Exceptional Soft Tissue Fossilization of a Pleistocene Vulture (Gyps Fulvus)

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Exceptional soft tissue fossilization of a Pleistocene vulture (Gypsfulvus): new evidence for emplacement temperatures of pyroclasticflow deposits

Dawid A. Iurino a,*, Luca Bellucci a, Danielle Schreve b, Raffaele Sardella a

aDepartment of Earth Sciences, “Sapienza e University of Rome”, Piazzale Aldo Moro 5, 00185 Rome, ItalybDepartment of Geography, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK

a r t i c l e i n f o

Article history:Received 4 February 2014Received in revised form9 April 2014Accepted 17 April 2014Available online xxx

Keywords:Soft tissue fossilizationTaphonomyPyroclastic sedimentsGyps fulvusPleistocene

* Corresponding author.E-mail address: [email protected] (D.A. Iu

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a b s t r a c t

Volcanic sediments are often unsuitable for the fossilization of both hard and soft organic tissues,however, in some circumstances, they can provide unusual conditions for the preservation of remains.Here we report an exceptional case of soft tissue fossilization of a Late Pleistocene Eurasian griffonvulture (Gyps fulvus) in the pyroclastic sequence of the Alban Hills volcanic region (SE Rome, Italy). CTanalyses have revealed an exceptional natural cast of the complete head and neck that preserveextraordinary detail including the fossilized everted tongue, beak, feather insertions and the first recordof the nictitating membrane of the eye. This fossilization (superior in detail even to the victims of the AD79 Plinian eruption of Vesuvius) reveals no evidence of burning and requires re-evaluation of the thermalconstraints in operation for the preservation of organic materials within pyroclastic sediments. Theanalysis of the external morphological features has provided key information regarding the taphonomicprocesses in operation, the emplacement temperatures of distal pyroclastic flow deposits and the re-lationships between organic materials and low temperature phreatomagmatic flows. This sheds light notonly on the extremely rare situation of fossilization in volcanic contexts but also provides a newperspective on taphonomic studies of highly detailed casts of fossil vertebrates.

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1. Introduction

Fossil animal remains preserved within sediments of volcanicorigin are exceptionally rare in the geological record, constitutingonly w2% of known bone beds of Phanerozoic age (Behrensmeyer,2007). Although volcaniclastic ashesmay preserve ichnofossils and,occasionally, soft-bodied invertebrates such as those from thelower Silurian Wenlock Series, UK (424-430 Ma BP) (Briggs andSiveter, 1996), the extreme heat of a basaltic flow (>900 �C)(Branney and Kokelaar, 2002) will generally destroy any organicmaterials (such as skin, flesh or bone) that it encounters. A notableexception is the Mid-Miocene (15e16 Ma BP) Blue Lake rhinoceros(Diceratherium sp.) from the Grand Coulee area of Washington,USA. There, a mould of the already-dead animal’s carcass, bloatedand floating upside down in a lake, was created when ColumbiaRiver basalt flood deposits entered the shallow water body(Chappell et al., 1951), the instant cooling leading to the formation

rino).

., et al., Exceptional soft tissuow deposits, Quaternary Scien

of pillow lavas that initially packed around the body beforesolidifying.

For vertebrates, the preservation of trackways and footprints involcanic ashes is the most common occurrence, with notable ex-amples from the celebrated late Pliocene hominin footprint surfaceat Laetoli, Tanzania (Leakey and Hay, 1979), hominin footprintsfrom the late Middle Pleistocene site of Roccamonfina, Italy (Miettoet al., 2003) and the trackways of capercaillie (Tetrao urogallus),brown bears (Ursus arctos), a red deer hind with calf (Cervus ela-phus) and horses with foals (Equus sp.) from Middle Laacher SeeTephra (Allerød interstadial, c.11 ka BP) at Mertloch in centralGermany (Baales et al., 2002). The Mertloch case also provides arare insight into seasonality, with deposition in spring inferredfrom the presence of juvenile animals. However, whereas footprintsurfaces can shed light on palaeobiological aspects as diverse asgroup size, posture, gait and behaviour, preservation of the actualvertebrates that made the tracks is highly unusual.

