This is the accepted version of the journal article: Casanovas i Vilar, Isaac; Garcés, Miguel; Marcuello, Álex; [et al.]. «Els Casots (Subirats, Catalonia), a key site for the Miocene vertebrate record of Southwestern Europe». Historical Biology, (March 2022). DOI 10.1080/08912963.2022.2043296 This version is available at https://ddd.uab.cat/record/256972 under the terms of the license 1 Els Casots (Subirats, Catalonia), a key site for the Miocene vertebrate 2 record of Southwestern Europe 3 Isaac Casanovas-Vilara*, Miguel Garcésb–c, Álex Marcuellob–c, Juan Abellaa,d, Joan Madurell- 4 Malapeiraa, Sílvia Jovells-Vaquéa,e, Lluís Cabrerab–c, Jordi Galindoa, Elisabet Beamudc,f, Juan 5 José Ledob–c, Pilar Queraltb–c, Anna Martíb–c, Josep Sanjuanb, Carles Martín-Closasb, Gonzalo 6 Jiménez-Morenog, Àngel H. Lujána,h, Andrea Villaa, Daniel DeMigueli,a, Israel M. Sáncheza, 7 Josep M. Roblesa, Marc Furiój,a, Lars W. Van den Hoek Ostendek, Antonio Sánchez Marcoa, 8 Óscar Sanisidrol, Alberto Valencianom,n, Israel García-Paredeso,a, Chiara Angelonep,a,q, 9 Guillem Pons-Monjoa, Beatriz Azanzam, Massimo Delfinor,a, Arnau Boleta,s, Montserrat Grau- 10 Camatsa, Víctor Vizcaíno-Varoa, David Mormeneoa, Yuri Kimurat,a, Salvador Moyà-Solàa,u, 11 David M. Albaa a 12 Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, 13 Cerdanyola del Vallès, Spain. 14 b Departament de Dinàmica de la Terra i de l’Oceà, Universitat de Barcelona, Barcelona, 15 Spain. c 16 Institut de Recerca Geomodels, Grup de Recerca Consolidat de Geodinàmica i Anàlisi de 17 Conques, Universitat de Barcelona, Barcelona, Spain. d 18 Instituto Nacional de Biodiversidad, Quito, Ecuador. e 19 Department of Geology and Palaeontology, Faculty of Natural Sciences, Comenius 20 University, Bratislava, Slovak Republic. f 21 Paleomagnetic Laboratory, CCiTUB-Geo3BCN CSIC, Barcelona, Spain. g 22 Departamento de Estratigrafía y Paleontología, Universidad de Granada, Granada, Spain. h 23 Department of Geological Sciences, Faculty of Science, Masaryk University, Brno, Czechia. 24 1 i 25 ARAID foundation / Departamento de Ciencias de la Tierra and Instituto Universitario de 26 Investigación en Ciencias Ambientales de Aragón (IUCA), Zaragoza, Spain. j 27 Serra Húnter Fellow, Departament de Geologia, Universitat Autònoma de Barcelona, 28 Cerdanyola del Vallès, Spain. k 29 Naturalis Biodiversity Center, Leiden, the Netherlands. l 30 Universidad de Alcalá, GloCEE -Global Change Ecology and Evolution Research Group, 31 Departamento de Ciencias de la Vida, Alcalá de Henares, Spain. m 32 Departamento de Ciencias de la Tierra and Instituto Universitario de Investigación en 33 Ciencias Ambientales de Aragón (IUCA), Universidad de Zaragoza, Zaragoza, Spain. n 34 Research and Exhibitions Department, Iziko Museums of South Africa, Cape Town, South 35 Africa. o 36 Departamento de Educación, Métodos de Investigación y Evaluación, Facultad de Ciencias 37 Humanas y Sociales, Universidad Pontificia Comillas, Madrid, Spain. p 38 Dipartimento di Scienze, Università degli Studi Roma Tre, Roma, Italy. q 39 Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate 40 Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China. r 41 Dipartimento di Scienze della Terra, Università di Torino, Torino, Italy. s 42 School of Earth Sciences, University of Bristol, Bristol, United Kingdom. t 43 Department of Geology and Paleontology, National Museum of Nature and Science, 44 Tsukuba, Japan. u 45 Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain. 46 47 *Corresponding author. E-mail address: isaac.casanovas@icp.cat 48 49 ORCIDs: 2 50 Isaac Casanovas-Vilar: 0000-0001-7092-9622 51 Miguel Garcés: 0000-0001-7666-6392 52 Álex Marcuello: 0000-0002-6216-4436 53 Juan Abella: 0000-0002-3433-6093 54 Joan Madurell-Malapeira: 0000-0003-4639-9451 55 Sílvia Jovells-Vaqué: 0000-0003-0358-0840 56 Lluís Cabrera: 0000-0003-0995-310X 57 Jordi Galindo: 0000-0002-8796-3584 58 Elisabet Beamud: 0000-0003-3158-2966 59 Juan José Ledo: 0000-0003-1548-1575 60 Pilar Queralt: 0000-0002-4195-4228 61 Anna Martí: 0000-0002-9551-8069 62 Josep Sanjuan: 0000-0002-1275-6783 63 Carles Martín-Closas: 0000-0003-4349-738X 64 Gonzalo Jiménez-Moreno: 0000-0001-7185-8686 65 Àngel H. Luján: 0000-0003-1844-0453 66 Andrea Villa: 0000-0001-6544-5201 67 Daniel DeMiguel: 0000-0001-6138-7227 68 Israel M. Sánchez: 0000-0003-2151-7693 69 Josep M. Robles: 0000-0002-5410-3529 70 Marc Furió: 0000-0002-4582-3268 71 Lars W. Van den Hoek Ostende: 0000-0003-3114-0121 72 Antonio Sánchez Marco: 0000-0003-0654-1935 73 Óscar Sanisidro: 0000-0002-8238-6394 74 Alberto Valenciano: 0000-0003-1633-2248 3 75 Israel García-Paredes: 0000-0003-4390-2349 76 Chiara Angelone: 0000-0002-7140-9431 77 Guillem Pons-Monjo: 0000-0002-5218-6877 78 Beatriz Azanza: 0000-0003-2487-547X 79 Massimo Delfino: 0000-0001-7836-7265 80 Arnau Bolet: 0000-0003-4416-4560 81 Montserrat Grau-Camats: 0000-0002-1481-7033 82 Víctor Vizcaíno-Varo: 0000-0001-8312-7186 83 Yuri Kimura: 0000-0002-7621-9901 84 Salvador Moyà-Solà: 0000-0001-8506-1061 85 David M. Alba: 0000-0002-8886-5580 86 4 87 ABSTRACT 88 Els Casots is one of the richest fossil vertebrate sites of the Vallès-Penedès Basin (Catalonia, 89 Spain). It was discovered in 1989 and excavated briefly during the 1990s, resulting in the 90 recovery of thousands of remains and the erection of several new mammal species. 91 Excavations resumed in 2018 and continue to date. Here we provide updated results regarding 92 the age, stratigraphy, biota and palaeoenvironment of the site. The age of the site is well 93 constrained to ~15.9 Ma thanks to recent bio- and magnetostratigraphic data, thus coinciding 94 with the onset of the Miocene Climatic Optimum (MCO). The stratigraphic succession at the 95 site area indicates lacustrine to palustrine environments with cyclically oscillating water level. 96 There are several fossiliferous layers that have yielded a vertebrate fauna comprising up to 74 97 different vertebrate species including amphibians, reptiles, birds and mostly mammals. The 98 finding of several articulated partial skeletons indicate that the site records an autochthonous 99 to parautochthonous assemblage. The abundance and completeness of the vertebrate remains 100 together with a well-constrained age and detailed stratigraphic and palaeoenvironmental data, 101 make els Casots a key site for understanding wetland ecosystems in southern Europe during 102 the MCO. 103 104 KEYWORDS: Miocene Climatic Optimum, fossil vertebrates, taphonomy, 105 palaeoenvironment, Vallès-Penedès Basin, Spain 106 5 107 Introduction and historical overview 108 The Early to Middle Miocene transition was a crucial period marked by important climatic 109 and faunal changes. The former notably comprise the Miocene Climatic Optimum (MCO), the 110 warmest interval since the late Eocene, which peaked between ~17–15 Ma (Zachos et al. 111 2001). This interrupted the long-term Cenozoic cooling trend and Antarctic ice-sheet build up 112 (Shevenell et al. 2008; Foster et al. 2012), resulting in estimated mid-latitude atmospheric 113 temperatures 5–7° C warmer than today (Steinthorsdottir et al. 2021). The MCO coincided 114 with a series of faunal dispersals, such as those of modern cricetid rodents or bovids which 115 ―contrary to earlier Miocene dispersals (e.g., those between Africa and Eurasia)― were not 116 facilitated by new continental connections. During the Miocene these newcomers would 117 replace older groups of Palaeogene origin and ‘modernise’ the mammal faunas. This time 118 interval is well represented in several Spanish basins, such as the Calatayud-Montalbán Basin 119 (Aragon; Van der Meulen et al. 2012; García-Paredes et al. 2016), the Magro Basin 120 (Valencia; Ruiz Sánchez et al. 2003), the Ribesalbes-Alcora Basin (Valencia, Crespo et al. 121 2019) or the Bardenas Reales (Navarra) in the Ebro Basin (Suárez-Hernando 2017). However, 122 their record mostly consists of microvertebrates, larger mammals being generally scarce. By 123 contrast, the Vallès-Penedès Basin (Catalonia) presents a rich record for the Early/Middle 124 Miocene transition that includes several sites that have yielded both large and small 125 vertebrates. Amongst these, els Casots stands out as one of the richest sites of the whole 126 basin, including thousands of specimens, often exceptionally complete. 