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ANCIENT ANIMAL MIGRATION: A CASE STUDY OF
EYELESS, DIMORPHIC DEVONIAN TRILOBITES
FROM POLAND
by BŁA _ZEJ BŁA _ZEJOWSKI1, CARLTON E. BRETT2, ADRIAN KIN3,† ,
ANDRZEJ RADWA �NSKI4,† and MICHAŁ GRUSZCZY �NSKI3,†1Institute of Palaeobiology, Polish Academy of Sciences, Twarda 51/55, 00-818, Warszawa, Poland; [email protected] of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA; [email protected] ‘Phacops’ – Association of Friends of Geosciences, Grajewska 13/40, Warszawa, 02-766, Poland4Institute of Geology, University of Warsaw, _Zwirki i Wigury 93, 02-089, Warszawa, Poland
Typescript received 15 February 2016; accepted in revised form 8 July 2016
Abstract: We report evidence of one of the oldest known
animal migratory episodes in the form of queues of the eye-
less trilobite Trimerocephalus chopini Kin & Bła_zejowski,
from the Late Devonian (Famennian) of central Poland. In
addition, there is evidence for two morphs in this popula-
tion, one with nine segments and the other with ten. We
infer that these queues represent mass migratory chains
coordinated by chemotaxis, comparable to those observed in
modern crustaceans such as spiny lobsters, and further sug-
gest that the two forms, which occur in an approximately
1:1 ratio, may be dimorphs. These ancient arthropods may
have migrated periodically to shallow marine areas for mass
mating and spawning. The sudden death of the trilobites in
the queues may have been caused by excess carbon dioxide
and hydrogen sulphide introduced into the bottom water by
distal storm disturbance of anoxic sediments. This study
demonstrates the potential for further research on the evolu-
tion and ecology of aggregative behaviour in marine arthro-
pods.
Key words: animal migration, eyeless trilobite, Phacopinae,
Devonian, Holy Cross Mountains, Poland.
PER IODIC mass migrations have been observed in many
modern groups of vertebrate and invertebrate animals
(Hoare 2009a, b). There are several possible functions of
such periodic migratory behaviour including reproductive
and trophic aggregations (Thollot et al. 1999; Crossin
et al. 2009). Recent studies on the processes controlling
mass migrations (Wilcove 2008) form an important
aspect of behavioural science, particularly migrations
related to human activity and rapid variations of climates,
but very little is yet known about the evolutionary origin
and ecological significance of mass migrations, which
have rarely been recognized in the fossil record. Chain-
like clusters of the enigmatic early Cambrian arthropod
(crustacean?) Synophalos xynos have been described before
(Hou et al. 2008, 2009); in this example the organisms
were seemingly linked in that the caudal region of each
individual inserted into the anterior carapace of the one
behind. The authors interpreted these chains as probable
migratory aggregates. However, the forms and structures
described are distinct from positions or behaviour known
in trilobites, as briefly noted earlier (Radwa�nski et al.
2009, p. 467). Linear clusters of trilobites are also known
from the Ordovician of Morocco (Chatterton & Fortey
2008) and that of Portugal (Guti�errez-Marco et al. 2009),
but their relationship to migration or mating aggregation
has not been pursued in detail. These instances in dis-
tantly related clades, however, may point to a more com-
mon phenomenon among arthropods than previously
recognized.
New material from the Kowala Quarry (Holy Cross
Mountains, Central Poland) described herein has great
potential for the study of the nature of such migrations
based on queues of the blind phacopide trilobite Trimero-
cephalus. A previous study of these queues (Radwa�nski
et al. 2009) concerned the structure (organization) of
queues in relation to the interpreted ambient environ-
ment. Size frequency aspects and dimorphism, were not
discussed in the former study. Thus, the present paper
aims to provide substantial further details and discussion†Deceased
© The Palaeontological Association doi: 10.1111/pala.12252 743
[Palaeontology, Vol. 59, Part 5, 2016, pp. 743–751]
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of the significance of these findings and a reinterpretation
of queues as evidence for migratory behaviour, probably
in association with reproduction in these blind trilobites.
