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Microfaunal analysis of the Wattonensis Beds (Upper Bathonian) of South Dorset

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  • Robertson, CGG

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The Wattonensis Beds (Upper Bathonian) are exposed in the low cliffs to the east of Rodden Hive Point (Dorset). This locality is famous for the abundance of the otolith fauna described in the 1960s. The presence of this otolith fauna is confirmed with new material collected in 2008. Along with the otoliths are a number of statoliths, the aragonitic bones found in the heads of squid- like cephalopods and almost certainly un-described. Many of the otoliths and statoliths are encrusted with adherent foraminifera, as are the numerous shell fragments found in these clays.
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MICROFAUNAL ANALYSIS OF THE WATTONENSIS BEDS (UPPER BATHONIAN)
OF SOUTH DORSET
M.B. HART, A. DE JONGHE, S.T. GRI MES, B. METCALFE, G.D. PRICE AND C. TEECE
Hart, M.B., De Jonghe, A., Grimes, S.T., Metcalfe, B., Price, G.D. and Teece, C. 2009. Microfaunal analysis of the Wattonensis
Beds (Upper Bathonian) of South Dorset. Geoscience in South-West England, 12, 134-139.
The Wattonensis Beds (Upper Bathonian) are exposed in the low cliffs to the east of Rodden Hive Point (Dorset). This locality is
famous for the abundance of the otolith fauna described in the 1960s. The presence of this otolith fauna is confirmed with new
m
aterial collected in 2008. Along with the otoliths are a number of statoliths, the aragonitic bones found in the heads of squid-
like cephalopods and almost certainly un-described. Many of the otoliths and statoliths are encrusted with adherent foraminifera,
as are the numerous shell fragments found in these clays.
School of Geography, Earth & Environmental Sciences, University of Plymouth,
Drake Circus, Plymouth, PL4 8AA, U.K.
(E-mail: mhart@plymouth.ac.uk).
Keywords: Wattonensis Beds, Bathonian, Dorset, otolith, statolith, foraminifera.
M.B. Hart, A. De Jonghe, S.T. Grimes, B. Metcalfe, G.D. Price and C. Teece
134
INTRODUCTION
In the geological literature about the Dorset Coast the
Wattonensis Beds of the Upper Bathonian are recorded as
containing one of the most abundant assemblages of Jurassic
otoliths in the U.K. (Stinton and Torrens, 1968; House, 1993;
Cox and Page, 2002). Stinton and Torrens (1968) indicate that,
in their experience, the average sample of clay from the
Bathonian in the U.K. yields 1 otolith per kg of sediment
while the Wattonensis Beds at Rodden Hive Point yielded the
‘extraordinary’ figure of 10 specimens per kg. The database on
which these judgments were made is, however, somewhat
limited with only the work of Frost (1924, 1926) and the
research of Stinton and Torrens (1968) recording the presence
of otoliths in Jurassic sediments. In our recent work on the
Wootton Bassett Mud Springs (Hart et al., 2006; Price et al.,
2009) we did find significant numbers of otoliths, although the
mechanism by which they were sampled is atypical (fluid mud
oozing from natural springs). Field samples were, therefore,
collected from the Wattonensis Beds on the shore of the Fleet
Lagoon in South Dorset in order to make a direct comparison
with the work of Stinton and Torrens (1968).
Rodden Hive Point (SY 599821) is located WSW of Langton
Herring on the shore of the Fleet Lagoon (Figure 1). The
section is almost inaccessible, backed by private land and often
rather muddy of access: permission should be sought, for both
visiting and sampling, from the Strangways Estate. About
90-100 m east of the point there are abundant, beautifully
preserved macrofossils littering the foreshore, all of which
appear to have been washed out from the Wattonensis Beds
(Cox and Page, 2002). Samples were collected from the
lumachelle that marks the Elongata Beds and the soft clays that
occur below, and to the west of, the shell bank. This is one of
the best exposures of the Wattonensis Beds which are ~1 m
thick (Figure 2). All the previous authors, beginning with
Stinton and Torrens (1968) describe the shell fragments, and the
otoliths recovered from these clays, as being encrusted with
‘microfaunal bryozoa and serpulids’. As part of our investigation
of the otoliths and the shell material from the succession
we have studied this epifauna and determined that the
overwhelming majority of the taxa are not bryozoans or
serpulids but adherent foraminifera. For comparison, shell
fragments from the mid-Upper Jurassic of Poland
(Pugaczewska, 1970) also carry abundant specimens of
serpulids, bryozoans and foraminifera (including taxa described
here).
