Taphonomic Analysis of Amphibian and Squamate

Transcription

International Journal of Osteoarchaeology
Int. J. Osteoarchaeol. 22: 616–635 (2012)
Published online 26 August 2011 in Wiley Online Library
(wileyonlinelibrary.com) DOI: 10.1002/oa.1275
SPECIAL ISSUE PAPER
Taphonomic Analysis of Amphibian and
Squamate Remains from El Harhoura 2
(Rabat-Témara, Morocco): Contributions
to Palaeoecological and Archaeological
Interpretations
E. STOETZEL,a* C. DENYS,b S. BAILON,a,c M. A. EL HAJRAOUId AND R. NESPOULETa
a
Muséum National d’Histoire Naturelle, Département de Préhistoire - UMR 7194, Paris, France
Muséum National d’Histoire Naturelle, Département Systématique et Evolution - UMR 7205, Laboratoire de
Zoologie Mammifères et Oiseaux, Paris, France
c
Muséum National d’Histoire Naturelle, Département Ecologie et Gestion de la Biodiversité - UMR 7209,
Laboratoire d’Anatomie Comparée (CP56), Paris, France
d
Institut National des Sciences de l’Archéologie et du Patrimoine, Angle rues 5 et 7 Rabat instituts, Rabat,
Morocco
b
ABSTRACT
Amphibian and reptile remains found in archaeological contexts are still poorly studied, especially in North
Africa. This article presents the first taphonomic analysis realised on amphibian and squamate remains
coming from a North-African quaternary site. The bones were not transported/sorted by water; they were
quickly buried and no significant perturbation occurred within deposits. The main origin of the amphibian
and squamate assemblages is predation, although some animals probably died in the cave from natural
causes. A comparison with taphonomic data from small mammals of the same cave gave more accurate
taphonomic and reliable palaeoecological interpretation of the site. This study also highlights the numerous
problems of interpretation linked to the lack of taphonomic referentials based on predator pellets/scats and
on weathering/burying experiments in North Africa. Copyright © 2011 John Wiley & Sons, Ltd.
Key words: Taphonomy; Amphibians; Squamates; Late Pleistocene; Holocene; Morocco
Introduction
Small vertebrates found in archaeological and palaeontological contexts can provide information not only
on past climates and landscapes but also the origin
and homogeneity of deposits through a taphonomic
analysis (Denys, 1985, 2002; Andrews, 1990). For the
Quaternary, studies on small mammal fossil assemblages (Rodentia, Erinaceomorpha, Soricomorpha,
Chiroptera) are numerous and are well distributed in
all geographical zones. On the contrary, amphibians
and reptiles are poorly studied in archaeological
* Correspondence to: Muséum National d’Histoire Naturelle, Département
de Préhistoire - UMR 7194, Bâtiment de Géologie-CP48, 43 rue Buffon,
75005 Paris, France. e-mail: [email protected]
Copyright © 2011 John Wiley & Sons, Ltd.
contexts, maybe because of their small size and the lack
of specialists, although they may be abundant and diversified in fossil accumulations (Rage, 2002). These
small animals are very dependent on their environment,
especially on the climatic conditions, for their thermic
regulation (reptiles) and on the presence of temporary
or permanent water pounds for respiration and
reproduction (amphibians). Thus, these taxa are accurate environmental indicators of the climate and landscape near the site and available freshwater (Bailon &
Rage, 1992; Rage, 2002).
Like for small mammals, a taphonomic approach has
to be adopted in order to determine the origin and the
eventual bias of faunal/skeletal representation of amphibian and reptile accumulations before the palaeoecological interpretation of the assemblages (Denys,
Received 18 May 2011
Accepted 11 July 2011
Taphonomic Study of Amphibian and Squamate Fossil Remains
1985, 2002; Andrews, 1990; Pinto Llona & Andrews,
1999). But, we must note the lack of taphonomic studies undertaken on these taxa, with only one detailed
and complete work on amphibians from Atapuerca in
Spain (Pinto Llona & Andrews, 1999) and some sparse
studies at several archaeological sites in various geographical zones (Bailon, 1997, 2005; Castillo et al.,
2001; Piper & O’Connor, 2001; Sampson, 2003;
Cochard, 2004; Arbogast et al., 2010). In addition,
few studies have been realised on amphibian and reptile
bone preservation in coprocoenoses (Pinto Llona &
Andrews, 1999). Rey and Sanchiz (2005) studied the
preservation of anuran bones in Barn owl pellets from
Spain. For North Africa, only two detailed taphonomic
studies have been realised specifically on fossil small
vertebrates (Stoetzel & Denys, in press): at Tighenif
(Algeria, Middle Pleistocene; Dauphin et al., 1994;
Denys et al., 1987) and at El Harhoura 2 (Morocco,
Late Pleistocene - Holocene; Stoetzel et al., 2011).
These studies have only considered small mammals,
especially rodents. Reference works on taphonomy
and palaeoecology for herpetofauna in archaeological
context as well as in modern predator assemblages
(owl pellets and mammalian carnivore scats) remain
very rare (Bailon, in press; Stoetzel & Denys, in press).
We present here the results of taphonomic analyses
of amphibian and squamate material from the El
Harhoura 2 cave and their contribution to palaeoecological and archaeological interpretations.
Context of study
The El Harhoura 2 cave is located in the region of
Témara, near Rabat (Figures 1, 2) and belongs to a
complex of several littoral caves which have probably
been dug by marine erosion into the local calcarenite
around the Middle-Late Pleistocene boundary (Texier
et al., 1985; Aberkan, 2008; Plaziat et al., 2008; Barton
et al., 2009). This region is of major interest to the
North-African prehistory, owing to the discovering of
several human remains in an Aterian context (Vallois
& Roche, 1958; Roche, 1969, 1976; Debénath, 1975,
1980, 2000; Roche & Texier, 1976; El Hajraoui,
2004; Nespoulet et al., 2008, 2009).
The El Harhoura 2 cave was discovered in 1977, and
after preliminary excavations in 1996, this site has been
excavated since 2001 using modern methods. The entrance faces west, towards the ocean and is around
300 m away from the current shoreline and 18.64 m
above sea level (ref. Nivellement Général du Maroc). Today,
the cave is fairly large (maximum length: 22 m,
617
maximum width: 9 m, maximum height: 8 m), with a
surface area of more than 25 m2.
