Bollettino della Società Paleontologica Italiana, 49 (3), 2010, 203-225. Modena, 15 dicembre 2010203

The Upper Miocene fossil fish locality of Pecetto di (, ): a multidisciplinary approach

Jean Gaudant, Marie-Denise Courme-Rault, Eliana Fornaciari & Elisabeth Fourtanier

J. Gaudant, 17 rue du Docteur Magnan, F 75013 Paris, France (Muséum national d’Histoire de la Terre, USM 203, UMR 7207 CNRS); jean.gaudant@ orange.fr M.-D. Courme-Rault, 6 rue Porte vendomoise, F 45190 Beaugency, France; [email protected] E. Fornaciari, Dipartimento di Geologia, Paleontologia e Geofisica, Università di Padova, via Giotto 1, I 35137 Padova, Italia; [email protected] E. Fourtanier, Diatom Collection, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118-4599 (USA); EFourtanier@ calacademy.org

Key words - Fishes, Micropalaeontology, Stratigraphy, Palaeoenvironment, Upper Miocene, Piedmont, Italy.

Abstract - Pecetto di Valenza is the first Upper Miocene fossil fish locality of Piedmont to have been studied and the only one in which fossils are embedded in a diatomitic sediment. Sturani & Sampò (1973) considered that it is Messinian in age. However, as a preliminary examination of the diatom flora from this locality by one of us (Elisabeth Fourtanier) suggested a late Tortonian age, it was decided to complete a more thorough micropalaeontological study in order to clarify the stratigraphical question. A comprehensive study of the diatom flora confirmed the preliminary results. Later, the study of the calcareous nannoplankton also concluded a late Tortonian age for the fossiliferous diatomaceous sediment. However, the examination of the planktonic foraminifera supports a Messinian correlation. Such a contradiction is puzzling and is hitherto not understood, even when making reference to a possible reworking. The composition of the fish fauna from Pecetto di Valenza is very similar to that observed in the two other marine Upper Miocene fish faunas of Piedmont, as myctophids predominate in all of them with more than 50% of the total number of specimens, whereas clupeids belonging to the species Alosa elongata comprise about 20% of the fauna. Except for the two species of the genus Lepidopus which, together, reach almost 8%, each one of the other identified taxa is below 5% of the fish fauna. The occurrence of upwellings, which is indicated by the abundance of the diatom Thalassionema nitzchioides in every diatomaceous sample, may have been responsible for the rather significant percentage of Lepidopus in the fish fauna. However, the upwelling environment did not exert any notable influence on the overall composition of the fish fauna from Pecetto di Valenza, relatively to those of the Tortonian of the Tanaro River and of the pre-evaporitic Messinian of Roddi, two localities in which diatoms are missing.

Riassunto - [La località a pesci del Miocene Superiore di Pecetto di Valenza (Piemonte, Italia): uno studio multidisciplinare] - Pecetto di Valenza è il primo sito a pesci fossili del Miocene Superiore del Piemonte ad essere stato studiato. Inoltre è l’unico in cui i fossili sono inclusi in sedimenti diatomitici. Sturani & Sampò (1973) li hanno considerati di età messiniana. Tuttavia l’analisi preliminare dell’associazione a diatomee di questa località da parte di uno di noi (Elisabeth Fourtanier) suggeriva un’età tortoniana. Perciò, al fine di chiarire la posizione stratigrafica di questo sito, è stato condotto uno studio micropaleontologico con anche altri gruppi. Lo studio definitivo dell’associazione a diatomee ha confermato i risultati preliminari. In seguito anche lo studio dell’associazione a nannofossili calcarei ha permesso di concludere che i sedimenti diatomitici hanno un’età attribuibile alla parte alta del Tortoniano. Al contrario le analisi dell’associazione a foraminiferi planctonici supportano la correlazione con il Messiniano di Sturani & Sampò (1973). Questa contraddizione è inspiegabile e finora non è stata compresa. La composizione della fauna di pesci di Pecetto di Valenza è molto simile a quella osservata nelle due altre faune a pesci del Miocene Superiore del Piemonte. In tutte i myctophidi predominano con più del 50% sul totale del numero di esemplari mentre i clupeidi appartenenti alla specie Alosa elongata sono circa il 20% della fauna. A Pecetto di Valenza, ad eccezione di due specie del genere Lepidopus che insieme raggiungono l’8%, ciascuno degli altri taxa identificati costituisce meno del 5% della fauna a pesci. La percentuale piuttosto significativa di Lepidopus nella fauna a pesci potrebbe essere imputabile alla presenza di upwelling indicata dall’abbondanza, in tutti campioni analizzati, della diatomea Thalassionema nitzchioides. In ogni caso il confronto tra la composizione della fauna a pesci fossili del fiume Tanaro (Tortoniano) e di Roddi (Messiniano pre-evaporitico), due località in cui le diatomee sono assenti, con quella di Pecetto di Valenza indica che quest’ultima, globalmente, non è stata influenzata in maniera significativa dall’upwelling.

Introduction Proatlanta sp., lepadids: Lepas sp., portunid crabs: Necronectes sp., as well as juvenile oysters (2 to 15 mm More than thirty years ago, Carlo Sturani described long): Ostrea cf. neglecta Michelotti, 1847, fixed on a new fish fauna collected in the vicinity of Pecetto di driftwood or, exceptionally, on a drifted shell of a cuttlefish Valenza (Fig. 1), after a landslide which had occurred near (specimen MRSNP 35/140). Cascina Valnera, in the Upper Miocene of the Eastern part In his study of the fish fauna from Pecetto di Valenza of the Montferrato hills ( province) (Sturani & - the material collected by him is kept in Torino, in the Sampò, 1973). According to Sampò, who had studied the palaeontological collection of the University (PU) - foraminifera, the locality was supposed to be Messinian Sturani identified eleven (a number which is here reduced in age. to ten) different species: The material had been collected in diatomitic layers - Family Clupeidae: Alosa elongata Agassiz, 1843; by Carlo Sturani and Mario Macagno who observed in - Family Gonostomatidae [=Sternoptychidae]: Mauro- the sediment the occurrence of pteropods: Cavolinia licus gregarius Franceschi, 1922 [= M. muelleri gypsorum Bellardi, 1873, heteropods: Atlanta or (Gmelin, 1789)];

ISSN 0375-7633 204 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Fig. 1 - Map of the surroundings of Alessandria (Eastern Piedmont) showing the location of Pecetto di Valenza.

- Family Myctophidae: Myctophum microsoma (Sauvage, 1870) [= M. licatae (Sauvage, 1870) plus, pro parte, M. dorsale (Sauvage, 1870)] and M. edwardsi (Sauvage, 1870) [= M. licatae (Sauvage, 1870)]; - Family Syngnathidae: Syngnathus albyi Sauvage, 1870; - Family Merluccidae: Merluccius merluccius (Linnaeus, 1758); - Family Caproidae: cf. Capros aper (Linnaeus, 1758) [= Percoidei indet.]; - Family Trichiuridae: Lepidopus proargenteus Arambourg, 1927; - Family Carangidae: Trachurus trachurus (Linnaeus, 1758); - Family Soleidae [= Bothidae]: Microchirus abropteryx (Sauvage, 1870) [= Arnoglossus abropteryx (Sauvage, 1870)].

