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THEROPOD FOOTPRINTS IN THE CRETACEOUS
ADRIATIC-DINARIC CARBONATE PLATFORM
(ITALY AND CROATIA)
Fabio M. DALLA VECCHIA
A : Theropod footprints are known in ten sites of late Hauterivian/early Barremian
(1), late Barremian (1), late Albian (5) and late Cenomanian (3) age on the Adriatic-Dinaric
carbonate platform (Italy and Croatia). Most of the footprints belongs to small- to medium-
size individuals; large ones are known in the upper Hauterivian-upper Barremian sites and
are much rarer in upper Albian ones. Small- to medium-size theropods are associated with
small sauropods in the late Albian and perhaps in late Cenomanian. Most of the footprint-
bearing beds are marine carbonates exposed to subaereal desiccation in tidal or lagoon set
-
tings. Data suggest that theropods were just passing through these environments. The
Adriatic-Dinaric carbonate platform is a special case of an intraoceanic, or at best very far
away from any continental area, carbonate platform with a local dinosaur fauna.
INTRODUCTION
The Adriatic-Dinaric carbonate platform is a fos-
sil carbonate platform of Jurassic-Cretaceous age.
It was involved in Alpine-Dinaric orogeny and at
present it crops out mainly in NE Italy (Pre-Alps,
Karst), SW Slovenia (Karst, Istria), W Croatia (Istria,
Dinarids), W Bosnia and Montenegro (Dinarids).
Sites with dinosaur fossils are found in Creta
-
ceous limestones exposed along the western coast
of the Istrianpeninsula(Croatia),inIstrian islands, in
the Italian Karst (Trieste) and in a block quarried in
the Cansiglio Plateau (NE Italy) (for references see
D
V 1997 and D V &T
, 1995). Footprints probably made by theropods
are present in most of these sites (Fig. 1).
The detailed study of the Istrian sites from pa
-
leoichnologic, stratigraphic and sedimentologic
point of view is in progress by the part of the writer, I.
Vlahovic, S. Venturini, G. Tunis and A. Tarlao.
Since the Istrian region is bilingual (Croatian and
Italian), I report two names (when existing) for each
locality.
METHODOLOGICAL ASPECTS
Cretaceous tridactyl dinosaur footprints are gen
-
erally attributed to theropod or ornithopod dino
-
saurs. Features characterizing footprints supposed
to have been impressed by theropod dinosaurs (e.g
belonging to bipedal tracks, presence of claw marks,
elongate and narrow digit prints, etc.) are reported in
the main paleoichnological works (H
, 1971;
L
, 1991; T , 1990) and in several
papers dealing with local ichnoassociations (e.g.
L
, 1984; P , 1989).
Following these features most of the tridactyl,
mesaxonic footprints, often organized in bipedal
tracks found in the Cretaceous limestones of
Adriatic-Dinaric carbonate platform are here consid
-
ered to be theropod footprints.
Footprints in a track rarely have the same size: I
report for each trackway just one value of L which
corresponds to the media of the lengths or the length
of the best preserved print. I consider small-size
theropods those with L<15 cm, middle-size those
with 15<L<25 cm and large when L>25 cm.
The extimation of V has been based on the equa
-
tion by A
(1976); h has been calculated by
A
(1976) method and by the allometric
equations of T
(1989). AWS was calcu
-
lated by equation 10.6 in T
(1990). Follow
-
ing T
(1990: 260) the dinosaurs were
considered running when SL/h>2.9.
PALEOGEOGRAPHICAL SETTING
The Adriatic-Dinaric carbonate platform was a
roughly N-S elongated structure bordered W, E and
N by marine basinal areas (i.e. Ionian basin,
Bosnian Basin, Tolmin trough, etc.) (see for exam
-
ple, C
,S &V , 1989; Z
, 1990). As a carbonate platform it is
355
artigos/papers
considered to be mainly a region of marine sedimen
-
tation therefore a shallow marine environment even
if repeated emersions, sometimes long-lasting,
were locally identified (see for example M
et
al., 1996; T
,Š &V , 1994; V ,
T
&S 1989).
