Marine reptiles from the Triassic of the Tre Venezie Area, Northeastern Italy

36 Pages·2001·2.1 MB·English

by  Rieppel, Olivier

FIELDIANA
Geology
NEW
SERIES, NO. 44
Marine from the Triassic of the
Reptiles
Tre Venezie Area, Northeastern Italy
Olivier Rieppel
Fabio Marco Dalla Vecchia
as
January 31, 2001
Publication 1511
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
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Croat,T. B. 1978. FloraofBarroColorado Island. StanfordUniversityPress, Stanford, Calif., 943 pp.
Grubb, P. J., J. R. Lloyd, and T. D. Pennington. 1963. A comparison ofmontane and lowland rain forest in
Ecuador. I.The foreststructure, physiognomy, andfloristics. JournalofEcology, 51: 567-601. D
Langdon, E. J. M. 1979. Yage among the Siona: Cultural patterns in visions, pp. 63-80. In Browman, L.,
andR.A. Schwarz, eds., Spirits, Shamans, andStars. MoutonPublishers,TheHague,Netherlands.
Murra, J. 1946. The historic tribes of Ecuador, pp. 785-821. In Steward, J. H., ed., Handbook of South
American Indians. Vol. 2, The Andean Civilizations. Bulletin 143, Bureau of American Ethnology,
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Stolze, R. G. 1981. Ferns and fern allies ofGuatemala. Part II. Polypodiaceae. Fieldiana: Botany, n.s., 6: 1-
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FIELDIANA
Geology
NEW
SERIES, NO. 44
Marine from the Triassic of the
Reptiles
Tre Venezie Area, Northeastern Italy
Olivier Rieppel
Department ofGeology
FieldMuseum ofNatural History
1400 South Lake Shore Drive
Chicago, Illinois 60605-2496
U.S.A.
Fabio Marco Dalla Vecchia
Museo Paleontologico
Cittadino di Monfalcone
Via Valentinis 134
1-34074 Monfalcone (Gorizia)
Italy
Accepted March 15, 1999
Published January 31, 2001
Publication 1511
PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY
© 2001 Field Museum ofNatural History
ISSN 0096-2651
PRINTED IN THE UNITED STATES OF AMERICA
GEOLOGY LIBRARY
Table of Contents 9. ICymbospondylus sp.; isolated neural
arch and proximal head of a rib 7
10. IShastasaurus sp.; isolated dorsal ver-
tebral centrum 7
Abstract 1 11. Placodus cf. P. gigas; posterior pala-
Introduction 1 tine tooth plates 8
Systematic Paleontology 2
12. Cyamodontoidea indet.; incomplete
Ichthyosauria 2 neural arch 9
Sauropterygia 8 13. Cyamodontoidea indet., carapace frag-
Discussion 20 ment 11
Acknowledgments 22
14. Cyamodontoidea indet.; nuchal region
Literature Cited 23 of a carapace 12
15. ICyamodus sp.; partial palatine bone .. 13
16. Nothosaurus sp.; rib fragment with iso-
lated tooth 13
List of Illustrations 17. Nothosaurus sp.; incomplete femur 13
18. Nothosaurus sp.; fragmentary mandible 14
19. Nothosaurus sp.; neural arch 14
21.. MLoicxaolsiatiuersusinstp.h,epTarretiaVlensekzeileetoanrea 23 222102... NNNooottthhhooosssaaauuurrruuusss cssfpp...;;N.ppaarrgttiiigaaallntsskkeuuullsll; partial 1156
3. Mixosaurus sp., neural spine 3 skull 17
4. ICymbospondylus sp.; isolated dorsal 23. Nothosaurus cf. N giganteus; lower
vertebral centrum 4 jaw fragments 18
5. ICymbospondylus sp.; isolated dorsal 24. Nothosaurus cf. N. giganteus; vertebrae 19
vertebral centrum 5 25. Nothosaurus cf. N giganteus; distal
6. ICymbospondylus sp.; isolated dorsal end of clavicle 19
vertebral centrum 5 26. Cymbospondylus sp.; dorsal vertebral
7. ICymbospondylus sp.; isolated dorsal centrum 20
vertebral centrum 6 27. Lariosaurus calcagnii; humerus 21
8. ICymbospondylus sp.; partial dorsal 28. Sauropterygia indet.; partial skeleton .. 21
vertebral centrum 6 29. Sauropterygia indet.; thoracic rib 22
m

Marine Reptiles from the Triassic of the Tre Venezie
Area, Northeastern Italy
Olivier Rieppel Fabio Marco Dalla Vecchia
Abstract
Ichthyosaurian and sauropterygian remains are described from Triassic deposits in the Tre