Additionally, Sturani noted that one species of myctophids, Myctophum microsoma (Sauvage, 1870), is the most frequent. He also noted that this fish community mainly includes nectonic fishes and considered that the lack of littoral species is indicative of a sedimentation taking place at some distance from the shore, in the upper part of the bathyal zone, at a depth comprised between 200 and 400 or 500 metres, under influence of upwellings which were producing waterblooms of diatoms. New excavations were carried out in 1981 in the same area - more precisely near Cascina Guarnera, at about 1 km S-SE of Pecetto di Valenza - by Giulio Pavia and Mario Macagno, assisted by Daniele Ormezzano. Consequently, a total amount of more than two hundred fishes specimens became available for study. The newly collected material is kept in Torino, in the Museo Regionale di Scienze naturali del Piemonte (MRSNP). Additionally, a section Fig. 2 - Lithostratigraphical section of the strata excavated in 1981 of about seven metres of sediment (Fig. 2) was sampled (from Pavia, 1989, modified). The numbers to the right indicate the on this occasion (Pavia, 1989). position of the samples collected for micropalaeontological studies. J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV 205

Although it is impossible to know if Sturani’s and comparison the diatoms of a fish specimen collected at Pavia’s excavations were carried out, or not, exactly in Pecetto di Valenza by Oreste Cavallo, from the Museo the same part of the diatomitic sequence which is more or civico “F. Eusebio” of Alba, during Sturani’s excavations: less exposed near Cascina Guarnera, the composition of in fact, she unexpectedly concluded that the diatom flora the two fossil fish associations exhibit the same general of this sample is not Messinian but Tortonian (Fourtanier composition. The main difference between them results et al., 1991). from the occurrence of scombrids in the material collected during Pavia’s excavation. The quantitative study of the composition of both fossil Micropalaeontological study of populations is completed by a comparison with those from the section sampled in 1981 the Tortonian of the Tanaro bed near Alba (Gaudant et al., 2007) and from the pre-evaporitic Messinian of Roddi Diatoms (Gaudant et al., 2008). (Fig. 3; Pl. 1) The diatom flora was examined by Elisabeth Fourtanier who studied the samples collected during Pavia’s Methods - Samples (ca. 1cc) were boiled in HCl excavations. Additionally, Eliana Fornaciari examined and H2O2. The residues were rinsed by diluting them the calcareous nannoplankton whereas Marie-Denise in distilled water and decanting off excess liquid after Courme identified the foraminifera. A stratigraphical at least 12 hours of settling. This cycle was repeated 3 problem arose when Elisabeth Fourtanier studied for times. Strewn slides were prepared by sampling a fraction

Fig. 3 - Diatom occurrence chart at Pecetto di Valenza, and stratigraphical range of selected taxa. First and Last occurrence ages are based on data from the Pacific Ocean according to: 1: Barron (2003); 2: Barron (1976, updated). A= abundant, C= common, F= few, R= rare; LOD: Last occurrence datum; FOD: First occurrence datum; LCOD: Last common occurrence datum. 206 Bollettino della Società Paleontologica Italiana, 49 (3), 2010 of the suspended residue with a pipette and spreading it that the stratigraphical range of these stratigraphic markers on a cover slip that was air-dried and mounted on a slide is similar between the Mediterranean and the Pacific with Hyrax. Ocean. The last occurrence datum (LOD) and the first For each sample an entire slide was scanned under occurrence datum (FOD) in the Pacific Ocean for selected the light microscope at 1000x power. Relative abundance species (Barron 1976, 2003) are indicated in Fig. 3. of each taxa is reported (Fig. 3) as A (abundant), C The occurrence of Denticulopsis simonsenii (Last (common), F (few) and R (rare). common occurrence - LCO - around 8.6 Ma in all areas except Antarctica) and the occurrence of Thalassiosira Results - Samples 1, 2 and 9 are devoid of diatoms. brunii (LO 9.0 Ma) suggest an age older than 9.0 Ma. The Samples 3-8 (55 cm-165 cm) yielded a well preserved and occurrence of Actinocyclus ellipticus f. lanceolata (FO abundant diatom flora. 10.5 Ma) and the absence of Actinocyclus moronensis (LO 9.8 Ma) suggest an age younger than 9.8 Ma. The other Palaeoecology - The diatom assemblages from Pecetto stratigraphic markers present in the section are supporting di Valenza are dominated by Thalassionema nitzschioides, an age of about 9.0-9.8 Ma (Tortonian) for the section of which is abundant in every sample. Chaetoceros resting Pecetto di Valenza. spores are also frequent in levels 3 and 4. Denticulopsis In addition, we note that the diatom flora is simonsenii (mostly in sample 3, 6, 7) and Coscinodiscus characteristically lacking definitive Messinian diatoms spp. are fairly common. The assemblages are typically such as those recorded at Masseria il Salto (Gaudant et oceanic with very few neritic species (e.g. Actinoptychus al., 1996) or Capo Rossello (Schrader & Gersonde, 1978). senarius). Messinian diatoms absent at Pecetto include Nitzschia Thalassionema nitzschioides is a cosmopolitan miocenica (FO 7.3 Ma), Thalassiosira praeconvexa (FO planktonic species that is found in oceanic and coastal 6.7 Ma) and Thalassiosira convexa var. aspinosa (FO 6.6 environments. The abundance of Thalassionema Ma). Furthermore, we note the absence of species that nitzschioides seems to correspond to highly productive could be characteristic of the uppermost Tortonian, such oceanic environments (Sancetta, 1992). Chaetoceros as Thalassiosira burckliana (FO 9.0 Ma), Nitzschia fossilis are abundant in areas of coastal upwelling (Schuette & (FO 8.9 Ma), Alveus marina (FO 7.9 Ma) and Nitzschia Schrader, 1981). reinholdii (FO 7.6 Ma) (Barron, 2003). The base of the The diatom flora at Pecetto is indicative of a highly Messinian has been astronomically dated at 7.251 Ma productive oceanic environment. The influence of a (Hilgen et al., 2000). coastal upwelling may be reflected in samples 3 and 4. The assemblage from Pecetto di Valenza resembles that described by Schrader (in Berggren et al., 1976) Age of the deposit - Stratigraphical markers (e.g. at El Cuervo (Andalusia, Spain) and that of the upper Denticulopsis simonsenii, Thalassiosira brunii, diatom sedimentation episode studied by Bustillo and Thalassiosira grunowii, Nitzschia porteri) occur in the López Garcia (1997) in the Guadalquivir Basin of Spain, section. The stratigraphical range of these markers have suggesting that diatom deposition occurred between ca. been well documented and directly correlated with the 9.0 to 9.8 Ma in at least parts of the Mediterranean. palaeomagnetic scale in the Pacific Ocean (Burckle, 1972; Barron, 1976, 2003; Shackleton et al., 1995). Previous studies in the Mediterranean Neogene (e.g. Burckle, Calcareous nannofossils 1976, 1978; Gersonde, 1980; Gersonde & Schrader, 1984; (Fig. 4) Monjanel, 1987; Gaudant et al., 1996) demonstrate that the diatom zonation established in the Pacific Ocean is Methods - Nine samples were prepared from applicable in the Mediterranean area. We therefore accept unprocessed material as smear slides and examined

EXPLANATION OF PLATE 1

Selected diatoms from Pecetto di Valenza.

