Zoological Journal of the Linnean Society, 2011, 163, S257–S272. With 5 figures
Redescription and phylogenetic relationships of
Meridiosaurus vallisparadisi, a pholidosaurid from the
Late Jurassic of Uruguay
DANIEL FORTIER1,2*, DANIEL PEREA3 and CESAR SCHULTZ1
1
Departamento de Paleontologia e Estratigrafia, IG, UFRGS, Avenue Bento Gonçalves, 9500,
Cx. P. 15001, Porto Alegre, RS, Brazil
2
Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, USA
3
Departamento de Evolución de Cuencas, Facultad de Ciencias, Iguá 4225, 11400 Montevideo,
Uruguay
Received 12 April 2010; accepted for publication 28 October 2010
Meridiosaurus vallisparadisi Mones, 1980, a freshwater pholidosaurid from the Late Jurassic of Uruguay, is
redescribed herein. It can be diagnosed by the possession of the following combination of features: (1) lateral
constriction of the rostrum at premaxilla–maxilla contact, strong lateral expansion of the premaxilla with the fifth
tooth placed in the widest portion; (2) sinusoidal premaxilla–maxilla suture in palatal view, posteromedially
directed on its lateral half, and anteromedially directed along its medial region; (3) evaginated maxillary alveolar
edges forming a discrete collar at each alveolus, lateroventrally oriented; (4) greater number of maxillary teeth (at
least 27) with respect to Elosuchus (less than 20 maxillary teeth); (5) nasals do not meet premaxilla dorsally; (6)
strong sinusoidal lateral contour of snout in dorsal view, with respect to the similar condition of Elosuchus, forming
two waves (‘festooned’); and (7) third, fourth, and fifth alveoli are equally enlarged. A phylogenetic analysis was
performed, including six pholidosaurids: Elosuchus, Meridiosaurus, Oceanosuchus, Pholidosaurus, Sarcosuchus,
and Terminonaris. The analysis confirmed the monophyly of Pholidosauridae, and a new definition is proposed: a
stem-based group name including Pholidosaurus schaumburgensis Meyer, 1841 and all taxa closer to it than to
Dyrosaurus phosphaticus (Thomas, 1893) or Pelagosaurus typus Bronn, 1841. Pholidosauridae originated in Europe
during the Middle Jurassic, dispersed to Africa, and North and South America, in several dispersal events, and
completely disappeared in the Late Cretaceous.
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272.
doi: 10.1111/j.1096-3642.2011.00722.x
ADDITIONAL KEYWORDS: aquatic crocodylomorph – mesoeucrocodylia – neosuchia – pholidosauridae –
Tacuarembó.
INTRODUCTION
Pholidosauridae is a group of fossil longirostrine crocodylomophs adapted to aquatic environments,
reported from the Middle Jurassic (Owen, 1884;
Mook, 1942) to Late Cretaceous (Mook, 1934; Wu,
Russell & Cumbaa, 2001; Hua et al., 2007). Remains
*Corresponding author. E-mail: daniel.fortier@ufrgs.br
of Pholidosauridae occur in marine, estuarine, and
fluviolacustrine sediments of North America
(Shimada & Parris, 2007), South America (Buffetaut
& Taquet, 1977), Africa (Sereno et al., 2001), and
Europe (Salisbury, 2002). Despite some well-known
species, like Terminonaris and Sarcosuchus, some
pholidosaurids are still rather poorly known, like
Pholidosaurus and Anglosuchus.
There are three main Mesozoic longirostrine crocodylomorph groups: Thalattosuchia, Dyrosauridae,
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
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D. FORTIER ET AL.
Figure 1. Map showing the Tacuarembó Formation (shaded area) and Valle Edén locality.
and Pholidosauridae. The latter have been included
in some phylogenetic analysis, but there is still no
consensus as regards to the monophyly of the group.
Some authors consider Pholidosauridae as a monophyletic group (Jouve et al., 2006; Jouve, 2009),
whereas others postulate its paraphyly (Sereno
et al., 2001; Wu et al., 2001; Young & Andrade, 2009).
Nevertheless, all those works show the close relationship between Pholidosauridae and Dyrosauridae.
However, the relationship among them and Thalattosuchia is controversial. Previous cladistic hypotheses have considered at least two main positions for
Thalattosuchia: as the sister clade of most mesoeucrocodylians (Buckley et al., 2000; Sereno et al., 2001,
2003; Tykoski et al., 2002; Larsson & Sues, 2007;
Sereno & Larsson, 2009; Young & Andrade, 2009); or
as closely related to Pholidosauridae and Dyrosauridae (Clark, 1994; Buckley & Brochu, 1999; Larsson
& Gado, 2000; Wu et al., 1997, 2001; Brochu et al.,
2002; Pol & Apesteguía, 2005; Jouve et al., 2006;
Jouve, 2009; Pol & Gasparini, 2009). Although recent
works have explored improvements, either in cladistic
methods or in taxon sampling, the phylogenetic
relationships among those groups are still under
debate and are far from a conclusion.
A partial skull of a longirostrine crocodylomorph
was discovered in the 1970s, from the Late Jurassic–
Early Cretaceous continental sediments of Uruguay
(Fig. 1). Mones (1980), in a brief note, described the
specimen and tentatively assigned it as a member of
Pholidosaudidae. Named Meridiosaurus vallisparadisi Mones, 1980, it was the first amniote found in the
Tacuarembó Formation, and the only one for at least
20 years (Mones, 1980; Perea, Ubilla & Rojas, 2003).
After a reanalysis of the type specimen, it was found
necessary to redescribe the incomplete skull, along
with a few elements not mentioned in the original
description, such as a mandibular fragment. Meridiosaurus vallisparadisi is redescribed herein and its
phylogenetic relationship is tested through a cladistic
analysis, including most of the pholidosaurid species.
