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Houcaris gen. nov. from the early Cambrian (Stage 3) Chengjiang Lagerstätte expanded the palaeogeographical distribution of tamisiocaridids (Panarthropoda: Radiodonta)


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Radiodonts were cosmopolitan and diverse stem-euarthropods that have been generally regarded as the apex Cambrian predators. Four major groups have been distinguished including tamisiocaridids, primarily based on the endite features of the frontal appendages. Anomalocaris saron Hou, Bergström and Ahlberg, 1995, one of the most well-known radiodonts in the Chengjiang Lagerstätte, is generally treated as a member of the Family Anomalocarididae. New anatomical evidence reported here, allied with the data of microcomputed tomography (CT) shows that the endites in A. saron are paired, much longer than the height of associated podomeres, and furnished with multiple slender distal auxiliary spines. These new observations allow us to reassign A. saron to a new genus, Houcaris gen. nov., and strongly support its tamisiocaridid affinities rather than anomalocaridid as previously suggested. Houcaris saron thus represents the first tamisiocaridid species known from South China, as well as the oldest tamisiocaridid in the fossil record (Cambrian Stage 3). Our occurrence data, coupled with other distribution of tamisiocaridids, demonstrates that this group is restricted to the early Cambrian (Series 2), and occur across South China, Laurentia and eastern Gondwana within tropics/subtropics belt, indicating a possible climatic control on their distribution. Moreover, these tamisiocaridid records documented in several Konservat Lagerstätten suggest an ecological preference to shallow water environment with well-oxygenated sea bottom conditions.
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1 3
Houcaris gen. nov. fromtheearly Cambrian (Stage 3) Chengjiang
Lagerstätte expanded thepalaeogeographical distribution
oftamisiocaridids (Panarthropoda: Radiodonta)
YuWu1· DongjingFu1· JiaxinMa1· WeiliangLin1· AoSun1· XingliangZhang1
Received: 5 August 2020 / Accepted: 28 December 2020
© Paläontologische Gesellschaft 2021
Radiodonts were cosmopolitan and diverse stem-euarthropods that have been generally regarded as the apex Cambrian
predators. Four major groups have been distinguished including tamisiocaridids, primarily based on the endite features of
the frontal appendages. Anomalocaris saron Hou, Bergström and Ahlberg, 1995, one of the most well-known radiodonts in
the Chengjiang Lagerstätte, is generally treated as a member of the Family Anomalocarididae. New anatomical evidence
reported here, allied with the data of microcomputed tomography (CT) shows that the endites in A. saron are paired, much
longer than the height of associated podomeres, and furnished with multiple slender distal auxiliary spines. These new
observations allow us to reassign A. saron to a new genus, Houcaris gen. nov., and strongly support its tamisiocaridid affini-
ties rather than anomalocaridid as previously suggested. Houcaris saron, thus, represents the first tamisiocaridid species
known from South China, as well as the oldest tamisiocaridid in the fossil record (Cambrian Stage 3). Our occurrence data,
coupled with other distribution of tamisiocaridids, demonstrate that this group is restricted to the early Cambrian (Series 2),
and occur across South China, Laurentia and eastern Gondwana within tropics/subtropics belt, indicating a possible climatic
control on their distribution. Moreover, these tamisiocaridid records documented in several Konservat Lagerstätten suggest
an ecological preference to shallow water environment with well-oxygenated sea bottom conditions.
Keywords Radiodonta· Tamisiocaridid· Houcaris gen. nov.· Biogeography· Chengjiang biota· Computed tomography
Radiodonta Collins, 1996 is a clade of stem arthropods
(sensu Ortega-Hernandez 2016) that have generally been
regarded as large apex predators of the Cambrian and Ordo-
vician Periods (e.g. Briggs 1994; Chen etal. 1994; Whit-
tington and Briggs 1985; Daley and Budd 2010; Paterson
etal. 2011;Daley etal. 2013a, b; Daley and Edgecombe
2014; Van Roy etal. 2015; Liu etal. 2018). These animals
are typified by paired grasping frontal appendages with a
series of morphologically diverse endites, radial mouthparts,
prominent dorsolateral compound eyes on stalks, a series of
flexible lateral flaps along its dorsoventrally flattened body
and tail fans. Frontal appendages are the most commonly
preserved element of radiodonts owing to their sclerotised
nature, and thus, these structures played a key role in under-
standing radiodonts taxonomy and ecology. Primarily on
the basis of the organisation of frontal appendages, four
major groups have been distinguished, including the fami-
lies Anomalocarididae Raymond, 1935, Amplectobeluidae
Pates etal.2019b, Tamisiocarididae Pates and Daley, 2019
and Hurdiidae Lerosey-Aubril and Pates, 2018. As one of
the four families of radiodonts, the Family Tamisiocaridi-
dae is characterised by a pair of frontal appendages bearing
elongate and thin endites with numerous auxiliary spines.
To date, tamisiocaridids contains only Tamisiocaris borealis
Daley and Peel, 2010, Anomalocaris briggsi Nedin, 1995,
and possible Tamisiocaris aff. borealis (Pates and Daley
Recent phylogenetic analyses exploring radiodont inter-
relationships have produced incompatibility with the tra-
ditional taxonomy of the genus Anomalocaris, with A.
Handling editor: Mike Reich.
* Dongjing Fu
1 State Key Laboratory ofContinental Dynamics andShaanxi
Key Laboratory ofEarly Life andEnvironments, Department
ofGeology, Northwest University, Xi’an710069, China
Y. Wu etal.
1 3
kunmingensis retrieved within the Amplectobeluidae, and
A. briggsi within the Tamisiocarididae, leaving Anomalo-
caris to be polyphyletic (Van Roy etal. 2015; Liu etal. 2018;
Lerosey-Aubril and Pates 2018). Anomalocaris saron Hou,
Bergström and Ahlberg, 1995, a classic radiodont species
from the well-known Chengjiang Lagerstätte (Cambrian
Series2, Stage 3), was originally described 25years ago
(Hou etal. 1995). Several researchers have illustrated frontal
appendage material of A. saron, nevertheless, new anatomi-
cal features have yet been well studied (Cong etal. 2018;
Guo etal. 2018; Pates etal. 2019b), and then no more data
have been involved in the subsequent phylogenetic analysis
of Lerosey-Aubril and Pates (2018). Therefore this taxon
is still generally treated as a member of the Family Anom-
alocarididae (e.g., Van Roy etal. 2015; Liu etal. 2018;
Pates etal. 2019b). In this contribution, we have studied
new material of this species, drawing on microcomputed
tomography (CT) study, to elucidate morphological details
of frontal appendage that forces the assignment of A. saron
to tamisiocaridids rather than anomalocaridids. Our work
herein also adds to spatio-temporal distributional data on
tamisiocaridid radiodonts and evaluate palaeogeographic
distribution patterns and habitat preferences of this group.
Materials andmethods
The studied appendage specimens documented here were
collected from seven localities (Ercai, Erjie, Jianshan,
Sanjiezi, Mafang and Haoyicun) of the Cambrian (Stage
3; locally Qiongzhusian) Yu’anshan Member of the Chi-
ungchussu Formation in eastern Yunnan Province, China,
which falls within the Eoredlichia–Wutingaspis Trilobite
Zone (Hou etal. 2017; Zhang etal. 2017). The material is
deposited in the Shaanxi Key Laboratory of Early Life and
Environments (LELE) and Department of Geology, North-
west University (NWU), Xi’an, China.
All specimens here were gathered from split slabs of
mudstones, and a few specimens were further prepared
with fine needles under high magnification using stereomi-
croscopes. Fossils were photographed with a Canon EOS
5D Mark II digital camera and images processed in Adobe
Photoshop CS 6. Camera lucida drawings were made
using a Zeiss Discovery V12 microscope and prepared
with Corel Draw X4. Measurements were measured from
specimen digital photographs using ImageJ freeware (https
://image .html). X-ray micro-computed
tomography (CT) was used to reveal ventral structures
concealed within the rock matrix (e.g., Chen etal. 2019;
Zhai etal. 2019a, b, c; Liu etal. 2020). Specimen scanning
was performed by Zeiss X-radia 520 Versa for MF-002.
Each scan generated a set of radiographs saved as TIFF
stacks which were further processed with the DRAGON-
FLY 4.1 software (http://www.theob jects .com). The 3D
models rendered in Dragonfly were screen-captured as
images in the figures.
Terminology and abbreviations. As listed in Table1, the
morphological terms used in the description of radiodont
frontal appendages vary considerably. For accuracy and sim-
plicity, we here give a new description scheme for radiodont
frontal appendages.