Figs. 1-3 - Denticulopsis simonsenii (sample 6). Figs. 4-5 - Nitzschia porteri (sample 6). Fig. 6 - Rouxia californica (sample 6). Fig. 7 - Thalassiosira flexosa (sample 8). Fig. 8 - Rhizosolenia miocenica (sample 6). Fig. 9 - Thalassiosira flexosa (sample 6). Fig. 10 - Thalassiosira cf. gersondei (sample 6). Fig. 11 - Dimmerogramma sp. 1 of Schrader & Gersonde, 1978 (sample 7). Fig. 12 - Nitzschia praereinholdii (sample 6). Fig. 13 - Thalassiosira grunowii (sample 6). J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.207 1 208 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Helicosphaera% N/mm2 >7μm Cretaceous taxa reworked Paleogene taxa reworked Diatoms Sample H. carteri H. pacifica/orientalis H. stalis H. euphratis H. recta Discoaster brouweri Discoaster hamatus Discoaster variabilis Minylitha convallis R. pseudoumbilicus

9 84 10 6 0 0 0 0 2 4 35 P P Fig. 4 - Distribution of 8 47.17 14.15 37.73 0 0.94 0 0 2 1 37 P A selected calcareous nannofossil 7 66 4.8 29.26 0 0 1 0 0 0 16 P P taxa at Pecetto di Valenza. Countings: relative abundance 6 56.2 6.6 37.14 0 0 0 0 0 2 9 A of helicoliths species on 100 5 81 3.8 13.5 0.96 0 5 0 10 0 7 P counted helicoliths. Number of discoasterids on 6-7 mm2. 94.4 0.9 4.7 0 0 0 0 30 0 10 C C A 4 Number of Reticulofenestra 3 91 2 5 2 0 0 0 1 0 10 A pseudoumbilicus and Minylitha 2 2 83 4 13 0 0 6 0 24 5 4 convallis on 1 mm . A: Abundant; C: Common; D: 1 80 6 14 0 0 5 1cf. 25 7 8 P P Dominant; P: Present; cf.: REWORKED compare to.

using a light microscope at 1250x magnification. it displays an interval of reduced presence or virtual After a preliminary qualitative analysis to evaluate the absence (Paracme) starting from the base of MNN10a abundance and the state of preservation of calcareous (Raffi et al., 2003) at ca. 8.8 Ma (Raffi et al., 2006). nannofossil assemblages, the following quantitative Therefore, the concomitant occurrence of common R. and semiquantitative counting methods (Backman & pseudoumbilicus and H. stalis allows an assignment of the Shackleton, 1983; Rio et al., 1990) have been applied in Pecetto di Valenza section to the calcareous nannofossil order to check the presence or absence of index species: zones MNN8b-MNN10. Additionally, the presence of Minylitha convallis makes possible a correlation of the 1) Counting the number of biostratigraphically useful strata with an interval ranging from the upper part of zone species in an area of about 1 mm2 (Reticulofenestra MNN9 to the top of MNN10 (cf. Raffi et al., 2003, fig. pseudoumbilicus, Minylitha convallis); 1). Hence, on the basis of the stratigraphical distribution 2) Counting a prefixed number of taxonomically related of R. pseudoumbilicus, M. convalllis and H. stalis the age forms, i.e., 100 helicoliths (Rio et al., 1990); of the Pecetto section is Tortonian and ranges from the 3) Counting the number of rare but biostratigraphically upper part of zone MNN9 to the top of MNN10 of Raffi useful species in an area of about 6-7 mm2 (2-3 vertical et al. (2003) (Fig. 4). traverses), i.e. discoasterids.

Results - With the exception of sample 9, all the other Foraminifera ones contain common calcareous nannofossils, having a (Figs. 5-6) rather good state of preservation. The results are shown in Fig. 4. Reworked Cretaceous and Palaeogene taxa are Methods - All the samples being more or less marly, present in almost every sample, and are fairly common they were washed with water to which hydrogen peroxide in the sample 4. The other samples exhibit similar had been added. Then the sediment was sifted with three associations in which dominate placoliths and helicoliths. sifters having meshes of 0.500, 0.250 and 0.125 mm. The genus Discoaster is generally poorly represented Finally, the foraminifera were examined under a binocular and the marker species (e.g. Discoaster hamatus and D. microscope. pentaradiatus) are virtually absent (Fig. 4). Minylitha convallis is present (from rare to scarce) in samples Results - According to the composition of the 1, 2, 6, 8 and 9. Helicoliths are common. Especially, foraminiferal associations, the Pecetto section can be Helicosphaera stalis is present in all samples (Fig. 4). subdivided into four members. Among placoliths, Reticulofenestra pseudoumbilicus is always common. 1) The sample Pecetto 1 can be distinguished from the following ones by the abundance of the foraminifera. Age of the sediments - Helicosphaera stalis is widely Although no planktonic marker was found in this level, distributed throughout the Tortonian (from zone MNN8b this planktic foraminifera association points toward a to zone MNN11a of Fornaciari et al., 1996 and Raffi et Tortonian age. Benthic foraminifera, very diverse in al., 2003) while Reticulofenestra pseudoumbilicus ranges species and numerous in samples, indicate an environment from the Middle Miocene to the Early Pliocene, although which was favorable for their growth. Most species J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV 209

characterize an open sea oxygenated environment, normal salinity waters, and circalittoral to infralittoral conditions, on a muddy bottom. Bulimina, Brizalina, Bolivina and Uvigerina proliferated in an environment rich in organic matter. The existence of surface currents can explain the presence of genera living in water plant communities (Biasterigerina or Elphidium), which are very scarce, and probably carried away from their habitat by down slope transport.

