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wavenumber offsets between 1,000 and 1,800 cm
−1
(Kudryavtsev et al.
2001
). The
LabSpec program was used to estimate the dimensional parameters of the bands
(Rahl et al.
2005
).
Results
Py-GC-MS of the cuticle of the modern scorpion
Pandinus imperator
(Fig.
7.2a
,
Table
7.2
) and the horseshoe crab
Limulus polyphemus
(Fig.
7.2b
) refl ect the known
composition of living arthropod cuticles, which consist of chitin fi bres embedded in
a protein matrix interlinked by catechol moieties (Schaefer et al.
1987
, Fig.
7.2b
; See
Stankiewicz et al. (
1996
) for details on identifi cation and structure of fragment ions).
Thermochemolysis of
Limulus
cuticle refl ects the distribution of fatty acyl moieties;
C
16
and C
18
fatty acids were the most dominant (Fig.
7.2c
). Such acyl moieties are not
detected during pyrolysis of model chitin or protein compounds (Stankiewicz et al.
1996
); hence, the C
16
and C
18
fatty acyl moieties in the pyrolysate of
Limulus
and
modern scorpion likely derive from lipids associated with the cuticle.
No chitin or protein was detected in the eurypterid cuticles. Py-GC/MS analyses
of samples in this study revealed the breakdown products of an aliphatic polymer
with detected chain lengths typically extending from <C
9
to C
22
(Fig.
7.3
). Those
<C
9
were not detected as they probably eluted during the thermal hold time of the
MS. All the samples showed a very similar distribution, with the C
9
to C
15
alkane
and alkene homologues being the most abundant, irrespective of body part, species
and lithology (Table
7.1
). Benzene derivatives were also detected, but phenols and
polyaromatic hydrocarbons (naphthalene, anthracene) were absent. Pyrolysis of the
surrounding sediment resulted in no yield, due to its organic lean nature.
Thermochemolysis of the eurypterid cuticle yielded fatty acids ranging from C
7
to C
18
with an even over odd predominance (Fig.
7.4
). The most abundant fatty acyl
moieties were those with chain lengths of C
16
and C
18
. Hydrolysis of the cuticle in
basic conditions followed by thermochemolysis yielded a similar distribution of
fatty acyl moieties. No sulfur-bearing compounds were detected in the pyrolysate.
Raman scattering of areas of cuticle (Fig.
7.5
) revealed vibrational bands charac-
teristic of carbonaceous materials at 1,350 and 1,580 cm
−1
, which are commonly des-
ignated D(disordered) and G(ordered or graphitic), respectively. The ratio between the
two bands is temperature sensitive: with increased thermal maturity, the ordered band
Gband becomes more prominent (Beyssac et al.
2002
). Samples of
Eurypterusdekayi
,
E. lacustris
,
Pterygotussarlei
and
P. ventricosus
showed a similar band distribution—
a typical spectrum of
E. lacustris
(Fig.
7.5
), attesting to the similar maturity of all the
samples independent of body part and lithology. In contrast, the Raman spectra of the
adelophthalmid eurypterid and scorpion from Joggins previously analysed by
Stankiewicz et al. (
1998a
) revealed band parameters, such as a more pronounced peak
height of the G band than that of the D band (Fig.
7.5
), indicating greater thermal
maturity (Rahl et al.
2005
). Raman spectra of the scorpion from LoneStarLake indi-
cate a thermal maturity intermediate between the other two sample sets.
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