MATERIAL AND METHOD
All trilobites discussed herein occur in an approximately
25 m thick succession of marly shales in the early Famen-
nian (approximately 365 Ma), at the Kowala Quarry near
Kielce, Holy Cross Mountains, central Poland (Fig. 1)
(Radwa�nski et al. 2009). A total of 78 examples of rows or
queues of the blind trilobite Trimerocephalus chopini Kin &
Bła_zejowski, 2013, have been obtained, each with up to 19
aligned, articulated individuals. These trilobite queues are
preserved within three horizons of marly shales with occa-
sional small, calcareous concretions. Trilobites in the
queues are arranged in the same direction, one after the
other, in cephalon to pygidium (head to tail) manner, and
frequently contact or overlap each other (Figs 2A, C; 3).
All specimens are preserved in apparent life-positions and
those in queues fall into a relatively narrow size range rela-
tive to those seen in other phacopine trilobites (7–19 mm
in length). Nearly all specimens are fully articulated and a
few individuals preserve elements of locomotory appen-
dages (i.e. endo- and exopodites), indicating rapid, in situ
burial. They are directly associated with numerous small
enrolled specimens of T. chopini. One exceptionally
preserved specimen, examined in detail using x-ray tomo-
graphy, revealed the oldest fully preserved moulting
episode (exuvium plus soft-shelled trilobite) known from
the fossil record (Bła_zejowski et al. 2015).
All trilobite specimens have been prepared manually.
The collected material is housed at the Institute of
Palaeobiology, Polish Academy of Sciences in Warsaw
(ZPAL Tr.8).
Carbon dioxide for isotopic analysis of matrix carbon-
ate was extracted either manually using traditional vac-
uum extraction lines or using an automated online
Isocarb reaction system. Carbon and oxygen stable iso-
tope data were obtained using a Finnigan MAT 251 mass
spectrometer at the University of Liverpool. All isotopic
data are reported with reference to the VPDB interna-
tional standard; typical precisions of 0.1 & are reported
by this laboratory. Statistical calculations were performed
with PAST v. 3.01 (Hammer et al. 2001).
RESULTS
The size-range of articulated trilobite exoskeletons within
the queues varies somewhat. Surprisingly, however, the
studied specimens in ten sample queues have an inconsis-
tent number of thoracic segments, with nearly equal
numbers of two morphs (Kin & Bła_zejowski 2013): 51%
of individuals have nine segments, while 49% have ten
A C
B
F IG . 1 . A, map of Poland indicat-
ing the location of the Holy Cross
Mountains area (HCM; rectangle).
B, generalized geological map of the
Holy Cross Mountains and the loca-
tion of Kowala Quarry (arrowed).
C, map of Kowala Quarry with the
location of the studied section
exposed in the western part of the
northern quarry wall (arrowed).
Scale bars represent 100 km (A);
10 km (B); and 0.5 km (C).
744 PALAEONTOLOGY , VOLUME 59
Page 3
(Table 1). In general, the 9-segmented morphs are smaller
(N = 34; mean = 8.8 mm; range: 5–12 mm) than 10-seg-
mented forms (N = 36; mean = 14.5 mm; range: 7–19 mm); the medians are significantly different (Mann-
Whitney U-test: U = 90; p = 6.669).
In addition, at least 119 enrolled specimens were found
in association with the queues at each of the three levels,
though typically a few millimetres above the bedding
planes containing the queues. These specimens usually
range in cephalic size from 2 to 4 mm.
Geochemical and mineralogical investigations revealed
very fine-grained calcareous silt with abundant limonitic
pseudomorphs after original pyrite, directly underneath
individual T. chopini skeletons from the trilobite queues.
Carbonate sediment underneath the individual T. chopini
exuviae, yielded d13C values that oscillated around
�1.5&, whereas values for the sediment underneath the
trilobite skeletons in the queues are somewhat higher,
being around �0.3& PDB (Fig. 4G–H).
DISCUSSION
Seasonal migrations of modern marine arthropods: a
modern analogue
Among modern marine arthropods, the phenomenon of
mass seasonal migration has been observed, for example,
among spiny lobsters (Decapoda, Palinuridae) in pre-
adult, moulting and reproductive phases of their life cycle
(Herrnkind 1980) (Fig. 2B). Reproductive cycles are the
major causes of periodic mass migration in the spiny lob-
ster Jasus edwardsi Hutton, from New Zealand; this spe-
cies may migrate considerable distances, from offshore to
inshore sites (Linnane et al. 2005). Another lobster spe-
cies, Panulirus ornatus Fabricius migrates more than
500 km to shallow water sites for mass breeding (Moore
& McFarlane 1982). The lobster breeding sites vary, but
are generally in shallow depths of a few metres and fre-
quently occur close to coral reef buildups (Kanciruk &
Herrnkind 1978). There are many other examples of mass
migration among Palinuridae including Panulirus argus
Latreille, Panulirus cygnus George, and Jasus verreauxi
Milne-Edwards (Herrnkind 1980; Phillips 1983; Booth
1997).
