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Pristinaspinidae, a new family of Cretaceous kiwaiform
stem-lineage squat lobster (Anomura, Chirostyloidea)
S.T. Ahyong & C.N. Roterman
Ahyong, S.T. & Roterman, C.N. Pristinaspinidae, a new family of Cretaceous kiwaiform stem-lineage squat
lobster (Anomura, Chirostyloidea). In
Proceedings of the 5th-
Scrip ta Geolo gica, 147: 125-133, 1 pl., Leiden, October 2014.
-
Australia (shane.ahyong@austmus.gov.au-
KiwaPristinaspina, fossil.
The chirostyloid squat lobster Pristinaspina gelasina from the Upper Cretaceous of Alaska is most closely
related to members of the genus Kiwa
-
graphic position and molecular divergence estimates of extant chirostyloids supports its position in the
Pristinaspina
a new family, Pristinaspinidae. The chief distinction between the free-living pristinaspinids and vent- or
-
branchial regions in kiwaids, which meet in the mid-line and separate the cardiac region from the intes-
tinal region. The enlarged metabranchial regions of kiwaids may have improved respiration in poorly
ecology of kiwaiform squat lobsters, that is, the movement into chemosynthetic habitats.
Contents
Introduction ............................................................................................................................................................ 125
Systematic palaeontology ..............................................................................................................................
Acknowledgements ........................................................................................................................................... 129
References ................................................................................................................................................................ 129
Introduction
et al., 2009; Schnabel
et al., 2011; Tsang et al.et al., 2013). Recent revisions of the squat
lobster system (Schnabel & Ahyong, 2010; Ahyong et al.-
-
group, but the aforementioned phylogenetic studies have shown that the galatheoids
and chirostyloids are not sister groups, but appear to have convergently evolved a sim-
-
-
Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster.
et al.
record is presently poor, being known only from two species, Pristinaspina gelasina
Eouroptychus montema-
grensisEouroptychus corresponds to
the current concept of Chirostylidae, but the position of Pristinaspina is less clear. Pristi-
naspina-
of the Chirostylidae, however, Pristinaspina cannot be readily accommodated there, with
its supraorbital spines, broad, medially carinate rostrum and well-marked branchiocar-
spines and a median carina on the rostrum. Unlike eumunidids, Pristinaspina has neither
a spiniform rostrum nor a transversely striated carapace. The broad, carinate rostrum,
-
pace of Pristinaspina, Pristi-
naspina gelasina
Pristinaspi-
na
Systematic palaeontology
Superfamily Chirostyloidea Ortmann, 1892
Family Pristinaspinidae nov.
Type genusPristinaspina
Stratigraphic range
Diagnosis
regions; surface regularly dimpled, without transverse striae or dorsal spines, regions
-
praorbital spines slender, well developed. Carapace margins spinose, with 3 hepatic
marginal spines posterior to supraocular spines, 2 spines on anterior epibranchial mar-
gins, 1 metabranchial spine at base of branchiocardiac groove. Cervical groove well
-
branchial regions. Anterior part of branchiocardiac groove subparallel to cervical
groove, between them enclosing triangular mesobranchial and epibranchial regions;
epibranchial region slightly larger and more swollen than mesobranchial region. Car-
diac and intestinal regions fused, hourglass shaped, anteriorly as wide as metagastric
region, separating metabranchial regions.
Remarks
-
Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster.
gionalisation of pristinaspinids and kiwaids is similar, albeit somewhat less pronounced
-
regions in kiwaids, which are more expanded and meet in the midline, separating the
cardiac region from the intestinal region. Conversely, the metabranchial regions in pris-
tinaspinids, although wide, are clearly separated by the fused cardiac and intestinal
than strongly divergent cervical and branchiocardiac grooves; mesobranchial regions
slightly smaller, rather than markedly smaller than the epibranchial regions; and prom-
inently spinose rather than unarmed lateral carapace margins. For comparison with
is given below.
Shared morphological features between pristinaspinids and kiwaids, along with
stratigraphic position of P. gelasina
would also be possible (Ahyong et al.-
gene phylogenetic analysis, however, suggest that the common ancestor of Chirosty-
Cretaceous (Roterman et al., 2013). Thus, combined evidence from morphology, stratig-
-
waidae, supporting a kiwaiform clade. The former presence of Pristinaspina in deep
Kiwa, suggests that kiwaids may have evolved in deep
(Roterman et al., 2013).
