Rivista Italiana di Paleontologia e Stratigrafia volume 104 numero L pagrne 123-130 Aprile 1998 NOA BREVE MIDDLE PLIOCENE CETACEANS FROM MONTE VOLTRAIO (TUSCANY, ITALY). BIO STRATIGRAPHICAL, PALEOECOLOGICAL AND PALEOCLIMATIC OBSERVATIONS GIOVANNI BIANUCCI (*), GIOVANNI SARTI (**), RITA CATANZARITI (***), UBALDO SANTINI (****) Received August 13, 1997; accepted Jarutary 19, 1998 Key-uord;: Odontoceti, Cetacea, Systematics, Stratigraphn Bio- stratigraphy, Paleoecology, Paleoclimatology, Middle Pliocene, Tusca- ny, Ita.y. Riassunto. Viene esaminata la collezione storica di odontoceti (Cetacea) fossili del Monte Voltraio vicino a Volterra (Toscana) e vie- ne condotta un'indagine litostratigrafica e biostratigrafica nella locali- tà di ritrovamento. Laffioramento di Monte Voltraio è attribuito al Pliocene medio, in particolare alle zone a Globorotalia aerniliana e Discoaster tarnalis. I resti di odontoceti vengono riferiti alle famiglie Kogiidae (Kogia pusilLQ e Delphinidae (Globicephala? eturiae e dre reperti indeterminati che potrebbero appartenere a Hemisyntrachelus e a Stenella giulii). La fauna a cetacei del Pliocene medio del bacino Mediterraneo (associazioni di Monte Voltraio e di fuo Stramonte) in- clude taxa estinti o attualmente assenti in questo bacino. La loro scomparsa potrebbe essere messa in relazione ai deterioramenti clima- tici pliocenici e,/o quaternari (per esempio, 1a crisi climatica intorno a 2.6-2.4 MA). Abstact. The historic collection of fossil odontocetes (Cetacea) from Monte Voltraio, near Volterra (Tuscann ltaly) has been exami- ned and lithostratigraphical and biostratigraphical investigations on the find locality have been carried out. The Monte Voltraio outcrop ìs referred to the Middle Pliocene, in panicular to Globorotalia aetni- liana and Discoaster tamalis zones. The odontocete remains are assi- gned to the families Kogiidae (Kogia pusilLa) and Delphinidae (GLobí cephala? etruriae and two indeterminate specimens which might be- long to Hemisyn*acbelus and Stenella gìuli). The Middle Pliocene cetacean fauna from the Mediterranean basin (Monte Voltraio and Rio Stramonte associations) includes extinct tàxa or extant taxa no longer represented in this basin. The disappearance of these raxa may be linked with the Pliocene andlor Quaternary climatic deteriora- tions (e.g. the climatic crisis at *tout 2.6-2.4 M,L). lntroduction. Some historic collections and new finds of fossil cetaceans from Italian Piiocene sediments have recently been examined (Bianucci, 1996a-b, 1997a-c). The new systematic interpretation of these records confirmed a basic renewal of the Mediterranean fauna during the Pliocene with respect to the archaic Miocene cetacean association, already pointed out by Bianucci & Landini (L99I, 1992). These studies also documented the presence du- ring the Pliocene of some extinct taxa or extant taxa no longer represented in the Mediterranean sea. These taxa disappeared from the Mediterranean basin in the course of the Pliocene and/or of the Quaternary. The evolu- tion of these Mediterranean representarives during the last 5 MA is unknown and possible evenrs of extincrion and/or renewal events, at present, are not recognized. This is due to the fact that most of these fossils were collected in the second half of nineteenth century without reliable stratigraphic reference. This paper is a biostratigraphical study aimed to shed new light on the evolution of the Pliocene ceta- ceans of Mediterranean basin. Materials and methods. The four cetacean fossils examined make part of the Lawley Collection, which includes many other ceta- cean remains collected from Pliocene sediments of Tusca- ny (Pilleri, 1987). These specimens are preserved in the Museum of Geology and Palaeontology of the Universi- ty of Florence (IGF). Although incomplete and fragmen- tary these specimens are relatively significant from both a systematic (two of them are the holotypes and the only known records of fossil species) and from a