The largest thalattosuchian (Crocodylomorpha) supports teleosaurid
survival across the Jurassic-Cretaceous boundary
, Tetsuto Miyashita
, Luigi Cantelli
, Fawsi Mnasri
, Jihed Dridi
, Andrea Cau
Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Alma Mater Studiorum, Universit
a di Bologna, Via Zamboni 67, 40126 Bologna, Italy
Museo Geologico Giovanni Capellini, Alma Mater Studiorum, Universit
a di Bologna, Via Zamboni 63, 40126 Bologna, Italy
Department of Biological Sciences, University of Alberta, Edmonton, T6G 2E9 Alberta, Canada
Ofﬁce National Des Mines, Service Patrimoine G
eologique, 24 Rue de l'Energie 8601, La Charguia, 2035 Tunis, Tunisia
Museo Civico di Scienze Naturali Malmerendi, Via Medaglie d'Oro 51, 48018 Faenza, Italy
Received 18 July 2015
Received in revised form
5 November 2015
Accepted in revised form 15 November 2015
Available online xxx
A new teleosaurid from the Lower Cretaceous of Tataouine (Tunisia), Machimosaurus rex sp. nov.,
deﬁnitively falsiﬁes that these crocodylomorphs faced extinction at the end of the Jurassic. Phylogenetic
analysis supports its placement closer to M. hugii and M. mosae than M. buffetauti. With the skull length
up to 160 cm and an estimated body length of 10 m, M. rex results the largest known thalattosuchian, and
the largest known crocodylomorph at its time. This giant thallatosuchian probably was an ambush
predator in the lagoonal environments that characterized the Tethyan margin of Africa during the earliest
Cretaceous. Whether the Jurassic-Cretaceous mass extinction was real or artefact is debated. The dis-
covery of M. rex supports that the end-Jurassic crisis affected primarily Laurasian biota and its purported
magnitude is most likely biased by the incomplete Gondwanan fossil record. The faunal turnovers during
the J-K transition are likely interpreted as local extinction events, t riggered by regional ecological factors,
and survival of widely-distributed and eurytypic forms by means of habitat tracking.
© 2015 Elsevier Ltd. All rights reserved.
The Jurassic-Cretaceous (J-K) transition has been considered a
complex phase of global extinctions in both terrestrial and marine
faunas, which affected rates of lineage diversiﬁcation and
morphological evolution during the Early Cretaceous (Bakker, 1978,
1998; Sepkoski, 1984; Bardet, 1994; Benton, 2001; Upchurch and
Barrett, 2005; Lu et al., 2006; Benson et al., 2010). Whether this
event was real (i.e., a complex combination of clade-speciﬁc
extinction patterns driven by physical and biotic factors) or repre-
sents an artefact remains unresolved (Gasparini et al., 2004;
Bambach, 2006; Benson et al., 2010; Ruban, 2012; Newham et al.,
2014). Among speciose clades of Jurassic marine reptiles, tele-
osauroid crocodylomorphs stand as the sole that supposedly went
extinct at the Jurassic-Cretaceous boundary (Young et al., 2014a),
with all purported Cretaceous remains re-interpreted as belonging
to other reptilian clades, in particular, to the other thalattosuchian
clade, Metriorhynchoidea (Young et al., 2014a,b). From a palae-
ogeographic perspective, Teleosauroidea is known largely from
Europe (Vignaud, 1995), with Gondwanan remains rare, often
limited to problematic or extremely fragmentary specimens (e.g.,
Martin et al., 2015; Young et al., 2014a).
In December 2014, the articulated remains of a giant croc-
odylomorph were found during prospecting activities at the Touil el
Mhahir locality, Tataouine Governorate, Tunisia (Figs. 1, 2 ). In this
study, we describe this new specimen and determine its afﬁnities
and stratigraphic placement. The results of our analyses support
the erection of a new species of thalattosuchian teleosaurid,
Machimosaurus rex. Furthermore, we discuss the implications of
this new African taxon in the debate on the end-Jurassic biotic
2. Material and methods
Specimens collected at the Touil el Mhahir locality in 2014 are
housed in the Mus
ee de l'Ofﬁce National Des Mines (Minist
l’Industrie et de la Technologie, Tunis), under the accession
* Corresponding author. Dipartimento di Scienze Biologiche, Geologiche
e Ambientali, Alma Mater Studiorum, Universit
a di Bologna, Via Zamboni 67, 40126
E-mail address: email@example.com (A. Cau).
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/CretRes
0195-6671/© 2015 Elsevier Ltd. All rights reserved.
Cretaceous Research xxx (2015) 1e12
Please cite this article in press as: Fanti, F., et al., The largest thalattosuchian (Crocodylomorpha) supports teleosaurid survival across the
Jurassic-Cretaceous boundary, Cretaceous Research (2015), http://dx.doi.org/10.1016/j.cretres.2015.11.011
numbers ONM NG 1e25, 80, 81, and 83e87. Microvertebrate fossils,
ﬁeld notes and locality coordinates, and the 3D data are housed at
the Museo Geologico Giovanni Capellini (MGGC, Bologna, Italy).