Radiodonts frontal appendages consist of a series of
podomeres bearing a diverse morphology of endites along
their length and can be separated into two major regions:
the ‘base’ and ‘claw’. The anatomical term ‘base’ follows
Maddocks (2000), which is employed herein to designate the
proximal enlarged peduncular portion of frontal appendages
bearing no endite or reduced endite. And the term ‘claw’ fol-
lows Haug etal. (2012), which refers to the region distal to
the ‘base’ bearing relatively large and sophisticated endite.
The previously used terms ‘shaft’ (Hou etal. 1995; Cong
etal. 2018) and ‘distal articulated region’ (defined by Cong
etal. 2018) were not preferred over ‘base’ and ‘claw’ as they
have various meanings and are generally applied to tools,
not organs (Lerosey-Aubril and Pates 2018). The bound-
ary between the ‘base’ and ‘claw’ of the frontal append-
age can often be identified by the presence of an angle on
the dorsal surface of the frontal appendage, and the mor-
phology and position of endites (Pates etal. 2019a). And
thus, the ‘base podomere’ and ‘claw podomere’ refer to the
podomeres of base and claw respectively. Significantly, the
term ‘endite’ (defined by Boxshall 2004) initially refers to
the inner spinose or setose inner lobe of Arthropoda postan-
tennulary limb, we here extend this term to the radiodont
frontal appendages.
Table 1 List of morphological terms of radiodont frontal appendages used in previous works and this study
Briggs (1979) Hou etal. (1995) Haug etal. (2012) Cong etal. (2018) Liu etal. (2018) Pates etal. (2019a) This study
Shaft Peduncle Shaft Appendage
Shaft Base
Claw Distal articulated
Distal articulated
Ventral spine Endite Spine Endite Endite Endite Endite
Houcaris gen. nov. from the early Cambrian (Stage 3)
1 3
The other descriptive terminology mainly follows that of
Cong etal. (2018) and Pates etal. (2019a). ‘Auxiliary spine’
refers to the small spine located on the lateral margins of endite.
‘Terminal spines’ are spines at the distal end of the appendage.
Cp1–X refers to claw podomeres 1 to X, Bp1–3 refers to base
podomeres 1–3, and the numbering reflects a proximal–distal
axis. And En1–EnX refer to endites on Cp1–CpX.
The terminology essentially follows Briggs (1979) for its
orientation. Proximal (toward the base of the frontal append-
age) and distal (away from the base of frontal appendage) are
used here in their customary sense to designate directions
within the front appendage. Thus, the ‘distal auxiliary spine’
and ‘proximal auxiliary spine’ refer to the auxiliary spine
occurring on the distal and proximal margin of an endite,
respectively. The height of podomere refers to the distance
between its dorsal and ventral margins, and its length refers
to the distance between its boundaries with the preceding
and following podomeres.
Systematic palaeontology
Superphylum Panarthropoda Nielsen, 1995
Phylum (stem-group) Euarthropoda Lankester, 1904
Order Radiodonta Collins, 1996
Family Tamisiocarididae Pates and Daley, 2019
Type genus. Tamisiocaris Daley and Peel, 2010; from the
early Cambrian (Series 2, Stage 3) Sirius Passet Fauna of
North Greenland.
Revised diagnosis. Radiodonts with frontal appendages
bearing paired thin endites much longer than the height of
the associated podomeres; endites on proximal and inter-
mediate claw podomeres bearing multiple slender auxiliary
spines (modified from Pates and Daley 2019).
Remarks. In original description, the appendage endites of
the Family Tamisiocarididae are subequal rather than alter-
nating in length, which are well represented by Tamisiocaris
and Anomalocaris briggsi. Our present material indicates
that the appendage endites of tamisiocaridids could also
alternate long/short on odd/even numbered claw podomeres.
Compared to the arrangement of endites, the elongate
endites, slender and dense auxiliary spines are what really
matters to the filter-feeding of tamisiocarids. And thus, the
presence of the subequal endites is no longer treated as the
diagnostic character of the Tamisiocarididae. The family
hitherto comprises Houcaris gen. nov., Tamisiocaris Daley
and Peel, 2010, and Anomalocaris briggsi Nedin, 1995.
Genus Houcaris nov.
Etymology. Named after Professor Xianguang Hou for his
contributions to early research on the Chengjiang biota and
Chengjiang radiodonts; and ‘caris’ meaning ‘crab’, a com-
monly used suffix for marine euarthropods.
Type species. Houcaris saron (Hou etal., 1995); from the
Chengjiang biota (Series 2, Stage 3) of eastern Yunnan,
South China.
Diagnosis. Tamisiocaridids with paired elongate, distally
tapered frontal appendages consisting three base podomeres
and 13 claw podomeres; claw podomeres in proximal and
intermediate region bear paired elongate endite altering
long/short on odd/even numbered claw podomeres, each of
which processes multiple distal auxiliary spines; En1 stout
and slightly curved; claw podomeres are separated by trian-
gular flexible arthrodial membrane.
Remarks. Anomalocaris magnabasis (previously Anomalo-
caris cf. saron) from the Pioche and Carrara Formations of
Nevada, USA (Pates etal. 2019b; see also Lieberman 2003)
is reassigned to the new genus Houcaris as it also bears the
long and thin endites with fine distal auxiliary spines and
the same number of claw podomeres as seen in H. saron
(see discussion below). The two-part structure of endites is
recognised in H. magnabasis by Pates etal. (2019b). How-
ever, the argumentation of presence of two-part structure
merely based on the different colouration and morphological
differences in different preservation stage, and the authors
did not give further exhaustive description or key anatomi-
cal information of the endites of this feature (e.g. articu-
lation between endite base and the distal spine or simple
boundary). Moreover, the same research concerning the two-
part structure in other radiodont families (tamisiocaridids,
amplectobeluids and hurdiids) remains scanty. Therefore,
we here consider that the two-part structure in Anomalocaris
and Houcaris magnabasis as a taphonomic artefact rather
than a morphological characteristic. And thus, this character
does not appear to be of systematic value and is excluded
from the diagnosis of this genus.
Occurrence. Stage 3 (Chengjiang, China) and Stage 4
(the Pioche and Carrara Formations, USA) of Cambrian
unnamed Series 2.
Assigned species. Houcaris saron (Hou, Bergström and Ahl-
berg, 1995) and Houcaris magnabasis (Pates, Daley, Edge-
combe, Cong and Lieberman, 2019b).
Y. Wu etal.
1 3
Houcaris gen. nov. from the early Cambrian (Stage 3)
1 3
Houcaris saron (Hou, Bergström and Ahlberg, 1995)
Figures1, 2, 3
1995 Anomalocaris saron sp. nov. Hou etal.: 166–167,
figs.2a–f; fig.3b, c; fig.4.
1996 Anomalocaris saron—Chen etal.: 197–198, fig.266.
2017 Anomalocaris saron—Hou etal.: 154–155, fig.19.1.
2018 Anomalocaris saron—Cong etal.: fig.5c, f.
2018 Anomalocaris saron—Guo etal.: fig.2f.
2019b Anomalocaris saron—Pates etal.: fig.12A.
Material examined. Holotype: EC-0036AB. Paratype:
SJZ-400AB. Other specimens: EC-007, JS-0048AB,
JS-0187AB, JS-0763AB, JS-1073AB, EJ-1906AB, EJ-
1911AB, EC-2296AB, MF-002, MF-1136AB, MF-1257AB,
MF-1136AB, MF-1257AB, HY-1795AB, HY-1807, HY-
1795AB, HY-1807, SJZ-261AB, SJZ-400AB, SJZ-534AB,
SJZ-537AB, SJZ-581AB, SJZ-261AB, SJZ-400AB, SJZ-
534AB, SJZ-537AB, SJZ-581AB.
Emended diagnosis. Houcaris with elongate distally taper-
ing frontal appendage consisting of 16 podomeres, including
three base podomeres and 13 claw podomeres; Cp2–Cp8
nearly square, Cp9–Cp12 rectangular and much longer than
height; En2–En8 at least one and a half times as long as
the height of the associated podomeres, and bear 5 distal
auxiliary spines and 2 proximal auxiliary spines; auxiliary
spines near the base part of endite are shorter; En1 stout and
ventro-distally curved; two smaller setules projected from
distal ventral surface of each claw podomere; Cp10–Cp13
project paired elongate dorsal spines arching forward; Cp13
also bearing one terminal spine and a pair of secondary dor-
sal spines (Modified from Hou etal. 1995).