GEOLOGICAL SETTINGS
The sediments of the Tacuarembó Formation
outcrop in northern Uruguay (Fig. 1), mainly in the
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
departments of Tacuarembó and Rivera (Martínez
et al., 1993). The sediments were formed in fluviolacustrine and aeolian depositional systems (Perea
et al., 2009). Sprechmann, Bossi & Da Silva (1981)
distinguished two members within the formation:
Batoví (lower) and Rivera (upper) members (Perea
et al., 2009). The latter unit is afossiliferous.
The fossil remains are preserved in the sandstones
of the Batoví Member, widespread around the city
of Tacuarembó. The formation yields fossils from
freshwater and terrestrial environments, including
bivalves, gastropods, ostracods, conchostracans, dipnoans, ‘semionotiform’-like halecostomes, freshwater
hybodontid sharks, testudines, crocodylomorphs,
theropod dinosaurs, and ichnofossils (Mones, 1980;
Martínez et al., 1993; Yanbin, Gallego & Martinez,
2004; Soto & Perea, 2008; Perea et al., 2001, 2003,
2009).
Until recently, the age of the Tacuarembó Formation has been estimated on the basis of purely stratigraphic criteria, and there was no agreement in the
published literature. It was considered as Late Triassic (Bossi & Navarro, 1991; Bossi, 1996), Late
Triassic–Late Jurassic (Herbst & Ferrando, 1985),
Early Jurassic–Early Cretaceous (Sprechmann et al.,
1981), and Late Jurassic–Early Cretaceous (Mones &
Figueiras, 1981). Since the discovery of Priohybodus
cf. Priohybodus arambourgi d’Erasmo, 1960 (Perea
et al., 2001), the age of the Tacuarembó Formation
has been considered as Late Jurassic–Early Cretaceous. Later works also confirmed that age (Perea
et al., 2001, 2003; Soto & Perea, 2008), and the recent
work of Perea et al. (2009) performed a complete
lithographic and biostratigraphic study, and confirmed that the Tacuarembó Formation cannot be
older than Kimmeridgian or younger than Hauterivian. The fossil assemblage of the Batoví Member
suggests a Kimmeridgian–Tithonian age (Soto &
Perea, 2008; Perea et al., 2009). Meridiosaurus vallisparadisi was discovered in sediments of the Batoví
Member, in the Valle Edén locality, near Tacuarembó
city.
SYSTEMATIC PALEONTOLOGY
MESOEUCRODODYLIA WHETSTONE &
WHYBROW 1983
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Composition: Elosuchus cherifiensis (Lavocat, 1955),
Elosuchus felixi Lapparent de Broin, 2002, Meridiosaurus vallisparadisi Mones, 1980, Oceanosuchus
boecensis Hua et al., 2007, Pholidosaurus purbeckensis (Mansel-Pleydell, 1888) Pholidosaurus schaumburgensis (Meyer, 1841), Sarcosuchus hartii (Marsh,
1869), Sarcosuchus imperator de Broin & Taquet,
1966, Terminonaris browni (Osborn, 1904), Terminonaris robusta (Mook, 1934). Putative pholidosaurids
are Anglosuchus geoffroyi (Owen, 1884) and A.
laticeps (Owen, 1884), Crocodilaemus robustus
Jourdan in Gervais (1871), and Pholidosaurus meyeri
(Dunker,
1843).
Sarcosuchus
hartii,
from
the Early Cretaceous of Brazil, could be the same
species of S. imperator, as stated in de Broin &
Taquet (1966). The group ranges temporally from the
Middle Jurassic (Bathonian) to Late Cretaceous (Late
Turonian).
Emended
diagnosis:
Longirostrine
mesoeucrocodylians distinguished by the possession of the
following unambiguous synapomorphies: (1) anterodorsal margin of the external naris without the premaxillary dorsal projection; (2) the medial margin of
the orbit is formed mostly by the prefrontal, with
little or no participation of the frontal; (3) the fifth
premaxillary tooth is anterolaterally placed in relation to the maxillary tooth row; (4) the posterior
premaxillary teeth are longer then the anterior
teeth; (5) the ventral edge of the premaxilla is
located deeper than the ventral edge of the maxilla;
(6) the distance between the tip of the snout and
the anteriormost position of the premaxilla–maxilla
suture in dorsal view is smaller than the distance
between this and the posterodorsal extremity of the
premaxilla (except in Elosuchus); (7) absence of
postorbital–ectopterygoid contact; and (8) the
maximal width of premaxillae is wider than the
maximal width of the rostrum at the level of the
fourth or fifth alveoli.
MERIDIOSAURUS VALLISPARIDISI
1980 (FIG. 2)
MONES,
PHOLIDOSAURIDAE ZITTEL & EASTMAN 1902
Etymology: Genus from meridionalis, Latin for ‘southern’, and saurus, Greek for ‘lizard’, referring to the
southernmost record of a pholidosaurid. Specific
epithet from vallis, Latin for ‘valley’, and paradisus,
latin for ‘paradise, Eden’, referring to its geographic
provenance, the Valle Edén locality.
New definition: a stem-based group name including
Pholidosaurus schaumburgensis (Meyer, 1841) and
all taxa closer to it than to Dyrosaurus phosphaticus
(Thomas, 1893) or Pelagosaurus typus Bronn, 1841.
Holotype: FC-DPV-2322 (formerly SPV-FHC-27-II-781), anterior part of rostrum, mandible fragments, one
osteoderm, and unidentifiable fragments. No referred
NEOSUCHIA BENTON & CLARK 1988
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D. FORTIER ET AL.
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
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Figure 2. Meridiosaurus vallisparadisi, holotype and unique specimen, FC-DPV-2322. A and C, rostrum in dorsal view;
B and D, rostrum in dorsal view; E, rostrum in right lateral view; F, zoom of the dashed area in D, showing the details
of two maxillary teeth; G–I, right lower jaw fragment in lateral, medial, and dorsal views, respectively; J, caudal
osteoderm in dorsal view. Abbreviations: d, dentary; dn, notch for dentary teeth; if, incisive foramen; mx, maxilla; mg,
Meckelian groove; pmx, premaxilla; sp, splenial. Scale bars: A–E, 5 cm; F–J, 1 cm.