OTOLITHS
Otoliths are the stato-acoustic organs of bony (teleost) fish
and are often quite well preserved as fossils as they are
composed of calcium carbonate (Stinton and Torrens, 1968;
Lowenstein, 1971; Hart et al., 2006). On each side of the fish
the ‘labyrinth’ has three otoliths which are located adjacent to
the sensory spots. The largest is the sagitta and this is located
in the sacculus. The second otolith lies in the lagena
(asteriscus) while the third is in the utriculus (lapillus). The
sagitta is the largest and most commonly described in the fossil
record. The side of the sagitta facing the median plane of the
body is the ‘inner side’ and is usually flatter in comparison to
the “outer side” that often shows a range of grooves or other
features.
In their account of Bathonian otoliths, many of which came
from the Wattonensis Beds of Rodden Hive Point, Stinton and
Torrens (1968) created ten new taxa which represent the whole
of the recovered fauna. Many of these taxa have been found
in this current investigation (Figure 3). Along with the otoliths,
in lesser numbers, are a number of similar microfossils that
have not been described previously. These are the statoliths.
Microfaunal analysis of the Wattonensis Beds
135
Figure 1. Locality map for the exposure of the Wattonensis Beds at Rodden Hive Point near Langton Herring, Dorset.
STATOLITHS
Statoliths are the small, hard, aragonitic stones which lie in
the fluid-filled cavities or statocysts within the cartilaginous
skulls of all living and probably all fossil members of the
Coleoidea (Clarke, 1978, 2003). Their aragonitic composition,
colour and size mean that they often co-occur with fossil
otoliths, although they are relatively little known from Jurassic
strata (Clarke et al., 1980a,b; Clarke and Maddock, 1988a,b;
Clarke, 2003). Although we have found a number of statoliths
associated with the otolith fauna in the samples from the
Wattonensis Beds, we cannot at present identify the parent
animal. In form and shape, these Bathonian statoliths are
similar in appearance to the only previous illustrations of a
Jurassic statolith (Clarke, 2003, figures 14, 15). Work on Jurassic
statoliths from the Bathonian and Callovian is on-going.
ADHERENT FORAMINIFERA
As indicated above, the majority of previous workers have
indicated that shell fragments and otoliths in the Wattonensis
Beds are covered in abundant bryozoans and serpulids. While
we cannot say that there are no serpulids or bryozoans in the
epifauna, all the specimens that we have seen are adherent
foraminifera. Such an abundance of foraminiferal epifauna is a
peculiar characteristic of the Jurassic clays in the U.K. and
elsewhere in Europe, where the incidence of such faunas
appears to be greater than in the Cretaceous or Tertiary
successions of the same area. In the Cretaceous, where both
calcareous (e.g. Bullopora) and agglutinated (e.g. Placopsilina)
taxa are known, it is probable that one or two specimens may
be found in most micropalaeontological samples. In the
Jurassic, however, it is often found that 90% (or more) of shell
fragments have at least one (or more) adherent taxon present.
In many cases there can be as many as 5 on each small shell
fragment or otolith.
Figure 2. Lithostratigraphy of a part of the Bathonian Callovian interval within the Geological Conservation Review Sites on the Dorset
Coast.
M.B. Hart, A. De Jonghe, S.T. Grimes, B. Metcalfe, G.D. Price and C. Teece
136
Adherent taxa are rarely described in detail (Armstrong and
Brasier, 2005; Murray, 1991, 2006) in texts on the life and
ecology of foraminifera and even reviews of foraminiferal
taphonomy (e.g. Herrero and Canales, 2002) give few details.
The principal publications on such taxa (especially in the
Jurassic) are by Macfadyen (1941), Barnard (1950a,b, 1952,
1953, 1958), Cifelli (1957, 1959, 1960), Gordon (1962, 1965,
1967), Adams (1962), Coleman (1974, 1982), Morris and
Coleman (1989) and Shipp (1978, 1989). Gordon (1965,
text-figure 11) illustrates three species from the Corallian
succession of southern England, all of which are pertinent to
the following discussion.
