Zoological Journal of the Linnean Society, 2010, 158, 477–500. With 15 figures
A new arthropod from the Early Cambrian of North
Greenland, with a ‘great appendage’-like antennula
MARTIN STEIN*
Department of Earth Sciences (Palaeobiology), Uppsala University, Villavägen 16, SE-752 36
Uppsala, Sweden
Received 13 May 2008; accepted for publication 20 January 2009
Kiisortoqia soperi gen. et sp. nov. is an arthropod species from the Early Cambrian Sirius Passet Lagerstätte
of North Greenland. A head, incorporating four appendiferous segments and biramous limbs, with an anteroposteriorly compressed basipod with a spine bearing median edge, support the euarthropod affinities of K. soperi gen.
et sp. nov. Similarities with ‘short great appendage’ arthropods, or megacheirans, like the nine-segmented
endopod, and the flap- or paddle-like exopod, may be symplesiomorphies. The antennula, however, resembles in
composition and size the anteroventral raptorial appendage of anomalocaridids. Thus, the morphology of K. soperi
gen. et sp. nov. provides additional support for the homologization of the anomalocaridid ‘great appendage’ with
the appendage of the antennular or deutocerebral segment of extant Euarthropoda.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500.
doi: 10.1111/j.1096-3642.2009.00562.x
ADDITIONAL KEYWORDS: Arthropoda – arthropods – Sirius Passet.
INTRODUCTION
‘GREAT APPENDAGE’ ARTHROPODS
Arthropods with a pair of large anteroventral grasping appendages, the so-called ‘great appendages’,
appear to have been a common component of Cambrian arthropod faunas, both in terms of diversity and
number of individuals (e.g. Chen, Waloszek & Maas,
2004; Liu, Hou & Bergström, 2007). The phylogenetic
position of some of these taxa within Arthropoda, or
even their arthropod affinities, is still controversial
(e.g. Hou & Bergström, 2006), and thus it is not
surprising that the homology of the anteroventral
‘great appendages’ between taxa has only been
accepted in recent years, although the segmental
identity of the limb pair still remains disputed (Budd,
2002; Chen et al., 2004; Scholtz & Edgecombe, 2006).
The ‘great appendage’ has been considered to
represent either a pre-antennular (protocerebral)
*Corresponding author. Current address: Museum of
Evolution, Uppsala University, Norbyvägen 16, SE-752 36
Uppsala, Sweden. E-mail: [email protected]
appendage that was either lost or transformed into
the hypostome–labrum complex in the stem lineage of
Euarthropoda (Budd, 2002), or it has been assumed to
be homologous with the (deutocerebral) euarthropod
antennula and chelicera (Chen et al., 2004; Waloszek
et al., 2005; Scholtz & Edgecombe, 2006). Correspondingly, ‘great appendage’ arthropods have been considered to be derivatives of the euarthropod stem lineage
(Budd, 2002), chelicerate euarthropods, with the
raptorial anteroventral limb representing an autapomorphy of Chelicerata (Chen et al., 2004), or euarthropods, with the ‘great appendage’ representing
a symplesiomorphy of Euarthropoda (Scholtz &
Edgecombe, 2006).
In fact, there are two types of ‘great appendages’:
one is a long, leg-like structure, consisting of a
peduncle and about 15 short articles; the other, the
so-called ‘short great appendage’, is a sturdy grasping
limb, with a bipartite peduncle and a distal part of
three or four articles bearing stout spines, which
gives it a claw-like appearance (Chen et al., 2004; Liu
et al., 2007). Whereas the long type is found in the
controversially discussed anomalocaridids, including
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
477
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M. STEIN
Anomalocaris saron Hou, Bergström & Ahlberg, 1995
and Amplectobelua symbrachiata Hou et al., 1995, the
short type occurs in taxa sharing a number of
euarthropod traits, the so-called Megacheira Hou &
Bergström, 1997. Only one purported anomalocaridid,
Parapeytoia yunnanensis Hou et al., 1995, from the
Early Cambrian Maotianshan Shale, had a ‘short
great appendage’, which together with other features
of this species suggests megacheiran, rather than
anomalocaridid, affinities. Thus, the question of
homology of the ‘great appendage’ across the spectrum of fossil taxa needs to be reassessed, especially
as the food-gathering, limb-like, 15-segmented antennula has been recognized as a symplesiomorphy of
Arthropoda s.s. (Waloszek et al., 2005).
Kiisortoqia soperi gen. et sp. nov. from the Early
Cambrian Sirius Passet Lagerstätte, may, as the
megacheirans, rest comfortably within the Euarthropoda. Yet, it features a long, leg-like grasping
appendage that is very similar to that of the anomalocaridids. This may reinforce the claim of homology
between the two ‘great appendage’ types, and give
further clues to the segmental identity of the large
anteroventral appendages of certain fossil arthropods.
SIRIUS PASSET
FAUNA
The Sirius Passet Lagerstätte (Conway Morris et al.,
1987) has yielded one of the oldest exceptionally
preserved Cambrian biota. It is Early Cambrian
(Nevadella zone) in age, correlated with stage 3 of the
provisional Cambrian series 2 (Babcock et al., 2005).
So far, apart from sponges (Rigby, 1986), articulated
halkieriids (Conway Morris & Peel, 1995; Vinther &
Nielsen, 2005), and the polychaete Phragmochaeta
canicularis Conway Morris & Peel, 2008, mostly
arthropods have been described from the fauna,
including putative derivatives of the early euarthropod stem lineage such as Kerygmachela kierkegaardi
Budd, 1993, Pambdelurion whittingtoni Budd, 1997,
and the tardipolypod Hadranax augustus Budd &
Peel, 1998. Euarthropods are represented by the trilobite Buenellus higginsi Blaker, 1988 and the nektaspid Buenaspis forteyi Budd, 1999, and possibly by
the purported trilobite Kleptothule rasmusseni Budd,
1995. Isoxys volucris Williams, Siveter & Peel, 1996,
and Pauloterminus spinodorsalis Taylor, 2002 rest
within Arthropoda s.s. sensu Maas et al. (2004), but
the exact phylogenetic positions of the latter two
remain unresolved.
MATERIAL AND METHODS
The material was collected from talus slopes derived
from the lower part of the Buen Formation during
several expeditions between 1985 and 2006. The fossil
locality is situated on the south side of the valley
connecting J. P. Koch Fjord and Brainard Sund in
north-west Peary Land, central North Greenland
(82°47.6′N, 42°13.7′W; 450 m a.s.l.; Fig. 1).
Where required, specimens were prepared
mechanically with a pneumatic chisel. All specimens
were cleaned with an ultrasound bath prior to study,
which proved to be effective in removing the finegrained weathering products and mud that would
otherwise obscure delicate features.
