<oolo&alJoumal
ofthe Linnean Sock& (2000), 130: 183-212. With 6 figures
IDE bL@
doi:I 0.1006/zjls.1999.0207, available online at http://www.idealibrary.com on
+.
A new scincomorph lizard &om the Early
Cretaceous of Puebla, M6xico
VICTOR-HUGO REY"OSO*
Redpath Museum, McGill Universip, 859 Sherbmoke St. West, Montreal, Canada H3A 2x6
GEORGE CALLISON
2247 Codels Canyon Drive, G'randJunction, CO 81503, USA.
Received April 1997; acceptedfor publication May 1999
A complete skeleton of a new scincomorph lizard from the Early Cretaceous deposits of
Tepexi de Rodriguez is described. Tepexisaurus tepexii gen. et sp. nov. is the best
preserved early scincomorph and the first known taxon that is morphologically primitive to
scincoids and paramacellodid lizards. The presence of pointed ventral parietal downgrowths,
the coronoid overlapped anteriorly and posteriorly by the dentary and surangular, a small
medial flange on the retroarticular process, and weak zygosphene and zygantrum articulations
suggest scincoid relationships, but the absence of ventral and dorsal osteoscutes place
Epexisaurus as sister-group of this taxon. It shares the presence of 30 closely packed teeth
with the poorly known Upper Jurassic genus Saunllus and Pseudosaunllus, but differences in
the coronoid structure, Meckelian groove and jaw proportions indicate that both taxa are
distinct. Similar to i5pexisaum, the absence of osteoscutes in Saurillus, Pseudosaurillus and
Saurillodon place these taxa in a more primitive position relative to other paramacellodids
which should be included within Scincoidea. Thus, Paramacellodidae as previously defined
is a paraphyletic assemblage. The late presence of a pre-scincoid lizard in the Albian deposits
of Tlayua can be correlated with the presence of sphenodontians and the relictual nature of
the basal squamate Huehuecuewi rnirtcnrs. It gives additiod evidence to support the
hypothesis that Tlayua was a retkge for terrestrial archaic forms during the Albm.
Q 2000 The Linnean Society of London
ADDITIONAL KEY WORDS:-Squamata - Scincomorpha
Scincoidea - Paramacellodidae - Early Cretaceous - Albian - Mexico taxonomy - cladistics - biogeography.
~
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CONTENTS
Introduction . . . . . . . . . . . .
Abbreviations . . . . . . . . . . .
Systematic palaeontology
. . . . . .
Tepexisaurus tepexii sp. nov. . .
Description . . . . . . . . . . . .
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* Corresponding author. Present address: Departamento de Zoologia, Instituto de Biologia, UNAM,
Apdo, Postal 70- 153, Mexico 045 10 D.F. E-mail: [email protected]
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0024-408266/00/ 100183 30 $35.00/0
183
0 2000 The Linnean Society of London
184
V.-H. REYNOSO AND G. CALLISON
Skull. . . . . . . . . . . . . . .
Mandible . . . . . . . . . . . . .
Postcranial skeleton . . . . . . . . .
Appendicular skeleton . . . . . . . .
Discussion . . . . . . . . . . . . . .
Phylogenetic position . . . . . . . .
Comparison with other scincomorphs . . .
Comparison with other early lizards . . .
Stratigraphic and biogeographic significance . .
Conclusions . . . . . . . . . . . . . .
Acknowledgements . . . . . . . . . . .
References . . . . . . . . . . . . . .
Appendix. . . . . . . . . . . . . . .
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INTRODUCTION
Scincomorphsare among the earliest known fossil lizards. Most early scincomorphs
have been included within the world wide distributed Paramacellodidae (Estes,
1983). Paramacellodus is the best known paramacellodid lizard, described from
remains collected in the Early Cretaceous (Berriasian)deposits of Purbeck, England
(Hoffstetter, 1967). This lizard has also been reported from the Middle Jurassic
(Bathonian) deposits of Skye, in Scotland (Waldman & Evans, 1994); the Late
Jurassic (Kimmeridgian) deposits of the Morrison Formation in the United States
(Prothero & Estes, 1980; Evans & Chure, 1998); and from the Early Cretaceous
(Berriasian) deposits of Anoual, Morocco, and Ufia, Spain (Richter, 1994). From
the Purbeck limestone were also described the genera Becklesius, Saurillus, and
Pseudosaurillus (Hoffstetter, 1967; Estes, 1983). Becklesius was also reported from
scattered material collected in the Late Jurassic (OxfordiadKimrneridgian) deposits
of Guimarota, Portugal, where Saurillus and the Guimarota genus Saurillodon are also
representatives (Seiffert, 1973; Estes, 1983). Richter (1994) reports the presence of
Becklesius and Saurillus in Uiia, and Evans (1995) Saurillodon in the Middle Jurassic
deposits (Bathonian) of Kirtlington, Oxfordshire. The Upper Jurassic genus Shamutsaum from Karatu, Kazachstan (Hecht & Hecht, 1984) is the only complete
and fully articulated known paramacellodid; however, the coveringventral osteoscutes
does not permits detailed anatomical studies. Li ( 1985) described Mimobecklesisaurus
from remains found in the Gansu province of China, and other similar incomplete
paramacellodids were reported from the Mddle Jurassic of Tanzania (Zils et al.,
1995) and from the Middle Cretaceous of Mongolia (Alifanov, 1993).