The genera represented include Bullopora Quenstedt 1956,
Vinelloidea Canu 1913 (= Nubeculinella Cushman 1930) and
Tolypammina Rhumbler 1895’. In a lengthy discussion of
adherent taxa, Adams (1962) has outlined the classification
problems surrounding this group and discussed the wall
structure of each of these genera. All of this work was in
advance of scanning electron microscopy and the compilation
of the taxonomic databases now in use (Loeblich and Tappan,
1964, 1987). Barnard (1958) summed up the problem thus: The
chief problems involved in a study of fossil adherent
foraminifera are due to the inadvertent mixing of genera by
some authors. This is perhaps due to the different states of
preservation of the specimens. In most cases it is necessary
to make extensive use of thin sections to determine the wall
structure.
In many specimens the initial chambers, or coil, are not
present and this does not allow inspection of one of the most
important taxonomic characters. Specimens of Nubeculinella
often become detached, and occur as ‘normal’ foraminifera in
the residues studied by micropalaeontologists. When this
happens it can be seen that some specimens have a lower
surface to their chambers while others do not. The taxonomic
(or taphonomic) significance of this is not known.
TAXONOMIC NOTES
The classification scheme of Loeblich and Tappan (1964,
1987) is being followed here as the revisions of Kaminski (2004,
2008) are not fully accepted by the community. In the case of
Tolypammina Loeblich and Tappan (1964) is followed as this is
the name by which this taxon is best known in the Jurassic,
rather than the suggested Palaeozoic replacement (Serpenulina
Chernykh).
Superfamily AMMODISCACEA Reuss, 1862
Family Ammodiscidae Reuss, 1862
Subfamily Tolypammininae Cushman, 1928
Genus Tolypammina Rhumbler, 1895
Type species Hyperammina vagans Brady, 1879
‘Tolypammina sp.’
Diagnosis: A species of Tolypammina(?) with a tubular,
meandrine, ne-grained, unbranching test. The aperture
appears to be a simple, terminal opening.
Discussion: Tolypammina is described by Loeblich and
Tappan (1987) as a Late Palaeozoic form, while the original
definition of the ‘type species’ as Hyperammina vagans Brady,
1879 is a form from the Recent. It is quite clear that neither a
Recent form or a Palaeozoic taxon provide an appropriate name
for this relatively simple, agglutinated form that has a given
range of Ordovician to Holocene (Kaminski, 2008). This is one
of the rarer taxa in the Jurassic (see Macfadyen, 1941; Barnard,
1950a, 1958; Gordon, 1965) and until we have more material
it is not possible to resolve the question of its full range in
the Jurassic, or the most appropriate name for the genus. No
complete specimens have been found in the Wattonensis Beds.
Microfaunal analysis of the Wattonensis Beds
137
Figure 3. Scanning electron microscope images of some of the microfauna from the Wattonensis Beds at Rodden Hive Point, Dorset.
A. Leptolepis sp. cf. L. tenuirostris Stinton & Torrens (1968); B. Pholidophorus sp. cf. P. prae-elops Stinton & Torrens (1968); C. Bullopora
rostrata Quenstedt (1857); D. Bullopora rostrata Quenstedt, close-up of stolon-like neck between two chambers seen in centre-left of
photograph C; E. unidentified otolith; F. unidentified statolith, probably new taxon. Scale bars all 500 µm except D which is 100 µm.
Superfamily CORNUSPIRACEA Schultze, 1854
Family Nubeculariidae Jones, 1875
Subfamily Nubeculinellinae Avnimelech and Reiss, 1954
Genus Vinelloidea Canu, 1913
Type species Vinelloidea crussolensis Canu, 1913
Vinelloidea ‘bigoti’ Cushman, 1930
Diagnosis: A species of Vinelloidea with an imperforate
‘milky white’ test of attached uniserial chambers that follow a
proloculus, coiled second chamber and uncoiled later growth
stages. There is a simple aperture at the open end of the last
chamber.