Pristinaspina gelasina -
trichtian) non-chemosynthetic, siliciclastic deposits in Alaska. These deposits from the
deep continental slope have associated thalassinidean remains but no corals, indicating
-
mann, 2000). Thus, P. gelasina was probably free living, neither associated with live
et al.,
2010), nor chemosynthetic habitats, like modern kiwaids (Roterman et al., 2013). The
relatively swollen branchial regions of Pristinaspinidae compared to most other squat
Cervimunida and Pleuroncodes in the
more tolerant of less oxic conditions prior to the move by kiwaids to chemosynthetic
et al., 2010).
All known species of Kiwa
‘farm’ sulfur-reducing bacteria on which the animal feeds (Thurber et al., 2011). The
phylogeny of the few known species of Kiwa is consistent with a possible transition
Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster.
-
et al.
vice versa, however, remains to be
tested through discovery of additional species of Kiwa, although the distinction be-
et al., 2011). Regardless of the precise mode of transition, the late Paleogene/early
Neo
et al., et al., 2010), where methane seeps,
hydrothermal vents and non-chemosynthetic continental slope habitats are likely to
have been in very close proximity.
Either way, the ecological transition into arguably more extreme habitats might
account for the further expansion of the branchial regions in kiwaids as a means of
movement into chemosynthetic habitats. It is worth mentioning that the late Paleo-
et al., 2013) coincides with a dra-
-
cene/Oligocene transition (Pälike et al., 2012), possibly indicating that prior to this
-
tilated deep-sea may have been responsible for the widespread extinction of vent and
seep-associated megafauna, with present-day diversity the consequence of subsequent
event (Roterman et al., 2013), possibly later than other vent and seep endemic faunas
of kiwaids to ambient oxygen levels than many other chemosynthetic taxa, as evi-
-
nidae. Indeed, the indication, based on molecular divergences, that the other vent and
-
diated in these habitats more recently than many other taxa (Shank et al.-
hoek, 2013) raises the possibility that decapods as a whole are possibly evolutionarily
constrained by the internal placement of their branchiae under the carapace, thus lim-
-
ated conditions.
At present, the fossil record of clades neighbouring the chirostyloids is sparse. Lo-
misoids, endemic to southeastern Australia, have no known fossil record. Along with
Pristinaspina
many other decapods originated at high latitudes during the Cretaceous (Feldmann &
north and south, respectively. That both pristinaspinids and aegloids have Cretaceous
Tethyan origin for the chirostyloid-aegloid-lomisoid clade (Ahyong et al., 2011).
Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster. 129
Kiwaidae Macpherson, Jones & Segonzac, 2005
Type genus Kiwa
(monotypy).
Stratigraphic range
Diagnosis
praor-
-
regions; transverse or slightly inclined anteriorly either side of midline, always oblique
to cervical groove. Subtriangular mesobranchial and polygonal epibranchial regions.
Epibranchial region markedly larger than mesobranchial region. Cardiac region subtri-
angular, as long as or longer than wide, anterior margin convex; intestinal region trian-
gular, markedly wider than long. Cardiac and intestinal regions separated by medially
RemarksKiwa, with two described species,
K. puravidaK. hirsuta
-
et al., 2012) and pos-
et al., 2013).
Acknowledgements
Scotia Ridge and Southwest Indian Ridge kiwaids was funded by NERC Consortium
References
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Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster. 131
Also an explanation of the terms used in entomology; a calendar of the times of appearance and usual situa-
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132 Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster.
Plate 1
Pristinaspinidae
Fig. 1. Pristinaspina gelasina
Kiwaidae
Fig. 2. Kiwa puravida
Fig. 3. Kiwa hirsuta, courtesy of
Fig. 4. Kiwa sp., East Scotia Ridge.
Fig. 5. Kiwa sp., southwest Indian Ridge.
Scale bars equal 2 mm (Fig. 1) and 10 mm (Figs. 2-5).
Ahyong & Roterman. Pristinaspinidae, a stem-lineage squat lobster. 133