127 Els Casots (note that the correct toponym according to the Cartographical and 128 Geological Institute of Catalonia is ‘els Casots’, with ‘els’ not capitalized) pertains to the 129 municipality of Subirats (l’Alt Penedès), less than 40 km away from Barcelona. During the 130 late 19th century, several short-lived lignite mines were active near els Casots and eventually 131 the workers found a few fossil bones and teeth that were handled to the priest and geologist 6 132 Jaume Almera, from the Geological Museum of the Barcelona Seminary. These stand out 133 amongst the earliest finds of fossil vertebrates in Catalonia. Almera entrusted their 134 identification to well-known vertebrate palaeontologists of his time, such as Charles Depéret 135 and Albert Gaudry, who ascribed them to rhinoceroses, ruminants and rodents (Almera 1898). 136 When the mines closed no further findings were reported and eventually those given to 137 Almera were lost or destroyed in 1936, at the beginning of the Spanish Civil War. Later, the 138 renowned palaeontologist Miquel Crusafont, founder of the Institut de Paleontologia de 139 Sabadell (IPS, predecessor of the Institut Català de Paleontologia Miquel Crusafont, ICP), and 140 his collaborators surveyed the mine surroundings and only found some fossil plants but not 141 vertebrates (Crusafont et al. 1955). Finally, in 1989 Toni Adell, an amateur fossil hunter 142 found several bones on the surface of a vineyard close to the ancient mines (Figure 1a) and 143 these were reported to S.M.S from the IPS (Moyà-Solà and Rius Font 1993). Systematic 144 excavations followed between 1989 and 1993, resulting in the recovery of more than 3,000 145 macrovertebrate remains from different fossiliferous levels (Moyà-Solà and Rius Font 1993). 146 In addition, samples from some levels were screen-washed and yielded hundreds of 147 identifiable micromammal teeth. All the recovered fossils were deposited at the ICP and most 148 of them have been prepared. In 1995, the site was acquired by the municipality of Subirats 149 and protected as cultural heritage by the Catalan government. However, excavations were 150 interrupted in 1994, mostly because the discovery or re-excavation of major sites in the same 151 area (e.g., Can Llobateres) required the limited funding and personnel available. 152 Nevertheless, the study of the fauna continued during the 1990s, mostly focusing on 153 artiodactyls. New species such as the listriodontine suid Eurolistriodon adelli (Pickford and 154 Moyà-Solà, 1995) or the palaeomerycid Ampelomeryx ginsburgi Duranthon et al., 1995 were 155 erected based on material from els Casots. In the 21st century taxonomic studies expanded to 156 consider crocodylians, rodents and small carnivorans, amongst others (see below). Yet, there 7 157 are relatively few works devoted to the biota from els Casots and none summarising the 158 characteristics and significance of the site. In 2018, after more than 20 years of inactivity, the 159 ICP resumed fieldwork at els Casots. Yearly campaigns are currently conducted, and these 160 include not only systematic excavation, but also geological survey and sampling to provide 161 further insights on the age and palaeoenvironment of the site. Furthermore, several actions, 162 such as building permanent structures to shelter main excavation areas (Figure 1b), have been 163 undertaken by the Subirats municipality and the site is open for touristic visits upon request. 164 Here we present an overview of the els Casots site, its geology, age, biota and 165 palaeoenvironment based on our latest data. 166 167 Geological setting 168 Els Casots is located at the southern margin of the Vallès-Penedès Basin (VPB), an elongated 169 half-graben sub-parallel to the Catalan coastline and bounded by the Catalan Coastal Ranges 170 (Figure 2a), that was formed during the opening of the Western Mediterranean by the late 171 Oligocene (Roca et al. 1999; Cabrera et al. 2004). The VPB sedimentary record covers most 172 of the Miocene (from about 20 to 7 Ma) and is mainly continental except for relatively brief 173 marine episodes that occurred during the late Burdigalian (Early Miocene), Langhian and 174 early Serravallian (Middle Miocene), and Tortonian (Late Miocene; Casanovas-Vilar et al. 175 2016). Early to early Middle Miocene continental alluvial deposits interdigitate and are finally 176 overlain by shallow to deep marine (bay, shelf) and transitional deposits (fan deltas and minor 177 deltas, shoreline systems and saline lagoons) ranging in age from late Burdigalian to 178 Langhian. The continental, transitional and marine facies are stacked in transgressive– 179 regressive sequences that attained their maximum spreading and depth in the basin during the 180 Langhian sea-level high stand. 8 181 In general, the Early to early Middle Miocene (Ramblian to early Aragonian mammal 182 ages) terrestrial vertebrate record of the VPB is comparatively poorer than later intervals (late 183 Aragonian and Vallesian mammal ages; Casanovas-Vilar et al. 2016). This interval is 184 recorded by the sequences of the Lower Continental Units, a lithostratigraphical unit that 185 crops out near the southern basin margins and at the Llobregat and Anoia river valleys. This 186 assemblage includes intensely red alluvial fan facies sourced from the surrounding reliefs and 187 minor cyclically arranged alluvial-shallow lacustrine units of various ages (Cabrera Pérez 188 1981a; Cabrera et al. 1991; de Gibert and Casanovas-Vilar 2011; Casanovas-Vilar et al. 2011, 189 2016). The younger alluvial-lacustrine assemblage (Subirats alluvial-lacustrine unit; Agustí 190 and Cabrera 1980; Cabrera Pérez 1981a, 1981b) includes the site of els Casots as well as 191 other rich fossil sites such as les Cases de la Valenciana (Crusafont et al. 1955; Jovells-Vaqué 192 et al. 2018), Can Julià and Can Martí Vell (Crusafont et al. 1955; Agustí and Cabrera 1980; 193 Agustí 1983). This unit unconformably overlays directly the Mesozoic basement (Cabrera 194 Pérez 1979, 1981a, 1981b) and extends a few kilometres along the present southern basin 195 margin between the municipalities of Gelida and Subirats (Figure 2). Els Casots is located in a 196 continental to transitional sequence developed in an extensional faulted zone that affected 197 both the Mesozoic basement and the Miocene cover. 