䉳
specimens. Housed in the Colección de Vertebrados
Fósiles, Faculdad de Ciencias, Montevideo (FC-DPV).
Horizon and locality: The fluviolacustrine sandstone facies of the Batoví Member, Tacuarembó Formation, in the Valle Edén locatily near Tacuarembó
city.
Emended diagnosis: Longirostrine mesoeucrocodylian
with the following combination of features: (1) lateral
constriction of the rostrum at premaxilla–maxilla
contact, strong lateral expansion of the premaxilla
with the fifth tooth placed in the widest portion; (2)
sinusoidal premaxilla–maxilla suture in palatal view,
posteromedially directed on its lateral half and
anteromedially directed along its medial region; (3)
evaginated maxillary alveolar edges forming a discrete collar at each alveolus, lateroventrally oriented;
(4) greater number of maxillary teeth (at least 27)
with respect to Elosuchus (less than 20 maxillary
teeth); (5) nasals do not meet premaxilla dorsally; (6)
strong sinusoidal lateral contour of snout in dorsal
view, with respect to the similar condition of Elosuchus, forming two waves (‘festooned’); and (7) third,
fourth, and fifth alveoli are equally enlarged.
DESCRIPTION
State of preservation: The specimen is very fragmented. Practically all teeth are missing, and even
small elements, like an osteoderm, are fragmented.
Nevertheless, there is no evidence of water abrasion.
The sutures are visible and external ornamentation is
preserved, as well the delicate details of a carinated
maxillary tooth. There is no evidence of diagenetic
distortion.
Gerenal features: The nearly tubular rostrum measures 27.8 cm in length, 2.6–7.6 cm in width, and
1.5 cm in height. The external surface is ornamented
with deep pits and grooves, but the evaginated alveolar margins are smooth. The lateral and ventral edges
of the rostrum are sinusoidal in dorsal and ventral
views, forming waves, constricted anteriorly at the
level of premaxilla–maxilla suture in ventral view,
and posteriorly at the level of the seventh maxillary
teeth. The heart-shaped external naris is longer than
wide, not divided, and completely surrounded by the
premaxillae. It faces dorsally and is separated from
the anterior edge of the rostrum by the premaxillary
bar. There is no premaxilla–nasal contact, an autapomorphic feature of Meridiosaurus.
Premaxilla: Both premaxillae were preserved and
show fractures of compression oriented dorsoventrally. Each has a maximum length of 7.5 cm.
The width for each is 2.6 cm at the level of the
premaxilla–maxilla constriction, and the maximum
width is 4.2 cm at the level of the fourth tooth. Each
premaxilla has five teeth. The alveoli are ventrally
long and ventrally oriented. The first two are aligned
transversely at the anterior margin of the bone. The
other three teeth are positioned in a posteriorly
curving arch. Alveoli for the first four teeth enlarge to
the fourth tooth. The fifth is the smaller, placed
anterolaterally to the maxillary tooth row, and is in
close contact with the fourth tooth. In ventral view,
there is a deep notch for the first dentary teeth, at the
level of the third tooth, and a shallow notch for the
second dentary teeth behind it. Dorsally, the acute
posterior process extends to the level of the fifth
maxillary tooth, and in ventral view to the level of the
first maxillary tooth. The distance between the tip of
the rostrum and the anteriormost position of the
premaxilla–maxilla suture in dorsal view is smaller
than the distance between this and the posterodorsal
extremity of the premaxilla. The premaxilla–maxilla
suture is smooth in dorsal view, and slightly serrated
in lateral view. Laterally, the suture is oriented
anteroventrally, and ventrally is sinusoidal, with the
medial part directed anteriorly and the lateral part
directed posteriorly. The premaxilla is constricted at
the contact with the maxilla, and expands anteriorly
forming a concave notch, similar to the condition in
Goniopholis simus (Salisbury et al., 1999). It is more
expanded than the maxillae until the thirteenth maxillary teeth, where the maxillae become wider. The
anterior part is expanded dorsoventrally, and the
ventral edge is placed slightly deeper than the
maxilla edge, not as far as in Sarcosuchus imperator
(Sereno et al., 2001) or Terminonaris robusta (Wu
et al., 2001). A small ovate incisive foramen is placed
in the middle of the premaxillae in ventral view, and
is also visible in dorsal view. Some small to large
foramina are located in the ventral view, parallel with
the tooth row.
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Maxilla: Both maxillae are present, but fragmented.
The right maxilla has 27 alveoli preserved. Each
alveolus is surrounded by the unsculptured evaginated maxillary edge. The anterior alveoli are subcircular, and the posterior alveoli are anteroposteriorly
oval. Among the first eight alveoli, the third, fourth,
and fifth are larger. One complete and nine incomplete teeth are preserved. The teeth have a smooth
root (based on the left thirteenth tooth) and a carinated crown (based on the left fourteenth and right
third teeth; Fig. 2F). The tooth rows form sinusoidal
waves, and at the level of the fifteenth tooth, the
maxillae expand posteriorly. In ventral view, there is
an acute anterior process, extended to the level of
the fourth premaxillary tooth, close to the incisive
foramen. The anterior teeth have a large interalveolar space, whereas the posterior alveoli are close
to each other. Notches for dentary teeth follow the
tooth rows medially, from the eighth tooth to the end
of the maxillae. The maxillae are well sutured in the
midline. Some small foramina are located in ventral
view, medially to the notches for dentary teeth.
Dentition: Alveolar proximodistal diameters vary
between 2.6 mm (fifth premaxillary tooth) and
6.3 mm (fourth premaxillary tooth). The maximum
interalveolar space is 5.1 mm, between the first and
the second maxillary teeth. The teeth have a smooth
root and carinated crown, forming ridges (Fig. 2F).
