
the Valongo Formation, near S. Pedro da Cova, northern
Portugal
Description. Ellipsoidal in outline. 59.8 mm long and
49.4 mm wide. Central circular area 5.7 mm in diameter, with
ridges radiating out toward the edge of the specimen. At least
15 ridges, consistently about 3.1 mm wide and between 19.9
and 31.3 mm long. The ridges are straight and have no signs of
branching. Margin mostly smooth, though slightly scalloped
where the ridges are shorter (Fig. 3d).
Remarks. The specimen is questionably attributed to
Patanacta, based on the circular central area, the radiating
ridges, and the absent concentric rings. The smooth, uniform
appearing edge of the fossil is likely due to compression or
other taphonomic factors, it is not the same width throughout
the specimen. The specimen seems to be preserved at
somewhat of an angle to a dorsoventral plane, as the ridges
vary in length between 19.9 and 31.3 mm. Patanacta was first
described by Cherns (1994) from the Upper Ordovician-
Silurian of Sweden. The Swedish specimen is preserved as a
shiny, inorganic, and possibly silicate film (Cherns 1994),
resembling in general the style of preservation of the
Portuguese specimen. The Swedish specimen preserves 22
24 ridges, but the specimen from the Valongo Formation only
preserves 15 complete ridges (Fig. 3a, b). This difference
could be due to taphonomic factors, including compression,
ontogenetic variation, or it could represent intra- or interge-
neric variation. Given that this is the single known specimen,
it is not assigned to species level.
Another Ordovician discoidal genus that shares features with
the Portuguese specimen is Rutgersella Johnson and Fox, 1968
from the Australian Grindstone Range; it is preserved as three-
dimensional external molds (Rettalack 2009). The specimens are
elliptical in outline and preserve curving outward ribs and a
central ellipsoidal depression (Rettalack 2009). Patanacta? illus-
trated herein, however, does not have curving outward ribs, and
the center appears to be circular not elliptical.Additionally, there
is controversy regarding Rutgersella as it has been considered a
pseudofossil by Cloud (1973), although Rettalack (2009,2015)
argued that new fossils recovered from the Grindstone Range
Sandstone in southern Australia support a biogenic origin. By
contrast, in a review of the Dawson Hill Member of the
Grindstone Range Sandstone Jago et al. (2010) argued that most,
if not all, of the fossils described by Retallack (2009) are of
inorganic origin.
Patanacta? from the Valongo Formation also differs from
Ordovician and Cambrian representatives of Discophyllum
Hall 1847 (see MacGabhann 2012; Lieberman et al. 2017)
or the Ordovician Septus (MacGabhann and Murray 2010),
as it lacks concentric rings, although this difference could be
taphonomic (Briggs 2003; Kimmig and Pratt 2016).
The specimen does not appear to be a coprolite as these,
when recovered from BST deposits, usually preserve carbon
Sci Nat (2019) 106:27 Page 5 of 13 27
flakes or skeletal material (Vannier and Chen 2005; Kimmig
and Strotz 2017; Kimmig and Pratt 2018), yet these are absent
in Patanacta? Further, no radiating structures have been ob-
served in coprolites.
Finally, the specimen does not appear to be a radiodontan
oral cone of the type discussed in Pates et al. (2018) as the size
of the central circular area is relatively far too small to repre-
sent the central opening of anoral cone, there is no evidence of
possible marginal teeth/spines protruding into that central cir-
cular area, as would be expected if it was the central opening
of an oral cone, and the radiating ridges do not show the
linearity that would be expected if they represented the mar-
gins of plates of a radiodontan oral cone.
Lophotrochozoa Halanych et al., 1995
Wiwaxiidae? Walcott, 1911 (Fig. 4a)
Material. Two specimens (FCUP/DGAOT 5SPC) pre-
served in lateral view on one slab
Diagnosis. (See Conway Morris 1985)
Occurrence. Middle Ordovician slates of the upper part of
the Valongo Formation, near S. Pedro da Cova, northern
Portugal
Description. Twoisolatedrecurvedsclerites.Thefirstone
is 28 mm long and 2.4 mm wide in the center. The second is
23 mm long and missing both ends; it is 3.1 mm wide in the
center. Both sclerites are thickest in the center and pinch out
toward the ends. The more complete specimen is slimmer at
one end than the other.
