Permian tetrapod footprints from the Spanish Pyrenees

Palaeogeography, Palaeoclimatology, Palaeoecology 417 (2015) 112–120

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Permian tetrapod footprints from the Spanish Pyrenees Sebastian Voigt a,⁎, Hartmut Haubold b a b

Urweltmuseum GEOSKOP, Burg Lichtenberg (Pfalz), Burgstraße 19, D-66871 Thallichtenberg, Germany Institut für Geowissenschaften, Martin-Luther-Universität Halle-Wittenberg, Von-Seckendorff-Platz 3, D-06120 Halle (Saale), Germany

a r t i c l e

i n f o

Article history: Received 28 July 2014 Received in revised form 15 October 2014 Accepted 28 October 2014 Available online 4 November 2014 Keywords: Vertebrate tracks Late Paleozoic Alluvial plain Red-beds Iberian Peninsula

a b s t r a c t Paleozoic tetrapod footprints are a common and well-known phenomenon in almost all large European countries except for Spain. Here we report on hitherto unpublished vertebrate tracks from Permian red-beds of the southcentral Pyrenees that with regard to their relative abundance, diversity and quality of preservation are suitable to fill this gap of knowledge. The described tracks come from two localities in muddy to fine-grained, sandy, alluvial plain deposits in the lower third of the Peranera Formation of the Erill-Castell Basin near Les Iglésies, northern Catalonia. The tracks can be assigned to five ichnogenera, i.e., Batrachichnus Woodworth, 1900, Limnopus Marsh, 1894, Varanopus Moodie, 1929, Hyloidichnus Gilmore, 1927, and Dromopus Marsh, 1894, that we interpret as footprints of temnospondyls, captorhinomorphs, and araeoscelids or similarly sized sauropsids with a lacertoid foot pattern. This ichnofossil assemblage is most similar to ichnofaunas from the Hermit Formation of the Grand Canyon, Arizona, the upper Abo and Robledo Mountains formations of New Mexico, and the main trace fossil site of the Tiddas Basin, Morocco, suggesting a late Early Permian (Artinskian) age for this stratigraphic level of the Peranera Formation. Considering the relative abundance and diversity of captorhinomorph footprints, the new Spanish tracefossil localities may cover the onset of the Early Permian radiation of non-diapsid eureptiles. The thick Late Paleozoic red-bed successions of the south-central Pyrenees have the potential to also bear footprints of otherwise unknown early therapsids, so systematic fossil prospecting of this area is strongly recommended. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Vertebrate tracks are a valuable archive for the reconstruction of tetrapod evolution and for biostratigraphic analyses of continental deposits (Haubold, 1971, 1984, 1996, 2000; Clack, 1997; Lockley, 1998; Voigt et al., 2007; Klein and Lucas, 2010). The significance of tetrapod ichnology depends on the quantity and quality of data that are available for a certain geological period. First and foremost, this paper aims to extend the hitherto limited knowledge of Late Paleozoic vertebrate ichnofaunas from Spain. Tetrapod footprints from Late Paleozoic rocks of Spain have been known for less than 30 years. Fossil tracks were reported from latest Carboniferous deposits of the Puertollano Basin in central Spain (Soler-Gijón and Moratalla, 2001), the late Early Permian Sagra Formation of the Cantabrian Mountains in northern Spain (Gand et al., 1997; Demathieu et al., 2008), as well as from red beds of supposed Late Permian age in the Pyrenees of eastern Spain (Robles and Llompart, 1987). Permian vertebrate tracks from the Spanish Pyrenees gained increased attention recently, because of the discovery of a few more specimens (Fortuny et al., 2010, 2011). The material described by ⁎ Corresponding author. Tel.: +49 6381 993451; fax: +49 6381 993452. E-mail addresses: [email protected] (S. Voigt), [email protected] (H. Haubold).

http://dx.doi.org/10.1016/j.palaeo.2014.10.038 0031-0182/© 2014 Elsevier B.V. All rights reserved.

Fortuny and colleagues comes from the Palanca de Noves site in the Ribera d'Urgellent area south of La Seu d'Urgell, Lleida Province, Catalonia, a place which is geographically and stratigraphically close to the track locality of Robles and Llompart (1987) (Fig. 1). In 1998, the second author of this contribution (H.H.) and his wife Cornelia started exploration of the Southern Pyrenees for Permian tetrapod footprints by using regional geological maps (Mey et al., 1968; Nagtegaal, 1969). Investigation commenced in potentially footprintbearing Late Paleozoic red-beds south of La Seu d'Urgell and then covered all outcrops of related strata up to the Sierra de Peranera near El Pont de Suert, i.e. for a distance of almost 70 km. The discovery of unambiguous tetrapod footprints was finally made in red-beds of the Permian Peranera Formation near Les Iglésies about 10 km east of El Pont de Suert (Fig. 1). While driving on an unpaved road NE of La Mola d'Amunt footprints were recognized on exposed surfaces of vertical red-beds that correspond to a section measured by Nagtegaal (1969: section 6, sheet IV) more than three decades before. Since the discoveries, the area north of Les Iglésies has proven to be locally rich in Permian tetrapod footprints. The outcrops were visited and recollected by the discoverers several times between 1998 and 2005 as well as investigated during a joint trip of both authors in 2001. These activities resulted in a collection of more than 30 representative specimens with fossils from the Peranera Formation, mainly tetrapod footprints but also including plant remains, invertebrate traces,