Excavations are still occurring and have revealed 11
levels: Level 1 (Neolithic), Level 2 (Upper Palaeolithic,
Iberomaurusian) and Levels 3–11 (Middle Palaeolithic,
Aterian) (Figure 3). Only Levels 1–4 have been
subjected to extensive excavations (approximately
25 m2), underlying levels being known from a test pit
of around 4 m2 located at the entrance of the cave.
The geologic and stratigraphic context of the caves
of Témara is currently in revision, notably through
mineralogic and geochemical analyses (Boudad et al.,
2009, 2010). Preliminary results have shown the homogeneity of the deposits with abundance of an aeolian
sandy fraction, although several lithostratigraphical
levels can be identified. More detailed analyses are in
progress in order to interpret the chemical composition
of the sediments, a part of which could indicate faunistic activity (Boudad et al., 2009).
Radiometric datings are currently in progress at El
Harhoura 2, but results are already available for nearby
caves (Dar es Soltane 1 and 2, El Mnasra, Contrebandier;
Figure 1; Barton et al., 2009; Schwenninger et al., 2010).
These Optically Stimulated Luminescence datings have
revealed human occupation in this region since 125 ka
BP and have considerably decreased the lower age limit
of the Aterian culture with important implications for
understanding the Middle Palaeolithic in North Africa.
An important archaeological material was discovered
at El Harhoura 2, composed notably of human burials
and isolated remains, faunal remains, lithic and bone
industries, ceramics, pigments (hematite) and pearls
(in ostrich eggs and shells). The deposits of the El
Harhoura 2 cave have also yielded an exceptional richness in small terrestrial vertebrate remains (Rodentia,
Erinaceomorpha, Soricomorpha, Chiroptera, Amphibia,
Squamata, Chelonia) (Stoetzel et al., 2010). This particularity has allowed us to realise the first complete
taphonomic and palaeoecological study on small mammal remains at a North-African archaeological site
(Stoetzel, 2009; Stoetzel et al., 2007, 2010, 2011).
Material and methods
We present here the results of a taphonomic analysis
realised on the amphibian and squamate remains of El
Harhoura 2. The studied material comes from Levels 1
to 8 from the entrance of the cave (except Level 4b,
for which there was no sample available at the time of
this study): 152 buckets of sediments were sampled,
corresponding to a total volume of about 1.52 m3 of
sediments. The bones were then extracted by wet
618
E. Stoetzel et al.
Figure 1. Location of the region of Témara and of the main archaeological sites in the area.
Figure 2. Entrance of the El Harhoura 2 cave during excavations (photo E. Stoetzel).
619
Figure 3. Stratigraphy of the El Harhoura 2 cave (Nespoulet and El Hajraoui, 2007). Level 1: Neolithic; Level 2: Upper Palaeolithic (Iberomaurusian);
Levels 3–11: Middle Palaeolithic (Aterian).
screening using two superimposed sieves of 3-mm and
1-mm mesh. Sorting, identifications and taphonomic
analysis were made under a binocular microscope. A
previous taxonomic and taphonomic study on the herpetofauna from Level 1 has already been published
(Stoetzel et al., 2007, 2008); but at the occasion of
this work, we reviewed this material and the method
in order to homogenize the results all along the
stratigraphy.
The small vertebrates are largely dominated by small
mammals (more than 80%). Altogether, the studied
amphibian and squamate remains from Levels 1 to 8
of El Harhoura 2 represent 4414 elements belonging
to at least 17 species (Table 1; Figure 4; Stoetzel et al.,
2010; Bailon et al., 2011): six amphibians (Pleurodeles cf.
waltl, Bufo bufo, Bufo mauritanicus, Hyla meridionalis,
Discoglossus scovazzi, Pelobates cf. varaldii) and at least 11
squamates (Trogonophis wiegmanni, Ophisaurus koellikeri,
Gekkonidae cf. Tarentola, Lacertidae spp. including
Acanthodactylus sp., Eumeces algeriensis, Chalcides spp.,
Colubrinae indet., Coronella girondica, Malpolon monspessulanus, Natrix maura, Daboia mauritanica).
Taxonomic identifications were made through comparisons with keys found in literature (Klembara 1979,
1981; Rage, 1984; Szyndlar, 1984; Bailon, 1991,
1999, 2000; Ould Sabar & Michel, 1996; Barahona &
Barbadillon, 1997; Sanchiz, 1998; Bailon & Aouraghe,
2002; Caputo, 2004; Blain, 2005; Arnold et al., 2007)
and with modern specimens from Muséum National
d’Histoire Naturelle osteological collections and fresh
collections made by us in 2007 and housed now in
the Institut Scientifique of Rabat (Morocco). Species nomenclature follows the classifications of Bons and
Geniez (1996), Frost (2009) and Uetz and Hallermann
(2010).
Following several taphonomic studies (Andrews &
Evans, 1983; Denys, 1985; Denys et al., 1987, 1992,
1996, 1997; Andrews, 1990; Denys & Mahboubi,
1992; Fernandez-Jalvo et al., 1992, 1998; FernandezJalvo, 1996; Sanchez et al., 1997; Pinto Llona &
Andrews, 1999), we mainly studied skeletal representation and bone surface modifications (including digestion) but to a lesser extent, fragmentation. For saurians,
we also calculated two indices of skeletal representation
according to Andrews (1990) and Castillo et al. (2001):
Index1 [(femora + humeri)/(dentaries + maxillae)]*100;
Index2 [(tibiae + radii)/(femora +humeri)]*100.
Few taphonomic works on herpetofauna have been
realised, and they have been based on European Pleistocene material. Consequently, the predator referentials
are not necessarily adapted to North Africa. When possible, we made comparisons with material provening
from owl pellets from Morocco (Bubo ascalaphus, Tyto
alba) collected by C. Denys, E. Stoetzel and A. Rihane
(Faculty of Science, Mohammedia, Morocco); but amphibian and reptile remains are very rare in it. The elements most often taken into account for digestion in a
taphonomic study on small mammal remains are the
molars, incisors and femoral heads (Andrews, 1990).
Indeed, digestion is more visible on teeth and articular
E. Stoetzel et al.
620
Table 1. List of amphibian and squamate species from Levels 1 to 8 of El Harhoura 2 (NR = number of remains)
Level 1 Level 2 Level 3 Level 4a Level 5 Level 6 Level 7 Level 8
Species
Amphibia
NR
Urodela
Anura
Pleurodeles cf. waltl
Bufo bufo
Bufo mauritanicus
bufo sp
Hyla meridionalis
Discoglossus scovazzi
Pelobates cf. varaldii
Anura indet.