198 199 Structure, stratigraphy and age of the succession 200 Structure and arrangement of the basement 201 The pre-Miocene basement at the area of els Casots consists of Mesozoic, mainly Early 202 Cretaceous, marine carbonates (Figure 2b). To determine the basement arrangement, 203 geophysical prospection using ERT (Electrical Resistivity Tomography) methods was 204 conducted at the site area to infer the thickness of Miocene sediments and preliminarily study 9 205 the basement morphology. ERT data were collected along two intersecting sections (Figure 206 2b), and they encompassed three ERT profiles. Geoelectrical results are presented along two 207 sections built from the 2D models obtained from the ERT profiles (Figure 3). Geoelectrical 208 section 1 (Figure 3a) shows a preferential stratified behaviour with an alternate of conductive 209 and resistive layers gently dipping to the centre of the section. It also presents three segments 210 (A, B, and C) where this stratification is not complete. A similar behaviour is recognized in 211 section 2 (Figure 3b), with a horizontal stratification and an abrupt change in segment D. 212 The interpretation of section 1 is based on the information provided by two core 213 samples (CS-A and CS-B, see following section and Figure 4) taken next to the section (see 214 Figure 2b). The Cretaceous basement is identified as the bottom resistive layer (Figure 3, in 215 blue), while the different conductive and resistive layers in the Miocene cover can be 216 associated with the clayey and carbonate sequences described in the cores. Regions A, B, and 217 C (Figure 3a) may be interpreted as three fractured zones affected by minor normal faults 218 dipping to the N. In Section 2 (Figure 3b), basement identification is not straightforward 219 because this section runs along the fractured zone B. However, this section does not present 220 E-W changes in resistivity except in region D, which coincides with the location of the 221 inferred NE-SW fault (Figure 2b). 222 Attending to the geological and geophysical data, the pre-Miocene basement at els 223 Casots area consists of Mesozoic (mainly Early Cretaceous) marine carbonates, which make 224 up the present surrounding reliefs. During the Early to Middle Miocene these rocks 225 constituted a weathered, eroded and karstified palaeorelief later affected by NE-SW and 226 NNE-SSW faults related to extensional processes in the area. 227 228 Miocene stratigraphy 10 229 The overall stratigraphy of the Subirats alluvial-lacustrine unit at els Casots has been 230 previously described (Cabrera Pérez 1979, 1981a, 1981b). The lithological succession in the 231 area nearby the fossil site was further studied by means of geological core sampling next to 232 the excavation area (core CS-A; Figure 2b) and at the point of maximum thickness of 233 Miocene sediments as inferred from ERT results (core CS-B; Figure 2b). 234 Core CS-B (Figure 4) reached the Mesozoic basement at 36 m of depth. A 4 m-thick 235 deposit of clast- to matrix-supported scree breccias overlay the karstified Cretaceous 236 basement. The often large (up to several cm in diameter) clasts are made of Cretaceous 237 carbonates and show little rounding or are clearly subangular to angular, thus indicating that 238 they derived from in situ substrate fragmentation. The matrix consists of mudstone that grades 239 upwards from ochre/reddish to greenish grey due to reductive conditions associated to the 240 lacustrine flooding. Grey mudstone including outsized limestone granules and clasts overlay 241 the clast dominated lowermost deposits. Similar deposits overlay the basement in the 242 surrounding outcrops (Figure 2b) and include plant, gastropod and vertebrate fossils, badly 243 broken macrovertebrate remains and abundant micromammals (Cal Sutxet site; Jovells-Vaqué 244 and Casanovas-Vilar 2021). The lowermost breccia unit is of variable thickness because it 245 overlaid the pre-existing palaeorelief. This breccia unit is overlain by a 25 m-thick, cyclically- 246 arranged mudstone/limestone succession that at the bottom includes thin (mm to dm thick) 247 sub-bituminous coal deposits. Cycles often include a lower dark, organic matter rich term that 248 grades upwards to grey-bluish massive mudstones with minor, scattered millimetric siderite- 249 like ferruginous nodules. The upper part of the cycles is a carbonate term that includes a 250 variety of bioclastic- to micrite-dominated limestones (grainstones, wackestones and 251 mudstones) that range from a few centimetres to a maximum of a couple of meters thick 252 (Figure 4). The carbonate facies include bioclastic laminae made up of accumulations of 253 ostracods, charophytes and micrite-coated algal filaments. Very thin tufa-like carbonates also 11 254 occur (Cabrera Pérez 1979). Thin ferruginous laminae are associated to some of the bioclastic 255 facies. Both carbonates and siliciclastic mudstones may include abundant plant fragments and 256 freshwater gastropod shells or casts. This lacustrine/marshy lacustrine succession has yielded 257 abundant vertebrate fossils in the excavated area (Figure 5). 258 The lacustrine succession ends rather abruptly and in core CS-B grades along the 259 uppermost 5 m into intensely reddish and mottled silts and sandstones topped by carbonate- 260 rich pedogenic to palustrine facies (Figure 4). These palustrine facies crop out W of Cal 261 Sutxet farmhouse (Figure 2b) and are rich in internal moulds of terrestrial gastropods but are 262 devoid of vertebrate fossils. They are overlain by red mudstones and green/grey sandstones 263 that record subaerial distal channelized alluvial fan facies. The continental deposits are in turn 264 overlain by an oyster coquina and a bioclastic quartzarenite, which marks the early Langhian 265 transgressive surface in this sector. The Langhian marine transgression and high-stand marine 266 facies in the area record successive episodes of deposition of bioturbated sandstones overlain 267 by grey marine bay-shelf mudstones and marls and some episodes of minor reef construction 268 (Bessedik and Cabrera 1985; Agustí et al. 1990; Domènech et al. 2011; Casanovas-Vilar et al. 269 2016). 270 271 Age 272 Els Casots has been generally correlated to European Neogene Mammal (MN) unit MN4, 273 which corresponds to the early Aragonian, latest Early Miocene (e.g., Agustí et al. 1990; 274 Agustí and Llenas 1993; Duranthon et al. 1995; Pickford and Moyà-Solà 1995; Casanovas- 275 Vilar et al. 2011a, 2011b, 2016; Jovells-Vaqué et al. 2017a). Such correlation was mostly 276 based on the rodent fauna, which includes the early modern cricetids Megacricetodon 277 primitivus and Democricetodon hispanicus together with the eomyid Ligerimys ellipticus. 12 278 However, recent studies indicate that els Casots should indeed be correlated to MN5 (Jovells- 279 Vaqué and Casanovas-Vilar 2021). The MN4/MN5 boundary was previously defined by the 280 extinction of the eomyid genus Ligerimys (e.g., Mein 1999; Kälin and Kempf 2009), which 281 turned out to be a diachronic event in Western Europe, with the last Iberian species, L. 282 ellipticus, persisting for about 0.5 million years after the extinction of the last central 283 European species, Ligerimys florancei (Van der Meulen et al. 2012). However, the extinction 284 of L. florancei is synchronous in both areas (~16.4 Ma), so this has been proposed as the 285 diagnostic criterion for the definition of the MN4/MN5 boundary (Hilgen et al. 2012; Van der 286 Meulen et al. 2012). At els Casots, only L. ellipticus is present (and in low numbers), 287 suggesting a correlation to early Aragonian subzone Cb (16.15–15.94 Ma; see Van der 288 Meulen et al. 2012), corresponding to the earliest MN5, the beginning of the Middle Miocene. 