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Fig. 1. Geological framework of Permian tetrapod footprints from the Peranera Formation: A–B, Geographic position and simplified geological map of the wider study area in Spain; C, simplified geology in the vicinity of Las Iglésies and UGKU localities 34 and 80; D, generalized lithostratigraphy of Paleozoic–Mesozoic rocks between El Pont de Suert and Sort; E, upright muddy to fine-grained sandy red beds of the Peranera Formation near UGKU locality 34. Geological maps and section after Mey et al. (1968), Nagtegaal (1969), Saura and Teixell (2006).

and an arthropod body impression. Description of the material, however, has been postponed basically due to the ambiguous ichnotaxonomic assignation of the dominant captorhinomorph footprints. Much progress has been made in the understanding of captorhinomorph tracks during the last years triggered by numerous related finds in Early Permian deposits of the United States, Morocco, and Italy (Haubold and Lucas, 2001, 2003; Lucas and Spielmann, 2009; Voigt et al., 2010, 2011a; Marchetti, 2014; Marchetti et al., 2014). In view of this new situation it seems appropriate to reconsider the taxonomic composition of the tetrapod ichnofauna of the Peranera Formation based on our observations and collections. 2. Material and methods This paper is based on 18 specimens with tetrapod footprints from the Peranera Formation in the south-central Pyrenees, Spain, collected in 1998 to 2001. The material is housed at the Urweltmuseum GEOSKOP, Burg Lichtenberg near Kusel, Rheinland-Pfalz, Germany (UGKU; POLLICHIA geoscience collections) and labeled as UGKU 1826, 1923–1925, 1927, 1931, 1933–1939, 1964–1967, and 1977. Most of the UGKU tetrapod footprint specimens from the Peranera Formation show more than one track. Trampled surfaces with several dozens of imprints or mass occurrences of tetrapod scratch marks and swimming traces are common among the collected material and have also been observed in place near to the collecting sites. True trackways, i.e. sequences of at least three consecutive manus–pes imprint couples, however, could not be recorded. The described tracks are preserved in grayish-red to reddish-brown mudstone and may be associated with rain drop impressions, desiccation cracks and microbially induced sedimentary structures. Material was recovered at two distinct sites north of Les Iglésies, Lleida Province,

Catalonia (Fig. 1): (1) UGKU locality 34 (UTM 31T, WGS 84, E324813 N4696094) which is a road cut in the valley of the Riu Mañanet north of La Mola d'Amunt; and (2) UGKU locality 80 (UTM 31T, WGS 84, E325709 N4695923) which is a road cut in the valley of the Riu Valiri northeast of La Mola d'Amunt. With the exception of one specimen (UGKU 1826) all of the UGKU footprints from the Peranera Formation come from UGKU locality 34. The UGKU collection exclusively contains floating material found on spoil piles from road construction. More Permian footprints were observed along the road between La Mola d'Amunt and Sentis but have been left in place. For comparison purposes, digital photographs were taken of each tetrapod track specimen from the Peranera Formation. The best preserved tracks were outlined on transparency film in order to quantify the parameters of the imprint morphology following standard procedural practice in tetrapod ichnology (e.g., Haubold, 1971; Leonardi, 1987; Voigt, 2005). Identification of the footprints was performed according to an ichnotaxonomic concept that is entirely based on anatomically controlled characters of the imprint morphology and trackway pattern (Peabody, 1948; Haubold, 1996). 3. Geological framework All of the described ichnofossils come from the south-central Pyrenees, Spain, where the distribution of Late Paleozoic rocks gives evidence of several small, isolated continental Variscan basins (Mey et al., 1968; Nagtegaal, 1969; Gisbert, 1984; Muñoz, 2002). UGKU localities 34 and 80 are situated in the Erill-Castell Basin, which is an approximately 15 km long, E–W to ESE–WNW striking strip of Late Carboniferous and Permian volcanosedimentary deposits between El Pont de Suert in the west and Sort to the east (Fig. 1; Saura and Teixell, 2006). Pereira et al. (2014) stated that the centers of deposition of the Erill-Castell