Much palaeoecological information can equally be derived fromsediments and biota buried immediately underneath tephra de-posits, such as the Late Pleistocene Tempest Lake site on the SewardPeninsula in Alaska, dated to 21,570 cal yr BP (Goetcheus and Birks,

e fossilization of a Pleistocene vulture (Gyps fulvus): new evidence force Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.04.024

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D.A. Iurino et al. / Quaternary Science Reviews xxx (2014) 1e82

2001; Kuzmina et al., 2008). Here, a rapidly buried surface hasyielded plant macrofossils in growth position, including mosses, arich assemblage of graminoids and forbs and Salix arctica shrubs,which indicate the presence of mineral soils and calcareous sub-strates (Goetcheus and Birks, 2001). Kuzmina et al. (2008) furtherreported that many of the insects found were buried alive by thevolcanic ash and the species composition and ecological affinities ofthis fossil fauna are typical of Alaskan Late Pleistocene steppeetundra environments. The widespread eruption of the aforemen-tioned Middle Laacher See Tephra also rapidly buried regionalwoodland, leaving entire vertical tree trunks, wood and plant im-pressions preserved in the deposits. These reveal zonation of theAllerød vegetation in the central Rhineland, with low-lying areasand river valleys characterized by mainly aspen and birch withsome willow, higher elevations supporting an upper riparianwoodland with the addition of birdcherry, birch and aspen standsabove 300m asl and finally pine (probably Scots pine) on the upperslopes and plateaux (Baales et al., 2002).

The role of tephra in the preservation of fossils has been furtherhighlighted by Hay (1986) with reference to the Caenozoic volcanicdeposits of East Africa, and in particular those from the Kisingiri-Rangwa volcano on Rusinga Island in the Kavirundo region ofKenya. Here, Miocene age fossils of small vertebrates are found inboth subaerial and subaqueous contexts (Bishop, 1963), with thepresence of natrocarbonatite (alkali carbonatite) ash facilitating

Fig. 1. Location of the Alban Hills v

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rapid formation of a matrix suitable for retaining the moulds ofsoft-bodied forms and providing a source of CaCO3 to enhancepreservation.

In the Kenyan fossiliferous tuffs of Songhor and Koru (emanatingfrom eruptions of the Tinderet volcanic complex), Halstead (1982,43) described an assemblage of “soft-bodied animals preserved assolid objects, including caterpillars preserved in the round; animalswith skeletons are also preserved. Lizards and birds are fossilizedcomplete with their muscles, which are transformed into calciumcarbonate. One lizard can be identified as belonging to a present-day group because its forked tongue is preserved”. Here, themoulds evidently formed extremely rapidly in fine-grained mate-rial sufficiently cohesive to preserve the shapes of the animals untilthey were filled by calcite.

Volcanic deposits likely to embed vertebrate fossils have beensubdivided into two groups with differing temperature ranges(Antoine et al., 2012): (1) distal ash falls, where there is no heatingapparent on the fossils, and (2) relatively cool (by comparison tobasaltic flows) pyroclastic density currents (250e600 �C), whereremains either exist only as casts, or more rarely as ‘baked’ pyro-tized skeletons displaying clear thermal alteration. With respect tothe former, catastrophic death assemblages from distal ash falls canoccur many thousands of kilometres from the original volcanicsource and reflect a delayed and often protracted death throughsuffocation or subsequent pulmonary disease. Examples of distal

olcanic region (SE Rome, Italy).

e fossilization of a Pleistocene vulture (Gyps fulvus): new evidence fornce Reviews (2014), http://dx.doi.org/10.1016/j.quascirev.2014.04.024

Fig. 2. Gyps fulvus V0034. a) V0034.0 block with the head cavity, b) V0034.1 block, c)V0034.2 block, d) V0034.3 block, e) V0034.4 block, f) V0034.5 block, g) V0034.6 block,h) V0034.7 block and i) close-up of the feather. feh) Right wing. The dashed line showsthe change of granulometric size of scoria lapilli. The arrow indicates the top. Scalebars: (aeh) 10 cm and (i) 5 cm.