Assemblage data were interpreted from the ﬁnal quarry map as
well as from ﬁeld notes: all elements were mapped using a 1 m
grid box. Following the discovery of small elements from the sur-
face of the outcrop, a total of 2.5 kg of sandy and clayish sediments
were collected from both the excavation site and the matrix sur-
rounding the skull for screen washing. Samples were soaked with
water and H
(5%) and screened using progressive sieves of
1 mm, 200
m, and 63
m. With 100% of collected matrix screened
and sorted, a total of 231 specimens were identiﬁed. The collected
specimens were primarily identiﬁed and compared with those
described and illustrated by Cuny et al. (2004), Cuny et al. (2010)
(Early Cretaceous of southern Tunisia), and Pouech et al. (2015)
(Berriasian of France). Furthermore, during the preparation of the
skull, four displaced osteoderms lying slightly imbricated on the
snout were recovered and prepared (ONM NG 14-17).
The taxonomic content of the genus-level ranked clade Machi-
mosaurus von Meyer, 1837, is controversial. Young et al. (2014a,b)
recognised four species of Machimosaurus: M. buffetauti Young
et al., 2014b, M. hugii von Meyer, 1837, M. mosae Sauvage and
enard, 1879, (all from Europe) and M. nowackianus (von Huene,
1938) (from Ethiopia). Martin et al. (2015) challenged the distinc-
tion among the ﬁrst three species suggested by Young et al.
(2014a,b), referring all European Machimosaurus to M. hugii, and
considered M. nowackianus as a nomen dubium. We follow the
distinction among the species of Machimosaurus as suggested by
Young et al. (2014b) since both morphological and stratigraphic
disparities among the three European morphotypes support a
species-level distinction among them, and tested whether the in-
clusion of the new Tunisian material in a phylogenetic analysis of
Teleosauroidea further supports or challenges a taxonomic
distinction among the European Machimosaurus.
2.2. Phylogenetic analysis of Thalattosuchia
In order to analyse the evolutionary af ﬁnities of the Tunisian
thalattosuchian, we performed Bayesian inference methods inte-
grating the morphological and stratigraphic data with BEAST
(Rambaut and Drummond, 2009; Drummond et al., 2012) following
the method of Lee et al. (2014). The morphological dataset is based
on Young (2014) and modiﬁed by Cau (2014) after the a priori
exclusion of all non-thalattosuchian taxa. As branch duration esti-
mation and cladogenesis timing using Bayesian inference requires
sampling among both constant characters and autapomorphies of
terminal taxa e not solely among synapomorphies of internodes
(Lee et al., 2014) e
we retained all characters of the dataset of Young
(2014), including those resulted phylogenetically uninformative by
the a priori removal of most crocodyliform taxa from the ingroup.
The ingroup was consequently expanded by the inclusion of
Machimosaurus buffetauti (based on Martin and Vincent, 2013, and
Young et al., 2014b) and the new Tunisian thalattosuchian. One
Triassic pseudosuchian closely related to Crocodylomorpha (Post-
osuchus Chatterjee, 1985) and one basal crocodyliform (Protosuchus
Brown, 1934) were used as outgroups e with the former set as root
of the trees e according to the recent revision of thalattosuchian
afﬁnities by Wilberg (2015) indicating a non-crocodyliform place-
ment for Thalattosuchia. Stratigraphic data and age constraints for
each terminal were obtained primarily from the Paleobiology
Database (http://paleobiodb.org/) and from the literature, using
Fig. 1. (A) Geographic location and type locality of M. rex. (B) Simpliﬁed geological map of the Tataouine basin of southern Tunisia showing the Touil el Mhahir locality.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e122
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Jurassic-Cretaceous boundary, Cretaceous Research (2015), http://dx.doi.org/10.1016/j.cretres.2015.11.011
provided geochronological ages for the formations in which the
taxa were found or the mean of the geologic stages associated with
those formations. The root age prior (i.e., the maximum age of the
last common ancestor of all included taxa) was set along a uniform
range between 218 Mya (the age of the oldest terminal included,
Postosuchus) and 252 Mya (the Permian-Triassic boundary). The
latter was considered as a ‘loose’ hard constraint that consistently
pre-dates the age of the oldest potential crocodylomorphs and
basal loricatans. In the analysis, rate variation across traits was
modelled using the gamma parameter, and rate variation across
branches was modelled using an uncorrelated relaxed clock. The
analyses used four replicate runs of 40 million generations, with
sampling every 4000 generations. Burnin was set at 20%, and the
Maximum Clade Credibility Tree (MCCT) of the merged four post-
burnin samples was used as framework for phyletic reconstruction.