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Basin and the easterly adjoining Estac Basin belong to the same structural basin and therefore introduced the term Erill-Castell–Estac Basin. The Erill-Castell Basin was a half-graben with steep southern and shallowly inclined northern flanks. It contains a more than 1000 m thick succession of Late Paleozoic rocks that unconformably rest on Variscan deformed Cambrian to Early Carboniferous basement and that are unconformably overlain by Triassic red beds. The Late Paleozoic succession comprises volcanic and sedimentary rocks of latest Carboniferous (Stephanian) and Permian age divided into four formations (Mey et al., 1968; Nagtegaal, 1969). These are from base to top (Speksnijder, 1985; Saura and Teixell, 2006; Fig. 1): (1) Aguiró Formation, basal breccias, up to 350 m thick; (2) Erill-Castell Formation, volcanic and volcaniclastic rocks, 200 to 400 m thick; (3) Malpàs Formation, coal beds interbedded with shales and graywackes, up to 550 m thick; and (4) Peranera Formation, red shales and interbedded sandstone, conglomerate and lacustrine limestone, 950 to 1500 m thick. The Aguiró, Erill-Castell and Malpàs formations are considered to be of Carboniferous age based on plant fossils (Nagtegaal, 1969). The precise age of the red-beds of the Peranera Formation is not known; they are generally regarded to be of Permian age, as they occur between sediments of proven latest Carboniferous (Stephanian) and Early Triassic age (Mey et al., 1968; Nagtegaal, 1969; Hartevelt, 1970; Zwart, 1979; Speksnijder, 1985). Detailed sedimentologic and petrologic studies of the post-Hercynian succession of the southern Pyrenees were first provided by Dutch geologists of the University of Leiden as a result of geological mapping of the area at the scale of 1:50,000 during the 1960s (Mey, 1967, 1968; Mey et al., 1968; Nagtegaal, 1969; Hartevelt, 1970; Zwart, 1979) and continued by Spanish and other workers (Gisbert, 1981; Bixel and Lucas, 1983; Gisbert, 1983; Gisbert et al., 1985; Speksnijder, 1985; Martí, 1986). All Paleozoic tetrapod footprints that were hitherto known from the southern Pyrenees come from red-beds of the Peranera Formation. Specimens published by Robles and Llompart (1987) and Fortuny et al. (2010) from the Palanca de Noves site were found in the Peranera Formation south of La Seu d'Urgell and are referred to the La Seu Basin sensu Speksnijder (1985), which seems to be identical with the Gramós Basin of Saura and Teixell (2006) and part of the El Cadí Basin sensu Pereira et al. (2014). Saura and Teixell (2006) estimate the maximum thickness of the Peranera Formation at 1500 m in contrast to 950 m in the Erill-Castell Basin. Nagtegaal (1969) gives for the latter area a maximum thickness of the Peranera Formation of 700 m. Even if the stratigraphic position of the Palanca de Noves site is not exactly known, it is quite possible that there are differences in the absolute age of the footprints from the La Seu/Gramós and Erill-Castell basins. UGKU localities 34 and 80 are situated about 220–230 m above the base of the Peranera Formation north of Les Iglésies according to the geological map and detailed stratigraphic section of this area published by Nagtegaal (1969) (Fig. 1). The Peranera Formation north of Les Iglésies is composed of interbedded conglomeratic sandstone (24%), mudstone (75%), and volcanic ash (1%) interpreted to represent distal alluvial plain deposits with a high percentage of eolian dust (Nagtegaal, 1969). Locally thick horizons of pedogenic calcite concretions, desiccation cracks, and raindrop impressions support the idea that deposition took place under intermittent wet and dry conditions. Though the fossils from UGKU localities 34 and 80 were not found in place, its combined lithological and paleontological features point to an origin in what Nagtegaal (1969) termed ‘puddle deposits’, but might be more precisely called channel cut-offs. These are 1–40 cm thick, laminated, fine-grained strata of restricted lateral extent containing desiccation cracks, raindrop impressions, microbially induced sedimentary structures, root traces and walchian conifer remains. The common presence of amphibian tracks, tetrapod scratches and swimming marks at UGKU localities 34 and 80 is in good agreement with an origin of the traces in association with water holes in the beds of dried-up streams.