Squamata Sauria
Trogonophis wiegmanni
Ophisaurus koellikeri
Gekkonidae
Lacertidae
Scincidae
Sauria indet.
Serpentes Coronella girondica
Malpolon monspessulanus
Natrix maura
Colubrinae indet.
Daboia mauritanica
Serpentes indet
TOTAL
NR
1
2
38
26
5
8
44
64
1
9
16
94
35
7
53
2
43
3
158
609
12
4
NR
NR
4
6
7
15
9
3
2
4
6
12
3
1
4
2?
25
35
4
NR
5
9
17
25
4
NR
NR
1?
19
13
3
2
8
9
1
1
15
16
24
23
20
12
1
7
46
38
11
40
14
16
2
11
2
95
40
109
18
30
4
29
1
35
47
34
11
30
2
22
1
95
74
234
53
89
12
40
2
128
187
567
76
64
4
49
1
69
100
449
5
4
6
14
21
69
6
7
2
15
15
194
23
441
11
253
40
762
28
1257
6
714
11
184
zones than on other skeletal elements. But for amphibians, the proximal parts of long bones are cartilaginous
and are not preserved during fossilisation (Pinto Llona
& Andrews, 1999). In addition, teeth are rare in fossil
context because of their fragility, which limit direct
comparisons with small mammals. Thus, we chose to
study all amphibian skeletal elements in order to define
if specific elements are better adapted than the others
to this type of study. For squamates, we studied vertebrae, dentaries, maxillae and long bones. We also realised scanning electron microscope pictures (JEOL
JSM-840A) to better observe alterations in bone surfaces by using a secondary electron emission mode at
an accelerating voltage of 15 kV.
The palaeoecological inferences are mainly based on
the ecological data available in the literature (Bons &
Geniez, 1996; Le Berre, 1989; Schleich et al., 1996).
Results
Fragmentation
Even if some variations exist between the levels of El
Harhoura 2, we observed a very high degree of fragmentation on the amphibian and squamate remains all
along the stratigraphy. Intact bones are extremely rare,
and this could be due to fallen rocks, roots, trampling,
weathering, sediment compaction, as well as excavations and sieving. These phenomena have over-broken
NR
18
80
9
31
1
1
14
TOTAL
19
26
120
147
30
13
2
138
286
1
16
490
574
1531
190
293
28
215
3
292
4414
the material, so it is not possible to assess an eventual
original predator-induced breakage pattern. In addition,
amphibian (and some saurian) bones are more fragile
than small mammal ones, notably because they are
more hollow and thinner, which increase their fragmentation and decrease their conservation potential. So, we
decided here to not study in a detailed way the fragmentation of the amphibian and squamate elements, as
it was the case for small mammals (Stoetzel et al.,
2011). However, we observed that Eumeces elements
and snake vertebrae (especially Malpolon) are generally
better preserved, thanks to their robustness and compactness. In addition, we often observed a ‘breakage
pattern’ for the vertebrae. It begins with a lateral cracking all around the vertebrae (on both left and right lateral faces) until the separation of the neural arch and
the ventral parts (centra). All apophyses are frequently
broken. We also observed a better preservation of
bones at the deepest levels (6, 7, 8).
Digestion
We can see in Table 2 and Figure 4 that, for amphibians, the percentages of digestion (PD) are relatively
low (3.3%–23.1%), which correspond in all levels to
a predator category 1–2 (Pinto Llona & Andrews,
1999). The maximum PD is observed in Level 6 and
the lower one in Level 2. In addition, the grade of digestion is low; only Levels 1, 3, 5 and 6 show moderate
digestion on few bones. Concerning squamates, the
621
Figure 4. Representation of the percentage of amphibian and squamate remains at El Harhoura 2 affected by different grades of digestion.
proportion of digested remains is higher than for
amphibians (24.5%–37.7%). The grades of digestion
are also more important, with high digested elements
in all levels (Table 2, Figure 4). For the total material
attributed to squamates, the maximum PD is observed
in Level 3 and the minimum in Level 1. Snakes and
lizards present similar results, but for amphisbaenians,
the maximum PD is observed in Level 4a. In this group,
digestion is also important in Levels 2, 3 and 6, and the
PD is lower in Levels 1, 7 and 8. For amphibians, as
well as for squamates, there is no relation between
number of remains and PD. This means that the levels
with the most abundant remains are not necessarily the
levels with the highest PD.
Traces of digestion on amphibian and squamate
bones of El Harhoura 2 are similar to those observed
on small vertebrate remains from other sites (among
which Andrews, 1990; Fernandez-Jalvo & Andrews,
1992; Pinto Llona & Andrews, 1999): splitting, flaking
(rare in our material), polishing and dissolution by
digestive acids, thinning of cortical bone inducing
rounding of broken areas and emergence of cancellous
bone (Figure 5).
For amphibians, we observed digestion particularly
on broken diaphyses, condyles of vertebrae, tuberosities of ilia, metapodials, humeral condyles and articular
surface of radio-ulnae (Figure 5a,b,c,d). For squamates,
digestion is well visible on the articular surface, notably
on the condyle and paradiapophysis of snake vertebrae
(Figure 5i). Often, the parapophyseal processes are
digested before the condyle, sometimes until total dissolution. But for amphisbaenian vertebrae, we often
observed higher digestion of the ventral face than of
the articular parts, with an enlargement of ventral foramens and the apparition of holes. On saurian vertebrae,
we frequently observed digestion not only on the articular zones (condyle, synapophyses) but also the
facets of post-zygapophyses and prezygapophyses
and the ventral surface of centra (Figure 5h). For gekkos, which vertebrae are amphicoelous, we did not
E. Stoetzel et al.
622
Table 2. Percentages according to grades of digestion of amphibian and squamate remains from Levels 1 to 8 of El Harhoura 2
Percentage of digestion (PD, %)
Amphibians
No digestion
Low digestion
Moderate degestion
High digestion
Total PD
Squamates
No digestion
Low digestion
Moderate digestion
High digestion
Total PD
Total PD
Level 1
Level 2
Level 3
Level 4a
Level 5
Level 6
Level 7
87.1
8.1
4.8
0
12.9
96.7
3.3
0
0
3.3
95.5
3.0
1.5
0
4.5
91.5
8.5
0
0
8.5
91.1
6.3
2.5
0
8.9
76.9
21.8
1.3
0
23.1
83.7
16.3
0
0
16.3
84.0
16.0
0
0
16.0
75.2
15.5
5.8
3.2
24.5
20.9
63.0
19.7
14.2
2.4
36.2
29.9
62.3
19.9
11.2
6.5
37.7
32.0
67.6
21.4
7.7
3.3
32.4
27.5
68.8
19.0
8.9
3.3
31.2
28.5
64.2
19.8
11.6
4.4
35.8
35.0
64.0
18.7
12.8
4.4
36
34.7
72.2
15.8
9.0
3.0
27.8
25.9
observe digestion on the condyle. It was possible on
the cotyle outlines, but it was difficult to define at
which degree of digestion it corresponded. For lizards,
it was also possible to study the digestion on dentaries,
maxillae, teeth and long bones. We generally observed
thinning of the anterior part of the dentaries, and the
teeth become matt and spotted, the top become thinner and digestion often cracks and breaks the teeth
(Figure 5e,f,g).