Table 1Comparison of select measurements of extant Gyps fulvus and of V0034 specimen, (a) de

Extant Gyps fulvus

Variable n Pooled Range Juvenile Immature A

x � SD x � SD (n) x � SD (n) x

Head length 89 142.8 � 5.07 133.3e153.8 142.8 � 5.33 (35) 142.5 � 5.10 (44)

Head width 59 61.1 � 2.54 56.9e66.8 60.6 � 2.83 (16) 61.2 � 2.45 (37) 6

Bill length 91 52.6 � 2.58 45.9e61.1 52.1 � 2.44 (35) 52.6 � 2.74 (46)

Bill-cerelength

74 73.5 � 2.5 67e78.6 73.7 � 2.78 (25) 73.4 � 2.37 (40) 7

Bill width 75 24.8 � 1.84 21.4e29 24.9 � 1.89 (27) 24.8 � 1.82 (39) 2

Bill depth 74 35.5 � 1.94 30.8e40 35 � 1.96 (26) 35.9 � 1.70 (39) 3

D.A. Iurino et al. / Quaternary Science Reviews xxx (2014) 1e8 3

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ashfall assemblages include the abundant large mammals from the11.8 Ma old Ashfall Fossil Beds of Nebraska, USA (Voorhies andThomasson, 1979), which perished as a result of the Bruneau-Jarbridge super-eruption some 1500 km to the west and the>3200 specimens from the 7.1 Ma old Akkasda�gı bone beds ofcentral Turkey (Valli, 2005), their demise likely linked to a gasemanation from eruptions in the Central Anatolian Volcanic Prov-ince (Karadenizli et al., 2005). Concerning the preservation ofvertebrate remains in pyroclastic density currents, an articulatedcranium and mandible of a rhinoceros Ceratotherium neumayri hasbeen recovered from the late Miocene Kavak ignimbrites(9.26 Ma BP) near Karacasar in central Turkey (Antoine et al., 2012).However, the best-known example is the AD 79 Plinian eruption ofVesuvius, Italy, which created casts and occasional skeletons ofhumans, horses and pets, ‘flash heated’ to death in suspended ac-tion poses. The death of these individuals is believed to haveoccurred instantaneously as a result of exposure to temperatures inexcess of 250 �C during a pyroclastic surge (Mastrolorenzo et al.,2010). Critically, however, none of these findings, including thePompeiian archeological remains, preserve complete and highlydetailed external soft tissue anatomy.

Here we present a unique case of vertebrate soft tissue fossil-ization from the Peperino Albano (PA) ignimbrite of Rome, Italy,and discuss both its importance in re-evaluating emplacementtemperatures for volcaniclastic deposits and its role in highlightingthe potential of similar sediments for preserving exceptionalpalaeoecological information. Using Computer Tomography (CT)analyses (Sutton, 2008; Iurino et al., 2013), we have obtained ahighly detailed cast of the entire head of a Late Pleistocene Eurasiangriffon vulture, Gyps fulvus (Hablizi, 1783), thereby providing bothadditional information and amuch higher degree of resolution thanprevious data obtained using traditional methods of casting (seeMeli, 1889, 1892; Manni et al., 2003e2004). Notably, the new CTmould reveals the external morphology of the head in a perfectstatus of preservation with ocular bulbs, eyelids, nictitating mem-brane, the whole cast of the oral cavity and imprints of feathers,making this the best-preserved example of soft tissue preservationin a fossil so far discovered.

2. Geological context and age of the vulture remains

The Alban Hills volcano is a large composite caldera complexlocated about 20 km SE of Rome (Fig. 1). It belongs to the Romanvolcanic potassic province that extends on the Tyrrhenian back-arczone from southern Tuscany to Campania and which has evolvedsince about 700 ka until the present (Funiciello and Parotto, 1978;Fornaseri, 1985). The Alban Hills volcano is now considered

note approximate measurements.

Gyps fulvus fromAlban Hills

dult Male (n ¼ 29) Female (n ¼ 22) /

� SD (n) x � SD (range) x � SD (range)

144 � 4.24 (10) 146.1 � 3.92 (139.5e153.8) 138.9 � 2.50(134.3e143.2)

a 160

2.2 � 2.30 (6) 62.1 � 2.14 (58.4e66.1) 59.8 � 2.51(57.3e66.8)

66

54 � 1.84 (10) 54.1 � 2.18 (49.9e61.1) 51.4 � 1.81(45.9e55)

55.5

3.9 � 0.53 (9) 74.7 � 1.93 (71.5e78.6) 72.6 � 1.77(69.1e76)

77.8

4.4 � 1.95 (9) 24.8 � 1.98 (21.4e29) 25.3 � 1.86(21.8e29)