Modern aquatic arthropods, such as crayfish and lob-
sters, are highly sensitive to specific chemical compounds
present in minute amounts within the ambient water
(Attema 1995), due to specialized chemoreceptor cells.
Urine-borne compounds are among the most common
chemical signals, which stimulate both group behaviour
(e.g. scent paths) and individual interactions (e.g. court-
ship, dominance). For example, spiny lobsters of the spe-
cies P. argus disseminate urine from special glands over
distances of 1–2 m, which allows other individuals to
sense the surrounding environment, especially under
A
C
B
F IG . 2 . Examples of periodic migratory queues occurring among the ancient and modern arthropods: trilobites and spiny lobsters.
A, idealized reconstruction of Trimerocephalus chopini Kin & Bła_zejowski, 2013 queue showing trilobites about 365 million years ago,
Kowala (Holy Cross Mountains, Poland). B, example of a relatively short migratory queue formed by six specimens of the spiny lobster
Panulirus argus (Linnaeus), similar to that photographed by Herrnkind (1975, p. 828), Bimini (Bahamas). C, typical example of T. chopini
queue (formed by over ten well-aligned specimens; Kow/Ta 60) from the third horizon. Scale bar in C represents 10 mm. Colour online.
BŁA _ZE JOWSKI ET AL . : ANC IENT ANIMAL MIGRAT ION 745
Page 4
conditions of significantly reduced visibility caused by
bottom water turbidity. The number of lobsters moving
in single queues along the scent path (= urinal trail) is
variable, reaching a few to several dozen individuals
usually during day to day movements, and hundreds or
even thousands of individuals in seasonal migrations
(Booth 1997).
Trilobite migratory queues controlled by chemotaxis
In the case of Trimerocephalus chopini queues, it is proba-
ble that trilobites moved one after another following
chemosensory cues because T. chopini was eyeless and is
regarded as having had no alternate photoreceptors.
Therefore, T. chopini queues are recognized as the first
fossil record of possible chemotaxis, and these lines are
interpreted as the oldest known migratory queues. We
suggest that the trilobites were undergoing mass migra-
tions to spawning-grounds during reproductive periods.
This hypothesis is supported by the relatively small but
variably sized specimens forming queues, demonstrating
putative dimorphism with approximately equal numbers
of the two dimorphs, and by comparison with modern
analogues. There is abundant evidence for possible
aggregative moulting and mating behaviour in phacopid
trilobites (Speyer & Brett 1985; Brett et al. 2011; Brett et al.
2012). Mass occurrences of Ordovician trilobites have also
been explained as a result of mating behaviour (Karim &
Westrop, 2002; Guti�errez-Marco et al. 2009). The repeated
occurrences of species-segregated clusters of carcasses and
moult ensembles, of similarly sized individuals in particu-
lar facies in the Middle Devonian Hamilton Group sug-
gests that the trilobites migrated to particular breeding
grounds prior to mass moulting and spawning as in certain
extant peracarid crustaceans (Speyer & Brett 1985).
Such mating grounds might also become trilobite
‘nurseries’ (Paterson et al. 2007). Modern analogues of
this phenomena are represented by ‘nursery grounds’ of
the horseshoe crabs (e.g. Tachypleus tridentatus Leach and
Limulus polyphemus Linnaeus (Carmichael et al. 2003)).
‘Limulid nurseries’ are also described from the Upper
Jurassic of Poland (Kin & Bła_zejowski 2014; Bła_zejowski
2015), and similar ‘nurseries’ observed in some echino-
derms are widely discussed by Radwa�nski et al. (2012,
2014).
The latter suggestion appears to be supported in the
case of the Kowala trilobites by the occurrence of a num-
ber of small, sphaeroidally or discoidally enrolled
T. chopini specimens (Fig. 4A–F) in situ within each of
the three horizons with the queues. All of these enrolled
individuals represent meraspid stages with 3–7 thoracic
segments, i.e. juvenile forms of T. chopini. Thus, the juve-
niles may represent remains of a ‘trilobite nursery’ and
the T. chopini queues formed by sexually mature individ-
uals (i.e. holaspids in strict morphological terms) may
represent migration to the spawning area during repro-
duction cycles. It should be emphasized that the largest
F IG . 3 . Migratory queue of Trimerocephalus chopini Kin &
Bła_zejowski, 2013 from Kowala Quarry (Holy Cross Mountains).