Other surface modifications
Figure 6 shows the percentage of amphibian and reptile
remains affected by surface modifications other than digestion. The same bone can present several types of
traces, that is why percentages go over 100%. Root
marks and black traces (probably because by manganese oxides) were always the most abundant, both for
amphibians (35.9%–76.7% for root marks; 26.6%–
93.6% for black traces) and squamates (16.6%–80.8%
for root marks; 37.8%–98.8% for black traces). They
can be very ponctual and localised or cover the whole
surface of the bone. Level 1 always presents a lower
proportion of bones affected by black traces. There
could be two main reasons to this observation: first,
black traces are less numerous, and second, coating
by black sediment can hide them and then they may
be underestimated. Bones coated by sediments are in
all cases more numerous in Level 1 (12.1% for amphibians and 15.1% for squamates), but they are also
present in other levels, notably Levels 2 and 4a. In
Level 1, one amphibian bone is well rounded, but this
is the only one in the whole material, and the attribution to water action is doubtful. Trampling traces are
rare (0%–5.6%; Figure 7c,d). On the contrary, traces
of corrosion are present in all levels (4.3%–18.6%;
Figure 7e,f) and are probably bevause of an attack by
Level 8
acidic sediments. Concerning crackings and desquamations attributed to weathering (Figure 7a,b), they are
more or less abundant all along the stratigraphy
(2.3%–25.5%) but always with a low intensity, which
indicates quick burying. Burnt bones are more abundant in Level 1 (up to 9%), which is an ashen layer
and were probably accidentally burnt (Stoetzel et al.,
2011). We observed that burnt bones are generally
weakened and more easily fragmented and splitted.
No tooth marks were observed on our material.
Because of the superimposition of several taphonomic
processes and the lack of taphonomic referentials, it is
sometimes difficult to distinguish between them. Confusion can occur between splitting because of digestion
and weathering or compaction and between corrosion
and digestion. However, corrosion can generally be
differentiated from digestion by a pitted surface, which
is less smooth and less polished (Andrews, 1990). In
addition, we observed corrosion often associated
with ‘black traces’, around which there can be a ‘halo’
of alteration with a local decoloration spot and fragilisation of the bone, which differs from digestion.
In Level 1, we observed unidentified traces on an
amphibian radio-ulna (Figure 7g,h), too marked to be
attributed to trampling and different than tooth marks.
Are they anthropic cut marks? Further analyses have to
be realised to answer this question.
Skeletal representation
Tables 3 and 4 and Figure 8 present the percentage of
skeletal representation (PR) of the main amphibian and
saurian remains. We didn’t consider snakes or amphisbaenians, almost exclusively represented by vertebrae.
All the Voorhies categories of skeletal elements based
on bone-sorting by water transportation are represented
(Voorhies, 1969; Dodson, 1973; Behrensmeyer, 1975;
623
Figure 5. Examples of digested elements from El Harhoura 2: a-b = amphibian tarse (with root marks on the right); c-d = amphibian radio-ulna;
e-g = Lacertidae dentary; h = saurian vertebra; i = snake vertebra. Scale = 1 mm.
Korth, 1979; Denys, 1985), except amphibian maxillae
(cat. I) and mandibles (cat. V). There are differences in
the percentages of representation between the levels,
and we observe a general loss of small and/or fragile elements such as radii, ribs, phalanges and metapodials.
This loss is more probably due to the mesh size used
to sieve the sediments, the difficulty in recognising
them during sorting, or a lower resistance to fossilisation, than sorting by water transport.
For amphibians (Figure 8), we observe a low representation of cranial elements (mainly represented by
sphenethmoids), ischia, scapular girdle and extremities
(generally 0%–20%). On the contrary, long bones
such as urostyles, humeri, tibio-fibulae and radio-ulnae
624
E. Stoetzel et al.
Figure 6. Post-predation modifications on the bone surface of amphibian and reptile remains from Levels 1 to 8 of El Harhoura 2.
are well represented (generally 30%–100%). We observe differences between levels:
• Level 1: the maximum PR is obtained for tibio-fibulae
and then for radio-ulnae, ilia, humeri and urostyles.
Femora are low represented.
• Level 2: the profile is quite different from that of
Level 1. Radio-ulnae are the most represented, followed by tibio-fibulae and urostyles. Femora, ilia
and humeri are low represented.
• Level 3: urostyles present the highest PR, just before
tibio-fibulae and ilia and then humeri and radioulnae. Femora and scapular girdle are better represented than in the two previous levels.
• Level 4a: tibio-fibulae, urostyles and humeri are all
the most represented elements in this level. Radioulnae, femora and ilia present also relatively high PR.
• Level 5: the profile is close to that of Level 4a but
with a higher representation of humeri and scapular
girdle and a lower representation of urostyles.
• Level 6: urostyles, femora, ilia and vertebrae are
better represented than in Level 5, contrary to
scapular girdle.
• Level 7: the maximum PR is obtained here for radioulnae, followed by femora, tibio-fibulae and humeri.
Scapular and pelvian girdle and vertebrae are also
relatively well represented.
• Level 8: the better represented elements are tibiofibulae and radio-ulnae, after ilia, urostyles, humeri
and vertebrae.
For saurians, profiles of skeletal representation are
very similar (Figure 8). The better represented elements
are always dentaries, whereas radii, scapulae, ribs and
625
Figure 7. Examples of post-predation modifications on the amphibian and squamate remains of El Harhoura 2: a-b = weathering and root mark (hole)
on an amphibian tibio-fibula; c-d = striations interpreted as trampling on an amphibian ilion; e-f = corrosion on a snake vertebra; g-h = unidentified
striations on a toad radio-ulna from Level 1. Scale = 1 mm.
extremities present the lower PR (0%–6.7%). However, there are some differences between the levels:
• Levels 1 and 8 are very similar; maxillae, femora and
tibiae are well represented contrary to the other
levels, with also a pic for pelves and vertebrae.