The specimens are of low relief, and only the threedimensionally preserved axial structures contrast in
colour with the dark-grey to black surrounding shale
matrix. Coating the specimens with ammonium chloride and using low-angle light gave the best results
for study. Interpretative line drawings were prepared
with vector illustration software, where photographs
were placed on a background layer and drawings
were made with a drawing tablet on an additional
layer.
Measurements were made on digital photographs
using the graphic software GraphicConverter v6.0.
Because of the predominant oblique taphonomic
aspect, and the resulting lateral compaction, only
sagittal measurements were taken.
The items measured included: (1) the total length,
measured from the anterior margin of the head shield
to the posterior margin of the tail shield; (2) the head,
measured from the anterior margin to the posterior
margin of the head shield; (3) tergites 1–10, measured
from the anterior margin to the posterior margin of
the tergite.
The reconstructions were created using the
modelling
software
BLENDER
(http://www.
blender.org). In order to perform the modelling, additional approximate measurements were taken to
maintain proportions. The model was rigged with an
armature that allows the position of the individual
segments, limbs, and their components (basipods,
endopod podomeres, exopods, and articles) to be
changed.
PRESERVATION
AND TAPHONOMY
A total of 175 specimens of K. soperi gen. et sp. nov.
were available for this study. All are more or less
complete: disarticulated material is not known.
Kiisortoqia soperi gen. et sp. nov. was sclerotized, as
no signs of soft cuticle, such as wrinkles, could be
observed, whereas pivot joints can be detected on the
antennula. Yet, sclerotization seems to have been
comparatively weak, as the specimens are preserved
with lower relief than other Sirius Passet Arthropoda
s.s., e.g. B. forteyi or K. rasmusseni, and features such
as tergal boundaries are faint. Structures in the axial
region often have a considerably higher relief than
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
479
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
C
B
B
100 km
Peary
Land
J.P. Koch
Fjord
N
A
N
Freuchen
Land
Brain
ard S
und
C
Neogene
Polkorridoren Group
ce
Buen Formation
Portfjeld Formation
p
ca
I
Fossil locaity
N
J.
P.
K
oc
h
Fj
or
d
5 km
Figure 1. Map of the locality. A, overview map of Greenland and North America; the rectangle marks the area shown
in (B). B, overview map of North Greenland. C, detailed map of the Sirius Passet locality.
Figure 2. Schematic model of the predominant oblique mode of entombment of Kiisortoqia soperi gen. et sp. nov. One
limb series is extended under the tergopleurae, whereas the other is folded under the axis. A, ventral view. B, frontal view.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
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M. STEIN
the remainder, and commonly have a marked yelloworange stain (Babcock & Peel, 2007). A similar phenomenon is known from Leanchoilia superlata
Walcott, 1912 from the Middle Cambrian Burgess
Shale, where it was attributed to the early permineralization of mid-gut diverticula (Butterfield, 2002).
Budd (1998) reported preservation of muscle tissue in
Pambdelurion whittingtoni from the Sirius Passet
Lagerstätte, although his interpretation was later
questioned by Butterfield (2002). Independent of
interpretation, some of the three-dimensional axial
structures in K. soperi gen. et sp. nov. bear some
resemblance to structures observed in Pambdelurion
whittingtoni. In areas not affected by this early mineralization, features are effectively projected to one
plane by compaction. Thus, cuticular structures
occurring at a lower level may be imprinted through
overlying structures, e.g. tergite boundaries visible
under adjacent tergites, or setal fringes of exopods
imprinted in the tergopleurae.
The majority of specimens are obliquely entombed,
with the anterior limbs of one limb series tucked
underneath the axial region, and with the opposite
series extending from below the tergopleurae, as
reconstructed in Figure 2. The tergopleurae are more
flattened, and are thus more extended (transverse) on
the side where the appendages protrude, whereas
there is lateral compression, and thus shortening
(transverse), on the opposite side. Of the appendages
tucked under the axial region, only traces of the
exopods are imprinted in the tergites. In specimen
MGUH 28946, bulges under the flattened side may
represent the endopods folded underneath. The posterior limbs of both limb series are often flipped
backwards. The oblique entombment was probably
caused by the length of the limbs combined with their
probable pendant posture in life (cf. Bergström, 1992).
The flexure of the limbs may be the result of postmortem collapse at the time of falling onto the substrate. There appears to be no preference as to which
side collapsed. Only three specimens lie more or less
flat on the shale surface.
The preservation of the limbs is poor, particularly
where several structures usually overlie each other.
Thus, only the distalmost parts of the endopods,
which are not overlain by exopods and/or tergites, are
clearly visible. Proximally, where imbricated exopods
overlie each other, structures can only be traced by
outline in the best specimens. Characteristically,
these areas have a smooth surface. Paradoxically,
delicate details like exopod setae or basipod armature
are preserved, whereas more robust structures like
tergite borders can hardly be traced. Limbs seem to
have been rotated considerably post-mortem. In some
cases, the basipod–exopod joint lies anteriorly, with
the exopod hinged back over the limb; the spines
along the medial face of the basipod point obliquely
backwards, thus indicating the outwards and forwards rotation of the whole limb (Fig. 2A, posterior
limbs). This model, however, does not apply to all of
the material. Basipod spines provide one indicator of
orientation: they mostly point backwards or inwards,
indicating morphological constraints to rotation. The
spines are preserved as a series of holes in specimens
of dorsal aspect, or as a series of studs in specimens
of ventral aspect, but the taphonomic reason for this
is not yet understood. Neither is it clear whether the
two types actually correspond to part and counter
part. Apart from the preservation of the basipod
spines, even the three-dimensional structures differ
between the two types or aspects. Thus, the transverse structures in the axial area are preserved as
bars in ventral aspect and as hollows in dorsal aspect.
Unfortunately, no specimen in the collection is available with both part and counterpart, which could help
to resolve this problem.
TERMINOLOGY
The standardized terminology developed by Walossek
(1993, and later papers; also published as Waloszek)
is followed wherever possible. The term antennula,
rather than antenna, is applied to the anteriormost
appendage, and all subsequent limbs are described
with neutral terminology (see also Stein et al., 2008).
The term ‘axis’ is applied to the raised central region
of the trunk tergites; the term ‘tergopleurae’ is
applied to the lower lateral parts.
TAXONOMY
KIISORTOQIA GEN. NOV.
Derivation of name: From the Kalaallisut (Greenlandic) word kiisortoq, meaning predator.
Diagnosis: As for species.
Type species: Kiisortoqia soperi gen. et sp. nov. (by
monotypy).
KIISORTOQIA
SOPERI SP. NOV.
(FIGS 4–15)
Derivation of name: Named after N.J. Soper, who,
together with A.K. Higgins, collected the first fossils
from the Sirius Passet Lagerstätte.
Diagnosis: Euarthropod with a simple head shield, 16
trunk segments, and a small, semicircular tail shield.