Schematic drawing of three marly shale surfaces exposing the
longest T. chopini queue (formed by 19 specimens; Kow/Ta 3)
as extracted from the first of studied horizon (left) and close-
ups of the best preserved fragments (right). Scale bar represents
50 mm. Colour online.
746 PALAEONTOLOGY , VOLUME 59
Page 5
TABLE
1.Biometricmeasurements
ofTrimerocephaluschopiniKin
&Bła_ zejowski,2013
form
ing10
sample
trilobitequeues,that
occurin
asuccessionofmarly
shales
ofearlyFam
e-
nnianage,exposedin
theKowalaQuarry
(Holy
Cross
Mountains,central
Poland).
Queue
characteristics
Kow/Ta3
(Fig.3)
Kow/
Ta19
Kow/
Ta22
Kow/
Ta23
Kow/
Ta45
Kow/
Ta47
Kow/
Ta59
Kow/Ta60
(Fig.2C
)
Kow/Ta63
Kow/Ta77
Totalnumber
of
individuals
195
55
56
710
1013
Individualswith9
thoracicsegm
ents
82
34
11
22
56
Lengthof
individualswith9
thoracicsegm
ents
(mm)
5/11/12/9/10/
~10/9/11
9/11
10/7/11
10/8/~11/10
11~5
9/~1
011/12
10/10/~1
2/9/10
9/10/8/~10/11/10
Individualswith10
thoracicsegm
ents
43
21
35
36
45
Lengthof
individualswith10
thoracicsegm
ents
(mm)
15/17/14/~19
17/17/18
15/17
137/13/17
11/11/9/
10/~16
15/18/15
14/14/15/
~14/12/17
14/14/~1
5/17
13/14/17/14/~1
4
Additional
datafor
incomplete
individuals(w
idth:
lengthofcephalon;
mm)
5:3/~7
:5/6:4/~5:3&
threesm
allto
semi-largepartially
preserved
thoraces
––
–5:3
–8:6&
7:5
~7:5
&single
partofthorax
–5:3&
~5:3
B ŁA _ZE JOWSKI ET AL . : ANC IENT ANIMAL MIGRAT ION 747
Page 6
number of segments observed in the thorax of T. chopini
was 11 (Kin & Bła_zejowski 2013). Variable numbers of
segments in holaspid trilobites is very rare, but have been
demonstrated in the unusual form Aulacopleura konincki
(Hughes & Chapman 1995). In the latter, dimorphism is
ruled out as the segment numbers vary from 18 to 22.
If the unique queues formed by T. chopini discussed
herein were strictly connected to periodic migrations for
breeding, it could be assumed that T. chopini reached
maturity during the 9- or 10-segmented stage. It also
means that the sexual maturity of T. chopini was not nec-
essarily combined with morphological stabilization of their
exoskeletons, as revealed essentially by the occurrence of a
stable number of trunk segments. It is associated with the
transition between two main ontogenetic phases: from
the morphologically variable larval (meraspid) period to
the morphologically stable post-larval (holaspid) period,
i.e. from anamorphic to epimorphic phases (Hughes et al.
2006; Cronier 2011). Thus, the results of this study pro-
vide a possible example of sexually mature trilobites,
forming unique migratory queues and represented by
non-holaspid individuals (i.e. non ‘adult-type’ forms, in
terms of widely accepted morphological classification).
The variation in thoracic segment number could simply
represent an unusual case of meristic variation of segment
number within a species, or different moult stages. Alter-
natively, and more probably, the 9- or 10-segmented
individuals both represent holaspids, but male and female
dimorphs respectively. The fact that both 9- and 10-seg-
mented forms show a substantial and similar range of
variation (5 mm for 9-segmented forms and 7 mm in
10-segmented forms) suggests that each morph is not sim-
ply a different growth stage. Rather, each form occurs as
both smaller and larger sized individuals, a range much
larger than that found in a single meraspid instar of any
known trilobite. Furthermore, the earlier meraspid forms,
up to stage 8, are represented by the minute enrolled spec-
imens, so there was a very large size difference between
meraspid stage 8 and stage 9 or 10, suggesting that once
one or the other of these segment numbers was achieved
it remained stable through a substantial size range, most
likely representing several moult episodes.