Description. The frontal appendages are elongate, slender
and moderately narrowing distally. Frontal appendages range
in length from 1.7cm to at least 12cm (Figs.1, 2), as meas-
ured along the outwardly convex dorsal margin from the
proximal margin of proximal base to the distal extremity of
the appendage. The frontal appendages are almost incom-
pletely preserved in lateral aspect. Rare complete specimens
are known, which consist of a three-segmented base and a
13-segmented claw (Fig.2i). The base podomeres are both
higher and longer than the claw podomeres. The base is
angled at 127–145 degree to the claw on the dorsal surface
(Figs.1, 2). In SJZ-261, one tiny endite projects from the
ventral region of Bp1 (be in Fig.2g). The proximal claw
podomeres (Cp2–Cp8) length/height ratio ranges from 0.8
to 1; whereas in distal claw podomeres (Cp9–Cp12), the
length/height ratio more than 1.5. The proximal margin of
each podomeres, apart from the first (outwardly convex), was
straight and inclined at about 80° to the dorsal margin of the
appendage. The result of CT shows the endites are paired per
claw podomere (Fig.2d, e). En1 are stout, ventrally curved
flanked by two relative large auxiliary spines (Fig.2f–g). In
Cp2–Cp12, elongate thin endites differ in the way they pro-
ject on podomeres and in their orientation relative to them.
On Cp2–Cp7 of the holotype, the endites project proximally
from the proximal half of the podomere at an angle of c.
75–85° (relative to the long axis of the appendage; Figs.1,
2). On the contrary, En8–En12 project distally from the dis-
tal half of the podomere at a decreasingly low angle relative
to the ventral margins (these angles might be distorted dur-
ing preservation). The endites are quite elongate and at least
one and a half times as long as the height of the associated
podomeres (Figs.1a–e, 2a–h). Endites alternate long/short
on odd/even-numbered claw podomeres, reducing distally in
length (Figs.1a, b, d, e, 2a, b, h, i). The number of auxiliary
spines on distal edge of endites is variable and increases dis-
tally along the appendage, and the proximal edge of endites
bears two auxiliary spines. En2–En8 bear 5 distal auxiliary
spines; whereas, En9–En12, only bear one distal auxiliary
spines (Figs.1c, 2a, b). En2–En12 bear 2 proximal auxiliary
spines, which projected from the half length of the endites.
No evidence that these single auxiliary spines are in pair
has been observed. Apparently, some variation in the posi-
tion of the proximal auxiliary spines, but in the proximal
claw podomeres they tend to protrudes from about the mid-
length of the endite; whereas, they project from near the base
of the endite in the more distal claw podomeres. In some
specimens, two small closely pitched setules project from
the distal ventral surface of claw podomeres, ranging from
1 to 2.5mm in length (see in Figs.1c–d, 2a–e, g, h). Cp12
bears one simple endite without auxiliary spines (Fig.2a,
c). In SJZ-261, a series of small protuberances present at
the base of endites on the podomere’s ventral surface (white
arrows in Fig.2f). In JS-1073, Cp12 bears a pair of dorsal
spines (Fig.2j). The dorsal spines arch forwards and extend
generally parallel to the dorsal margin of the podomere. The
distal end of the appendage is ventrally curved and narrow,
Cp13 (most distal claw podomere) also bears one terminal
spines and a pair of secondary dorsal spines (sds and ts in
Cp13 in Fig.2j).
Fig. 1 Houcaris saron (Hou, Bergström and Ahlberg, 1995) from
the Chengjiang biota, South China (Series 2, Stage 3). Frontal
appendages in lateral aspect. a and d part and countpart of holotype,
EC-0036, nearly complete appendage, showing the elongate and thin
endites furnished with multiple distal auxiliary spines. b and e cam-
era lucida drawing of a and D. c close-up of En4 (boxed in a), show-
ing the five distal auxiliary spines (solid black arrows) on the elon-
gate endite and two small setules on the distal ventral surface of claw
podomere. Am arthrodial membrane, Bp base podomere, Cp claw
podomere, das distal auxiliary spine, pas proximal auxiliary spine, se
setules. All scale bars represent 10mm
Y. Wu etal.
1 3
Fig. 2 Houcaris saron (Hou, Bergström and Ahlberg, 1995) from the
Chengjiang biota, South China (Series 2, Stage 3). Frontal append-
ages in lateral aspect. a part of MF-002 appendage showing elongate
and thin endites on proximal and middle claw podomeres. b close-
up of MF-002 part (boxed in a), showing two small setules originate
from distal ventral surface close to En6. c camera lucida drawing of
a. d Three-dimensional computer models derived from a micro-CT
scan of MF-002, showing the paired endites per claw podomeres.
e white box e in d showing small setules and the detail features of
endites. f, g part of SJZ-261 appendage with camera lucida drawing
of f showing proximal part of appendage. White solid arrows indicat-
ing the small protuberances near the base of endites on the ventral
surface. h SJZ-400, nearly complete appendage, showing the elongate
endites. i JS-1073, nearly complete appendage, showing three base
podomeres and 13 claw podomeres. j close-up of JS-1073 (boxed in
i), showing paired dorsal spines on Cp12 and paired secondary dor-
sal spines on distalmost claw podomere. As auxiliary spines, be base
podomere endite, EnL left endite, EnR right endite, sds secondary
dorsal spine. Scale bars represent: 5mm (a, ci), 1mm (b, j)
Houcaris gen. nov. from the early Cambrian (Stage 3)
1 3
Remarks: The new Chengjiang material illustrated herein
allows us to provide more detail anatomical information.
Despite several recent studies have illustrated Houcaris
saron appendage material (e.g. Cong etal. 2018; Guo etal.
2018; Pates etal. 2019b), no diagnosis and formal descrip-
tion concerning this taxa have yet been provided after its
original description (Hou etal. 1995), in which the append-
age endites only bear two pair of auxiliary spines, whereas
the present material shows that the majority of endites bear
five slender distal auxiliary spines and two proximal auxil-
iary spines. The previously illustrated specimen shows that
En1 also bears at least five distal auxiliary spines (Guo etal.
2018: fig.2f, g), which is obscure in our new specimens. Our
observation also further unequivocally excludes the possibil-
ity of the reconstruction of one proximal base podomere and
fifteen claw podomeres (Chen etal. 2004; Lerosey-Aubril
etal. 2014: fig.3) and two base podomeres and 14 claw
podomeres (Hou etal. 1995, 2017). Moreover, the specimen
illustrated by Chen etal. (1994) was previously treated as H.
saron (Hou etal. 1995). We here consider this specimen is
not H. saron owing to its less auxiliary spines and relative
short endites (Chen etal. 1994: fig.1b, c). Microcomputed
tomographic (micro-CT) scanning provides solid evidence
to substantiate the presence of paired endites in H. saron
for the first time (Fig.2d, e), and further reconfirms that
the presence of paired endites remains a consistent trait of
the Tamisiocarididae and indeed a characteristic feature of
Radiodonta (Pates etal. 2019a).
Occurrence. Cambrian Series 2, Stage 3, Yu’anshan Mem-
ber, Chiungchussu Formation, EoredlichiaWutingaspis
trilobite biozone (Jianshan, Mafang, Ercai, Erjie, Sanjiezi,
Haoyicun), eastern Yunnan, South China.
Houcaris gen. nov. asamember ofTamisiocarididae
Houcaris saron (Hou, Bergström and Ahlberg, 1995) (pre-
viously Anomalocaris saron) is unequivocally identified as
Tamisiocarididae as presently defined (see also original defi-
nition of this family in Pates and Daley 2019) by the diag-
nostic features of frontal appendage, including the multiple
podomeres, elongate and tapering outline, paired elongate
endites that much longer than the height of the associated
podomeres and multiple slender distal auxiliary spines.
H. saron can be easily distinguished from the members
of Amplectobeluidae and Hurdiidae, since the former was
characterised by hypertrophied endite and simple spine-like
endites devoid of auxiliary spines, and the latter by blade-
like endites.
This species has been traditionally considered as a repre-
sentative of the Family Anomalocarididae (e.g. Hou etal.
1995; Cong etal. 2018; Guo etal. 2018; Pates etal. 2019b).