28.8

5.4 � 2.66 (9) 35.4 � 1.64 (30.8e38.6) 36 � 1.90(32.5e40)

a 35



quiescent (De Rita et al., 1995a) according to its seismic and hy-drothermal activity (Amato and Chiarabba, 1995; Calcara et al.,1995). The chemical composition of the magma involved in theAlban Hills volcanism is basic, mostly ranging from tephrites to K-foidite (Trigila et al., 1995; Giordano et al., 2006). During the mostrecent period of volcanic activity (<260 ka), the interaction be-tween magma and groundwater, present in the highly permeableMesozoiceCaenozoic karstic reservoirs located below the volcano(Funiciello and Parotto, 1978; De Rita et al., 1988), led to extensivephreatomagmatic activity from several maars whose products formwhat is known as the Final Hydromagmatic succession (De Ritaet al., 1995b). Phreatomagmatic eruptions occurred at this timefrom both single and coalescent craters. The elliptic Albano NW-trending maar is the most recent of these craters, from which thePA ignimbrite erupted (De Rita et al., 1986; Giordano et al., 2002).

Fig. 3. Virtual cast of the V0034.0 block cavity. a) Head, b) close-up of the skin surface,c) close-up of the right eye and d) close-up of the pterylae. (ey) Eyelids, (eb) eyeball,(nm) nictitating membrane. Scale bars: (a) 5 cm, (b, d) 1 cm and (c) 2 cm.


The elliptic Albano maar is formed by nested craters aligned NWe

SE, with a 3.5 km maximum diameter. At the present day, LakeAlbano (292 masl) is located along the western slope of the AlbanHills and is the deepest maar crater lake of Europe (�167.5 m)(Anzidei and Esposito, 2009).

The PA ignimbrite is a small volume pyroclastic flow deposit(Porreca et al., 2008), radially distributed around the Lake Albanomaar within 2 km of the edge of the crater rim. The PA ignimbritecovers an area of approximately 40 km2 and its thickness variesfrom a fewmetres to up to 30mwithin palaeovalleys. An estimatedtotal minimum volume of the deposit is approximately 0.2 km3.Field analysis and point counting on thin sections show that thejuvenile component of the deposit, which makes up the 90% of theunit, is consistently fine-grained, with a maximum size of coarseash. Juvenile ash is typically grey in colour. The fine ash matrix ispervasively zeolitised, giving the unit the lithified mechanicalcharacteristics that make it desirable as a construction stone(Trigila et al., 1995).

The occurrence within the PA ignimbrite of both unburnedsteppe grass and arboreal vegetation (Ulmus sp. and Quercus ilex),showing minimal conversion to charcoal, implies that the PAignimbrite had a limited thermal effect on the local vegetation. Thepresence of unburned plants therefore indicates that the temper-ature of the pyroclastic flow must have been lower than the tem-perature of ignition of wood, i.e. at or below around 246 �C(Macdonald, 1972). Radiocarbon dating of fossil branches of Ulmussp. and Quercus ilex embedded within the PA ignimbrite providedan age estimate of 29.7 � 0.4 ka BP (Soligo et al., 2003), within themiddle part of the last glaciation (Marine Oxygen Isotope Stage[MIS] 3). An age determination of 22.9 � 6.7 ka BP was also ob-tained on carbonate deposits underlying the PA ignimbrite byUranium-series dating (using the total sample dissolution tech-nique); this overlaps the radiocarbon date within errors and cor-roborates an age for the PA ignimbrite in MIS 3 (Soligo et al., 2003).

3. Material and methods

3.1. Description of the specimen

In 1889, in the foothills of “Monti Tuscolani” SE of Rome, thefossil remains of a vulture (feather casts and natural counter-moulds or negatives) were accidentally discovered embedded inblocks of the PA ignimbrite (Meli, 1889, 1892; Manni et al., 2003e2004). The blocks represent a lithified pyroclastic deposit, madeup of well-sorted, clast-supported, centimetre-thick layers of mil-limetre sized, dark grey, scoria lapilli, alternatingwith poorly sortedmassive layers of grey coarse ash, containing millimetre-sizedscoria fragments and analcite crystals, along with sparsecentimetre-sized leucitite lava inclusions (Manni et al., 2003e2004). During quarrying activity, the vulture remains becamefragmented into several blocks, eight of which have been preserved(V0034.0-V0034.7) (Fig. 2). Specimens are housed in the Istituto diIstruzione Superiore Secondaria “Leonardo Da Vinci” in Rome.