Venezie area of northeastern Italy. The taxa recorded include Mixosaurus, Cymbospondylus,
IShastasaurus, Placodus, ICyamodus, an as yet unnamed cyamodontoid placodont, Nothosau-
rus sp., and Nothosaurus cf. N. giganteus. The temporal distribution of these fossils ranges
from the earliest Anisian to the middle Carnian. Placodus (from the lower upper Anisian
Calcare di Recoaro Formation of Vallarsa and Recoaro) is recorded for the first time (on the
basis of diagnostic material) from the Alpine facies of the Middle Triassic. Collectively, the
sauropterygian fauna from the Tre Venezie area resembles that of the eastern Alpine Triassic
more closely than that of the southwestern Alps. This may indicate two separate colonization
events ofthe Alpine Triassic as intraplatform basins developed along the northwesternTethyan
margin.
Introduction of the European platform before the late Anisian.
It is at the Anisian-Ladinian boundary that the
A number of taxa of marine reptiles (Thalat- fossil record of marine reptiles becomes richer in
tosauria, Ichthyosauria, and Sauropterygia) have the Alpine Triassic. A well-corroborated phylog-
been collected over the years from Triassic de- eny on which paleobiogeographic reconstructions
posits in theTre Venezie area ofnortheastern Italy can be based is available for the Sauropterygia
(Trentino-Alto Adige, Veneto, and Friuli-Venezia only at this time (Rieppel, 1999a). Given the pa-
Giulia). The localities yielding Paleozoic andMe- leobiogeographic reconstruction of the late Ani-
sozoic reptiles in these areas have been cata- sian western Tethyan realm by Marcoux et al.
logued by Sirna et al. (1994), along with an iden- (1993) and the phylogenetic relationships of the
tification of the faunal elements found at the re- Sauropterygia (Rieppel, 1997, 1998a), alternative
spective localities (Fig. 1). Some of the material scenarios can be reconstructed for the invasion of
has been described in greater detail, such as thal- the Alpine Triassic by Sauropterygia. A detailed
attosaurcaudal vertebrae, nothosaur("Paranotho- comparison of the faunas from the Germanic Tri-
saurus") vertebrae, and a tooth-bearing palatine assic (Muschelkalk) and from the southern Alps
fragment of a cyamodontoid placodont (Dalla (Monte San Giorgio and equivalent deposits in
Vecchia, 1993). Other material has remained un- northern Italy; Perledo) led Rieppel and Hagdorn
described and forms thebasis ofthepresentstudy. (1997) to conclude that sauropterygians invaded
The occurrences of Sauropterygia and other the southern Alpine realm through a southern
marine reptiles in the Alpine Triassic range from gateway (Burgundian Gate), which linkedthe An-
&
the early Anisian (Sirna et al., 1994; Rieppel glo-Germanic Basin with the developing southern
Hagdorn, 1997) to the Rhaetian (Pinna, 1990). branch of the Neotethys. In view of their eastern
Lower Anisian records are exceedingly rare, not affinities (with Chinese taxa such as Sanchiaosau-
so much because of a sampling bias, but rather rus, Keichousaurus, and Hanosaurus: Rieppel &
because thecharacteristic intraplatformbasinhab- Lin, 1995; Rieppel, 1998a, 1999b), sauropterygi-
itats did not develop along the southeastern shelf ans might alternatively have reached the eastern
FIELDIANA: GEOLOGY, N.S., NO. 44, JANUARY 31, 2001, PP. 1-25
Fig. 1. Localities in the Tre Venezie area (NE Italy) yielding Triassic marine vertebrates. 1, Ambruseit Creek,
ArtaTerme(UdineProvince); 2,ClapdiVal, Forni di Sotto(UdineProvince);3,PiandelleStreghelocalityofBivera
Mountain, Forni di Sotto (Udine Province); 4, Leno Creek, Specchieri (Trento Province); 5, Recoaro, (Vicenza
Province);6,FuseanearTolmezzo(UdineProvince);7,FusCreek,MoggioUdinese(UdineProvince);8,Mt.Tersadia,
ArtaTerme (Udine Province); 9, Lavaz Creek, Dogna (Udine Province).