2) The appearance of the planktonic taxa Globorotalia humerosa and Globigerinoides eamesi in samples Pecetto 2 and 3, followed by that of Globorotalia suterae in the sample Pecetto 4, argue for a Messinian age. The large variety of planktonic species is remarkable in these three levels; however, this does not apply to benthic foraminifera. It seems that depositional conditions changed and were no longer as favorable for benthic foraminifera as in Pecetto 1. Species of open sea and normal salinity waters are scarce or absent (such as Uvigerina for example). Genera living in water plant communities are more frequent (Biasterigerina, Cibicides, Elphidium). Species supporting dysoxic and salinity increases (Bolivina, Brizalina, Rectuvigerina, Hopkinsina) Fig. 5 - Distribution of the planktic foraminifera throughout the are predominant and associated to species supporting section of Pecetto di Valenza sampled by Pavia (1981). suboxic conditions (Cancris, Gyroidina, Cassidulina). The bottom remains muddy.

Fig. 6 - Distribution of the benthic foraminifera throughout the section of Pecetto di Valenza sampled by Pavia (1981). 210 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

3) From Pecetto 5 to 8, planktonic foraminifera conditions on the bottom, as suggested by Van Hinsbergen remained diverse and well represented. The Globorotalia et al. (2005). humerosa-Globigerinoides eamesi association, along with Globorotalia suterae and additionally with G. conomiozea Note - During this study, we have mainly used the data (Pecetto 7) is always present and therefore indicates a published by Berggren et al. (1995), Bolli, Saunders & Messinian age. Benthic foraminifera show few variations Perch-Nielsen (1985), Betzler et al. (2006) and Hüsing et in their contents in comparison with Pecetto 2 to 4; al. (2009) for determining the stratigraphical distribution however, intervals which are poor in benthic foraminifera of the planktic foraminifera, whereas we have taken into (Pecetto 6 and 8) alternate with levels where they are still consideration the publications by AGIP (1982), Murray rather well represented (Pecetto 5 and 7). Genera living (1973, 1991), Van der Zwaan (1979) and Zachariasse in sea plant communities are present, such as forms & Spaak (1983) for interpreting the environmental supporting suboxic conditions (Cancris, Pullenia) or significance of the benthic fauna. dysoxy and salinity increases (Rectuvigerina, Hopkinsina, Hanzawaia). The bottom remained muddy. The presence of Uvigerina may suggest sporadic incursions of waters The fish fauna having a normal salinity. (Figs. 7-10; Pls. 2-6; Tab. 1)

4) Depositional conditions observed in the sample The present description of the Upper Miocene fish Pecetto 9 are similar to those of Pecetto 1. The planktic fauna from Pecetto di Valenza relies on the bulk of material foraminifera belong to the association Globorotalia collected, first by Carlo Sturani, Giulio Pavia and Mario humerosa - G. praemargaritae (the second one scarce) and Macagno and, later, by a team composed of Giulio Pavia, include Globigerinoides eamesi, indicating a Messinian Mario Macagno and Daniele Ormezzano (Table 1). age. Among benthic foraminifera, genera living in sea plant communities are less numerous at the species level, as well as those supporting dysoxy and salinity increases Family Clupeidae Cuvier, 1817 (Hopkinsina). On the other hand, the abundance of the Genus Alosa Linck, 1790 four species of Uvigerina, indicates a close relation to an open sea environment. Associated to Bulimina, Brizalina Alosa elongata Agassiz, 1843 and Bolivina, they characterize again an environment rich (Pl. 2, figs. 1-2) in organic matter. The bottom remained muddy. Discussion - This species is represented by 18 Interpretation - The associations of planktic specimens (15.3%) in the material collected by Sturani, foraminifera observed in the samples 2 to 9 are indicative and by 31 (25%) in the newly collected material. It is rather of a Messinian age. Moreover, they look rather similar to well known from an anatomical point of view since its those described by Wernli (1980) from the Messinian of description by Arambourg (1927), which was completed the Mediterranean coast of Morocco. However, although more recently for fishes from the Upper Miocene of Globorotalia humerosa and Globigerinoides eamesi are the surroundings of Alba (Gaudant et al., 2007, 2008). frequent at Pecetto di Valenza, Globorotalia suterae, G. The characteristic shape of the preoperculum and the conomiozea and G. praemargaritae are less common. operculum is shown in Pl. 2, fig. 1. Additionally, the From a palaeoenvironmental point of view, the ventral surface of an isolated neurocranium exhibiting fossiliferous layers correspond to a sedimentation taking the two pterotic bullae and the left prootic one is also place in a quiet area of the circalittoral zone which was figured (Pl. 2, fig. 2). disturbed from time to time by surface currents, as shown The standard lengths of the examined specimens by the important number of foraminifera normally living range from 107 to 175 mm in Sturani’s collection (with in sea plant communities. Additionally, the fact that, the exception of a larger fish reaching 280 mm), whereas except in the sample Pecetto 1, the benthic foraminifera it ranges from 69 to 215 mm in the material collected in are unfrequent, may be related to the occurrence of dysoxic 1981, except for a larger fish reaching 284 mm.

EXPLANATION OF PLATE 2

Fossil fishes from the Upper Miocene of Pecetto di Valenza.

Fig. 1 - Alosa elongata (Agassiz). Head. Specimen MRSNP 35/08. Fig. 2 - Alosa elongata (Agassiz). Neurocranium. Specimen MRSNP 35/30. Fig. 3 - Maurolicus muelleri (Gmelin). Specimen MRSNP 35/32b. Fig. 4 - “Myctophum” licatae (Sauvage). Specimen MRSNP 35/58b. Fig. 5 - “Myctophum” licatae (Sauvage). Specimen PU 12 463 (Sturani’s collection). J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.211 2 212 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Tab. 1 - Composition of the Upper Miocene fish fauna from Pecetto di Valenza. The study was managed separately for the Sturani’s collection belonging to the Torino University and for the material collected in 1981 under the leadership of Pavia for the Museo Regionale di Scienze naturali del Piemonte. Note: The specimen of Solea cf. solea was kept in the private collection of the late Mario Macagno.

Family Sternoptychidae Duméril, 1806 Messinian throughout the Mediterranean basin in which Genus Maurolicus Cocco, 1838 it was dominant in many localities. It is also the case at Maurolicus muelleri (Gmelin, 1789) Pecetto di Valenza as 103 specimens were collected: 61 (Pl. 2, fig. 3) by Sturani (51.7% of the collected material) and 42 in 1981 (33.9% of this material). These percentages can be Discussion - Maurolicus muelleri is a species which compared to those observed in the Tortonian of the Tanaro is well known in the Messinian of the Mediterranean River (43.4%) and in the Lower Messinian of Roddi (40%) basin. It was first described as Clupea gregaria and then (Gaudant et al., 2007, 2008). as Sahelinia gregaria by Arambourg (1925, 1927) in the This species is well known through its description by Messinian of Licata (Sicily) and later of Oran and Sidi Arambourg (1925, 1927) who distinguished two other Brahim (Algeria). Additionally, a detailed description of species that we consider as synonyms of Myctophum this species was published by Landini & Menesini (1980). licatae: Myctophum microsoma (Sauvage, 1870) and Ten specimens were collected at Pecetto di Valenza. Four Myctophum edwardsi (Sauvage, 1870) (Gaudant & belong to Sturani’s collection (3.4% of the collected Ambroise, 1999). material), whereas six were found in 1981 (they constitute The standard lengths of the specimens range from 10.5 4.8% of the material found at that time). to 61.5 mm, whereas the maximum frequency is observed As shown by Fig. 14, their standard lengths range between 10 and 50 mm (Fig. 14), to be compared with from 10.5 to 35.5 mm. It may be noted that the specimens a maximum frequency between 30 and 55 mm in the having a standard length exceeding 30 mm were collected Tortonian of the Tanaro River and 40 and 65 mm in the in 1981. pre-evaporitic Messinian of Roddi. This indicates that young specimens were rather more abundant at Pecetto di Valenza. Family Myctophidae Gill, 1893 Genus “Myctophum” Rafinesque, 1810 (s.l.) “Myctophum” licatae (Sauvage, 1870) “Myctophum” dorsale (Sauvage, 1870) (Pl. 2, figs. 4-5) (Pl. 3, figs. 1-3)