Discussion: This species is better known as Nubeculinella
bigoti but Loeblich and Tappan (1987, p.323) suggest that
Vinelloidea crussolensis which was initially described as an
adherent bryozoan may be a senior synonym. The illustrations
provided by Loeblich and Tappan (1987, plate 333) are not
totally convincing and we have retained the specific name
‘bigoti’ for the present. This species has been fully described
by Adams (1962), who gives the range as ?Lower Lias
Kimmeridgian. This species has previously been recorded from
M.B. Hart, A. De Jonghe, S.T. Grimes, B. Metcalfe, G.D. Price and C. Teece
138
the Oxfordian – Kimmeridgian by Shipp (1989) and the
Oxfordian by Gordon (1965). De Jonghe (2009) records it as
abundant on shell fragments in the Phaeinum Subzone
(Callovian) in Wiltshire. It is, overwhelmingly, the most
a
bundant adherent taxon in the material from the Wattonensis
Beds and the Callovian.
This species frequently detaches from the host surface
during taphonomy (or sample processing) and the 125-250 µm
size fraction often contains large numbers of this species (often
fragmented). This makes any taxonomic counts of genera/
species in Jurassic strata problematic as: (1) How does one
assess fragments (especially as the proloculus is almost never
seen)? (2) How does one assess abundances in different size
f
ractions as detached specimens are often in the 63-125 µm or
125-250 µm size fractions, while those still attached will be in
the 250-500 µm or >500 µm size fractions.
Superfamily NODOSARIACEA Ehrenberg, 1838
Family Polymorphinidae d’Orbigny, 1839
S
ubfamily Webbinellinae Rhumbler, 1904
Genus Bullopora Quenstedt, 1856
Type species Bullopora rostrata Quenstedt, 1857
Bullopora rostrata Quenstedt, 1857
Diagnosis: A species of Bullopora with adherent, hemispheri-
cal, tear-drop shaped chambers that may be closely adjacent
or, more normally, separated by stolon-like necks. The wall
is calcareous, perforate with a smooth surface (when well-
preserved).
Discussion: Gordon (1965, text-figure 11(20)) illustrates a
form with quite closely oppressed chambers (rather than
connecting necks) as B. globulata. The chamber arrangement
is slightly different to that shown in the type figure by Barnard
(1950a, p.352, text-figure 1e). In some of our material the
typical stolon-like necks between the chambers only appear
later in growth, earlier chambers being much more closely
adjacent. Barnard (1958) attempted to describe the evolution
of Bullopora, but our experience indicates that this may be
an overly simplistic view. Even in one sample we see a
great range of variation in chamber shape, length of any
interconnecting necks and nature of any changes in growth
direction. In many of our specimens from the Wattonenesis
Beds and the Oxford Clay Formation some chambers (usually
the earlier ones) taper into the neck quite gradually, while in
the later chambers the more rounded chambers are joined by
necks that are more distinct and often change the direction of
growth of the individual.
SUMMARY
There has been relatively little work on the Bathonian
foraminifera in the United Kingdom and the fauna from the
Wattonensis Beds of the Dorset Coast is virtually un-described:
see Cifelli (1959) for a general account of Bathonian
foraminifera. The adherent foraminifera, which are abundant,
have their own particular problems as indicated above. Why
the Middle Jurassic should contain such an extensive fauna of
adherent taxa is also unknown. Colonized shell fragments,
otoliths and statoliths must have been available for a certain
length of time on the sea floor to allow the settlement of the
protozoa and its subsequent growth. As we know little about
rates of growth and chamber production in adherent
foraminifera, this colonization may just represent one ‘season’
and this might go some way to explaining the frequency,
though not why we do not see this in comparable clays in other
parts of the Mesozoic (e.g. Gault Clay Formation in the
mid-Cretaceous).
The statoliths and otoliths also require further work but, as
our database for the Middle and Upper Jurassic expands, it is
possible to identify the stratigraphic significance of a number of
key taxa. Unfortunately we are never likely to determine from
which organisms they are derived unless a lagerstätte like the
Christian Malford Squid Bed (Wilby et al., 2004, 2006) yields an
animal with the otoliths or statoliths still within the soft tissue
o
f the parent organism.