Other forms of probable sexual dimorphism in trilo-
bites have been documented, including the presence of
preglabellar bulbs, being possible brood pouches (Fortey
& Hughes 1998), and median cephalic bulbs and spines
in raphiophorids (Knell & Fortey 2005). These morpho-
logical features can be logically related to functional dif-
ferences between sexes (e.g. brood pouches in females) or
sexual selection. Conversely, it is difficult to conceive of
A
D
G H
E F
B C
F IG . 4 . Two examples of juvenile
enrolled trilobites representing a
meraspid stage, occurring in the
upper parts of two horizons with
Trimerocephalus chopini queues. A–C, example of a small, enrolled speci-
men found in horizon 1. D–F,slightly larger enrolled specimen
from horizon 2; note the white arrow
marking siderite filling the enrolled
specimen. G, backscattered electron
image of the sediment just beneath
the skeleton of one of the trilobites
in the T. chopini queue with a place
of composition analysis marked with
arrow; note the amount of iron oxide
(white) crystals pseudomorphs after
pyrite and the stable carbon and oxy-
gen isotope compositions for the
sediment matrix. H, T. chopini exu-
vium; note that the d13C values and
d18O isotope values for the sediment
from underneath the exuviae are
identical to those for the sediment
adjacent to the trilobite queue. Scale
bars represent 1 mm (A–C, G);2 mm (D–F); 4 mm (H). Colour
online.
748 PALAEONTOLOGY , VOLUME 59
Page 7
functional distinctions in forms with one more or less
segment. Possibly, this was simply related to size differ-
ences between sexes, but, as yet, we have no more plausi-
ble explanation. For this reason, we must be slightly
tentative in ascribing this dimorphism to sexual differ-
ences. Nonetheless, considering the cohort of trilobites
occurring in queues as a whole, the ratio of 9- to 10-seg-
mented individuals is very nearly 1:1. While sex ratios in
some organism populations are significantly different
from unity, the preservation of 1:1 ratios of morphotypes
is strongly suggestive of sexual dimorphism. Interestingly,
the vast majority of contemporary arthropods become
sexually mature exactly after entering into the epimorphic
phase (Minelli 1992, 2003; Minelli et al. 2006). This
occurrence of dimorphism in segment number is, to our
knowledge, unique among trilobites and its functional
significance, if any, is not known, although differences in
mean size between sexes are common.
Sedimentary characteristics of the bottom sediment for
the migratory queues of T. chopini indicate (see Rad-
wa�nski et al. 2009) a low energy hydrodynamic regime.
Typical parallel to low-angle cross lamination and occa-
sional hummocky cross stratification of the carbonate silt
indicate a low energy setting affected by occasional
storms. An abundance of remains of primitive plants (i.e.
psilophytes) provides evidence for close proximity to
land; however, these remains may have been transported
offshore to settle out in relatively deep water, where dys-
oxic conditions favoured their preservation.
Mass mortality of Trimerocephalus chopini
The most striking feature of the examined trilobite queues
is the preservation of the members of the queue in their
life positions suggesting instantaneous mortality. A few
trilobite individuals in the queues exhibit slightly flexed
postures, suggesting incipient but incomplete enrollment,
a plausible defensive behaviour for trilobites. The occur-
rence of fine-grained pyrite and slightly negative d13C val-
ues for the sediment adjacent to trilobite queues, as well
as that directly beneath the carcasses, strongly suggests
bacterial decay of rapidly buried trilobite soft parts in the
sulphate reduction zone. Anaerobic degradation of
organic matter underneath the trilobite skeletons may
have increased alkalinity sufficiently that pore fluids
became supersaturated with respect to calcium carbonate
causing precipitation of cements.
Small, enrolled T. chopini exoskeletons are filled either
by siderite (d13C = �1& and d18O = �2.5&), or sedi-
ment of almost identical appearance to the sediment
beneath the skeletons of queuing trilobites, forming con-
cretionary infillings within the enrolled skeletons. Both
the sediment inside the enrolled trilobites and that
forming concretions contain abundant iron oxide pseudo-
morphs after pyrite crystals; both also display d13C values
of ~�0.5&. The enrolled specimens of T. chopini suggest
that they had time to take defensive action, i.e. enrolling
the body to protect sensitive ventral respiratory surfaces,
so their death was not as sudden as that of trilobites in
the queues.