289 Cores CS-A and CS-B were sampled for palaeomagnetism at an average interval of 290 0.35 cm, collecting 57 samples from core CS-A and 78 samples from core CS-B, and 291 additional oriented samples were taken from the fossil site on surface and the overlying, non- 292 lacustrine sediments, up to the Langhian oyster coquina (Figure 2). Bedding dip, when 293 observable in the cores, was taken as a reference for the orientation of palaeomagnetic 294 samples. Both stepwise alternating field (AF) and thermal (TH) demagnetization was applied 295 to all samples, providing comparable results. A viscous component was demagnetized at 296 temperatures below 200º C and peak AF of 10 mT. Above this range, a stable characteristic 297 remanent magnetization (ChRM) could be determined up to temperatures of 450º C and peak 298 AF of 60 mT. The ChRM was ranked as Quality 1 when a linear decay was observed until 299 complete demagnetization. As the samples from cores lacked azimuthal orientation, the 300 polarity determination relied only on the inclination of the ChRM, positive (downwards) 301 inclination representing normal polarity and vice versa. For caution, ChRM components 302 yielding low inclinations (reference palaeomagnetic inclination at the site is 60º) were not 13 303 considered as reliable and were ranked as Quality 2. A complementary quality check applied 304 was the coherency of the angular relationship between the viscous and the ChRM 305 components. Since the viscous component mostly conform to the north-directed present-day 306 field, a reversed polarity ChRM should be roughly antiparallel to the viscous component, 307 while a normal polarity ChRM should tend to align with the viscous component. ChRM 308 directions meeting this condition were included in Quality 1. 309 Best quality results were obtained from core CS-B, with 66 samples (88%) ranked as 310 Quality 1, compared to 25 (44%) samples of Quality 1 from CS-A. The whole series shows 311 reverse polarity except for a normal interval determined at a depth between 12–15 m in CS-A, 312 but not confirmed in CS-B, which yielded a palaeomagnetic signal of higher quality. 313 Therefore, we consider this interval of normal magnetization from CS-A possibly resulted 314 from a secondary magnetization process, unrelated with the time of deposition. Two 315 additional normal magnetization intervals in CS-B are very thin, marked only by one sample, 316 and were not considered relevant for correlation purposes. As already exposed, the rodent 317 assemblage indicates a correlation to early Aragonian subzone Cb, which in the Calatayud- 318 Montalbán Basin spans the whole normal polarity geomagnetic chron C5Cn.1n and the 319 earliest part of the inverse polarity chron C5Br (Van der Meulen et al. 2012). Considering 320 these data, the dominantly reverse polarity interval recorded in the cores is best correlated to 321 chron C5Br (15.974–15.160 Ma; boundaries after Ogg 2020). Coupled with the 322 aforementioned correlation to Aragonian subzone Cb (16.15 – 15.94 Ma; Van der Meulen et 323 al. 2012), this results in an estimated age of ~15.9 Ma for the site of els Casots. 324 325 Excavated area and taphonomic remarks 14 326 The fossiliferous area of els Casots is huge, comprising all the fields around the farmhouses of 327 Cal Solà and Cal Sutxet, but only a small area of about 6,200 m2 is protected (Figures 1, 2b). 328 For the moment being, a small surface of just 400 m2 has been excavated, most of it during 329 the 1990s field campaigns. Detailed stratigraphic information from the different excavated 330 sectors (or ‘spots’) was recorded during the 1990s field campaigns and up to 13 stratigraphic 331 levels (labelled A to M) were distinguished from surface to bottom (Figure 5). These 332 represent a ~2 m thick succession consisting of mostly greyish to ochre mudstones, with 333 occasional thin black mudstone layers. A thin layer of reddish carbonates (L) crops out at the 334 base of the excavated sections. Mudstones are often laterally discontinuous and of variable 335 thickness within the site area. They are rich in mollusc shell fragments and may include plant 336 remains (mostly wood). Carbonate nodules are abundant in some levels. 337 Although all levels have yielded macrovertebrate fossils, level E turned out to be the 338 most productive in the 1990s campaigns. Field campaigns since 2018 have focused on the 339 excavation of level J, a bone bed that has yielded partially articulated specimens (Figures 6b– 340 d, 7). Furthermore, well-preserved carnivoran coprolites and numerous wood fragments have 341 been found at level J. Taphonomic information was recorded during both recent and older 342 field campaigns. Macrovertebrate remains occur in high concentrations in all the excavated 343 area laying subhorizontally, parallel to stratigraphy, and do not show signs of transport. 344 Therefore, although detailed taphonomic analyses have yet to be conducted, we interpret that 345 the biota from els Casots represents an autochthonous to parautochthonous assemblage. 346 Lithostatic pressure has resulted in extensive crushing and deformation of many remains. For 347 example, the holotype cranium of the suid Eurolistriodon adelli (IPS9096; Pickford and 348 Moyà-Solà 1995: figs. 1–2) is so flattened dorsoventrally that it measures less than 5 cm in 349 thickness. Almost all the fossils recovered during the 1990s have been prepared for study, but 15 350 only a few of the most relevant specimens (such as articulated skeletons and crania) found in 351 the new excavations are prepared. 352 Microvertebrates were recovered during the 1990s field campaigns after screen- 353 washing sediment samples from three different levels (CS-72, CS-73 and CS-74, certainly 354 equivalent to excavation level D; Figure 5) and yielded hundreds of identifiable dental 355 remains, mostly belonging to rodents (Agustí and Llenas 1993). During the new field 356 campaigns large amounts of sediment have been screen-washed from layers K, J and M 357 resulting in the recovery of thousands of microvertebrate remains, which include a diverse 358 palaeoherpetological assemblage, some bird remains and numerous rodent, lagomorph and 359 insectivoran cheek teeth. Even if only a small part of this collection has been prepared for 360 study and is considered here, as shown in the following sections, the amount of new 361 information is so relevant that els Casots can be already considered a key locality for the 362 Miocene vertebrate record of Southwestern Europe. 363 364 Biota and palaeoenvironment 365 Flora and invertebrates 366 Crusafont et al. (1955) reported a single palm leaf found near the abandoned coal mines next to 367 els Casots. Poorly preserved leaf fragments of helophytic plants, i.e., reeds and sedges (e.g., 368 Typha) and wood fragments have been recovered during the recent excavations. Sediment 369 samples next to the excavation area have been screen-washed and yielded gyrogonites which 370 are currently under study. The charophyte assemblage is dominated by Chara cf. vulgaris and 371 Chara molassica var. notata. Extant C. vulgaris inhabits various kinds of freshwater 372 environments, ranging from small eutrophic temporary ponds to mesotrophic lakes and rivers. 373 Core samples from the site area (see above) were also analysed in search for palynomorphs, but 16 374 without success. Invertebrates are represented at the site by fragments of ostracod carapaces, 375 mollusc shell fragments (such as freshwater gastropods) and, in the non-lacustrine upper layers, 376 by moulds of terrestrial gastropods. Rare benthic foraminifera (i.e., Ammonia sp.) also occur in 377 the assemblage and were probably transported from nearby marine settings. 