However, the presence of longer endites with multiple aux-
iliary spines of this taxon is extremely differs from the rep-
resentatives of Anomalocarididae, such as Anomalocaris
canadensis Whiteaves, 1982, Anomalocaris cf. canadensis
from Emu Bay Shale (Daley etal. 2013b) and Anomalocaris
Fig. 3 Artistic reconstruction of the frontal appendage of Houcaris
saron, showing a series podomeres bearing paired elongate and thin
endites furnished with multiple distal auxiliary spines. Drawing by
Daowen Lv, copyright Shaanxi Key Laboratory of Early Life and
Environments; used with permission. Not to scale
Y. Wu etal.
1 3
aff. canadensis from the Weeks Formation of USA (Lerosey-
Aubril etal. 2014). Although the characteristic alteration
of long and short endites in anomalocaridids and amplec-
tobeluids is also present in Houcaris, the difference in
length between adjacent long and short endites in proxi-
mal podomeres is quite unconspicuous in H. saron. And the
minute difference in endite length would not prevent their
appendages from forming a basket shape when they are bent
and pulled toward mouth for filter-feeding. Whereas, in typi-
cal anomalocaridids and amplectobeluids, the long endites
are apparently longer than the adjacent short endites, such
as Anomalocaris canadensis (Daley and Edgecombe 2014:
figs.12.7, 13.4), Anomalocaris pennsylvanica (see Pates and
Daley 2019: fig.3, fig.6a), Amplectobelua symbrachiata
(see Cong etal. 2017: fig.2d). Despite Houcaris bears simi-
larity with anomalocaridids in the arrangement of endites,
the substantially morphological differences of endites (e.g.
length, arrangement and morphology of auxiliary spines)
prompt the exclusion of Houcaris from Anomalocarididae.
And the alteration of long and short endites is no longer
restricted to anomalocarids and amplectobeluids.
Anomalocaris briggsi has constantly been retrieved within
the Tamisiocarididae in recent phylogenetic analyses
(Vinther etal. 2014; Van Roy etal. 2015; Lerosey-Aubril
and Pates 2018; Liu etal. 2018; Moysiuk and Caron 2019).
Compared to other radiodont taxa, the frontal appendage
of Houcaris bears closer resemblance to that of A. briggsi,
Fig. 4 Comparative sketches of tamisiocaridid radiodont frontal
appendages. a Houcaris saron (this study). b Houcaris magnaba-
sis (redrawn from Pates etal. 2019b). c Tamisiocaris borealis Daley
and Peel, 2010 (redrawn from Pates and Daley 2019). d Tamisiocaris
aff. borealis (redrawn from Pates and Daley 2019). e ‘Anomalocaris’
briggsi Nedin, 1995 (redrawn from Daley et al. 2013b). Compare
to H. magnabasis, H. saron the ratio of height/length of each claw
podomeres is much lower, and the length of endites relative to claw
podomere height is higher. Further, H. saron does not well display
the two-part structure of endites as seen in H. magnabasis. Compared
to ‘Anomalocaris’ briggsi, Houcaris possesses less and more robust
auxiliary spines. Houcaris also can be differentiated from Tamisio-
caris not only by the less podomeres, but also by the endites being
shorter relative to podomere height, and by the much less auxiliary
Houcaris gen. nov. from the early Cambrian (Stage 3)
1 3
since both of them have slender and distally tapering mor-
phology, and the number of claw podomeres in H. saron
(13; Figs.1, 3) is close to that in A. briggsi (14; Fig.4e).
More importantly, the length of endites relative to podomere
height in Houcaris (endite length:podomere height ratio
is c. 1.5) is quite comparable to that in A. briggsi (endite
length:podomere height ratio is c. 1.6; Fig.4e; see also
Daley etal. 2013b: figs.1, 2). These similarities between
H. saron and A. briggsi support the tamisiocaridid affinities
of Houcaris.
More recently, Pates etal. (2019b) reinterpreted Anom-
alocaris cf. saron Lieberman (2003) as Anomalocaris
magnabasis from the Pioche and Carrara Formation of
Nevada, USA. In the light of the anatomical features of
the frontal appendages in A. magnabasis, such as long and
thin endites with fine distal auxiliary spines and the same
number of claw podomeres as seen in Houcaris saron, we
here reinterpret this American species as Houcaris magna-
basis within the Family Tamisiocarididae. Compared to H.
saron, the ratio of height/length of each claw podomeres
in H. magnabasis is much higher, and the length of endites
Fig. 5 Distribution of the Family Tamisiocarididae during the Cam-
brian. a, Stratigraphical distribution, showing tamisiocaridids are
restrict to Cambrian Series 2 (the early Cambrian). b, Palaeobiogeo-
graphical distribution, indicating tamisiocaridids occur across South
China, Laurentia and eastern Gondwana within a relatively narrow
tropical belt. Palaeocontinental reconstructions during the early Cam-
brian time redrawn, modified and simplified by Torsvik and Cocks
(2013: fig. 2.7). Each taxon indicated by specific number. Numbers
in a correspond to those plotted in b. References for different tamisio-
caridid radiodont taxa: 1 = Daley and Peel (2010) and Vinther et al.
(2014); 2 = Pates and Daley (2019); 3 = Nedin (1995) and Daley etal.
(2013b); 4 = Hou et al. (1995) and this study; 5 = Lieberman (2003)
and Pates etal. (2019b). Ca the Carrara Formation, Cj the Chengji-
ang biota, EBS Emu Bay Shale, K the Kinzers Formation, P the
Pioche Formation, SP the Sirius Passet biota
Y. Wu etal.
1 3
relative to claw podomere height is lower. Further, H.
magnabasis apparently displays the two-part structure of
endites (Pates etal. 2019b). Therefore, H. saron from the
Chengjiang biota extends the paleogeographical range of
this genus outside of Laurentia for the first time, and also
constitutes the oldest occurrence for this genus (Cambrian
Stage 3). The occurrence also suggests a palaeobiogeo-
graphical connection between soft-bodied faunas from the
early Cambrian of geographically disparate South China and
western Laurentia.
In the context of the Family Tamisiocarididae, Houcaris
gen. nov. also resembles Tamisiocaris borealis and Anom-
alocaris briggsi in having paired elongate endites with
multiple slender auxiliary spines. Moreover, in Houcaris,
the endite in the distal podomere is miniaturised as seen
in A. briggsi (Daley etal. 2013b: figs.1, 2). In Houcaris,
however, the endites are alternating long and short, whereas
for T. borealis and A. briggsi, the endites are subequal in
length. Furthermore, the auxiliary spines in Houcaris are
much less than those in T. borealis and A. briggsi (Table2;
Daley etal. 2013b; Vinther etal. 2014; see also Lerosey-
Aubril and Pates 2018). Houcaris also can be differentiated
from Tamisiocaris (Vinther etal. 2014) not only by the less
podomeres, but also by the endites being shorter relative to
podomere height.
Spatio‑temporal distribution oftamisiocaridids
In addition to the newly erected genus herein, the Family
Tamisiocarididae by far contains Houcaris gen. nov. and
Tamisiocaris Daley and Peel, 2010, as well as Anomalocaris
briggsi Nedin, 1995. The biogeographical and temporal dis-
tribution of Tamisiocarididae is summarised in Fig.5.
The record of tamisiocaridids is restricted to the early
Cambrian (Series 2), occurring across South China (east-
ern Yunnan), Laurentia (USA and Greenland) and eastern
Gondwana (Australia) (Fig.4). Houcaris saron from the
Chengjiang biota and Tamisiocaris borealis Daley and Peel,
(2010) from the Sirius Passet fauna of North Greenland (see
also Vinther etal. 2014) represent the earliest fossil record
of tamisiocaridids, suggesting the emergence of tamisioca-
ridids in Cambrian Stage 3. After this early first appear-
ance, the tamisiocaridid fossil record continued sparse and
occurred in the west margin of Laurentia (Nevada, Penn-
sylvania) and eastern Gondwana (South Australia) at Stage
4, including Anomalocaris briggsi from Emu Bay Shale
of Australia (Pararaia janeae Zone; see also Daley etal.
2013b), Houcaris magnabasis from the Pioche Formation
(Eokochaspis nodosa zone and Nephrolenellus multinodus
zone) and Carrara Formation (Nephrolenellus multinodus
zone) of USA (Pates etal. 2019b), and possible Tamisiocaris
aff. borealis from the Kinzer Formation of Pennsylvania,
USA (Pates and Daley 2019). The occurrence of Houcaris in
geographically disparate South China and Laurentia during
the early Cambrian may reflect their relative strong capabili-
ties for dispersal in the water column, despite the lacking
of anatomical evidences (e.g. eyes, body flaps and tail fan).