4. Paleoichnology UGKU localities 34 and 80 yield fossil tetrapod footprints that can be attributed to five characteristic Permian ichnogenera. The following description refers to the best preserved track material from the Peranera Formation at UGKU. Considering the low number of specimens, the incomplete preservation of most tracks and the lack of true trackways, we prefer to keep the majority of footprints in open nomenclature at the ichnospecies level. 4.1. Batrachichnus Woodworth, 1900 (Figs. 2A–B, 3A) Type ichnospecies: Batrachichnus plainvillensis Woodworth, 1900, but this is considered to be a younger subjective synonym of Batrachichnus salamandroides (Geinitz, 1861). Referred specimen: UGKU 1923, incomplete trackway of five manus– pes sets preserved in convex hyporelief; UGKU 1934, part and counterpart of three longer discontinuously preserved trackways. Description: Tracks of quadrupedal tetrapods with pentadactyl pes imprints, tetradactyl manus imprints, and always distantly rounded digit tips. Pes imprints up to 10 mm in length, slightly larger than the manus imprint. Pes imprints semiplantigrade to digitigrade; digit proportions about I b II ~ V b III b IV. Manus imprints plantigrade, about as long as wide, digit length increases from I to III, IV as long as II, III slightly longer than the total imprint length; palm impression with a distinct proximomedial pad. Trackway pattern with alternating coupled manus–pes sets; manus and pes imprints are slightly inwardly rotated. Discussion: The described footprints are characterized by small size and the tetradactyl manus matching the diagnostic features of Batrachichnus Woodworth, 1900. This ichnotaxon is well known from many localities with Carboniferous and Permian tetrapod footprints in North America, Europe and Africa (Haubold, 1970, 1996; Haubold and Sarjeant, 1973; Gand, 1988; Haubold et al., 1995; Lucas et al., 2005; Voigt, 2005, 2012; Voigt et al., 2011a, 2011b; Marchetti et al., 2013). B. salamandroides from the Early Permian of the Czech Republic is the first available ichnospecies of Batrachichnus (Geinitz, 1861; Haubold, 1996). Based on anatomically controlled features of the imprint morphology and trackway pattern it is also the only valid species of the ichnogenus (Voigt, 2005). The discussed tracks may belong to B. salamandroides as well. We, however, are careful with this assignment considering the poorly preserved pes imprints of the Peranera specimens (Fig. 2A–B). Among the studied material there are several slabs with small-sized scratch marks or swimming traces (Fig. 3A). As this kind of trace is often associated with Batrachichnus tracks (Haubold, 1970, 1996; Haubold et al., 1995; Voigt, 2005; Voigt et al., 2011a; Petti et al., 2014), it is reasonable that they have been made by the same kind of animals as the walking traces. Batrachichnus is consensually considered to be the tracks of small to medium-sized temnospondyls (Haubold, 1971, 1996, 2000; Gand, 1988; Lucas et al., 2005; Voigt, 2005; Voigt et al., 2011a). 4.2. Limnopus Marsh, 1894 (Figs. 2C–D, 3B–D) Type ichnospecies: Limnopus vagus Marsh, 1894, but Limnopus heterodactylus (King, 1845) is most likely synonymous with L. vagus (Lucas and Dalman, 2013). Referred specimens: UGKU 1939, manus imprint and tips of two digits of the coupled pes imprint preserved in convex hyporelief; UGKU 1964, manus–pes couple preserved in concave epirelief. Description: Tracks of quadrupedal tetrapods with plantigrade to semiplantigrade imprints up to 40 mm in length; pes pentadactyl, manus tetradactyl, digits straight with blunt and slightly enlarged tips. Pes imprint is almost one fifth wider than long, length of digits increases from I to IV, V about as long as II; sole impression shallow and indistinct. Manus imprint slightly wider than long, digit proportions I b II b III ~ IV; palm impression missing except for a distinct medioproximal

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Fig. 2. Batrachichnus Woodworth, 1900 and Limnopus Marsh, 1894 from the Peranera Formation. Material: A, UGKU 1923; B, UGKU 1934; C, UGKU 1939; D, UGKU 1964. Tracks are preserved in convex hyporelief (A–C) and concave epirelief (D). Scale bars equal 1 cm.

pad opposite to digit I. Pes imprint positioned behind or partially overstepping the manus imprint within pes–manus couples. Manus imprint rotated inward relative to the pes imprint. Discussion: The described tracks are most similar to Batrachichnus regarding the number of digits and overall shape. There are only two differences between both ichnogenera, i.e., imprint size and the digit proportions of the manus imprint. UGKU 1939 and UGKU 1964 show imprints that are about four times larger than Batrachichnus from

UGKU locality 34 and the fourth digit of the manus imprint is significantly longer than the second one. All these features are in agreement with the characteristics of the ichnogenus Limnopus (Voigt, 2005). Because of the observed difference in manual digit proportions and the remarkable differences in track size we suggest a separation of Batrachichnus and Limnopus from the Peranera Formation. However, it should be stated that the ichnotaxonomic separation of Batrachichnus and Limnopus has been a long lasting and not yet readily resolved

Fig. 3. Fossil traces from the Peranera Formation which are the result of temnospondyl tetrapods paddling in shallow water. Material: A, C–D, UGKU 1933, preserved in concave epirelief (A, D) and convex hyporelief (C); B, UGKU 1939, preserved in convex hyporelief. Scale bars equal 1 cm.