Remarks. The sclerites are tentatively attributed to
Wiwaxiidae based on similarities to Wiwaxia corrugata from
the Burgess Shale (see Fig. 145 in Conway Morris 1985)and
Wiwaxi a herka (see Conway Morris et al. 2015;Kimmigetal.
2019) from the Spence Shale (Fig. 4b). The assignment is,
however, tentative because no microstructures are preserved.
If indeed wiwaxiids, they likely represent ventro-lateral scler-
ites, based on their recurved shape. The sclerites would extend
the range of the group into the Middle Ordovician; wiwaxiids
Fig. 4 aWiwaxiid? sclerites from the upper part of the Valongo
Formation in lateral view (FCUP/DGAOT 5SPC). bVentro-lateral
sclerite of Wiwaxia herka from the Cambrian Spence Shale of Utah in
lateral view, collected by the Gunther Family (KUMIP 286302; see
Conway Morris et al. 2015). Scale bars are 5 mm
Fig. 3 Patanacta? sp. indet. (FCUP/DGAOT 3SPC) from the upper part
of the Valongo Formation of northern Portugal. aDorsal view of the
specimen. bLine drawing illustrating the preserved structures in a.ce
Close-ups of different parts of the specimen. cThe center of the specimen,
showing the circular central area and ridges connected to it. dThe center
bottom of the specimen, showing the edge of the fossil and ridges. eThe
top left of the specimen, showing the edge of the fossil and possible
ridges. Scale bars are 5 mm
27 Page 6 of 13 Sci Nat (2019) 106:27
have also been reported from the early Ordovician Fezouata
biota (Van Roy et al. 2015).
Arthropoda von Siebold 1848
Pseudoarctolepidae? Brooks and Caster 1956 (Fig. 5a, b)
Material. One specimen in lateral view (FCUP/DGAOT
20BE)
Diagnosis. (See Brooks and Caster 1956)
Occurrence. Middle Ordovician slates of the upper part of
the Valongo Formation, near Belói, northern Portugal.
Description. Two valves partly overlying each other. Hinge
line approximately straight. Total valve length 49.4 mm.
Prominent ventral process 18.8 mm long, projecting from
ventral margin well anterior of midline, weakly curved, with
concave margin posteriorly, thinning slightly ventrally to end
in weakly rounded point. Prominent posterior process
27.3 mm, only weakly thinning posteriorly; no anterior pro-
cess preserved. Valve 14.1 mm at widest point (excluding
ventral process).
Remarks. The specimen is strongly weathered, especially
the valve that is displaced anteriorly and also weakly declined
ventrally and slightly rotated counterclockwise. The valves
preserve no or possibly weak, millimeter-sized trapezoid, or-
namentation, and only the margins are well preserved. Valves
appear to have been separated along the putative hinge line
before burial, as the two valves are offset (Fig. 5a, b), with the
posterior process only visible in theoverlying valve. The spec-
imen is tentatively assigned to the Pseudoarctolepidae Brooks
and Caster 1956, as it shares with members of that family the
shape of the valves and the prominent ventral process, which
seems to originate at the same position of the valve. Further,
the ventral processes bear roughly the same shape as those in
Pseudoarctolepis sharpi Brooks and Caster 1956 (Fig. 5c, d).
The shape of the posterior process is also reminiscent of what
is known for the family, although it seems somewhat larger
and more prominent than what is known in P. sharpi. All
previously identified representatives of the family are from
the Cambrian (e.g., Brooks and Caster 1956; Robison and
Richards 1981;Yuanetal.2011), so this would constitute a
range extension for the group. The specimen does differ from
typical Cambrian specimens of the family in not having the
two valves joined along the hingeline. However, this may be
analogous to the situation in phyllocarid crustaceans (e.g.,
Rode and Lieberman 2002; Briggs et al. 2004), or the
Cambrian carapaced arthropod? Perspicaris dilatus
(Kimmig and Pratt 2015), where some species are typically
preserved with the two valves joined, yet others are represent-
ed by individual valves. Notably, the specimen differs from
phyllocarid crustaceans in the presence of the prominent ven-
tral process.
