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New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the Argana Basin, western High Atlas, Morocco – Ichnotaxonomic implications
New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the Argana Basin, western High Atlas, Morocco — Ichnotaxonomic implications Abdelouahed Lagnaoui, Hendrik Klein, Hafid Saber, Abdelilah Fekkak, Abouchoua¨ıb Belahmira, Joerg.W. Schneider PII: DOI: Reference:
S0031-0182(16)30035-9 doi: 10.1016/j.palaeo.2016.03.022 PALAEO 7755
To appear in:
Palaeogeography, Palaeoclimatology, Palaeoecology
Received date: Revised date: Accepted date:
7 December 2015 14 March 2016 21 March 2016
Please cite this article as: Lagnaoui, Abdelouahed, Klein, Hendrik, Saber, Hafid, Fekkak, Abdelilah, Belahmira, Abouchoua¨ıb, Schneider, Joerg.W., New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the Argana Basin, western High Atlas, Morocco — Ichnotaxonomic implications, Palaeogeography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.03.022
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ACCEPTED MANUSCRIPT New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the
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implications
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Argana Basin, western High Atlas, Morocco – ichnotaxonomic
Abdelouahed Lagnaouia,b*, Hendrik Kleinc, Hafid Sabera, Abdelilah Fekkaka, Abouchouaïb Belahmiraa,d, Joerg. W. Schneider b,d
Geodynamic and Geomatic Laboratory, Department of Geology, Faculty of Sciences,
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a
b
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Chouaïb Doukkali University, El Jadida, Morocco Department of Paleontology and Stratigraphy, Institute of Geology and Petroleum Technologies, Kazan (Volga Region) Federal University, Kazan, Russia
d
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Saurierwelt Paläontologisches Museum, Neumarkt, Germany
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c
TU Bergakademie Freiberg, Institut für Geologie, Freiberg/Sa, Germany.
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Keywords: Tetrapod ichnoassemblages, Scoyenia ichnofacies, Red-beds, Carnian-Norian, Irohalene Member, Moroccan High Atlas, North Africa.
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*Corresponding author. E-mail address: [email protected]
ABSTRACT New discoveries of tetrapod footprints from the Irohalene Member (T5, Upper Triassic, Carnian) of the Timezgadiouine Formation near Irohalene (Argana Basin, Morocco) are assigned
to
Parachirotherium
isp.,
Atreipus-Grallator
isp.
(Dinosauromorpha),
Brachychirotherium isp. (crocodylian-stem archosaurs), Apatopus lineatus (phytosaurs) and Rhynchosauroides (lepidosauromorphs/archosauromorphs). Parachirotherium is present on the surfaces with different tetradactyl-pentadactyl extramorphological variations, similar to the preservation mode observed at the type locality of the ichnogenus in the Middle Triassic 1
ACCEPTED MANUSCRIPT of the European Germanic Basin. Described specimens permit a re-evaluation of footprints described earlier from the Irohalene locality that are synonymized
here with
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Parachirotherium and Atreipus-Grallator. The presence of Brachychirotherium is the second
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record in North Africa and Morocco. The assemblage is similar in composition to other T5
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localities and to some ichnofaunas in North America and central Europe. Biostratigraphically, the occurrence of Brachychirotherium indicates the respective biochron that can be cross-
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correlated with the Carnian-Rhaetian interval.
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1. Introduction
In recent years, the Argana Basin of Morocco became an important region for the dicovery of Paleozoic-Mesozoic tetrapod footprints and a rich source for ichnological research. Several
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ichnotaxa, previously unknown from North Africa or even the African continent, where described for the first time (Hminna, 2013; Hminna et al., 2012; 2013; Klein et al., 2010,
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2011, 2013; Lagnaoui, 2014a, b; Lagnaoui et al., 2012; Voigt et al., 2010, 2011). The Irohalene Member (T5) of the Timezgadiouine Formation (Upper Triassic, Carnian) in the
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Argana Basin is essentially known for its rich vertebrate fauna (Jalil, 1999; Jalil and Peyer, 2007; Kammerer et al., 2011). Tetrapod footprints were described from this unit by Biron and Dutuit (1981) and recently by Lagnaoui et al. (2012). The latter paper was essentially based on material from 2011 field work, when diverse tetrapod track assemblages together with abundant Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations. The footprints were assigned to Apatopus, Atreipus-Grallator, Eubrontes
isp.,
Parachirotherium,
cf.
Parachirotherium
postchirotherioides,
Rhynchosauroides ispp., and Synaptichnium isp. (Lagnaoui et al., 2012). Recently, during further fieldwork in the Argana Basin following the First International Congress on Continental Ichnology (ICCI) in El Jadida, 2015, the authors documented numerous new finds of footprints, mostly those of archosaurs. These are preserved on the 2
ACCEPTED MANUSCRIPT lower and upper surfaces of loose sandstone blocks scattered around localities near Irohalene village in the northern part of the Argana Basin (Fig. 1). Preservation of the footprints and co-
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occurrence of abundant invertebrate trace fossils on the surfaces is similar to that of
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specimens figured and described from Irohalene by Biron and Dutuit (1981). Even if the exact
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position of locations mentioned by the latter authors is vague, it is likely that the new discoveries come from same or nearby spots. Moreover, the partly well-preserved imprints and morphological details permit a re-evaluation of the ichnotaxonomy of Irohalene footprints
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and some conclusions drawn by Biron and Dutuit (1981).
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In the following we give a detailed description of the new material and discuss ichnotaxonomic affinities, including similar footprints from other localities in the global
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Triassic record.
1.1 Institutional abbreviations
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CDUE = Department of Geology, Chouaïb Doukkali University, El Jadida, Morocco.
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2. Material and methods
10 slabs (CDUE 360–369) from CDUE locality 100 with 7 isolated pes imprints and 5 pesmanus sets. 4 slabs (CDUE 370–373) from CDUE locality 101 with 4 isolated pes imprints and 1 pes-manus set. All in all, 23 imprints. Of these, CDUE 360, 361 and 362 were collected and are now housed in the footprint collection of the Department of Geology, Chouaïb Doukkali University, El Jadida, Morocco. All footprints were photographed with natural light in the field. Some collected specimens were additionally photographed with artificial light in the laboratory, as specified in the captions of figures. Outline tracings were made on transparency film in the field and finally digitalized with a vector-based drawing software. Measurements of the tracks were taken using standard methods proposed by Haubold (1971) and Leonardi (1987). 3
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3. Geological setting
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The Argana Basin is situated between Marrakech and Agadir at the south-western edge of
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the High Atlas mountain range in central Morocco (Fig. 1). It refers to an about 20 km wide
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and 70 km long, NNE-SSW trending area of excellently exposed Permian and Triassic continental deposits. The Irohalene area is located in the northern part of Argana Basin, which is bounded by Jurassic and Cretaceous strata in the north and west, and by the epizonal
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metamorphic Palaeozoic inlier of the Western High Atlas in the east that consists of the Early
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Cambrian of Aït Bkhyar and the Middle Cambrian of Aït Lahcen (Ferrandini et al., 1987 ; Saber, 1998, Saber et al., 2007). The red-bed succession, mainly Triassic in this locality, rests with a major unconformity on the Paleozoic basement and is unconformably overlain by
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Jurassic strata. Generally, in the Argana Basin, the 2000–5000 m thick succession of red-beds is subdivided into three formations and eight members: (1) the Permian Ikakern Formation
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(T1-T2; 900–1800 m); (2) the Lower-Upper Triassic Timezgadiouine Formation (T3-T5; 1000–2000 m); and (3) the Upper Triassic Bigoudine Formation (T6-T8; 300–1500 m)
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(Tixeront, 1973; Brown, 1980; Jalil, 1999; Hofmann et al., 2000; El Arabi et al., 2006; Klein et al., 2009, 2010, 2011, 2013; Voigt et al., 2010, 2011; Hminna et al., 2012; Hminna, 2013; Lagnaoui et al., 2012; Lagnaoui, 2014). It has to be noted that the Tourbihine Member (T2) (the uppermost part of the Ikakern Formation) is missing in the studied area and crops out locally more to the South. All archosaur footprints described here come from the base of the uppermost unit of the Timezgadiouine Formation (T5, Irohalene Member). The Irohalene Member (T5) lies conformably on the Aglegal Member (T4) and is conformably overlain by the Tadart Ouadou Member (T6). Between Ameskroud in the southwest and Imi-N-Tanoute in the north-eastern part of the basin, the thickness of the Irohalene Member varies non-systematically between 200 and 500 m. The succession is mud-dominated but in the upper part (100–200 m) is 4
ACCEPTED MANUSCRIPT characterized by increasingly common intercalations of sandstone interpreted to represent deposition on a low-gradient of alluvial plain with meandering rivers and extensive
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floodplains (Hofmann et al., 2000; Lagnaoui et al., 2012; Hminna, 2013; Lagnaoui, 2014).