Ultimately, this group virtually disappeared from the mid-
dle Cambrian rock record, which seems likely to represent
a true evolutionary absence, since the fossil record of other
radiodont families, are relative abundant in the depositions
of middle Cambrian, such as the Burgess Shale (e.g. Daley
and Budd 2010), Spence Shale (e.g. Briggs etal. 2008;
Table 2 Detailed comparison of frontal appendage characters of selected tamisiocaridid species
Y presence, N absence, U unknown, No number, Bp base podomere, Cp claw podomere, Ba base, Cl claw, En endite, aux auxiliary spine, d.a.s.
distal auxiliary spine, tm triangular membrane, dist distal, prox proximal
? indicates that thenumber of claw podomeres remains uncertain owing to the partial preservation
Houcaris saron Houcaris magnabasis Anomalocaris briggsi Tamisiocaris
No. of Bp 3 2 1 U
No. of Cp 13 13 14 ?18
Angle between Ba and Cl Y N Y N
Height:width ratio in proximal Cp 1.3:1 2.5:1 3:1 1.6:1
EnL/CpH on odd numbered Cp 1.7:1 1.4:1 1.6:1 2.5:1
Numerous aux Dist Dist Dist and prox Dist and prox
Max. no. of d.a.s 5 5 10 30
Rows of endites 2 2 2 2
Tm between Cp Y Y Y Y
En alternate long/short Y Y N N
Stout En1 Y Y N N
References This study Pates etal. (2019b) Daley etal. (2013b) Vinther etal. (2014)
Houcaris gen. nov. from the early Cambrian (Stage 3)
1 3
Daley etal. 2013a) and Wheeler Formation (e.g. Briggs
etal. 2008; Lerosey-Aubril etal. 2020). The demise of tami-
siocaridids at the end of Cambrian Stage 4, may have influ-
enced by factors that caused the mass extinction event of
archaeocyathids and redlichiid/olenellid trilobites (ROECE;
see Zhu etal. 2006) at the early–middle Cambrian boundary
(EMC), such as volcanically (Kurtz etal. 2003; Hough etal.
2006; Jourdan etal. 2014) or eustatically (e.g. Li etal. 2017;
Chang etal. 2017, 2019) associated expanded anoxia, as
well as the oligotrophic environment caused by aggravated
N loss as well as enhanced P input (Chang etal. 2019).
From a palaeogeographic point of view, tamisiocaridids
are present on South China, Laurentia (USA and Green-
land) and eastern Gondwana (Australia). This distribution
restricted to subtropical to tropical belt (Fig.4b) when plot-
ted on world maps based on palaeomagnetic data (Torsvik
and Cocks 2013), in contrast to Hurdiidae, which invade the
higher-latitude areas of the southern hemisphere (Baltica
and Avalonia) (Daley and Legg 2015; Pates etal. 2020).
Their latitudinal preference for the tropics/subtropics sug-
gests that tamisiocaridids may be warm-water animals that
controlled by changes in sea temperatures and climate zones.
Depositional environments
Tamisiocaridids in Konservat Lagerstätten provide further
evidence to suggest that tamisiocaridids have an ecological
preference to the shallow and well-oxygenated environment
(Table3). Houcaris magnabasis occurs from inner- (the
Pioche Formation, Nevada, USA; Pates etal. 2019b) to the
middle-shelf (the Carrara Formation, Nevada, USA; Pates
etal. 2019b) environment (Webster etal. 2008). H. saron
is preserved in the Chengjiang biota, which is generally
considered to have been deposited in shallow outer-shelf
settings (e.g. Hu 2005; Zhang etal. 2008; Hou etal. 2017)
with the fossils having been subjected to minimal transport
(Hou etal. 2004; Zhang and Hou 2007; Hou etal. 2017).
The presence of Anomalocaris briggsi Nedin, 1995 in the
Emu Bay Shale (Daley etal. 2013b) indicates that tami-
siocaridids could also survive in the nearshore, inner-shelf
shallow water environments. It seems to be that Tamisiocaris
represents an exception, with T. borealis being deposited
at the outer edge of the relict platform (Sirius Passet suc-
cession of Buen Formation; Daley and Peel 2010; Vinther
etal. 2014), and Tamisiocaris aff. borealis at a low energy
deep environment with intermittent, pulsed sedimentation
(Fine Pelitic Facies of the Emigsville Member of the Kinzers
Formation; Pates and Daley 2019). However, the sediment
from both two deposits was considered to be transported
from further shallow inboard or elsewhere (Skinner 2005;
Harper etal. 2019). It indicates that the organisms, including
Tamisiocaris in the depositional sites may be entombed far
away from their living environment. That is, Tamisiocaris
also likely to survive in shallow water environments and
probably the photic zone. Actually, tamisiocaridids have
generally been considered as filter-feeders, and then the low
oxygen deep marine settings would be unfavourable to pri-
mary producers and zooplanktons survival.
The detailed study of new material of Anomalocaris saron
from the Chengjiang biota leads a better understanding of
the appendage anatomy and sheds new light on the taxon-
omy of this important lower stem-group euarthropod. The
paired thin endites of this species are elongate, and bear
multiple slender auxiliary spines along its distal margin.
This character prompts a reassignment of A. saron to a new
genus, Houcaris gen. nov., and supports its tamisiocaridid
affinities. Houcaris saron gen. nov., together with Tamisio-
caris borealis from the Sirius Passet fauna of North Green-
land, represents the earliest fossil record of tamisiocaridids
around the world (Cambrian Stage 3). From the distribution
Table 3 The distribution of tamisiocaridid radiodonts from Konservat Lagerstätten representing different sedimentary environments
Fm Formation, Gu Guzhangian, Wu Wuliuan, H Houcaris, T Tamisiocaris
Biota Location Stage Environment Taxa References
Chengjiang Yunnan, South China 3 Offshore, outer part of broad clastic shelf;
below storm wave base
HThis study;
Hou etal. (1995)
Sirius Passet biota North Greenland 3 Shelf-slope break; below storm wave base TDaley and Peel (2010);
Vinther etal. (2014)
Pioche Fm Nevada, USA 4 Inner shelf HLieberman (2003);
Pates etal. (2019b)
Carrara Fm Nevada, USA 4 Middle shelf HPates etal. (2019b)
Kinzers Fm Pennsylvania, USA 4 Seaward of a carbonate shelf TPates and Daley (2019)
Emu Bay Shale Australia 4 Nearshore clastic setting; tectonic sub-basin Anomalo-
Daley etal. (2013b)
Y. Wu etal.
1 3
data of tamisiocaridids, this group is widespread longitudi-
nally but occurs within the tropical/subtropical regions dur-
ing the early Cambrian. This latitudinal preference implies
that tamisiocaridids may be warm-water animals that are
controlled by changes in sea temperatures and climate zones.
The discovery of tamisiocaridids in the Chengjiang biota
also provides support for the idea that these animals appear
to adapt to shallow water environments. The description
of biogeographic patterns and habitat preferences of other
radiodont groups (i.e. anomalocaridids, amplectobeluids and
hurdiids) is currently in preparation.
Acknowledgements We are grateful to Meirong Cheng, Cong Liu, Shu
Chai and Juanping Zhai at the Shaanxi Key Laboratory of Early Life
and Environments for joining in the fieldwork and the technical assis-
tance. We deeply appreciate the editor-in-chief Mike Reich (SNSB-
BSPG Munich) and one anonymous reviewer for their thoughtful and
constructive comments which greatly improved this manuscript. We
also would like to thank Hao Yun for discussion. Special thanks go
to Daowen Lv and Xi Liu (Northwest University Museum) for their
contribution to the reconstruction artwork, and Jie Sun and Yifei Sun
for scanning the fossils. This research was supported by the Natural
Science Foundation of China (41930319, 41772011, 41720104002,
41890844, 41621003), the Strategic Priority Research Program of
the Chinese Academy of Sciences (XDB26000000), and 111 Project
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... Key studies by Kühl et al. (2009) and Daley et al. (2009) used a phylogenetic approach to situate radiodonts in the lower stem lineage of Euarthropoda, indicating that their anatomical features provide insight into the acquisition of euarthropod morphological features. The identification of large cephalic carapaces in the Burgess Shale radiodont taxa Hurdia (Daley et al., 2009;Daley et al., 2013a) and Cambroraster (Moysiuk and Caron, 2019), consisting of a central element and two lateral elements (Figures 6A-E) (Supplementary Table S1A), meant that similar isolated carapaces in numerous Cambrian lagerstätten have found a home within Radiodonta (e.g., Sun et al., 2020a;Pates et al., 2021b) New discoveries of frontal appendages and oral cones have shown that these two anatomical features are highly variable in morphology within the clade, giving opportunities for reconstructions of their feeding paleoecology (Daley and Peel, 2010;Daley et al., 2013b;Vinther et al., 2014;Cong et al., 2016;Cong et al., 2017;Cong et al., 2018;Lerosey-Aubril and Pates, 2018;Pates et al., 2018;Guo et al., 2019;Wu et al., 2021a;Wu et al., 2021b;Wu et al., 2022 and references therein). Whole body specimens of radiodonts remain relatively rare but have been instrumental in describing previously unknown features of their flaps, setal blades and tail fan (Van Roy and Briggs, 2011;Van Roy et al., 2015;Zeng et al., 2022), and internal organs such as the nervous system (Cong et al., 2014;Moysiuk and Caron, 2022) and digestive tract (Daley and Edgecombe, 2014;Vannier et al., 2014). ...