The last maxillary alveoli are lingolabially compressed, oriented parallel with the longitudinal axis
of the rostrum. However, all the preserved teeth are
circular to subcircular in cross section. No teeth show
constriction at the base of the crown, and the width of
the root is nearly equal to the width of the crown. No
premaxillary alveoli are inturned, as in Sarcosuchus
and Terminonaris (Sereno et al., 2001). All dentary
teeth occlude lingual to maxillary teeth, as suggested
by the presence of notches in the premaxillae and the
maxillae for occlusion of the dentary teeth. The tooth
margins are slightly higher than the medial portion of
the palate.
Mandible: Only a post-symphysial dentary fragment
was preserved, probably from the right ramus,
bearing three incomplete teeth (Fig. 2G–I). The ornamentation is formed by shallow grooves. The alveolar
edges are evaginated, forming discrete evaginations
at each alveoli, covering the base of the teeth. All
alveoli lie in a 30° angle, postero-anteriorly. As in the
maxilla, the dentary teeth have a smooth root and a
carinated crown. In lingual view, a thin sheet of the
splenial was preserved, forming the ventral edge of a
reduced Meckelian groove.
Bone armour: Only one osteoderm was recovered
associated with Meridiosaurus remains, from the
caudal armour (Fig. 2J). The osteoderm is strongly
ornamented, with ridges, grooves, and punctuations,
and is not keeled. It is slightly convex dorsally, and it
bears an anteriorly depressed overlap margin for
articulation with the preceding osteoderm. It is very
similar to the caudal osteoderm of Sarcosuchus
(Sereno et al., 2001).
Remarks on size and weight: Usually, the ratio
between the preorbital length and the total skull
length is used in longirostrine crocodylomorphs
(e.g. Hua et al., 2007). However, this measure cannot
be made for Meridiosaurus. Elosuchus have a ratio
between the length of the tip of the snout to the last
maxillary tooth, and the total skull length equal to
68%. There is little variation in this percentage
among other pholidosaurids, e.g. 65% for Sarcosuchus
and 70% for Terminonaris. Considering the last preserved maxillary tooth of Meridiosaurus as its last
tooth, we can suppose a skull length of 40 cm. This
value is the minimum size of the skull, but it is
possible that more teeth were present posterior to the
last preserved tooth. Plotting this size in the regression formulae of Sereno et al. (2001), the body length
should vary between 2.3 and 2.8 m, which would
make it the smallest know pholidosaurid. Using the
regression formulae of Farlow et al. (2005), Meridiosaurus weighed between 45 (2.3 m body length) and
85 kg (2.8 m body length). Nothing can be inferred
about the age of the specimen.
DISCUSSION
Pholidosauridae is well supported by eight unambiguous synapomorphies. However, some are homoplastic
and are shared with other neosuchian crocodylomorphs, or can vary inside the group. The distance
between the tip of the snout and the anteriormost
position of the premaxilla–maxilla suture in dorsal
view is longer than the distance between this and the
posterodorsal extremity of the premaxilla in Elosuchus, differing from all other pholidosaurids that have
this feature preserved. This autapomorphy may be
associated with the anterior elongation of the nasal
that borders the external naris in this taxon. In
pholidosaurids, the maximal width of the premaxillae
is more expanded than the maximal width of the
rostrum at the level of the fourth or fifth alveoli, as
well as in Gavialis gangeticus (Gmelin, 1789) and
some teleosaurids (Jouve, 2009). The medial margin
of the orbit in dorsal view is formed mostly by
the prefrontal, and the frontal is excluded or participates only slightly, as in Goniopholis simus Owen,
1878, Metriorhyncus superciliosus (Blainville, 1853),
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MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
Dakosaurus andiniensis Vignaud & Gasparini, 1996,
‘Teleidosaurus’ gaudry Collot, 1905, and Chenanisuchus (Salisbury et al., 1999; Jouve, Bouya & Amaghzaz, 2005; Jouve, 2009; Pol & Gasparini, 2009).
All known pholidosaurids possess all the diagnostic
features, expect when not preserved. Nevertheless,
there are features that are not included in the diagnosis because of ambiguity (either ACCTRAN or
DELTRAN optimizations) or primitivity (simplesiomorphies), but in fact they are useful for the identification and differentiation between Pholidosauridae
and other longirostrine groups, particularly Thalattosuchia and Dyrosauridae. The supratemporal fenestrae are relatively short, but are still longer than the
orbits, the basioccipital lacks well-developed bilateral
tuberosities, and the quadrates are ornamented in the
base. Pholidosaurids and Teleosaurus share five premaxillary teeth (Jouve, 2009). Pholidosaurids have a
broad sculpted region separating the supratemporal
fenestrae, as well as Teleosaurus cadomensis (Lamouroux, 1820) (Jouve, 2009) and Chenanisuchus
(Jouve et al., 2005). Dyrosaurids and pholidosaurids
share a squamosal longer than the postorbital. In
Terminonaris, the squamosal is about as long as the
postorbital (Wu et al., 2001).
When compared with other longirostrine groups –
Thalattosuchia and Dyrosauridae – several characters exclude Meridiosauris vallisparadisi from them.
It differs from Thalattosuchia in characters that
include the heavy external ornamentation, the presence of a strong lateral expansion of the premaxilla,
the presence of five premaxillary teeth, the sinusoidal
premaxilla–maxilla suture in ventral view, the sinusoidal contour of the snout in dorsal and lateral
views, and the evaginated maxillary alveolar edges.
