TAPIR REMAINS IN PARAI,IC DEPOSITS OF PLIOCENE AGE IN LOWER VAI,I)AR O

(TUSCANY., ITALY) : FACIES ANALYSIS AND TAPHONOMY

STEFANO DOMINICI, LORENZO ROOK, MARCO BENVENUTI & LAURA ABBAZZI

DOMINICI S., ROOK L., BENVENUTI M. & ABBAZZI L. 1995. Tapir remains in paralic deposits of Pliocene age in Lower Valdarno (Tuscany, Italy) : facies analysis and taphonomy. [Restes de tapir darts des d~pSts paraliques d'~ge phoc~ne dans le Valdarno inf~rieur (Toscane, Italie) : analyse de facies et taphonomie]. GEOBIOS, M.S. 18 : 131-135.

ABSTRACT

Remains of two specimens of Tapirus arvernensis, a young adult and a juvenile, were recovered in paralic deposits of Pliocene age in lower Valdarno. Facies analysis of the succession bearing such remains has been carried out through the study of sedimentary structures and molluscan assemblages. The results of this study show that the two tapirs died and were buried in an interdistributary, very shallow-water bay.

KEY-WORDS : FACIES ANALYSIS, TAPHONOMY, PARALIC DEPOSITS, PLIOCENE, TUSCANY, ITALY.

RI~SUMI~

Des restes de deux specimens de Tapirus arvernensis, un adulte et un jeune, ont ~t~ recuefllis dans des d~p6ts paraliques du Plioc~ne dans le Valdarno inf~rieur. L'analyse de facies de la succession a ~t~ effectu6e en ~tudiant les structures s~dimentaires et la faune de mollusques. Cette ~tude a montr~ que les deux tapirs ont ~t4 conserves dans les d~p6ts d'une bale tr~s peu profonde off ils sont morts.

MOTS-CL]~S : ANALYSE DE FACIF.S, TAPHONOMIE, D~.POTS PARALIQUES, PLIOC]~NE, TOSCANE, ITALIE.

INTRODUCTION

Fossilization of terrestr ia l mammal faunas in pa- ralic deposits seems more than a rare chance : coastal environments such as lagoons, interdistri- butary bays or tidal flats are in fact suitable pla- ces for preservat ion of bone material (Frey et al . 1975 ; Weigelt 1989). The present paper reports on the finding of tapi r remains in Pliocene depo- sits from a shel tered-bay paleoenvironment. Sedi- mentary, taphonomic and paleoecologic analyses allow to make some speculations on the occur- rence of such remains.

GEOLOGICAL SETTING

The Casenuove outcrop is located on the flanks of a clay quar ry about 2 km south of Empoli (lower Valdarno, central Italy) (Fig. la). The outcrop dis- plays a 60 meters- thick Pliocene succession made

of terrigenous sediments arranged in a cyclic or- der. Cycles are fining-upward and are charac- terized by basal coarse sands from lowstand flu- vial settings, transgressive fine sands and silty clays from shoreface and lagoonal environments and highstand silts and sands with hummocky cross stratification (HCS) from open shelf set- tings. Each cycle is in terpre ted as a depositional sequence (sensu Vail et al. 1977). Four sequences have been recognized on the outcrop, arranged in a transgressive trend.

During the winter of ].993, some amateurs of the "Gruppo Paleontologico C. De Giuli" of Castelfio- rentino found and part ial ly recovered the re- mains of two specimens of Tapirus arvernensis, a young adult and a juvenile, in the highstand de- posits of the third sequence.

Tapirus arvernensis is a species tha t charac- terizes the Ruscinian and early Villafranchian

Florence

IArno rtver ~ ' ~ " ~ ' O - - . - -

~ s t / i e P ° * l l sit "J e

I t e x t - f i g " la

SB: sequence boundary

TS: transgressive surface

MFS: maximum flooding surface

5m LST: Iowstand

systems tract

TST: transgressive systems tract

HST: hlghstand systems tract

t e x t - f i g , lb 0m

5B

T A P l R U 5

Mrs

T5

132

Helletds

Btttlum-JujUbtntts assemblage

5trlarca lactea ass. shark teeth

Ostrea vmlett -

5crob~cularta Diana assemblage

. . . . . TS Pitar subgtgantea

assemblage T5

5S

Turrltella beds

r- o=

COASTAL PLAIN

BAY

OPEN LAGOON

8A~qRIER AND LAGOON

5HOREFACE

BRAIDED RIVER?