Paramacellodidae as defined by Estes (1983) is a cordyloid-like assemblage that
resembles extant cordylids in the presence of compound ventral osteoscutes and
weakly keeled, non-compound, rectangular dorsal osteoscutes that cover the body
in overlappingseries. These osteoscutes are only known to be present in Paramacellodus,
Becklesius, Mimobecklesisaum and Sharovlsaurus. However, other early scincomorphs
referred to Paramacellodidae (Saurillus, Pseudosaurillus, and Saurillodon) share only a
similar lower jaw structure that does not differ greatly from modern cordylids
and skinks. Osteoscutes are not known for these taxa, making their identity as
paramacellodids dubious (Evans & Chure, 1998).
Ardeosaum from the Late Jurassic (Tithonian) limestones of Solnhofen, Germany
and Mgaraurus from the Early Cretaceous (Berriasian) deposits of Montsec, Las
CRETACEOUS SCINCOMORPH FROM MEXICO
185
Hoyas, Ufia, and Galve in Spain, were recently reviewed by Evans (1994) and Evans
and Barbadillo (1 997). Ardeosaums was removed from the Gekkota (Hoffstetter, 1964)
and placed in the Scincomorpha (more probably just Scleroglossa) based on the
structure of the temporal region. Mqmaums, on the other hand, is now considered
to be a lacertoid, sister-group of Teiioidea.
The Albian deposits of the Tlayua formation, Tepexi de Rodriguez, Puebla, have
yielded an interesting assemblage of superbly preserved lepidosaurs that includes an
unusual beaded sphenodontian (Reynoso, 1997), an equally unusual aquatic sphenodontian with ankylosed teeth and pachyostotic skeleton (Reynoso, 2000), and a primitive basal squamate (Reynoso, 1998a).A complete skeleton of a new scincomorph
relativelymore primitive to scincoidlizards is describedbelow. Its exquisite preservation
adds significantinformation to pre-scincoid morphology and clarifies the phylogenetic
position of early scincomorphs in relation to modern lizards.
ABBREVIATIONS
I-v
a.
a.c.
ar.
arx.
atl.
atl.ic.
aut.v.
ax.
ax.ic.
bo.
bs.
C.
ce.
cl.
co.
d.
dt.
ecX
ecp.
eP.
f.
fe.
f.f.
fi.
grsc.
h.
isc.
j.
Lce.
m.
m.c.
m.ce.
m.f
m.p.s.
metacarpaWmetatarsals
angular
astragalocalcaneum
articular
articular condyle
atlas
atlas intercentrum
autotomous vertebrae
axis
axis intercentrum
basioccipital
basisphenoid
coronoid
centrale
clavicle
coracoid
dentary
distal tarsal
ectepicondylar foramen
ectopterygoid
epipterygoid
frontal
femur
foramen facialis
fibula
granular scales
humerus
ischium
jugal
lateral centrale
maxilla
Meckelian canal
medial centrale
mandibular foramen
maxillary palatal shelf
OPP.
Pal.
p.d.pr.
pi.
p.l.pr.
Pm.
PO.
pof.
psv.
Pt .
PU.
q.
r.
ra.
ra.m.c.
r.t.
S.
sa.
sc.
sc.f.
s.f.
spl.
s9.
s.sc.
st.
ste.
ste.ri.
S.V.
ti.
U.
ul.
V.f.
Vi.C
opisthotic
parietal
palatine
parietal descending process
pisiform
parietal lateral process
premaxilla
postorbital
postfrontal
presacral vertebrae
pterygoid
pubis
quadrate
radius
radiale
retroarticular medial crest
replacement tail
stapes
surangular
scapula
scapular fenestra
surangular foramen
splenial
squamosal
suprascapula
supratemporal
sternum
sternal ribs
sacral vertebras
tibia
ulna
ulnare
vagus foramen
vidian canal
186
V.-H.REYNOSO AND G. CALLISON
SYSTEMATIC PALAEONTOLOGY
Lepidosauria Dumeril and Bibron, 1839
Squamata Oppel, 1811
Scincomorpha Camp, 1923
Tepexisaurus gen. nov.
3 p e species. I: tepexii
Epmology. From tetl, stone, and pexk, split (Nihuatl); and suuros (Gr.) lizard. Lizard
of the split stone.
Diagnosis. As for the type and only known species.
Tepexisaurus tepexii sp. nov.
(Fk. 1 A, B)
Holoppe. Instituto de Geologia, Universidad Nacional Authoma de MCxico, Cat.
