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James Lamsdell's
Eurypterids.co.uk
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My
research thus far has focused around the palaeobiology, phylogeny
and evolution of the eurypterids, although my interests extend
far beyond this single group. I studied stylonurine eurypterids
for my Masters' at the University of Bristol, focusing particularly
on redescribing the species Drepanopterus abonensis and
the phylogeny of the suborder. Since finishing at Bristol I have
continued to work on eurypterids, including new stylonurines from
Arctic Canada, Late Devonian stylonurines from Pennsylvania and
the scottish Silurian eurypterid fauna of the Pentland Hills.
Beyond
simple descriptive work I have been focusing on a number of different
aspects of eurypterid palaeontology; the phylogeny of the Mixopteroidea,
the dual evolution of sweep-feeding in Stylonurina, primitive
characters in Eurypterida and the evolution of swimming, the relationship
of eurypterids and scorpions and a reevaluation of Romer's theory
on eurypterid and vertebrate competition. I am also in close contact
with David Marshall regarding the phylogeny of the chasmataspids
(an obscure chelicerate order with close links to eurypterids)
and the identification of the closest eurypterid ancestor.
Below
are summaries of my different research projects; click on the
links for further information. If you wish to discuss any of my
projects with me feel free to email.
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The
redescription of Drepanopterus abonensis - with
Simon Braddy and Erik Tetlie
Funded by the Palaeontological Association
The
primary focus of my MSc thesis; to redescibe Drepanopterus
abonensis, known from a single locality at Portishead,
near Bristol. Originally described in 1951, the rediscovery
of the site in 2004 and subsequent excavations there has
turned out a great deal of new material. Analysis of this
material showed the morphology of D. abonensis
to be drastically different to as originally described,
indicating a relationship with the Carboniferous sweep-feeding
hibbertopterids.
--now
published-- |
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The
systematics and phylogeny of the Stylonurina - with Simon
Braddy and Erik Tetlie
Funded by the Palaeontological Association
A
further objective of my MSc was to resolve stylonurine phylogeny;
while the phylogeny of the suborder Eurypterina is relatively
well resolved, Stylonurina have usually been included in
analyses in a massively cut-down form and the relationships
between families (and the components of those families)
are largely unknown. Furthermore, the hibbertopterids have
been considered to represent a separate order outside of
Eurypterida. My results suggest that hibbertopterids are
highly derived stylonurines, and that the suborder consists
of four superfamilies with metastoma shape being a highly
important family-level character.
--now
published-- |
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Romer's
theory reevaluated - with Simon Braddy
In
the 1930s Alfred Romer proposed that competition and predation
pressure from eurypterids was the driving factor in the
evolution of dermal armour in vertebrates. In recent years
the theory has fallen out of favour among vertebrate workers,
however comparisons of early jawed vertebrate and eurypterid
diversity have always treated eurypterids as a single group.
By splitting eurypterids into their two suborders, one being
nektonic predators and the other benthic scavengers, there
does appear to be some correlation between the evolution
of large size and ultimate extinction of swimming eurypterids
and the radiation of jawed vertebrates. Stylonurines however
show no such correlation due to their inhabiting a different
ecological niche, and their development of large body sizes
seems linked to environmental factors.
--now
published-- |
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Stylonurina
from Arctic Canada - with Simon Braddy, Liz Loeffler and
David Dineley
During
the 1970s David Dineley led several expeditions to Prince
of Wales Island in Arctic Canada and discovered a number
of armoured fish localities. A number of eurypterid specimens
were also discovered and brought back to the University
of Bristol, but are only now just being described. As well
as fragments of pterygotid there are two well-preserved
stylonurine specimens; a small individual that probably
represents a new genus and a specimen that is the same species
as a massive stylonurine described from the same strata
by Plotnick and Elliott in 1995. These add to an increasingly
diverse fauna of Early Devonian canadian euryperids, including
Drepanopterus, Erieopterus and Carcinosoma.
--now
published-- |
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Redescription
of 'Nanahughmilleria' conica
Funded by the Palaeontographical Society
Originally
described by Malcom Laurie in 1892, 'Nanahughmilleria'
conica is one of the most common eurypterids found in
the Pentland Hills. Work in my MSc thesis, along with Erik
Tetlie's, suggested that 'N'. conica was actually
a basal member of the Eurypterina and may have been cogeneric
with some of the 'Drepanopterus' species also found
at the locality. Study of all the known specimens has shown
that they probably all belong to the same species, and that
there may be a degree of sexual dimorphism within the population.