Any hypothesis for the preservation of these queues
must explain the nearly synchronous mortality of many
individuals slightly prior to abrupt burial. We suggest
that the initial affect of storms may have been to stir up
anoxic, sulphide-rich sediment slightly upramp from the
site of mortality, producing thin suspensions of toxic,
turbid water. The most likely scenario for sudden death of
both the adult and juvenile T. chopini involves suffocation,
hypercapnia (excess CO2) and/or toxicity of sulphidic
waters. Seemingly, these trilobites died literally in their
tracks but the carcasses were then subject to minor, incipi-
ent post-mortem decay, without transport, prior to rapid
burial. We suggest that clouds of suspended sediments
subsequently blanketed the seafloor, perhaps as a result of
fallout of flocculated muds in the aftermath of the same
storm that had killed the animals.
Juvenile forms of T. chopini could attain fully enrolled
postures, perhaps because small forms were more tolerant
of anoxic/sulphidic conditions compared to adult individ-
uals, as has been demonstrated in experiments (see Hol-
man & Hand 2009) carried out on ghost shrimp of the
species Lepidophthalmus louisianensis Schmidt. Thus, these
juveniles survived long enough to respond to the toxic
stimulus by enrollment.
CONCLUSIONS
Results of our research demonstrate that repetitive migra-
tory behaviour had already evolved among marine animals
by at least the mid-Palaeozoic Era. We infer that the breed-
ing strategy for the blind trilobite Trimerocephalus chopini
Kin & Bła_zejowski 2013 included mass migration to
spawning-grounds; the mass migrations in queues were
likely coordinated by primary chemosensory phenomenon,
as in some modern crustaceans. An important argument
related to periodic migration of T. chopini to the breeding
areas is the co-occurrence of numerous enrolled juveniles,
which occur in each queue horizon; these abundant juve-
niles could record ‘trilobite nurseries’. Moreover, individu-
als of T. chopini forming migratory queues do not show a
fixed number of thoracic segments. A plausible explanation
for the 9- and 10-segmented variants, considering their
nearly 1:1 ratio, is that they represent sexual dimorphs in a
single species; these two morphotypes each show consider-
able and overlapping size ranges, although the 10-segmen-
ted morph is generally larger.
BŁA _ZE JOWSKI ET AL . : ANC IENT ANIMAL MIGRAT ION 749
Page 8
As to causes of sudden death of the described blind
trilobites, we suggest poisoning by hydrogen sulphide,
which is very diffusive and highly toxic, and/or hypercap-
nia, owing to carbon dioxide released from sediment,
replacing oxygen in the bottom waters. Regardless, the
similar state of in situ preservation of these blind trilobites
suggests almost simultaneous death of all of the individu-
als (both enrolled juveniles and sexually mature adults
arranged in the queues). Abrupt burial of T. chopini popu-
lations followed very shortly after the mass mortalities,
probably from fallout of flocculated muds stirred up by
storms (Type 1 assemblages of Brett et al. 2012). This
must have been a recurrent phenomenon in this area
during the Late Devonian because at least three occasions
of storm burial overlapped with reproductive periods
of T. chopini to produce similar queues at three distinct
horizons.
Finally, we conclude that chemotaxis may have func-
tioned as a long-term macroevolutionary process control-
ling reproductive behaviour of arthropods, the largest
known phylum of animals on Earth.
Acknowledgements. Most of the work presented in this paper,
including field and laboratory studies and the idea and overall
design of research, were initiated by Adrian Kin who passed away
before the completion of the final draft of this paper. Bła_zej
Bła_zejowski, Carlton E. Brett and Andrzej Radwa�nski accepted
responsibility for the validity of data and conclusions presented
herein. Warmest thanks are expressed to Urszula Radwa�nska
(University of Warsaw) for many helpful suggestions during the
early phase of this investigation. Comments and criticism sup-
plied by Tammie Gerke greatly improved the quality and content
of this manuscript. We would like to thank Adam T. Halamski
(Institute of Palaeobiology, PAS) for assistance with statistical
analysis. And last but not least, we wish to acknowledge Lisa
Amati (NY State Museum, Albany), Sally Thomas (The Palaeon-
tological Association) and one anonymous reviewer for his critical
review and very helpful comments that improved the manuscript.
Editor. George Sevastopulo
REFERENCES
ATTEMA, J. 1995. Chemical signals in the marine environ-
ment: dispersal, detection, and temporal signal analysis.