It was situated on a microplate (Apulian micro
-
plate or African Promontory; C
, D'A
&H , 1979) placed between African-Arabian
and Laurasian plates. Following D
,R
&V (1993) the Adriatic-Dinaric carbonate
platform was placed at the north-western end of a
larger, narrow and E to W elongated, shallow marine
paleogeographic unit. This unit, made only of car
-
bonate platforms, included from W to E the Gavrovo
zone (Bulgaria), Tripolitza, Menderes, Seydisehir,
Eastern Taurus and Muzurdan (Turkey) and was
surrounded by deep marine troughs. Therefore, fol
-
lowing the paleogeographic maps of D
,R
&V (1993) the Cretaceous Adriatic-
Dinaric carbonate platform was completely
separated from continental areas, dominated by sili
-
coclastic fluvial-lacustrine sedimentation. However,
the affinity with the associations of foraminifers of
Northern Africa, suggests a strict connection with
the African-Arabian continent during Hauterivian-
Barremian (C
&S , 1973). There is
a general agreement that it was separated from the
Arabian-African plate by the opening of the Eastern
Mediterranean Ocean during Early Aptian.
DATA
U
H /L B
Sarone, Cansiglio Plateau, Pordenone provin
-
ce, NE Italy.
A limestone block with a large (L=36 cm) thero
-
pod footprint preserved as positive hiporelief, was
discovered in the pier of Ravenna (Fig. 1(1), 2A, 3A).
Also a sauropod manual print is preserved along
with the theropod footprint (D
V ,in
press). The block comes from a quarry open in the
Cretaceous limestones of the southern flank of the
Cansiglio Plateau, northern point of the Adriatic plat-
form (D
V &V , 1995). The infill-
ing is a wackestone with foraminifers and ostracods
while the stratigraphical section from which the
block comes is composed mainly of mudstones with
ostracods and desiccation structures, and pedoge-
netic breccias, sometimes with black pebbles.
Kolone, Bale/Valle, SW Istria, Croatia.
This locality preserves dinosaur bone remains in
carbonate lacustrine sediments (D
,T &V
, 1998; T ,Š &V , 1994). It
is a rich outcrop which unfortunately lies below the
present sea level. For this reason only a limited
number of specimens, (about 200) mostly fragmen
-
tary, were collected. Most of the identifiable bones
belong to small to large-size titanosauriform, diplo
-
docimorph and, perhaps, camarasaurid sauropods
(D
V , 1994, 1998). Only recently a tooth
and an ungual phalanx belonging to small theropods
were discovered. The tooth is a shed crown 12.5 mm
long, resembling those of the velociraptorine dro
-
meosaurids (see C
,R &S , 1990),
because it is laterally compressed, elongate and re
-
curved, and denticles of the distal carina are decid
-
edly larger than the mesial ones. In fact, in the upper
part of the tooth there are six denticles per mm on
the distal carina and eight denticles per mm on the
mesial carina (”denticle size difference index” of
R
&W (1995) is therefore 1.33). How
-
ever, the preserved denticles do not point apically
like those of the teeth of velociraptorine dromeo
-
saurids. The very small (8.75 mm long) ungual pha
-
356
F.M. DALLA VECCHIA
Fig. 1 - Location of the sites. 1 - Sarone, Cansiglio Pla-
teau, upper Hauterivian/lower Barremian. 2 - Pogleda-
lo/Salsa promontory, Main Brijuni/Brioni island, upper Bar-
remian. 3 - Puntizela/Puntesella, upper Albian. 4 - Ploce
Promontory, Main Brijuni/Brioni island, upper Albian.
5 - Kamnik (Plijesivac) Promontory, Main Brijuni/Brioni is-
land, upper Albian. 6 - Mirna/Quieto river mouth, upper
Albian. 7 - Cervar/Cervera, upper Albian. 8 - Fenoliga islet,
upper Cenomanian. 9 - Grakalovac Promontory, upper Ce
-
nomanian. 10 - Lovrecica/S. Lorenzo di Daila, upper Ceno
-
manian.