Discussion - Myctophum licatae is a species which Discussion - The second species of myctophids is already well known as it was widespread during the identified at Pecetto di Valenza is quite less abundant than

EXPLANATION OF PLATE 3

Fossil fishes from the Upper Miocene of Pecetto di Valenza.

Fig. 1 - “Myctophum” dorsale (Sauvage). Specimen MRSNP 35/80. Fig. 2 - “Myctophum” dorsale (Sauvage). Specimen MRSNP 35/87. Fig. 3 - “Myctophum” dorsale (Sauvage). Same specimen: enlargement showing the photophores (arrows). J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.213 3 214 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Myctophum licatae. Only six specimens were found by isolated operculum was found at Pecetto di Valenza in Sturani (5.1% of the collected material) and 11 in 1981 1981 (Pl. 4, fig. 1). It is an ovoid bone bearing a reticulate (8.9% of the fish number). This species differs from ornamentation. Its length equals about 1.5 time its height. Myctophum licatae (Sauvage) by their thicker scales and the possession of rather large light organs. Their standard lengths range from 15.5 to 40 mm. The percentage of Suborder Percoidei Bleeker, 1859 representatives of this species at Pecetto di Valenza is Percoidei indet. similar to what is known in the Tortonian of the Tanaro (Pl. 5, figs. 1-3) River and in the Messinian of Roddi (Gaudant et al., 2007, 2008), but the size of the specimens is slightly smaller at Discussion - At least five indetermined small percoids Pecetto di Valenza. were collected at Pecetto di Valenza. Three were found by Sturani. One of them (PU 12355/1 and /2; Pl. 5, fig. 1) was tentatively determined by him as “cf. Capros aper Family Merluciidae Adams, 1864 (L.)”. However, this juvenile fish is indicated as being Genus Merluccius Rafinesque, 1810 only 9 mm long, against 14 mm for the specimen here figured which is labelled in this collection “cf. Capros Merluccius merluccius (Linnaeus, 1758) aper (L.)” (Pl. 5, fig. 1). It has a height of body which is almost half of its standard length. This specimen differs Discussion - Sturani & Sampò (1973, pl. I, fig. 1) from Capros aper (Linnaeus, 1758) in having both shorter described and figured a well preserved specimen of spines in the first dorsal fin and longer ones in the anal fin. Merluccius merluccius. This specimen (PU 12373/1 and Additionallly, its operculum is wider when compared to /2) has a standard length of 155 mm and a maximum height the narrow operculum of Capros aper so that this specimen of body measuring 30 mm. The dorso-ventrally crushed cannot be assigned to the genus Capros Lacepède, 1803. head of another fish (PU 12349) can be assigned to the A second juvenile percoid fish was collected by Sturani same species. Additionally, the caudal region of a larger (PU 12473; Pl. 5, fig. 2). It has also a rather thick-set body fish (MRSNP 35/99), which is covered by small cycloid as its body height reaches 4 mm for a standard length of scales ornamented with ovoid circuli, was found in 1981. 10 mm. It is mainly characterized by its convex skull As already emphasized by Sturani & Sampò (1973), it roof outline. The length of the spines of its dorsal fin is was the first time that the genusMerluccius was recorded clearly shorter than that which can be expected for the from the diatomitic Upper Miocene of the Mediterranean genus Capros. basin. A third specimen (PU 12474; Pl. 5, fig. 3) strikingly differs from the preceding ones. It has a standard length of 9 mm. This juvenile fish cannot be assigned to the genus Family Syngnathidae Bonaparte, 1832 Capros as it has an elongate body, which has a maximum Genus Syngnathus Linnaeus, 1758 height included four times in standard length, and also dorsal fin spines which are quite shorter, as well as an anal Syngnathus albyi Sauvage, 1870 spine which is quite smaller than those of Capros aper. (Pl. 4, fig. 1; Pl. 6, fig. 1)

Discussion - This species is represented by fifteen Family Carangidae Rafinesque, 1815 specimens in the studied material. Six were found by Genus Trachurus Rafinesque, 1810 Sturani (5.1% of his collection) against nine collected in 1981 (7.3%). Their standard length (measured or Trachurus trachurus (Linnaeus, 1758) estimated) ranges from about 260 to 500 mm. This species, which is widely distributed in the Upper Miocene Discussion - This species is only represented by a small of the Mediterranean basin, was already described by specimen which is preserved in part and counterpart (PU Arambourg (1925, 1927). In Piedmont, it is also present 124471/1 and /2). It was described and figured by Sturani in the Tortonian of the Tanaro River and in the Lower & Sampò (1973, pl. II, fig. 1). Its standard length does not Messinian of Roddi (Gaudant et al., 2007, 2008). An exceed 40.5 mm for a maximum depth of body of 11.5

EXPLANATION OF PLATE 4

Fossil fishes from the Upper Miocene of Pecetto di Valenza.