... Debates about the cephalic carapaces in Radiodonta center around whether they are dorsal or ventral in position, which changes their interpretation and suggested homologies with plates seen in the heads of upper stem lineage and crown group euarthropods. For example, the rounded central cephalic structure in Anomalocaris canadensis ( Figure 1C) was interpreted as dorsal by Daley and Edgecombe (2014), and a carapace of similar size, shape and position observed in I. maotianshanensis ( Figure 1A) from the Chengjiang Biota (Chen et al., 1994;Wu et al., 2021a;Zeng et al., 2022) is also suggested to be dorsal. However, Budd (2021) suggested that these rounded central carapaces are actually ventral, and further suggested the presence of a ventral sclerite in Peytoia ( Figure 1D) (Whittington and Briggs, 1985;Collins, 1996), although confirmation awaits a complete redescription of this taxon. ...
... Taxa included: "Anomalocaris" briggsi ( Figure 5C) (Nedin, 1995), Houcaris saron ( Figure 5D) (Hou et al., 1995), Houcaris magnabasis ( Figure 5B) (Pates et al., 2021a), Tamisiocaris borealis ( Figure 5A) (Daley and Peel, 2010). The diagnosis of Hurdiidae established in was recently revised in Wu et al. (2021a). ...
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One of the most widespread and diverse animal groups of the Cambrian Explosion is a clade of stem lineage arthropods known as Radiodonta, which lived exclusively in the early Paleozoic. First reported in 1892 with Anomalocaris canadensis, radiodonts are now one of the best known early animal groups with excellent representation in the fossil record, and are ubiquitous components of Konservat-Lagerstätten from the Cambrian and the Early Ordovician. These large swimmers were characterised by a segmented body bearing laterally-oriented flaps, and a head with a distinct radial oral cone, a pair of large frontal appendages adapted for different feeding modes, compound eyes on stalks, and prominent head carapaces. Radiodonts inform on the paleoecology of early animal communities and the steps involved in euarthropod evolution. Four families within Radiodonta have been established. The raptorial predator families Anomalocarididae and Amplectobeluidae were dominant early in the evolutionary history of Radiodonta, but were later overtaken by the mega-diverse and widespread Hurdiidae, which has a more generalised sediment-sifting predatory mode. Suspension feeding, notably in the families Tamisiocarididae and Hurdiidae, also evolved at least twice in the history of the clade. The well-preserved anatomical features of the radiodont body and head have also provided insights into the evolution of characteristic features of Euarthropoda, such as the biramous limbs, compound eyes, and organisation of the head. With 37 species recovered from all major paleocontinents of the Cambrian and Early Ordovician, Radiodonta provides a unique opportunity for revealing evolutionary patterns during the Cambrian Explosion.
... Radiodont frontal appendages can be separated into two major regions for amplectobeluids, anomalocaridids and tamisiocaridids, namely, peduncle and distal articulated region. The term 'peduncle' [48] (also called a 'base' sensu [49]) is used to describe proximal podomeres of frontal appendages, which have more weakly defined articulations and bear no endite or reduced endite; the 'distal articulated region' (defined by Cong et al. [25]; equivalent to 'claw' sensu [49]) refers to the distal part of appendages, where endites project from the ventral side of podomeres and may bear sophisticated auxiliary spines. An angle on dorsal margin can normally be identified as the boundary between the peduncle and the distal articulated region. ...
... Radiodont frontal appendages can be separated into two major regions for amplectobeluids, anomalocaridids and tamisiocaridids, namely, peduncle and distal articulated region. The term 'peduncle' [48] (also called a 'base' sensu [49]) is used to describe proximal podomeres of frontal appendages, which have more weakly defined articulations and bear no endite or reduced endite; the 'distal articulated region' (defined by Cong et al. [25]; equivalent to 'claw' sensu [49]) refers to the distal part of appendages, where endites project from the ventral side of podomeres and may bear sophisticated auxiliary spines. An angle on dorsal margin can normally be identified as the boundary between the peduncle and the distal articulated region. ...
... According to the pattern of the paleogeographic distribution of amplectobeluids, this group occurred in South China and Laurentia from Cambrian Stage 3 to Drumian, restricted to the subtropical to tropical belt ( Figure 7). Thus, in contrast to hurdiids [79], amplectobeluids have the preference for warm water, as seen in anomalocaridids and tamisiocaridids [49,80], which may be controlled by changes in sea temperatures and climate zones. ...
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Radiodonta, an extinct stem-euarthropod group, has been considered as the largest predator of Cambrian marine ecosystems. As one of the radiodont-bearing Konservat-Lagerstätten, the Guanshan biota (South China, Cambrian Stage 4) has yielded a diverse assemblage of soft-bodied and biomineralized taxa that are exclusive to this exceptional deposit. "Anomalocaris" kunmingensis, the most abundant radiodont in the Guanshan biota, was originally assigned to Anomalocaris within the Anomalocarididae. Despite this taxon being formally assigned to the family Amplectobeluidae more recently, its generic assignment remains uncertain. Here, we present new materials of "Anomalocaris" kunmingensis from the Guanshan biota, and reveal that the frontal appendages possess two enlarged endites; all endites bear one posterior auxiliary spine and up to four anterior auxiliary spines; three robust dorsal spines and one terminal spine protrude from the distal part. These new observations, allied with anatomical features illustrated by previous studies, allow us to assign this taxon to a new genus, Guanshancaris gen. nov. Brachiopod shell bearing embayed injury and incomplete trilobites, associated with frontal appendages in our specimens, to some extent confirm Guanshancaris as a possible durophagous predator. The distribution of amplectobeluids demonstrates that this group is restricted to Cambrian Stage 3 to Drumian, and occurs across South China and Laurentia within the tropics/subtropics belt. Moreover, the amount and abundance of amplectobeluids evidently decreases after the Early-Middle Cambrian boundary, which indicates its possible preference for shallow water, referring to its paleoenvironmental distribution and may be influenced by geochemical, tectonic, and climatic variation.
... The legend of flower drum lanterns spread in the Huaihe River Basin, which in fact fully demonstrates the life and production of the people in this area. It is not difficult to see that the people in this region are simple, hardworking, kind, and optimistic, and their dance form, content, and activity time are reflected in the cultural form [16]. In terms of dance structure, flower drum lantern dance is mainly divided into "big flower field" and "small flower field" which are closely combined with farming life. ...
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Anhui flower drum lantern, as a folk dance in the Huaihe River Basin, exudes the local cultural atmosphere and expresses the cultural color of song and dance drama incisively and vividly. At the same time, it is a sacrificial activity with social belief. As a typical example of the development of folk activities in Anhui, it is an important intangible cultural heritage. With the accelerating construction of economic globalization and social innovation, the pursuit of “cultural confidence” has gradually become the belief of a country, a nation, and even everyone. More and more attention is being paid to the protection and dissemination of national intangible cultural heritage. The paper takes Anhui flower drum lamp as the research object, combined with the characteristics of the regional nature, performance form, content, and cultural connotation of Huagu Lantern, by reading the social activities of the people on both sides of the Huaihe River Basin and using literature data, field visits, interviews, logical analysis, and other research methods. The origin, living environment, development historical context, cultural value, existing confusion, and development countermeasures of Huaihe River are analyzed and discussed. This article helps to spread to the people the understanding of the evolution law of the traditional projects with the characteristics of generational attack. At the same time, it is also helpful to grasp the understanding of Hua Gu Deng and the social life, social beliefs, social relations, and other factors on both sides of the Huaihe River. This also make people further understand the social status and value function of the flower drum lantern along the Huai River and it is of great practical significance to the dissemination of the same type of intangible cultural heritage.
... The key step to carrying out such studies is to start with an accurate three-dimensional (3D) model for fossils. Arthropod fossils with soft tissue preservation from the Cambrian Chengjiang biota (Series 2, Stage 3), Yunnan, China offer a compelling source of materials (Stein and Selden, 2012;Hou et al., 2017;Chen et al., 2019), especially with the recent application of micro-computed tomography (micro-CT) and 3D model rendering techniques that allow the recovery of, e.g., detailed appendage morphology (e.g., Liu et al., 2015Liu et al., , 2016Liu et al., , 2020Zhai et al., 2019aZhai et al., , 2019bZhai et al., , 2019cWu et al., 2021;O'Flynn et al., 2022;Zhang et al., in press). ...