Proceedings of the National Academy of Sciences, 92, 62–66.BŁ A _ZEJOWSKI , B. 2015. The oldest species of the genus
Limulus from the Late Jurassic of Poland. 3–14. In CARMI-
CHAEL, R. H., BOTTON, M. L., SHIN, P. K. S. and
CHEUNG, S. G. (eds). Changing global perspectives on biol-
ogy, conservation, and management of horseshoe crabs. Springer.
-GIESZCZ, P., BRETT, C. E. and BINKOWSKI , M.
2015. A moment from before 365 Ma frozen in time and
space. Scientific Reports, Nature Publications, 5, 14191. doi:
10.1038/srep14191
BOOTH, J. D. 1997. Long-distance movements in Jasus ssp.
and their role in larval recruitment. Bulletin of Marine
Sciences, 61, 111–128.BRETT, C. E., ALLISON, P. A. and HENDY, A. J. W.
2011. Comparative taphonomy and sedimentology of
small-scale mixed carbonate/siliciclastic cycles: synopsis of
Phanerozoic examples. 107–199. In ALLISON, P. A. and
BOTTJER, D. J. (eds). Taphonomy: process and bias through
time. 2nd edn. Springer Science.
-ZAMBITO, J. J., HUNDA, B. R. and SCHINDLER, E.
2012. Mid Paleozoic trilobite Lagerst€atten: models of
diagenetically enhanced obrution deposits. Palaios, 27, 326–345.CARMICHAEL, R. H., RUTECKI , D. and VALIELA, I.
2003. Abundance and population structure of the Atlantic
horseshoe crab Limulus polyphemus in Pleasant Bay, Cape
Cod. Marine Ecology Progress Series, 246, 225–239.CHATTERTON, B. D. E. and FORTEY, R. 2008. Linear
clusters of articulated trilobites from the Lower Ordovician
(Arenig) strata at Bini Tinzoulin, north of Zagora, southern
Morocco. 73–78. In R �ABANO, I. GOZALO,R. and
GARC�IA-BELLIDO,D. (eds). Advances in trilobite research.
Instituto Geol�ogico y Minero de Espa~na, Madrid.
CRONIER, C. 2011. Varied development of trunk segmenta-
tion in three related Upper Devonian phacopine trilobites.
Historical Biology, 22 (4), 341–347.CROSSIN, G. T., HINCH, S. G., COOKE, S. J., COOP-
ERMAN, M. S., PATTERSON, D. A., WELCH, D. W.,
HANSON, K. C., OLSSON, I., ENGLISH, K. K. and
FARRELL , A. P. 2009. Mechanisms influencing the timing
and success of reproductive migration in a capital breeding
semelparous fish species, the sockeye salmon. Physiological &
Biochemical Zoology, 82, 635–652.FORTEY, R. A. and HUGHES, N. 1998. Brood pouches in
trilobites. Journal of Paleontology, 72 (4), 638–649.GUTI�ERREZ-MARCO, J. C., S �A, A. A., GARC�IA-
BELLIDO, D. C., R �ABANO, I. and VAL�ERIO, M. 2009.
Giant trilobites and trilobite clusters from the Ordovician of
Portugal. Geology, 37, 443–446.HAMMER, Ø., HARPER, D. A. T. and RYAN, P. D. 2001.
PAST: paleontological statistics package for education and
data analysis. Palaeontologia Electronica, 4 (1), 1–9.HERRNKIND, W. F. 1975. Strange march of the spiny lob-
ster. National Geographic, 147 (6), 818–831.-1980. Spiny lobsters: patterns of movement. 349–407. In
PHILLIPS , B. F. (ed.) The biology and management of lob-
sters. Vol. 1. Academic Press.
HOARE, B. 2009a. Animal migration: remarkable journeys by
air, land and sea. Natural History Museum, London.
-2009b. Animal migration: remarkable journeys in the wild.
Marshall Editions, London.
HOLMAN, J. D. and HAND, S. C. 2009. Metabolic depres-
sion is delayed and mitochondrial impairment averted during
prolonged anoxia in the ghost shrimp, Lepidophthalmus
louisianensis (Shmitt, 1935). Journal of Experimental Marine
Biology & Ecology, 367, 85–93.HOU, X.-G., S IVETER, D. J., ALDRIDGE, R. J. and
SILVETER, D. J. 2008. Collective behavior in an early Cam-
brian arthropod. Science, 322 (5899), 224 pp.