2.3. 3D photogrammetry and modelling
During the last decade, the development of Structure from
Motion (SFM) techniques has been dramatically improved allowing
accurate reconstruction of 3D structures processing 2D images
(Koenderink and Doorn, 1991; Beardsley et al., 1996; Trucco and
Verri, 1998; Dellaert et al., 2000; Haming and Peters, 2010; Fanti
et al., 2013; Engel et al., 2014; Fanti et al., 2015). We acquired dig-
ital models of the Machimosaurus quarry, the skull (both dorsal and
ventral views), and the prepared dorsal vertebrae, using high-
resolution photogrammetry. We used Agisoft PhotoScan Profes-
sional, and Meshlab for this technique. The models were built as in
the following procedure: 1. positioning of coded targets so that 70%
of photos frame at least one target (actual distances between tar-
gets will serve to include accurate measurement tools in the
model); 2. proper preparation of the light so that variations in the
enlightenment are minimal; 3. prearrangement of a photo-
shooting path. In order to properly perform the metric recon-
struction in the 3D model, it was mandatory to work with a camera
with a ﬁ xed focal length lens. The lens proﬁle for Agisoft Photoscan
was set using the software Agisoft lens. Automatic check of images
veriﬁed the complete coverage of selected objects before pro-
ceeding with the alignment of frames that originated the ﬁrst point
cloud based on corresponding points recognized in different
photos. Once the consistency of the generated surface were veri-
ﬁed, a photographic texture was generated.
3. Stratigraphy and age
The Touil el Mhahir locality (the exact locality data can be ob-
tained upon request) is located less than 50 km to the south-west of
the city of Tataouine and about 25 km to the north-west of Remada
(Fig. 1). Substantial erosion resulted in a badland-like morphology
that exposed the basal beds of the Douiret Formation, and in
particular of the Douiret Sand Member. In the Tataouine Basin, the
Douiret Formation uncoformably overlays the Boulouha Formation
which has been assessed a Barremian age based on the occurrence
of the Cretaceous brachiopod Loriolithyris russillensis (De Loriol,
1866), in the upper beds of the unit (Peybernes et al., 1996; Ouaja
et al., 2004; Bodin et al., 2010). However, recent re-evaluation of
stratigraphic and biostratigraphic data in southern Tunisia and
western Lybia (Cuny et al., 2010; Le Loeuff et al., 2010; Fanti et al.,
Fig. 2. Machimosaurus rex quarry map. Ortographic images of the 3D photogrammetry-based model of the main quarry in natural light (A) and with superimposed collected
elements (B). Abbreviations: cv, cervical vertebrae; dr, dorsal ribs; dv, dorsal vertebrae; ﬂ, forelimb bones; pe, pelvic elements; sk, skull; tp, turtle hyoplastron.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e12 3
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2012) placed the lower, sandy deposits of the Douiret Formation in
the Barremian. Speciﬁcally, the age of the Douiret Formation has
been assessed primarily through a detailed, basin-scale revision of
the stratigraphic occurrence and lateral variability of fossil-bearing
strata (Fanti et al., 2012). The occurrence of the hibodontid Eger-
tenodus Maisey, 1987, and Gyrodus Agassiz, 1833, in the Douiret
Formation supports an Hauterivian-Barremian age for this unit. In
fact, Rees and Underwood (2008) indicate the latest ascertain re-
cord of Egertenodus in the Barremian of Spain, and Kriwet and
Schmitz (2005) note the youngest record of Gyrodus in the Hau-
terivian of Germany. Therefore, although a pre-Hauterivian age of
the lower Douiret beds cannot be excluded, based on 1) the Early
Cretaceous age of the Boulouha Formation, and 2) stratigraphic and
biostratigraphic data provided by Cuny et al. (2010), Le Loeuff et al.
(2012), and Fanti et al. (2012), we conservatively consider the age of
the Touil el Mhahir locality as Hauterivian-Barremian.
The deposits are characterized by repeating, ﬁning-up se-
quences of ﬁne-grained sand and clay, capped by an alternating
sequence of clay and dolostone or dolomitized sandstone. The M.
rex quarry is located approximately 20 m above the fossil-rich
conglomerate that, on a basin scale, marks the base of the
Douiret Formation (Fanti et al., 2012). Furthermore, we report iso-
lated teeth of Machimosaurus sp. occurring in several localities from
the Douiret Formation deposits along the Dahar Escarpment (i.e. El
Hmaima, Jebel Haddada, Boulouha localities; Fanti et al., 2012)of
southern Tunisia, supporting that this genus is a representative of
4. Taphonomy and paleoecology
The type specimen of Machimosaurus rex represents the ﬁrst
articulated vertebrate from the Douiret Formation and the second
Mesozoic archosaur skeleton collected in Tunisia (Fanti et al., 2012,
2013, 2015). The skeleton lies on its ventral side with the head
rotated clockwise toward the right side of the body (Figs. 2e4).