Dynamic mechanical analysis offers the opportunity to explore the motility and feeding strategies of extinct organisms, but the prerequisite is to have an accurate recovery engineering model. As shown with micro-computed tomography (CT) scanning, fossils of the bivalved arthropod Ercaicunia multinodosa from the Cambrian (Series 2, Stage 3) Chengjiang biota of China have well-preserved three-dimensional (3D) morphological details with a certain degree of compression. Here, we propose a palaeontological restoration method using computational fluid dynamics (CFD) to analyse multiple hypothetical models based on the fossil information to obtain a reasonable restoration model. Furthermore, we carry out hydrodynamic experiments to verify the palaeontological restoration results. Our simulation and experimental results suggest that a dorsally convex and ventrally straight body shape with the valves opening at an angle of approximately 120° works best for E. multinodosa to overcome resistance and in the meantime obtain most lift while sliding in the water column. The combination of three-dimensional reconstruction, CFD simulation, and hydrodynamic experiments provides a useful method for restoring the morphologies of extinct animals and exploring their palaeoecology.
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The stem-group euarthropod Anomalocaris canadensis is one of the largest Cambrian animals and is often considered the quintessential apex predator of its time. This radiodont is commonly interpreted as a demersal hunter, responsible for inflicting injuries seen in benthic trilobites. However, controversy surrounds the ability of A. canadensis to use its spinose frontal appendages to masticate or even manipulate biomineralized prey. Here, we apply a new integrative computational approach, combining three-dimensional digital modelling, kinematics, finite-element analysis (FEA) and computational fluid dynamics (CFD) to rigorously analyse an A. canadensis feeding appendage and test its morphofunctional limits. These models corroborate a raptorial function, but expose inconsistencies with a capacity for durophagy. In particular, FEA results show that certain parts of the appendage would have experienced high degrees of plastic deformation, especially at the endites, the points of impact with prey. The CFD results demonstrate that outstretched appendages produced low drag and hence represented the optimal orientation for speed, permitting acceleration bursts to capture prey. These data, when combined with evidence regarding the functional morphology of its oral cone, eyes, body flaps and tail fan, suggest that A. canadensis was an agile nektonic predator that fed on soft-bodied animals swimming in a well-lit water column above the benthos. The lifestyle of A. canadensis and that of other radiodonts, including plausible durophages, suggests that niche partitioning across this clade influenced the dynamics of Cambrian food webs, impacting on a diverse array of organisms at different sizes, tiers and trophic levels.
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The Cambrian (Miaolingian; Wuliuan) Spence Shale Lagerstätte of northern Utah and southern Idaho is one of the most diverse Burgess Shale-type deposits of Laurentia. It yields a diverse fauna consisting of abundant biomineralized and locally abundant soft-bodied fossils,along a range of environments from shallow water carbonates to deep shelf dark shales. Panarthropods are the dominant component throughout the deposit, both in time and space, but while the trilobites and agnostoids are abundant, most of the soft-bodied taxa are only known from very few specimens. Additionally, the knowledge of the soft-bodied panarthropods is currently largely limited to locations in the Wellsville Mountains of northeastern Utah. This contribution describes 21 new soft-bodied panarthropods from six locations, including the first occurrences of soft-bodied panarthropods in the High-Creek, Smithfield Creek, Spence Gulch, and Two-Mile Canyon localities. Additionally, we report the presence of bradoriids, Branchiocaris pretiosa, Perspicaris? dilatus, Naraoia? sp., Thelxiope cf. T. palaeothalassia, and Tuzoia guntheri for the first time from the Spence Shale Lagerstätte, the first occurrence reported outside of the Burgess Shale for Thelxiope cf. T. palaeothalassia and the first Wuliuan occurrence of Tuzoia guntheri. We also report on a new hurdiid carapace element and additional specimens of Buccaspinea cooperi?, Dioxycaris argenta, Hurdia sp., and Tuzoia retifera. This new material improves our understanding of the panarthropod fauna of the Spence Shale Lagerstätte and substantially increases our understanding of the distribution of the described taxa in time and space.
The Palaeozoic radiodonts are important for understanding the evolution and ecology of early euarthropods. However, complete radiodont fossils are very rare, despite their central roles in understanding radiodont palaeobiology. Here we describe Innovatiocaris maotianshanensis gen. et sp. nov. in detail based on an iconic complete radiodont specimen from the early Cambrian Chengjiang Lagerstätte of China. The head of I . maotianshanensis has a pair of stalked eyes, an ovate dorsal sclerite, a pair of frontal appendages composed of 11 distal articulated podomeres bearing spiky endites with only anterior auxiliary spines, and a putative triradial oral cone. The body possesses six anterior pairs of small differentiated neck flaps and ten posterior pairs of trunk flaps, with soft tissues including alimentary canal and musculature preserved. The tail includes a tail fan comprising three pairs of lateral blades and a pair of very long furcae. Another two new species, Innovatiocaris ? sp. and I .? multispiniformis sp. nov., are established based on the frontal appendages with different numbers of anterior auxiliary spines and are tentatively assigned to Innovatiocaris . Phylogenetic analysis retrieves Innovatiocaris as either a basal member of Hurdiidae or early-branching species of the non-hurdiid clade. Thus, Innovatiocaris provides new insights into the radiodont phylogeny and illuminates the early diversification of Radiodonta. Supplementary material: Supplementary figures, phylogenetic data matrix, and a character list for phylogenetic analysis are available at Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at:
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Originally considered as large, solely Cambrian apex predators, Radiodonta—a clade of stem-group euarthropods including Anomalocaris—now comprises a diverse group of predators, sediment sifters and filter feeders. These animals are only known from deposits preserving non-biomineralized material, with radiodonts often the first and/or only taxa known from such deposits. Despite the widespread and diverse nature of the group, only a handful of radiodonts are known from postCambrian deposits, and all originate from deposits or localities rich in other total-group euarthropods. In this contribution, we describe the first radiodont from the UK, an isolated hurdiid frontal appendage from the Tremadocian (Lower Ordovician) Dol-cyn-Afon Formation, Wales, UK. This finding is unusual in two major aspects: firstly, the appendage (1.8 mm in size) is less than half the size of the next smallest radiodont frontal appendage known, and probably belonged to an animal between 6 and 15 mm in length; secondly, it was discovered in the sponge-dominated Afon Gam Biota, one of only a handful of non-biomineralized total-group euarthropods known from this deposit. This Welsh hurdiid breaks new ground for Radiodonta in terms of both its small size and spongedominated habitat. This occurrence demonstrates the adaptability of the group in response to the partitioning of ecosystems and environments in the late Cambrian and Early Ordovician world.
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Trilobitomorphs are a species-rich Palaeozoic arthropod assemblage that unites trilobites with several other lineages that share similar appendage structure. Post-embryonic development of the exoskeleton is well documented for some trilobitomorphs, especially trilobites, but little is known of the ontogeny of their soft parts, limiting understanding of their autecology. Here, we document appendage structure of the Cambrian naraoiid trilobitomorph Naraoia spinosa by computed microtomography, resulting in three-dimensional reconstructions of appendages at both juvenile and adult stages. The adult has dense, strong spines on the protopods of post-antennal appendages, implying a predatory/scavenging behaviour. The absence of such gnathobasic structures, but instead tiny protopodal bristles and a number of endopodal setae, suggests a detritus-feeding strategy for the juvenile. Our data add strong morphological evidence for ecological niche shifting by Cambrian arthropods during their life cycles. A conserved number of appendages across the sampled developmental stages demonstrates that Naraoia ceased budding off new appendages by the mid-juvenile stage.
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Traditionally, the origin and evolution of modern arthropod body plans has been revealed through increasing levels of appendage specialisation exhibited by Cambrian euarthropods. Here we show significant variation in limb morphologies and patterns of limb-tagmosis among three early Cambrian arthropod species conventionally assigned to the Bradoriida. These arthropods are recovered as a monophyletic stem-euarthropod group (and sister taxon to crown-group euarthropods, i.e. Chelicerata, Mandibulata and their extinct relatives), thus implying a radiation of stem-euarthropods where trends towards increasing appendage specialisation were explored convergently with other euarthropod groups. The alternative solution, where bradoriids are polyphyletic, representing several independent origins of a small, bivalved body plan in lineages from diverse regions of the euarthropod and mandi-bulate stems, is only marginally less parsimonious. The new data reveal a previously unknown disparity of body plans in stem-euarthropods and both solutions support remarkable evolutionary convergence, either of fundamental body plans or appendage specialization patterns.