The prominent posterior process could also indicate a pos-
sible affinity to the bivalved arthropod Isoxys, but this genus
usually does not preserve a ventral process (García-Bellido
et al. 2009; Kimmig and Pratt 2015).
Another possible affinity might be the marrellid Furca
(e.g., Van Roy et al. 2010;Legg2016), which is known from
deposits relatively close in space and time to the Valongo
Formation. In this case, the fossil would either represent two
Fig. 5 aPseudoarctolepid? arthropod valves from the upper part of the
Valongo Formation in lateral view (FCUP/DGAOT 20BE), posterior end
of right valve showing possible dorsoventral compression. bLine
drawing illustrating the preserved structures in a.cButterflied valves of
Pseudoarctolepis sharpi from the Cambrian Wheeler Formation of the
Wheeler Amphitheater in the House Range of Western Utah, collected by
Robert Harris (KUMIP 153913). Scale bars are 5 mm
Sci Nat (2019) 106:27 Page 7 of 13 27
very poorly preserved specimens, or one fractured specimen.
In this case, what has been interpreted as the ventral process
would instead be the projection coming off of the righthand
side and center of a Furca carapace, and the interpreted pos-
terior process would be the process coming off of the
righthand side and posterior of the carapace.
A final possible affinity might be an arthropod appendage
with a spine on each podomere.
Preservation
EDX analysis of Patanacta? and the wiwaxiid sclerites
(Suppl. 3and 4) identified carbon throughout but no consis-
tent film, likely due to the metamorphic alteration of the rock
and possibly to weathering on the scree slope (note a similar
preservational style regarding carbon was found in Cambrian
Discophyllum by Lieberman et al. 2017). While the sclerites
are visually different, the elemental composition does not sig-
nificantly differ from Patanacta? No sulfur was detected in
the rock, suggesting that pyrite is not playing a role in medi-
ating preservation. In addition to carbon, the bulk mineralogy
of the specimens was determined to comprise aluminosilicates
(SiAlO or SiFeAlO), likely muscovite (Kal
2
AlSi
3
O
10
(OH)
2
)
and/or chlorite ((Mg, Fe, Al)
6
(Al, Si)
4
O10(OH)
8
); examina-
tion via petrographic microscope revealed these were dis-
persed across the surrounding rock and the fossil. Spectral
maps of Patanacta?(Suppl.3) indicated the following varia-
tions in percentage by weight for different detectable ele-
ments: O, 40.247.1%; Si, 15.822.1%; Al, 14.816.3%; C
4.113.8%; Fe, 4.410.3%; K, 2.84.2%; Na, 0.70.9%; Mg,
0.40.6%; Ti, 00.8%; and P 00.3%. Although the
Patanacta? specimen was found in scree, it appears that the
elemental signature is primary. The fossil has an enhanced
signature of carbon (from 6.7 at the edge to 13.8% near the
center of the fossil) relative to the matrix (4.14.8%). Al, Si,
O, Na, Mg, P, and Ti were found to be close to identical in the
fossil and the surrounding matrix. It appears unlikely that the
fossils are of inorganic nature, as no S was present in detect-
able levels during the EDX analysis, confirming that the fos-
sils are no pyrite residue. Iron is slightly more prominent in the
matrix (9.410.3%) than in the fossil (4.46.2%) of FCUP/
DGAOT 3SPC, again arguing against a prominent role for
pyrite in soft-bodied preservation.
In total, the EDX data indicate the specimens are originally
preserved via carbonaceous films and aluminosilicate replace-
ment, broken up by weathering and low temperature meta-
morphism. Scanning electron microscopy of the soft-bodied
fossils revealed no pyrite framboids in the fossil or the sur-
rounding matrix, but pyrite framboids can occur in some slate
layers. There is no indication of phosphatisation in any of the
soft-bodied or biomineralized fossils. The low temperature
metamorphism (epizone) that overprinted the rocks (Couto
1993) might have altered part of the mineralogical composi-
tion of the host-rock and the fossils, but still the soft-bodied
preservation in the upper Valongo Formation appears to have
followed the standard path of BST preservation (Butterfield
1995; Orr et al. 1998; Cai et al. 2012;Gaines2014).