750 PALAEONTOLOGY , VOLUME 59
Page 9
---and SIVETER D. J. 2009. A new arthropod in
chain-like associations from the Chengjiang Lagerst€atte (Lower
Cambrian), Yunnan, China. Palaeontology, 52, 951–961.HUGHES, N. C. and CHAPMAN, R. E. 1995. Growth and
variation in the Silurian proetide trilobite Aulacopleura kon-
incki and its implications for trilobite palaeobiology. Lethaia,
28 (4), 333–353.-MINELLI , A. and FUSCO, G. 2006. The ontogeny of
trilobite segmentation: a comparative approach. Paleobiology,
32, 603–628.KANCIRUK, P. and HERRNKIND, W. F. 1978. Mass
migration of spiny lobster, Panulirus argus (Crustacea: Palin-
uridae): behavior and environmental correlates. Bulletin of
Marine Sciences, 28, 601–623.KARIM, T. and WESTROP, S. R. 2002. Taphonomy and
paleoecology of Ordovician trilobite clusters, Bromide Forma-
tion, south-central Oklahoma. Palaios, 17, 394–403.KIN, A. and BŁ A _ZEJOWSKI , B. 2013. A new species of
blind phacopid trilobite from the Late Devonian (early Fam-
menian) of Poland. Zootaxa, 3626 (3), 345–355.--2014. The Horseshoe Crab of the genus Limulus: liv-
ing fossil or stabilomorph? PLoS One, 9 (10), e108036. doi:
10.1371/journal.pone.0108036
KNELL , R. J. and FORTEY, R. A. 2005. Trilobite spines and
beetle horns: sexual selection in the Palaeozoic? Biology Letters,
1, 196–199.LINNANE, A., DIMMLICH, W. and WARD, T. 2005.
Movement patterns of the southern rock lobster, Jasus edward-
sii, of South Australia. New Zealand Journal of Marine &
Freshwater Research, 39, 335–346.MINELLI , A. 1992. Towards a new comparative morphology
of myriapods. Berichte des naturwissenschaflich-medizinischen
Vereins in Innsbruck. Supplementum, 10, 37–46.-2003. The development of animal form. Cambridge Univer-
sity Press.
-BRENA, C., DEFLORIAN, G., MARUZZO, D. and
FUSCO, G. 2006. From embryo to adult: beyond the
conventional periodization of arthropod development. Devel-
opment Genes & Evolution, 216, 373–383.MOORE, R. and McFARLANE, J. W. 1982. Migration of
the ornate rock lobsters, Panulirus ornatus (Fabricius), in
Papua New Guinea. Australian Journal of Marine & Freshwater
Research, 35, 197–212.PATERSON, J. R., JAGO, J. B., BROCK, G. A. and
GEHLING, J. G. 2007. Taphonomy and palaeoecology of
the emuellid trilobite Balcoracania dailyi (early Cambrian,
South Australia). Palaeogeography, Palaeoclimatology, Palaeoe-
cology, 249 (3–4), 302–321.PHILLIPS , B. F. 1983. Migrations of pre-adult western rock
lobsters, Panulirus cygnus, in Western Australia. Marine Biol-
ogy, 76, 311–318.RADWA �NSKI , A., KIN, A. and RADWA �NSKA, U. 2009.
Queues of blind phacopid trilobites Trimerocephalus: a case
of frozen behaviour of Early Famennian age from the Holy
Cross Mountains, Central Poland. Acta Geologica Polonica, 59,
459–481.-WYSOCKA, A. and G �ORKA, M. 2012. Miocene bur-
rows of the Ghost Crab Ocypode and their environmental sig-
nificance (Mykolaiv Sands, Fore-Carpathian Basin, Ukraine).
Acta Geologica Polonica, 64 (2), 217–229.-G �ORKA, M. and WYSOCKA, A. 2014. Badenian (Mid-
dle Miocene) echinoids and starfish from western Ukraine,
and their biogeographic and stratigraphic significance. Acta
Geologica Polonica, 64 (2), 207–247.SPEYER, S. E. and BRETT, C. E. 1985. Clustered trilobite
assemblages in the Middle Devonian Hamilton Group.
Lethaia, 18, 85–103.THOLLOT, P., KULBICKI , M. and HARMELIN-
VIVIEN, M. 1999. Trophic analysis and trophodynamic
functioning of mangrove fish fauna of New Caledonia. Comp-
tes Rendus de l’Acad�emie des Sciences, Series 3: Sciences de la
Vie, 322, 607–619.WILCOVE, D. S. 2008. No way home: the decline of the world’s
great animal migrations. Island Press, Washington, DC.
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