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The Irohalene Member (T5) is considered to be of Late Triassic (Carnian) age based on
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vertebrate skeletons and tracks (Dutuit, 1977a, b; Jalil, 1999; Jalil and Peyer, 2007; Lucas, 2010; Kammerer et al., 2011; Hminna, 2013; Lagnaoui, 2014a, b; Lagnaoui et al., 2012). The described Archosaur tracks were discovered at the Irohalene locality near Tizi
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M’Achou area, about 17 km southwest of Imi-N-Tanoute (CDUE localities 100 and 101,
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Irohalene Member) (Fig. 1). At CDUE locality 100, two track-bearing beds with 10 and 20 cm thickness occur. These are yellowish-red to greenish fine-grained sandstones separated by mm-thick silty to clayey mudstone (Fig. 2). Current ripples, mudcracks and diverse
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invertebrate traces point to deposits of a stream bed with recurrent subaerial exposure. The 410 cm-thick succession at CDUE locality 100 consists of trough cross-bedded and tabular-
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bedded sandstone with intercalations of friable reddish-brown siltstone (Fig. 2). Archosaur footprints are preserved on the lower and upper surfaces of a fine-grained sandstone.
beds.
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Footprints of CDUE locality 101 are loose blocks that obviously originate from the same
4. Archosaur footprints from Irohalene Member 4. 1 Former research Archosaur footprints from the Irohalene Member (T5) of the Timezgadiouine Formation of the Argana Basin have been described by Biron and Dutuit (1981). These authors introduced several new ichnotaxa: Tridactylus machouensis ichnogen. nov. ichnosp. nov., Anomoepus moghrebensis ichnosp. nov., Quadridigitus dubius ichnogen. nov. ichnosp. nov., Pentichnus largus ichnogen. nov. ichnosp. nov. Furthermore, small footprints from the Irohalene Member were described together with other archosaur and non-archosaur footprints from the Ourika 5
ACCEPTED MANUSCRIPT Basin of Morocco (Biron and Dutuit (1981). In 2012, Lagnaoui et al. described a tetrapod ichnofauna from the Irohalene Member (T5). The assemblage included the archosaur footprint
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ichnotaxa Apatopus, Atreipus-Grallator, Eubrontes, Parachirotherium cf. Parachirotherium
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postchirotherioides and Synaptichnium as well as some indeterminate archosaur ichnotaxa. In
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this paper, Lagnaoui et al. (2012) suggest a possible similarity of some ichnotaxa with those described by Biron and Dutuit (1981). In a conference paper, Belvedere and Jalil (2015) present several footprints from the Biron and Dutuit (1981) material deposited in the Muséum
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national d’Histoire Naturelle, Paris, identifying these as cf. Brachychirotherium, cf.
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Parachirotherium and cf. Grallator. 4. 2 Description
Four archosaur morphotypes are present:
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1) Large, relatively broad, tetradactyl to pentadactyl and digitigrade to semiplantigrade pes imprints with a digit divarication II–IV ranging from 25° to 67° (Figs. 3, 4A-E). Their
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maximum size reaches 29 cm in length (including digit V, if preserved) and 23 cm in width. The pes is functionally tridactyl with digit III being by far longest, while digits II and IV are
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shorter and subequal in length, or digit IV is slightly longer than digit II. Digit I (hallux) is short and posteriorly shifted relative to the digit group II–IV. It is slightly curved inward. Digit V is an oval basal pad positioned in line with the axis of digit IV. The shape of the digits is variable from broad and rounded to narrow and distally tapering due to different substrate conditions. Distinctly impressed, robust triangular claw traces are present on digits I–IV. Occasionally incomplete traces of a small tri-pentadactyl manus are visible (Fig. 4B, 4E). 2) Large tridactyl and more slender shaped digitigrade to semidigitigrade pes imprints, 23 cm in length and 12 cm in width (Fig. 5A). Their digit divarication II–IV is small (28°). In specimen CDUE 361 (Fig. 5A), which is the best preserved example, digit III is by far longest, whereas digits II and IV are shorter. The pes has a characteristic mesaxonic, symmetrical shape. Digits are relatively long and slender with rounded pads that are more or 6
ACCEPTED MANUSCRIPT less distinctly preserved. Digit II shows three pads, with the most proximal one being circular in shape and distinctly separated from the distal portion. Pads in digit III are indistinct,
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whereas digit IV appears to have four pads. A distinct elongate oval pad is visible proximally
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to and in line with digit IV. Triangular to elongated claw traces are preserved with that of
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digit II being distinct. Occasionally associated with this is a small tri-pentadactyl, more rounded small manus imprint. In specimen CDUE 361 it is positioned close to the anterolateral margin of pedal digit IV. It is about 8 cm in length and 7 cm in width and shows three
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digits, that are identified here as digits II–IV (Fig. 5A). Manual digits are subequal in length,
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digits two and III point anteriorly relative to the long axis of the pes, whereas digit IV is strongly abducted laterally. Claw traces as well as pad impressions are indistinct or absent. 3) small-large-sized pentadactyl and semiplantigrade pes imprints with broad short digits
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mostly associated with a tri-pentadactyl manus trace (Figs. 5B, 6A). Digit III is longest, followed by digits II and IV, whereas digit I is short. CDUE 360 (Fig. 5B) is the best
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preserved specimen. The pes imprint is 8.5 cm in length and 7.2 cm in width. Digit V is preserved as an oval pad in a postero-lateral position relative to the anterior digit group I–IV.
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Phalangeal pads are indistinctly visible in the slightly more slender shaped digit IV. Small claw traces are observed in digits III and IV. The manus impression consists of three digit traces (presumably digits II, III and IV). It is positioned close to the antero-medial margin of the pes and is rotated slightly outward relative to the latter. A triangular acuminate claw trace is preserved on the outermost digit. A large pes-manus couple (CDUE 364) (Fig. 6A) is incomplete, representing the anterior portion (digits I–IV) of the pes, about 15 cm in length and 16.5 cm in width. The tridactyl manus trace, 7.5 in length and 10.5 cm in width is positioned close to the antero-medial margin of the pes. Digits of both the pes and the manus are short, broad, often with a rounded overall shape and small triangular claws pointing laterally.
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ACCEPTED MANUSCRIPT 4) Large ectaxonic pentadactyl pes imprints with an anterior digit group where digit IV is longest, followed by digits III, II and I which is shortest. Digit V is postero-laterally
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positioned and consists of a massive basal portion running into an elongated "heel"
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impression, and a short and thinner, possible phalangeal segment (Fig. 6B). The pes imprint is
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18 cm in length and width, respectively. Digits I–IV are curved inward distally and more sharp claws are indicated at least in digits III and IV.
Furthermore, some incomplete archosaur pes and manus imprints are present. CDUE 360
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(Fig. 6C) is a pentadactyl chirotheriid pes imprint, 14 cm long and 8.5 cm in width. It reflects
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a functionally tridactyl but pentadactyl pes with a very short and thin digit I and a laterally everted digit V, preserved as an oval basal pad only. It lacks a manus impression. Specimen CDUE 368 (Fig. 6D) consists of the fragmentary distal portion of a pes impression showing
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three digits (6 cm in length, 12 cm in width) and a tetradactyl-pentadactyl manus trace with short and thick, rounded digits arranged in a semicircular pattern, 8.5 cm in length and 12.5
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cm in width.
An isolated small tridactyl imprint (2.7 cm in length, 1.5 cm in width) associated with large
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tridactyl archosaur footprints (Fig. 5A) can be assigned to Rhynchosauroides isp. based on the overall-morphology with long and slender, curved digits.
5. Ichnotaxonomic implications Biron and Dutuit (1981) have assigned morphologically identical footprints from the Irohalene Member, obviously from the same locality (see above), to several new ichnotaxa such as Tridactylus machouensis, Anomoepus moghrebensis and Quadridigitus dubius. Against the background of the clear presence of the ichnogenus Parachirotherium and some grallatorid forms (Atreipus-Grallator, Eubrontes) in the Irohalene Member (Lagnaoui et al., 2012, Fig. 7A-B), it is obvious that most footprints described by Dutuit and Biron (1981)
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ACCEPTED MANUSCRIPT represent extramorphological (substrate-related) variations of these ichnotaxa. This is demonstrated in the following.