• Level 2 shows a very low representation for tibiae
but a higher one for pelves.
• In Level 3, tibiae and pelves are relatively well represented but less than femora and humeri.
• Levels 4a, 5, 6 and 7 present pics for femora, pelves
and humeri and a very low representation of tibiae.
E. Stoetzel et al.
626
Table 3. Number of skeletal elements (N) and their percentage of representation (PR, %) for the amphibian remains from Levels 1 to 8
of El Harhoura 2
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
Level 7
Level 8
Skeletal elements
Amphibians
N
PR
N
PR
N
PR
N
PR
N
PR
N
PR
N
PR
N
PR
Cranial elements (Cr)
Femora (Fem)
Tibio-fibulae (TF)
Ilia (Il)
Ischia (Isch)
Urostyles (Uro)
Humeri (Hum)
Radio-ulnae(RU)
Scapulae (Scap)
Suprascapulae (SScap)
Clavicles (Clav)
Coracoids (Cor)
Vertebrae (Vert)
Phal. + Metap. (PM)
3
2
22
13
1
4
10
15
4
1
1
1
25
26
1.2
9.1
100.0
59.1
4.5
36.4
45.5
68.2
18.2
4.5
4.5
4.5
25.3
2.7
0
0
2
1
0
1
1
6
0
0
0
1
3
16
0.0
0.0
33.3
16.7
0.0
33.3
16.7
100.0
0.0
0.0
0.0
16.7
11.1
6.1
1
3
7
7
0
4
6
6
2
0
0
2
9
21
1,1
37,5
87,5
87,5
0,0
100,0
75,0
75,0
25,0
0,0
0,0
25,0
25,0
6,0
0
2
8
2
0
4
8
4
1
0
0
0
5
14
0.0
25.0
100.0
25.0
0.0
100.0
100.0
50.0
12.5
0.0
0.0
0.0
13.9
4.0
2
3
12
4
0
1
15
10
4
0
0
4
16
7
1.2
20.0
80.0
26.7
0.0
13.3
100.0
66.7
26.7
0.0
0.0
26.7
23.7
101
0
5
9
6
0
2
12
8
2
0
0
0
25
9
0.0
41.7
75.0
50.0
0.0
33.3
100.0
66.7
16.7
0.0
0.0
0.0
46.3
107
0
4
4
1
1
1
4
5
3
0
0
1
10
9
0.0
80.0
80.0
20.0
20.0
40.0
80.0
100.0
60.0
0.0
0.0
20.0
44.4
401
1
1
3
2
0
1
2
3
1
0
0
0
9
1
3.0
33.3
100.0
66.7
0.0
66.7
66.7
100.0
33.3
0.0
0.0
0.0
66.7
0.8
MNI
N Total
Mean PR
11
128
3
31
4
68
27.4
4
48
15.6
8
78
43.4
6
78
28.7
3
43
27.5
28.8
2
24
36.6
40.3
PR = (FO/(FTxMNI))x100 (FO = Observed frequency, FT = Theoretical frequency of each element).
The minimum number of individuals (MNI) was calculated from the most abundant skeletal element, and PR was calculated according
to Dodson and Wexlar (1979).
Table 4. Number of skeletal elements (N) and their percentage of representation (PR, %) for the saurian remains from Levels 1 to 8 of El
Harhoura 2
Level 1
Level 2
Level 3
Level 4a
Skeletal elements
Saurians
N
Cranial elements (Cr)
Dentaries (Dent)
Maxillae (Mx)
Femora (Fem)
Tibiae (Tib)
Pelves (Pel)
Humeri (Hum)
Radii (Rad)
Scapulae (Scap)
Ribs (Ri)
Vertebrae (Vert)
Phal. + Metap. (PM)
14
8.1 4
2.1 16
3.0
3
23 100.0 25 100.0 71 100.0 43
12 52.2 8 32.0 20 28.2
8
9 39.1 5 20.0 38 53.5 21
6 26.1 0
0.0 12 16.9
2
9 39.1 16 64.0 14 19.7
9
3 13.0 4 16.0 31 43.7 10
0
0.0 0
0.0 0
0.0
0
0
0.0 0
0.0 0
0.0
0
17
6.7 0
0.0 1
0.1
1
60 10.4 27
4.3 41
2.3 20
3
0.0 0
0.0 2
0.1
0
MNI
N Total
Mean PR
((Fem + Hum)/(Dent + Mx))x100
((Tib + Rad)/(Fem + Hum))x100
PR
12
153
N
13
89
16.9
34.3
50.0
PR
N
36
246
12.1
27.3
/
PR
N
N
43
403
10.8
60.8
6.5
PR
Level 6
N
PR
Level 7
N
PR
Level 8
N
PR
0.9
16
2.5 36
3.1 11
1.5 2
1.6
100.0
86 100.0 156 100.0 97 100.0 17 100.0
18.6
18 20.9 45 28.8 31 32.0 8 47.1
48.8
49 57.0 67 42.9 44 45.4 6 35.3
4.7
5
5.8
9
5.8
6
6.2 3 17.6
20.9
41 47.7 49 31.4 29 29.9 8 47.1
23.3
29 33.7 31 19.9 12 12.4 3 17.6
0.0
2
2.3
0
0.0
7
7.2 0
0.0
0.0
1
1.2
0
0.0
0
0.0 0
0.0
0.2
9
1.0 16
0.9
3
0.3 3
1.6
1.9 145
6.7 454 11.6 379 15.6 53 12.5
0.0
2
0.1 15
0.2
0
0.0 1
0.1
22
117
13.8
75.8
17.4
PR
Level 5
78
878
14.2
75.0
9.0
49
619
12.8
48.8
9.2
9
104
12.5
43.8
23.2
13.9
36.0
33.3
PR = (FO/(FTxMNI))x100 (FO = Observed frequency, FT = Theoretical frequency of each element).
The minimum number of individuals (MNI) was calculated from the most abundant skeletal element, and PR was calculated according
to Dodson and Wexlar (1979).