Discussion
The upper Valongo Formation preserves relatively few taxa of
soft-bodied fossils compared to many of the other Ordovician
soft-body deposits (Fig. 2and Suppl. 1), but itstill addsto our
knowledge of soft-bodied fossils as it represents the only de-
posit preserving such fossils of DapingianDarriwilian age
from Gondwana, filling the gap between the Tremadocian
Floian Fezouata biota and the Sandbian fossils of the Tafilalt
Biota (MacGabhann 2012; Gutiérrez-Marco and García-
Bellido 2015; Van Roy et al. 2015). In addition, the upper part
of the Valongo Formation represents one of the few deeper-
water BST deposits in the Ordovician; finally, it is the first
deposit preserving soft-bodied fossils from the Ordovician of
the Iberian Peninsula.
In regard to the fossils, the best-preserved specimen is the
discoidal fossils referred to Patanacta?. Discoidal fossils
comprise an enigmatic, probably polyphyletic assemblage of
organisms known from the late Neoproterozoic and through-
out much of the Phanerozoic (Cartwright et al. 2007). They
have been referred to many phyla including Cnidaria,
Mollusca, and Echinodermata. One of the challenges of study-
ing discoidal fossils is determining whether or not they are
truly biogenic, a topic discussed in detail in Hofmann et al.
(1991), Gehling et al. (2000), Ruiz et al. (2004), MacGabhann
(2007), Kirkland et al. (2016), and Lieberman et al. (2017).
Focusing on examples that appear to represent bona fide or-
ganic remains, soft-bodied discoidal fossils are particularly
well known from the Ediacaran (Glaessner 1971;Fedonkin
1981; Sun 1986; Gehling et al. 2000; MacGabhann 2007;
Tarhan et al. 2015; Lieberman et al. 2017). They are also
known from the Phanerozoic as well, especially from the
Cambrian (Masiak and Zylinska 1994; Waggoner and
Collins 1995; Landing and Narbonne 1992; Hagadorn et al.
2002; Zhu et al. 2002; Van Roy 2006a,b;Cartwrightetal.
2007; Young and Hagadorn 2010; Sappenfield et al. 2017),
with fewer localities preserving these fossils known from the
Ordovician (e.g., Ruedemann 1916; Yochelson 1984; Cherns
1994; MacGabhann and Murray 2010; Botting et al. 2015;
Fig. 2a and Suppl. 1) and later time periods (e.g., Ossian
1973; Stanley and Kanie 1985;Kirklandetal.2016).
Cherns (1994)consideredP. pedina to be a medusoid of
uncertain affinities, based on its concentric center, which she
treated as the stomach, and its radial ridges, which could be
part of the gastrovascular system. An interpretation as a
medusozoan is not unreasonable, though currently there is
27 Page 8 of 13 Sci Nat (2019) 106:27
much debate about the interpretation of discoidal fossils and
their taxonomic affinities (Cartwright et al. 2007;
MacGabhann 2007; Young and Hagadorn 2010; Botting
et al. 2015;Tarhanetal.2015; Kirkland et al. 2016;
Lieberman et al. 2017; Landing et al. 2018). The absence of
concentric rings in Patanacta was treated by Cherns (1994)as
either reflecting taphonomic factors or the absence of actual
biological structures. Notably, these are again absent in the
specimen described herein, perhaps suggesting that this might
not be a taphonomic feature. Other Ordovician discoidal fos-
sils have been attributed to Medusozoa (Young et al. 2007,
2012;Lamsdelletal.2017).
An alternative affinity for Patanacta would be as an
eldoniid, although a diagnostic coiled sac is not visible.