AC
KNOWLEDGEMENTS
The authors thank Malcolm Clarke for advice on Jurassic
statoliths and for sharing some of his data with us. The staff of
the Electron Microscope Centre in the University of Plymouth
are thanked for their assistance. Dr Philip Copestake is thanked
f
or his thorough review and advice. Dr Christopher Smart is
thanked for preparing the final version of Figure 3.
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... An example of such an isolated occurrence is that recorded by Hart et al. (2009) from the Wattonensis Beds (Bathonian) of Rodden Hive Point near Langton Herring (Dorset). Material from this succession has yielded otoliths in the past (Stinton and Torrens 1968) and our material also contained a number of otoliths (Hart et al. 2009, fig. 3) and very rare statoliths ('morphospecies' Jurassic sp. ...
... An example of such an isolated occurrence is that recorded by Hart et al. (2009) from the Wattonensis Beds (Bathonian) of Rodden Hive Point near Langton Herring (Dorset). Material from this succession has yielded otoliths in the past (Stinton and Torrens 1968) and our material also contained a number of otoliths (Hart et al. 2009, fig. 3) and very rare statoliths ('morphospecies' Jurassic sp. D). ...
... 43c). Donovan (2006, p. 677) also indicates that the specimens of P. huxleyi are (mainly) from the Black Ven Marls Member of the Charmouth Mudstone Formation (Obtusum Chronozone), with one specimen Hart et al. 2009 for location details). Scale bar is 1 mm labelled as 'Monmouth Beach', west of Lyme Regis. ...
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The occurrence of statoliths within the Jurassic succession of south-west England and other parts of Europe is reviewed. Five ‘morphospecies’ have been identified, ranging in age from Hettangian to Kimmeridgian. With so little published information on statoliths, the presently known geological record is incomplete, although new occurrences are continually being discovered. The occurrence of statoliths, in the absence of soft-bodied fossils, may ultimately provide a more complete indication of the distribution of the soft-bodied host animals. At the present time, however, only one of the statolith ‘morphospecies’ can be, tentatively, linked to a known species of teuthid.
... Jurassic statoliths (Fig. 3) have yet to be described in any detail as there are only a few references to them in the literature (Clarke et al. 1980a(Clarke et al. , 1980bClarke and Maddock 1988b;Clarke 2003;. Otoliths, which are of similar appearance, are the aragonitic, stato-acoustic organs of bony (teleost) fish and have a betterknown, though still limited, fossil record (e.g., Frost 1924Frost , 1926Neth and Weiler 1953;Rundle 1967;Stinton and Torrens 1968;Hart et al. 2009;Nolf 2013). Some of these publications include illustrations of what are probably statoliths, though they were not identified as such at the time of publication (e.g., Frost 1926, figs. ...
... In Core 10, the elevated levels of statolith abundance extend from 0.25 m down-core to 4.25 m down-core, with the highest levels of abundance at 2.70 m down-core. Otoliths show a similar pattern (Fig. 6), although their numbers are always below that of the statoliths: a reversal of the normal situation where otoliths invariably dominate (see Clarke 2003, p. 43;Hart et al. 2009). ...
... Otoliths (Lowenstein 1971;Nolf 2013) are the stato-acoustic organs of bony (teleost) fish and are better known than the statoliths, especially in Cenozoic sediments. Jurassic records are relatively sparse and there are few well-known taxa with which to compare new records (Frost 1924(Frost , 1926Neth and Weiler 1953;Rundle 1967;Stinton and Torrens 1968;Patterson et al. 1993;Patterson 1998Patterson , 1999Hart et al. 2009;Price et al. 2009;Nolf 2013). In the samples from Core 10 a number of taxa have tentatively been identified (Fig. 3A-3C) and the distribution of the otoliths in the core shown in Figure 6. ...