The V0034.0 block includes the natural counter-moulds of thefrontal portion of the head and the neck. A change in the gran-ulometric size of scoria lapilli can be observed in this block, whichbecomes increasingly coarse towards the top (Fig. 2a). The feathersimprints, including the rachis and vexillum, are well preserved onthe external surface of the blocks V0034.1eV0034.7. Meli (1889)described some of the postcranial bones of the vulture, alsowithin natural moulds, in particular a humerus (length 275 mm), afemur (length 144 mm) and a tibia (length 340 mm). Today, theseremains are unfortunately apparently lost but Meli’s descriptionnevertheless provides useful taphonomic information from theformerly more complete specimen. In addition, Meli (1889 and


Fig. 4. Virtual cast of V0034.0 block cavity. (a) Head in lateral view (right side), (b) head in frontal view and (c) head in lateral view (left side). The red dashed lines indicate the slightdeformation of the head. Scale bar 5 cm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)


references therein) reported several findings of other vertebrateremains (cervids, bovids, equids and wolves) in the PA ignimbrite,found between the late 18th and late 19th centuries. The mostinteresting fossil reportedwas found in 1786 in the village of Ariccia(approximately 10 km from the site where the vulture was found),supposedly a complete natural cast including bones of the skeletonof a deer that was unearthed by workers during an excavation.Unfortunately these fossils were destroyed soon after discovery butthey demonstrate the muchmorewidespread occurrence of similarfossiliferous deposits within the PA ignimbrite.

3.2. Computer tomography

The blocks containing the vulture were first examined in theEarth Science Department of “Sapienza e University of Rome”before tomographic images were made at M. G. Vannini Hospital(Rome) using a Philips Brilliance CT 64-channel scanner. Thescanning of the V0034.0 block produced 833 images each with asize of 512 � 512 pixels. The slices are 0.67 mm thick with aninterslice space of 0.33 mm. Slice data derived from the scans wereanalyzed and manipulated using OsiriX 5.6 32-bit (http://www.osirix-viewer.com), Mimics 10.01 and ZBrush 4 on an iMac.

3.3. Measurements and anatomical abbreviations

The biometric data were taken using standard measurements asdescribed for vultures (Mendelssohn et al., 1989; Mundy et al.,1992; Xirouchakis and Poulakakis, 2008), including head length(HL), from the supraoccipital to the tip of the bill; head width (HW),distance between the widest points in the auricular patches behindthe eyes; bill length (BL), from the tip of the culmen to its junctionto the cere; bill plus cere length (BCL), from the bill tip to the edge ofimplantation of feathers; bill width (BW), from the junction of thetomium of the upper jaw to the cere at both sides of the culmen;and bill depth (BD) and the dorso-ventral distance at the nostrils(Table 1).


4. Results

CT analyses on the V0034.0 block produced a series of imagesthat have been joined to create a 3D virtual model. Using softwarenormally employed in medical imaging, the entire cavity has beenvirtually filled. The results represent a perfect 3D cast of a vulturehead with the distal portion of the neck (Fig. 3a). Along the sagittalplane, the left part of the head is slightly shifted upwards (Fig. 4).The complete absence of any traces of the decomposition processand the clarity of the anatomical details suggest that a pyroclasticflow entered through the mouth soon after death and wrapped theinner walls of the oral cavity, thereby producing a perfect cast ofthe anatomy. This has been observed in detail through the seg-mentation of the virtual model in transversal (Fig. 5), sagittal andcoronal planes. The tongue is well preserved and every anatomicaldetail is apparent (Fig. 5b). It is slightly everted, reaching downtowards the lower part of the beak. The fraenulum, a small fold oftissue that secures or restricts the motion of the tongue, is visibleas well as the glottis (Fig. 5b). The median palatine ridge, theboundary line between non-glandular and glandular mucosa andthe choanae are also clearly visible (Fig. 5d). The choanae do notappear as cavities but as protrusions due to sediment infilling. Thebeak is completely preserved although the nostrils are not evidentbecause they are similarly filled with sediment. The two portionsof the rhamphotheca (the outer surface of the beak consisting ofkeratin), the rhinotheca of the maxilla and the gnathotheca of themandible are clearly distinguishable. The dorsal ridge of themaxilla (culmen) shows a strong thickening in the proximalportion that corresponds to the cere (a waxy structure covering thebase of the beak). This structure is well separated from the distalportion of the culmen through a commissure (Fig. 5a). Both eyesare open and preserve the details of the orbits and the eyelids. Thenictitating membrane can be observed in the right eye (Fig. 3c).Both of the eyelids are swollen compared with those of a livingspecimen. The right ear only is visible on the 3D model and ap-pears as a small circular depression located behind the eye. Both