Antennula about one half to two thirds of body length,
sturdy, composed of a peduncle and about 15 articles,
with paired spines medially.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
B
10
8
head (mm)
15
10
0
6
5
frequency (mm)
20
12
A
481
20
25
30
35
40
45
50
55
total length (mm)
25
30
35
40
45
50
total length (mm)
Figure 3. Statistics of selected morphometrics, based on 69 specimens that could be measured. A, size–frequency
histogram based on the total length of the specimens. B, plot of length of the head shield against total length.
Holotype: MGUH 28942.
Type locality and horizon: J.P. Koch Fjord, Peary
Land, central North Greenland; base of the Buen
Formation (Cambrian series 2, stage 3).
Material illustrated: MGUH 28943–28969.
Other material: There are 147 additional specimens.
Repository: Typus specimen and illustrated specimens
are deposited in the Geological Museum, Copenhagen
(with the MGUH prefix).
Description: Dorsal morphology: the observed specimens of K. soperi gen. et sp. nov. range from 234 mm
to 534 mm in total length, with an approximately
normal distribution (Fig. 3A). All specimens in this
range have a trunk with 16 tergites.
The general habitus is subelliptical, with a length
of approximately twice the width, and with the
maximum width in the anterior third of the body at
the third to fifth tergite (Fig. 4). The length of the
head shield is, on average, one fifth of the total length
(Fig. 3B). The trunk tapers from the fifth tergite
backwards to a small tail shield. The trunk and tail
shield are trilobate (Figs 4–6).
The head shield is a simple, convex shield, without
marked trilobation, and is parabolic in outline, and
wider than long.
The trunk consists of 16 segments (Figs 4, 5). The
tergites are short, and are about five times wider than
long. Tergites 1–5 are of almost equal length; tergites
3–5 are widest. The width and length of tergites
decrease posterior to the fifth tergite. Axially, the
posterior border of each tergite overhangs the following tergite by approximately one fifth of its length,
but by less abaxially. The axis is approximately half
the width of the tergites. The first and second tergites
curve towards the anterior abaxially, whereas tergites
posterior to that are straight. The tergopleurae of the
first tergite terminate bluntly posterolaterally, and
those of the second tergite have a pointed posterolateral corner. The tergopleurae of tergites 4–16 are
extended into posterolateral projections. The length of
these projections increases posteriorly.
The tail shield is a semicircular plate, and is twice
as wide as long; the anterior half to two thirds are
trilobate (Figs 4–6).
Ventral morphology: the head carries the large
antennulae and three pairs of biramous limbs ventrally. The hypostome or eyes are not known.
Each antennula reaches a length of one half to
two thirds the total length of the body: it consists of
a peduncle and about 15 articles. The peduncle is at
least twice as long as the proximal article, and is
distinguished from the articles by the absence of
armament. It inserts well below the head shield
(Fig. 7D). The articles are cylindrical, with a flat to
concave medial side (Fig. 7D). Articles 1–6 are of
equal width, but increase in length distally. Articles
7–15 decrease in both width and length. Each
article carries two spines, set wide apart,
medially.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
482
M. STEIN
A
app1
ex
app2
en
B
ant
app2
ex
cs
tg1
bas
spn
tg2
gud
tg15
tg16
ts
5 mm
5 mm
Figure 4. Holotype of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28942, arrows mark exsagittal mineralizations. B,
drawing of MGUH 28942, heavy lines indicate non-biological features, such as cracks. Abbreviations: ant, antennula; app1
ex, exopod of first postantennular appendage; app2 en, endopod of second postantennular appendage; app2 ex, exopod of
second postantennular appendage; bas spn, spines on the median edge of the basipod; cs, cephalic shield; gud, gut
diverticulae; tg1, first trunk tergite; tg2, second trunk tergite; tg15, fifteenth trunk tergite; tg16, sixteenth trunk tergite;
ts, tail shield.
All postantennular limbs are biramous. The sizes
increase from the first postantennular limb to the
first trunk limb, and decrease posterior to the fifth
trunk limb.
The arthrodial membrane between basipod and
limb insertion is medially supported by at least three
more strongly sclerotized ridges (Fig. 8C, arrows).
The basipod is trapezoidal in outline and long
(Figs 8A, B, 9D): its length from the limb insertion to
the mediodistal end is almost one quarter of the
tergal width, and about one fifth to one quarter of the
total length of the limb. The median face carries a
biserial armature of spines (Figs 8C, D, 9A, 10C, D,
11D). The number of spines in the rows varies
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
483
en
A
ant
ant
cs
tg1
ts
tg16
5 mm
B
C
ant
ant
app1
ex
app2
ex
cs
tg1
tg2
bas
spn
tg15
tg16
ts
5 mm
5 mm
Figure 5. Kiisortoqia soperi gen. et sp. nov. A, MGUH 28963, oblique entombment, showing the length of the limbs.
B, MGUH 28964, horizontal entombent, showing the length of the antennula. C, drawing of MGUH 28964. Abbreviations:
ant, antennula; app1 ex, exopod of first postantennular appendage; app2 ex, exopod of second postantennular appendage;
bas spn, spines on the median edge of the basipod; cs, cephalic shield; en, endopod; tg1, first trunk tergite; tg2, second
trunk tergite; tg15, fifteenth trunk tergite; tg16, sixteenth trunk tergite; ts, tail shield.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
484
M. STEIN
A
B
tg15
tg16
ts
2 mm
C
2 mm
D
gut?
tg15
tg16
ts
2 mm
2 mm
Figure 6. Kiisortoqia soperi gen. et sp. nov., posterior part of trunk and tail shield. A, MGUH 28966, parts of the
exopods are represented by the margins with setae, and arrows mark the exsagittal mineralizations. B, drawing of MGUH
28966, exopods indicate that the posterior limbs were flipped backwards at the time of burial. C, MGUH 28962, in the
posterior part of the trunk, an elongate hollowed-out structure potentially marks the position of the gut (gut?). D, drawing
of MGUH 28962. Abbreviations: tg15, fifteenth trunk tergite; tg16, sixteenth trunk tergite; ts, tail shield.
between the basipods of the limbs. The basipods of
the anterior trunk segments carry the highest
number of spines, with up to twelve in the anterior
series, and about ten in the posterior series. Spines in
the anterior series are of roughly equal size; two or
three larger spines are inserted in the distal half of
the posterior series.
The endopod comprises nine podomeres (Figs 9A,
10B). The podomeres are cylindrical; the distal ones
have a slight projection laterodistally, which may be
drawn out into a small spine (Figs 9A, B, 10B). The
first podomere is one third to one half the length of
the basipod (Fig. 9A). The eighth podomere carries
two spines distally, flanking the terminal podomere,
which is a long, sturdy spine (Fig. 9C, arrows).