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In the shell-rich, laminated clays of the Phaeinum Subzone (Athleta Zone, upper Callovian, Middle Jurassic) of the Peterborough Member of the Oxford Clay Formation, large numbers of statoliths and otoliths have been recovered. This apparent mass mortality is associated with the Christian Malford Lagerstätte in which there is exceptional, soft-bodied preservation of coleoid fossils. Statoliths are the aragonitic 'stones' that are found in the fluidfilled cavities (or statocysts) within the cartilaginous head of all modern and probably many fossil coleoids. Jurassic statoliths are largely undescribed and there are no known genera or species available to aid their classification. Otoliths, which may be of somewhat similar appearance, are the aragonitic stato-acoustic organs of bony (teleost) fish. These are more familiar to micropaleontologists and have a better known, though limited, fossil record. The abundance of statoliths in the Phaeinum Subzone at Christian Malford may indicate a mass mortality of squid that extends over some 3 m of strata and, therefore, a considerable interval of time. This has been tentatively interpreted as a record of a breeding area (and subsequent death) of squid-like cephalopods over an extended period of time rather than a small number of catastrophic events.
... Specimens figured by Clarke apparently lost[11]. First described by[14] (Fig. 3F)as "unidentified statolith, probably new taxon", then named "sp. D" by[10] (Fig. 2G: refiguration of specimen in[14],Fig. ...
... First described by[14] (Fig. 3F)as "unidentified statolith, probably new taxon", then named "sp. D" by[10] (Fig. 2G: refiguration of specimen in[14],Fig. 3F) with age precision (Bathonian stage). ...
... An example of such an isolated occurrence is that recorded by Hart et al. (2009) from the Wattonensis Beds (Bathonian) of Rodden Hive Point near Langton Herring (Dorset). Material from this succession has yielded otoliths in the past (Stinton and Torrens 1968) and our material also contained a number of otoliths (Hart et al. 2009, fig. 3) and very rare statoliths ('morphospecies' Jurassic sp. ...
... An example of such an isolated occurrence is that recorded by Hart et al. (2009) from the Wattonensis Beds (Bathonian) of Rodden Hive Point near Langton Herring (Dorset). Material from this succession has yielded otoliths in the past (Stinton and Torrens 1968) and our material also contained a number of otoliths (Hart et al. 2009, fig. 3) and very rare statoliths ('morphospecies' Jurassic sp. D). ...
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In September 2014, the 9th International Symposium Cephalopods—Present and Past (ISCPP) and the 5th International Coleoid Symposium were held at the University of Zurich. The numerous contributions from two joint symposia fill more than one special issue. After the first special issue, which was published in 2015 in the Swiss Journal of Palaeontology (Vol 134, Issue 2), the present second special issue also contains contributions from all fields of research on fossil and Recent cephalopod. In this editorial, we provide a short obituary honouring Fabrizio Cecca and report from the three conference field trips.
... The former subfamily includes, for instance, the genus Bullopora Quenstedt, 1856, whose species are very common encrusters on Jurassic and Cretaceous belemnite rostra and other substrates (e.g. Adams, 1962;Pugaczewska, 1965;Hart et al., 2009) and who show a similarity in segmentation to C. enigmaticum. A specimen from the Marnes de Dives Formation is illustrated in Fig. 6c-d. ...
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A single specimen of an enigmatic new attachment etching, together with an unknown calcareous encruster partly preserved in situ, has been identified on a belemnite rostrum from the Marnes de Dives Formation (Callovian, Middle Jurassic) of the Falaises des Vaches Noires in Normandy, France. The trace fossil, here established as the new ichnotaxon Circumpodichnus serialis igen. et isp. n., is a uniserial arrangement of very shallow depressions, oval to fusiform in outline, with peripheral pouches and central pits. The trace maker has a morphology unlike any other known calcareous epibiont, fossil or recent, and is consequently described as the new microproblematicum Circumpodium enigmaticum gen. et sp. n. Its calcitic skeleton is composed of a chain of segments with perforate basal and lateral walls, anchored to the attachment trace in the substratum by vertical protrusions in the centre and feet-like protrusions in the periphery. The hypothetical upper wall of the segments was either organic-walled and has decayed or it was calcitic and has been abraded. Based on morphological criteria and the capacity to bioerode, C. enigmaticum can best be compared to encrusting bryozoans and foraminiferans. Candidate bryozoans are aberrant arachnidiid ctenostomes, early cheilostomes, or stomatoporid cyclostomes. Among the foraminiferans, webbinellid or ramulinid polymorphinids are closest in their characters. In addition, tintinnid or folliculinid ciliophorans are considered as an alternative interpretation, and similarities to the Palaeozoic microproblematicum Allonema are discussed.