http://www.osirix-viewer.com/

http://www.osirix-viewer.com/

Fig. 5. Anatomy of the oral cavity. (a) Head in dorsal view, (b) gnathotheca in dorsalview, (c) head in ventral view and (d) rhinotheca in ventral view. (t) Tongue, (g) glottis,(mpr) median palatine ridge, (ngm) non-glandular mucosa, (gm) glandular mucosaand (co) choanae. Scale bar 5 cm.


the high detailed skin of the head and of the neck are also apparenton the 3D model (Fig. 3b). The small folds of skin on the neckcorrespond to the insertion points of the feathers (pterylae)(Fig. 3d), although no traces of feathers are present. To understandthe positioning of the vulture within the ignimbrite, the image ofthe block has been sectioned and made transparent, whereas thehead cavity has been made opaque (Figs. 6 and 7). The result hasallowed reconstruction of the exact position of the raptor at thetime of its death.

5. Discussion

The exceptional level of detail allows all anatomical portions ofboth the head and the beak to be defined. Morphological and


biometrical data from the Alban Hills vulture have been comparedwith those of extant G. fulvus to confirm the taxonomical attribu-tion and to establish the biological characters of this individual.According to the comparative measurements of Xirouchakis andPoulakakis (2008), the Alban Hills vulture was an adult male(>5 yrs) with an estimated weight of more than 7 kg (Table 1). Malegriffon vultures are today smaller than females but significantlylarger (c. 3e5%) for head length, head width, bill length and billlength including the cere (Xirouchakis and Poulakakis, 2008). Thefossil vulture fits perfectly within the range of variation in extantmales of G. fulvus when considering the head and beakmeasurements.

The most convincing hypothesis is that the vulture met itsdeath in a cloud of ash and/or steam and was then engulfed by arelatively cold (<100 �C) pyroclastic flow. The contact with hotashes or steam produced immediate asphyxiation, caused by a lackof oxygen and abundant suspended material that clogged the air-ways. This condition can last for a few seconds before death iscaused by thermal shock (Baxter, 1990; Mastrolorenzo et al., 2010).In animals, scalding can occur when the fluid and/or air temper-atures reach >48.8 �C (Di Maio and Di Maio, 2001); deep burns canoccur in just a few seconds at this temperature. Laryngeal andtracheal burns with associated nasal and bronchial injuries are alsopossible if the steam is inhaled (Di Maio and Di Maio, 2001). Theopen beak of the vulture, with its everted tongue and partially-retracted nictitating membrane, indicates the heat-induced coag-ulation of the muscle tissue and contraction of the muscle fibres(Di Maio and Di Maio, 2001). It is impossible to establish, however,whether the raptor died in flight or while perched (likely on a cliffledge, as is the behaviour of extant griffon vultures). The absence oftrauma to the vulture’s head suggests that soon after scaldingoccurred, the vulture’s body fell into a pyroclastic flow, the lowdensity of which probably absorbed much of the impact, causingthe folding of some secondary feathers but breaking only two ofthese (Fig. 2g). The reconstruction of the raptor’s position confirmsthis interpretation. The blocks with feather imprints have beenattributed to the right wing on the basis of anatomical character-istics. The ventral and dorsal surfaces of the feathers have beenidentified by the depth of the groove left by the rachis, which isvery prominent along the ventral surface of the feathers (Pass,1995). Moreover the shape of the feathers implies that thedifferent blocks were once interconnected (V0034.1 with V0034.2and V0034.3; V0034.5 with V0034.6 and V0034.7), thus allowingthe partial reconstruction of the right wing (Fig. 2feh). The changein the granulometric size of scoria lapilli (Fig. 2a), together with thelateral folding of the head and the everted right wing, indicate thatthe raptor drowned as the flow impacted on the ventral part of thebody. The burial process was synchronous with death and theidentical orientation of the feathers suggests that the vulture’sbody has not undergone transport since its deposition. Porrecaet al. (2008) have previously stated that the equilibriumemplacement temperature of the PA ignimbrite ranges between240 �C and 350 �C; however, such temperatures would havedestroyed the bird’s body and are consequently inconsistent withthe fossil’s preservational state (Sinclair and Lockwood, 2006). Thenatural mould of the ocular bulbs, the nictitating membrane andthe skin therefore require a revised temperature estimate for themarginal areas of the pyroclastic flow, which spanned between50 �C and lower than 100 �C, compatible with the preservation ofanimal soft tissue (Di Maio and Di Maio, 2001; Sinclair andLockwood, 2006). The fine-grained pyroclastic material reducedaerobic activity, favouring the creation of natural counter-moulds(negatives) of the external soft body parts. At the same time, anacidic gas-rich environment inhibited the putrefaction process(Manni et al., 2003e2004).