Fig. 1 - Syngnathus albyi Sauvage. Left operculum. Specimen MRSNP 35/107b. Fig. 2 - Lepidopus sp. Right premaxillary deprived of its long fangs. Specimen PU 17808 (Sturani’s collection). Fig. 3 - Lepidopus proargenteus Arambourg. Head of specimen MRSNP 35/109. Fig. 4 - Lepidopus proargenteus Arambourg. Caudal fin of specimen MRSNP 35/109. J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.215 4 216 Bollettino della Società Paleontologica Italiana, 49 (3), 2010 mm. Although this specimen is still rather juvenile, a parhypural articulates with the terminal centrum, whereas, series of characteristic scutes is present along the anterior dorsally, one long epural is present. The caudal fin is not part of the lateral sensory line in the upper part of the preserved. abdominal region. The first dorsal fin is missing, except for its posterior pterygiophores. The posterior dorsal fin is imperfectly preserved: two unbranched rays are present in front of Family Scombridae Rafinesque, 1815 the fin; behind them, the number of branched rays was of Genus Sarda Cuvier, 1829 about six. The endoskeleton was apparently composed of seven pterygiophores. At least five or six - and possibly up Sarda sp. to eight - pinnules were present behind the posterior dorsal (Pl. 5, fig. 4) fin; they articulate with rather strong pterygiophores. The anal fin, which was rather small, begins behind Discussion - Two small specimens collected in 1981: the posterior dorsal fin. Although it is poorly preserved, it MRSNP 35/119a+b (Pl. 5, fig. 4) and 35/120 a+b, the seems to have been supported by at least six pterygiophores. standard length of which is only 42 and 44 mm, bear At least five or six - and possibly up to seven - pinnules witness of the occurrence of this species at Pecetto di were present behind it. They are supported by robust Valenza. Their body is elongate, the maximum height pterygiophores similar to those supporting the dorsal of which is included five to six times in standard length. pinnules. The vertebral column comprises at least 36 vertebrae, 19 of which are postabdominal. The vertebral centra bear Taxonomical interpretation - The lack of the anterior long neurapophyses and haemapophyses. The thin pleural part of the body, especially of the head and of the first ribs are about 15 pairs; the posterior ones articulate with dorsal fin makes difficult a precise taxonomical assessment vertebral parapophyses, the length of which increases of this fossil. However, the relative position of the second backwards. dorsal fin and of the anal fin and the probable number The caudal fin is deeply forked; it is supported by of pinnules behind them (higher than five) show that it three vertebral centra which are quite shorter than the does not belong to the genus Scomber Linnaeus. On the preceding ones. The posterior triangular centrum supports contrary, both characters agree with those of the genus two triangular hypural plates which are not yet fused Sarda Cuvier. together as in adults.

Family Trichiuridae Rafinesque, 1810 Genus Sarda Cuvier, 1829? Genus Lepidopus Gouan, 1870

Sarda? sp. Lepidopus proargenteus Arambourg, 1927 (Pl. 5, fig. 5) (Fig. 7; Pl. 4, figs. 2-4; Pl. 6, fig. 2)

Discussion - The posterior part of a rather large fish Discussion - Sturani & Sampò (1973) noted that indicates the occurrence of another scombrid fish (MRSNP eight specimens of Lepidopus had been first collected 35/12; Pl. 5, fig. 5) at Pecetto di Valenza. It shows at Pecetto di Valenza: six were assigned to the species the posterior part of the abdominal region, especially L. proargenteus and two to L. albyi. In fact, Sturani’s the posterior pleural ribs and a rather well preserved collection really includes 11 more or less incomplete postabdominal region which is composed of 19 vertebrae. specimens and three isolated premaxillaries. Additionally, Among them, 16 have elongate centra which are bearing six specimens were found in 1981 during the excavations long arched neural and haemal apophyses. Posteriorly, carried out by Giulio Pavia and Mario Macagno. the caudal axial skeleton includes two shortened centra Although no diagnostic character is visible on it, bearing rather strong neural and haemal apophyses and except its size, as its height of body measures 38 mm, a a triangular terminal centrum which is fused with a body fragment was figured by Sturani & Sampò (1973, very wide triangular hypural plate in front of which the Tav. II, fig. 4) asL. proargenteus (PU 12356). One of the

EXPLANATION OF PLATE 5

Fossil fishes from the Upper Miocene of Pecetto di Valenza.

Fig. 1 - Percoidei indet. Specimen PU 12355/1 (Sturani’s collection). This specimen was wrongly considered by Sturani as belonging to the genus Capros). Fig. 2 - Percoidei indet. Specimen PU 12473 (Sturani’s collection). Fig. 3 - Percoidei indet. Specimen PU 12474 (Sturani’s collection). Fig. 4 - Sarda sp. Specimen MRSNP 25/119a. Fig. 5 - Sarda? sp. Specimen MRSNP 35/123. J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.217 5 218 Bollettino della Società Paleontologica Italiana, 49 (3), 2010 premaxillaries (PU 17808) was figured later by Landini & Sorbini (1980). This premaxillary (Pl. 4, fig. 2), which is lacking its two long fangs, is exposed by its lateral surface. Its oral edge was bearing about thirty acute teeth of moderate size. Among the material excavated in 1981, only three (out of eight) specimens can be determined at the species level. All belong to the species Lepidopus proargenteus. One of them (MRSNP 109; Pl. 4, figs. 3-4; Pl. 6, fig. 2) is a complete specimen reaching 695 mm in standard length with a height of body measuring 30 mm. Its vertebral column consists of 145 vertebrae: 45 abdominal - against 35-36 in Lepidopus albyi according to Arambourg (1925) - and 100 postabdominal. The head shows the premaxillary which is provided with two strong fangs (Fig. 7), the dentary, the oral edge of which bears a series of sharp Fig. 7 - Lepidopus proargenteus Arambourg. Fang borne by the premaxillary of specimen MRSNP 35/113. teeth of moderate size. The operculum has undergone a 90° rotation. Its posterior outline is lacerated. The small caudal fin (Pl. 4, fig. 4) seems to have consisted of about six rays and was apparently paddle shaped. This unusual morphology of the caudal fin suggests that this species Pecetto di Valenza cannot be determined at the species was possibly intermediate between the other species of level. The fact that many of them are rather small or Lepidopus which have a forked caudal fin composed of moderate in size may suggest that they generally belong 15 furcated principal rays and the recent apodous genus to Lepidopus albyi, although there are necessarily among Trichiurus Linnaeus. Although the dorsal fin is not totally them young representatives of Lepidopus proargenteus. preserved, it seems to have been composed of about 138 rays, as indicated by the pterygiophores supporting the missing rays. The composition of the anal fin is unknown Family Bothidae Regan, 1910 as it is partly destroyed. Genus Arnoglossus Bleeker, 1862 The second incomplete large specimen (MPSNP 114/1 and /2) lacks the caudal region. According to the size of its Arnoglossus sauvagei (Capellini, 1878) head, its estimated standard length reached about 880 mm. The third specimen corresponds to the head and the Discussion - The unique specimen of Heterosomata forepart of the abdominal region of a very large fish. (PU 12374) found by Sturani at Pecetto di Valenza is a According to the size of its head which is 150 mm long, juvenile (18.5 mm in standard length) which was wrongly its standard length may be estimated about 1250 mm. Its described and figured by Sturani & Sampò (1973, Tav. II, premaxillary bears a very large fang having a small notch fig. 6) asMicrochirus abropteryx (Sauvage). In fact, this on its posterior edge (Fig. 7). specimen has a vertebral column which is composed of about 36 vertebrae, 27 or 28 of which are postabdominal, whereas Microchirus abropteryx has only 27 vertebrae: 9 Lepidopus albyi (Sauvage, 1870) abdominal and 18 postabdominal.