Alpine realm along the southeastern continental Giulia Region. Lower Pelsonian (Cuccense sub-
shelf ofEurope, bordering on the western Tethys zone), lowermost upper Anisian.
in the northeast and on the western branch ofthe The specimen (mfsn 19385) was collected by
Neotethys in the south. In view of these alterna- C. Rosenfeld in the bed ofAmbruseit Creek near
tive scenarios, a more detailed analysis ofmarine the village of Piedim (Arta Terme). Specimen
reptiles from the Triassic ofthe southeastern Alps mfsn 19385 comes from alternating black silt-
is likely to provide important new information on stones and gray nodular limestones with subor-
the paleobiogeography of this region. dered black marly limestones. This interval is sit-
uated below and in continuity with the Bivera
Formation (lower Illyrian; Farabegoli et al., 1984)
and is attributed to the Dont Formation (Carulli
Systematic Paleontology et al., 1987). On the basis of ammonoids, the age
can be determined as early Pelsonian, earliest late
Ichthyosauria Blainville, 1835 Anisian (P. Mietto, pers. comm.).
Mixosauridae Baur, 1887 The specimen comprises a total of 15 caudal
Mixosaurus Baur, 1887 vertebral centra, ofwhich 3 are very incompletely
preserved (Fig. 2). All vertebral centra are weath-
Mixosaurus sp. ered to a sagittal or parasagittal plane, exposing
— their deeply amphicoelous and notochordal struc-
Material Museo Friulano di Storia Naturale ture. The length ofthe centra ranges from 12.5 to
(mfsn), Udine, no. 19385; a partially disarticulat- 6 mm, and their height varies from 15 to 14 mm;
ed string of 15 caudal vertebral centra (of which the height/lengthratio varies from 1.12 to 2.3. As-
3 are poorly preserved) associated with neural sociated with the caudal centra are neural arches
arches (Fig. 2). — carrying tall neural spines. The basal portions of
Locality and Horizon Ambruseit Creek, the neural arches are sutured but not fused to the
Arta Terme, Province of Udine, Friuli-Venezia vertebral centra. Thebases (pedicels) oftheneural
FIELDIANA: GEOLOGY
AniFsiiga.n.2.ScaMliexobsaaru=rus20spm.m(.mfsn 19385) from Arta Terme, Ambruseit Creek, Province ofUdine, lowermost upper
arches are generally expanded; one well-pre- and convex posterior margin. Elongation and cur-
served and complete neural arch is remarkable in vatureoftheneural spines arecharacteristic ofthe
that it shows a greatly expanded pedicel, which middle tail section of Mixosaurus (Repossi,
appears to carry distinct pre- and postzygapo- 1902). Only a single elementis preserved thatcan
physes (Fig. 3). Repossi (1902, pi. IX, fig. 9e) be identified as an incomplete chevron.
figured the neural arches oftail vertebrae ofMix- Mixosaurus has a cosmopolitan distribution
&
osaurus cornalianus, which bear pre- and post- during the Middle Triassic (Callaway Massare,
zygapophyses but show much less expanded ped- 1989; Mazin & Sander, 1993; Sander & Mazin,
icels. The neural spines are slender and elongate. 1993), with five species currently recognized.