´
357
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
Fig. 2 - Theropod footprints. A - Sarone, Cansiglio Plateau (NE Italy), upper Hauterivian-lower Barremian. B -Po
-
gledalo/Salsa Promontory, Main Brijuni/Brioni island (SW Istria), upper Barremian. C - Puntizela/Puntesella (SW Istria),
upper Albian. D - Ploce II, Main Brijuni/Brioni island (SW Istria), upper Albian, cast. All scale bars in centimetres. (Contin
-
ued).
^
358
F.M. DALLA VECCHIA
Fig. 2 (continued) - Theropod footprints. E - Kamnik II, Main Brijuni/Brioni island (SW Istria), upper Albian, cast.
F - Cervar/Cervera I (Central-W Istria), upper Albian, cast. G - Cervar/Cervera II (Central-W Istria), upper Albian.
H - Mirna/Quieto river mouth (central-W Istria) upper Albian. All scale bars in centimetres. (Continued).
^
^
359
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
Fig. 2 (continued) - Theropod footprints. I - Fenoliga Islet (S Istria), upper Cenomanian, cast. J - Grakalovac (SW Is
-
tria), upper Cenomanian, cast. K - Lovrecica/S. Lorenzo di Daila (N Istria), upper Cenomanian. L - Lovrecica/S. Lorenzo di
Daila (N Istria), upper Cenomanian, cast. All scale bars in centimetres.
^
^
lanx is narrow, low, elongate and pointed, not very
much recurved; the ventral margin of the proximal
ungual blade is flat whereas that of the distal ungual
blade is blunt; the groove crosses diagonally the
phalanx ending dorsally well before its point. The
proximal part is not deep, the articular facet does not
exceed the ungual blade in height and the articular
surface occupies most of the articular facet. The
specimen shows some resemblance with the or
-
nithomimid manual phalanges because of its overall
morphology and the presence of a relatively small
flexor tubercle displaced somewhat distally (see
O
&B , 1990; R &W ,
1995) but belongs to a chicken-size individual.
There is a groove between the main body of the pha
-
lanx and the flexor tubercle, which could indicate an
uncomplete fusion of the two and suggests that the
individual was immature, as also indicated by small
size. These specimens, at present under the care of
the municipality of Bale/Valle, are the only theropod
bones recorded up to now from the Istrian region.
U
B
Pogledalo/Salsa Promontory, Main Brijuni/Brio-
ni Island, SW Istria.
In this site there are only large tridactyl footprints
on a single bed surface exposed on the shore as an
elongated band (Fig. 1(2), 2B, 3B). The state of pres-
ervation is not good. Five short tracks, seven cou-
ples and 19 single isolated prints, for a total of about
60 footprints are recognizable. L=24-45 cm; size
distribution is shown in Figure 5. The substrate was
a "fenestral micrite" overlain by stromatolites and
"pellettal limestones" with ripple marks indicating an
intertidal environment (V
&T , 1987; Fig.
4).
U
A
Puntizela/Puntesella, Fazana/Fasana; SW Is
-
tria.
This site presents two footprint-bearing surfaces
placed at different stratigraphic levels (Fig. 1(3)).
Level II is placed few metres above level I.
Level II has a track with five poorly preserved
foorprints (in the best preserved L=17.5 cm). The
printed bed is a pellettal mudstone-wackstone with
rare ostracods; the stratigraphic section presents
high energy bands of grainstone with gastropod
shells.
Level I preserves a segment of a track with four
footprints but only three preserved (in the best one
L=20 cm; Fig. 2C, 3C). The printed bed is a
mudstone-wackestone with rare ostracods and fo
-
raminifers; mud cracks are present on the surface.
Ploce Promontory ("Rocca Kapp" of B
-
E , 1925), Main Brijuni/Brioni Island, SW Is
-
tria.