Discussion - The occurrence at Pecetto di Valenza of a second species of the genus Lepidopus is indicated by Family Soleidae Norman, 1931 specimen PU 12366, in which are preserved the remains Genus Solea Quensel, 1806 of a rather small head with a premaxillary bearing a fang, the posterior edge of which is smooth, without notch. Solea cf. solea (Linnaeus, 1758)

Discussion - Landini (1982) described as Solea cf. Lepidopus sp. vulgaris (Quensel) a specimen having a standard length of 73 mm, which had been collected at Pecetto di Valenza Discussion - Except for the five specimens described by the late Mario Macagno. It is an elongate fish bearing above, all the other specimens of Lepidopus found at the eyes on the right side, having a standard length of 73

EXPLANATION OF PLATE 6

Fossil fishes from the Upper Miocene of Pecetto di Valenza.

Fig. 1 - Syngnathus albyi Sauvage. Specimen MRSNP 35/102. Fig. 2 - Lepidopus proargenteus Arambourg. Specimen MRSNP 35/109. Fig. 3 - Archaeotetraodon bannikovi Carnevale & Tyler. Specimen MRSNP 35/125. J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV Pl.219 6 220 Bollettino della Società Paleontologica Italiana, 49 (3), 2010 mm. Its maximum height of body is included three times in the standard length. The vertebral column includes 42 vertebrae: 8 abdominal and 34 postabdominal. There are about 70 rays in the dorsal fin and 62 in the anal fin. The composition of the vertebral column and of the dorsal and anal fins of this specimen support its attribution to the genus Solea and the existence of a direct relationship with the recent species Solea solea, from which it differs only by the composition of its dorsal fin which seems to have several rays less than the recent species.

Family Tetraodontidae Bonaparte, 1832 Genus Archaeotetraodon Tyler & Bannikov, 1994

Archaeotetraodon bannikovi Carnevale & Tyler, 2010 (Figs. 8-10; Pl. 6, fig. 3)

Discussion - The family Tetraodontidae is represented at Pecetto di Valenza by a unique rather large specimen Fig. 9 - Archaeotetraodon bannikovi Carnevale & Tyler. Caudal (MRSNP 35/125), the standard length of which reaches axial skeleton of specimen MRSNP 35/125. Hy 3+4: upper hypural about 345 mm. This specimen has recently been described plate; PU 1+U 1+Hy 1+2: uro-terminal complex fused with the lower hypural plate; PU 2: first free preural centrum. by Carnevale & Tyler (2010) who designated it as the holotype of a new species: Archaeotetraodon bannikovi. For this reason, we give only here a short description of this specimen (MRSNP 35/125) which was collected in the premaxillary is indented for allowing the articulation 1981. with the symmetrical premaxillary. About six compressed, The head, which is partly disarticulated, shows leaf-like teeth are present on the dentary. A triangular the ventral surface of the neurocranium on which the operculum is fossilized at some distance above the parasphenoid is preserved. The premaxillary is present in neurocranium. front of the neurocranium. It bears about ten teeth which The vertebral column is composed of about 20 are distributed in two main rows whereas one additional vertebrae having rather robust and elongated centra. The tooth is present ventrally (Fig. 8). The symphysal edge of third and the fourth centra bear triangular neurapophyses which are flattened, whereas the following neurapophyses are not.

Fig. 8 - Archaeotetraodon bannikovi Carnevale & Tyler. Toothed Fig. 10 - Archaeotetraodon bannikovi Carnevale & Tyler. Bifurcated premaxillary of specimen MRSNP 35/125. spinules borne by the scales of specimen MRSNP 35/125. J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV 221

The caudal fin, which is paddle shaped, is composed of real agreement exists between the results obtained with about 11 main rays, nine of which are furcated. Its length diatoms and calcareous nannoplankton which clearly equals about one quarter of standard length. It is supported indicate a Tortonian age, and those deduced from the by a remarkably specialized posterior centrum (PU 1+U foraminifera which suggest a Lower Messinian age (Fig. 1) which is fused with the lower hypural plate (Hy 1+2), 11). This discrepancy cannot hitherto be explained. whereas an upper hypural plate (Hy 3+4) articulates with The separate study of the two collections made first by it (Fig. 9). Sturani and then, in 1981, by Pavia has evidenced small The dorsal and anal fins, which are more or less differences in the composition of the collected material opposed, are situated near the middle of the body. Their (Tab. 1; Fig. 12). composition is unknown. The first pterygiophore of the The most important difference concerns the percentage dorsal fin points horizontally forwards. of myctophids: 61.0%, including 51.7% of Myctophum The body is covered with many bifurcated spinules licatae in the first one, against 46.8% and only 33.8% of which are well preserved in front of the dorsal (Fig. 10) Myctophum licatae in the second one. On the contrary, and anal fins. Alosa elongata is less abundant (15.3%) in Sturani’s collection than in the material collected in 1981 (25.0%). It should also be noted that Lepidopus remains are more Conclusion abundant in Sturani’s collection (9.3%) than in the newer material (6.5%) (Fig. 12). The micropalaeontological study of the fossiliferous These small differences suggest that the excavations sediments from Pecetto di Valenza has shown that no did not take place exactly in the same part of the diatomitic series outcropping near Pecetto di Valenza (as suggested by the fact that, according to Sturani, at the place first excavated, the fossiliferous level was only three metres

Fig. 11 - Stratigraphical interpretation of the diatomitic sediments Fig. 12 - Comparison of the fish associations from Pecetto di Valenza of Pecetto di Valenza taking into account the ages provided by three successively collected by Sturani and Pavia. a: Sturani’s excavations; different micropalaeontological studies. b: Pavia’s excavations (1981). 222 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Fig. 13 - Comparison of the global fish fauna from Pecetto di Valenza with those from the Tortonian of the Tanaro River and the pre-evaporitic Messinian of Roddi. a: Tanaro River (Tortonian); b: Pecetto di Valenza; c: Roddi (Messinian). thick, although the diatomitic series is obviously quite Myctophum licatae are predominant in them: 42.6% thicker). of the collected material at Pecetto di Valenza, 43.4% Considering the bulk of material collected during in the Tortonian of the Tanaro River and 40.0% in the both excavations, it is possible to compare the fish pre-evaporitic Messinian of Roddi, while the percentage fauna from Pecetto di Valenza with those which were of myctophids reaches 53.7% at Pecetto di Valenza, recently described in the Upper Miocene of the vicinity against 51.8% in the Tanaro River and 45.0% at Roddi. of Alba (Gaudant et al., 2007, 2008). A great similarity Additionally, the second most abundant species is Alosa exists between these three fish faunas (Fig. 13), as the elongata, with more than 20.0% in these three localities: myctophids and especially those belonging to the species 20.2% at Pecetto di Valenza, 22.9% in the Tortonian of J. Gaudant et al. - The Upper Miocene fossil fish locality of Pecetto di alenzaV 223