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The overall shape of pes and manus imprints in Morphotype 1) resembles characteristic
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pentadactyl, but functionally tridactyl pes imprints with an associated small manus seen in the
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ichnogenus Parachirotherium and some similar forms. Parachirotherium was originally named by Kuhn (1958) based on material from the Middle Triassic (Late Ladinian) of the Germanic Basin. The ichnogenus has been identified also from the Upper Triassic Irohalene
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Member (Timezgadiouine Formation, T5, Carnian) of Ait Moussi locality in the Argana Basin
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(Lagnaoui et al., 2012; Fig. 7A). However, the fifth digit of the pes is mostly lacking in the new material from the Irohalene locality. Therefore, most pes imprints are tetradactyl, only with a short hallux, which is considered here as an extramorphological variation of the
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pentadactyl form. Only in rare cases a small oval pad is visible in a position where the fifth digit would be expected (CDUE 369; Fig. 4A). Because of the overall similarity with the
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ichnogenus Parachirotherium, but considering their incompleteness, we assign these footprints tentatively to Parachirotherium isp. Furthermore, some footprints from the
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Irohalene Member figured in Biron and Dutuit (1981, planche IIA–F, J–L) are re-assigned here to Parachirotherium isp.. This concerns tetradactyl-pentadactyl footprints described by these authors under Anomoepus moghrebensis and Quadridigitus dubius (Biron and Dutuit, 1981, planche II, F, L, K). Morphotype 2) when well preserved (CDUE 361; Figs. 5A) is similar in shape of the pes and manus imprints with those of the ichnogenus Atreipus (Olsen and Baird, 1986). The slender grallatorid pes imprint combined with a chirothere-like manus is typical of Atreipus that originally was described from the Upper Triassic of the Newark Supergroup (Olsen and Baird, 1986). Several grallatorid footprints fom the Irohalene Member (T5) of the Timezgadiouine Formation and from the Tadart Ouadou Member (T6) of the Bigoudine 9
ACCEPTED MANUSCRIPT Formation have been tentatively referred to the plexus Atreipus-Grallator, due to variation in the presence/absence of a manus trace (sensu Haubold and Klein, 2002), a larger form to
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Eubrontes (Olsen et al., 1998; Lucas et al., 2006; Lagnaoui et al., 2012; Fig. 7B). Because of
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their strong similarity with these footprints, we assign Morphotype 2 to Atreipus-Grallator.
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Also, the ichnotaxon Tridactylus machouensis erected by Biron and Dutuit (1981, planche II, A–E, J) is re-assigned here to Atreipus-Grallator based on the congruence in shape. Haubold
and
Klein
(2000,
2002) partly
along
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Parachirotherium–Atreipus–Grallator
discussed
transitional
single
morphs
trackways,
between
emphasizing
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ichnotaxonomical problems resulting from this observation. The Irohalene footprints again raise the same issue by the co-occurrence and transition of Parachirotherium- and AtreipusGrallator-like forms on the same surface or in the same unit.
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Moreover, tri-tetradactyl footprints with a posteriorly shifted reduced hallux from MiddleUpper Triassic deposits of Argentina (Melchor and De Valais, 2006; Marsicano et al. , 2007,
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2010) strongly resemble the footprints from Irohalene. Some of these have been assigned to Rigalites, an ichnogenus introduced by Huene (1931) based on trackways from the Los
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Rastros Formation (Ladinian–?Carnian) of Argentina. These are large tetradactyl pes imprints with an associated pentadactyl manus. Some imprints show a massive proximal region or rounded "heel" pad that could be interpreted as remnants of the reduced digit V. Moreover, Parachirotherium, Atreipus-Grallator, Rigalites and the footprints from the Irohalene Member show similar shape, proportions and digit orientation of the manus: 1) digits II, III and IV dominating in the imprint, 2), digits II and III longest and pointing forward, whereas digit IV is short and laterally spread. We note that the ichnogenera Rigalites and Parachirotherium as well as some similar ichnotaxa are presently under study and their relationship is re-examined by one of us (HK). From the Pekin Formation (Newark Supergroup, Carnian) of the Deep River Basin in North Carolina, USA, Olsen and Huber (1998) describe tetradactyl to pentadactyl, but 10
ACCEPTED MANUSCRIPT functionally tridactyl, pes imprints that clearly show a posteriorly shifted short hallux whereas digit V, if present, is reduced to an oval basal pad only and position far posterior to the rest of
these footprints
with the ichnogenus
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Huber (1998) mention the similarity of
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the pes. However, the material is incomplete and manus imprints are missing. Olsen and
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Parachirotherium. Nevertheless, there are some morphological differences between these tracks from North America, Rigalites from South America and the footprints described here from the Irohalene Member of the Argana Basin. Parachirotherium is distinct, especially in
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the development of the fifth pedal digit. However, this could be due to the different reduction
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of the latter in various lineages of dinosauromorphs during their radiation in the MiddleUpper Triassic (see below).
Morphotype 3 shows the typical morphology and diagnostic features of the ichnogenus
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Brachychirotherium by the broad overall shape of the pes imprint and by the short, broad digits with tiny claws, and the oval basal pad of digit V being in a postero-lateral position
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relative to the anterior digit group I–IV (Beurlen, 1950; Baird, 1957; Karl and Haubold, 1998; Lucas et al., 2010; Klein et al., 2015). It is assigned here tentatively to Brachychirotherium
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isp. A specific determination is not possible presently, because of the isolated material. It is the second record of the ichnogenus in the Upper Triassic of Morocco after the findings at the Sidi Said Maachou locality (Hminna et al., 2013). Morphotype 4 is represented by an isolated pes only. The digit proportions, with pedal digit IV being longest, and the inward curvature of distal ends that show sharp claw traces, are identical with pes imprints of the ichnotaxon Apatopus lineatus. Apatopus lineatus is also known from the Irohalene Member by a longer trackway (Lagnaoui et al., 2012). Therefore we assign Morphotype 4 and the isolated pes imprint here to Apatopus lineatus.
6. Trackmakers and biostratigraphic implications
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ACCEPTED MANUSCRIPT Parachirotherium
and
Atreipus-Grallator
footprints
have
been
attributed
to
dinosauromorph trackmakers (Haubold and Klein, 2000, 2002; D'Orazi-Porchetti et al., 2008).
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In particular, Atreipus was alternatively considered to be of ornithischian affinity by some
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workers (Olsen and Baird, 1986). Interestingly, all these functionally tridactyl footprints with
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strongly reduced or absent pedal digits I and V have their first occurrence in the late Anisian and appear to be widely distributed and diversified from near the Ladinian-Carnian boundary (Klein and Lucas, 2010). This corresponds with the stratigraphic distribution of the known
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skeletal record of dinosauromorphs (Dzik, 2003; Langer et al., 2013). From the Irohalene
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Member (T5) of the Argana Basin, skeletal remains of the dinosauromorph Diodorus scytobrachion are known (Kammerer et al., 2011). The track record suggests that there was a strong radiation of dinosauromorphs during the late Middle Triassic-early Late Triassic time
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interval with different small to medium-sized forms that show a different degree of reduction of pedal digits I and V. The new discoveries from the Irohalene Member support this.
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For trackmakers of Brachychirotherium, aetosaurs (Heckert et al., 2010; Lucas and Heckert, 2011) as well as "rauisuchians" such as Postosuchus (Hminna et al., 2013; Klein et
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al., 2015) have been proposed. Both groups are known from T5 skeletal assemblages (Jalil, 1999; Jalil and Peyer, 2007). However, a definitive correlation with Brachychirotherium from T5 is presently not possible. The ichnogenus Apatopus has been widely accepted as a phytosaur track (Padian et al., 2010; Lagnaoui et al., 2012; Klein and Lucas, 2013). Rhynchosauroides is considered to be of lepidosauromorph and/or archosauromorph affinity. Biostratigraphically, the occurrence of the ichnogenera Brachychirotherium and Apatopus in the Irohalene assemblage indicates the Brachychirotherium faunachron that can be crosscorrelated with the Late Triassic (Carnian-Rhaetian) (Klein and Lucas, 2010).
7. Conclusions 12
ACCEPTED MANUSCRIPT New discoveries of tetrapod footprints from the Irohalene Member (T5) of the Timezgadiouine Formation are assigned to the ichnogenera Parachirotherium, Atreipus-
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Grallator, Brachychirotherium and Apatopus based on overall-morphology and characteristic
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digit proportions. It is evident that the most common tetradactyl imprints with a short trace of
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the hallux are extramorphological variations or incomplete pes impressions of pentadactyl Parachirotherium. The latter is occasionally present at Irohalene and has been also described from other T5 localities (Lagnaoui et al., 2012). The variation in the number and shape of
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preserved digits in Parachirotherium is congruent with similar phenomena observed at the
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type locality of this ichnogenus in the Middle Triassic of the Germanic Basin of central Europe (Haubold and Klein, 2000, 2002).
Footprints of the Atreipus–Grallator plexus are also present. Together with Apatopus and
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the non-archosaur ichnotaxon Rhynchosauroides, the Irohalene ichnofauna documents a similarity in composition with assemblages from other T5 localities (Lagnaoui et al., 2012),
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North America (Olsen and Huber, 1998) and central Europe (Haubold and Klein, 2000, 2002). The presence of Brachychirotherium is the second record from North Africa and Morocco
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and the first from the Argana Basin (Hminna et al., 2013). Klein and Lucas (2010) proposed five tetrapod-footprint biochrons for the Triassic defined by the first appearance of distinct archosaur ichnotaxa and associated characteristic tracks. The footprint assemblages of the Irohalène Member (T5) in the Argana Basin can be attributed to the Late Triassic Brachychirotherium biochron (Klein and Lucas, 2010) based on the co-occurrence of Brachychirotherium, Atreipus–Grallator and Apatopus. The re-evaluation of the ichnotaxonomy of the Irohalene assemblage based on the new material suggests that footprints formerly described by Biron and Dutuit (1981) under Tridactylus machouensis, Anomoepus moghrebensis and Quadridigitus dubius are
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ACCEPTED MANUSCRIPT extramorphological variations of Parachirotherium and Atreipus-Grallator and are therefore considered here as junior synonyms of the latter.