Eldoniids are discoidal soft-bodied fossils thought to represent
stem group deuterostomes (Caron et al. 2010;MacGabhann
2012; Kimmig et al. 2018). Once thought to be limited to the
Cambrian, now specimens from other periods have been re-
ported (Alessandrello and Bracchi 2003;MacGabhann2007,
2012). The eldoniids are characterized by branching radial
ridges and a coiled sac (Alessandrello and Bracchi 2003;
MacGabhann 2007,2012); many specimens also preserve
concentric rings, especially if Discophyllum is considered to
be an eldoniid (see discussion in Lieberman et al. 2017). In the
last two decades, several eldoniids have been described from
the Ordovician, and they now appear to comprise the most
common soft-bodied discoidal fossils from this time period
(Table 1; Alessandrello and Bracchi 2003;MacGabhann
2012; Gutiérrez-Marco and García-Bellido 2015).
MacGabhann (2012) in particular argued that specimens of
Discophyllum (and other discoidal forms that resemble this
genus such as Paropsonema) from the Ordovician and other
time periods were likely to represent eldoniids. However,
there still is active debate about whether these taxa might
comprise eldoniids or instead porpitids (Lieberman et al.
2017; Landing et al. 2018). Discophyllum has also been re-
ported from the Cambrian of California (Lieberman et al.
2017), the Ordovician of Morocco (MacGabhann 2012), the
Ordovician of Portugal (Delgado 1892), the Ordovician of
France (Phillips and Slater 1848; Barrois 1891), and the
Silurian of England (Fryer and Stanley 2004). If all these
specimens actually belong to Discophyllum, the genus is long
lived and likely had a worldwide distribution. At this time,
based on the available evidence in the literature and the new
specimen presented herein, we build on Cherns(1994)inter-
pretation and suggest Pantanacta is likely a medusozoan of
some kind, though the precise class, i.e., hydrozoan or scy-
phozoan (there is no evidence for cubozoan affinity), is inde-
terminate. More, better preserved specimens are needed to
verify and constrain its taxonomic affinities. Furthermore,
the lack of concentric rings, the lack of branches on the radial
ridges, and the lack of a prominent coiledsac in the specimens
from the Valongo Formation and from Sweden suggest that at
this time there is a paucity of character evidence supporting an
eldoniid interpretation.
Conclusions
The discovery of soft-bodied fossils in the upper Valongo
Formation extends the occurrence of deposits with soft-
tissue preservation into the Dapingian-Darriwilian of northern
Gondwana and closes a gap in the soft-bodied fossil record
between the TremadocianFloian Fezouata biota and the
Sandbian fossils of the First Bani Group in Morocco.
Additionally, it expands the extent of BST deposits in deep-
water settings into northern Gondwana. Moreover, it repre-
sents the first occurrence of soft-bodied fossils in Portugal
and the first Ordovician soft-tissue preservation on the
Iberian Peninsula. The discovery of the soft-bodied fossils in
the upper Valongo Formation also shows that it is likely that
many soft-bodied fossils in the Ordovician remain to be dis-
covered, and a new look at deep-water shales and slates of this
time period is warranted.
Acknowledgements We would like to thank P. Thapa for his assistance
using the SEM. P. Van Roy is thanked for his comments on a previous
version of the manuscript. The editor, Allison Daley, William Ausich, and
an anonymous referee are thanked for their comments. This is a contri-
bution to ICT, Institute of Earth Sciences, Department of Geosciences,
Environment and Spatial Planning, University of Porto, and to the IGCP
Project 653.
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... Here, shelly and soft-bodied organisms characteristic of both Cambrian (e.g., radiodonts, lobopodians, marrellomorphs, nektaspids, paleoscolecids) and Paleozoic (e.g., horseshoe crabs, eurypterids, phyllocarids, various echinoderms, mollusks, and bryozoans) faunas occur together (Van Roy et al., 2015). A few other sparser assemblages may provide comparable windows in other regions (e.g., Muir et al., 2014;Balinski and Sun, 2015;Botting et al., 2015;Hearing et al., 2016;Aris et al., 2017;Kimmig et al., 2019). The occurrence of Tomlinsonus in shallow marine deposits in Ontario, preserved alongside diverse echinoderms, trilobites, brachiopods, and bryozoans, provides a tentative connection with these other sites and indicates that marrellomorphs were likely typical members of Ordovician marine shelf communities. ...