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issue (Haubold, 1996; Tucker and Smith, 2004; Voigt, 2005; Voigt et al., 2011a, 2011b). Extensive surfaces with large tetrapod scratch and swimming marks are common, in particular at UGKU locality 34 (Fig. 3B–D), and have only been found associated with Limnopus tracks, suggesting that all of these traces were produced by the same kind of animals. Estimated from digit tip scratch/swimming marks, the trackmaker's autopodes could reach more than 10 cm in width (Fig. 3D). This is not unusual considering unpublished material of Limnopus from the Pennsylvanian– Permian Washington Formation at Marietta College, Ohio, with tracks that measure more than 20 cm in length (personal observation: SV, 2009). The name Characichnos Whyte and Romano, 2001 has been suggested for tetrapod swimming traces, but this is meaningless in the light of a trackmaker-based ichnotaxonomic concept (Peabody, 1948; Haubold, 1996) as it is preferred here. The first named ichnospecies of Limnopus is L. heterodactylus (King, 1845) from Pennsylvanian strata of Westmoreland County in western Pennsylvania (Baird, 1952; Haubold, 1970, 1996; Voigt, 2005; Lucas and Dalman, 2013). Any discussion on ichnospecies assignment of Limnopus, however, is misguided until the ichnotaxonomic relationship between Batrachichnus and Limnopus has been resolved. Limnopus is considered to be the tracks of temnospondyls that reached considerable body size in adult individuals (Haubold, 1971; Gand, 1988; Haubold, 2000; Tucker and Smith, 2004; Van Allen et al., 2005; Voigt, 2005; Gand and Durand, 2006). 4.3. Varanopus Moodie, 1929 (Figs. 4, 5) Type ichnospecies: Varanopus curvidactylus Moodie, 1929, but this is considered to be a younger subjective synonym of Varanopus microdactylus (Pabst, 1896). Referred specimens: UGKU 1931, five tracks of one trackway preserved in convex hyporelief; UGKU 1936, two manus–pes couples of one trackway preserved by print and partial counterprint; UGKU 1977, manus–pes couple preserved in convex hyporelief.

Fig. 4. Varanopus cf. microdactylus (Pabst, 1896) from the Peranera Formation. Material: UGKU 1936, two manus–pes imprint couples of the same trackway preserved in concave epirelief. Scale bars equal 1 cm.

Fig. 5. Varanopus cf. hermitanus (Gilmore, 1927) from the Peranera Formation. Material: UGKU 1931, manus–pes imprint couple preserved in convex hyporelief. Scale bars equal 1 cm.

Description: Tracks of quadrupedal tetrapods with pentadactyl, semiplantigrade imprints up to 3 cm in length. Pes imprint about one fifth longer than the manus imprint; digits straight to slightly inwardly curved in distal parts, with acute claw marks. Digit length increases from I to IV in both imprints; digit V of the pes imprint either as long as III or II, digit of the manus imprint ranges in length between I and II. Manus and pes imprints are as long as wide or slightly wider than long. If preserved, sole and palm impression short with concave proximal margin. Pes imprinted behind or partially overstepping the manus imprint in pes–manus couples. Manus imprint rotated inward with respect to the pes imprint. Discussion: The described tracks show all characteristics of the ichnogenus Varanopus Moodie, 1929. Tracks of this ichnogenus are well-known from Early Permian deposits of Germany (Müller, 1954; Haubold, 1998), France (Gand, 1988), the United States (Haubold and Lucas, 2001, 2003; Lucas and Spielmann, 2009), Canada (Van Allen et al., 2005), and Italy (Nicosia et al., 2000; Marchetti et al., 2013; Marchetti, 2014). Varanopus is most similar to tracks assigned to Notalcerta Butts, 1891, Hyloidichnus Gilmore, 1927, Erpetopus Moodie, 1929 and Robledopus Voigt et al. (2013), but significant differential characters between these ichnotaxa were recently recorded in detail (Voigt et al., 2013). Varanopus from the Peranera Formation rather forces to focus on ichnospecific differences within the ichnogenus. Haubold (2000) considered two ichnospecies to be valid, V. microdactylus (Pabst, 1896) and V. curvidactylus Moodie, 1929. Apart from minor differences in the trackway pattern, both ichnospecies seem to be the same (Voigt, 2005). Therefore, we consider V. curvidactylus a junior synonym of V. microdactylus. A number of Varanopus tracks from the Hermit and Arroyo de Alamillo formations of the United States (Gilmore, 1927; Lucas and Spielmann, 2009), the Rabejac Formation of France (Gand, 1988), the Collio and Pizzo del Diavolo formations of Italy (Nicosia et al., 2000; Marchetti et al., 2013; Marchetti, 2014) and the Çakraz Formation of Turkey (Gand et al., 2011), however, differ from V. microdactylus by a relatively shorter fifth digit of the pes imprint. The same observation was independently made for Varanopus from the Pizzo del Diavolo Formation of the Southern Alps and, consequently, application of a separate ichnospecies claimed (Marchetti et al., 2013). The ichnogenus Varanopus was introduced by Moodie (1929) for tracks from the Choza Formation in Texas, but the first available ichnospecific name for this type of tracks is Varanopus (Hylopus) hermitanus (Gilmore, 1927) referring to tracks from the Hermit Formation of the Grand Canyon, Arizona. Because the type material of V. (H.) hermitanus is poorly preserved, the use of this ichnotaxon should be considered tentatively until a comprehensive analysis of all available tracks of this ichnospecies will be conducted. V. microdactylus and V. (H.) hermitanus are Varanopus tracks that only differ in the relative length of the fifth digit of the pes imprint: this fifth digit is about as