In this site there are two printed surfaces (I, lower,
and II, upper) at the top of two superimposed layers
(Fig. 1 (4), 2D, 3D). The site was described by the
paleoichnological point of view by B
(1925) who wrongly attributed the footprints to
Iguanodon M
. After the description by the
German paleontologist some footprints were taken
away. For example, none of the large tridactyl foot
-
prints reported by him is now present in the outcrop.
Five slabs with a footprint each are stored in a house
of the port of the island which was once a museum.
They testify the presence of relatively large thero
-
pods (L~40 cm and ~32 cm) but give no other infor
-
mation.
The narrow surface of level I presents two tracks
and a couple, for a total of 12 footprints; L=13.5 cm,
21 cm and 21.5 cm.
In the level II there are 12 tracks, two couples and
five single isolated footprints, for a total of about 60
preserved footprints; L=14-26 cm. Larger footprints
(two tracks?) are considered to came from this hori-
zon.
The footprint-bearing level I is a wackestone with
foraminifers, small gastropods and desiccation
structures. Level II is a packstone-grainstone with
foraminifers and gastropods; the printed surface
shows mud cracks. High energy accumulations of
gastropod shells and ripple marks are present in the
stratigraphic section (Fig. 4).
Kamnik/Pljiesivac Promontory, Main Brijuni/Bri
-
oni Island, SW Istria.
In this outcrop (Fig. 1(5)) there are two track-
bearing surfaces at the top of superimposed beds
but only the upper one presents footprints ascrib
-
able to theropods (Fig. 2E, 3E-F) while the lower one
has just a medium-size ornithopod trackway.
There are four theropod tracks, with badly pre
-
served footprints, for a total of about 70 footprints.
L=15.5-17.5 cm.
The footprint-bearing level is a mudstone-
wackestone with foraminifers and ostracods. The
layer below presents ripple marks (Fig. 4).
Cervera/Cervar, Camping Solaris, Punta del
Dente, NW Istria.
In this site there are two separated footprint-
bearing surfaces which could be different horizons
(D
V , 1994, 1996; D V &
T
, 1995) (Fig. 1(7), 2F-G, 3G-H). One is ex
-
posed along the shore (level I), the other (level II),
360
F.M. DALLA VECCHIA
^
^
´
361
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
I
J
K
L
M
N
5cm
Fig. 3 - Drawings of some theropod footprints from the Cretaceous Adriatic-Dinaric Carbonate Platform. A - Sarone,
Cansiglio Plateau (NE Italy), upper Hauterivian-lower Barremian (see Fig. 2A). B - Pogledalo/Salsa Promontory, Main Bri
-
juni/Brioni island (SW Istria), upper Barremian, taken from the cast (see Fig. 2B). C - Puntizela/Puntesella (SW Istria), up
-
per Albian, (see Fig. 2C). D - Ploce II, Main Brijuni/Brioni island (SW Istria), upper Albian, taken from the cast (see Fig. 2D).
E - Kamnik II, Main Brijuni/Brioni island (SW Istria), upper Albian, taken from the cast (see Fig. 2E). F - Kamnik II, Main Bri
-
juni/Brioni island (SW Istria), upper Albian, taken from the cast. G - Cervar/Cervera I (Central-W Istria), upper Albian,
taken from the cast (see Fig. 2F). H - Cervar/Cervera II (Central-W Istria), upper Albian, taken from the cast (see Fig. 2G).
I - Mirna/Quieto river mouth (central-W Istria) upper Albian, (see Fig. 2H). J - Fenoliga Islet (S Istria), upper Cenomanian,
taken from the cast (see Fig. 2I). K - Grakalovac (SW Istria), upper Cenomanian, taken from the cast (see Fig. 2J).
L - Grakalovac (SW Istria), upper Cenomanian, taken from the cast. M - Lovrecica/S. Lorenzo di Daila (N Istria), upper Ce
-
nomanian, taken from the cast (see Fig. 2K). N - Lovrecica/S. Lorenzo di Daila (N Istria), upper Cenomanian, taken from
the cast (see Fig. 2L). Drawn to scale; scale bar=5cm.