... All fractions were weighed prior to picking and/or counting. In the case of foraminifera a minimum of 250-300 individuals were counted in each size fraction, but the ostracods, otoliths, statoliths (Hart et al., 2009(Hart et al., , 2013(Hart et al., , 2015a(Hart et al., , 2016aClarke, 2003;Clarke and Hart, 2018) and arm hooks (Hart et al., 2016a(Hart et al., , 2019 were treated differently as, particularly in the case of statoliths, there are no counting protocols to follow. Weighing samples to determine foraminiferal numbers was undertaken but, as many of the specimens are in-filled with pyrite, any calculations based on these figures would probably be invalid. ...
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The Christian Malford lagerstätte in the Oxford Clay Formation of Wiltshire contains exceptionally well-preserved squid-like cephalopods, including Belemnotheutis antiquus (Pearce). Some of these fossils preserve muscle tissue, contents of ink sacks and other soft parts of the squid, including arms with hooks in situ and the head area with statoliths (ear bones) present in life position. The preservation of soft-tissue material is usually taken as an indication of anoxic or dysaerobic conditions on the sea floor and within the enclosing sediments. Interestingly, in the prepared residues of all these sediments there are both statoliths and arm hooks as well as abundant, species-rich, assemblages of both foraminifera and ostracods. Such occurrences appear to be incompatible with an interpretation of potential sea floor anoxia. The mudstones of the Oxford Clay Formation may have been compacted by 70 %–80 % during de-watering and burial, and in such a fine-grained lithology samples collected for microfossil examination probably represent several thousand years and, therefore, a significant number of foraminiferal life cycles. Such samples (even if only 1–2 cm thick) could, potentially, include several oxic–anoxic cycles and, if coupled with compaction, generate the apparent coincidence of well-preserved, soft-bodied, cephalopods and diverse assemblages of benthic foraminifera.
... Present also through the Early Cretaceous are stem group halecostomes (y = extinct): Holostei, Pycnodontiformesy, Amiidae, Pholidophoridaey, Leptolepidaey, Pachycormidaey, Aspidorhynchidaey and Ichthyodectidaey (Benton, 2015). The majority of English Mesozoic otoliths have been assigned to the Pycnodontiformes (Stinton and Torrens, 1968), Pholidophoridae (Harte et al., 2009;Stinton and Torrens, 1968), Leptolepidae (Frost, 1924(Frost, , 1926Harte et al., 2006;Stinton and Torrens, 1968), Elopomorpha (Harte et al., 2006;Stinton, 1973), and Amiidae (Harte et al., 2006;Rundle, 1967), a smaller number to Euteleostei (Stinton and Torrens, 1968) and one to the non-teleost clade Chondrostei (Stinton and Torrens, 1968). ...
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Teleostean saccular otoliths from the upper part of the late Hauterivian Lower Weald Clay Formation of the Wealden Supergroup exposed at Langhurstwood Quarry, West Sussex, UK, and Clockhouse Brickworks, Surrey, UK are described for the first time. Two new species of the genus Leptolepis, Leptolepid wealdensis and Leptolepis toyei are described.. Many of the specimens are densely packed on individual bedding planes and they are interpreted as coprocoenotic accumulations. Additional mechanisms of deposition and concentration are discussed, in particular wave action. Ontogenetic series show isometric growth of the otoliths, and some specimens show growth rings on two orders of magnitude.
... There are also the otoliths (fish ear bones) and statoliths (squid ear bones) that belong to animals that live at various depths in the same water column. Price et al. (2009), using well-preserved material from the unusual locality of the (Royal) Wootton Bassett Mud Springs for an analysis of stable isotopes, were able to compare the possible sea floor temperatures with those prevailing in the overlying water column A similar investigation of the Wattonensis Beds of South Dorset (Stinton and Torrens, 1968;Cox and Page, 2002;Hart et al., 2009) also demonstrated the validity of this approach (Price and Teece, 2010). ...