The exopod is a paddle-shaped flap, fringed with
setae. It reaches more than two thirds the length of
the endopod (Figs 9A, 10B). Proximally, it articulates
in a hinge joint along the slanting lateral edge of the
basipod (Fig. 11D).
DISCUSSION
REMARKS
ON MORPHOLOGY
As a result of the variable states of preservation, not
all morphological features are accessible for a
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
A
485
B
5 mm
C
5 mm
tg1
D
ant
2 mm
cs
ped
app1
ex
app2 app2
en
ex
5 mm
E
1 mm
Figure 7. Details of the antennula of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28948, the most completely
preserved antennula, showing medial spines. B, drawing of MGUH 28948. C, MGUH 28953, showing pivot joints between
articles (arrows). D, MGUH 28960, antennula rotated, showing peduncle and concave median surface of articles, arrows
mark spines. E, MGUH 28954, showing widely spaced double rows of spines (arrows). Abbreviations: ant, antennula; app1
ex, exopod of first postantennular appendage; app2 en, endopod of second postantennular appendage; app2 ex, exopod of
second postantennular appendage; cs, cephalic shield; ped, peduncle; tg1, first trunk tergite.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
486
M. STEIN
A
B
en2
cs
en1
bas
tg1
tg2
5 mm
C
5 mm
D
bas
spn
5 mm
2 mm
Figure 8. Details of the postantennular limbs of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28947, showing shape
of basipod and first podomere, the arrows mark exsagittal mineralizations. B, drawing of MGUH 28947. C, MGUH 28945,
showing sclerotized ridges in the arthrodial membrane between body and basipod (arrows). D, MGUH 28959, showing
posteriorly directed basipod spines. Abbreviations: bas, basipod; bas spn, spines on the median edge of the basipod; cs,
cephalic shield; en1, first podomere of endopod; en2, second podomere of endopod; tg1, first trunk tergite; tg2, second
trunk tergite.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
A
app3
bas
487
app1
app2 bas
bas
cs
tg1
exs
tg2
en6
en7
en8
en9
en5
B
en4
en3
en2
en1
2 mm
C
app2
en
app1
ex
ant
1 mm
1 mm
Figure 9. Details of the postantennular limbs of Kiisortoqia soperi gen. et sp. nov. A, close-up of MGUH 28946,
showing endopods, exopod setae, and basipod spines (see Fig. 8B for an interpretative line drawing), the first postantennular limb is only marked by the basipod armature, arrows point to bulges that may represent the limbs of the
opposing limb series folded under the axis. B, close-up of the postantennular limbs of MGUH 28942, arrows mark joints
between the podomeres of the endopod. C, MGUH 28956, close-up of distal parts of endopods, showing the distal (ninth)
podomere, which is a stout spine (arrows). Abbreviations: ant, antennula; app1-3 bas, basipods of first to third
postantennular appendages; app1 ex, exopod of first postantennular appendage; app2 en, endopod of second postantennular appendage; cs, cephalic shield; en1–9, first to ninth podomere of the endopod; exs, exopod setae; tg1, first trunk
tergite; tg2, second trunk.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
488
M. STEIN
A
B
ant
cs
en
tg1
tg2
bas
spn
C
exs
en
tg15
tg16
ts
5 mm
D
tg15
cs
tg1 tg2
ant
app1
ex
app2
en
app3
en
5 mm
Figure 10. Details of the postantennular limbs of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28946, overview of an
almost complete specimen, showing the length of the postantennular limbs and basipod spines. B, interpretative line
drawing of anterior part of MGUH 28946, the endopod podomeres could only be traced on the actual specimen under
oblique light from varying angles, see also Fig. 10A. C, MGUH 28949, basipod spines (arrow) point posteriorly (left). D,
MGUH 28951, specimen in horizontal entombment, appendages are flipped anteriorly, as indicated by basipod spines.
Abbreviations: ant, antennula; app1 ex, exopod of first postantennular appendage; app2 en, endopod of second postantennular appendage; app3 en, endopod of third postantennular appendage; bas spn, spines on the median edge of the
basipod; cs, cephalic shield; en, endopod; exs, exopod setae; tg1, first trunk tergite; tg2, second trunk tergite; tg15,
fifteenth trunk tergite; tg16, sixteenth trunk tergite; ts, tail shield.
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A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
A
489
B
app2
app1 en
ex
app3
en
app2
ex
app1
en
1 mm
C
1 mm
D
exs
en1
asr
psr
1 mm
1 mm
Figure 11. Details of the postantennular limbs of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28950, showing the
shape and size of the anterior exopods, the endopod of the third postantennular limb is covered by the exopod of the
second. B, MGUH 28967, posterior part of trunk, the exopods are made visible by the marginal setae (arrows). C, MGUH
28952, posterior part of trunk, the exopods are made visible by the marginal setae (arrows) imprinted in tergites. D,
MGUH 28969, showing the articulation of the exopod along the slanting lateral edge of the basipod (arrows), the joint
between the basipod and the first endopod podomere is seen by a sharp fold, and the exopod is probably represented by
the smooth area, with the setae probably being imprints of setae belonging to the exopod of the next anterior (left) limb.
Abbreviations: app1 en, endopod of first postantennular appendage; app1 ex, exopod of first postantennular appendage;
app2 en, endopod of second postantennular appendage; app2 ex, exopod of second postantennular appendage; app3 en,
endopod of third postantennular appendage; asr, anterior spine row of basipod; en1, first podomere of endopod; exs, exopod
setae; psr, posterior spine row of basipod.
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M. STEIN
straightforward description. Some are obscured by
taphonomic circumstances, and are subject to interpretation under consideration of taphonomy and
comparisons with other taxa. These features are
discussed in this section.
The head shield is covered with concentric wrinkles
resulting from compaction from its original convex
form (Figs 4, 7D, 8A, B, 10A, B). The centre of the
head shield is often free of wrinkles. This area is
narrower than the trunk axis. Wrinkles and folds are
evenly distributed from this smooth region to the
margins. It is therefore assumed that the head shield
was a simple, convex shield, without marked trilobation. The trilobation of the trunk tergites and the tail
shield is often obscured by compaction, and the
oblique entombment. It is most apparent on the
convex side, where it may be creased by a sharp fold
(Figs 4–6).
Neither eyes nor a hypostome, or the mouth, could
be found in any of the 175 specimens. If the eyes in K.
soperi gen. et sp. nov. were situated under the anterior border of the head shield, as in e.g. Leanchoilia
illecebrosa (Hou, 1987), it is possible that they,
together with the other ventral features of that area,
were not preserved.