^
^
^
^
^
much wider (33x13 m), is placed few tens of meters
inland, and is the bed of an abandoned largequarry.
In the level I there are 12 tracks, five couples of
footprints and 14 single isolated footprints, for a total
of about 60 footprints. L=16.5-24 cm. Probably there
are also footprints of small-size sauropods. The
footprint-bearing level is a pelletal wackestone with
ostracods, foraminifers and desiccation structures;
in the stratigraphic sequence there are some levels
with large mud-cracks.
In level II there are many tracks and tens of single
isolated footprints. The study of this material is just
beginning. L range seems to be approximately the
same of level I. Many small-sized sauropod foot
-
prints are present too (D
V 1994, 1996).
The printed layer is a mudstone with ostracods and
rare foraminifers; the surface shows mud-cracking.
Mirna/Quieto river mouth, NW Istria.
This outcrop preserved some tracks impressed
by tridactyl, medium-size biped dinosaurs, very
probably theropods (Fig. 1(6), 2H, 3I). Unfortu-
nately, it was nearly completely destroyed by fossil
collectors after 1977 (D
V ,T &T
, 1993).
Two single footprints in private collections (L=21
and 22.5 cm), a possible theropod footprint (L=21
cm) and an uncomplete couple very badly preserved
in situ, are described in D
V ,T &
T
(1993). The footprint-bearing level is a
wackestone-packstone with foraminifers. Subtidal
to supratidal environments are represented in the
thin stratigraphic section (ibidem).
Size distribution of the late Albian theropod foot
-
prints (excluded level II of Cervar/Cervera) is re
-
ported in Figure 6.
U
C
Fenoliga Islet, S Istria.
The footprint-bearing surface (about 28x14 m) is
exposed along the shore and footprints are very
badly preserved (Figs. 1(8), 2I, 3J). There are three
possibly theropod tracks for a total of about 55 foot
-
prints. L=17 cm, 17.5 cm and 21.5 cm. Also many
non-theropod footprints and a non-theropod long
track is preserved in this site. The trackmaker of the
latter was identified by L
&L (1990)
as a small sauropod. Tracks are preserved on a
wackestone with bioclasts (fragments of rudist
shell), foraminifers and desiccation structures.
362
F.M. DALLA VECCHIA
Fig. 4 - Stratigraphical column of the Lower Cretaceous
carbonates of the Main Brijun/Brioni Island with the
footprint-bearing levels. A - Stromatolite. B - Pelmicrite/
pelsparite. C - Biomicrite with Salpingoporella. D - Peritidal
and desiccation breccia. E - Ripple marks. F - Biointras
-
parite with gastropods. G - Oncolite / micrite alternation.
H - Oncolite and micrite with Requienia. I - Emersion brec
-
cias. J - Mud pebbles conglomerate. K - Micrite/fenestral
micrite. L - Oointrasparite. M - Rudist coquina. N - Beds
and lenses of late diagenetic dolomite. O - Desiccation
cracks. The footprint symbol indicates the position and
number of the footprint-bearing levels. After V
&
T
(1987), modified.
U.
^
´
Grakalovac Promontory, Premantura/Promonto
-
re, S Istria.
The printed surface is exposed along the shore in
the upper part of a cliff as a narrow and few metres
long band (Fig. 1(9), 2J, 3K-L). Three tracks and a
single footprint are preserved for a total of 13 foot
-
prints. L=15-25 cm. The printed layer is a biotur
-
bated wackestone-packstone with foraminifers, in a
stratigraphical sequence with rudist limestone beds
and mounds.
Lovrecica/S. Lorenzo di Daila, Umag/Umago,
NW Istria.
In this site there is a single footprint-bearing sur
-
face exposed along the shore as a 20 m long band
(Fig. 1(10), 2K-L, 3M-N). The state of preservation of
the specimens is not good. There are five tracks,
seven probable tracks, three couples and four single
isolated footprints, for a total of 58 footprints.