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Background: Artiopodan euarthropods represent common and abundant faunal components in sites with exceptional preservation during the Cambrian. The Chengjiang biota in South China contains numerous taxa that are exclusively known from this deposit, and thus offer a unique perspective on euarthropod diversity during the early Cambrian. One such endemic taxon is the non-trilobite artiopodan Sinoburius lunaris, which has been known for approximately three decades, but few details of its anatomy are well understood due to its rarity within the Chengjiang, as well as technical limitations for the study of these fossils. Furthermore, the available material does not provide clear information on the ventral organization of this animal, obscuring our understanding of phylogenetically significant details such as the appendages. Results: We employed X-ray computed tomography to study the non-biomineralized morphology of Sinoburius lunaris. Due to the replacement of the delicate anatomy with pyrite typical of Chengjiang fossils, computed tomography reveals substantial details of the ventral anatomy of Sinoburius lunaris, and allow us to observe in detail the three-dimensionally preserved appendicular organization of this taxon for the first time. The dorsal exoskeleton consists of a crescent-shaped head shield with well-developed genal spines, a thorax with seven freely articulating tergites, and a fused pygidium with lateral and median spines. The head bears a pair of ventral stalked eyes that are accommodated by dorsal exoskeletal bulges, and an oval elongate ventral hypostome. The appendicular organization of the head is unique among Artiopoda. The deutocerebral antennae are reduced, consisting of only five podomeres, and bear an antennal scale on the second podomere that most likely represents an exite rather than a true ramus. The head includes four post-antennal biramous limb pairs. The first two biramous appendages are differentiated from the rest. The first appendage pair consists of a greatly reduced endopod coupled with a greatly elongated exopod with a potentially sensorial function. The second appendage pair carries a more conventionally sized endopod, but also has an enlarged exopod. The remaining biramous appendages are homonomous in their construction, but decrease in size towards the posterior end of the body. They consist of a basipodite with ridge-like crescentic endites, an endopod with seven podomeres and a terminal claw, and a lamellae-bearing exopod with a slender shaft. Contrary to previous reports, we confirm the presence of segmental mismatch in Sinoburius lunaris, expressed as diplotergites in the thorax. Maximum parsimony and Bayesian phylogenetic analyses support the monophyly of Xandarellida within Artiopoda, and illuminate the internal relationships within this enigmatic clade. Our results allow us to propose a transformation series explaining the origin of archetypical xandarellid characters, such as the evolution of eye slits in Xandarella spectaculum and Phytophilaspis pergamena as derivates from the anterolateral notches in the head shield observed in Cindarella eucalla and Luohuilinella species. In this context, Sinoburius lunaris is found to feature several derived characters within the group, such as the secondary loss of eye slits and a high degree of appendicular tagmosis. Contrary to previous findings, our analyses strongly support close affinities between Sinoburius lunaris, Xandarella spectaculum and Phytophilaspis pergamena, although the precise relationships between these taxa are sensitive to different methodologies. Conclusions: The revised morphology of Sinoburius lunaris, made possible through the use of computed tomography to resolve details of its three-dimensionally preserved appendicular anatomy, contributes towards an improved understanding of the morphology of this taxon and the evolution of Xandarellida more broadly. Our results indicate that Sinoburius lunaris possesses an unprecedented degree of appendicular tagmosis otherwise unknown within Artiopoda, with the implication that this iconic group of Palaeozoic euarthropods likely had a more complex ecology and functional morphology than previously considered. The application of computer tomographic techniques to the study of Chengjiang euarthropods holds exceptional promise for understanding the morphological diversity of these organisms, and also better reconstructing their phylogenetic relationships and evolutionary history.
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Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov. is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.
The euarthropod head is a highly versatile and functionally specialized body region composed of multiple appendage-bearing segments and whose complex evolution has been scrutinized through anatomical, developmental, and paleontological approaches [1 , 2 , 3 , 4 ]. Exceptionally preserved Cambrian fossils have allowed for the reconstruction of critical stages of the evolutionary history of the head, such as the origin of the labrum—an anteromedian flap-like structure that overlies the mouth opening in almost all extant representatives—from an ancestral pair of pre-ocular (protocerebral) appendages [3 , 4 , 5 ]. The highly conserved position of the labrum makes it a valuable anatomical landmark for understanding the anterior segmental organization among extant and extinct euarthropods [2 ]. However, the labrum is seemingly absent in the megacheirans, a major extinct group characterized by enlarged raptorial “great appendages” with a central role in competing hypotheses on the early evolution of the head [1 , 2 , 3 , 6 , 7 , 8 ]. Here, we used micro-computed tomography to demonstrate the presence of a three-dimensionally preserved labrum associated with the mouth opening in juvenile specimens of the megacheiran Leanchoilia illecebrosa from the early Cambrian Chengjiang biota, Southwest China. The position of the labrum relative to the pre-oral great appendages of L. illecebrosa indicates that these limbs correspond to the deutocerebral segment and are therefore serially homologous with the first appendage pair of extant euarthropods [1 , 2 , 4 , 6 , 8 ]. The reduced labrum and deutocerebral great appendages of L. illecebrosa also strengthen the affinities of megacheirans as stem-group chelicerates, in line with recent paleoneurological fossil data from the early to mid-Cambrian of China and North America [6 , 9 ].
The Drumian Wheeler Konservat-Lagerstätte of the House Range of Utah (Wheeler-HR) has yielded one of the most diverse exceptionally-preserved Cambrian biotas of North America. The discovery of soft-bodied fossils invariably provides precious insights on this biota, for most of its non-biomineralizing components are known from very few specimens. This contribution describes some 30 new exceptionally-preserved fossils of Wheeler panarthropods. Two new species are recognized, the radiodont Hurdia sp. nov. A and the megacheiran Kanoshoia rectifrons gen. et sp. nov. Along with a species of Leanchoilia, K. rectifrons represent the first confident megacheiran record in these strata. The presence of the radiodont genus Amplectobelua and the isoxyid species Isoxys longissimus are reported outside of the Burgess Shale in Laurentia. New specimens of Caryosyntrips serratus, Naraoia compacta, Messorocaris magna, and Mollisonia symmetrica provide insights on the phylogenetic affinities, local spatial distribution, and morphological variation of these species hitherto known by single specimens in the Wheeler-HR. The same is true of new materials of the more common Pahvantia hastata and Perspicaris? dilatus. Formal descriptions of the order Mollisoniida ord. nov. and family Mollisoniidae fam. nov. are also provided. Lastly, the preservation of body structures other than the dorsal exoskeletons is illustrated for the first time in two common components of the fauna: the agnostid Itagnostus interstrictus and the bivalved euarthropod Pseudoarctolepis sharpi. The new material substantially improves our understanding of the diversity of the Wheeler-HR biota, and provides new evidence of its distinctiveness relative to the Wheeler biota of the Drum Mountains.
Anomalocaris, the most well‐known genus of the diverse stem euarthropod group Radiodonta, was first reported over 100 years ago from the Burgess Shale (Canada). This large Cambrian apex predator was later treated as occurring in the southern Great Basin (California and Nevada, USA). We re‐evaluate the systematic affinities of previously described material from the Pioche Formation, Nevada, and the Latham Shale, California, and describe the first radiodonts from the Pyramid Shale Member, Carrara Formation, California. Latham Shale (Cambrian Series 2, Stage 4, upper Dyeran) specimens previously assigned to Anomalocaris are reinterpreted as Ramskoeldia consimilis?, an amplectobeluid previously known only from the Chengjiang biota (Cambrian Series 2, Stage 3). Younger material from the Pioche and Carrara Formations (Series 2, Stage 4) is described as a new Anomalocaris species, A. magnabasis. This new species sheds light on the two‐part structure of Anomalocaris ventral endites, a potentially important character for distinguishing species, and reveals a sequence of five disarticulation stages for frontal appendages. The oldest Hurdia from Laurentia is also reported from the Pioche Formation (Cambrian Series 2, Stage 4). A changeover in taxonomic composition of the Radiodonta in the southern Great Basin is recognized: Anomalocaris replaces Ramskoeldia in the upper Dyeran, but it is not associated with a replacement of local olenelloid trilobites or seen in radiodonts elsewhere in Laurentia. These new data, combined with a summary of known radiodont occurrences, suggest that Anomalocaris species did not have large geographical distributions, when compared with other radiodonts such as Hurdia and Caryosyntrips.