The insertion of the antennula cannot be traced
because of the poor preservation of the limb portions
under the tergites, but the peduncle extends from
well below the head shield (Fig. 7D). Whether or not
the peduncle was composed of two articles, as in other
arthropods with ‘great appendages’ (Chen et al.,
2004), cannot be verified, as the proximal portions of
the limb are not accessible. The distalmost articles of
the antennula are poorly preserved; therefore, the
exact number of articles cannot be established. Two
medial spines on articles can be confirmed for at least
articles 1–13 (Fig. 7A, B, D, E); the preservation of
the articles distal to these is too poor for description.
In cases where the antennula is rotated, the double
rows of spines are evident (Fig. 7E).
Where the first postantennular limb extends from
underneath the head shield, it is usually directly
adjacent to the antennula, and somewhat rotated
anteriorly, as is, to a lesser degree, the second postantennular limb (Figs 4, 7D, 10D, 11A). As this occurs
in the majority of specimens, where preserved, it is
assumed that this rotation reflects an original difference in orientation.
The median face of the basipod often lies parallel
with the bedding plane, with the spines perpendicular
to it (Figs 8C, 9A, 11A). This indicates a stronger
sclerotization of the median face relative to the rest of
the limb. The armature of the basipod is less clearly
preserved on the first postantennular limb and the
posterior trunk limbs, and the spines often lie parallel
with the bedding plane. It seems that the armature is
less well developed, and that the median face is less
strongly sclerotized on these limbs.
The preservation of the articulations of endopod
podomeres is generally poor; often only the distal
articulations are exposed (Fig. 9B, arrows).
The articulation between basipod and exopod is
often obscured by the overlying tergites and limb
portions, but can be traced in rare instances. The
setae fringing the exopod are in many instances the
only part that can be traced (Fig. 11B, C). Because of
the poor preservation of the proximal portions,
whether or not the exopod was bipartite, as in the
species of Leanchoilia (García-Bellido & Collins, 2007;
Liu et al., 2007), or the stem lineage crustacean
Oelandocaris oelandica Müller, 1983 (Stein et al.,
2008), cannot be ascertained. The oblique mode of
entombment might be an indirect indication for a
bipartite exopod, as in that case the distal parts could
flip backwards, and lie flat on the sediment surface,
whereas undivided exopods would stick out from the
folded limbs (Fig. 2), rendering such a morphology
less likely.
No ventral details of the tail shield are preserved.
The presence of sternites is unclear. In rare
instances, there are fragments of seemingly cuticular
surfaces preserved in the axial area, but the preservation is not sufficient to unequivocally identify these
as sternites (Fig. 12A).
Internal structures: Transverse bars are located in the
axial region in a number of specimens, and these
sometimes appear to be composed of two or more
strands (Fig. 12B, C, E). They are common in specimens in ventral aspect, where the three-dimensional
structures described above are not preserved, and the
underside of the tergites is exposed. This indicates a
relatively dorsal position of the bars. Transverse bars
have been described from the trilobite Placoparia
cambriensis Hicks, 1875, and have been tentatively
interpreted as tendinous bars (Whittington, 1993).
Putative tendinous bars have also been reported from
the naraoiid Misszhouia longicaudata (Zhang & Hou,
1985; Edgecombe & Ramsköld, 1999). The mode of
preservation of these structures in both P. cambriensis and M. longicaudata differs considerably from that
in K. soperi gen. et sp. nov. In both taxa, the alleged
tendinous bars are situated in the plane of the sternites. Placoparia cambriensis is known only from
specimens preserved in dorsal aspect, with a sagittal
view of the sternites exposed; specimens of M. longicaudata are preserved in ventral aspect, with the
bars shown between the sternites. In K. soperi gen. et
sp. nov. the bars occur dorsally, and often coincide
with the anterior border of the tergites (Fig. 12B, C).
In the extant crustacean Hutchinsoniella maracantha
Sanders (1955), the ‘dorsal transverse tendon’ is
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A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
A
491
B
2 mm
C
2 mm
D
2 mm
2 mm
E
2 mm
Figure 12. Details of axial features of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28948, specimen in ventral aspect,
close-up of posterior part of axial features, the smooth structures on top of the three-dimensional mineralizations may
represent sternites. B, MGUH 28958, ventral aspect, showing transverse bars adjacent to anterior border of tergites. C,
MGUH 28965, ventral aspect, showing transverse bars composed of at least two strands adjacent to anterior border of
tergites. D, MGUH 28943, dorsal aspect, close-up of anterior part of trunk axis, showing transverse hollows in axial
mineralizations. E, MGUH 28946, close-up of axis, ventral aspect, showing transverse bars and continuous patch of
corrugated surface that may represent fossilized muscle tissue, the arrow marks the exopod setae.
found in this very position (Boudreaux, 1979). In the
dorsal aspect specimens of K. soperi gen. et sp. nov.,
the structures can be preserved as hollow transverse
structures within three-dimensionally preserved
features (Figs 12D, 13A, D). Similar structures are
known from Leanchoilia superlata (Butterfield, 2002:
fig. 2).
Many specimens of K. soperi gen. et sp. nov. have
three-dimensional structures preserved in the axial
area (Figs 4, 13C, D). One type of such structure
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492
M. STEIN
A
B
2 mm
2 mm
C
2 mm
D
2 mm
Figure 13. Details of axial features of Kiisortoqia soperi gen. et sp. nov. A, MGUH 28955, dorsal aspect, close-up of
anterior part of trunk and posterior part of head shield (left), showing putative muscle tissue in association with
transverse hollows; B, MGUH 28966, ventral aspect, close-up of middle part of trunk, showing corrugated surface with
transverse interruptions, the arrows point to exsagittal mineralizations. C, MGUH 28959, dorsal aspect, showing
segmentally arranged, putative midgut diverticulae, the radial orientation of planar elements is seen in the anterior two
trunk segments, and the sagittal orientation is seen in the posterior trunk segments. D, MGUH 28944, dorsal aspect,
showing hollows after segmentally arranged axial mineralizations.
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A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
493
A
2 mm
B
C
2 mm
2 mm
Figure 14. Potential gut traces of Kiisortoqia soperi gen. et sp. nov., all specimens in dorsal aspect. A, MGUH 28957,
showing continuous trace between segmentally arranged hollows. B, MGUH 28968, close-up of posterior part of trunk and
tail shield, showing hollow trace with transverse annulation. C, MGUH 28961, close-up of posterior part of trunk, showing
a three-dimensionally preserved continuous trace with transverse annulation.
present in a number of specimens is a longitudinally
corrugated surface within the axial region (Fig. 12E),
often interrupted at the transverse bars or tergite
boundaries (Fig. 13A, B). These structures are similar
to structures interpreted as putative muscle tissue
in Pambdelurion whittingtoni (Budd, 1998). Their
association with the transverse bars may provide
further support for both an interpretation of these
structures as muscle tissue, and of the bars representing elements of the intersegmental tendon
system.