INNER SHELF

~n

- r

I-- (/3

LSI

V)

Figure 1 - a, location map ; b, vert ical sect ion of the Case- nuove sequence . S e e text for explanat ion, a, localisation gdographique du site ; b, co- lonne stratigraphique de la succession de Casenuove. Voir le texte pour l'explication.

land m~mmal ages of western Europe (corretata- ble with the lower Pliocene). Its last occurrence is reported at the transition from the Triversa fau- nal unit to the Montopoli f.u (early Villafran- chian) (Azzaroli et al. 1988 ; Torte et al. 1992).

DESCRIPTION AND INTERPRETATION

The sequence where the tapirs were found is about 15 m thick and shows proximal characters with respect to the underlying sequences. At the base it is formed by a coarse deposit unconforma- bly overlying sandy silts with Turritella vermicu- laris beds and HCS (Fig. lb). The basal deposit is characterized by coarse sands with high-angle cross stratification and lags of clay chips, wood fragments and abraded molluscan remains. It is interpreted as a lowstand deposit of fluvial origin cutting through shelf deposits. The first trans- gression is marked by fine and medium well-sor- ted sands with a transported fossil assemblage characterized by Pitar subgigantea, an extinct ve- neriid that lived in sandy bottoms of upper shore- face paleoenvironments. Above these sediments

we find horizontal-lsminated fine and very fine sands laterally adjacent to laminated and biotur- bated silts with Scrobicularia plana and Ostrea virleti. S. plana is characteristic of lagoonal set- tings (Guelorget & Perthuisot 1983) and allows to interpret this part of the sequence as a transgres- sive barrier-and-lagoon deposit. A ravinement surface tops the lagoonal deposits, marked by a thin veneer of shell debris, overlain by l~minated fine sands and bioturbated silts. These are char- acterized by a more diversified molluscan fauna with Striarca lactea, Solen marginatus, Scrobicu- laria plana, Conids, Chamelea amidei, and by shark and ray teeth. This deposit marks the maximum deepening reached during the deposi- tion of the sequence and the top of the Transgres- sive Systems Tract. Early highstand deposits are made of silty sands with a Bit-tium reticulatum assemblage. Here was found Tapirus arvernensis. We interpret this part of the section as an inter- distributary bay deposit formed in a deltaic set- ting. Progradation continued through the deposi- tion of silts with caliche paleosoils and sparse pulmonate gastropod remains from a coastal subaereal paleoenvironment.

Bittium bed

Ostrea bed

TAPIRUS REMAINS

scattered Bittium and root traces

Cerastoderma bed

Figure 2 - Schematic section of the interdistributary bay depo- sits. Scale bar is in dins. Section schgmatique d~ d~p6ts de baie. L~chelle verticale est en din.

A detailed s tudy of early highstand deposits and faunas allowed a bet ter understanding of the pa- leoenvironment where the two Tapirus arvernen- sis specimens were to find their burial. These de- posits are 110 cm-thick and are homogeneous from the sedimentary point of view (Fig. 2). In the lower par t is a shell pavement made of the valves of juvenile Cerastoderma edule, a bivalve typical of lagoonal settings. None of the speci- mens reached adult size and all have about the same size, showing that environmental conditions were not suitable for the species to reach adul- thood. Sparse Bittium reticulatum and Jujubu- nius exasperatus specimens can be found above the Cerastoderma bed and below an Ostrea edulis bed. The deposits are bioturbated and plant root traces occur. Tapirus was found few centimeters below the Ostrea bed, together with scattered crustacean remains. Two samples, immediately above and below the Tapirus remains, have been analyzed and both showed a very similar micro- faunal composition : big specimens of the benthic foraminifera Ammonia beccarii and Elphidium crispum, ostracods and sparse Bittium reticula- turn. Other foraminifera were in minor amounts.