Meridiosaurus differs from dyrosauridae in the presence of five premaxillary teeth rather than four
(Barbosa, Alexander & Viana, 2008), the expanded
premaxilla, the anterolateral position of the last premaxillary tooth, the absence of the nasal–premaxilla
contact, and the sinusoidal contour of snout in dorsal
and lateral views. Meridiosaurus vallisparadisi is
diagnosed as a Pholidosauridae with the presence
of: (1) a deep ventral edge of premaxilla in respect to
the ventral edge of maxilla in lateral view; (2) an
expanded premaxilla; (3) the anterolateral position of
the fifth premaxillary tooth; (4) the maximal width of
premaxillae is wider than the maximal width of the
rostrum at the level of the fourth or fifth alveoli; and
(5) the distance between the tip of the snout and
the anteriormost position of the premaxilla–maxilla
suture in dorsal view is smaller than the distance of
that and the posterodorsal extremity of the premaxilla. Meridiosaurus vallisparadisi differs from any
other pholidosaurid in the absence of a premaxilla–
nasal contact in dorsal view, an autapomorphic
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feature for this taxon. Interestingly, Kälin (1955)
illustrated a Pholidosaurus schaumburgensis skull
with no premaxilla–nasal contact. Andrews (1913)
commented that the Pholidosaurus purbeckensis
nasal anterior process ‘probably’ just reaches the posterior process of the premaxilla. However, Köken
(1887) illustrated a skull of Pholidosaurus schaumburgensis with clear premaxilla–nasal contact. This
feature seems to vary among Pholidosaurus species
and specimens. Even if this condition is confirmed for
Pholidosaurus, Meridiosaurus would still be differentiated from Pholidosaurus in the presence of the
sinusoidal contour of the snout in dorsal and
lateral views, the large notch on ventral edge of the
snout at premaxillae–maxilla contact, the sinusoidal
premaxillae–maxilla suture in palatal view, posteromedially directed on its lateral half and anteromedially directed along its medial region, and the arched
orientation of the premaxillary tooth row.
PHYLOGENETIC ANALYSIS
To test the phylogenetic relationships of Meridiosaurus vallisparadisi, a comprehensive cladistic analysis
was performed. The analysis presented herein also
has the objective to test the monophyly of pholidosaurids. The phylogenetic analysis is based on an extension of the data matrix of Pol & Gasparini (2009).
Seven characters and three new taxa were added, and
the coding for some taxa were modified, based on
recent data or on a different interpretation (see
Appendix 1–3). Thus, the total data set is based on 62
taxa and 264 morphological characters. Six pholidosaurids are included in the analysis (Fig. 3): Elosuchus cherifiensis (Lavocat, 1955), Meridiosaurus
vallisparadisi, Oceanosuchus boecenis Hua et al.,
2007, Pholidosaurus purbeckensis, Sarsocusuchus
imperator, and Terminonaris robusta.
The phylogenetic data set was analysed with equally
weighted parsimony using TNT 1.1 (Goloboff et al.,
2008), with 1000 heuristic tree search replicates plus
tree bisection and reconnection (TBR) branch swapping, and holding ten trees per replicate. Zero-length
branches were collapsed if they lacked support (rule 1
of Coddington & Scharff, 1994). This analysis resulted
in a single most parsimonious tree of 910 steps (consistency index, CI = 0.35; retention index, RI = 0.70).
The most parsimonious hypothesis (Fig. 4) shows
the monophyly of Pholidosauridae, supported by
five unambiguous and eight ambiguous synapomorphies (see Appendix 4). The main reason for the
great number of ambiguous synapomorphies is
the high degree of missing data among pholidosaurids. Two main clades were formed, one grouping
Pholidosaurus as the sister taxon of Sarcosuchus and
Terminonaris, and the second grouping Oceanosuchus
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Figure 3. Pholidosaurids included in the phylogenetic analysis, and their relationships. Scale bars: 10 cm, except for
Meridiosaurus (5 cm).
as the sister taxon of Elosuchus and Meridiosaurus.
Figure 4 shows the phylogenetic relationships of
Pholidosauridae, calibrated on the temporal scale.
Non-pholidosaurid taxa follow the topology as
described in Pol & Gasparini (2009).
PALEOBIOGEOGRAPHY
Pholidosaurids were longirostrine crocodylomorphs
adapted to aquatic environments, but without as
many aquatic adaptations as Thalattosuchians and
Dyrosaurids (Buffetaut, 1982; Hua & Buffetaut, 1997;
Hua, 2008). In spite of the longirostrine proportions,
the relatively large limbs suggest the possibility of
ambulatory behaviour (Watson, 1911). Pholidosaurs
inhabited three different types of aquatic ecosystem.
Terminonaris and Oceanosuchus were probably
marine forms (Hua et al., 2007; Shimada & Parris,
2007), whereas the well-known species Pholidosaurus
and Sarcosuchus, along with Elosuchus and Meridiosaurus, where freshwater forms. However, the first
pholidosaurids were probably adapted to live in a
mixed environment. Anglosuchus was recovered from
the English Great Oolites limestones of Bathonian
age (Ziegler, 1990), interpreted as a mixing zone
between freshwater and marine waters (McLimans &
Videtich, 1989), and Crocodilaemus from the French
Cerin Lagerstätte of Kimmeridgian age, interpreted
as a near-shore lagoon with clear marine influence
(Gaillard et al., 2006). Even though they were not
true marine forms, these two species had at least the
ability to live in, or at least withstand, saltwater
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
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Figure 4. Temporally calibrated cladogram showing the phylogenetic relationships of Pholidosauridae. The ghost
lineages are in grey. 1, temporal range based on Sarcosuchus hartii. 2, temporal range based on two putative
pholidosaurids, Anglosuchus and Crocodilaemus. First appearances based on: Dyrosauridae, Buffetaut & Lauverjat (1978)
and Buffetaut, Bussert & Brinkmann (1990); Thalattosuchia, Buffetaut et al. (1981); other neosuchians, Tykoski et al.
(2002; Calsoyasuchus valliceps). Stratigraphic chart based on Ogg, Ogg & Gradstein (2008).
ecosystems. This ability may be the main factor for
the dispersal events in the biogeographic history of
the group.
Although the phylogenetic analysis presented here
has weak support on the internal nodes of Pholidosauridae, and its fossil record is fairly incomplete,
some considerations can be stated about its geographical distribution (Fig. 5). The paleobiogeographical history of Pholidosauridae shows wide temporal
lapses and sparse remains. Given the phylogeny presented here (Fig. 4), there is a long ghost lineage
through the Toarcian–Bajocian (c. 15 Myr). The oldest
record of the group is Anglosuchus, from the Bathonian of England, and Crocodilaemus, from the Kimmeridgian of France (Mook, 1942; Steel, 1973). It
suggests the group, or at least this lineage, originated
in Europe during the Middle Jurassic. This hypothesis is coherent with the biogeographical history of a
closely related group, the thalattosuchians. The oldest
record of teleosaurids are also from Europe (Buffetaut, Termier & Termier, 1981). In this scheme, the
biogeographical origin of the dyrosaurids may be
related to the European origin of pholidosaurids.