378 379 Non-mammalian vertebrates 380 Highly fragmentary fish dental remains have been recovered by means of screen-washing but 381 have neither been prepared nor studied. The herpetofauna is especially diverse, including up to 382 24 different species (Table 1), and the available collection has increased significantly after the 383 latest field campaigns. Amphibians include anurans and urodeles, the latter represented by just 384 a single humerus. Anurans are more abundant, but most of the recovered remains do not allow 385 for a confident taxonomic attribution. Based on ilial morphology, at least three different genera 386 are present: the discoglossine alytid Latonia (already known from the roughly coeval site of 387 Sant Mamet and other younger sites in the VPB; Villa et al. 2019a), the bufonid Bufotes (gr. 388 viridis), and the ranid Pelophylax. 389 Chelonian fossils include scarce remains of the geoemydid Ptychogaster as well as a 390 few disarticulated shell plates and some phalanges attributed to the medium-sized tortoise 391 Testudo. The lack of diagnostic shell parts precludes an assignment to the subgenus rank for 392 both taxa (Luján et al. 2014a, 2016). The most abundant and complete chelonian material, 393 comprising both shell and postcranial remains, belongs to giant tortoises of the genus 394 Titanochelon. The epiplastron resembles that of Titanochelon richardi, common in Middle to 395 Late Miocene (MN6–MN10) sites of the VPB (Luján et al. 2014b). Squamates are by far the 396 most diverse group in the palaeoherpetological assemblage. Gekkotans are represented by very 397 few bones, while lacertids, whose identification is often difficult if not impossible based on 17 398 isolated and fragmentary bones, are represented by at least a non-amblyodont form together 399 with a slightly-amblyodont one (cf. Amblyolacerta sp.). A scincoid is also present, based on the 400 tooth morphology of few fragmentary dentigerous elements. Several remains of non-Anguis 401 anguines were recovered, especially osteoderms and vertebrae. A single fragment of an 402 indeterminate dentigerous bone with an Ophisaurus-like dentition as well as at least one trunk 403 vertebra morphologically similar to those of Pseudopus has been recovered. A few vertebrae 404 and isolated teeth possibly belong to varanid lizards. Two small amphisbaenian premaxillae can 405 be referred to a member of the western clade of Blanus owing to the flat morphology of their 406 anterior outline in lateral view (Bolet et al., 2014; Villa et al. 2019b). Snakes, in turn, are mainly 407 identified based on vertebral morphology. The most abundant taxon is a pythonid, but an 408 indeterminate scolecophidian, an erycine boid, at least one “colubrine” (sensu Szyndlar 1991), 409 and possibly two viperids (a large and a smaller one) are present. 410 Small-sized crocodylians are extremely abundant at the site, being represented by 411 countless isolated plates, osteoderms and teeth, as well as by complete skulls. During the 2021 412 field campaign a complete articulated skeleton was unearthed and is currently under study. 413 Cranial remains recovered during the 1990s field campaigns were described in detail by Díaz 414 Aráez et al. (2017) and assigned to the diplocynodontid Diplocynodon ratelii. This represents 415 the youngest record of the genus in the Iberian Peninsula. 416 Avian remains are rare, and most can be attributed to a medium-sized diurnal raptor 417 showing some morphological similarities with the extant Circaetus. There is also evidence of 418 a larger eagle (cf. Aquila sp.), an unknown nocturnal raptor (Strigidae indet.) of the size of an 419 eagle owl, and the well-known peafowl Miophasianus altus and present in other sites of the 420 VPB (Sánchez-Marco 2021). 421 18 422 Small mammals 423 Small mammals are incredibly abundant in all levels and are represented by isolated cheek 424 teeth as well as mandibular and cranial material (Jovells-Vaqué et al. 2017b). However, only 425 some rodent groups have been studied in detail. Els Casots records one of the latest 426 occurrences in the Iberian Peninsula (see Furió et al. 2012) of the small marsupial 427 Amphiperatherium frequens, represented by a few isolated teeth. Chiropterans are similarly 428 rare, just a couple of molars of a small-sized taxon have been found to date. Most of the 429 recovered eulipotyphlan remains belong to the small-sized erinaceid Galerix symeonidisi. 430 Other insectivorans include the heterosoricid Heterosorex neumayrianus, represented by just 431 one fissident upper incisor, a few teeth belonging to the tiny soricid Paenelimnoecus cf. 432 truyolsi, and two unicuspids with rather strong cingula that may belong to the dimylid 433 Plesiodimylus. The insectivoran assemblage is somewhat poorer than that of older sites 434 (MN3–MN4) of the same basin, which usually record up to six different species (Van den 435 Hoek Ostende et al. 2020). Lagomorphs are represented by the ochotonid Lagopsis, common 436 in Early and Middle Miocene sites of the VPB (López Martínez 1989). 437 Rodents display a remarkable diversity of ground squirrels (Sciuridae) including both 438 xerins (Atlantoxerus idubedensis, Heteroxerus rubricati) and marmotins (Csakvaromys 439 besana), which were described by Aldana Carrasco (1991, 1992). Cricetids and glirids stand 440 out as the most abundant rodents. The former, which were thoroughly described by Jovells- 441 Vaqué et al. (2017a) and Jovells-Vaqué and Casanovas-Vilar (2021), include Megacricetodon 442 primitivus and three Democricetodon species: De. hispanicus, which is the most abundant; 443 De. gracilis, represented by a few small specimens; and a larger indeterminate species 444 recorded by a single lower first molar. Interestingly, De. hispanicus persists for longer in the 445 VPB than in the Calatayud-Montalbán Basin (the type area of the Aragonian; east-central 446 Spain), where it is last recorded at 16.63 Ma (Van der Meulen et al. 2003, 2012). 19 447 Democricetodon gracilis, on the other hand, indicates faunal affinities with Central Europe, 448 whereas it is absent in inner Iberian basins (Jovells-Vaqué and Casanovas-Vilar 2021). Glirids 449 have only been preliminarily studied (Agustí and Llenas 1993), but up to nine different 450 species have been identified. Many of these are characterised by their simplified dental 451 pattern –such as Peridyromys murinus, Pseudodryomys ibericus and the three species of 452 Simplomys (S. simplicidens, S. robustus, S. julii)– which is generally thought to reflect a 453 preference for open and arid environments (de Bruijn and Van der Meulen 1982; Van der 454 Meulen and Daams 1992; Van Dam 2006). Simplomys simplicidens and De. hispanicus stand 455 out as the most abundant rodents. The remaining glirids comprise presumably arboreal 456 species with more complex dental patterns (De Bruijn and Van der Meulen 1982; Van der 457 Meulen and Daams 1992; Van Dam 2006), namely Bransatoglis sp., Glirudinus modestus, 458 Microdyromys monspeliensis and Muscardinus sp., which are generally scarce. Finally, 459 eomyids are only represented by less than ten teeth (over more than 700 identifiable rodent 460 teeth) of Ligerimys ellipticus. This endemic Iberian species represents the last survivor of the 461 genus Ligerimys, which disappeared from central Spain at 15.93 Ma (Van der Meulen et al. 462 2012). 