Origin of amphibians and squamates of
El Harhoura 2
According to the Voorhies categories and the absence
of rounding, it seems that no water transportation had
occurred. In addition, some snake vertebrae were found
in anatomic connection, which could occur in owl pellets or when animals die in place and argue against the
perturbation in the accumulation. We are thus in presence of in situ accumulations without significant secondary perturbations. But what is the origin of these
accumulations? It is known that amphibians and
627
Figure 8. Profiles of percentages of representation of the amphibian and saurian remains from Levels 1 to 8 of El Harhoura 2.
reptiles can often live near or in caves in order to find a
more temperate and wet environment or to frequent
the crevices of the rock. However, numerous traces of
digestion were observed on the amphibians and squamate remains; thus, predation was probably the main
cause of accumulation at El Harhoura 2.
We have analysed digestion in a previous study on
amphibian and reptile remains from Level 1 of El
Harhoura 2 (Stoetzel et al., 2008). Since then, after having studied the whole material of El Harhoura 2 and
analysed owl pellets, we reviewed the digestion grades
and made some rectifications. For amphibians, in spite
of a PD similar to that observed in the previous study
on Level 1 (around 13%), no high digestion was finally
observed on our material (only low and moderate
grades). Another modification concerns saurian remains
from Level 1, which actually present digestion. We see
here the necessity to better characterise the grades of
digestion on amphibian and reptile bones, with photos
and drawings of each grade, as it was undertaken for
small mammals (Fernandez-Jalvo & Andrews, 1992;
Stoetzel, 2009; Stoetzel et al., 2011).
Concerning the potential predator(s) at the origin of
the accumulations, several studies were made on the
diet and the faunistic composition of scats and pellets
of North-African predators (mainly T. alba, B. ascalaphus,
Asio capensis, Falco tinnunculus, Genetta genetta). According
to these studies and our observations, owls and diurnal
raptors eat preferentially insects and small mammals,
but they also hunt occasionally snakes, lizards
(Gekkonidae, Lacertidae, small Scincidae, sometimes
Chameleons) and several amphibians such as Discoglossus,
Rana, Hyla, Pleurodeles, Pelobates, B. bufo and B. mauritanicus
(see for example Saint Girons et al., 1974; Boukhemza,
1989; Delibes et al., 1989; Bergier & Thévenot, 1991;
Hamdine et al., 1993; Aulagnier et al., 1999; Baziz
et al., 1999, 2001a, 2001b; Thévenot, 2006; Rihane,
2003, 2005; Souttou et al., 2007, 2008; Sekour et al.,
2010, 2011).
Based on other works on digestion of amphibian
remains (Pinto Llona & Andrews, 1999), the accumulator correspond in all levels to a predator category 1–2.
It was unlikely to be the Barn owl (T. alba) because it
produces minimal alterations on prey bones (Andrews,
E. Stoetzel et al.
628
1990; Pinto Llona & Andrews, 1999), while we
obtained higher rates of digestion. It was more probably another owl of medium size known to have an
eclectic diet, such as B. ascalaphus, which is supposed
to have a stronger digestion intensity like other Eagle
owls. However, if some literature data indicate that B.
ascalaphus eats amphibians and reptiles in its diet (Saint
Girons et al., 1974; Vein & Thévenot, 1978; Thévenot,
2006; Sekour et al., 2010), it is always in low proportions, and we cannot yet infer with precision whether
the predators were responsible for such accumulations.
As squamate remains present a higher digestion than
the amphibian ones, there exists the possibility of the
intervention of several types of predators, notably for
Levels 2, 3, 6 and 7 for which we observed a higher digestion of squamate bones. However, we must keep in
mind that amphibians are much less abundant than
squamates, thus the sample size could be too small to
have statistically valid results for amphibians, and the
observed digestion pattern may not be representative.
This could be due to differential conservation and fossilisation (squamate bones are more resistant than amphibian ones) and also due to the skeletal representation in
living animals. For instance, anurans have much less vertebrae (9) than squamates, especially snakes (which
could have several hundreds of vertebrae). It is also possible that the difference in digestion between amphibians
and squamates is because of different lifestyles of the animals concerned. Many of the amphibian remains could
have come from animals that were not predated but died
in the cave from natural causes (during estivation), and
this could account for their lower levels of digestion as
compared with squamates.
Concerning the prey species, studies on owl pellets
show that larger species such as Bufo and Eumeces are
more rarely hunted, or the animals are skinned and
their bones are not always ingested by predators. But
at El Harhoura 2, all the taxa presented traces of digestion and were thus hunted and ingested. We chose here
to make a global study on our material, just by separating amphibians and reptiles. However, we are aware of
the necessity to undertake, in the future, very detailed
studies to consider every family separately, species by
species and level by level. Thus, it will be possible to
see if all species present digestion and maybe highlight
different patterns of accumulation by taxon.
In each group, the differences in the skeletal representation along the stratigraphy could be due to the
origin of the accumulations (‘natural’, predation, or
both of them), the action of several predators, or the
differential preservation and fossilisation of bones
according to different species. It is thus important to
develop referentials, experiments and comparisons.
Comparisons with other studies
Amphibians
We compared our results with those coming from
other archaeological sites: Dolina (Spain; Pinto Llona
& Andrews, 1999), Val-De-Reuil (France, Arbogast
et al., 2010), Chalain 3 (France; Bailon, 1997), and
Chassey (France; Bailon, 2005). We also considered data
from T. alba pellets from Spain (Rey & Sanchiz, 2005).
No real correlation could be made between the profiles
of skeletal representation of El Harhoura 2 and those of
the other sites, even if we globally observed a better representation of long bones, probably because of differential conservation. The amphibian material from the two
french sites Chalain 3 and Chassey is dominated by Rana
temporaria, which was probably eaten by humans. As a
result, the profiles of skeletal representation show
clearly a better representation of posterior parts. Similar
results were observed by other authors such as Chiquet
(2005) and Kyselý (2008). According to Arbogast et al.
(2010), at Val-De-Reuil, Bufo and Rana remains were
probably accumulated by nonanthropic agents. There
is a better representation of ilia and femora and a lower
representation of tibio-fibulae than at El Harhoura 2. In
addition, PR of some levels of El Harhoura 2 are close
to those obtained for Discoglossus and Rana remains by
Rey and Sanchiz (2005) for T. alba pellets (notably
with good preservation of tibio-fibulae); but grades of
digestion do not correspond to this predator.
At Dolina (Pinto Llona & Andrews, 1999), the percentage of digestion is higher than at El Harhoura 2
(36%–38% at TD4 vs 3.3%–23.1% at El Harhoura
2). The authors concluded an accumulation by a mammalian carnivore, confirmed by a high fragmentation.
At Val-De-Reuil (Arbogast et al., 2010), 50% of the amphibian remains are digested and more than 70% of the
bones are fragmented, corresponding to a mammalian
carnivore of middle or large size or to a diurnal raptor.