Fig. 14 - Histogram of measured or estimated standard lengths of the teleostean fishes collected at Pecetto di Valenza. the Tanaro River and 20.7% at Roddi. The third most Alosa elongata ranges from 69.5 to 284 mm, with important component of the fish fauna from Pecetto a majority of specimens between 100 and 165 mm. di Valenza is the genus Lepidopus, represented by two This may be compared to the situation known in the species which, together, reach 7.9% of the collected Tortonian of the Tanaro River in which we have observed material, to be compared with 6.0% observed in the specimens ranging from 125 to 260, and even 282 mm Tortonian of the Tanaro River. and in the pre-evaporitic of Roddi: specimens having a If we consider now the standard length of the fishes, standard length ranging from 105 to 135 mm, a majority another striking similarity also exists between the three of specimens being included between 105 and 135 mm. localities (Fig. 14). At Pecetto di Valenza, the species Taking into consideration the Myctophum licatae from 224 Bollettino della Società Paleontologica Italiana, 49 (3), 2010

Pecetto di Valenza, their standard length ranges from Berggren W.A., Kent D.V., Aubry, M.-P. & Hardenbol J. (eds.): 10.5 to 61.5 mm, the majority of them being situated Geochronology time scale and global stratigraphic correlation. between 10 and 50 mm. This situation is to be compared SEPM Spec. Publ., Tulsa, Oklahoma, 54: 129-212. Betzler C., Braga J.C., Martín J.M., Sánchez-Almazo I.M. & with those observed in the Tortonian of the Tanaro Lindhorst S. (2006). Closure of a seaway: stratigraphic record River: standard length ranging from 34.5 to 118 mm and and facies (Guadix basin, Southern Spain). International highest frequence between 30 and 55 mm, and in the Journal of Earth Sciences (Geologische Rundschau), 95: pre-evaporitic Messinian of Roddi: standard length from 903-910. 21 to 72 mm, with the highest frequence between 40 and Bolli M., Saunders J.B. & Perch-Nielsen K. (1985). Plankton 65 mm. Consequently, the main difference between these stratigraphy. Cambridge University Press, 1032 pp. Burckle L.H. (1972). Late Cenozoic planktonic diatom zones from three populations of Myctophum licatae is the slightly the eastern Equatorial Pacific. In Simonsen, R. (ed.), First smaller size observed at Pecetto di Valenza in which the Symposium on Recent and Fossil Marine Diatoms. Beihefte very young specimens are more abundant. zur Nova Hedwigia, 39: 217-246. To conclude, as already emphasized by Gaudant & Burckle L.H. (1976). Time-relations of diatoms in the neostratotype Cavallo (2008), the main difference existing between the Messinian. Abstract. Messinian Seminar n° 2, Gargnano, 1976, fish fauna from Pecetto di Valenza and the two other ones Università di Parma: 30. from the marine Upper Miocene of Piedmont depends Burckle L.H. (1978). Diatom biostratigraphy of Unit 2 (Tripoli) of the neostratotype Messinian. Rivista Italiana di Paleontologia mainly on the nature of the fossiliferous sediments as, e Stratigrafia, 84: 1037-1050. at Pecetto di Valenza, the fish fauna is preserved in a Bustillo M.A. & López García M.J. (1997). Age, distribution and diatomitic sediment including upwelling markers instead composition of Miocene diatom bearing sediments in the of being preserved in more or less marly sediments totally Guadalquivir Basin, Spain. Geobios, 30 (3): 335-350. devoid of diatoms which have yielded the fish fauna Carnevale G. & Tyler J. (2010). Review of the fossil pufferfish genus from the Tortonian of the Tanaro River and from the pre- Archaeotetraodon (Teleostei, Tetraodontidae), with description of three new taxa from the Miocene of Italy. Geobios, 43 (3): evaporitic Messinian of Roddi. 283-304. Fornaciari E., Di Stefano A., Rio D. & Negri A. (1996). Middle Miocene quantitative calcareous nannofossil biostratigraphy in the Mediterranean region. Micropaleontology, 42 (1): 37-63. Acknowledgements Fourtanier E., Gaudant J. & Cavallo, O. (1991). La diatomite de Castagnito (Piémont): une nouvelle preuve de l’existence The first author is greatly indebted to Franca Campanino Sturani d’oscillations modérées du niveau marin pendant le Messinien and Daniele Ormezzano (Museo regionale di Storia naturale del évaporitique. Bollettino della Società Paleontologica Italiana, Piemonte, Torino) for assistance during the preparation of the present 30: 79-95. study and for the loan of the figured specimens. He also does not forget Gaudant J. & Ambroise D. (1999). Réexamen critique des that a first attempt to solve the stratigraphical question had already been Myctophidae messiniens de Licata (Sicile, Italie): conséquences made, more than ten years ago, in collaboration with Maria Romeo and taxinomiques. Cybium, 23 (2): 131-145. Agata Di Stefano (Università di Catania). John Barron (US Geological Gaudant J., Caulet J.-P., Di Geronimo I., Di Stefano A., Fourtanier E., Survey) is warmly acknowledged for providing precise information Romeo M. & Venec-Peyré M.-Th. (1996). Analyse séquentielle concerning the stratigraphical distribution of diatom species identified d’un nouveau gisement de poissons fossiles du Messinien marin at Pecetto di Valenza, and Jim Tyler (National Museum of Natural diatomitique: Masseria il Salto près de Caltagirone (Province History, Washington) for his help in determining the tetraodontid fish. de Catane, Sicile). Géologie méditerranéenne, 23: 117-153. Joël Dyon and Denis Serrette (Paris) respectively prepared the Gaudant J. & Cavallo O. (2008). The Tortono-Messinian fish faunas figures and photographed the fossils. of Piedmont (Italy) and the Adriatic trough: a synthesis dedicated to the memory of Carlo Sturani (1938-1975). Bollettino della Società Paleontologica Italiana, 47 (2): 177-189. References Gaudant J., Cavallo O., Courme-Rault M.-D., Fornaciari E. & Lauriat-Rage A. (2008). Palaéontologie du gisement de poissons AGIP (S.p.A.) (1982). Foraminiferi padani. Atlante iconografico e fossiles du Messinien préévaporitique de Roddi, près d’Alba distribuzione stratigrafica. a2 ed., 128 pp. (Piémont, Italie). Rivista Piemontese di Storia Naturale, 29: 3-60. Arambourg C. (1925). Révision des poissons fossiles de Licata Gaudant J., Cavallo O., Courme-Rault M.-D., Fornaciari E., (Sicile). Annales de Paléontologie, 14: 37-132. Lauriat-Rage A. & Merle D. (2007). Paléontologie des marnes Arambourg C. (1927). Les poissons fossiles d’Oran. Matériaux tortoniennes affleurant dans le lit du Tanaro, près d’Alba pour la Carte géologique de l’Algérie, 1re série: Paléontologie, (Piémont, Italie). Rivista Piemontese di Storia Naturale, 28: 6: 291 pp. 3-51. Backman J. & Shackleton N.J. (1983). Quantitative biochronology Gersonde R. & Schrader H.J. (1984). 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