... Here, shelly and soft-bodied organisms characteristic of both Cambrian (e.g., radiodonts, lobopodians, marrellomorphs, nektaspids, paleoscolecids) and Paleozoic (e.g., horseshoe crabs, eurypterids, phyllocarids, various echinoderms, mollusks, and bryozoans) faunas occur together (Van Roy et al., 2015). A few other sparser assemblages may provide comparable windows in other regions (e.g., Muir et al., 2014;Balinski and Sun, 2015;Botting et al., 2015;Hearing et al., 2016;Aris et al., 2017;Kimmig et al., 2019). The occurrence of Tomlinsonus in shallow marine deposits in Ontario, preserved alongside diverse echinoderms, trilobites, brachiopods, and bryozoans, provides a tentative connection with these other sites and indicates that marrellomorphs were likely typical members of Ordovician marine shelf communities. ...
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Ordovician open marine Lagerstätten are relatively rare and widely dispersed, producing a patchy picture of the diversity and biogeography of nonmineralized marine organisms and challenging our understanding of the fate of Cambrian groups. Here, for the first time, we report soft-bodied fossils, including a well-preserved marrellomorph arthropod, fragmentary carapaces, and macroalgae, from the Late Ordovician (Katian) Upper Member of the Kirkfield Formation near Brechin, Ontario. The unmineralized elements and associated exceptionally preserved shelly biota were entombed rapidly in storm deposits that smothered the shallow, carbonate-dominated shelf. The marrellomorph, Tomlinsonus dimitrii n. gen. n. sp., is remarkable for its ornate, curving cephalic spines and pair of hypertrophied appendages, suggesting a slow-moving, benthic lifestyle. Reevaluation of marrellomorph phylogeny using new data favors an arachnomorph affinity, although internal relationships are robust to differing outgroup selection. Clades Marrellida and Acercostraca are recovered, but the monophyly of Marrellomorpha is uncertain. The new taxon is recovered as sister to the Devonian Mimetaster and, as the second-youngest known marrellid, bridges an important gap in the evolution of this clade. More generally, the Brechin biota represents a rare window into Ordovician open marine shelf environments in Laurentia, representing an important point of comparison with contemporaneous Lagerstätten from other paleocontinents, with great potential for further discoveries. UUID: http://zoobank.org/884589d0-08f7-4398-ab42-1f5d459be9e9
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Burgess Shale-type fossil assemblages provide a unique record of animal life in the immediate aftermath of the so-called “Cambrian explosion.” While most soft-bodied faunas in the rock record were conserved by mineral replication of soft tissues, Burgess Shale-type preservation involved the conservation of whole assemblages of soft-bodied animals as primary carbonaceous remains, often preserved in extraordinary anatomical detail. Burgess Shale-type preservation resulted from a combination of influences operating at both local and global scales that acted to drastically slow microbial degradation in the early burial environment, resulting in incomplete decomposition and the conservation of soft-bodied animals, many of which are otherwise unknown from the fossil record. While Burgess Shale-type fossil assemblages are primarily restricted to early and middle Cambrian strata (Series 2–3), their anomalous preservation is a pervasive phenomenon that occurs widely in mudstone successions deposited on multiple paleocontinents. Herein, circumstances that led to the preservation of Burgess Shale-type fossils in Cambrian strata worldwide are reviewed. A three-tiered rank classification of the more than 50 Burgess Shale-type deposits now known is proposed and is used to consider the hierarchy of controls that regulated the operation of Burgess Shale-type preservation in space and time, ultimately determining the total number of preserved taxa and the fidelity of preservation in each deposit. While Burgess Shale-type preservation is a unique taphonomic mode that ultimately was regulated by the influence of global seawater chemistry upon the early diagenetic environment, physical depositional (biostratinomic) controls are shown to have been critical in determining the total number of taxa preserved in fossil assemblages, and hence, in regulating many of the important differences among Burgess Shale-type deposits.
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The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätte in northeastern Utah and southeastern Idaho. It is older than the more well-known Wheeler and Marjum Lagerstätten from western Utah, and the Burgess Shale from Canada. The Spence Shale shares several species in common with these younger deposits, yet it also contains a remarkable number of unique species. Because of its relatively broad geographic distribution, and the variety of different palaeoenvironments and taphonomy, the fossil composition and likelihood of recovering weakly skeletonized (or soft-bodied) taxa varies across localities. The Spence Shale is not only widely acknowledged for its collection of soft-bodied taxa, but also for its abundant trilobites and hyoliths. Recent discoveries from the Spence include problematic taxa and insights about the nature of palaeoenvironmental and taphonomic variation between different localities.