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long as digit III of the pes imprint in V. microdactylus and about as long as digit II in V. (H.) hermitanus. UGKU locality 34 of the Peranera Formation is the first place where these two Varanopus ichnospecies occur side by side as UGKU 1936 (Fig. 4) and UGKU 1977 can be assigned to V. microdactylus and UGKU 1931 (Fig. 5) to V. (H.) hermitanus based on the digit proportions of the pes imprint. Varanopus is principally accepted to be the track of basal captorhinomorphs (Haubold, 1971, 1998, 2000; Gand, 1988; Haubold and Lucas, 2001, 2003; Santi and Krieger, 2001; Voigt, 2005, 2012; Gand and Durand, 2006; Voigt et al., 2009, 2013). 4.4. Hyloidichnus Gilmore, 1927 (Fig. 6) Type ichnospecies: Hyloidichnus bifurcatus Gilmore, 1927. Referred specimens: UGKU 1927, isolated pes imprint preserved in convex hyporelief; UGKU 1965, isolated incomplete manus imprint preserved by part and counterpart. The following specimens are compared to the ichnogenus: UGKU 1826, mass occurrence of randomly arranged tracks preserved in convex hyporelief; UGKU 1924, 1926, several tracks preserved in concave epirelief; UGKU 1934, several tracks, preserved by part and partial counterpart; UGKU 1935, 1937 and 1938, several tracks, preserved in convex hyporelief. Description: Tracks of quadrupedal tetrapods with pentadactyl, digitigrade imprints up to 45 mm in length. Manus and pes imprints are similar in size and digit proportions. Both imprints are about as long as wide and show relatively long, straight and slender digits that increase in size from I to IV. Digit V is about as long as I in manus and pes imprints. Digits have slightly enlarged, claw mark like tapering digit tips which are curved inward in the first four digits, but outward

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rotated in V. Sole or palm impressions are not preserved. As the referred material includes only isolated imprints or track mass occurrences on trampled surfaces there are no data available on the trackway pattern. Discussion: With respect to the shape and proportions of the digits, UGKU 1927 (Fig. 6A) and UGKU 1965 correspond well with tracks of Hyloidichnus Gilmore, 1927. Hyloidichnus is similar to Varanopus Moodie, 1929; both ichnotaxa mainly differ in the relative length of the fifth digit of the pes imprint and by the size range of the imprints (Voigt et al., 2009, 2010, 2013; Hminna et al., 2012; Marchetti et al., 2013). Digit V of the pes imprint is about the length of digit I in Hyloidichnus, whereas it is as long as II or III in Varanopus. Maximum recorded pes imprint length of Varanopus is 45 mm (Voigt, 2005) in contrast to more than 100 mm in Hyloidichnus (Gand, 1988; Voigt et al., 2009, 2010). Varanopus and Hyloidichnus from UGKU locality 34 are of similar size but clearly separated by the digit proportions of the pes imprint. Several specimens among the studied material (UGKU 1826, 1924, 1926, 1934, 1935, 1937, and 1938; Fig. 6B, C) show pedal tracks that all lack an impression of the fifth digit. These tracks cannot be readily assigned to one or the other ichnogenus. Despite incomplete preservation, we compare the material with Hyloidichnus because of the remarkably straight digit impressions of these tracks. This is a consistent feature seen in many occurrences of Hyloidichnus such as from the Hermit Formation of the United States (Gilmore, 1927), the Rabejac Formation of France (Gand, 1988) or the Ikakern Formation of Morocco (Voigt et al., 2010). If this conclusion is correct, Hyloidichnus is the dominant ichnotaxon at UGKU locality 34. An ichnospecific assignment is avoided due to the relatively poor preservation of the material. Tracks of Hyloidichnus and Varanopus are usually referred to captorhinids (Haubold, 1971; Gand, 1988; Haubold and Lucas, 2001, 2003; Voigt,

Fig. 6. Hyloidichnus Gilmore, 1927 (A) from the Peranera Formation and incomplete tracks (B, C) from the same strata compared to Hyloidichnus Gilmore, 1927. Material: A, UGKU 1927, pes imprint preserved in convex hyporelief; B, UGKU 1826, mass occurrence of small tracks preserved in convex hyporelief; C, UGKU 1924, manus–pes imprint couple preserved in concave epirelief. Scale bars equal 1 cm.