Atreipus-Grallator),
crocodylian-stem
(Brachychirotherium)
and
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(Parachirotherium,
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Trackmakers of the Irohalene footprints were most probably dinosauromorph
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phytosaurian (Apatopus) archosaurs as well as lepidosauromorph/archosauromorph groups (Rhynchosauroides).
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Lagnaoui, A., 2014b. Late Palaeozoic and Early Mesozoic Continental Ichnofossils from Morocco: Biostratigraphy, Palaeoecology end end-Permian Biotic Crisis evidence. Arabian J. Earth Sci. 1 (4) , 26–35.
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Dinosauromorpha. In: Nesbitt, S.J., Desojo, J.B., Irmis, R.B. (Eds.), Anatomy, phylogeny and paleobiology of early archosaurs and their kin. Geol. Soc. London, Spec. Publ. 379,
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Leonardi, G. (Ed.), 1987. Glossary and manual of tetrapod footprint palaeoichnology. Minist.
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Min. En. Depart. N. Prod. Mineral, Brasilia, 117 p. Lucas, S.G., Heckert, A.B., 2011. Late Triassic aetosaurs as the trackmaker of the tetrapod footprint ichnotaxon Brachychirotherium. Ichnos18 (4), 197–208. Lucas, S.G., Klein, H., Lockley, M.G., Spielmann, J., Gierlinski, G.D., Hunt, A.P., Tanner, L.H., 2006. Triassic-Jurassic stratigraphic distribution of the theropod footprint ichnogenus Eubrontes. New Mexico Mus. Nat. Hist. Sci. Bull. 37, 68–93. Lucas, S.G., Spielmann, J.A., Klein, H. and Lerner, A.J., 2010. Ichnology of the Upper Triassic Redonda Formation (Apachean) in east-central New Mexico. New Mexico Mus. Nat. Hist. Sci. Bull. 47, 75 p. Marsicano, C.A., Domnanovich, N.S., Mancuso, A.C., 2007. Dinosaur origins: evidence from the footprint Record. Historical Biology 19 (1), 83–91. 18
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Melchor, R.N., De Valais, S., 2006. A review of Triassic tetrapod track assemblages from
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Olsen, P.E., Baird, D., 1986. The ichnogenus Atreipus and its significance for Triassic Biostratigraphy. In: Padian, K. (Ed.), The beginning of the age of dinosaurs. Cambridge
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Olsen, P.E., Huber, P., 1998. The oldest Late Triassic footprint assemblage from North America (Pekin Formation, Deep River Basin, North Carolina, USA). Southeastern Geology 38, 77–90.
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Olsen, P.E., Smith, J.B., McDonald, N.G., 1998. Type material of the type species of the classic theropod footprint genera Eubrontes, Anchisauripus, and Grallator (Early
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Jurassic, Hartford and Deerfield Basins, Connecticut and Massachusetts, U. S. A.). J. Vertebr. Paleontol. 18, 586–601.
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Padian, K., Li, C., Pchelnikova, J., 2010. The trackmaker of Apatopus (Late Triassic, North America) implications for the evolution of archosaur stance and gait. Palaeontology 53, 175–189.
Saber, H., 1998. The Stephano-Permian of the western High Atlas: geological and geodynamic evolution (Morocco). Doctorat Es-Sciences (thèse d'Etat), Chouaïb Doukkali University, El Jadida, Morocco, 212 pp. Saber, H., El Wartiti, M., Hmich, D., Schneider, J.W., 2007. Tectonic evolution from the Hercynian shortening to the Triassic extension in the Paleozoic Western High Atlas (Morocco). J. Iberian Geol. 33 (1), 31–40. Tixeront, M., 1974. Carte géologique et minéralogique du Couloir d’Argana, 1/100 000. Ed. Serv. Géol. Maroc Notes Mémoires, 205. 19
ACCEPTED MANUSCRIPT Tixeront, M., 1973. Lithostratigraphie et minéralisation cuprifères et uranifères stratiformes syngénétiques et familières des formations détritiques permo-triasiques du Couloir
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d’Argana (Haut-Atlas occidental, Maroc). Notes Mém. Serv. Géol. Maroc 33 (249), 147–
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177.
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Voigt, S., Hminna, A., Saber, H., Schneider, J.W., Klein, H., 2010. Tetrapod footprints from the uppermost level of the Permian Ikakern Formation (Argana Basin, Western High Atlas, Morocco). J. African Earth Sci. 57, 470–478.
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Voigt, S., Schneider, J. W., Saber, H., Hminna, A., Lagnaoui, A., Klein, H., Brosig, A.,
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Fischer, J., 2011. Complex tetrapod burrows from Middle Triassic red beds of the Argana Basin (Western High Atlas, Morocco). Palaios 26 (9), 555–566.
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Figure captions
Fig. 1. Geographic and stratigraphic position of footprint localities. A–C. Position in Morocco
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and in the Argana Basin. D. Geological map with Irohalene localities indicated by star (after, Tixeront, 1974). E. Stratigraphic section with Paleozoic-Mesozoic succession in
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the Argana Basin and the footprint horizon indicated by star. Fig. 2. Stratigraphic section at footprint locality CDUE 100 with the distribution of body- and ichnofossils and sedimentary structures. Fig. 3. Two tetradactyl pes imprints (CDUE 370) from CDUE locality 101 preserved as concave
epireliefs,
representing
incomplete
extramorphological
variations
of
Parachirotherium isp. with slender digit traces. A. Photograph showing overview of surface with imprints (c, d) and ripple marks. B. Sketches of pes imprints (c, d corresponding to footprints demarcated in A). C. Photograph with detail of imprint c. Scale bar 5 cm.
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ACCEPTED MANUSCRIPT Fig. 4. Tridactyl-pentadactyl archosaur footprints Parachirotherium isp. from Irohalene localities as photographs and sketches; all preserved as convex hyporeliefs. A–A'. Large
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pentadactyl pes imprint (CDUE 369) from CDUE locality 100 with broad digit traces. B–
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B'. Tetradactyl pes imprint and associated manus imprint CDUE 371 from CDUE locality
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101. C–C'. Tetradactyl pes imprint CDUE 372 from CDUE locality 101. D–D'. Tetradactyl pes imprint CDUE 374 from CDUE locality 101. E–E'. Tridactyl pes imprint
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and associated tridactyl manus imprint CDUE 363 from CDUE locality 100. Fig. 5. Archosaur footprints from Irohalene locality CDUE 100 as photographs and sketches;
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all preserved as convex hyporeliefs. A–A'. CDUE 361, two tridactyl pes imprints; one with associated tridactyl manus imprint (center); with tridactyl small Rhynchosauroides
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isp. in front of digit III (top). B–B'. CDUE 360, pentadactyl pes imprint and associated
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tridactyl manus imprint Brachychirotherium isp. B photographed under artificial light.
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Fig. 6. Archosaur footprints from Irohalene localities preserved as convex hyporeliefs. A–A'. Fragmentary pes and manus imprints Brachychirotherium isp. (CDUE 364) from CDUE locality 100. B–B'. pentadactyl pes imprint Apatopus lineatus CDUE 367 from CDUE
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locality 100. C–C'. Pentadactyl chirotheriid pes imprint CDUE 362 from CDUE locality 100. D–D'. Fragmentary pes-manus set (uncollected). C photographed under artificial light. Fig. 7. Photographs and sketches of archosaur footprints preserved as concave epireliefs from the Upper Triassic of the Timezgadiouine Formation described by Lagnaoui et al. (2012) for comparison. A–A’. Parachirotherium cf. Parachirotherium postchirotherioides Rehnelt, 1950. Left pes-manus set, CDUE 325, from CDUE locality 38 (Irohalene Member (T5). B–B’. Atreipus – Grallator. Left pes-manus set, CDUE 350, from CDUE locality 41 (Tadart Ouadou Member (T6)). All photographed under artificial light.
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New discoveries of Late Triassic tetrapod footprints from Morocco. Ichnotaxonomic re-evaluation of footprints described earlier from the Late Triassic deposits of Morocco. The second record of the ichnogenus Brachychirotherium in North Africa and Morocco.
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S0031-0182(16)30035-9 doi: 10.1016/j.palaeo.2016.03.022 PALAEO 7755
To appear in:
Palaeogeography, Palaeoclimatology, Palaeoecology
Received date: Revised date: Accepted date:
7 December 2015 14 March 2016 21 March 2016
Please cite this article as: Lagnaoui, Abdelouahed, Klein, Hendrik, Saber, Hafid, Fekkak, Abdelilah, Belahmira, Abouchoua¨ıb, Schneider, Joerg.W., New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the Argana Basin, western High Atlas, Morocco — Ichnotaxonomic implications, Palaeogeography, Palaeoclimatology, Palaeoecology (2016), doi: 10.1016/j.palaeo.2016.03.022
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT New discoveries of archosaur and other tetrapod footprints from the Timezgadiouine Formation (Irohalene Member, Upper Triassic) of the
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implications
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Argana Basin, western High Atlas, Morocco – ichnotaxonomic
Abdelouahed Lagnaouia,b*, Hendrik Kleinc, Hafid Sabera, Abdelilah Fekkaka, Abouchouaïb Belahmiraa,d, Joerg. W. Schneider b,d
Geodynamic and Geomatic Laboratory, Department of Geology, Faculty of Sciences,
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a
b
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Chouaïb Doukkali University, El Jadida, Morocco Department of Paleontology and Stratigraphy, Institute of Geology and Petroleum Technologies, Kazan (Volga Region) Federal University, Kazan, Russia
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Saurierwelt Paläontologisches Museum, Neumarkt, Germany
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c
TU Bergakademie Freiberg, Institut für Geologie, Freiberg/Sa, Germany.