Only three teeth were found preserved in the alveoli (Fig. 5),
whereas seven were shed along the snout. Although preserved el-
ements show no evidence of major pre-burial transportation
(Figs. 2e8A), the overall posture (i.e. the body lying on its ventral
side and the head curved on the right side of the body) combined
with displacement of osteoderms and the missing anterior end of
the snout strongly suggest that there was some inﬂuence from
paleocurrents (paleoﬂow from the south-east). In addition, the
right side of the skull is laterally compressed (see also the tapho-
nomic model of Syme and Salisbury, 2014). The dorsal part of the
skeleton was found partially eroded with the exception of the skull,
which lay slightly below ground level. Large turtle plastron ele-
ments were collected near the skull (Fig. 7E). The skull, two dorsal
vertebrae, several dorsal rib and gastralia fragments, a partial hu-
merus and osteoderms were collected during the excavation. The
remaining part of the quarry was mapped and isolated elements
littering the ground were collected.
The M. rex holotype was collected in association with abundant,
disarticulated elements from large turtle carapaces, plastrons and
vertebrae. The largest turtle elements, including a 25 cm long
hyoplastron associated with the skeleton (Fig. 7E), suggest an in-
dividual close to 1 m in body length. Because most of the turtle
elements were slightly above the type skeleton of M. rex, these
elements can be attributed to a subsequent depositional event.
Microvertebrate remains are representative of brackish and marine
taxa and include elasmobranchs, actinopterygians, dipnoans and
rare pterosaur teeth. Bivalves, gastropods, fragmentary echinoids
shell and spines, and scaphopods are also abundant.
In terms of relative percentage, ﬁsh elements (teeth, scales and
centra) represent 71% of the isolated elements; crocodilian (teeth
and osteoderms) 10%; invertebrates (gastropods, bivalves, and
echinoderms) 4%; elasmobranchs 3%; and the remaining 12% con-
sists of unidentiﬁable bony elements and teeth. Signiﬁcantly,
several teeth less than 5 mm in apicobasal length and a 4 mm wide
osteoderm are otherwise morphologically similar to those
described for Machimosaurus; the teeth are referred to the latter
taxon based on shared presence of blunt apex and anastomosing
apicobasal ridges on tooth crown. In addition, a partial dentary with
in situ teeth referable to a juvenile individual of Machimosaurus was
recovered in association with the type skull of M. rex. Prospecting
activities in the area revealed the presence of four additional
crocodylomorph individuals comparable in size and overall pres-
ervation to the M. rex holotype within 200 m from the main quarry.
The lower beds of the Douiret Formation are also rich in
megaplant remains, including large gypsiﬁed and sporadic hema-
tized trunks reaching 8 m in length. Remarkable fossil abundance in
the area and recurrent tree trunks indicate high rates of sediment
supply and accumulation: however, the lack of in situ plant roots
and organic components in the sediments combined with gypsiﬁed
fossils and dolomitized sandstones indicate arid to xeric environ-
ments subject to evaporitic conditions. Overall, facies analysis and
faunal assemblage are interpreted as a vast lagoonal system with
both marine and terrestrial inﬂuences.
5. Systematic paleontology
Crocodylomorpha Hay, 1930
Thalattosuchia Fraas, 1901
Teleosauridae Saint-Hilaire, 1831
Machimosaurus von Meyer, 1837
Machimosaurus rex sp. nov.
(ZooBank code: LSID urn:lsid:zoobank.org:act:1A11E9B9-0B1C-
Etymology. The species name rex, Latin for “king”, refers to its
majestic size among known
Machimosaurus and all
Holotype. ONM NG NG 1e25, 80, 81, and 83e87 (Figs. 2e7D;
Locality and horizon. Touil el Mhahir, Tataouine Governorate,
Tunisia; Douiret Sand Member, Douiret Formation, Hauterivian,
Diagnosis. Teleosaurid differing from other species by unique
combination of: adult basicranial length >155 cm (Fig. 5); rostrum
ornamented by densely arranged, parallel longitudinal ridges; orbit
elliptical; interorbital space narrow (one ﬁf th length of skull pos-
terior to orbit); anteromedial margin of supratemporal fossae
round; frontal not extended anteriorly to orbit and with reduced
orbital margin; relatively large maxillary alveoli; anterior dorsal
neural spine height less than centrum height; dorsal osteoderms
with tightly packed pits that are round centrally and ellipsoid
Differential diagnosis. Among the genus Machimosaurus (Fig. 8),
M. rex differs from M. buffetauti (Fig. 8A) in having relatively larger
and more closely spaced alveoli, and in bearing apicobasally aligned
enamel ridges immediately adjacent to the apical anastomosed
region of crown teeth that are closely packed on both labial and
lingual sides; from M. hugii (Fig. 8C) in showing more developed
ornamentation on maxillae and nasals, elliptical orbits, narrower
interorbital space, and dorsal osteoderms with more closely spaced
pits that become more elongate peripherally; from M. mosae
(Fig. 8B) in bearing elliptical orbits and shallower and unkeeled
F. Fanti et al. / Cretaceous Research xxx (2015) 1e124
ventral osteoderms. There is currently no overlapping material
between M. nowackianus and M. rex for a direct morphological
comparison. Although stratigraphic placement alone cannot be
used as a taxonomic criterion, based on stratigraphic separation
between the two type localities of M. nowackianus and M. rex (the
former is Oxfordian-Kimmeridigian in age, see Young et al., 2014b),
we consider likely these two African species as distinct.