However, Dyrosauridae has a ghost lineage of at least
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
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D. FORTIER ET AL.
Figure 5. Paleogeographic map of the Late Jurassic
(modified from Paleogeographic Globes available at http://
jan.ucc.nau.edu/~rcb7/globehighres.html) indicating the
pholidosaurid localities and dispersion routes. See text
for explanation. Legend: 1, Pholidosaurus; 2, Terminonaris; 3, Sarcosuchus; 4, Oceanosuchus; 5, Elosuchus; 6,
Meridiosaurus.
65 Myr (this work), without record from the Middle
Jurassic to the Early Late Cretaceous. The known
dyrosaurid lineage, from Cenomanian (Buffetaut &
Lauverjat, 1978) to Early Eocene (Buffetaut, 1978a–
c), originated in northern Africa and then dispersed to
the south, following two possible dispersal routes
(Barbosa et al., 2008).
After the Middle–Late Jurassic endemism in
Europe, Pholidosauridae may have dispersed in a
relatively short period of time. During the Late
Jurassic–Early Cretaceous, the group may have dispersed to Africa and South America in two independent events: the first, a dispersion of the Sarcosuchus
lineage to Africa and South America (Fig. 5, black
dashed line); and the second, a dispersion of the
Elosuchus–Meridiosaurus lineage to Africa and southern South America (Fig. 5, dotted line). After the
break-up of Gondwana, the South American lineages
no longer persisted, as there is no confirmed Late
Cretaceous record in that continent (Gasparini, 1996;
Fortier & Schultz, 2009). In Europe, the group
remained until the Berriasian (Pholidosaurus; Salisbury, 2002), reappeared during the Early Cenomanian (Oceanosuchus; Hua et al., 2007), and had
completely disappeared by the Late Cenomanian (Terminonaris; Buffetaut & Wellnhofer, 1980).
The group may have dispersed to South America
during the Oxfordian–Kimmeridgian, or even earlier
(Toarcian), considering the ghost lineages involved.
However, there is no record in Africa until the appearance of Sarcosuchus in Aptian–Albian (Buffetaut &
Taquet, 1977). The group possibly inhabited Africa
during these 30 Myr, considering the Sarcosuchus
from the Neocomian of Brazil (Buffetaut & Taquet,
1977), but no trace remains. The same phenomenon
occurred in the Elosuchus lineage, showing a ghost
lineage from the Kimmeridgian to the Late Albian
(this work) of approximately 50 Myr.
Another dispersal event occurred in the Terminonaris lineage (Fig. 5, white dashed line). Terminonaris
is assumed to have been an inhabitant of marginal
marine environments (Shimada & Parris, 2007), thus
the dispersal through the narrow Atlantic Ocean was
possible. The genus first appeared in the Late Cenomanian from Germany (Buffetaut & Wellnhofer,
1980), after a long ghost lineage since the earliest
record of Sarcosuchus during the Berriasian (see
Fig. 4), and then dispersed to North America sometime in the Late Conomanian or Early Turonian. All
the specimens are from the Turonian, recorded in
USA (Osborn, 1904; Mook, 1934; Erickson, 1969;
Shimada & Parris, 2007) and Canada (Wu et al.,
2001). The group had a short but important history in
North America, as Pholidosauridae had its last record
there.
CONCLUSION
Meridiosaurus vallisparadisi Mones, 1980 is a valid
taxon and a member of Pholidosauridae, from the
Late Jurassic–Early Cretaceous Tacuarembó Formation, Uruguay. It represents one of the earliest species
and the southernmost record of the group. Also, it is
the most complete record of a pholidosaurid from
South America.
The phylogenetic hypothesis herein presented
confirm the monophyly of Pholidosauridae, redefined
here as a stem-based group name including Pholidosaurus schaumburgensis and all taxa closer to it than
to Dyrosaurus phosphaticus or Pelagosaurus typus,
and is diagnosed by several characteristics. However,
the relationships among members of Pholidosauridae
are weakly supported because of a high degree of
missing data. Certainly, this problem requires further
study, such as increasing taxon and character sampling. Putative pholidosaurids, like Anglosuchus and
Crocodilaemus, strongly need a reappraisal of their
anatomy in order to have phylogenetic relationships
recovered. The genus Pholidosaurus needs a systematic revision, as regards to the taxonomic status of P.
schaumburgensis and P. meyeri. Nevertheless, some
paleobiogeographical considerations can be stated.
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
Pholidosaridae probably originated in Europe
during the Middle Jurassic, and remained only there
until the Tithonian–Oxfordian, when two dispersal
events probably occurred to Africa and South
America. The group possibly inhabited Africa during
the Neocomian, but no trace was left. The record in
Africa ranges from Late Aptian to Early Cenomanian.
In Europe, the group remained until the Berriasian,
reappeared during the Early Cenomanian, and completely disappeared in the Late Cenomanian. Another
dispersal event occurred from Europe to North
America sometime in the Late Cenomanian or Early
Turonian, a time when Pholidosauridae disappeared.
There is no specific explanation for the Early Creataceous ghost lineage among Dyrosauridae and Pholidosauridae. For dyrosaurids, the temporal gap is even
longer. The reason that could be stated is the incompleteness of the fossil record or an incorrect phylogenetic hypothesis.
ACKNOWLEDGEMENTS
The authors thank Hans Larsson, Diego Pol, and two
anonymous reviewers for many suggestions that
improved the article, and Martín Ubilla (Departamento de Paleontología, Faculdad de Ciencias, Montevideo) for collection support. For access to and
assistance with comparative collections, we thank
Carl Mehling (American Museum of Natural History),
Richard Butler and Oliver Rauhut (Bayerische
Staatssammlung für Paläontologie und Geologie),
Peter Woodward (Dorset County Museum), Lorna
Steel (Natural History Museum) and Rainer Schoch
(Staatliches Museum für Naturkunde Stuttgart).