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Keywords: Tetrapod ichnoassemblages, Scoyenia ichnofacies, Red-beds, Carnian-Norian, Irohalene Member, Moroccan High Atlas, North Africa.
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*Corresponding author. E-mail address: [email protected]
ABSTRACT New discoveries of tetrapod footprints from the Irohalene Member (T5, Upper Triassic, Carnian) of the Timezgadiouine Formation near Irohalene (Argana Basin, Morocco) are assigned
to
Parachirotherium
isp.,
Atreipus-Grallator
isp.
(Dinosauromorpha),
Brachychirotherium isp. (crocodylian-stem archosaurs), Apatopus lineatus (phytosaurs) and Rhynchosauroides (lepidosauromorphs/archosauromorphs). Parachirotherium is present on the surfaces with different tetradactyl-pentadactyl extramorphological variations, similar to the preservation mode observed at the type locality of the ichnogenus in the Middle Triassic 1
ACCEPTED MANUSCRIPT of the European Germanic Basin. Described specimens permit a re-evaluation of footprints described earlier from the Irohalene locality that are synonymized
here with
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Parachirotherium and Atreipus-Grallator. The presence of Brachychirotherium is the second
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record in North Africa and Morocco. The assemblage is similar in composition to other T5
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localities and to some ichnofaunas in North America and central Europe. Biostratigraphically, the occurrence of Brachychirotherium indicates the respective biochron that can be cross-
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correlated with the Carnian-Rhaetian interval.
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1. Introduction
In recent years, the Argana Basin of Morocco became an important region for the dicovery of Paleozoic-Mesozoic tetrapod footprints and a rich source for ichnological research. Several
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ichnotaxa, previously unknown from North Africa or even the African continent, where described for the first time (Hminna, 2013; Hminna et al., 2012; 2013; Klein et al., 2010,
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2011, 2013; Lagnaoui, 2014a, b; Lagnaoui et al., 2012; Voigt et al., 2010, 2011). The Irohalene Member (T5) of the Timezgadiouine Formation (Upper Triassic, Carnian) in the
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Argana Basin is essentially known for its rich vertebrate fauna (Jalil, 1999; Jalil and Peyer, 2007; Kammerer et al., 2011). Tetrapod footprints were described from this unit by Biron and Dutuit (1981) and recently by Lagnaoui et al. (2012). The latter paper was essentially based on material from 2011 field work, when diverse tetrapod track assemblages together with abundant Scoyenia invertebrate traces were discovered in the Triassic Timezgadiouine and Bigoudine formations. The footprints were assigned to Apatopus, Atreipus-Grallator, Eubrontes
isp.,
Parachirotherium,
cf.
Parachirotherium
postchirotherioides,
Rhynchosauroides ispp., and Synaptichnium isp. (Lagnaoui et al., 2012). Recently, during further fieldwork in the Argana Basin following the First International Congress on Continental Ichnology (ICCI) in El Jadida, 2015, the authors documented numerous new finds of footprints, mostly those of archosaurs. These are preserved on the 2
ACCEPTED MANUSCRIPT lower and upper surfaces of loose sandstone blocks scattered around localities near Irohalene village in the northern part of the Argana Basin (Fig. 1). Preservation of the footprints and co-
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occurrence of abundant invertebrate trace fossils on the surfaces is similar to that of
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specimens figured and described from Irohalene by Biron and Dutuit (1981). Even if the exact
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position of locations mentioned by the latter authors is vague, it is likely that the new discoveries come from same or nearby spots. Moreover, the partly well-preserved imprints and morphological details permit a re-evaluation of the ichnotaxonomy of Irohalene footprints
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and some conclusions drawn by Biron and Dutuit (1981).
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In the following we give a detailed description of the new material and discuss ichnotaxonomic affinities, including similar footprints from other localities in the global
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Triassic record.
1.1 Institutional abbreviations
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CDUE = Department of Geology, Chouaïb Doukkali University, El Jadida, Morocco.
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2. Material and methods
10 slabs (CDUE 360–369) from CDUE locality 100 with 7 isolated pes imprints and 5 pesmanus sets. 4 slabs (CDUE 370–373) from CDUE locality 101 with 4 isolated pes imprints and 1 pes-manus set. All in all, 23 imprints. Of these, CDUE 360, 361 and 362 were collected and are now housed in the footprint collection of the Department of Geology, Chouaïb Doukkali University, El Jadida, Morocco. All footprints were photographed with natural light in the field. Some collected specimens were additionally photographed with artificial light in the laboratory, as specified in the captions of figures. Outline tracings were made on transparency film in the field and finally digitalized with a vector-based drawing software. Measurements of the tracks were taken using standard methods proposed by Haubold (1971) and Leonardi (1987). 3
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3. Geological setting
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The Argana Basin is situated between Marrakech and Agadir at the south-western edge of
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the High Atlas mountain range in central Morocco (Fig. 1). It refers to an about 20 km wide
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and 70 km long, NNE-SSW trending area of excellently exposed Permian and Triassic continental deposits. The Irohalene area is located in the northern part of Argana Basin, which is bounded by Jurassic and Cretaceous strata in the north and west, and by the epizonal
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metamorphic Palaeozoic inlier of the Western High Atlas in the east that consists of the Early
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Cambrian of Aït Bkhyar and the Middle Cambrian of Aït Lahcen (Ferrandini et al., 1987 ; Saber, 1998, Saber et al., 2007). The red-bed succession, mainly Triassic in this locality, rests with a major unconformity on the Paleozoic basement and is unconformably overlain by
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Jurassic strata. Generally, in the Argana Basin, the 2000–5000 m thick succession of red-beds is subdivided into three formations and eight members: (1) the Permian Ikakern Formation
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(T1-T2; 900–1800 m); (2) the Lower-Upper Triassic Timezgadiouine Formation (T3-T5; 1000–2000 m); and (3) the Upper Triassic Bigoudine Formation (T6-T8; 300–1500 m)
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(Tixeront, 1973; Brown, 1980; Jalil, 1999; Hofmann et al., 2000; El Arabi et al., 2006; Klein et al., 2009, 2010, 2011, 2013; Voigt et al., 2010, 2011; Hminna et al., 2012; Hminna, 2013; Lagnaoui et al., 2012; Lagnaoui, 2014). It has to be noted that the Tourbihine Member (T2) (the uppermost part of the Ikakern Formation) is missing in the studied area and crops out locally more to the South. All archosaur footprints described here come from the base of the uppermost unit of the Timezgadiouine Formation (T5, Irohalene Member). The Irohalene Member (T5) lies conformably on the Aglegal Member (T4) and is conformably overlain by the Tadart Ouadou Member (T6). Between Ameskroud in the southwest and Imi-N-Tanoute in the north-eastern part of the basin, the thickness of the Irohalene Member varies non-systematically between 200 and 500 m. The succession is mud-dominated but in the upper part (100–200 m) is 4
ACCEPTED MANUSCRIPT characterized by increasingly common intercalations of sandstone interpreted to represent deposition on a low-gradient of alluvial plain with meandering rivers and extensive
T
floodplains (Hofmann et al., 2000; Lagnaoui et al., 2012; Hminna, 2013; Lagnaoui, 2014).
IP
The Irohalene Member (T5) is considered to be of Late Triassic (Carnian) age based on
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vertebrate skeletons and tracks (Dutuit, 1977a, b; Jalil, 1999; Jalil and Peyer, 2007; Lucas, 2010; Kammerer et al., 2011; Hminna, 2013; Lagnaoui, 2014a, b; Lagnaoui et al., 2012). The described Archosaur tracks were discovered at the Irohalene locality near Tizi
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M’Achou area, about 17 km southwest of Imi-N-Tanoute (CDUE localities 100 and 101,
MA
Irohalene Member) (Fig. 1). At CDUE locality 100, two track-bearing beds with 10 and 20 cm thickness occur. These are yellowish-red to greenish fine-grained sandstones separated by mm-thick silty to clayey mudstone (Fig. 2). Current ripples, mudcracks and diverse
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invertebrate traces point to deposits of a stream bed with recurrent subaerial exposure. The 410 cm-thick succession at CDUE locality 100 consists of trough cross-bedded and tabular-
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bedded sandstone with intercalations of friable reddish-brown siltstone (Fig. 2). Archosaur footprints are preserved on the lower and upper surfaces of a fine-grained sandstone.
beds.