Furthermore, they belong with enigmatic species from Norway
and the US as part of a new genus. |
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Late
Devonian Stylonurina from Pennsylvania
Stylonurine
eurypterids have been known from the Late Devonian of Pennsylvania
for over a century; the most well-known is Hallipterus, however
several more enigmatic species (Parastylonurus (?) beecheri,
Stylonurella (?) arnoldi and Stylonurus (?) shaffneri)
are also found in the area. Their generic-level assignment
has proven problematic due to the lack of suitable characters,
however given our new knowledge of stylonurine systematics
I believe it is now possible to resolve their affinities;
P. (?) beecheri and Stylonurus (?) shaffneri
can be assigned to existing genera while Stylonurella
(?) arnoldi represents a new genus of eurypterid. |
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Redescription
of Moselopterus - with Markus Poschmann
Funded by the Palaeontographical Society
On a recent
trip to Frankfurt in Germany I took the opportunity to study
the type material of Moselopterus ancylotelson
and M. elongatus, deposited in the Senckenberg
Museum by Størmer in 1974. I also had the great fortune
to see new specimens of Moselopterus held in Markus
Poschmann's personal collection. Reviewing the type material
in light of the new specimens and current knowledge of basal
eurypterine relationships sheds doubts on some of the features
described by Størmer and on the status of the two
German species; while for the large part the original work
of Størmer is accurate it is obvious there are some
descrepancies - especially regarding appendage V - that
need resolving. |
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Drepanopterus
pentlandicus, the oldest Hibbertopteroid
Funded by the Palaeontographical Society
The
genus Drepanopterus represents a transitionary stage
between the 'normal' scavenging stylonurines and the derived
sweep-feeding hibbertopterids. D. pentlandicus, from
the Pentland Hills in Scotland, therefore represents the oldest
known hibbertopteroid eurypterid. Since the redescription
of D. abonensis questions have been raised as to
whether the Devonian Drepanopterus represents a separate
genus. Study of the D. pentlandicus specimens has
confirmed the cogeneric nature of the two species, and revealed
further evidence of the sister-group relationship of the Kokomopteroidea
and Hibbertopteroidea. Several beautiful specimens, unfigured
by Laurie in his original description, have been found in
the collections. Using these I am to directly compare the
sweep-feeding methods of the Hibbertopteroidea and the Stylonuridae. |
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Phylogeny
of the Rhenopteridae
The Rhenopteridae are the most enigmatic of the stylonurine
families. Previously thought to consist of solely Rhenopterus,
recent work has added several Silurian eurypterids to their
numbers as well as the oldest known eurypterid, Brachyopterus.
There is still much that needs doing if we are to fully understand
this primitive and phylogenetically important family; new
discoveries in Canada and the US indicate that rhenopterids
have a larger geographic and temporal range than previously
supposed, and some Stylonurina incertae sedis genera
from Norway may have rhenopterid affinities. A focused analysis
of rhenopterids should help us more clearly understand the
progression of character transformations within the group,
aid in assigning several problematic taxa and assist in recognising
primitive character states within Eurypterida. |
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Phylogeny
of the Mixopteroidea
Funded by the Palaeontographical Society
If
Rhenopteridae is the most unresolved stylonurine family, then
Mixopteroidea is the most unresolved of the Eurypterina. There
are several key issues that need resolving; where does Megalograptus
fit into the eurypterids, is Mixopteroidea two clades or a
single one, is Carcinosoma undersplit, and what is
the character polarity within the group. Analysis of 'Carcinosoma'
scoticus from the Pentland Hills suggests it is not a
true Carcinosoma, while a preliminary phylogenetic
analysis of the clade shows promising results but really needs
Megalograptus integrated before anything meaningful
about their evolution can be deduced. |
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Updating
Tollerton 1989
Tollerton
in 1989 set out a series of morphological standards to which
all eurypterid descriptions have since adherred. In the last
twenty years, however, a number of new discoveries and changes
in classification has somewhat dated this system. I hope to
update the system, adding the hibbertopterids (excluded from
Eurypterida by Tollerton) and several types of appendages
not previously identified. I also intend to somewhat simplify
it, separating ornamentation from appendage classification
and the influence of palpebral lobes from lateral eye shape,
and reflect the variation seen among paddles of a single type
between genera. |
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The
evolutionary relationships of eurypterids and scorpions
The
position of Scorpionida is a key to the understanding of
arachnid evolution. In the past much has been made of the
similarities between scorpions and eurypterids, particularly
genera like Mixopterus with its caudal postabdomen
and curved telson. The publication of a partial redescription
of Rhenopterus, now identified as having a caudal
postabdomen and curved telson, led me to thinking about
which would be most parsimonious as a scorpion ancestor,
Rhenopterus or Mixopterus. I am keen to
take this further, and my research into the Rhenopteridae
and primitive character states in eurypterids is highly
suggestive of a sister-group relationship between scorpions
(and all other arachnids) and eurypterids without scorpions
having actually evolved from within the eurypterid tree. |
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The
Cottonwood Canyon pterygotid - with David Legg
In his
1986 posthumous scorpion monograph Kjellesvig-Waering mentioned
a 'Pterygotus mcgrewi' from Cottonwood Canyon,
Wyoming. This taxon has never been officially described.
Reexamination of the intended holotype of this species reveals
that it probably belongs within the genus Jaekelopterus,
and that it might be synonymous with a Jaekelopterus
species from the nearby Beartooth Butte.
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