463 Large mammals 464 Carnivorans are diverse and comprise multiple families of caniforms and feliforms. Amongst 465 the former, amphicyonids include two undescribed species of different size, the larger one 466 being represented by an almost complete skeleton (Figure 7a). Hemycionids are represented 467 by Hemicyon stehlini. Mustelids include the gulonin Iberictis buloti, the oldest member of the 468 wolverine lineage, which is abundantly represented by dental and cranial material (Figure 6a; 469 Valenciano et al. 2020). Other mustelids comprise Paralutra sp., represented by two 470 mandibles, which was likely semiaquatic (Ginsburg 1999) as well as two distinct small-sized 471 marten-like forms (“Martes” sp. 1 and 2). Feliforms include herpestids, hyaenids and felids. 20 472 Herpestids are represented by Leptoplesictis aurelianesis, for which only few, but remarkably 473 complete, craniodental remains have been found at the site. Concerning hyaenids, only a 474 single mandible tentatively attributed to Protictitherium has been recovered. Felids are better 475 represented by abundant postcranial and dentognathic remains belonging to the lynx-sized 476 “Pseudaelurus” lorteti. During the 2021 field campaign, a crushed complete skull was found 477 and is currently under study. 478 Rhinocerotids stand out as one of the most abundant elements of the fauna, being 479 recorded by Dromoceratherium mirallesi, which was originally described from the 480 neighboring locality of Can Julià (Gelida, MN4) by Crusafont et al. (1955). This poorly 481 known rhinoceros is generally included in Plesiaceratherium (Yan and Heissig 1986) but 482 ongoing studies of the type material and additional remains from other VPB sites support the 483 distinction of Dromoceratherium (Sanisidro et al. 2018). Further rhinocerotid remains include 484 indeterminate juvenile mandibles (Figure 6c), isolated teeth, and postcranial elements pending 485 detailed study but certainly belonging to another species. In contrast to rhinocerotids, equids 486 are extremely rare at els Casots, being only represented by lower molar fragment assigned to 487 Anchitherium sp. (Rotgers and Alba 2011). 488 Artiodactyls include the small cainotherid Cainotherium miocaenicum, a very 489 common element in older (MN3–MN4) sites of the same basin (see Crusafont et al. 1955; 490 Casanovas-Vilar et al. 2016), which is much rarer at els Casots, being represented by cranial 491 and mandibular fragments. Concerning suoids, els Casots is the type locality of two species: a 492 small “peccary-like” suoid, included in the family Palaeochoeridae (Van der Made 2020) or 493 Siderochoeridae (Pickford 2017), and a larger listriodontine suid. The former is best 494 represented by a crushed skull that is the holotype of Choeromorus ibericus (Pickford and 495 Moyà‐Solà 1994; Pickford 2017). Alternatively, Van der Made (2020) synonymized this 496 species with Choeromorus primus, with the material from els Casots representing its last 21 497 appearance datum. The listriodontine is assigned to Eurolistriodon adelli, a species originally 498 described based on a skull with associated skeleton from els Casots (Pickford and Moyà-Solà 499 1995) that is alternatively included in Bunolistriodon by Van der Made (2020). However, 500 cladistic analyses indicate that Eurolistriodon is the sister taxon of Listriodon s.l. (i.e., 501 including Bunolistriodon; Orliac 2006; Orliac et al. 2010). Although E. adelli has been cited 502 from multiple MN4 and MN5 localities (Van der Made 1997, 2020; Pickford and Morales 503 2003), in the VPB it is only known from els Casots. 504 Ruminant remains are very abundant, including pecoran and non-pecoran forms. 505 Among the latter, the tragulid “Dorcatherium” crassum, which belongs to a stem group 506 distinct from Dorcatherium s.s. (Sánchez et al. 2018), is represented by several dentognathic 507 fragments (Alba et al. 2014). The pecoran fauna is diverse. Palaeomerycids are abundantly 508 represented by Ampelomeryx ginsburgi, a species erected based on els Casots material 509 (Duranthon et al. 1995). Ampelomeryx ginsburgi is abundantly represented by partial 510 skeletons of various individuals (Figure 6b) including complete crania. It belongs to a 511 palaeomerycid lineage characterised by possessing flattish non-pneumatised ossicones located 512 over ‘eyebrow’ supraorbital projections, and flat forked occipital appendages (Sánchez et al. 513 2015). Lagomerycids are rare faunal elements in the VPB, and only a few specimens 514 (assigned either to Lagomeryx rutimeyeri or Lagomeryx pumilio) have been recovered from 515 Early Miocene sites (Crusafont et al. 1955). The few teeth from els Casots are referred to L. 516 rutimeyeri because they are clearly larger than those of L. pumilio. Cervids are common and, 517 although no protoantlers have been recovered, considering some similarities with the Sant 518 Mamet material (referred by Crusafont et al. 1955 to Procervulus dichotomus), we tentatively 519 ascribe the remains to P. cf. dichotomus. Together with palaeomerycids, bovids stand out as 520 the most abundant ruminants at els Casots, being represented by profuse dental remains and 521 even a partial skeleton of Eotragus (Figure 7b). The horn cores are small, short relative to 22 522 their diameter, and show no evidence of torsion. All these traits, coupled with the moderately 523 hypsodont teeth, justify an attribution to Eotragus noyei. 524 Proboscideans include both deinotheres and gomphotheres. The former are represented 525 by a few cheek teeth assigned by Gasamans et al. (2021) to Prodeinotherium cf. bavaricum, a 526 species characteristic of the early Middle Miocene (MN5–MN6) of Europe. Gomphothere 527 remains are more common and include a partial skeleton uncovered during 2019 (Figure 6d) 528 and additional cranial and dental material from the 1990s that is here assigned to 529 Gomphotherium cf. subtapiroideum based on dental morphology. 530 531 Palaeoenvironment 532 Els Casots fossil site represents a shallow freshwater lacustrine-palustrine (Figure 8) 533 environment as evidenced by the presence of charophytes, helophytic plants, ostracods, 534 freshwater gastropods, fishes and various semiaquatic tetrapods. The latter include a diverse 535 amphibian fauna, pond turtles (Ptychogaster), and abundant remains of small-bodied 536 crocodylians (Diplocynodon). The mammal assemblage also includes the semiaquatic otter 537 Paralutra, the aquophilous tragulid “Dorcatherium”, and other taxa likely linked to wetlands. 538 For example, palaeomerycids, abundantly represented by Ampelomeryx, generally are thought 539 to be associated to boggy forests and would have fed on soft leaves and aquatic vegetation 540 (Köhler 1993; DeMiguel et al. 2014). Concerning suoids, craniodental morphology suggests 541 that Choeromorus species might have fed on swamp plants too (Pickford 2012). Stratigraphic 542 data show cyclical fluctuations in the water level, probably related to climatic cycles. 