stratigraphi- cal point of view (the fossils are very close in age), These specimens had been collected in the nineteenth century from Pliocene sediments outcropping af "La Rocca", 1o- cality on Monte Voltraio, a hill 458 m above sea level about 2 km east of Volterra (province of Pisa) Fig. t) The systematic analysis of cetacean fossils was completed by a geotrogical and biostratigraphical study of the Monte Voltraio outcrop. A section represenrative of the whole depositional sequence of this area was exa- mined and sampled. Twenty-nine samples were collected for micropaleontological analysis (foraminifera and calca- /'i\ n:-'*:---'^ r: Scienze della Terra, via S. Maria, 53,56126 Pisa (italy). ("'f) Consulting of Emilia Romagna Region, via Amendola, 4,56127 Pisa (Italy). ('r't'f) Consulting of Emilia Romagna Region, via Possenti, 10, 56010 Asciano, Pisa (Ita1y). 1*++t) Via Cristoforo Colombo, 25, 55A49 Viareggio, Lucca (Italy). 1,24 G. Bianucci, G. Sarti, R. Fig. I - Location of Monte Voltraio cetacean assemblage. A : stu- died section. reous nannofossils). The small amount of matrix still preserved on the fossil specimens was also sampled for nannofossils. The abundance of the species ol Discoaster was noted in the samples in which L0 or more specimens of this genus were counted. At the latest 100 specimens were counted in the samples with very abundant Discoa- sfer (Backmann Ec Schakleton, 1983; Rio et al., 1990). The plankrcnic foraminiferal zonal scheme of lac- carino & Salvatorini (1982) followed in other papers concerning the Pliocene sediments of Tuscany (Bossio et a1., L995) was also followed here. The calcareous nanno- fossil zonation is by Rio et aL. (1990). Geological and biostratigraphical setting. The extensional basin of Volterra is filled by rp- per Miocene-Quaternary sequences (Sarti & Testa, 1,994; Bossio et al., 1995). Pliocene deposits outcrop at Monre Voltraio. They consist of grey claystones (called "Pag" on the Foglio 12 of the 1/100,000 National Geological Cartography) at the bottom, and by yellow sandstones at the top. The studied section is exposed to SE, of Mon- te Voltraio; here the succession has an average thickness of 150 m Fig. 2). The first 100 m at the base of the section are grey massive silty claystone. Moving upward the sand content increases rapidly, and after few alterna- ting sand and clay layers yeilow medium-fine sands outcrop at the top of the sequence. Three decimetric le- vels of weil cemented grey bioclastic (bivalves and ga- stropods mainly) calcarenites are present in the upper- most part of the section. The foraminiferal assemblage is suggestive of a transition from an outer-inner neritic zone (basal-medium part of the section) to a littoral zone (upper part of the section). In particular the asso- ciations are diversified and abundant in the samples col- lected from the lowest part of the section (P\B ratio 1\10-1\5). In the samples from the middle and upper part there is a progressive replacement of planktonic fo- raminifers and of benthic taxa from the deepest environ- Catanzariti, U. Santini ments by littoral benthic assemblages. Therefore the sec- tion represents a coarsening and shallowing upward se- quence. The genera Sclpbosphaera and Pontospbaera, both belonging to the family Pontosphaeracae, are parri- cularly well represented in the nannofossil assemblage. These taxa indicate neritic and emipelagic environments (Perch-Nielsen, 1985), which is consistent with the fora- miniferal datum. From a biostratigraphical point of view, the pre- sence in the studied section of Globoroulia crassaformis crassaformis associated wíth Globorotalia bononiensis and Globorotalia aemiliana in the claystone part of the se- quence suggests a reference to the lower part of Globoro, talia crassaformis crassaformis subzone (upper part of Globoroulia aemiliana zone) and therefore this part of sequence is dated Middle Pliocene. The calcareous nannofossil association is referable to the Discoaster tamalis