6. Description of Machimosaurus rex type specimen
6.1. Skull and mandible (Figs. 3e7A)
The anterior end of the snout is missing. Based on comparison
with other specimens of Machimosaurus (Hua, 1999; Martin and
Vincent, 2013; Young et al., 2014a,b), we estimate that approxi-
mately posterior two thirds of the maxillae are intact. The pre-
served parts are ornamented with a dense pattern of lightly
developed longitudinal ridges (Fig. 5A). Eight alveoli are preserved
in the right maxilla (Fig. 5C). They are relatively large, their diam-
eter being up to one sixth of snout width, and are closely spaced
(Martin and Vincent, 2013; Young et al., 2014b). The interalveolar
space is regular, as in the mid- and posterior part of the maxilla of
M. hugii and M. mosae. The nasal is subtriangular in dorsal view and
ornamented by a ﬁnely developed pattern of longitudinal ridges. It
does not reach the narial region anteriorly. The periorbital region is
poorly preserved, with only fragmentary prefrontals and lacrimals
present. Nevertheless, the preserved outline indicates elliptical
orbits, more like that in M. buffetauti, differing from the more
quadrangular shape observed in both M. hugii and M. mosae (Young
et al., 2014b). The lateral margins of the orbits are at the level of the
anteromedial corners of the supratemporal fossae, relatively much
closely placed than in M. hugii (Young et al., 2014b, ﬁg. 41). The
nasofrontal suture is at the level of the anterior margin of the orbit.
The anterior end of the dorsal interfenestral bar is preserved, but
most of the bar, including the parietal, is lost. The anterior margin of
the supratemporal fossa is gently rounded. The posterior ﬂoor of
the supratemporal fossae is partially preserved. The postorbital is
robust and elongate posteriorly. Only the lateral part of both
squamosals is preserved. The occipital region of the skull is pre-
served in numerous fragments. Nevertheless, the occipital condyle
was preserved in situ, allowing an accurate estimation of the pre-
served basicranial length. The occipital condyle (Fig. 7A) consists
exclusively of the basioccipital, as in other species of Machimosau-
(Young et al., 2014b). The posterior ends of both dentaries are
preserved in articulation with the postdentary bones. The external
mandibular fenestra is elongate anteroposteriorly. Both the left and
right surangulars are articulated with the glenoid region. The an-
gulars are in fragments. The retroarticular processes are elongate
posteriorly and triangular in dorsal view. The teeth (Fig. 6)have
several diagnostic features for Machimosaurus (Young et al., 2014c).
The relatively low crowns are blunt apically and slightly curved
apicodistally. No carinae are present, suggesting that all preserved
teeth belong to the posterior half of the tooth row. The crowns are
ornamented with tightly packed ridges oriented apicobasally. As in
M. hugii, and differing from M. buffetauti (Young et al., 2014c), these
Fig. 3. Machimosaurus rex type skull, (A) dorsal view, (B) ventral view. Abbreviations: d, dentary; fr, frontal; lj, left jugal; la, lacrimal; mal, maxillary alveoli; mx, maxilla; na, nasal;
pa, palatal element; pdb, postdentary bones; posq, postorbital-squamosal bar; rap, retroarticular process; sa, surangular; stfo, ﬂoor of supratemporal fossa. Scale bar 50 cm.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e12 5
Fig. 4. Machimosaurus rex type skull, (A) in situ photograph showing dorsally exposed preserved bones, (B) prepared ventral surface. Abbreviations: fr, frontal; lj, left jugal; la,
lacrimal; ld, left dentary; lmx, left maxilla; lna, left nasal; lpd, left postdentary elements; lposq, left postorbitalsquamosal bar; os, osteoderm; pa, palatal element; rd, right dentary;
rmx, right maxilla; rna, right nasal; rpd, right postdentary elements; rposq, right postorbital-squamosal bar; stfo, ﬂoor of supratemporal fossa; tp, turtle plastron element. Scale
bar ¼ 50 cm.
Fig. 5. Detail of M. rex type snout in dorsal (A, B) and ventral (C, D) views. Abbreviations: d, dentary; dt, dentary tooth; fr, frontal; ju, jugal; la, lacrimal; lmx, left maxilla; na, nasal;
prf, prefrontal; rmx, right maxilla. Scale bar in C ¼ 5 cm.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e126
ridges are closely packed on both labial and lingual sides of the
crown. The ridges are irregularly undulated, but not producing
distinct pseudo-tubercles as in M. hugii (Young et al., 2014a,b). The
ridges are anastomosed in the apical third of the crowns, forming a
complex network as in other species of Machimosaurus. Most teeth
show a distinct (macroscopical) apical wear.
6.2. Postcranial skeleton (Figs. 2, 7BeD)
The cervical series is poorly preserved. Few fragments of the
atlas-axis complex were recovered adjacent to the occipital region
of the skull. Two well-preserved anterior dorsal vertebrae have
massive centra that are as wide as tall in anterior view (Fig. 7B). The
articular facet of the centra are subcircular and moderately concave.