The other type of structure observed in specimens
of K. soperi gen. et sp. nov. appears to be paired and
segmental (Figs 4, 13B, C, 14A). Three-dimensionally
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M. STEIN
Figure 15. Reconstruction of Kiisortoqia soperi gen. et sp. nov. A, ventral view, mouth and anus are conjectural. B,
lateral view. C, dorsal view. D, trunk limb in posterior view, the articulation between the exopod and the first endopod
podomere, as well as the hinge dividing the exopod into two portions, are not known; E, trunk limb in oblique posterior
view, with exopod swung backwards.
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
preserved axial structures in L. superlata have been
interpreted as mid-gut diverticula (Butterfield, 2002).
Although there is some gross similarity, the axial
features in K. soperi gen. et sp. nov. differ in structure
and orientation. The planar elements (cf. Butterfield,
2002) are coarser than those observed in L. superlata,
and are oriented parallel with the axis (Fig. 13C).
There are rare indications of radial arrangement
abaxially (Figs 4A, 13C).
A few specimens preserve a continuous sagittal
structure, often in the form of a tubular canal
(Fig. 14). In rare instances this is partly preserved as
an intensely yellow-orange stained in-filling, with an
‘annulated’ appearance (Fig. 14C). This structure may
represent the gut or its contents, but is considerably
wider than the continuous gut trace described from L.
superlata (Butterfield, 2002). The width of the structure is comparable with gut traces encountered in
naraoiids (Bergström, Hou & Hålenius, 2007), interpreted as a ‘swollen digestive system’ by Lin (2006).
Abaxially, at the inner margin of the tergopleurae,
a concentric array of crescentic cavities is frequently
present (Figs 4A, 6C, 8B, 13B, arrows). This occurs
predominantly, but not exclusively, on the side with
the limbs folded underneath. The mode of preservation differs from that of setae or other external features. The high relief of the structure indicates early
permineralization. It therefore seems likely that the
structure is internal, although it does not readily
resemble structures interpreted as gut diverticulae
(cf. Butterfield, 2002; Bergström et al., 2007).
ECOLOGY
In the absence of direct evidence, the interpretation of
the possible life habits of K. soperi gen. et sp. nov.
must rest on inferences from its morphology and from
other taxa. The assumption of an active, swimming,
predatory life habit for K. soperi gen. et sp. nov. is
supported by the following features: (1) all postantennular limbs have large paddle-shaped exopods that
are suitable for swimming; (2) the basipods have
strongly sclerotized, spinose median margins, which
are suitable for grasping and, potentially, for the
mastication of larger food; (3) the antennulae are
robust, and are possibly suitable for capturing prey.
The antennulae of K. soperi gen. et sp. nov.
are reminiscent of the ‘great appendage’ of certain
anomalocaridids, such as Anomalocaris canadensis
Whiteaves, 1892, Anomalocaris saron, and Amplectobelua symbrachiata. A raptorial function is assumed
for Amplectobelua symbrachiata (e.g. Chen, Ramsköld
& Zhou, 1994; Chen et al., 2004; Maas et al., 2004).
Arguments for a grasping function in these anomalocaridids might be supported by the limb-like structure
and robustness of the ‘great appendages’, and possibly
495
the ability to flex inwards (e.g. Chen et al., 1994; Hou
et al., 1995, figs 7, 8). Stout inward-directed spines
might have functioned in concert with the inward
flexure to capture prey. Although the antennula of K.
soperi gen. et sp. nov. is comparable in relative size and
in sturdiness, it lacks some of the potential adaptations of a grasping limb. The spines are more delicate
than those in anomalocaridids, and there is no indication of the ability of strong inward flexure.
The presence of extensive gut diverticulae in fossil
arthropods has been taken as support for a predatory
lifestyle by inference from extant taxa (Butterfield,
2002). Bergström et al. (2007) questioned the general
validity of this argument, largely based on the sediment filling the digestive systems of arthropod fossils
from the Early Cambrian Maotianshan Shale. The
present study does not provide new data to help settle
this controversy, as the gut contents are not known.
Yet, complex taphonomic processes may result in
a secondary sediment filling of arthropod digestive
systems (Lin, 2006). External morphology may
support predation or scavenging as the prime mode of
foraging of K. soperi gen. et sp. nov., whereas there
are no obvious adaptations for sediment ingestion.
Eyes or any other possible photoreceptive structures are not preserved in any of the available specimens of K. soperi gen. et sp. nov. Whether or not this
is a taphonomic artefact is not known. The absence of
well-developed visual organs may be an impediment
in a predatory lifestyle: for example, Chen et al.
(2007) considered vision to have played an important
role in hunting in anomalocaridids. Eyes are also
present in arthropods with a ‘short great appendage’,
such as Haikoucaris ercaiensis Chen et al., 2004,
Jianfengia multisegmentalis Hou, 1987, Fortiforceps
foliosa Hou & Bergström, 1997, and Leanchoilia
species both from the Burgess Shale and the
Maotianshan Shale (García-Bellido & Collins, 2007;
Liu et al., 2007).
PHYLOGENETIC
IMPLICATIONS
‘Great appendage’ arthropods have received a considerable focus of attention during the last years,
because of the controversial hypotheses of their
phylogenetic position and significance (Budd, 2002;
Chen et al., 2004; Cotton & Braddy, 2004; Scholtz &
Edgecombe, 2006).
The term ‘great appendage’ was originally coined
for the anteroventral appendage of Yohoia tenuis
Walcott, 1912 (Whittington, 1974), and was later also
applied to that of L. superlata and closely related
forms from the Middle Cambrian Burgess Shale
(Bruton & Whittington, 1983). Additional species
were subsequently described from the Early Cambrian Maotianshan Shale (e.g. Hou & Bergström,
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M. STEIN
1997). These forms have a sturdy anteroventral ‘short
great appendage’ (Chen et al., 2004) composed of a
bipartite peduncle and a claw of four articles, of which
the three proximal articles are drawn into a stout
spine, which is sometimes serrated or carries a flagellate outgrowth, and the distal article forms a short
spine. All these taxa have a simple head shield, incorporating the segment carrying the eyes and four
appendiferous segments carrying the ‘great appendages’, and three pairs of biramous limbs (Hou &
Bergström, 1997; Chen et al., 2004; Liu et al., 2007),
although some authors consider only two segments
carrying biramous limbs to be present in the head of
the Burgess Shale species of Leanchoilia (GarcíaBellido & Collins, 2007) and Alalcomenaeus cambricus Simonetta, 1970 (Briggs & Collins, 1999). The
limbs have a differentiated basipod and endopod, and
a paddle-like exopod, recently described in detail for
L. illecebrosa (Liu et al., 2007).
More recently, the anteroventral appendage of
anomalocaridids has been considered to be homologous with the ‘short great appendage’ (Budd, 2002;
Chen et al., 2004). ‘Anomalocaridids’ in the loose
sense (e.g. Budd, 2002) comprise a heterogeneous
assemblage of taxa with pivot-jointed limbs and tergites (indicative of Arthropoda s.s.) at one end of the
spectrum, and with alleged lobopod-type appendages
(indicative of Arthropoda s.l.) at the other end of
the spectrum. The former, anomalocaridids sensu
Hou et al. (1995), share a sclerotized mouth circlet
(‘Peytoia’ mouth), the so-called ‘lateral lobes’ or
‘appendage flaps’ (potentially exopods or tergopleurae), with prominent transverse striations, the
pivot-jointed anteroventral grasping appendage, and
well-developed, possibly stalked lateral eyes. The
latter taxa are Kerygmachela kierkegaardi, Pambdelurion whittingtoni, and Opabinia regalis Walcott,
1912. The alignment of these taxa seems to rest more
on superficial similarities than on synapomorphies.