Fig. 6. Virtual section of V0034.0 block. (a) Section sequence following the antero-posterior direction of the head and (b) section sequence in lateral view of the head. Scale bars 5 cm.


6. Conclusions

The exceptional preservation of a Late Pleistocene vulture’s softtissues within pyroclastic rocks represents a unique case study interms of understanding taphonomic processes. While some simi-larities may be drawn with the mode of death for the Pompeiianvictims, the Alban Hills example preserves an altogether incom-parable level of millimetre-scale fine detail.

The temperature range calculated for the PompeiieHercula-neumeOplontis volcanic sediments, emanating from the eruptionof Vesuvius (79 AD), is between 250� and 600 �C. Antoine et al.(2012) proposed a similar range for the late Miocene Kavak ig-nimbrites in central Turkey, suggesting that the rhinoceros peri-shed in a pyroclastic density current with a temperature of 400e450 �C. However, the inferred equilibrium emplacement tempera-ture of the PA ignimbrite of Porreca et al. (2008) (240e350 �C) canno longer be corroborated by the present analysis of the Alban Hills

Fig. 7. Transparent view of V0034.0 block. It shows the laterally torsion of the head.Scale bar 5 cm.


vulture, which allows the thermal range for the PA ignimbrite to bepinpointed to between 50 �C and 100 �C, considerably lower thanearlier calculations. This would strongly suggest that the thermalranges of some other fossil-bearing pyroclastic deposits should bereviewed. Such deposits should be routinely investigated in future,with special attention paid to the detection of natural cavities thatmight preserve moulded soft tissues, and using a multidisciplinaryapproach involving technologies such as ground-penetrating radarand CT scanning. Although the other specimens from the PAignimbrite are now lost, analysis of historical sources in the sci-entific literature such as Meli (1889) suggests that these particulartaphonomic conditions are not a one-off, indicating that low-temperature phreatomagmatic deposits such as these can be anexcellent source of exceptionally well-preserved fossils.

In summary, the evidence from the Alban Hills vulture not onlyprovides a detailed insight into the external morphological featuresof a Pleistocene organism, through the preservation of soft tissuemoulds, but further highlights the exceptional potential of low-temperature phreatomagmatic deposits for the preservation ofpalaeoecological information in contexts where these data maynormally be lacking. This also opens the door for new perspectivesto be gained regarding the genesis of diverse pyroclastic deposits,since the very preservation of soft tissue and fine-scale morpho-logical features provides a restricted thermal constraint on this typeof deposit. Exciting possibilities therefore exist, through moresystematic multi-technique investigation of volcaniclastic depositsof various ages, for the recovery of palaeoecological and palae-obiological information, which may be particularly informative inthe understanding of morphology and behaviour of extinct species.

Acknowledgements

We would like to thank Dr. Massimiliano Danti and Prof. SabinoWalter Della Sala (Ospedale M.G. Vannini, Roma) for undertakingthe CT scanning. Prof. Gianna Renzini and Prof. Antonella Reverberi



(I.I.S.S. Leonardo Da Vinci, Roma) provided access to the fossil. Wealso thank Dr. Luca Santini, Dr. Leonardo Ancillotto and Dr. Fabio DiVincenzo (Sapienza Università di Roma) and Dr. Carlo Rosa (Fon-dazione Ing. C. M. Lerici e Politecnico di Milano) for their usefulsuggestions and help. A special thank to the Editor in Chief C.V.Murray Wallace and referees.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.quascirev.2014.04.024.

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Exceptional Soft Tissue Fossilization of a Pleistocene Vulture (Gyps Fulvus)

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