No. IGM 7466 (Fig. 1 A, B). Well preserved skeleton with the head and first
vertebrae separated from the body and part of the tail missing. The skull, atlas and
axis are visible in ventral view, and the rest of the postcranial skeleton in dorsal
view.
Epmology. For Tepexi de Rodriguez, municipality where the Tlayua Quarry (the
type locality) is located.
LoCali& Tlayua Quarry, LOC.No. IGM-370 Cantera Tlayua Aranguty. No level
specified. The Tlayua Quarry is located 2 km south east of the Colonia Morelos,
near Tepexi de Rodriguez, Puebla, Mkxico.
Horizon. Middle Member of the Tlayua Formation (Pantoja-Nor, 1992). Early
Cretaceous, Middle or Late Albian (Seibertz & Buitrbn, 1987).
Diagnosis. Scincomorph lizard with 23 small maxillary teeth packed closely and the
coronoid overlapped strongly by the dentary and surangular. Differs from other
scincomorphs in the presence of 23 presacral vertebrae (shared with Ardeosuurus),
scapular emargination, epipterygoid with small ventral expansion, and cervical
intercentra ventrally flat. Shares with scincoids the presence of a small medial flange
on the retroarticular process and weak zygosphene and zygantrum articulations, but
dorsal and ventral osteoscutes are absent.
DESCRIPTION
The holotype and only known specimen of ZpexZraurus tepexii is fully articulated
and exquisitely preserved but compressed (Fig. 1 A, B). The head, atlas-axis complex
and clavicles are visible in ventral view, and the rest of the postcranial skeleton is
exposed in dorsal view. The specimen lacks the ilia which presumably remain
CRETACEOUS SCINCOMORPH FROM MEXICO
187
attached to the counterpart block that unfortunately was not collected. Some damage
is observed on the dorsal surface of the sacral region and first caudal vertebrae. As
in other Tlayua lizards, there is no significant breakage of the bones despite of the
flattening of the skeleton into a single plane. Palatal bones are deformed following
the contour of the elements beneath, and the head was compressed in a manner to
expose simultaneously the left and right lower jaw in medial and lateral view,
respectively. The left side of the palate and the braincase are well exposed providing
a great deal of information. Some details of the dermatocranium can be observed
through the empty spaces of the palate and lower temporal fenestrae. Remnants of
dermal scales and soft tissue are preserved on some vertebrae and ribs. The tail was
lost in life and a portion of replacement cartilage is preserved. The complete
ossification of all tarsals and carpals, the fusion of the astragalocalcaneum, scapula
and coracoid, and the olecranon process to the ulna suggest that the specimen is
an adult.
Skull
The skull is large and broad with a short snout that measures about one third of
the skull length (Fig. 2 A, B). Its total length, measured from the tip of the premaxilla
to the occipital condyle, is about 30% of the presacral vertebral column (Table 1).
The right mandible is laying on top of the right side of skull obscuring details of
the anterior portion of the palate.
Little, except the dentition, can be observed on the premaxilla. Only 11 teeth
are exposed, but the lower jaw appears to be covering an additional two, giving a
total count of at least 13. The teeth are conical and slightly curved with sharpened
tips. Whether or not the premaxillary bones are fused is not known.
The right maxillae is preserved in ventral view and the left in medial view. In
ventral aspect, a wide shelf extends medially from the base of the tooth series. The
maxilla retains approximately the same width throughout most of its length except
posteriorly where it tapers. The tooth series terminates posteriorly slightly beyond
the anterior end of the orbit, but the maxilla continues posteriorly as a posterolaterally directed process to about the mid point of the orbit. The facet for the
palatine takes a form of a cup-shaped depression on the margin of the last third of
the maxilla. The contact is relatively slender and comparable to that of lacertids
and anguids. A longitudinally oriented facet for the reception of the anterior process
of the ectopterygoid is present a short distance posterior to the articulation with the
palatine, suggestingthat the maxilla was almost excluded from the suborbital fenestra.
The pleurodont teeth are covered extensively by the labial margin of the maxilla.
They are cylindrical, unicuspate, and although somewhat recurved anteriorly, they
become straight caudally. Their shape is similar to those of Becklesius (Richter, 1994).
The tips of the teeth also tend to change shape from nearly conical anteriorly to
more laterally compressed posteriorly. The posterior teeth of the right maxilla appear
to have blunt tips. Comparison with the sharply pointed teeth on the posterior left
maxilla shows this condition was caused by compression. Twenty-nine tooth positions
can be counted on both sides. The mode of replacement is obscure. Small posterolingual pits typical of scincomorphs are not obvious but they might be not
preserved. The lack of enlarged replacement pits at the base of the teeth suggest
that the iguanian-type replacement (Edmund, 1960) was not present. In the right
188
V.-H. REYNOSO AND C. CALLISON
Figure 1. A, photograph and B, illustration of the skeleton of Tepexisaurus tepexii gen. et sp. nov.
(IGM 7466) as preserved on the block.