The lateral surfaces of the centra are both dorsoventrally and
anteroposteriorly concave, due to the marked lateral rims of the
articular facets. The neural arch is transversely wide and low
dorsoventrally and has closely joined diapophyses and para-
pophyses that are oriented subhorizontally. The parapophyses
extend laterally to half the extent of the diapophyses, with their
articular surfaces facing posterolaterally. The dorsal surface of the
transverse process is anteroposteriorly convex. The ventrolateral
surfaces of the neural arches are moderately concave centrally. The
neurocentral suture is obliterated, suggesting a mature individual.
The zygapophyses are stout and moderately projected ante-
roposteriorly, being placed lateral to the neural canal and medial to
the centrum outline in anterior/posterior views. The neural spine is
robust, lower dorsoventrally than the height of the centrum and
moderately expanded transversally at its apex. Several dorsal ribs
and gastralia were found in articulation, although extremely
Appendicular elements include fragments of the left forelimb,
interpreted as the humeral shaft, and worn elements that, based on
in situ placement posterior to the dorsal ribs series, are interpreted
as belonging to the hindlimb.
6.3. Osteoderms (Fig. 7C, D)
Isolated osteoderms were found adjacent to the lower jaws. As
the skull is turned backward relative to the presacral vertebral
column, the osteoderms are interpreted as pertaining to the dorsal
region. The osteoderms are quadrangular, with poorly developed
anterolateral processes. Osteoderm ornamentation includes a
tightly packed pattern of rounded pits in the central part of the
dorsal surface, surrounded peripherally by radially elongate pits
that reach the margin of the osteoderm; this pitting pattern differs
from the more irregular pattern reported by Young et al. (2014b) for
Machimosaurus hugii. Furthermore, none of the recovered osteo-
derms bears the marked thickening and the distinct keel both
diagnostic of Machimosaurus mosae (Hua, 1999).
7.1. Phylogenetic analysis
The MCCT of Thalattosuchia resulted by the Bayesian phyloge-
netic analysis (Fig. 9) agrees in overall topology with previous an-
alyses of the same dataset using parsimony as tree search strategy
(e.g., Young 2014). The analysis strongly supports the monophyly of
Machimosaurus (posterior probability: 97%) and the inclusion of the
new Tunisian taxon in that genus. Machimosaurus buffetauti
resulted the basalmost member of the genus, excluded from the
clade including M. rex and the other European species (posterior
probability: 63%). The analysis therefore supports the distinction of
M. buffetauti from other Machimosaurus suggested by Young et al.
(2014a). Cladogenetic timing estimated by the Bayesian analysis
places the divergence of the lineage leading to M. rex from the other
Machimosaurus lineages at about 155 Mya.
8. Size of
8.1. Skull length
The skull of the type specimen of M. rex lacks the anterior end of
maxillae and the premaxillae. The basicranial length of the pre-
served skull is 114 cm, the length of the preserved skull from the
Fig. 6. Dentition of M. rex type. Isolated tooth crowns in labial (A, D) and lingual (B, E)
views; (C) detail of enamel close to apex. Arrows indicate tubercle-like ornamentation
of ridges. Scale bar ¼ 5 cm.
Fig. 7. Skeletal anatomy of M. rex sp. nov. type specimen and associated turtle remains.
(A) Occipital condyle in dorsal view. (B) Anterior dorsal vertebra in anterior view.
(CeD) Osteoderms in dors al views. (E) Turtle hyoplastron in visceral view. Scale bars
AeD ¼ 5 cm; E ¼ 10 cm.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e12 7
anterior end to the left mandibular glenoid is 134 cm. The length of
the skull from occiput to the anterior end of the orbits (‘post-snout’
length) is 65 cm. In a complete skull of M. buffetauti with a basi-
cranial length of 93.5 cm (Kimmeridgian, Germany; Martin and
Vincent, 2013; Fig. 8A), the equivalent part of the skull is 39 cm
long (42% of basicranial length). In other specimens of Machimo-
saurus, the snout length of the skull is approximately 58% of the
basicranial length, a value that is considered as an autapomorphy of
Machimosaurus (Hua, 1999; Young et al., 2014b; Fig. 8B). That im-
plies a 'post-snout' length of about 42% of the skull length in this
taxon (see also Martin and Vincent (2013), table 6). Assuming that
the proportions of the complete skull of M. rex holotype were
comparable to those observed in other Machimosaurus species, we
estimate a minimum total basicranial length for the Tunisian taxon
of 155 cm. Prior to this discovery, the largest size of Machimosaurus
was based on a fragmentary skull of M. hugii (the “Leira specimen”
of Young et al. 2014b, see Krebs (1967), Fig. 8C) with the basicranial
length estimated between 141 cm (Hua, 1999) and 149 cm (Young
et al., 2014b). Nevertheless, the “Leira specimen” lacks most of
the orbital and temporal regions, and no measurements of the
preserved elements are available, thus preventing any testable
estimation of its actual size (see Krebs, 1967).