zone. In fact, in the samples where the Discoaster is relatively frequenr, the identified species of this genus (D. swrculus, D. tamalis, D. asymme- tricus, D. brouweri, D. intercalaris, D. pentaradiatus, D. triradiatu) show abundance comparable to those of Di scoaster tamalis zone of the western Mediterranean basin reported by Rio et al. (1990). ZonaI markers are lacking in the upper part of section where littoral conditions are reached. Detailed regional biostratigraphical studies carried out in Tuscany (Bossio et aI., 1995) show that the regressive upper parr of the Pliocene deposits can be entirely included in Glo- borotalia aemiliana zone. The Upper Pliocene deposits (Globorotalia inflata zone) are indeed lacking in Tuscany because of a general uplift of the whole area. The calcareous nannofossil assemblage contained in a sample collected from the sediment preserved on the fossil delphinid IGF 1562V is referable to rhe same zone (Discoaster tamali) identified in the studied section of Monte Voltraio. The samples collected from the sedi- ment on the others fossil cetaceans either are sterile or bear biostratigraphicaly insignificant caicareous nanno- fossil associations. Systematic palaeontology. Class Mammalia Linnaeus, 1258 Order Cetacea Brisson, 1762 Suborder Odontoceti Flower, L867 Family K o g i i d a e (G1ll, 1871) Mìller, 1923 Genus Kogia Gray, 1846 Kogia pusilla (Pilleri, 1987) (Fig. 3ar-az) 1893 Placoziphias, V Beneden - Capellini, pp.287-288. 1,987 Hyperoodon pusillus Pilleri, pp. 35-36, fig. 11, pl. 13. 7997c Kogia pusilla (Pìllert) - Bianucci, pp. 172-173, {tg. 6. 1,25Middle Pliocene cetaceans from Monte Voltraio €. Èrl .--,; T.g NO É- 9X o* rca sÈ òo = ú; '= g 6 dC 2\? É ^r ., o qi ", d >'1, 'E o o b ll"ò ,>tr o'ú tr cÈ- ^Lî,a Ph -- gJH ! e .9 Op >\ o :'^ îu* ú.;1,X tr.tr iÚ' --9X Ào;ì f - = '- N = i àbF" oÒt iú N @ ui o plpln3alund c sllc swolossbJ? S waJjea whalqo J paìroMal sja)sooss p lDloL (tII) SS:{N)I3IHJ Iù & = tsa o z o F z L a fo & a zz z 0661 lo l8 oru +:F òE SINNN 9È 3È I, I NNIl q9 tNNt{ L Oh 9+dd qo a 09 I NNt'.l ;€ s;:v rNîr )g6t ÀrìnB rt opDìO I olll o Zt N 3 z t 1.6 | lu!.p Dt't @ zz r zz -t--zlz zz =z '- ooo o; !@ d dd slè'r bl punal ? | d6 : I qr: I ì È.5 3 I dS : Àhr s"j ruao ounloJoQoln D ?of@?túd o!, lb lo b |o?J ét dÉi €È s1 P{E 3È. 3'G- o ol!c'Pueua 9161 d J L 6 F c O NAÈHJ ssnvc I luSattc ^1 tè\.lod TI rrtrlrtlrtìltttttlll úobo .:dr;+ AHdVUC I.IVUlS O NOUH 3 NVtSVtlgl NVrZr.l]CvraluV:rcruvz fNlcottd t26 G. Bianucci, G. Sarti, R. Catanzariti, U. Santini The skull (IGF1540V) is slightly deformed and lacks of part of the right side and of ventral portion of braincase. This specimen 'was originally referred to a zi- phiid by Capellini (1893) and Pilleri (1987), but actually belongs to the Kogiidae (Bianucci, 1,997c).It represents the only preserved fossil skull of pigmy sperm whale of the genus Kogia. It is the holotype and the only known record of the extinct species Kogia pwsilla (Pilleri, 1987). Kogia pusilla differs from living K. simus and K. breviceps in having a more elongated rostrum, a smaller antorbital process, and an apparently more marked dorsal asymme- try. The posterior portion of the cranium is also slightly more uplifted. A detailed description of this species will appear in a future paper (Bianucci, in preparation). Family D e I p h i n i d a e Gray, 1825 Genus Globiceohala Lesson. 1828 Globicephala ? etruriae (Pilleri, 1987) (Fig. 3br-b3) 7987 GLobicepbala etruriae Pilleri, pp. 28-30, p|. 6. 79961: GLobicepbaLa? etruriae (Pilleri) - Bianucci, pp. 98-99, fig. 33, pl. 9, fig. 3-s . The incomplete mandible lacks the posterior parts of the rami but still bearing 30 teeth in place (IGF 1675V). Pilleri (1982) choose this specimen as holotype of the extinct delphinid species Globicepbala euuriae. This mandible (the only known record of G. etruriae) differs from the mandible of living pilot whales (Globi- cephala melas and G. macrorlrynchu) in its smaller size and in larger number of teeth. The Monte Voltraio fossil may belong, however, to a different genus from that of the two living species (Bianucci, 1996b). Delpbinidae indet. 