Article
Statoliths, in modern cephalopods, are the paired calcareous ‘stones’ that lie in two adjacent cavities (or statocysts) within the cartilage of the head. The stones are generally 0.5–2.0 mm in length and appear to be formed of aragonite. Statoliths often co-occur with fish otoliths, and being of similar appearance, size, colour, etc., this has caused confusion in the past. It was only towards the latter part of the twentieth century that it was recognized that statoliths could occur as fossils. © 2019 John Wiley & Sons Ltd, The Geologists' Association & The Geological Society of London
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Statoliths are, following the work of Clarke, now known to exist in the fossil record from the Lower Jurassic to Recent, though few micropalaeontologists know of their existence. Despite working on many thousands of Cretaceous residues, MBH has no record of statolith-like microfossils from the Cretaceous, though squid hooks have been recorded. Within the chalk facies this may be a result of dissolution of the aragonitic statoliths as other aragonitic microfossils (e.g. epistominid foraminifera) are also rare or nonexistent. It is important that such microfossils are noted (and described) by those working on microfossil residues in order that their full potential as palaeoenvironmental indicators is attained.
Chapter
The labyrinth represents the final stage in the process of submergence of neuromast organs of the lateral line type, and it has become completely or, at any rate, almost completely, separated from the outside medium and enclosed in the brain case. The ductus endolymphaticus maintains a tenuous connection with the outside world in the elasmobranchs only. The typical subdivision of the laybrinth into semicircular canals and otolith organs is phylogenetically fundamental, and is found in the labyrinth of the cyclostomes and in the fossil ostracoderm Kiaermpis. Two types of otoliths are known. The first is solid and of a constant shape characteristic of the species and in fact of the specific otolith organ within the labyrinth. The solid otoliths are anchored to the membranous wall of the labyrinth by systems of connective tissue strands functioning like guy ropes. Such structures are sparingly developed in connection with paste like otolithic masses. In the latter , the otolithic mass of one otolith organ can be continuous with that of another. In the elasmobranch labyrinth, such continuity has been observed between otolithic masses in sacculus and lagena.
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This paper is a contribution to the long-continued researches on the Dorset Lias by Dr W. D. Lang, F.R.S., who collected the described material. Some 700 mounted specimens from the Lower Lias (davoei zonc) of the Dorset coast have been studied. They are ascribed to six families, twenty genera, and fifty-five species; of these, eleven genera and forty-five species belong to the family Lagenidae. One genus and species, Carixia langi, and one other species, Lagena davoei, are described as new, and two new names are proposed to replace invalid names. There were studied for comparison certain of the few described English Lias faunas, some described French and German material, and a number of well-preserved but undescribed faunas from various Lias horizons and different English localities. This has yielded provisional evidence of the zonal ranges of the Dorset species. Some forms of Frondicularia were found to provide useful horizon markers. A tentative correlation is given of the zoning of the Lias by various authors of papers on Lias Foraminifera; there are notes on the horizons of some described Lias faunas, and a review of previous work on British Lias Foraminifera. Study of Jurassic Foraminifera has been comparatively neglected for many years, though there is a recent German revival. Some lengthy synonymies are therefore necessary. Certain less-known forms are discussed in detail; they were inadequately described and figured, so that they have hitherto been wrongly placed. It has thus been possible to rectify the systematic position or status of the genera Involutina, Problematina and Bullopora. The appearance in the Lias of Bolivina and Plectofrondicularia is demonstrated, genera usually stated not to occur in rocks of age earlier than the Cretaceous. Foraminifera thrived in the muddy Lias seas in whose clay deposits their shells are well preserved. There was a rapid evolution of new types, particularly of the predominating Lagenidae. In this family there appears to be wide variation within some of the groups, where neither 'species' nor even 'genera' are sharply defined. The bulk of the paper is taken up by the systematic description of the Foraminiferal fauna; all the recorded forms are figured. There is a reference list of some eighty-nine papers, mainly on Jurassic Foraminifera.
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A systematic study of the foraminifera from the Lower Lias of one was undertaken with a view to establishing a range-chart of the various species for application to other areas. The problems of nomenclature and synonymy, although studied, are outside the scope of the present paper and are consequently only briefly mentioned. The difficulties in correctly assigning specimens of Lenticulina to previously described species are dealt with, and it was found that examining the trends within a "plexus" gave best results. A range-chart shows that certain species are important stratigraphically and these forms are discussed.