A comparison between the size of the alveoli in M. rex type
specimen and other Machimosaurus individuals further supports
the giant size of the Tunisian taxon. In the skull of M. buffetauti type
specimen (Martin and Vincent, 2013), the mesiodistal diameter of
the alveoli at mid-length of the maxilla is between 15 and 18 mm.
In the neotype of M. mosae, the middle maxillary alveoli diameter
ranges between 18 and 25 mm (Hua, 1999). In the type specimen of
M. rex, the mesiodistal diameter of the middle maxillary alveoli
ranges between 30 and 43 mm, a value 200% or more than those of
M. buffetauti holotype, and about 166e173% larger than those in the
M. mosae neotype. The latter range conﬁ
rms that the basicranial
length of the Tunisian specimen is at least 166% larger than that of
the M. mosae neotype. Since the type skull of M. rex is also esti-
mated about 165e170% the size of the M. buf fetauti type skull
(Martin and Vincent, 2013), the Tunisian species shows propor-
tionally larger alveoli than in M. buffetauti.
8.2. Total body length
Young et al. (2014b) used the well-preserved neotype specimen
of M. mosae to estimate the total body length of various specimens
of Machimosaurus from their basicranial lengths, assuming a body
length to basicranial length ratio of about 6.22. Assuming isometry
among the various Machimosaurus individuals, and using the same
relationships of Young et al. (2014b), the total body length of M. rex
type is estimated at least as 9.6 m. Compared to the neotype of
M. mosae, the alveoli in M. rex holotype are about 166% larger than
the same element in the French specimen (Hua, 1999). Therefore,
assuming isometry in body proportions, based on both cranial and
dental comparisons with the best preserved specimen of Machi-
mosaurus mosae (Hua, 1999) the total body length of the Tunisian
Fig. 8. Comparison among skulls of Machimosaurus. (A) holotype of M. buffetauti, (B) neotype of M. mosae, (C) estimated size of the ‘Leira specimen’ of M. hugii, (D) holotype of
M. rex. Dashed areas in (A) and (B) indicate size of largest known individuals of those species. (E) Reconstruction of M. rex body based on preserved elements. Figures (A)e(C)
modiﬁed from Young et al. (2014b).
F. Fanti et al. / Cretaceous Research xxx (2015) 1e128
individual is estimated at about 10 m (166% of 6 m, see Young et al.,
2014b; Fig. 8E).
9.1. Hypothetical lifestyle
The skull of M. rex bears a platyrostral snout, longitudinally
oriented ornamentations on the skull roof, elongate subrectangular
supratemporal fossae and blunt-crowned teeth with anastomosed
apical enamel ornamentation (Figs. 1, 2), all synapomorphies of
derived teleosaurids (Young et al., 2014b). With the skull length up
to 160 cm and an estimated body length around 10 m (Fig. 8E), the
new Tunisian species is the largest known thalattosuchian, and was
the largest known crocodylomorph from the Triassic until the
Aptian-Albian (see Young et al., 2014b, Johnson et al., 2015). As in
other Machimosaurus (in particular, M. hugii, Young et al., 2014b,c),
the low-crowned, sub-globidont dentition of M. rex supports a
generalist-durophagous feeding ecology. The abundance of turtle
remains in the M. rex quarry, including large-bodied forms with
length approaching 1 m, suggests that chelonians were a signiﬁcant
part of the diet also in the Tunisian taxon.
Krebs (1967) and Hua (1999) discussed the hypothetical life-
styles of M. hugii and M. mosae respectively (see also the review by
Young et al., 2014b). The former was interpreted as well-adapted to
an open sea environment, whereas the latter resulted better
adapted to high-energy, coastal conditions. Based on extant ana-
logues among crocodilians showing an inverse relationships be-
tween dermal ornamentation and aquatic adaptation, the relatively
reduced ornamentation in both skull roof and osteoderms of
Machimosaurus hugii has been suggested as additional functional
adaptation to a pelagic lifestyle (Young et al., 2014b). Similarly, the
thick and keeled ventral osteoderms of M. mosae are interpreted as
adaptations to a high-energy/turbulent environment (Hua, 1999;
Young et al., 2014b). In M. rex, both skull roof ornamentation and
extent of pitting on the osteoderms are more developed than in
M. hugii. The relatively shallower osteoderms lacking a keel suggest
that the Tunisian species was not adapted to a high-energy envi-
ronment as that inferred for M. mosae. This interpretation is
consistent with the paleoecology of the M. rex type locality (see
above) indicating a lagoonal environment with signiﬁcant terres-
In analogy with modern semi-aquatic crocodilians, we suggest
that M. rex was an ambush predator that preyed on both aquatic
and terrestrial vertebrates. Since Machimosaurus bite marks on a
sauropod dinosaur bone are already known (
Young et al., 2014b),
we predict that M. rex included mid- to large-bodied dinosaurs in
9.2. Implications for teleosaurid extinction
Unlike their survival into the Cretaceous of southern Tethys,