The present paper follows Chen et al. (2004), and
excludes these taxa from anomalocaridids.
Homology statements between the ‘short great
appendage’ and the anomalocaridid ‘great appendage’
have rested mainly on the appendage morphology of
Parapeytoia yunnanensis, a purported anomalocaridid
species from the Maotianshan Shale (Budd, 2002;
Chen et al., 2004). This species is exceptional among
anomalocaridids not only in having a ‘great appendage’
of the ‘short great appendage’ type, but also in being
the only anomalocaridid so far that has yielded specimens with preserved limbs. Euarthropod affinities of
Parapeytoia yunnanensis have been disputed (Hou
et al., 1995; Hou, Bergström & Yang, 2006), but the
arguments in favour of such a radical view are problematic, as they are largely based on a single, poorly
preserved specimen, or take into account features of
different species (e.g. the evidence of soft skin cited by
Hou et al., 2006 is based on Cucumericrus decoratus
Hou et al., 1995). The endopods of Parapeytoia yunnanensis (‘ramipods’ of Hou et al., 1995) are similar to
those of L. illecebrosa (Liu et al., 2007). The median
portion of the ‘propod’, with its armature, opposite to
segmental sternites, is directly comparable with the
basipod of euarthropods. Admittedly, an articulation
with the exopod (‘appendage flap’) is not clearly visible
on the illustrated material, but that may be a preservational artefact in the limited material. On the other
hand, the anomalocaridid affinities of Parapeytoia
yunnanensis have not yet been demonstrated indisputably. Although there is a large, bulbous area around
the mouth, the presence of oral sclerites is not clearly
demonstrated, and neither is the distinct striation of
the ‘appendage flaps’ of anomalocaridids. Parapeytoia
yunnanensis thus remains problematic until more and
better preserved material is described. This unclear
position of Parapeytoia yunnanensis, however, poses
problems to the interpretation of the segmental identity of the anomalocaridid ‘great appendage’.
In megacheirans, the ‘short great appendage’ pair is
the most anterior of the four limb pairs incorporated
into a simple head shield (e.g. Chen et al., 2004; Liu
et al., 2007). Where eyes are known, they occur anterior to the ‘short great appendage’ (Chen et al., 2004;
Liu et al., 2007), and all limbs posterior to the ‘short
great appendage’ are biramous. This configuration
exactly mirrors the euarthropod head composition
(e.g. Waloszek et al., 2005; Waloszek et al., 2007), and
it is therefore most reasonable to assume homology
between the ‘short great appendage’ and the deutocerebral antennula of Crustacea, and the chelicera of
Chelicerata (e.g. Chen et al., 2004; Scholtz & Edgecombe, 2006; Waloszek et al., 2007).
With the unresolved position of Parapeytoia
yunnanensis, renewed support for homology of the
anomalocaridid ‘great appendage’ with the megacheiran ‘short great appendage’, and thereby with antennula and chelicera, may be gained from the data on K.
soperi gen. et sp. nov. presented herein. The antennula of K. soperi gen. et sp. nov. share with the ‘great
appendages’ of Anomalocaris saron and Amplectobelua symbrachiata, the composition of the peduncle,
and about 15 massive, podomere-like articles armed
with paired spines. The spines are more delicate in K.
soperi gen. et sp. nov., and appear to be simple,
whereas Anomalocaris canadensis and Anomalocaris
saron have prong-like spines. The spine morphology
seems, therefore, to be more plesiomorphic, yet the
overall similarity is taken as a support for the homology of the structures. The position of the mouth and
eyes are not known for K. soperi gen. et sp. nov., and
thus there is no direct or dependable topological indication for this limb belonging to the deutocerebral
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A NEW CAMBRIAN ARTHROPOD FROM GREENLAND
segment. Yet, the number of limb-bearing segments
incorporated in the head matches the euarthropod
condition. Furthermore, as in megacheirans, the
limbs following the ‘great appendage’ are biramous,
with a basipod, paddle-like exopod, and an endopod
comprising no more than nine podomeres. Waloszek
et al. (2005) have put forward a hypothesis of an
originally limb-like antennula composed of a peduncle
and about 15 distal articles. Their identification of the
antennula in the euarthropod stem lineage derivatives Fuxianhuia protensa Hou, 1987, Chengjiangocaris longiformis Hou & Bergström, 1991, and
Shankouia zhenghei Chen, Wang, Maas & Waloszek
in Waloszek et al., 2005 was questioned by Scholtz &
Edgecombe (2006), who argued for this appendage
being a protocerebral ‘primary’ antenna. According to
their hypothesis, this appendage was lost along the
stem lineage of Euarthropoda. This reassessment,
mainly based on Fuxianhuia protensa from the Maotianshan Shale seems doubtful. For instance, the
peduncle of the antennula of Fuxianhuia protensa is
considered by these authors to be situated close to the
eye in the published material, which is inconsistent
with the specimens illustrated by Hou & Bergström
(1997: figs 8B, 11C, D), where the antennula apparently inserts far behind the eye, as is also the case in
S. zhenghei. The hypostomal outline, mentioned by
Scholtz & Edgecombe (2006) in a specimen illustrated
by Hou et al. (2004: fig. 16.3a) is conjectural: the
picture does not allow one to discern that feature.
Likewise, the hypostomal outline in one specimen of
Chengjiangocaris longiformis (Waloszek et al., 2005;
Scholtz & Edgecombe, 2006; Budd, 2008) is debatable.
Part of the inferred outline (Budd, 2008: figs 5, 6)
seems to be part of a dark stain connected with the
gut, which may represent gut diverticulae.
The presence of a second pre-oral limb in Fuxianhuia protensa is equally doubtful, as shown by
Waloszek et al. (2005), who interpreted the structure
as gut diverticula. It is not consistently geniculate
(e.g. Waloszek et al., 2005: fig. 2), as was claimed by
Scholtz & Edgecombe (2006), and has been taken as
an argument against gut diverticula. Furthermore,
Scholtz & Edgecombe (2006) stated that the gut was
preserved only posterior to the structures. However, a
photograph published by Bergström & Hou (2005: 56)
shows the gut extending all the way to the structure.