543 The faunal list includes some megathermic taxa, such as crocodylians, giant tortoises, 544 monitor lizards, pythonid and boid snakes. These indicate warm conditions associated with 545 the MCO. The small mammal assemblage is overwhelmingly dominated by the cricetids 23 546 Democricetodon and Megacricetodon and the terrestrial glirid Simplomys. Considering that 547 the site represents a certainly humid environment, the absence of beavers (castorids) is quite 548 unexpected. The diversity of arboreal small mammals is surprisingly low, with only four 549 dormice (glirid) species and no tree or flying squirrels. Insectivorous small mammals are also 550 rare and only include four insectivorans and the marsupial Amphiperatherium. The number of 551 arboreal and insectivorous small mammal species has been found to be positively correlated 552 to precipitation and environmental humidity (Van Dam, 2006), so this may indicate that at els 553 Casots more open and arid woodland environments occurred not far from the wetlands. The 554 larger-bodied herbivores include only browsing species, many of them of small size (e.g., 555 Choeromorus, Lagomeryx, Procervulus), which likely inhabited the more forested 556 environments (Fortelius et al. 1996) surrounding water masses. The different signal provided 557 by small and larger mammals may result from taphonomic bias. Whereas larger mammals 558 represent a (para-)authothonous assemblage, birds of prey are commonly the main 559 accumulation agents of small mammal remains, which would then provide a more regional 560 signal. This palaeoenvironmental reconstruction is congruent with macrofloral (Sanz de Siria 561 Catalán 1993, 2001) and palynologic (Bessedik and Cabrera 1985; Jiménez-Moreno and Suc 562 2007) data from nearby Langhian deposits from the Penedès area, which indicate tropical to 563 subtropical environments with seasonal rainfall. Scattered forests rich in tropical elements 564 developed at low altitudes near humid areas, whereas far away from the wetlands more open 565 woodlands with herbs (Poaceae, Asteraceae) and leguminous trees (e.g., Acacia) defined the 566 regional vegetation (Jiménez-Moreno and Suc 2007). 567 568 Conclusions 24 569 With up to 74 different vertebrate species represented by thousands of specimens, els Casots 570 stands out as one of the richest early MN5 sites in Europe. It includes multiple fossiliferous 571 layers, some of them bone beds, that have yielded remarkably complete remains, including 572 partial skeletons. Recent field campaigns enable constraining its age combining bio- and 573 magnetostratigraphic data to ~15.9 Ma (Aragonian subzone Cb, earliest MN5, Middle 574 Miocene) and have also provided detailed insight on the stratigraphy of the site area and 575 structure of the pre-Miocene basement. Sedimentologic, palaeobotanic and faunal data 576 indicate that els Casots corresponds to an ancient freshwater lacustrine or palustrine 577 environment that developed in a tropical-subtropical climate with rainfall seasonality. 578 Vertebrate remains represent an autochthonous to parautochthonous assemblage, as evidenced 579 by the partial articulation of several specimens. Many large mammals appear to have 580 inhabited the forests surrounding the water masses, while small mammals provide evidence of 581 drier woodlands further from the wetlands. Finally, it is noteworthy that the site dates to the 582 onset of the Miocene Climatic Optimum and provides a unique opportunity to study wetland 583 ecosystems from southern Europe during this exceptionally warm period. 584 585 Acknowledgements 586 The Ajuntament de Subirats [Subirats city council] has supported the excavations from the 587 very beginning and provided funding for the protection of the site and preparation of the fossil 588 remains. We appreciate the interest by Caves Olivé i Batllori (Subirats), which allowed core 589 drilling, survey and excavation in their vineyard. We thank the ICP Preparation & 590 Conservation Area for tireless preparation of els Casots fossils. Preliminary identification of 591 the fish remains by Tomáš Přikryl (Czech Academy of Sciences, Prague) is much appreciated. 592 We especially thank all the colleagues, students and volunteers that have joined us in the 25 593 excavations: without them this work would not have been possible. We also thank the editors 594 of this special volume for inviting us to contribute to it. The constructive comments by H.-A. 595 Blain, P. Montoya and a third unknown reviewer certainly improved the text. Finally, we 596 want to express our gratitude and admiration to Jorge Morales. Back in 2011, after a visit to 597 els Casots, Jorge spent a whole evening trying to convince some of us to excavate it again. It 598 was a wise advice, as usual coming from Jorge, and we really appreciate it. Thanks, Jorge, for 599 always inspiring and encouraging us. 600 601 Disclosure statement 602 No potential conflict of authors was reported by the authors. 603 604 Funding 605 This publication is part of projects I+D+i PID2020-117289GBI00 funded by 606 MCIN/AEI/10.13039/501100011033/ and CLT009/128/00068 funded by the OSIC 607 (Departament de Cultura, Generalitat de Catalunya). It has also been supported by projects 608 PID2019-106440GB-C21, PID2020-113912GB-100, PID2020-116220GB-I00, PID2020- 609 116908GB-I00 and PGC2018-094122-B-100 all funded by 610 MCIN/AEI/10.13039/501100011033/, as well as by the CERCA Programme and consolidated 611 research groups 2017 SGR 116, 2017 SGR 86, 2017 SGR 596, 2017 SGR 841 of the 612 Generalitat de Catalunya. Additional funding includes: Ministerio de Economía y 613 Competitividad RYC-2013-12470 to I.C.V.; ‘Programa Postdoctoral Beatriu de Pinós de la 614 Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la 615 Generalitat de Catalunya’ 2017 BP 00223 to J.A and 2019 BP 00154 to À.H.L.; NSP 616 (National Scholarship Program of Slovak Republic for the Support of Mobility of University 26 617 Researchers) ID 33758 to S.J.V.; Operational Programme Research, Development and 618 Education - Project "Postdoc@MUNI" No. CZ.02.2.69/0.0/0.0/16_027/0008360 to À.H.L.; 619 Juan de la Cierva Formación fellowship FCI2019-039443 to A.Vi., FJC2018-036669-I to 620 A.Va., and Juan de la Cierva Incorporación fellowship IJC2018-037685-I to A.B. all by the 621 MCIN/AEI/10.13039/501100011033/. A.Va. is also supported by Gobierno de Aragón 622 (research group E33_20R) and by the Universidad Complutense de Madrid and Comunidad 623 Autónoma de Madrid (research group UCM-CAM 910607); C.A. is supported by a Visiting 624 Professor grant of the President’s International Fellowship Initiative of the Chinese Academy 625 of Science and a Grant to the Department of Science, Roma Tre University (MIUR-Italy 626 Dipartimenti di Eccellenza, ART.1, C-314-337 L- 232/2016). 627 628 References 629 Agustí J. 1983. Roedores (Mammalia) del Mioceno Inferior de Can Martí Vell (Vallès- 630 Penedès, Cataluña, España). Estud Geol. 39:417–430. 631 Agustí J, Cabrera L. 1980. Nuevos datos sobre la biozonación del Burdigaliense continental 632 de la cuenca del Vallès-Penedès. Acta Geol Hisp. 15:81–84. 633 Agustí J, Cabrera L, Domènech R, Martinell J, Moyà-Solà S, Ortí F, de Porta J. 1990. 634 Neogene of the Penedès area (Prelittoral Catalan Depression, NE Spain). 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Zitteliana. 14:81–109. 863 Zachos JC, Pagani M, Sloan L, Thomas E, Billups K. 2001. Trends, rhythms, and aberrations 864 in global climate 65 Ma to present. Science. 292:686–693. doi:10.1126/science.1059412 865 38 866 Figures 867 868 Figure 1. a, Panoramic view of the site of els Casots in 2011. Site perimeter is the deforested 869 field behind the vineyards and corresponds to the hatched area in Figure 2. b, Excavated 870 surface after the 2019 field campaign. A metal structure has been built over the main 871 excavation area to protect the site from heavy rains and allow for guided touristic visits. 872 Photograph courtesy of Ajuntament de Subirats. 