Financial support for this research was provided by
ANII-Uruguay (project number FCE2007-110) and
the Jurassic Foundation, for partial fieldwork support
(granted to DP), and CNPq (Proc. 490340/2006–7 –
PROSUL, granted to CS). DF also thanks CNPq and
CAPES for a PhD scholarship, and the University of
Iowa for lending its computational and bibliographical resources.
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APPENDIX 1
INSTITUTIONAL
ABBREVIATIONS AND LIST OF
REFERENCE PHOLIDOSAURIDAE USED IN THE
PHYLOGENETIC ANALYSIS
Collection numbers of the specimens that were
revised first-hand by the authors are added before the
bibliographic reference. Six pholidosaurids have been
considered in the present work, included in the data
matrix from Pol & Gasparini (2009).
AMNH, American Museum of Natural History,
New York, USA; BSP, Bayerische Staatssammlung
für Paläontologie und Geologie, Münich, Germany;
DORCM, Dorset County Museum, Dorchester, UK;
FC-DPV, Faculdad de Ciencias, Departamento de
Paleontología de Vertebrados, Montevideo, Uruguay;
MNHN, Museum National d’Histoire Naturelle,
Paris, France; NHM, Natural History Museum,
London, UK; SMNS, Staatliches Museum für
Naturkunde Stuttgart, Stuttgart, Germany.
Elosuchus cherifiensis: Lavocat (1955); Lapparent de
Broin (2002).
Meridiosaurus vallisparadisi: FC-DPV-2322 (formerly
SPV-FHC-27-II-78–1); Mones (1980).
Oceanosuchus boecenis: Hua et al. (2007); Lepage
et al. (2008).
Pholidosaurus schaumburgensis: DORCM G97; NHM
R3414; NHM R3956; NHM 28432; NHM 28966; Owen
(1878); Koken (1887; for P. meyeri and P. schaumburgensis); Mansel-Pleydell (1888); Watson (1911);
Andrews (1913); Salisbury (2002).
Sarcosuchus imperator: MNHN uncatalogued cast of
the holotype; Taquet (1976); Sereno et al. (2001).
Terminonaris robusta: AMNH 5849, AMNH 5850;
Osborn (1904); Mook (1933, 1934); Sereno et al.
(2001); Wu et al. (2001).
Steneosaurus bollencis: AMNH 5138, BSP 1890.I.510,
BSP 1945.XV.1, BSP 1949.XV.1, BSP 1972.V.11, BSP
1973.VII.592, SMNS 115, SMNS 4554, SMNS 9427,
SMNS 9428, SMNS 15951, SMNS 16848, SMNS
17484, SMNS 18878, SMNS 20280, SMNS 20282,
SMNS 20283, SMNS 53422.
Pelagosaurus typus: NHM R32599, BSP 1925.I.34,
BSP 1990.VIII.68, SMNS 8666, SMNS 80066, Pierce
& Benton 2006.
APPENDIX 2
LIST
OF CHARACTERS EMPLOYED IN THE
PHYLOGENETIC ANALYSIS
The following list presents the characters added in
the original data matrix from Pol & Gasparini (2009).
No modification was made to the original list. The
additional characters are listed here and their respective sources are cited along with the character
number of the original publication. These characters
were set as non-additive.
Character 258 (modified from Jouve, 2004; character
178): Anterior process of the frontal extending
far anteriorly, or slightly anteriorly, at the same level
(0) or posteriorly (1) to the anterior margin of the
orbits.
Character 259 (modified from Jouve, 2004; character
197): Posterior surface of basioccipital ventral to the
occipital condyle short and gently curved, lower than
the occipital condyle (0), or long, flat, and nearly
vertical, at least as high as occipital condyle (1).
Character 260 (Jouve, 2009; character 326): Medial
margin of the orbit in dorsal view: formed mostly by
the frontal (0), or mostly by the prefrontal, the frontal
is excluded or participates only slightly (1).
Character 261 (Jouve, 2009; character 341): Maximal
width of premaxillae less (0), or more (1) expanded
than the maximal width of the rostrum at the level of
alveoli 4 or 5.
Character 262 (Wu et al., 2001; character 114):
Maxilla terminating behind anterior margin of orbit
(0), or anterior to orbit (1).
Character 263 (Jouve, 2004; character 205): Distance
between the tip of the snout and the anteriomost
position of the premaxilla–maxilla suture in dorsal
view is larger (0), or smaller (1) than the distance
between the anteriormost position of premaxilla–
maxilla suture in dorsal view and the posterodorsal
extremity of the premaxilla.
Character 264 (modified from Jouve, 2004; character
3): Anterodorsal margin of the external nares with
small dorsal projection at the level of the suture
between right and left premaxillae (0), or without
premaxillary dorsal projection (1).
APPENDIX 3
LIST
OF CHARACTER SCORES
Coding for characters 258–264 of taxa from the original data set (Pol & Gasparini, 2009), and for all 263
characters of the three species included (Elosuchus
cherifiensis, Meridiosaurus vallisparadisi, and
Oceanosuchus boecensis) and five modified taxa
(Pholidosaurus purbeckensis, Sarcosuchus hartii, Terminonaris robusta, Steneosaurus bollensis and Pelagosaurus typus).
Gracilisuchus stipanicicorum???????
Terrestrisuchus gracilis???????
Dibothrosuchus elaphros 1010000
Protosuchus richardsoni 1000000
Hemiprotosuchus leali?1??0?0
Orthosuchus stormbergi 1000000
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
MERIDIOSAURUS, A PHOLIDOSAURID FROM URUGUAY
Kayenta form???0000
Edentosuchus tienshanensis 1?100??
Zaraasuchus shepardi???????
Gobiosuchus kielanae 11?0000
Sichuanosuchus shuhanensis 1?10000
Shantungosuchus hangjinensis?1?00??