teleosaurids did not cross the J-K boundary in the northern realm
(Young et al., 2014a,b). The Late Jurassic species of Machimosaurus
occur from Portugal to Germany to Ethiopia in lagoonal to shallow
marine settings (Young et al., 2014b). These environmental condi-
tions existed well into Cretaceous times in southern Tunisia, where
lagoonal to tidal ﬂats deposits straddle the J-K transition and
dominate the Lower Cretaceous sedimentary successions (Benton
et al., 2000; Barale and Ouaja, 2002; Ouaja et al., 2004; Anderson
et al., 2007; Ouaja et al., 2011; Fanti et al., 2012). Conversely, the
end-Jurassic transition in Europe is characterized by rapid climatic
oscillations (alternation of ‘greenhouse’ conditions and cooling
events) and concomitant extension of pelagic environments with
dramatic loss of shallow marine and coastal ecosystems (Adatte
et al., 1996; Cecca, 1999; Cecca et al., 2001; Dromart et al., 2003;
ecuyer et al., 2003; Cecca et al., 2005; Husinec and Jelaska,
2006; Ruban, 2011; Martin-Garin et al., 2012). Reduction of these
habitats most likely resulted in local extinction of teleosauroids
across the J-K boundary of Europe. Among macropredatory marine
reptiles, as many as nine ichthyosaurian, three plesiosaurian and at
least four metriorhynchoid lineages crossed the J-K boundary, and
morphological disparity of these clades maintained the pre-
boundary levels through Early Cretaceous (Fischer et al., 2012,
2013, 2014; Benson and Druckenmiller, 2014; Young et al., 2014a;
Chiarenza et al., 2015). Our study adds teleosauroids to the list of
the reptilian lineages that crossed the Jurassic-Cretaceous
Machimosaurus rex sp. nov. is based on the articulated skeleton
of a giant crocodylomorph from the Hauterivian of Tunisia. This
taxon represents the ﬁrst indisputable Cretaceous teleosauroid, and
the ﬁrst member of this clade from Africa based on well preserved
remains. With a basicranial length approaching 160 cm (and a
partial skeleton indicating a total body length around 10 m), M. rex
is the largest known thalattosuchian. Both paleoecological data and
morphological features suggest that this species was an ambush
generalist predator with an ecology comparable to extant semi-
aquatic crocodilians. The discovery of M. rex falsiﬁes a global
mass extinction event at the J-K transition (i.e., teleosauroid
extinction), thereby highlighting the problem of sampling bias in
the reconstruction of large-scale patterns in the geological record.
The new Tunisian teleosaurid points to a conservative interpreta-
tion of faunal turnovers during the J-K transition: local extinction
events triggered by regional ecological factors and survival of
widely-distributed and eurytypic forms by means of habitat
Selected measurements of Machimosaurus rex type specimen.
Preserved basicranial length 114
Left side, from preserved anterior
end to mandibular glenoid
Right side, distance from mandibular
glenoid to anterior orbit
Width of snout anterior to orbits 25
Internal supratemporal fenestra length 33
Distance between ﬁve maxillary alveoli 22
Estimated total length of maxillary tooth row (range) 80e97
Preserved snout length 49
Postorbital skull length 65
Interorbital width 11.5
Occipital condyle width 6.2
Anterior dorsal centrum height 8.5
Anterior dorsal vertebra total height 17.6
Anterior dorsal vertebra width across diapophyses 24.3
1 29.6 35.2
2 29.5 28.8
3 34.4 28.2
4 32.6 26.1
5 33.6 29.9
6 43.4 34.7
7 38.9 29.9
8 n.d. 32.4
MD, mesiodistal diameter; LL, labiolingual diameter, in mm.
Numeration refers to position along the preserved maxilla and not to the
inferred position in the complete tooth row.
F. Fanti et al. / Cretaceous Research xxx (2015) 1e12 9
This research was supported by the National Geographic So-
ciety (grant 9586-14), Museo Geologico G. Capellini (Bologna) and
Ofﬁce National des Mines (Tunis). This manuscript beneﬁted from
discussion with A.R. Fiorillo (Perot M useum of Nature and Science,
Dallas, U.S.A.). We thank S. Hua, M. Young a nd Editor in Chief E.
Koutsoukos for detailed revisions that improved the quality of the
manuscript. The Machimosaurus rex holotype was discovered by
FM dur ing prospecting activities led by FF, an d excavated by a
team including FF, JD, LC, AC and FM. The specimen was prepared
in Tunis by FF, FM, JD, LC, TM, and MC. AC and FF conceived and
wrote the manuscript, performed the analyses and prepared the
ﬁgures. TM, LC, MC, JD and FM helped draft the manuscript and
prepa re the ﬁgures. Skeletal reconstructions of M. rex are by M.
Auditore. We thank the other members of the 2014 Italian -
eTunisian palaeontological exp edition in the Tataouine Governa-
torate, in particular, H. Aljane, M. Hassine, L. Angelicola, A.
Bacchetta, S. Cafaggi, J. Carlet and G. Mignani . This study is dedi-
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Appendix A. Supplementary data
Supplementary data related to this article can be found at http://dx.doi.org/10.
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