L=14.5-25.5 cm. The printed bed is a microbreccia
with abundant matrix with foraminifers and clasts
with desiccation structures; it is intercalated among
rudist limestone beds. It is probably a storm layer.
Size distribution of the late Cenomanian thero-
pod footprints is reported in Figure 7.
INTERPRETATIONS
Even if at present the study of the Istrian foot-
prints is far from concluded, some observations can
be anticipated here.
Exposures suited to find vertebrate fossil foot-
prints are limited to just a narrow band exposed
along the coast in Istria, to quarry beds or to quarried
blocks (the case of the footprints from Cansiglio Pla
-
teau). Despite this limited sampling area we found
significant evidence of dinosaurs in the northern part
of the Adriatic-Dinaric platform, which has been less
disturbed tectonically. This is probably just a small
portion of the real dinosaur record of this region. At
least during some intervals of the Cretaceous Peri
-
od, the platform was inhabited by populations of di
-
nosaurs. The emersions which permitted the
presence of the dinosaurs are most probably related
to tectonic events rather than eustatic sea level fluc
-
tuations even if the influence of the latters could
have played a role. In fact the Apulian Promontory or
Microplate during the Cretaceous times was begin
-
ning to collide with "Europe". Besides, late Albian
and late Cenomanian are intervals of worldwide sea
level high stand (D
,R &V ,
1993).
All the sites with footprints are in prevailing ma
-
rine carbonate sequences but with sedimentological
evidence of emersion (pedogenetic breccias, karsti
-
fication of carbonates, bauxites, marsh-lacustrine
deposits, etc.), mainly during late Albian. Footprint-
bearing beds are deposited in marine environments
as tidal flats or lagoons but most of them presents
evidence of subaerial exposure as mud cracks (e.g.
Puntizela/Puntesella I, Ploce II and Cervar/Cervera
II) or desiccation microstructures (e.g. Pogledalo,
Ploce I, Fenoliga).
Only a population of large theropods is testified,
in the single site of late Barremian age. Most of the
footprint lengths are included in the interval 30-38
cm (Fig. 5) corresponding to h values ranging 120-
155 cm to 152-190 cm, with a separate group of
smaller footprints and some larger; M=32.25 cm.
There is not a clear mean, having three small peaks
for 30 cm, 35 cm and 38 cm.
Different is the situation in the upper Albian,
where we have a larger sample. Large theropods
are rather uncommon and middle-size individuals
are prevailing (Fig. 6). In fact, most of the footprint
lengths are included in the interval 16-24 cm corre
-
sponding to h values ranging 64-72 cm to 96-115 cm.
The mean is 21 cm (h = 84-98 cm), M = 20.75 cm and
the distribution is skewed toward smaller forms.
The late Cenomanian assemblage is composed
only by middle-size individuals (Fig. 7); the mean is
21 cm, M = 19.55 cm and the distribution is skewed
toward smaller forms. There are not significative
size differences with the late Albian assemblage, if
we exclude the total absence of large individuals.
Anyway, we must keep in mind that the sample is
much smaller.
At a first preliminary survey there are some differ
-
ent theropod ichnotaxa in the Cretaceous of Istria.
This means that a certain degree of taxonomical di
-
versity is suggested not only by different sizes but
also by footprint morphology (see Fig. 2-3). Its worth
to note that the one here reported is the only thero
-
pod evidence in that part of the Cretaceous world.
No skeletal record of such theropod populations re
-
mains, except the tooth and the phalanx of late
Hauterivian-early Barremian age.
363
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
Fig. 5 - Size distribution of late Barremian footprints.