CRETACEOUS SCINCOMORPH FROM MkXICO
B
I
2 cm
I
I89
I90
V.-H. REYN'OSO AND G . CALLISON
Figure 2. A, photograph and B, illustration of the skull of Tepexisaum tepexii gen. et sp. nov.
(IGM 7466) as preserved on the block.
CRETACEOUS SCINCOMORPH FROM MEXICO
191
maxilla a small replacing tooth appears adjacent and slightly posterior to tooth
number five. Similar teeth are present on positions 11, 17, 20, and 25 of the left
side, but the older teeth were already shed.
Only small areas of the frontal are visible on this specimen. A short length of the
left lateral margin shows the location of part of the left orbit. The strong ventral
cristae cranii can be traced alongside this margin under the deformed overlying
palatal bones. Both ridges begin medial to the posterolateral corners of the frontal
and converge anteriorly. The contact between the paired descending processes of
the frontal is uncertain, since the deformed area of the left pterygoid appears to
outline the wall of the aerial groove. Whether the frontals were paired or fused
V.-H. REYNOSO AND G. CALLISON
192
TABLE
1. Measurements of the holotype of Tepexisaurus tepexii gen. et sp. nov. (in mm)
Total specimen length ....................................................................................................................
Skull length (tip of the premaxilla to occipital condyle) ....................................................................................
A-P diameter of orbit .......................................................................................................................................
Quadrate height ................................................................................................................................................
Mandible length
...........................................................
..............
Mandible height at dorsal tip of coronoid .............................
Dorsal tip of coronoid to centre of articulation facet .........................................................
Mentis to dorsal tip of coronoid .....................................................................................................................
Presacral vertebral column length (PSVC) .......................................
.................................................................
Skull length plus PSVC =Presacral length (PSL)..........................................................................................
Skull length/PSL x loo= 29%
c. 186
23.3
4.7
5.2
12.2
58.4
8 1.7
:
Forelimb
Total length from proximal humerus to tip of longest digit .....................
............................................
Humerus length ( =H) ............................................................................
H PSL x loo= 14%
H/F x 100=80%
Ulna le
..........................
......................................................
Radius
.......................................................................................................
R/H x 100=73%
Digit
Metacarpal length
Phalanx length
1
I
I1
I11
N
V
Metacarpal III/H x
2.2
3.2
3.8
3.6
2.4
100 = 33%
2.4
1.9
2.0
1.9
2. I
2
1.6
2.4
2.0
1.8
2.5
3
4
5
1.4
2.5
1.7
1.4
I .5
2.5
I .2
Hind limb:
Total length from proximal femur to tip of longest digit ...... ...............................................................
Femur length (=F) ........... ..........................................................................................................
F/PSL x 100=17%
Tibia length (=T) .......................................................................................................................................
T/F ~ 1 0 0 = 7 5 %
H + R / F + T x 100=79%
Fibula length .................................................................................................
Digit
Metacarpal length
Phalanx length
I
I
I1
111
3.5
4.8
5.8
3.0
2.3
2.3
2.9
2.5
IV
6.0
V
2.0
Metatarsal N / F x 100=42%
Metatarsal V/Metatarsal IV x 100 = 33%
2
1.3
2.7
2.1
2.1
2.6
3
4
5
1.1
2.7
2.2
2.7
1 .o
2.2
1.6
1.1
11.4
c.42.4
14.2
10.7
.
9.9
cannot be determined. A straight, transversely oriented fronto-parietal suture can
be observed on either side of the right pterygoid.
Projecting ventrally from the parietal are a pair of narrow, elongated crest-like
processes that partially wall the lateral part of the braincase. Swollen ends very
similar to those of the cordylids (e.g. Cordylus campbelli) articulate with the epipterygoids
as in most scincomorphs,although in the holotype the epipterygoidsare disarticulated.
The presence of a parietal foramen and the paired or fused condition of the parietals
cannot be confirmed because the right pterygoid and sphenoid obscure this region.
Neither parietal tabs underlying the frontals nor a fossa for the reception of these
tabs on the ventral surface of the frontal are present, as they are in gymnophthalmids.
CRETACEOUS SCINCOMORPH FROM MkXICO
I93
The medial position of parietal downgrowths and the structure of the postorbital
bones (see below) suggest that the adductor musculature was attached to the ventral
surface of the skull roo[ The tip of a long and slender supratemporal process of the
parietal is exposed posterior to the suspensorium.
The prefrontals are covered by the left and right palatines and the dentary, but
deformation of the palatal elements as they were crushed down onto the skull table
provides a rough outline of these bones. In most lizards the prefrontals are thick
bones with medially expanded projections that form the anterior wall of the orbit.
The posterior ends of the masses beneath the deformed palatine delimit the anterior
boundaries of the orbits but no other details can be discerned.
Both sturdy jugals are present. The right jugal is exposed in ventral aspect and
the left in medial. In ventral view, the jugal is straight along the postorbital region.