This would be in accord with the interpretation of the
dark stains in Chengjiangocaris longiformis as gut
diverticulae. There is also a correspondence in the
overall shape of these stains with the structures in
Fuxianhuia protensa. Apart from that, the limb interpretation suffers from two shortcomings. First, the
structure never extends from underneath the shieldlike tergite, which might be expected in the case of a
limb, and proponents of the limb interpretation fail to
497
explain the layer of cuticle occurring underneath the
structure (Waloszek et al., 2005). That an appendage
is covered ventrally by a large sclerite, possibly the
hypostome (Budd, 2008), seems highly unusual, and,
given that the size of this sclerite or hypostome was
based on conjecture, casts further doubt on this explanation. Second, there are no signs of regular segmentation and pivot joints in the structure, although
these are preserved in the other limbs of the same
taxon (e.g. Hou & Bergström, 1997: figs 8A, 11D).
Furthermore, it is striking that among the three
stem-lineage euarthropods Fuxianhuia protensa,
Chengjiangocaris longiformis, and S. zhenghei, the
structure is known only from Fuxianhuia protensa.
Finally, apart from size and armature, the morphology of the antennula in K. soperi gen. et sp. nov. is in
accord with the morphology of the antennule of Fuxianhuia protensa, as identified by Waloszek et al.
(2005). The morphology of the Furongian Agnostus
pisiformis (Wahlenberg, 1818) is important in this
context, as it, too, has an antennula composed of a
peduncle and about 15 articles that was mainly
involved in nutrition (Müller & Walossek, 1987).
Agnostus pisiformis has more recently been interpreted to represent the sister taxon of Crustacea s.l.
or Mandibulata (Stein, Waloszek & Maas, 2005), and
thus demonstrates that this antennula design was
plesiomorphically retained in the ground pattern of
Euarthropoda (Waloszek et al., 2007).
AFFINITIES
OF
KIISORTOQIA
SP. NOV.
SOPERI GEN. ET
Kiisortoqia soperi gen. et sp. nov. exhibits three characters that are considered to be part of the ground
pattern of Euarthropoda (Waloszek et al., 2007).
1. A head incorporating the antennular plus three
limb-bearing segments.
2. Postantennular limbs with a rigid, anteroposteriorly flattened, spine-bearing basipod, extended
mediodistally into the endopod, and carrying the
exopod on its lateral sloping edge.
3. A flap-like exopod fringed with setae.
Consequently, K. soperi gen. et sp. nov. rests comfortably within the Euarthropoda. The position within
Euarthropoda, however, is difficult to resolve because
of the many plesiomorphies of K. soperi gen. et sp.
nov. The potential absence of eyes and the trilobate,
semicircular tail shield may represent autapomorphies. None of the known arthropod taxa with ‘great
appendages’ has such a tail shield, but a somewhat
similar tail can be found in trilobite-like taxa, where
it frequently includes limb-bearing segments, forming
the pygidium. Apart from the tail shield, there is,
however, no character that would support the affini-
© 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 477–500
498
M. STEIN
ties of K. soperi gen. et sp. nov. with trilobites or allied
taxa. According to Chen et al. (2004) and Maas et al.
(2004), the large, potentially raptorial antennula may
represent a synapomorphy with Chelicerata, but a
true raptorial function remains speculative, and a
mere function in food gathering of the antennula is
considered to be a ground-pattern character of Arthropoda s.s., retained e.g. in the ground pattern of Crustacea (Waloszek et al., 2007). Scholtz & Edgecombe
(2006) considered even a large, raptorial antennula
to be part of the ground pattern of Euarthropoda,
although this assumption is based partly on equivocal
data from Fuxianhuia protensa (see above). Resolving
the phylogenetic position of anomalocaridids should
help to settle this issue, but their phylogenetic position remains controversial (Chen et al., 2004; Scholtz
& Edgecombe, 2006), mainly because of the insufficient preservation of the material available. The
phylogenetic position of K. soperi gen. et sp. nov.,
therefore, cannot be resolved at present.
CONCLUSIONS
On balance, the present data seem to support the
homology of the ‘great appendage’ of anomalocaridids
with the ‘short great appendage’ of megacheirans. By
extension, homology with the limb of the deutocerebral segment of Euarthropoda seems most tenable,
as advocated by Chen et al. (2004), Waloszek et al.
(2005), and Scholtz & Edgecombe (2006). This contrasts with the hypothesis advanced by Budd (2002),
which assumes homology of the ‘great appendage’ of
‘anomalocaridids’ and the ‘short great appendage’ of
megacheirans with the palp-like ‘frontal appendage’
of the Sirius Passet taxa Kerygmachela kierkegaardi
and Pambdelurion whittingtoni, the Burgess Shale
tardipolypod Aysheaia pedunculata Walcott, 1911,
and the (protocerebral) palp of extant Onychophora.
Given the homology of the uniramous limb of K.
soperi gen. et sp. nov. with the anomalocaridid ‘great
appendage’, this would require transformation or loss
of this latter appendage, in addition to an originally
biramous antennula being secondarily transformed
into an uniramous limb: a scenario for which there is
little evidence. The homology of the ‘great appendage’
with the antennula of other arthropods is also in
accord with a food-gathering antennula in the ground
pattern of Euarthropoda (Waloszek et al., 2005;
Scholtz & Edgecombe, 2006; Waloszek et al., 2007).
Whether or not the antennula in that ground pattern
was a specialized raptorial appendage (Scholtz &
Edgecombe, 2006) is not clear, as this is coupled with
the question of the phylogenetic position of such taxa
as Anomalocaris saron or Amplectobelua symbrachiata, which remain problematic until better material is available.
The phylogenetic position of K. soperi gen. et sp.
nov. has to remain unresolved at present, because of
the many euarthropod plesiomorphies possessed by
the taxon. This in itself is interesting, as it may
indicate a very basal position of the species, and it
once more demonstrates the importance of fossils in
characterizing ground patterns.
ACKNOWLEDGMENTS
I am indebted to John S. Peel, Uppsala, for access to
the material studied, facilities, and countless discussions on the Sirius Passet fauna in general, and the
studied material in particular, as well as for corrections to the English in the manuscript. Valuable discussions and suggestions on arthropod morphology
and phylogeny, on the present material, and comments on various versions of the manuscript were
provided by Dieter Waloszek and Andreas Maas, both
from Ulm. Reinhardt M. Kristensen, Copenhagen,
and David J. Siveter, Leicester, provided stimulating
remarks on the material and the manuscript. Two
anonymous referees have also helped to improve the
quality of this contribution.
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