^
^
´
´
If the carbonate platform was connected with the
African-Arabian continent (at least in pre-Aptian
times), the most probable source area for coloniza
-
tion was Africa via Middle East. No osteological rec
-
ord of theropods is known in the Middle East if we
exclude scanty remains in the ?Cenomanian of
Syria (W
, 1990). Even if some fragmen
-
tary remains have been reported during last 80
years (e.g. D
V , 1995; D &S
, 1925; L , 1960; R &W
, 1995; R , 1996; S , 1915, 1931,
1934), African theropods of Aptian to Cenomanian
age are just beginning to be known in detail (S
et al., 1994, 1996). As the general rule with terres
-
trial vertebrates (B
,W &
D
-B , 1979) the remains of large thero
-
pods are much more represented in the sample than
those of small to medium-size ones. This point out
that the osteological record (biased by strong tapho
-
nomical control) testifies just a little part of the real di
-
nosaur diversity. On the other side, ichnological
record is not suitable for phylogenetical analyses
but opens windows on real distribution and possible
local and general diversity of taxa.
If the platform was intraoceanic, separate from
continental regions by deep seaways since Early Ju-
rassic, as D
,R &V (1993)
suggest, the colonization from a source area is ap-
parently impossible.
None of the theropods was running; the most
common gait was a relatively fast walking (Kamnik,
Ploce II, Puntizela/Puntesella, Cervar/Cervera I,
Fenoliga, Grakalovac, Lovrecica/S.Lorenzo). As a
general feature, they were going straight or in a
slightly undulating way, without big changes of direc
-
tion, stops, or the irregular walking of an animal
searching for food. The estimated V values are as a
rule higher than AWS, in many cases nearly two
times higher (e.g., Cervar/Cervera I and Lovre
-
cica/S.Lorenzo). This suggests that the animals
were just passing through the environments were
they left the prints with something like a cruising
speed. It is interesting to note that the modern flight
-
less bird Emu (Dromaius novaehollandiae
(L
)), which has tridactyl feet and h compara
-
ble to that of most of the Cretaceous theropods of Is
-
tria, covers great distances at a costant speed of
7km.h
(F , 1992). Of course, this observation
is not enough to say that medium-size Cretaceous
theropods had a similar behaviour and, conse-
quently, the same metabolism of the bird Emu.
In outcrops with many footprints and tracks there
is a roughly bimodal distribution of directions. Main
directions are more or less perpendicular (e.g. Kam-
nik II, Ploce II, Lovrecica/S.Lorenzo); sometimes it is
apparently roughly unimodal (Grakalovac). Such
preferential directions have been often interpreted
as evidence of social behaviour. I think that in the
cases under examination another explanation is
possible. The bimodal distribution with more or less
perpendicular directions reflects the typical behav
-
iour of vertebrates reaching the shore: a direction
more or less normal to the local coastline (the short
-
est way to reach it) and a second one parallell to (a
free way with the lateral bondary of the water). The
movement was in both the two verses of each main
direction. The same pattern is present in theropod
trackways in coastal settings of late Albian-early Ce
-
nomanian age of Israel and A
(1966)
came to similar conclusions about the behaviour of
the trackmakers.
Dinosaur body and trace fossils are known in the
carbonate platforms which surrounded the Gulf of
Mexico during Aptian-Cenomanian times, mainly in
the lower-middle Albian but also in the Cenomanian
(P
, 1989). However, the paleogeographic
setting was different from that of the Adriatic-Dinaric
platform. The Gulf of Mexico platforms bordered the
southern part of the North American continent, and
the depositional environment for most of the dino
-
saur fossils has been identified as the shoreline tran
-
sition between continental clastic sediments and the
carbonate tidal flats (P
, 1989).
364
F.M. DALLA VECCHIA
Fig. 6 - Size distribution of late Albian footprints.
Fig. 7 - Size distribution of late Cenomanian foot-
prints.
^
^
^
^
^
^
^
Paleoichnological associations are similar, hav
-
ing in both cases a dominance of supposed thero
-
pods, a significative but lesser presence of
sauropods and rarer ornithopods. This is in agree
-
ment with the concept of Brontopodus ichnofacies
(L
,H &M , 1994).