It tapers dorsally, lapping under the ventrolateral edge of the postorbital. A small
foramen pierces the posteroventral margin close to the most posterior contact with
the maxilla. The maxillary process of the jugal extends under the orbit, but the
contact with the prefrontal is unknown. In medial view, the jugal is slightly curved
and somehow constricted behind the orbital rim. Near the ventral-most end is the
facet for the ectopterygoid. The jugal does not contact the postfrontal, but abuts
very close to it and does not approach the squamosal.
The postfrontal and postorbital are better seen on the left side of the temporal
region. Both bones remain in articulation and are not fused together. They extend
caudally and border the lateral edge of the parietal. The upper temporal fenestra
is closed at least to the level of the anterior tip of the squamosal, but whether it is
closed throughout the remainder of its length is unknown.
The postorbital is flat and mainly horizontal, forming part of the skull roof. A
jugal process is very small or absent. The postfrontal is a broad element, of about
the same width as the postorbital. In spite of its total width in ventral aspect, the
bone might have had very limited exposure in dorsal view, as in cordylids.
The suspensorium is supported by the squamosal, the supratemporal and the
paraoccipital process. Only the anterior and posterior tips of both squamosals are
exposed. The posterior ends are sharply curved suggesting the presence of the typical
scleroglossanJ-shaped squamosal, although the presence or absence of the squamosal
dorsal process is uncertain. The supratemporal lies deep between the posterior end
of the squamosal, parietal, and paraoccipital process.
Most of the vomerine region of the palate is obscured by the right dentary and
the vomerine process of an anterolaterally displaced right palatine. Only a very
small portion of the lateral concave emargination that borders the internal naris of
the right vomer is exposed. Laterally, the internal naris parallels the straight medial
margin of the maxilla, and medially is concave, following the lateral expansion of
the vomer. The posterior boundary of the internal naris is located slightly posterior
to the palatine/maxilla contact.
The outline of the palatine is trapezoidal. Anteriorly, the vomerine process of the
palatine projects more anteriorly than the maxillary process and the area between
these processes is vaulted dorsally to form the posterior and lateral walls of the naris.
The maxillary process is preserved with the articulation facet facing ventrally. The
vomerine process of the palatine seems to end freely without a superficial ventral
contact with the vomers. This is suggested by the way the vomerine process of the
left palatine is preserved, overriding the body of the right palatine and dentary, and
by the way the right palatine has become similarly displaced over the vomers. The
194
V.-H. REYNOSO AND G . CALLISON
flange formed anteriorly by the vomerine process might have provided a secondary
passage for the choana, extending the narial passageway further back into the
mouth. The articulation with the pterygoid is extensive, almost transversally oriented,
and interdigitated. Interdigitations are small and rounded, probably forming a
kinetic hinge (Frazzetta, 1962). Depending on how much the skull was flattened
postmortem, the palatines may be restored as just touching or separated at the
midline. The lack of a facet on their medial margin suggest that the palatines were
most probably separated.
The ectopterygoid is triradiate. The lateral process is elongated and fits into a
medial articulating facet of the jugal. The anterior process extends forward, barely
reaching the maxilla/palatine contact, almost excluding the maxilla from the
suborbital fenestra. The entire anterolateral surface forms a flange that fits into a
groove on the maxillary posteromedial edge. The pterygoidal process is broad and
crushed flat as is the rest of the skull. An originally more vertical position is suggested
by the decoupling of the ectopterygoid from the articulation facet of the pterygoid.
The pterygoid lacks teeth. The palatine process is broad, with its medial part
projected more anteriorly. The lack of medial facets on either anterior tip suggests that
the pterygoids were separated by a broad interpterygoidal vacuity. The ectopterygoid
process bears an enlarged and ventrally oriented transverse flange that runs from
the ectopterygoid contact to the central body of the pterygoid, broadening medially.
The central body is broad and somewhat short anteroposteriorly. It lacks the medial
process for the basipterygoid. The basipterygoid facet, is located posterior to the
point where the quadrate process diverges from the central plate. The quadrate
process of the pterygoid is long and slender in ventral view, At its posterior end,
the process curves laterally and tapers distally to form a lateral facet where the
quadrate abuts. The quadrate process maintains a primitive condition and is
broadened distinctively dorsoventrally as in most iguanians.
The long, slender epipterygoids are displaced: the right on top of the braincase,
and the left covered partially by the quadrate. The ventral end is swollen to almost
twice the diameter of the shaft and rounded at its articulation with the pterygoid.
The dorsal end has approximately the same diameter as the shaft. Both epipterygoids
are bowed equally with the convexity facing posteriorly, suggesting that this is their
natural shape.