873 39 874 875 Figure 2. a, Geographical location and general geological context of the Vallès-Penedès 876 Basin showing the location of the study area. b, Detailed geological map of the area around 877 els Casots, showing the location of the fossil site, the electric resistivity profiles, and core 878 samples. Observe the proximity of els Casots to the ancient coal mines as well as its situation 879 directly overlying the Mesozoic basement. Also notice the close proximity of the site to the 880 first Middle Miocene (Langhian) transitional and marine deposits. 881 40 882 883 Figure 3. Geoelectric (ERT) sections 1 and 2. a, ERT section 1 is 585 m long with a direction 884 S170, overlapping 34 m with two ERT profiles, one of 144 m long with an electrode spacing 885 of 2 m, and the other of 475 m and 5 m of electrode spacing. b, ERT section 2 is 355 m with a 886 direction N65 corresponding to a unique ERT profile with 5 m electrodes spacing. Data were 887 acquired with a Syscal-Pro (Iris-Instruments), and the models were obtained with the ResIPy 888 code (Blanchy et al. 2020). Locations of the drilled wells are projected in section 1. White 889 lines show the expected contact between Miocene cover and the basement, whereas the black 890 arrow indicates the point where both profiles intersect. Segments A–D represent resistivity 891 changes interpreted as faulted zones (see text for interpretation). The vertical scale is the 892 topographic elevation above sea level in meters. Section location is shown in Figure 2. 893 41 894 895 Figure 4. Stratigraphic logs of cores Casots A and B (see Figure 2b) and palaeomagnetic 896 inclination from studied samples. Positive inclinations represent normal polarity (in black) 897 and negative inclinations represent reverse polarity (white). Black circles indicate directions 898 of best quality (Quality 1), while white circles indicate directions of lower quality (Quality 2, 899 see text for explanation). Note the long reverse polarity interval in CS-B core. 900 42 901 902 Figure 5. Detailed stratigraphic column of the excavation area (sectors 1 and 2). Capital 903 letters refer to fossiliferous levels. In this sector, levels A–I were almost entirely excavated 904 during the 1990s, so current excavations focus on levels J–M. The levels sampled for 905 micromammals during the 1990s (CS-72, CS-73 and CS-74) are also indicated. 906 43 907 908 Figure 6. Some pictures of the recent field campaigns at els Casots. a, Almost complete 909 mandible of Iberictis buloti (field number CS-150) recovered from level K in 2019. b, Part of 910 a disarticulated hindlimb of Ampelomeryx ginsburgi (field number CS-77) recovered from 911 level J in 2019. From left to right the long bones correspond to a metatarsal, a femur fragment 912 and a tibia. c, Two juvenile hemimandibles of a rhinocerotid (field numbers CS-633 and CS- 913 634) found in level K in 2021. d, Bone accumulation of different elements (mostly ribs and 914 vertebrae) of Gomphotherium cf. subtapiroideum found in level K in 2019. A mandibular 915 fragment with two molars can be observed in the upper left corner (field number CS-325). 916 The whole accumulation of Gomphotherium bones covers a surface of 2 m2. 917 44 918 919 Figure 7. Excavation plans of two fossil accumulations excavated during the 1990s. a, Partial 920 skeleton of Amphicyonidae sp. 1 (larger size) extracted during the 1993 campaign (collection 921 number IPS11428). Observe the anatomical connection of some elements such as the 922 vertebral column (vc) or the cranium and mandible (cr, ma). b, Bone accumulation of two 923 different-sized juvenile ruminant individuals found during the 1994 campaign. The smallest, 924 and more abundantly represented is Eotragus noyei. Although most elements are 925 disarticulated, a few are in anatomical connection, such as vertebrae (v) and phalanges (ppx, 926 mpx, dpx). Collection number for the cranial fragment (cr) of E. noyei is IPS11878. 927 Orientation and exact position of the bone accumulations within the excavation area was not 928 recorded. Anatomical abbreviations: at, atlas; cr, cranium; dpx, distal phalanx; fe, femur; fi, 929 fibula; hu, humerus; ma, mandible; mpx, middle phalanx; mt, metapodial; pl, pelvis; ppx, 930 proximal phalanx; r, rib; ra, radius; sc, scapula; ti, tibia; ul, ulna; v, vertebra; vc, vertebral 931 column. 932 45 933 934 Figure 8. Reconstruction of the fauna and palaeoenvironment of els Casots. In the foreground 935 the felid “Pseudaelurus” lorteti stares at a large amphycionid that has hunted an individual of 936 the suid Eurolistriodon adelli. Behind them, three individuals of the palaeomerycid 937 Ampelomeryx ginsburgi walk away. To their left and in the background, partly hidden behind 938 a palm, there is the cervid Procervulus cf. dichotomus. The crocodylian Diplocynodon ratelii 939 can be seen resting in the lake. In the background, a herd of Gomphotherium cf. 940 subtapiroideum approaches the lake shore. Plant remains at els Casots are too fragmentary, so 941 the reconstructed vegetation is based on that from contemporaneous nearby sites (see Sanz de 46 942 Síria Catalán 2001). Large plants include the palm Sabal and leguminous trees Acacia and 943 Mimosa. Bushes in the foreground are Caesalpinia and Cassia, whereas reeds (Typha) grow 944 abundantly on the lake shore. Palaeoart by Ó. Sanisidro, courtesy of Ajuntament de Subirats. 945 47 946 Table 1. Updated faunal list of the tetrapod assemblage from els Casots. Class Order Family Taxonomic assignment Amphibia Anura Alytidae Latonia sp. Bufonidae Bufotes (group viridis) sp. Ranidae Pelophylax sp. Urodela Urodela indet. Reptilia Testudines Testudinidae Titanochelon sp. Testudo sp. Geoemydidae Ptychogaster sp. Squamata Gekkota indet. Lacertidae cf. Amblyolacerta sp. Lacetidae indet. Scincoidea indet. Anguidae cf. Ophisaurus sp. Pseudopus sp. Varanidae cf. Varanidae indet. Blanidae Blanus sp. Incertae sedis. Scolecophidia indet. Boidae Erycinae indet. Pythonidae Python sp. Colubridae “Colubrinae” indet. Viperidae Vipera sp. (“Oriental vipers”) Viperidae sp. 2 (cf. “European vipers”) Crocodylia Diplocynodontidae Diplocynodon ratelii Aves Galliformes Phasianidae Miophasianus altus Falconiformes Accipitridae cf. Circaetus sp. cf. Aquila sp. Strigiformes Strigidae Strigidae indet. Mammalia Incertae sedis Herpetotheriidae Amphiperatherium frequens Chiroptera Chiroptera indet. Eulipotyphla Erinaceidae Galerix symeonidisi Dimylidae cf. Plesiodimylus sp. Heterosoricidae Heterosorex neumayrianus Soricidae Paenelimnoecus cf. truyolsi Lagomorpha Ochotonidae Lagopsis sp. Rodentia Sciuridae Atlantoxerus idubedensis Heteroxerus rubricati Palaeosciurus sp. Csakvaromys besana Gliridae Bransatoglis sp. Glirudinus modestus Microdyromys monspeliensis Muscardinus sp. Peridyromys murinus 48 Pseudodryomys ibericus Simplomys julii Simplomys robustus Simplomys simplicidens Eomyidae Ligerimys ellipticus Cricetidae Democricetodon hispanicus Democricetodon gracilis Democricetodon sp. 3 Megacricetodon primitivus Carnivora Amphicyonidae Amphicyonidae sp. 1 Amphicyonidae sp. 2 Hemicyonidae Hemicyon stehlini Mustelidae Iberictis buloti Paralutra sp. “Martes” sp. 1 “Martes” sp. 2 Herpestidae Leptoplesictis aurelianensis Hyaenidae cf. Protictitherium sp. Felidae “Pseudaelurus” lorteti Perissodactyla Rhinocerotidae Dromoceratherium mirallesi Rhinoceratidae sp. 2 Equidae Anchitherium sp. Artiodactyla Cainotheriidae Cainotherium miocaenicum Siderochoeridae Choeromorus ibericus Suidae Eurolistriodon adelli Tragulidae “Dorcatherium” crassum Palaeomerycidae Ampelomeryx ginsburgi Lagomerycidae Lagomeryx rutimeyeri Cervidae Procervulus cf. dichotomus Bovidae Eotragus noyei Proboscidea Deinotheriidae Prodeinotherium cf. bavaricum Gomphotheriidae Gomphotherium cf. subtapiroideum 947 948 49