They slant slightly posterodorsally and show a These are Mixosaurus atavus (Quenstedt, 1852),
slight curvature, resulting in a concave anterior from the lower Muschelkalk of southern Germa-
ny; Mixosaurus cornalianus (Bassani, 1886),
from the Grenzbitumen horizon (Anisian-Ladini-
an boundary) of southern Switzerland and north-
ern Italy; Mixosaurus nordenskioeldii (Hulke,
1873), from the Middle Triassic of Spitzbergen
and British Columbia; Mixosaurus natans (Mer-
riam, 1908), from the Middle Triassic of north-
western Nevada (Sander & Bucher, 1990); and
Mixosaurus maotaiensis Young, 1965, from the
lower Middle Triassic of China (Kweichou Prov-
ince). Early Triassic remains ofMixosaurus have
been reported from British Columbia (Callaway
&
Brinkman. 1989), while intheAnglo-Germanic
Basin, Mixosaurus extends back to the Gogolin
Fig. 3. NeuralarchofMixosaurussp. (mfsn 19385). beds (?Bithynian, lower Anisian) of Gorny Slask
Scale bar =10 mm. (Huene, 1916). Coming from the Pelsonian (low-
RIEPPEL & DALLA VECCHIA: TRIASSIC MARINE REPTILES FROM ITALY
Fig. 4. ICymbospondylus sp. (mfsn 15275); isolated dorsal vertebral centrum from Clap di Val, Forni di Sotto,
Province ofUdine, upper Ladinian. A, Anterior view; B, posterior view; C, right lateral view; D, left lateral view;
E,dorsal view; F, cross-sectional area. Scalebar = 20 mm. Abbreviations: dia, diapophysis (fortheribarticulation);
nc, neural canal.
ermost upper Anisian), the specimen mfsn 19385, Sotto, Province ofUdine. "Formazione delle cal-
from the Carnian Alps, is the earliest record for careniti rosseegrigie," Longobardian, upperLad-
the genus in the Alpine Triassic. The incomplete- inian.
ness of the fossil renders comparison with other The vertebrae were collected at the locality of
species ofMixosaurus difficult, but the broad ex- Clap di Val, near the village of Forni di Sotto
pansion of the pedicel of the neural arch appears (Udine). Specimen mfsn 15275 comes from the
to be a unique character ofthe Friulian specimen. UA5 interval of "red and gray calcarenites For-
mation" (Pisa, 1966), dated to as early as middle
Longobardian (late Ladinian: P. Mietto, pers.
Shastasauridae Merriam, 1902 coram.), from which a rich ammonoid fauna was
Cymbospondylus Leidy, 1868 collected as well. It is a nearly complete centrum,
lacking only a small splinter in the ventrolateral
ICymbospondylus sp. anteriorpart (Fig. 4). In posteriorview itis slimghmt-
— ly deformed by lithostatic pressure. It is 23.6
mm
Material Museo Friulano di Storia Naturale, long, 42.8 high (1.81 height/length ratio), and
mm
Udine, no. 15275; isolated dorsal vertebral cen- the horizontal diameter is 46.0 (anterior sur-
mm
trum. Museo Paleontologico of Portogruaro (Ve- face) and 39.5 (posterior surface), respective-
nezia), uncatalogued specimen; isolated dorsal ly. The anterior and posterior ends ofthe centrum
vertebral centrum. — are deeply amphicoelous and notochordal, but the
Locality and Horizon Clap di Val, Forni di articular surface is only weakly inclined in the
FIELDIANA: GEOLOGY