The left quadrate is preserved in posterior aspect, and the right is crushed and
twisted to expose the cephalic condyle. In posterior view, the quadrate is D-shaped
and imperforate. The tympanic crest is broad throughout its length. A thick crest
boarding the lateral edge of the quadrate emargination is apparently formed by the
compressed lateral margins of the quadrate lateral conch suggesting that the 'lateral
conch was not only wide but also distinctively deep. On the medial side of the
quadrate there is a small crest that extends from the cephalic condyle to the
mandibular condyle. The ventral portion of the medial crest seems not to be modified
as a lappet for the pterygoid, but this condition is uncertain since this part is obscured
by the overlying quadrate process of the pterygoid. The conspicuous posterior
curvature of the posterior quadrate crest suggests a strongly bowed quadrate in
lateral view. The cephalic condyles are smooth surfaces separated by a medial
groove. They probably contacted the posterior end of the temporal arch and the
paraoccipital process, permitting a great amount of streptostyly. The mandibular
articulations are also smooth and separated by a groove. The groove suggest the
presence of a ridge on the mandibular counterpart. A broken medial portion of a
'
CRETACEOUS SCINCOMORPH FROM MhXlCO
.
195
slender stapes, similar to the stapes of other squamates, lies on top of the quadrate
lateral conch.
Although the braincase region is heavily compressed and distorted, several
important features can be discerned. The suture between the basisphenoid and the
basioccipital is faint, but clearly interdigitated. Anteriorly, the basipterygoid processes
are elongated, but do not seem to be very broad in the condylar region. The
parasphenoid process is either not preserved or is bent backwards and obscured by
the left parietal downgrowth. The basisphenoid is transversely narrow on its central
portion. Wide lateral wings represent a recessus jugularis and not an expanded
crista lateralis. Two small parallel ridges delimit the lateral edges of the medial
region of the basipterygoid. This portion has been flattened exposing the lateral
margins. On the left side, the crista prootica (also outturned because of compression)
marks the most lateral margin of the braincase. A small depression on the anterior
region indicates the position of the posterior opening of the vidian canal, but the
perforation itself is not evident. More posteriorly, on the paraoccipital process and
close to the midline is a small foramen facialis. The position of the suture between
the prootic and basisphenoid is uncertain, so it cannot be said which bone is pierced
by the jugular vein, although it is clearly enclosed by the crista prootica. If the
suture in Figure 2B is correctly identified, then the vidian canal traverses the suture
between both bones as in some skinks and cordylids. The distorted basioccipital
shows a well developed sphenooccipital tubercle. The occipital condyle is mostly
obscured by the atlantal hypocentrum.
Under the lateral margins of the crista prootica and parallel to the sphenooccipital
tubercles are two heavily compressed lateral processes that resemble the alar process
of the prootic in lacertids. At the posterior part of the skull, a fused opisthoticexoccipital is turned anteriorly leaving only the posterior face exposed. As in other
squamates, they are oriented slightly backwards, and the broad distal ends contact
mainly the quadrate. A pair of vagal foramina are exposed on the dorsal surface
close to the occipital condyle.
Mandible
The structure of the lower jaw is similar to that of scincoids and xantusiids. The
robust dentary is distinctly wider in the region around the postdentary articulation
(Fig. 2A, B). The anterior end of the dentary is less robust and tapers close to the
end. Five or six foramina pierce the anterior half of the bone. The posterior end is
notched to receive a similarly robust surangular. A lateral process extends dorsally,
overlaying laterally the coronoid, almost covering it up to the apex. The posterior
process of the dentary extends dorsally almost to the level of the tip of the coronoid.
Ventrally, the dentary extends posteriorly to fit into an anterior notch of the angular.
A centered and fully open Meckelian canal occupies the medial surface of the
lower jaw from the mental symphysis to the posterior end of the splenial. Thirty
closely spaced mandibular teeth are present, a similar number to that of the maxilla.
Tooth numbers 2-3, 5, 8, 13, 18, 24, and 26 are missing. The teeth are long and
peg-like with recurved tips, and sit on a broad subdental shelf. About two-thirds of
the tooth length is overlapped laterally by the dentary labial margin leaving exposed
only a relatively short tooth portion. As in the maxilla, the mode of tooth replacement
is not clear, and no lingual or posterolingual replacement pits are evident.
I96
V.-H. REYNOSO AND G . CALLISON
The surangular covers most of the lateral surface of the postdentary region,
restricting the angular to the ventral border of the mandible. It overlaps tightly the
posterior margin of the coronoid to restrict the lateral exposure of the coronoid to
a small antero-ventrally directed ridge as in cordylids and xantusiids. The posterior
end of the surangular does not reach the articular condyle. An enlarged anterior
surangular foramen pierces the lateral surface of the surangular, forming a deep
groove that extends anteriorly to the ventral end of the coronoid. O n the posterior
half of the surangular, a posterior surangular foramen and an additional unnamed
foramen are aligned posteriorly, at the same level of the surangular foramen.
Although the angular is almost completely fused to the articular and surangular,
a faint suture permits delineation of their limits. The angular is exposed primarily
on the medial side of the jaw. Anteriorly it forks, bearing a ventral notch for the
reception of the dentary and a dorsal notch for the reception of the splenial.
Posteriorly it is reduced, and extends only as far as the middle portion of the
postdentary region.