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2005; Gand and Durand, 2006). More specifically, Voigt et al. (2009, 2010) argued for a track–trackmaker relationship of Hyloidichnus and moradisaurine captorhinids. 4.5. Dromopus Marsh, 1894 (Fig. 7) Type ichnospecies: Dromopus agilis Marsh, 1894, but this is considered to be a younger subjective synonym of Dromopus lacertoides (Geinitz, 1861). Referred specimen: UGKU 1925, three shallow imprints of two trackways preserved in convex hyporelief. Description: Digitigrade footprints of quadrupedal, pentadactyl tetrapods with long and slender digits. Imprints are small, 15–20 mm in length, and usually exhibit digits II to IV or III and IV only. Impressions of outer digits may be present but are faint. Middle digits increase in length from II to IV; IV significantly longer than III and moderately to strongly curved inwardly. Digit V is positioned proximally to the digits II–IV, longer than II, but shorter than III, rather straight and pointed outwardly. Manus and pes imprints are similar and sometimes indiscernible in isolated tracks. Sole impressions are not preserved. Discussion: The discussed tracks are attributed to Dromopus Marsh, 1894 based on their long, slender, and curved digit imprints. They are different from Erpetopus Moodie, 1929 and Varanopus Moodie, 1929 by a relatively long fourth digit impression and large angle of divarication between digit III and IV. Apart from the type ichnospecies D. lacertoides, there are more than a dozen ichnospecific names available in the literature for Dromopus-like tracks from Late Paleozoic deposits. Whether any of them are based on anatomically controlled characters is still under question (Gand, 1988; Haubold, 1996, 2000; Haubold and Lucas, 2001, 2003; Voigt, 2005; Marchetti, 2014). Incompletely preserved tracks such as the described material do not contribute to this issue. Dromopus is the most common and most widespread Late Paleozoic tetrapod ichnotaxon and usually referred to small and mediumsized sauropsids with lacertoid autopod structures, i.e., araeoscelids and bolosaurids in particular (Haubold, 1971, 1996, 2000; Gand, 1988; Haubold and Lucas, 2001, 2003; Voigt, 2005, 2012; Gand and Durand, 2006; Lucas, 2007; Hminna et al., 2012). 5. Biostratigraphic significance and global context The red beds of the Peranera Formation at UGKU localities 34 and 80 yield a typical Permian tetrapod ichnofossil assemblage. While Batrachichnus, Limnopus and Dromopus occur in both Carboniferous and Permian strata, Varanopus and Hyloidichnus are hitherto known from Permian successions only (Geinitz, 1861; Marsh, 1894; Woodworth,

1900; Pabst, 1908; Baird, 1952; Haubold, 1970, 2000; Gand, 1988; Haubold et al., 1995; Nicosia et al., 2000; Santi and Krieger, 2001; Voigt, 2005; Gand and Durand, 2006; Voigt et al., 2009, 2010, 2011a, 2012; Marchetti et al., 2013; Marchetti, 2014). Varanopus has mainly been reported from Early Permian strata (Haubold, 1971; Gand, 1988; Haubold and Lucas, 2001, 2003; Lucas et al., 2001; Van Allen et al., 2005; Voigt, 2005; Marchetti, 2014), suggesting that the footprint level of the Peranera Formation at UGKU locality 34 is of the same age. The first appearance of Hyloidichnus is uncertain, but most likely dates to the late Early Permian (Haubold, 2000; Gand and Durand, 2006; Voigt et al., 2009, 2011a; Fig. 8). Regarding the taxonomic composition and relative abundance of individual taxa, the most similar ichnofaunas to UGKU locality 34 are all considered to be of late Early Permian age: (1) Hermit Formation, Arizona, USA (Gilmore, 1927, 1928; Haubold et al., 1995; Lucas, 2007); (2) the upper third of the Abo Formation and the Robledo Mountains Formation, New Mexico, USA (Haubold et al., 1995; Lucas et al., 1995, 2004, 2012; Voigt et al., 2013); and (3) the main footprint level of the Tiddas Basin, Morocco (Voigt et al., 2011a). All of these occurrences are characterized by relatively abundant and diverse captorhinomorph footprints, mainly represented by Varanopus and Hyloidichnus. Another common feature is the lack of Erpetopus, which occurs in slightly younger strata such as the Choza Formation, Texas, USA (Moodie, 1929; Haubold and Lucas, 2001, 2003), the boundary of the Abo and Arroyo de Alamillo formations, New Mexico, USA (unpublished data, personal observations: SV, 2010–2012), the Rabejac Formation, France (Gand, 1988), and the Pizzo del Diavolo and Collio formations, Italy (Nicosia et al., 2000; Marchetti et al., 2013; Marchetti, 2014). The tetrapod ichnofauna of the Collio Formation is of early Kungurian age according to radiometric data (Schaltegger and Brack, 2007). If the co-occurrence and relative abundance of Varanopus and Hyloidichnus is accepted as a proxy of the captorhinomorph radiation, then it appears to be a significant event of Paleozoic terrestrial tetrapod evolution started in the Artinskian stage based on ichnofaunal data of North America, Europe and NW Africa. At the present stage of knowledge, the tetrapod ichnofauna from UGU localities 34 and 80 suggests an Artinskian age for this track-bearing level of the Peranera Formation. Based on our results, the Peranera Formation of the Erill-Castell Basin may be of similar age as the footprint-bearing level of the Sagra Formation in the Cantabrian Mountains (Gand et al., 1997). The stratigraphic correlation to the track sites of the Peranera Formation south of La Seu d'Urgell, however, remains unresolved. The two tracks described by Robles and Llompart (1987) are more than 30 cm in size. This is far beyond the size of any known Early Permian track. As the Peranera Formation in the La Seu/Gramós Basin is estimated to be up to 1500 m thick (Saura and Teixell, 2006) it is possible that the succession includes much younger, maybe Middle Permian, red beds with a different tetrapod ichnofauna. The footprints of the Palanca de Noves site, described and compared to Chelichnus Jardine, 1850, Varanopus Moodie, 1929, Dromopus Marsh, 1894, and Dimetropus Romer and Price, 1940 by Fortuny et al. (2010), are rather poorly preserved undertracks of limited ichnotaxonomic information and do not allow comparison with the material known from the surfaces near Les Iglésies. 6. Conclusions and perspectives