The predominance of carnivorous dinosaurs is
not so meaningful from the palaeocological point of
view if you accept my hypothesis that the animals
where just passing through: they were not in their
normal habitat. It is clear for some Cenomanian sites
where footprints are preserved in a sequence with
prevailing rudist rudstones and mounds. Tidal flats,
shores and similar environments are rather uncom
-
fortable habitats for large terrestrial vertebrates; I do
not know large and extant terrestrial vertebrates
which use to spend most of their time in such envi
-
ronments. I suspect that dinosaurs lived usually few
hundred of metres or few kilometres inland, where
there was vegetation and fresh water but no or
scarce sedimentation. Tidal flats, shores and similar
muddy and wet environments were just routes and
the only place where large tetrapods could leave evi-
dence of their presence. I do not suggest that the di-
nosaurs were migrating along these routes: this is a
possibility but cannot be demonstrated.
Some faunal differences are evident between
U.S.A. sites and the Istrian ones. The large thero-
pods are dominant in the Gulf sites (P
, 1989)
while medium-size ones are much more common in
Istria. This is particularly true if we compare the
roughly coeval Albian associations. The same hap-
pens with sauropods: upper Albian sauropod foot
-
prints of Istria are comparatively very small,
probably the smallest recorded in the world. I sus
-
pect that such "dwarfism" could be related to insular
-
ism, since the isolated geographical position of the
carbonate platform.
CONCLUSION
Even if the Adriatic-Dinaric carbonate platform
was an area of prevailing marine carbonate sedi
-
mentation, isolated or at best very far from continen
-
tal areas dominated by silicoclastic deposition,
theropods were relatively common. In fact, the ex
-
posed surface where footprints can be found is very
small if compared with the thickness and extension
of the Cretaceous shallow water carbonate se
-
quence of the platform. In spite of this, 10 sites with
theropod and other dinosaur footprints have been
discovered.
During the late Hauterivian/early Barremian
there is evidence of large theropods and medium-
size sauropods in the northern end of the platform,
while in its Istrian portion small to large-size sauro
-
pods lived together with small theropods.
In the only site of late Barremian age just large
theropods are recorded.
Most of the theropod evidence has a late Albian
age, with five sites with at least nine printed levels.
There was the prevalence of medium-size individu
-
als, while large ones are testified just in one outcrop
(Ploce). In one site medium-size theropod footprints
are associated to small sauropod footprints.
Upper Cenomanian sites present only medium-
size theropods. In just one site they are associated
with a possible sauropod track.
The Adriatic-Dinaric carbonate platform is a spe
-
cial case of an intraoceanic carbonate platform, or at
best very far away from continental land, with a local
dinosaur fauna. The paleogeographic and evolu
-
tionary significance of the Istrian dinosaur remains
is just beginning to be investigated.
ACKNOWLEDGEMENTS
I thank A. Tarlao, M. Tentor and G. Tunis for the
help on the field and the sedimentological-
stratigraphical sampling, and the staff of the Gruppo
Speleologico A.D.F. - Museo Paleontologico Cit-
tadino of Monfalcone for the technical, logistical and
economical support. The research of A. Tarlao, who
discovered most of the new sites, has been funda-
mental. Sandro Venturini did the sedimentological
description and interpretation of the thin sections. I
thank J. G. Pittman for the discussion and advice on
paleoichnological ground; J. Moratalla and T.H.
Holtz for the critical review of the manuscript and for
correcting the English grammar.
The field work was possible thanks to the eco
-
nomical support of The Dinosaur Society. This work
was supported also by MURST funds (Dr. G.Tunis).
ABBREVIATIONS
AWS - average walking speed; h - heigth at hip;
L - footprint length; M - media; N - number of speci
-
mens; SL - stride length; V - absolute speed.
REFERENCES
365
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
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366
F.M. DALLA VECCHIA
^
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´
´
´
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367
THEROPOD FOOTPRINTS IN THE CRETACEOUS ADRIATIC-DINARIC CARBONATE PLATFORM