The splenial is a small triangular bone. It extends anteriorly to the level of the
last third of the tooth bearing portion of the dentary, and posteriorly to the level of
the coronoid process. The Meckelian canal passes through the entire ventral margin.
The anterior process of the fused prearticular-articular prevents contact of the
splenial with the surangular below the coronoid.
The articular condyle is formed only by the articular. Posterior to the articular
surface a rather short retroarticular process is present. On the right mandible the
process was overturned and flattened to the level of the lateral surface of the dentary.
Nevertheless, the process shows a slight twist and a medial inflection of the process
is presumed. On the left mandible, the process does not appear to be as wide. This
condition, however, might be an artifact of compression. As in most scincoids, a
medial flange is present on the retroarticular process.
Postcranial shhton
The majority of the postcranial skeleton is exposed in dorsal aspect (Fig. lA, B).
It was separated by a very short distance from the cranium prior to fossilization.
The preservation is particularly remarkable not only for its completeness but also
for showing remnants of soft tissue in a regenerated tail and what appear to be
patches of granular integumentary scales (Fig. 3).
A complete presacral column of 23 vertebrae and 2 sacral vertebrae are preserved,
but only 6 proximal caudals remain. The last vertebra was autotomized and a small
section of a regenerated tail remains attached to its end. Another small portion of
regenerated tail was displaced transversally beneath more anterior vertebrae. The
atlas-axis remains attached to the skull. Both neural arches are crushed to the right
side, but they preserve some details. The atlas is about one third the length of the
axis. Their respective intercentra and the axis centra are exposed in ventral aspect.
Ventrally, the atlantal centrum contacts extensively the second intercentrum leaving
only a very reduced contact with the first intercentrum. The axis appears to be
procoelous, but this condition is uncertain. If so, then the posterior cotyle is not
very pronounced. The neural arch is enlarged and bears a broad neural spine that
is somewhat extended posteriorly. The anterior part of the third vertebral neural
arch remains articulated to the axis.
CRETACEOUS SCINCOMORPH FROM MEXICO
197
Figure 3. Detail of the granular scale remains preserved on top of the vertebral column in the holotype
of Tspexisaurus tepexii gen. et sp. nov. (IGM 7466). Scale bar =2 mm.
The arrangement of the cervical intercentra resembles the primitive lacertilian
type (type 1 intercentra of Hoffstetter & Gasc, 1969) in which the atlas intercentrum
contacts the ventral margin of the occipital condyle, and the axis intercentrum is
placed in an intervertebral position, contacting the atlas intercentrum anteriorly and
the axis centrum posteriorly. Both intercentra lack ventral keels as in primitive
lepidosaurs.
It is difficult to determinate the number of cervical vertebrae based on the number
of rib attached to the sternum. Small flattened ribs are present from the third to
fifth cervicals. All more posterior ribs are enlarged to about the same length. The
ribs of the seventh vertebrae (and probably the sixth as well) have rounded ends
suggesting that they were free ribs. A small portion of a sternal rib shows between
the eighth and nine right ribs. It seems to contact the anteriormost sternal rib
emargination, immediately posterior to the coracoid articulation. The distal end,
however, is obscured by the eighth and ninth ribs, and it is not clear with which of
these two ribs it was associated. In either case, Zpexisaurus could not have less than
seven cervical vertebrae. It is interesting to note that ribs nine to twelve are oriented
in the same way, suggesting that only these ribs were attached to the sternum. Thus,
the formula for the cervical vertebrae would be two ribless vertebrae three vertebrae
bearing short distally widened ribs two (or three) long slender vertebrae (Hoffstetter
& Gasc, 1969).
Trunk vertebrae are short anteroposteriorly. The neural spines are short and the
zygapophyses well developed. On some vertebrae, traces of weak zygosphene/
zygantra articulations can be discerned, but in most vertebrae compression of the
neural arches obscures this region. In the last presacral vertebra the post-zygapophyses
are distinctly closer to one other compared to anterior vertebrae. All trunk vertebrae
+
+
198
V.-H. REYNOSO AND G . CALLISON
bear ribs except the last one. Trunk ribs remain of the same size from the first
sternal rib (either eighth or ninth) to rib number 16, after which they decrease in
size. The posteriormost presacral ribs are strongly angulated.
The area around the anteroposterior axis of the two sacrals and first three caudals
is heavily crushed. The shape and length of the impression on top of these vertebrae
suggest that an unpreserved ilium covered them. Each sacral and caudal vertebra
bears a single rib fused to the centrum. In the caudal vertebrae they are oriented
slightly posteriorly. Only five caudal vertebrae remain complete since the sixth was
autotomized and has a replacement tail attached posteriorly. The first autotomous
vertebra is the fifth.Although the septum is clearly preserved, the slight displacement
of the transverse processes prevents the establishment of the position of the autotomous septa relative to the processes. The lack of transverse processes in the
anterior portion of the autotomized vertebra suggests that it was split anterior to
the transverse processes (vertebrae type 3 of Etheridge, 1967). This type of vertebra
occurs in the Middle Jurassic-Early Cretaceous genus Paramacellodm (Hoffstetter,
1967).