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Footprints of CDUE locality 101 are loose blocks that obviously originate from the same
4. Archosaur footprints from Irohalene Member 4. 1 Former research Archosaur footprints from the Irohalene Member (T5) of the Timezgadiouine Formation of the Argana Basin have been described by Biron and Dutuit (1981). These authors introduced several new ichnotaxa: Tridactylus machouensis ichnogen. nov. ichnosp. nov., Anomoepus moghrebensis ichnosp. nov., Quadridigitus dubius ichnogen. nov. ichnosp. nov., Pentichnus largus ichnogen. nov. ichnosp. nov. Furthermore, small footprints from the Irohalene Member were described together with other archosaur and non-archosaur footprints from the Ourika 5
ACCEPTED MANUSCRIPT Basin of Morocco (Biron and Dutuit (1981). In 2012, Lagnaoui et al. described a tetrapod ichnofauna from the Irohalene Member (T5). The assemblage included the archosaur footprint
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ichnotaxa Apatopus, Atreipus-Grallator, Eubrontes, Parachirotherium cf. Parachirotherium
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postchirotherioides and Synaptichnium as well as some indeterminate archosaur ichnotaxa. In
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this paper, Lagnaoui et al. (2012) suggest a possible similarity of some ichnotaxa with those described by Biron and Dutuit (1981). In a conference paper, Belvedere and Jalil (2015) present several footprints from the Biron and Dutuit (1981) material deposited in the Muséum
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national d’Histoire Naturelle, Paris, identifying these as cf. Brachychirotherium, cf.
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Parachirotherium and cf. Grallator. 4. 2 Description
Four archosaur morphotypes are present:
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1) Large, relatively broad, tetradactyl to pentadactyl and digitigrade to semiplantigrade pes imprints with a digit divarication II–IV ranging from 25° to 67° (Figs. 3, 4A-E). Their
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maximum size reaches 29 cm in length (including digit V, if preserved) and 23 cm in width. The pes is functionally tridactyl with digit III being by far longest, while digits II and IV are
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shorter and subequal in length, or digit IV is slightly longer than digit II. Digit I (hallux) is short and posteriorly shifted relative to the digit group II–IV. It is slightly curved inward. Digit V is an oval basal pad positioned in line with the axis of digit IV. The shape of the digits is variable from broad and rounded to narrow and distally tapering due to different substrate conditions. Distinctly impressed, robust triangular claw traces are present on digits I–IV. Occasionally incomplete traces of a small tri-pentadactyl manus are visible (Fig. 4B, 4E). 2) Large tridactyl and more slender shaped digitigrade to semidigitigrade pes imprints, 23 cm in length and 12 cm in width (Fig. 5A). Their digit divarication II–IV is small (28°). In specimen CDUE 361 (Fig. 5A), which is the best preserved example, digit III is by far longest, whereas digits II and IV are shorter. The pes has a characteristic mesaxonic, symmetrical shape. Digits are relatively long and slender with rounded pads that are more or 6
ACCEPTED MANUSCRIPT less distinctly preserved. Digit II shows three pads, with the most proximal one being circular in shape and distinctly separated from the distal portion. Pads in digit III are indistinct,
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whereas digit IV appears to have four pads. A distinct elongate oval pad is visible proximally
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to and in line with digit IV. Triangular to elongated claw traces are preserved with that of
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digit II being distinct. Occasionally associated with this is a small tri-pentadactyl, more rounded small manus imprint. In specimen CDUE 361 it is positioned close to the anterolateral margin of pedal digit IV. It is about 8 cm in length and 7 cm in width and shows three
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digits, that are identified here as digits II–IV (Fig. 5A). Manual digits are subequal in length,
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digits two and III point anteriorly relative to the long axis of the pes, whereas digit IV is strongly abducted laterally. Claw traces as well as pad impressions are indistinct or absent. 3) small-large-sized pentadactyl and semiplantigrade pes imprints with broad short digits
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mostly associated with a tri-pentadactyl manus trace (Figs. 5B, 6A). Digit III is longest, followed by digits II and IV, whereas digit I is short. CDUE 360 (Fig. 5B) is the best
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preserved specimen. The pes imprint is 8.5 cm in length and 7.2 cm in width. Digit V is preserved as an oval pad in a postero-lateral position relative to the anterior digit group I–IV.
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Phalangeal pads are indistinctly visible in the slightly more slender shaped digit IV. Small claw traces are observed in digits III and IV. The manus impression consists of three digit traces (presumably digits II, III and IV). It is positioned close to the antero-medial margin of the pes and is rotated slightly outward relative to the latter. A triangular acuminate claw trace is preserved on the outermost digit. A large pes-manus couple (CDUE 364) (Fig. 6A) is incomplete, representing the anterior portion (digits I–IV) of the pes, about 15 cm in length and 16.5 cm in width. The tridactyl manus trace, 7.5 in length and 10.5 cm in width is positioned close to the antero-medial margin of the pes. Digits of both the pes and the manus are short, broad, often with a rounded overall shape and small triangular claws pointing laterally.
7
ACCEPTED MANUSCRIPT 4) Large ectaxonic pentadactyl pes imprints with an anterior digit group where digit IV is longest, followed by digits III, II and I which is shortest. Digit V is postero-laterally
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positioned and consists of a massive basal portion running into an elongated "heel"
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impression, and a short and thinner, possible phalangeal segment (Fig. 6B). The pes imprint is
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18 cm in length and width, respectively. Digits I–IV are curved inward distally and more sharp claws are indicated at least in digits III and IV.
Furthermore, some incomplete archosaur pes and manus imprints are present. CDUE 360
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(Fig. 6C) is a pentadactyl chirotheriid pes imprint, 14 cm long and 8.5 cm in width. It reflects
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a functionally tridactyl but pentadactyl pes with a very short and thin digit I and a laterally everted digit V, preserved as an oval basal pad only. It lacks a manus impression. Specimen CDUE 368 (Fig. 6D) consists of the fragmentary distal portion of a pes impression showing
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three digits (6 cm in length, 12 cm in width) and a tetradactyl-pentadactyl manus trace with short and thick, rounded digits arranged in a semicircular pattern, 8.5 cm in length and 12.5
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cm in width.
An isolated small tridactyl imprint (2.7 cm in length, 1.5 cm in width) associated with large
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tridactyl archosaur footprints (Fig. 5A) can be assigned to Rhynchosauroides isp. based on the overall-morphology with long and slender, curved digits.
5. Ichnotaxonomic implications Biron and Dutuit (1981) have assigned morphologically identical footprints from the Irohalene Member, obviously from the same locality (see above), to several new ichnotaxa such as Tridactylus machouensis, Anomoepus moghrebensis and Quadridigitus dubius. Against the background of the clear presence of the ichnogenus Parachirotherium and some grallatorid forms (Atreipus-Grallator, Eubrontes) in the Irohalene Member (Lagnaoui et al., 2012, Fig. 7A-B), it is obvious that most footprints described by Dutuit and Biron (1981)
8
ACCEPTED MANUSCRIPT represent extramorphological (substrate-related) variations of these ichnotaxa. This is demonstrated in the following.
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The overall shape of pes and manus imprints in Morphotype 1) resembles characteristic
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pentadactyl, but functionally tridactyl pes imprints with an associated small manus seen in the
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ichnogenus Parachirotherium and some similar forms. Parachirotherium was originally named by Kuhn (1958) based on material from the Middle Triassic (Late Ladinian) of the Germanic Basin. The ichnogenus has been identified also from the Upper Triassic Irohalene
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Member (Timezgadiouine Formation, T5, Carnian) of Ait Moussi locality in the Argana Basin
MA
(Lagnaoui et al., 2012; Fig. 7A). However, the fifth digit of the pes is mostly lacking in the new material from the Irohalene locality. Therefore, most pes imprints are tetradactyl, only with a short hallux, which is considered here as an extramorphological variation of the
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pentadactyl form. Only in rare cases a small oval pad is visible in a position where the fifth digit would be expected (CDUE 369; Fig. 4A). Because of the overall similarity with the
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ichnogenus Parachirotherium, but considering their incompleteness, we assign these footprints tentatively to Parachirotherium isp. Furthermore, some footprints from the
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Irohalene Member figured in Biron and Dutuit (1981, planche IIA–F, J–L) are re-assigned here to Parachirotherium isp.. This concerns tetradactyl-pentadactyl footprints described by these authors under Anomoepus moghrebensis and Quadridigitus dubius (Biron and Dutuit, 1981, planche II, F, L, K). Morphotype 2) when well preserved (CDUE 361; Figs. 5A) is similar in shape of the pes and manus imprints with those of the ichnogenus Atreipus (Olsen and Baird, 1986). The slender grallatorid pes imprint combined with a chirothere-like manus is typical of Atreipus that originally was described from the Upper Triassic of the Newark Supergroup (Olsen and Baird, 1986). Several grallatorid footprints fom the Irohalene Member (T5) of the Timezgadiouine Formation and from the Tadart Ouadou Member (T6) of the Bigoudine 9
ACCEPTED MANUSCRIPT Formation have been tentatively referred to the plexus Atreipus-Grallator, due to variation in the presence/absence of a manus trace (sensu Haubold and Klein, 2002), a larger form to
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Eubrontes (Olsen et al., 1998; Lucas et al., 2006; Lagnaoui et al., 2012; Fig. 7B). Because of
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their strong similarity with these footprints, we assign Morphotype 2 to Atreipus-Grallator.