Zosuchus davidsoni 110000?
Fruita form???????
Hsisosuchus chungkingensis 000?1??
Notosuchus terrestris 1100001
Comahuesuchus brachybuccalis 1000001
Mariliasuchus amarali 1?000??
Uruguaysuchus aznarezi 1?00001
Chimaeresuchus paradoxus???0?01
Malawisuchus mwakayasyunguti 1?1000?
Candidodon itapecurense???????
Simosuchus clarki 1100000
Sphagesaurus huenei???0001
Bretesuchus bonapartei???0000
Baurusuchus pachecoi???????
Iberosuchus macrodon???????
Lybicosuchus brevirostris?1?00?0
Araripesuchus gomesii 1100000
Araripesuchus patagonicus 110?0??
Araripesuchus buitreraensis???????
Araripesuchus wegeneri???????
Lomasuchus palpebrosus 11?000?
Peirosaurus torminni???0000
Theriosuchus pusillus 0?00001
Alligatorium???????
Metriorhynchus superciliosus 1010000
Metriorhynchus casamiquelai???????
Geosaurus araucanensis 1000000
Geosaurus suevicus???????
Dakosaurus maximus 1?00000
Dakosaurus andiniensis 0010000
Rhabdognathus 010?0??
Sokotosuchus ianwilsoni???????
Dyrosaurus phosphaticus 0100000
Hyposaurus rogersii???????
Goniopholis 1110000
Eutretauranosuchus delfsi 0?0?0??
Bernissartia fagessi 0?00001
Hylaeochampsa vectiana 110?0??
Borealosuchus formidabilis 010000?
Gavialis gangeticus 0001001
Crocodylus niloticus 0100001
Alligator mississippiensis 0100000
Pholidosaurus purbeckensis
212?121101??1??1110[01]10011?1001000101211
0101?01112?11?1010?10?100?131[12]???0???1?
0????1?2???0??0??200?????????0??0??????0?1
?1??10110?????0?001001??1???00??????000?00
10102?100????0?0000?0???000?00?10?0?10??01
?100?0010???0??????0??00???0?102?1011?1???
0?0001?0?00001101?
S271
Sarcosuchus imperator
203?12110100101?100010011001010001012?1010
1[01]01?12?1??10100?0?100?131213??00021010
1?112????[01]00?1200?00??010[01]0??00[01]0
01?0?101??121100??0000001001011???00???110
?0[02]11010[01]022100?0000?000000?000000?0
0?01001000?1?100?0010?00000000?0?0100000?1
00011110100?0?000100?101011111
Terminonaris robusta
202?[01]2?1010010?11??01001??01010001012?1
010[01]1??????11?1010??0??0??13[01][12]13?
000?2100011112??00000?1200?10??0?010210?10
01001101??12010??0??0?0010???11???00001110
0?0?1?101[01]2[12]10?????0?0000?0?0000?000
1?0?00?0?0?11100?00?0??00???00?0?0100?00?1
020111101?0?0?00?100??00011011
Meridiosaurus vallisparadisi
2?2?121111??11????????????????????????????
???????????????????????1???????????12?????
?????????????????????010???????????1??0?11
????????0?0010?????????????????????010????
???????0?1????11???0??????????????????0???
???????????????00???0????20?001??????????1
????????1?11
Elosuchus cherifiensis
203?12111100001?1??010????11????01012?????
??????????????0??????????1????????112?????
????????????0????????0????0??????0???1???0
10?????????????0?11???????????????0?1??02?
0????????1????1???????????????????????????
????????????????0????????2??001??????????1
?????1011101
Oceanosuchus boecensis
202?12110100101????11001???101??01012?????
??????????????0??????????1????????1?00???1
?????????????????????0????0??????0???1???1
10????????????????????????????????0?1??0??
?????????0????0???????????????????????????
????????????????0????????2??001??????????1
?????1011111
Steneosaurus bollensis
[02]02?[01]111?10011020100[01]000100000001
10021101000?0011011?1001011?1?00120103?000
?20000110111100000?120001[01]1?011?02100[0
1]001001101??10?10000??0?0010?1?00??000001
10000010000110?0001001000200?0?00000000010
1[12]01000[01]1100010010?0000000000?0010?0
0?100000000?1000010?0[01]01001001000
Pelagosaurus typus
202?[01]111?1001102010[01][01]00000000000[
01]1002110100000011011?1001001?10001201?30
0000200001101?1?00000012000111?011002100??
?101?101??1??10000??00001010100??[01]00???
100000??0001102000100?000200?0??0?0?000010
11010000110000001??0000000??0???10?00?10[0
1]00000021000[01]100110?00100?000
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272
S272
D. FORTIER ET AL.
APPENDIX 4
LIST
OF APOMORPHIES
The apomorphy list is provided here for Pholidosauridae and its internal nodes only. Legend: italicized,
ACCTRAN; underlined, DELTRAN; bold, unambiguous transformations.
Pholidosauridae
33(0), 57(0), 68(1), 78(1), 78(1), 106(0), 144(1), 145(1),
163(1), 241(1), 259(0), 260(1), 261(1), 263(1), 264(1)
Pholidosaurus + Sarcosuchus, Terminonaris
128(1), 142(1), 169(1), 240(1)
Pholidosaurus
2(1), 18(1), 28(0), 126(0), 256(0)
Sarcosuchus + Terminonaris
27(0), 77(2), 78(1), 126(2), 155(1), 161(1), 227(1),
239(1)
Sarcosuchus
3(3), 80(1), 100(0), 236(0), 256(1), 258(1), 262(1)
Terminonaris
100(1), 127(0), 193(1)
Oceanosuchus + Elosuchus, Meridiosaurus
N: 128(0), 142(0), 258(1), 262(1)
Oceanosuchus
20(1), 126(1)
Elosuchus + Meridiosaurus
9(1), 79(2), 178(1), 183(1)
Elosuchus
3(3), 13(0), 126 (0), 263(0)
Meridiosaurus
14(1), 126(1)
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, S257–S272