On the contrary, at Chassey (Bailon, 2005), no or few
dubious traces of digestion were observed while fragmentation is very high (74%–80%), arguing for an anthropic accumulation with mastication but without
ingestion of bones. Pinto Llona and Andrews (1999),
Piper and O’Connor (2001) and Arbogast et al. (2010)
had already noticed that on amphibian bones, protruding edges and fragmented and articular surfaces are
most prone to abrasion (digestion, corrosion), and we
found similar results.
Post-predation modifications have been only studied
by Pinto Llona and Andrews (1999). At Dolina, no
weathering traces were observed on amphibian bones,
indicating no exposition to open air and quick burying.
In addition, abrasion resulting from slight water transport or sediment motion within a general context of
low energy was found at Dolina, while no such evidences were found at El Harhoura 2.
Squamates
Other taphonomic studies such as Arbogast et al. (2010;
Val-De-Reuil, France) and Castillo et al. (2001; La Cueva
del Llano, Canary Islands) have considered squamate
remains.
In comparison with Castillo et al. (2001), some similarities with the skeletal representation of El Harhoura
2 are observed, notably a good representation of dentaries, maxillae, humeri, femora and pelves. At ValDe-Reuil, Arbogast et al. (2010) noticed that reptile
assemblages are mainly composed of vertebrae, often
found in anatomic connection.
Concerning cranial and post-cranial proportions, index
2 (cf. Material and methods) is in mean similar at La Cueva
(22–49.5) and at El Harhoura 2 (6.5–50), indicating a
loss of distal long bones compared with proximal ones.
But, the range of index 1 is quite different at the two
sites: 68.3–129.9 at La Cueva and 27.3–75.8 at El
Harhoura 2, indicating a better representation of cranial elements at El Harhoura 2 than at La Cueva. As
for amphibians, there is probably a differential conservation phenomenon which has to be defined more precisely for reptiles in this particular geographical region.
At Val-De-Reuil, Arbogast et al. (2010) noticed that
15% of the reptile remains are digested, against
20.9%–35% at El Harhoura 2. In both cases, the fragmentation is very high. As for amphibians, the authors
attributed these alterations to a small or medium mammalian carnivore despite the low percentage of digestion. At La Cueva, Castillo et al. (2001) observed no
evidence of digestion on reptile bones and attributed
the small vertebrate accumulations to T. alba on the
basis of a low digestion on small mammal remains.
Arbogast et al. (2010) noticed that digestion is more observable on prezygapophyseal processes, synapophyses, neural spine and neural arch of reptile
vertebrae. This is a little different from the observation
that we made at El Harhoura 2 (see Results: Digestion),
but the prezygapophyseal processes on the snake vertebrae are frequently broken in our material.
Comparison with small mammals of El
Harhoura 2 and contribution to the
taphonomic history of the cave
For small mammals (Stoetzel et al., 2011) as well as for
amphibians and squamates, polishing/rounding by
629
water is absent and all the Voorhies categories are
represented, suggesting that no transport and sorting
by water occurred.
The accumulations of amphibian and squamate
remains at El Harhoura 2 correspond to ‘natural accumulations’ (animals living near or in the cave) and
mostly to coprocoenosis (probably by an owl such as
B. ascalaphus), according to the numerous traces of digestion. Squamates and small mammals present similar
trends in the evolution of the PD along the stratigraphy (low PD in Levels 1 and 8, high PD in Levels 3
and 6), except for Levels 2 and 7 which present a
higher digestion of squamate bones than of small mammal ones (Figure 4). For amphibians, the only common
trend with small mammals is a maximum of digestion in
Level 6. Generally, at El Harhoura 2, we observed that
amphibian remains are less digested than squamate and
small mammal ones (Stoetzel et al., 2011). According to
Pinto Llona and Andrews (1999) criteria, the potential
predators at the origin of the amphibian accumulations
belong to category 1–2 of digestion in all levels,
whereas for small mammals, we concluded higher categories predators (2–4).
This could have several explications. First, for small
mammals, we selected bones on which digestion is
more easily observable (teeth and femoral heads),
whereas for amphibians, we took into account all skeletal elements. In addition, for amphibians, there are less
elements on which digestion could be observed, because epiphyses are absent and teeth are extremely rare
(or unusable) in fossil assemblages. We also must keep
in mind that amphibian bones are very fragile and
probably more sensitive to taphonomic processes.
They should be less resistant to high digestion (high
dissolution and fragmentation) and fossilisation. Thus,
the most fragile and digested elements are probably
under-represented in the fossil assemblage. But, it could
also be possible that several predators occurred and ate
different amphibians, squamates and small mammals.
Finally, a part of amphibians could have come itself in
the cave, without being hunted and accumulated by
predators. Indeed, amphibians frequently enter in caves
to find a more temperate and wet environment, especially to estivate or hibernate (mainly Bufonidae), as
could be the case for several reptiles, which often frequent the rock faces of the cave. We also noticed that
contrary to small mammals for which digestion is well
observable on femoral heads, digestion on saurian long
bones here indicate rarely an attack on the articular
parts but rather edges and anterior/posterior faces of
the proximal parts.
For the small mammals of El Harhoura 2 (Stoetzel
et al., 2011), we concluded an accumulation by an owl
630
(B. ascalaphus?) in Levels 1, 7 and 8 and by a small mammalian carnivore (Fox? Genet?) or a diurnal raptor
(Falco tinnunculus?) in Levels 3 and 6. Levels 2, 4a and
5 present intermediate signals (unknown predator? mixing of several predators?). All these potential predators
are generalists and add frequently amphibians and reptiles to small mammals and birds in their diet. As squamate remains are more digested than small mammals in
Levels 2 and 7, it is possible that they were accumulated
by a small carnivore or a diurnal raptor rather than by an
owl in these levels. No traces attributable to anthropic
cut marks were observed on the small mammal bones.
Concerning post-predation processes, amphibian,
squamate and small mammal data present similar
results: high breakage, numerous root marks, ‘black
traces’, low trampling and weathering, frequent corrosion by soil and rare burning. These observations confirm the relatively quick burying and low perturbations
of the deposits except by the growth of plant roots and
burrows (insects, rodents) localised during excavations
(but without observation of insect or rodent marks on
small vertebrate bones). In addition, the weathering
stages are similar for small mammals and herpetofauna,
indicating that they were probably accumulated at the
same time by similar agents.