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Also, the ichnotaxon Tridactylus machouensis erected by Biron and Dutuit (1981, planche II, A–E, J) is re-assigned here to Atreipus-Grallator based on the congruence in shape. Haubold
and
Klein
(2000,
2002) partly
along
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Parachirotherium–Atreipus–Grallator
discussed
transitional
single
morphs
trackways,
between
emphasizing
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ichnotaxonomical problems resulting from this observation. The Irohalene footprints again raise the same issue by the co-occurrence and transition of Parachirotherium- and AtreipusGrallator-like forms on the same surface or in the same unit.
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Moreover, tri-tetradactyl footprints with a posteriorly shifted reduced hallux from MiddleUpper Triassic deposits of Argentina (Melchor and De Valais, 2006; Marsicano et al. , 2007,
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2010) strongly resemble the footprints from Irohalene. Some of these have been assigned to Rigalites, an ichnogenus introduced by Huene (1931) based on trackways from the Los
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Rastros Formation (Ladinian–?Carnian) of Argentina. These are large tetradactyl pes imprints with an associated pentadactyl manus. Some imprints show a massive proximal region or rounded "heel" pad that could be interpreted as remnants of the reduced digit V. Moreover, Parachirotherium, Atreipus-Grallator, Rigalites and the footprints from the Irohalene Member show similar shape, proportions and digit orientation of the manus: 1) digits II, III and IV dominating in the imprint, 2), digits II and III longest and pointing forward, whereas digit IV is short and laterally spread. We note that the ichnogenera Rigalites and Parachirotherium as well as some similar ichnotaxa are presently under study and their relationship is re-examined by one of us (HK). From the Pekin Formation (Newark Supergroup, Carnian) of the Deep River Basin in North Carolina, USA, Olsen and Huber (1998) describe tetradactyl to pentadactyl, but 10
ACCEPTED MANUSCRIPT functionally tridactyl, pes imprints that clearly show a posteriorly shifted short hallux whereas digit V, if present, is reduced to an oval basal pad only and position far posterior to the rest of
these footprints
with the ichnogenus
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Huber (1998) mention the similarity of
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the pes. However, the material is incomplete and manus imprints are missing. Olsen and
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Parachirotherium. Nevertheless, there are some morphological differences between these tracks from North America, Rigalites from South America and the footprints described here from the Irohalene Member of the Argana Basin. Parachirotherium is distinct, especially in
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the development of the fifth pedal digit. However, this could be due to the different reduction
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of the latter in various lineages of dinosauromorphs during their radiation in the MiddleUpper Triassic (see below).
Morphotype 3 shows the typical morphology and diagnostic features of the ichnogenus
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Brachychirotherium by the broad overall shape of the pes imprint and by the short, broad digits with tiny claws, and the oval basal pad of digit V being in a postero-lateral position
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relative to the anterior digit group I–IV (Beurlen, 1950; Baird, 1957; Karl and Haubold, 1998; Lucas et al., 2010; Klein et al., 2015). It is assigned here tentatively to Brachychirotherium
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isp. A specific determination is not possible presently, because of the isolated material. It is the second record of the ichnogenus in the Upper Triassic of Morocco after the findings at the Sidi Said Maachou locality (Hminna et al., 2013). Morphotype 4 is represented by an isolated pes only. The digit proportions, with pedal digit IV being longest, and the inward curvature of distal ends that show sharp claw traces, are identical with pes imprints of the ichnotaxon Apatopus lineatus. Apatopus lineatus is also known from the Irohalene Member by a longer trackway (Lagnaoui et al., 2012). Therefore we assign Morphotype 4 and the isolated pes imprint here to Apatopus lineatus.
6. Trackmakers and biostratigraphic implications
11
ACCEPTED MANUSCRIPT Parachirotherium
and
Atreipus-Grallator
footprints
have
been
attributed
to
dinosauromorph trackmakers (Haubold and Klein, 2000, 2002; D'Orazi-Porchetti et al., 2008).
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In particular, Atreipus was alternatively considered to be of ornithischian affinity by some
IP
workers (Olsen and Baird, 1986). Interestingly, all these functionally tridactyl footprints with
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strongly reduced or absent pedal digits I and V have their first occurrence in the late Anisian and appear to be widely distributed and diversified from near the Ladinian-Carnian boundary (Klein and Lucas, 2010). This corresponds with the stratigraphic distribution of the known
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skeletal record of dinosauromorphs (Dzik, 2003; Langer et al., 2013). From the Irohalene
MA
Member (T5) of the Argana Basin, skeletal remains of the dinosauromorph Diodorus scytobrachion are known (Kammerer et al., 2011). The track record suggests that there was a strong radiation of dinosauromorphs during the late Middle Triassic-early Late Triassic time
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interval with different small to medium-sized forms that show a different degree of reduction of pedal digits I and V. The new discoveries from the Irohalene Member support this.
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For trackmakers of Brachychirotherium, aetosaurs (Heckert et al., 2010; Lucas and Heckert, 2011) as well as "rauisuchians" such as Postosuchus (Hminna et al., 2013; Klein et
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al., 2015) have been proposed. Both groups are known from T5 skeletal assemblages (Jalil, 1999; Jalil and Peyer, 2007). However, a definitive correlation with Brachychirotherium from T5 is presently not possible. The ichnogenus Apatopus has been widely accepted as a phytosaur track (Padian et al., 2010; Lagnaoui et al., 2012; Klein and Lucas, 2013). Rhynchosauroides is considered to be of lepidosauromorph and/or archosauromorph affinity. Biostratigraphically, the occurrence of the ichnogenera Brachychirotherium and Apatopus in the Irohalene assemblage indicates the Brachychirotherium faunachron that can be crosscorrelated with the Late Triassic (Carnian-Rhaetian) (Klein and Lucas, 2010).
7. Conclusions 12
ACCEPTED MANUSCRIPT New discoveries of tetrapod footprints from the Irohalene Member (T5) of the Timezgadiouine Formation are assigned to the ichnogenera Parachirotherium, Atreipus-
T
Grallator, Brachychirotherium and Apatopus based on overall-morphology and characteristic
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digit proportions. It is evident that the most common tetradactyl imprints with a short trace of
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the hallux are extramorphological variations or incomplete pes impressions of pentadactyl Parachirotherium. The latter is occasionally present at Irohalene and has been also described from other T5 localities (Lagnaoui et al., 2012). The variation in the number and shape of
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preserved digits in Parachirotherium is congruent with similar phenomena observed at the
MA
type locality of this ichnogenus in the Middle Triassic of the Germanic Basin of central Europe (Haubold and Klein, 2000, 2002).
Footprints of the Atreipus–Grallator plexus are also present. Together with Apatopus and
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the non-archosaur ichnotaxon Rhynchosauroides, the Irohalene ichnofauna documents a similarity in composition with assemblages from other T5 localities (Lagnaoui et al., 2012),
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North America (Olsen and Huber, 1998) and central Europe (Haubold and Klein, 2000, 2002). The presence of Brachychirotherium is the second record from North Africa and Morocco
AC
and the first from the Argana Basin (Hminna et al., 2013). Klein and Lucas (2010) proposed five tetrapod-footprint biochrons for the Triassic defined by the first appearance of distinct archosaur ichnotaxa and associated characteristic tracks. The footprint assemblages of the Irohalène Member (T5) in the Argana Basin can be attributed to the Late Triassic Brachychirotherium biochron (Klein and Lucas, 2010) based on the co-occurrence of Brachychirotherium, Atreipus–Grallator and Apatopus. The re-evaluation of the ichnotaxonomy of the Irohalene assemblage based on the new material suggests that footprints formerly described by Biron and Dutuit (1981) under Tridactylus machouensis, Anomoepus moghrebensis and Quadridigitus dubius are
13
ACCEPTED MANUSCRIPT extramorphological variations of Parachirotherium and Atreipus-Grallator and are therefore considered here as junior synonyms of the latter.
Atreipus-Grallator),
crocodylian-stem
(Brachychirotherium)
and
IP
(Parachirotherium,
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Trackmakers of the Irohalene footprints were most probably dinosauromorph
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phytosaurian (Apatopus) archosaurs as well as lepidosauromorph/archosauromorph groups (Rhynchosauroides).
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Klein, H., Voigt, S., Saber, H., Schneider, J.W., Hminna, A., Fischer, J., Lagnaoui, A., Brosig, A., 2011. First occurrence of a Middle Triassic tetrapod Ichnofauna from the
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Argana Basin (Western High Atlas, Morocco). Palaeogeogr. Palaeoclimatol. Palaeoecol. 307, 218–231.