About 20 centimeters above the Ostrea bed is a laterally-continuous shell bed, characterized by huge amounts of the small gastropod Bittium re- ticulatum, accompanied by less abundant Mitrel- la sp. and Jujubinus exasperatus.

We envisage that the depositional environment did not change much during the early highstand. The structure of the benthic community, as re- vealed by the shelled fauna, remains constant throughout the deposition of this part of the se- quence. This is characterized by the small herbi-

133

vorous gastropods Bittium and Jujubinus and by the foraminifera Ammonia and Elphidium, also living on plant leaves. Filter feeders are only lo- cally important, namely along the Ostrea bed. Carnivores are represented by sparse Mitrella sp. and crustaceans. The preserved par t of the com- muni ty thus shows a simple trophic web mainly made by pr imary producers (plants) and primary consumers (herbivores) and with sparse first level carnivores. Some deposit feeders were probably responsible of the extensive bioturbation but were not recovered among the shelled fauna.

Some autoecologic remarks can be made about Bittium reticulatum and Jujubinus exasperatus, for these two species are still living in the Medi- terranean. They are today particularly abundant on the stems of those algae that grow in very shallow waters and tha t often reach the water surface, as Cystoseira (Ried] 1991).

There are no signs of brackish water conditions and we interpret the environment as an interdis- t r ibutary bay connected with the open sea but close to river mouths from which it received abundant organic matter. Water was probably very shallow.

TAPIR US AR VERNENSIS

Most of the bones recovered are at tr ibutable to the adult specimen, while the juvenile one is rep- resented only by a few deciduous teeth.

The exploiting activity going on in the quarry probably lead to the lost of some of the remains. The skull and mandibles of the adult specimen were recovered in the ditch aside the in-situ re- mains.

The adult skeleton is almost complete. Some parts are in anatomical connection : ulnae and radii, tibiae and fibulae, right tarsus, left III and IV metatarsal , some thoracic vertebrae. A few re- mains are slightly displaced from the anatomical connection, e.g. right tarsus and metatarsus . Some hydraulical reorientation of the bones can be perhaps envisaged in the disposition of long axes along two directions at right angles (Fig. 3).

The remains show no sign of weathering (cf. Behrensmeyer 1978 ; Hill 1980), nor signs of subaereal scavenger activity of the type described by Behrensmeyer & Dechant Boaz (1980), Hill (1980) and Brain (1981). These two last evidences suggest that the remains have not been exposed above the water level. The lack of traces of sub-

134

. . . . . " : , o o o

Figure 3 - Schematic plan of the site showing distribution of tapir skeletal remains (IGF 4884V). The dotted area represents the ditch. L = lower deciduous teeth, U = upper deciduous teeth. Plan sch4matique de la distribution des restes de tapir. L'aire couverte de points reprgsente le canal d'drosion. L = dentition de lait infdrieur, U = dentition de lair supdrieur.

marine bioerosion and incrustation suggests a re- latively quick burial.

DISCUSSION

The results of our study show a coherent picture : the two tapirs died in an environmental setting no t dissimilar to their habitat. Tapirs live in fact in hllmid or under-water terrains, eating aquatic vegetation and covering their body with mud to protect themselves from the tropical weather and from insects (cf. Grassd 1955 ; Walker 1964). An interdistributary, very shallow-water bay could offer to these animals such conditions. The lack of signs of significant lateral displacement of the bones are furtherly in favour of a "life position" interpretat ion of these terrestrial fossils.

CLOSING REMARKS

M~mmal faunas have been frequently found in Pliocene paralic deposits of the lower Valdarno of Tuscany, forming sometimes important faunal units for continental correlations (Azzaroli 1977). Our s tudy shows tha t a modern approach to fur-

ther findings requires an integrated analysis of the entombing deposits through sedimentology, taphonomy and, in the case of paralic paleoenvi- ronments, benthic paleoecology. Careful integra- ted studies (cf. Behrensmeyer, 1991) can in fact provide case histories for taphonomic models, check the degree of resedimentation of the re- mains and, in the case of findings in paralic de- posits, eventually establish correlations with the marine record.