Fig. 7. Dromopus Marsh, 1894 from the Peranera Formation. Material: UGKU 1939, manus and pes imprints preserved in convex hyporelief. Scale bars equal 5 mm.

The Peranera Formation of the south-central Pyrenees near Les Iglésies yields abundant and partially well-preserved footprints of Batrachichnus, Limnopus, Varanopus, Hyloidichnus, and Dromopus. These tracks can be referred to at least five different kinds of temnospondyl, captorhinomorph, and araeoscelid/bolosaurid trackmakers. The described ichnofossil assemblage is remarkable by the relative abundance and diversity of captorhinomorph footprints. In this respect it is similar to some late Early Permian ichnofaunas of North America and Morocco that all lack Erpetopus, an index vertebrate trace fossil for Kungurian and younger Permian strata. The Peranera Formation of the study area may cover the onset of one of the interesting periods of Late Paleozoic

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Fig. 8. Stratigraphic range of common and well-known Permian tetrapod ichnotaxa (thick bar = fossil evidence; thin bar = distribution supposed). Formation names exemplify footprintbearing deposits of the respective time interval. Data are compiled from Newell et al. (1976), Haubold (1984, 2000), Van Allen et al. (2005), Voigt (2005), Gand and Durand (2006), Lucas (2007), Voigt et al. (2010, 2013), Hminna et al. (2012), Marchetti (2014), and Sacchi et al. (2014).

tetrapod evolution which is the late Early Permian radiation of captorhinomorphs. The Permian red beds of the south-central Pyrenees are a promising target for prospection on fossil vertebrate remains in general. Additional ichnofossil material may help to clarify the taxonomy of the Permian tracks found in the La Seu/Gramós Basin, to correlate the already known track sites as well as to constrain the stratigraphic range of the Late Paleozoic red beds of the study area. There is reason to hope that this thick succession of continental deposits also bears evidence of otherwise unknown early therapsids. Acknowledgment This paper benefits from joint field work and discussion on captorhinomorph footprints with colleagues from the New Mexico Museum of Natural History and Science in Albuquerque, New Mexico, the Chouaïb Doukkali University in El Jadida, Morocco, the TU Bergakademie Freiberg, Germany, and the University of Padova, Italy. The German Science Foundation (DFG Ha 1872/1-4; DFG Schn 408/ 17) financially supported several projects on Late Paleozoic tetrapod footprints during the last two decades. We thank Spencer G. Lucas and Lorenzo Marchetti for their constructive reviews. References Baird, D., 1952. Revision of the Pennsylvanian and Permian footprints Limnopus, Allopus and Baropus. J. Paleontol. 26, 832–840. Bixel, E., Lucas, C., 1983. Magmatisme, tectonique et sédimentation dans les fosses stéphano-permiens des Pyrénées occidentales. Rev. Géol. Dynam. Géog. Phys. 24, 329–342. Butts, E., 1891. Recently Discovered Footprints of the Amphibian Age in the Upper Coal Measure Group of Kansas City 5. Kansas City Scientist, Missouri, pp. 17–19. Clack, J.A., 1997. Devonian tetrapod trackways and trackmakers: a review of the fossils and footprints. Palaeogeogr. Palaeoclimatol. Palaeoecol. 130, 227–250. Demathieu, G., Torcida Fernández-Baldor, F., Demathieu, P., Urién Montero, V., PérezLorente, F., 2008. Icnitas de grandes vertebrados terrestres en el Pérmico de Peña

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