Klein, H., Saber, H., Voigt, S., Schneider, J.W., Hmich, D., Hminna, A., 2009. An archosaurdominated footprint assemblage in Permo-Triassic red-beds of Morocco and the global record of early chirotherians. First Int. Congr. N. African Vertebr. Palaeontol. Abstr. 18. Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J.W., Hmich, D., 2010. Early Triassic Archosaur-dominated footprint assemblage from the Argana Basin (Western High Atlas, Morocco). Ichnos 17, 215–227. Kuhn, O., 1958. Die Fährten der vorzeitlichen Amphibien und Reptilien. Bamberg, Meisenbach, 64 p.
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ACCEPTED MANUSCRIPT Lagnaoui, A., 2014a. Late Paleozoic and Early Mesozoic continental ichnofaunas of Morocco (Sidi Kassem, Souss, Tiddas and Argana basins): Ichnotaxonomy, Paleoecology and
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Biostratigraphy. Unpublished PhD thesis, Faculty of Sciences, Chouaïb Doukkali
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University, Morocco, 215 pages.
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Lagnaoui, A., 2014b. Late Palaeozoic and Early Mesozoic Continental Ichnofossils from Morocco: Biostratigraphy, Palaeoecology end end-Permian Biotic Crisis evidence. Arabian J. Earth Sci. 1 (4) , 26–35.
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Lagnaoui, A., Klein, H., Voigt, S., Hminna, A., Saber, H., Schneider, J.W., Werneburg, R.,
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2012. Late Triassic tetrapod-dominated ichnoassemblages from the Argana Basin (Western High Atlas, Morocco). Ichnos 19, 238–253. Langer, M.C., Nesbitt, S.J., Bittencourt, J.S., Irmis, R.B., 2013. Non-dinosaurian
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Leonardi, G. (Ed.), 1987. Glossary and manual of tetrapod footprint palaeoichnology. Minist.
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Min. En. Depart. N. Prod. Mineral, Brasilia, 117 p. Lucas, S.G., Heckert, A.B., 2011. Late Triassic aetosaurs as the trackmaker of the tetrapod footprint ichnotaxon Brachychirotherium. Ichnos18 (4), 197–208. Lucas, S.G., Klein, H., Lockley, M.G., Spielmann, J., Gierlinski, G.D., Hunt, A.P., Tanner, L.H., 2006. Triassic-Jurassic stratigraphic distribution of the theropod footprint ichnogenus Eubrontes. New Mexico Mus. Nat. Hist. Sci. Bull. 37, 68–93. Lucas, S.G., Spielmann, J.A., Klein, H. and Lerner, A.J., 2010. Ichnology of the Upper Triassic Redonda Formation (Apachean) in east-central New Mexico. New Mexico Mus. Nat. Hist. Sci. Bull. 47, 75 p. Marsicano, C.A., Domnanovich, N.S., Mancuso, A.C., 2007. Dinosaur origins: evidence from the footprint Record. Historical Biology 19 (1), 83–91. 18
ACCEPTED MANUSCRIPT Marsicano, C.A., Mancuso, A.C., Palma, R.M., Krapovickas, V., 2010. Tetrapod tracks in a marginal lacustrine setting (Middle Triassic, Argentina): taphonomy and significance:
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Melchor, R.N., De Valais, S., 2006. A review of Triassic tetrapod track assemblages from
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Olsen, P.E., Baird, D., 1986. The ichnogenus Atreipus and its significance for Triassic Biostratigraphy. In: Padian, K. (Ed.), The beginning of the age of dinosaurs. Cambridge
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Olsen, P.E., Huber, P., 1998. The oldest Late Triassic footprint assemblage from North America (Pekin Formation, Deep River Basin, North Carolina, USA). Southeastern Geology 38, 77–90.
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Olsen, P.E., Smith, J.B., McDonald, N.G., 1998. Type material of the type species of the classic theropod footprint genera Eubrontes, Anchisauripus, and Grallator (Early
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Jurassic, Hartford and Deerfield Basins, Connecticut and Massachusetts, U. S. A.). J. Vertebr. Paleontol. 18, 586–601.
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Padian, K., Li, C., Pchelnikova, J., 2010. The trackmaker of Apatopus (Late Triassic, North America) implications for the evolution of archosaur stance and gait. Palaeontology 53, 175–189.
Saber, H., 1998. The Stephano-Permian of the western High Atlas: geological and geodynamic evolution (Morocco). Doctorat Es-Sciences (thèse d'Etat), Chouaïb Doukkali University, El Jadida, Morocco, 212 pp. Saber, H., El Wartiti, M., Hmich, D., Schneider, J.W., 2007. Tectonic evolution from the Hercynian shortening to the Triassic extension in the Paleozoic Western High Atlas (Morocco). J. Iberian Geol. 33 (1), 31–40. Tixeront, M., 1974. Carte géologique et minéralogique du Couloir d’Argana, 1/100 000. Ed. Serv. Géol. Maroc Notes Mémoires, 205. 19
ACCEPTED MANUSCRIPT Tixeront, M., 1973. Lithostratigraphie et minéralisation cuprifères et uranifères stratiformes syngénétiques et familières des formations détritiques permo-triasiques du Couloir
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d’Argana (Haut-Atlas occidental, Maroc). Notes Mém. Serv. Géol. Maroc 33 (249), 147–
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Voigt, S., Hminna, A., Saber, H., Schneider, J.W., Klein, H., 2010. Tetrapod footprints from the uppermost level of the Permian Ikakern Formation (Argana Basin, Western High Atlas, Morocco). J. African Earth Sci. 57, 470–478.
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Voigt, S., Schneider, J. W., Saber, H., Hminna, A., Lagnaoui, A., Klein, H., Brosig, A.,
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Fischer, J., 2011. Complex tetrapod burrows from Middle Triassic red beds of the Argana Basin (Western High Atlas, Morocco). Palaios 26 (9), 555–566.
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Figure captions
Fig. 1. Geographic and stratigraphic position of footprint localities. A–C. Position in Morocco
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and in the Argana Basin. D. Geological map with Irohalene localities indicated by star (after, Tixeront, 1974). E. Stratigraphic section with Paleozoic-Mesozoic succession in
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the Argana Basin and the footprint horizon indicated by star. Fig. 2. Stratigraphic section at footprint locality CDUE 100 with the distribution of body- and ichnofossils and sedimentary structures. Fig. 3. Two tetradactyl pes imprints (CDUE 370) from CDUE locality 101 preserved as concave
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Parachirotherium isp. with slender digit traces. A. Photograph showing overview of surface with imprints (c, d) and ripple marks. B. Sketches of pes imprints (c, d corresponding to footprints demarcated in A). C. Photograph with detail of imprint c. Scale bar 5 cm.
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ACCEPTED MANUSCRIPT Fig. 4. Tridactyl-pentadactyl archosaur footprints Parachirotherium isp. from Irohalene localities as photographs and sketches; all preserved as convex hyporeliefs. A–A'. Large
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pentadactyl pes imprint (CDUE 369) from CDUE locality 100 with broad digit traces. B–
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B'. Tetradactyl pes imprint and associated manus imprint CDUE 371 from CDUE locality
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101. C–C'. Tetradactyl pes imprint CDUE 372 from CDUE locality 101. D–D'. Tetradactyl pes imprint CDUE 374 from CDUE locality 101. E–E'. Tridactyl pes imprint
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and associated tridactyl manus imprint CDUE 363 from CDUE locality 100. Fig. 5. Archosaur footprints from Irohalene locality CDUE 100 as photographs and sketches;
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all preserved as convex hyporeliefs. A–A'. CDUE 361, two tridactyl pes imprints; one with associated tridactyl manus imprint (center); with tridactyl small Rhynchosauroides
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tridactyl manus imprint Brachychirotherium isp. B photographed under artificial light.
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Fig. 6. Archosaur footprints from Irohalene localities preserved as convex hyporeliefs. A–A'. Fragmentary pes and manus imprints Brachychirotherium isp. (CDUE 364) from CDUE locality 100. B–B'. pentadactyl pes imprint Apatopus lineatus CDUE 367 from CDUE
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locality 100. C–C'. Pentadactyl chirotheriid pes imprint CDUE 362 from CDUE locality 100. D–D'. Fragmentary pes-manus set (uncollected). C photographed under artificial light. Fig. 7. Photographs and sketches of archosaur footprints preserved as concave epireliefs from the Upper Triassic of the Timezgadiouine Formation described by Lagnaoui et al. (2012) for comparison. A–A’. Parachirotherium cf. Parachirotherium postchirotherioides Rehnelt, 1950. Left pes-manus set, CDUE 325, from CDUE locality 38 (Irohalene Member (T5). B–B’. Atreipus – Grallator. Left pes-manus set, CDUE 350, from CDUE locality 41 (Tadart Ouadou Member (T6)). All photographed under artificial light.
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ACCEPTED MANUSCRIPT Highlights
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New discoveries of Late Triassic tetrapod footprints from Morocco. Ichnotaxonomic re-evaluation of footprints described earlier from the Late Triassic deposits of Morocco. The second record of the ichnogenus Brachychirotherium in North Africa and Morocco.
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