Acknowledgements - The manuscript was critically read by Profs. Danilo Torre and Ernesto Abbate. Work supported by M.U.R.S.T. and C.N.R. grants.

REFERENCES

AZZAROLI A. 1977 - The Villafranchian Stage in Italy and the Plio-Pleistocene boundary. Giornale di Geo- logia, ser. II, 41 : 61-79.

AZZAROLI A., DE G:UL: C., FICCARELLI G. & TORRE D. 1988 - Late Pliocene to early mid-Pleistocene mam- mals in Eurasia : faunal succession and dispersal events. Palaeogeography , Palaeocl imatology , Pa- laeoecology, 6 : 77-100.

135

BEHRENSMEYER A.I~ 1978 - Taphonomic and ecologic informat ions from bone weather ing . Paleobiology, 4: 150-162.

BEHRENSMEYER A. K - 1991 - Ter res t r i a l Ver tebra te Accumulat ion. In ALLISON P~A. & BRIC, GS D.E. (eds) Taphonomy Releasing the Data Locked in the Fossil Record, Plenum Press , New-York : 291-335.

BEHRENSMEYER A . K & DECHANT BOAZ D.E. 1980 - The recent bones of Ambosel i park , Kenia, in re la t ion to eas t Afr ican paleoecology. In BEHRENSMEYER A. K & HILL A. (eds.) : Fossils in the making, Butzer and F r e e m a n Edi tors , Chicago : 72-92.

BRAIN C.I~L 1981 - The Hunters or the Hunted, The Univer s i ty of Chicago Press, Chicago.

FREY R.W., VOORHIES H. & HOWARD J.D. 1975 - Es- tua i res of the Georgia Coast , U.S~k. : Sedimentolo- gy and Biology. VIII . Fossi l and Recent ske le ta l re- ma ins in Georgia es tuai res . Senckenbergiana Mari- tima, 7 : 257-295.

GRASSE P.P. 1955 - Traitd de Zoologie. Anatomie, Sys- tdmatique, Biologie. Masson et Cie, Edi teurs , Par is , 17, 1 : 1-1170.

GUELORGET O. & PERTHUISOT J.P. 1983 - Le domaine para l ique . Travaux Laboratoire Gdologie, Paris, 16 : 1-136.

HILL A.P. 1980 - Ea r ly pos t -mor tem damage to the re- ma ins of some con temporary eas t African mam- mals. In BEHRENSMEYER A . K & HILL A. (eds.) : Fos-

sils in the making, Butzer and F r e e m a n Editors , Chicago : 131-155.

RIEDL R. 1991 - Fauna e Flora del Mediterraneo. Fran - co Muzio ed., Padova : 777 p.

TORRE D., FICCARELLI G., MASINI F., ROOK L. & SALA B. 1992 - M a m m a l d ispersa l events in the ea r ly Pleistocene of wes te rn Europe. Courier For- schungsinstitut Senckenberg, 153 : 51-58.

VAIn P. R., MrrCHUM R.M. JR., TODD R.G., WIDMIER J.M., THOMSON S. III , SANGREE J. B., BUBB J.N. & HATEILID W.G. 1977 - Seismic S t r a t i g r a p h y and glo- bal changes of sea level. In PAYTON C.E. (ed.) : Seis- mic Stratigraphy - Applications to Hydrocarbon exploitation. Amer ican Associat ion of Pe t ro l eum Geologist, Memoir 36 : 347-363.

WALKER E.P., 1964 - Mammals of the World. The Jones Hopkins Press , Bal t imore , 2 : 647-1500.

WEIGELT J. 1989 - Recent vertebrate Carcasses and their paleobiological implications. [Trans la ted from the ge rman by J. Schafer]. The Unive r s i ty of Chica- go Press, Chicago.

S. D O M I N I C I , L. R O O K , M. B E N V E N U T I & L. ABBAZZI

Dipartimento di Scienze della Terra via G. La Pira, 4

50121 Firenze, I taly