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The Winneshiek Shale (Middle Ordovician, Darriwilian) was deposited in a meteorite crater, the Decorah impact structure, in NE Iowa. This crater is 5.6 km in diameter and penetrates Cambrian and Ordovician cratonic strata. It was probably situated close to land in an embayment connected to the epicontinental sea; typical shelly marine taxa are absent. The Konservat-Lagerstätte within the Winneshiek Shale is important because it represents an interval when exceptional preservation is rare. The biota includes the earliest eurypterid, a giant form, as well as a new basal chelicerate and the earliest ceratiocarid phyllocarid. Conodonts, some of giant size, occur as bedding plane assemblages. Bromalites and rarer elements, including a linguloid brachiopod and a probable jawless fish, are also present. Similar fossils occur in the coeval Ames impact structure in Oklahoma, demonstrating that meteorite craters represent a novel and under-recognized setting for Konservat-Lagerstätten.
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The Weeks Formation in Utah is the youngest (c. 499 Ma) and least studied Cambrian Lagerstätte of the western USA. It preserves a diverse, exceptionally preserved fauna that inhabited a relatively deep water environment at the offshore margin of a carbonate platform, resembling the setting of the underlying Wheeler and Marjum formations. However, the Weeks fauna differs significantly in composition from the other remarkable biotas of the Cambrian Series 3 of Utah, suggesting a significant Guzhangian faunal restructuring. This bioevent is regarded as the onset of a transitional episode in the history of life, separating the two primary diversifications of the Early Paleozoic. The Weeks fossils have been strongly affected by late diagenetic processes, but some specimens still preserve exquisite anatomical details.
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The Pioche Formation of SE Nevada preserves a diverse soft-bodied fauna from the early and middle Cambrian (Series 2–3: Stage 4–5). While the fauna is dominated by arthropods, animals belonging to other taxa can be found. Here we document the first occurrence of Herpetogaster collinsi outside the Burgess Shale. Further, the specimens are from the Nephrolenellus multinodus biozone and thus represent the oldest occurrence of the species, as well as possibly the earliest soft-bodied deuterostomes in Laurentia.
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The Rockslide Formation (middle Cambrian, Drumian, Bolaspidella Zone) of the Mackenzie Mountains, northwestern Canada, hosts the Ravens Throat River Lagerstatte, which consists of two, 1-m thick intervals of greenish, thinly laminated, locally burrowed, slightly calcareous mudstone yielding a low-diversity and low-abundance fauna of bivalved arthropods, ‘worms’, hyoliths, and trilobites. Also present are flattened, circular, black carbonaceous objects averaging 15 mm in diameter, interpreted as coprolites preserved in either dorsal or ventral view. Many consist of aggregates of ovate carbonaceous flakes 0.5–2 mm long, which are probably compacted fecal pellets. Two-thirds contain a variably disarticulated pair of arthropod valves, and many also contain coiled to fragmented, corrugated ‘worm’ cuticle, either alone or together with valves. A few contain an enrolled agnostoid. In rare cases a ptychoparioid cranidium, agnostoid shield, bradoriid valve, or hyolith conch or operculum is present; these are taken to be due to capture and ingestion of bioclasts from the adjacent seafloor. Many of the coprolites are associated with semi-circular spreiten produced by movement of the worm-like predator while it occupied a vertical burrow. Its identity is unknown but it clearly exhibited prey selectivity. Many coprolites contain one or more articulated hyoliths, ptychoparioid trilobites, or outstretched agnostoid arthropods oriented dorsal side up. These are interpreted as opportunistic coprovores drawn to the organic-rich fecal mass while it was lodged near the entrance to the burrow. This argues that hyoliths were mobile detritivores, and agnostoids were mainly nektobenthic or benthic, like the ptychoparioid trilobites. Fecal matter was probably an important source of nutrition in the Cambrian food web.
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