1987 Tì.trsíops sp. - Pilleri, p. 44. Fourteen complete teeth and seventeen fragments of teeth (IGF 1562V) were referred to Thrsiops sp. by Pilleri (1982), but are morphologically and dimensional- ly similar to the teeth of Hemisyntrachelus, a delphinid which lived in the Mediterranean sea during the Plioce- ne (Bianucci, 1996b, 1997a, 1997b). Isolated teeth are however inadequate for generic determination. Delphinidae indet. 1987 Odontocett Gen. et sp. indet. - Pilleri, pp. 47-48, ftg. 13. Seven cervical and the first two thoracic vertebrae, belonging to of the same animal (IGF 15489, all lack the neural and transverse processes. Pilleri (1987, pp.47- 48) referred this find to "Odontoceti Gen. et sp. indet" (slc). The atlas and the axis are fused and the other cer- vical vertebrae have small and very flatten corpora; the thickness of the corpora increase in the first two thora- cic vertebrae. These vertebrae are illustrated by Pilieri (1.987, fig.13) although he misinterpreted the fused atlas and axis as the first cervical vertebra (and consequently in Pilleri's iliustration there is only one thoracic verte- bra). The atlas is similar to but larger than that of Ste- nella sp. from the Pliocene of Tuscany (Bianucci, 1996b). These vertebrae might belong to the relatively large-size dolphin Stenella giulii, an extinct species repre- sented by only four finds from Pliocene sediments of Orciano (Tuscany). The calcareous nannofossil content of the sediment preserved on three of these fossil speci- mens of Stenella giulii (one, the holotype, has been lost) was analysed. The sediment on one of these specimens (IGF 1541V) contained a biostratigraphically insignifi- cant nannofossil assemblage, while the assemblages of the samples from the other t.wo specimens (MC CF1, IGF i545V) are attributable to the same nannofossil zone (Discoaster tama/i) found in the Monte Voltraio outcrop. These biostratigraphical data support the hypothesis of the presence of Stenella giulii ín the Mon- te Voltraio sediments. Discussion and conclusion" The bathymetric analysis of foraminiferal and nannofossil associations indicate the transition from the inner-outer neritic to the littoral zone. There is an appa- rent discrepancy between the environmental conditions documented by the plankton and the pelagic habitat in- dicate by Kogia and the delphinid near Globicephala. The Recent species of these cetaceans live on the conti- nental siope and feed in the bathyal environment. I-ong drifting of the carcasses from pelagic water to near coast environment may have occurred after death. Prolonged carcass transportation has actually been observed in pre- sent-day cetaceans (Shafer, 1972); such an explanation has already been advocated to explain the odd presence of a fossil pelagic whale in a shallow'water environment (Bianucci, I996a). The odontocete cetacean assemblage from Monte Voltraio can be re{erred to a restricted time span in bio- stratigraphical terms, ranging from approximately 3 to 2.6 lr/.A. This is the same interval in which the clayed marls of Rio Stramonte in Piacenza province were depo- sited (Monegatti & Ranieri, 1987; Monegatti, pers. com.). These clays yielded fossil remains of cetaceans in the past (Bianucci, 1.997b; Cigala Fulgosi, 1990; Del Pra- to, t897,1900). The two associations together shed new light on the Middle Pliocene cetacean fauna of the Me- diterranean basin (Tab. 1). Middle Pliocene cetaceans frorn Monte Voltraio 127 'locm Odontocete remains from Middle Pliocene sediments of Monte Voltraio (Tuscany). ay Kogia pusilla (Pllleri, 1987), incomplete skull in dorsal view; a2, the same in lateral view; br, GLobicephala? eturiae (Prlleri, 1987), incomplete mandible in dorsal view; bz, the same in ventral view; b:, the same in lateral view. Fr : frontrl, La : lacrimal; Mx : Maxilla; N : externàl nares, Pmx : oremaxilla. br 1,28 G. Bianucci, G. Sarti, R Monte Voltraio Rio Stramonte Suborder Odontoceti Family Delphinida Globice phala? etruriae He mi syntrac helus coftesi i Hemisyntrachelus sp. Stenella giulii Family Kogiidae Kogia pusilla Suborder Mysticeti Family Balaenidae Balaena paronai Tab. 1 - Middle Pliocene cetaceans from Monte Voltraio (Tuscanv) and Rio Stramonte (Emilia Romagna). The three families recognized are still living, although two (Kogiidae and Balaenidae) are no longer represented in the Mediterranean sea. The listed taxa include both living (Kogia, Balaena and probably Stenella) and extinct genera (Hentisyntra- cbelws and a delphinid near Globicephala). Kogia and Ba- laena, as are their families, are missing today from the Mediterranean sea. All of these raxa are extinct at the specific levei. These data indicate that the Mediterranean ceta- cean association of Middle Pliocene differed from the extant one in composition and structure. Pliocene and/or Quaternary phases of climatic de- terioration (and consequently changes in water circula- tion, in the water productivity and in the food availabi- lity) might have caused the extinction of some Middle Pliocene cetaceans. The effects of climatic changes and of other correlated factors are already associated with va- riations in cetacean distribution (Barnes, 1974; Davies, 1963; Fordyce, 1980, 1984; Fordyce & Barnes, 1994; Gaskin, 1926; \X/hitmore, 1,994).In particular, food avai- iability seems to have an important control on the structure and composition of cetacean communities (Fordyce, 1996; Lìpps & Mitcheil, 1976). As regards, the co-occurrence of a delphinid near Globicephala and of Kogia (both fed on squids in the bathyal environ- ment) in the Middle Pliocene Monte Voltraio associa- tion, indicate that the teutophag trophic resource was probably larger than that existing today. The analysis of isolated periotics from Lower-Middle Pliocene sediments of Tuscany confirms the presence of kogiids and teutho- phag delphinids (probably Globicephala and Grampus, see Bianucci, 1996lr) in the Mediterranean earlier than the Late Pliocene. Kogia today shows an almost cosmo- politan distribution (Caldwe1l & Caldwell, 1989) and its absence from the Mediterranean might be due to the scarce food supply and to the competition with teutho- phag delphinids (Grarnpus, Globicephala and Pseudorca). The climatic deteriorations in the Mediterranean basin have been dated and calibrated on the basis of ex- Catanzariti, U. Santini tinction events of molluscs (Raffi & Monegatti, 1992; Raffi et al., 1985) and benthic foraminifera (Sprovieri, 1986). A possibie change in the Mediterranean cetacean communities may have occurred at the time of the in- tense climatic crisis which is detected at about 2.6-2.4 MA (approximately correlatable with the upper deposi- tion boundary of Monte Voltraio and Rio Stramonte outcrops). According to Landini Ee Menesini (1988), this climatic deterioration caused the extinction of Bregmace- ros (teleost, fish) from the Mediterranean Basin. This ex- tinction episode of molluscs, foraminifera and fishes has been correlated with the first major glacial event of the northern hemisphere (Thuneil & Williams, 1983). A better calibration of cetacean extinction events with and climatic changes will be possible when syste- matic and biostratigraphical studies of other Mediterra- nean cetacean assemblages (particularly from the Late Pliocene and Quaternary) are carried out. Acknouledgements. \le are grateful to P. Mazza (Museo di Geologia e Paleontologia, University of Florence) for grating us access to the Monte Voltraio cetacean collectron and for revising the English. Many thanks to \7. Landini (Dipartimento di Scienze della Terra, University of Pisa) for the interesting discussions. 'We also wish to thank D. J. Bohaska (U.S. National Museum) for critically reading rh" -".".".i.t REFERENCES Backman J. & Shackleton N.J. 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