We made a preliminary study on the small mammal
remains concerning a potential relationship between
the quantity of root marks and the density of the vegetation cover (Stoetzel et al., 2011). We found that
Levels 1–4 have high percentages of bones with root
marks as compared with Levels 5–7. We found similar
results for amphibians and squamates, despite the fact
that Level 8 shows a significant increase in small mammal bones with root marks. The vegetation cover could
be the major parameter to explain this observation, and
in this case, in older levels (except Level 8?), the landscape was more open with a lower vegetation cover
than in upper levels. But it could be also interpreted
in relation with the evolution of the cave entrance
morphology during the time, by the progressive erosion (destruction) of the roof. This reduction process
of the natural overhang allowed the plant development
inside the cave, even if the climate does not change.
This could explain the fact that quantity of root marks
is not necessary linked with the palaeoecological
evolution.
Castillo et al. (2001) have already shown that lizards
present a higher loss of distal bones as compared
with small mammals. For amphibians, Bailon (1997),
Sampson (2003) and Arbogast et al. (2010) highlighted
a differential fragmentation and conservation of skeletal
elements, probably because of osteological particularities.
It is necessary to develop comparative studies concerning
E. Stoetzel et al.
differential representation and conservation within
amphibians, squamates and small mammals through the
study of owl pellets and other fossil sites. Indeed, amphibians and reptiles are poorly studied, and when they are
recorded, they are often not determined at a specific or
even generic level.
Palaeoecological and archaeological
implications
At El Harhoura 2, amphibians and reptiles display the
same post-depositional taphonomic pattern and could
have been accumulated simultaneously in some levels
by the same predators (Level 6: small mammalian carnivore or diurnal raptor?). For other levels, they may have
had different sources and consequently the palaeoecological information provided by both the taxa may be
either complementary or in contradiction. The lack of
taphonomic referentials makes the characterisation of
taphonomic bias difficult. We, however, decided to
compare the palaeoecological signals given by amphibians, squamates and small mammals, because although
the origin of the assemblages can be ‘natural’ or by predation, there was no secondary transport. So, the local
palaeoecological signal given by the present species
is still ‘valid’, although we cannot really interpret the
absence of other species nor use a quantitative index
for reconstructions.
The palaeoecological study based on small mammals
(Stoetzel et al., 2011) revealed an alternation of arid
(Levels 5 and 7) and relatively humid periods (Levels
3, 4a, 6, 8) during the Late Pleistocene, ending with a
humid phase during the Middle Holocene (Level 1).
Results based on the ecology and relative abundance
of amphibian and squamate taxa corroborate these conclusions (Stoetzel, 2009; Stoetzel et al., 2008, 2010). In
addition, they underlined the aridification of the climate in Level 2, not recorded by small mammals but
previously shown by large mammals (Michel et al.,
2009). The humid periods were characterised by the
development of water pounds tree-lined in the vicinity
of the cave. On the contrary, when the climate was
drier, the number and/or the surface of water sources
were reduced and aquatic species were less numerous.
However, neither small mammals nor herpetofauna
were accumulated by water transport in the cave.
No cut marks or specific burning patterns indicating
human consumption were observed on the small mammal and squamate remains at El Harhoura 2. We only
found one amphibian radio-ulna with traces looking
like anthropic cut marks (Figure 7g,h). Amphibian consumption has been shown in several archaeological
sites from different geographical regions, mainly for the
Mesolithic or Neolithic periods (Cooke, 1989; Bailon,
1993, 1997, 2005; Bailon & Rage, 1992; Chiquet,
2005; Kyselý, 2008). Toad consumption by humans
at El Harhoura 2 during the Holocene is coherent with
an enlargement of their diet in this period (birds, marine resources; Campmas et al., 2008, 2010). But only
one amphibian bone displays this kind of trace,
whereas generalised consumption of toads would have
shown a clear over-representation (or even an exclusive
representation) of posterior parts (ilia, urostyles, femora, tibio-fibulae); it is not the case at El Harhoura 2.
Thus, if the Neolithics consumed amphibians at El
Harhoura 2, it seems that it was only a very limited
practise. In addition, muscles on frog limbs leave easily
after cooking and it is generally possible to eat directly
above without tools. Thus, there are generally more
often burning traces at the extremities of the long
bones and chewing marks than cut marks. But, here,
this is a radio-ulna, and arms are maybe less easy to
eat than thighs, inducing the use of tools. Experiment
works have to be realised to verify this hypothesis.
Conclusion
A combination of studies on mammals and herpetofauna allows us to have cross validations and a more reliable taphonomic and palaeoecological interpretation
of the sites occupied by Moroccan human populations
during the Quaternary. Even if each group seems to
present taphonomic particularities (differential representation and conservation), a lot of similarities have
been revealed between the data resulting from small
mammals, amphibians and squamates of El Harhoura
2: a relative permanency in post-depositional phenomenon, no transport/sorting by water, quick burying
and few deposits perturbations. The main origin of the
small vertebrate accumulations is predation, probably
by several types of predators. But, without fossil and
modern taphonomic referentials, notably for amphibians, reptiles and North-African rodents, it is difficult
to determine precisely the accumulator or the taphonomic bias induced by predation. A part of amphibians,
lizards and snakes also probably came itself in the cave,
perhaps in order to find a more temperate habitat during
hot and dry periods. Despite this lack of referentials,
amphibians and reptiles can bring interesting palaeoecological information. But, it appears necessary to realise taphonomic referentials based on the study of owl
pellets and mammalian scats, as well as on weathering
and burying experiments, in order to better characterise
the effects of several taphonomic agents on amphibian
631
and squamate bones and to enhance the taphonomic
and palaeoecological interpretations of North-African
fossil assemblages.
Acknowledgments
The studied paleontological material was sampled during
excavations of the archaeological mission El HarhouraTémara, under the administrative supervision of the
Institut National des Sciences de l’Archéologie et du Patrimoine
(Rabat, Morocco). A great thanks to the researchers
and technicians of the Institut Scientifique (Rabat) for their
help for small vertebrate trapping and osteological preparations. We thank Abdeslame Rihane (Mohammedia)
for his help in T. alba pellets collection. We also thank
Emilie Campmas for her comments, Céline Houssin for
her help for the scan microscope photographs, and
Maxime Cammas who made the map. We finally thank
the reviewers for their corrections and comments.
This work was realised thanks to doctoral grants from
Region Ile-de-France and financial support of the Project
ANR-09-PEXT-004 ‘MOHMIE’ (coord. C. Denys). This
paper was presented in the New Perspectives in
Taphonomy session within the 11th ICAZ meeting in Paris.
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