Appendiculur shleton
Both clavicles are preserved in ventral view and displaced on either side of the
atlas-axis complex (Fig. 2A, B). They are S-shaped, but strongly angulated. On the
proximal end, a modest expansion lies anteriorly. Partial division with the main
body of the clavicle suggests the presence of a clavicular fenestra.
The sternum is visible faintly below the eighth to tenth right ribs (Fig. 4).As
exposed, it has three lateral extensions for the sternal ribs, indicating that at least
three ribs were attached (possibly ribs nine to 1 1). There are no signs of fenestration,
but this region is covered by the dorsal vertebrae. A small portion of a thin
interclavicle is observed to the right of the seventh vertebra. No other details of this
bone can be discerned. Fragments of secondary ribs at the ends of some trunk
vertebrae are mostly likely from postxiphisternal inscriptional ribs.
The scapula and coracoid are covered partially by remnants of soft tissue, probably
the cartilaginous suprascapula. Both bones are preserved in articulation, but a faint
suture indicates that they are not co-ossified. The scapulocoracoid, anterior coracoid,
and a small scapular fenestra are present. The scapular dorsal process is expanded
posteriorly, and the postero-ventral process of the coracoid terminates abruptly in
a squared, angular extension similarly to cordylids and paramacellodids (Hoffstetter,
1964; Prothero & Estes, 1980). Traces of the epicoracoid cartilage are preserved
anterior to the coracoid.
The front limbs are typically squamate with co-ossified epiphyses. Measurements
and proportions are given in Table 1. The right humerus was compressed, exposing
both ventral and medial faces at the same plane. As in the other long bones of the
holotype, the shaft has been broadened because of compression. An ectepicondylar
foramen is present.
The radius and ulna are subequal in length. The ulna has a co-ossified olecranon,
a deep sigmoid notch, and an almost hemispherical distal end. The manus is
preserved in detail. The dorsal aspect is shown on the right manus and the ventral
on the left. The carpal elements identified are the radiale, ulnare, intermedium,
medial centrale, lateral centrale, pisiform, and distal carpals two to five (interpretation
CRETACEOUS SCINCOMORPH FROM MEXICO
I99
cl.
Figure 4. Detail of the right shoulder girdle and forelimb of T'exisaurus
t e p e d gen. et sp. nov.
( E M 7466) as preserved.
of medial carpal elements from Carroll, 1977). The broadening of the proximal end
of the first metacarpal suggests that the first distal carpal was fused to the epiphysis.
In general, the structure and arrangement of the carpal bones are consistent with
extant lizards. The intermedium is about the size of the lateral centrale and does
not contact the ulna. The medial centrale is similar in size to the intermedium and
lateral centrale and is excluded from the medial border of the manus. The pisifom
200
V.-H. REYNOSO AND G . CALLISON
sits high (mostly above the ulnare) as in the xantusiids Lepidophyma and Xantusia and
in the skink Mumsc& (Renous-Ucuru, 1973).
The manus of Zpexzjuurus retains the plesiomorphic lepidosaurian phalangeal
formula 2-3-4-5-3. A short, curved, and dorsoventrally expanded, but distally pointed
ungual terminates each digit. The ungual of the first digit is considerably larger
than the other ones.
Neither ilium is well preserved. Parts of them were lost on an uncollected
counterpart block, or were overprepared. As pointed out above, a long imprint
about the size expected of the left ilium deforms the dorsal surface on the sacral
and first caudal vertebrae. Other than the length, no other feature of the ilium is
evident. The anterior margin of the right ischium is preserved. Its unusually broad
contact with the pubis, shown by a well defined puboischial suture, reduces the size
of the pelvic thyroid fenestra. The posterior edge of the left ischium is exposed
lateral to the first caudal vertebra, but no details are preserved. The robust pubis
is quite wide proximal to the acetabulum and is penetrated by a moderately large
obturator foramen. The short ventral extension of the pubis resembles the primitive
squamate condition (Estes et ul., 1988: Fig. 8d).
The hind limbs are preserved in dorsal aspect (Fig. 5). The tibia is subequal in
length to the fibula Fable I) and bears a distal notch for the articulation of the
astragalus as seen on the left limb. The right and left tarsi are fully ossified. The
astragalus and calcaneum are fused, but a faint suture is s t i l l visible. The astragalus
is considerably larger, bearing wide articulations for both the tibia and fibula. Only
a very small part of the medial end of the fibula contacts the calcaneum. A perforation
in the right astragalus appears to be an artifact and was probably made during
preparatio;. An enlarged fourth distal tarsal has approximately equal areas of
articular surface for the astragalocalcaneum and the fifth metatarsal. On the right
pes the fourth distal tarsal was overturned and shows the complex tongue-in-groove
articulation with the astragalocalcaneum (Brinkman, 1980). The third distal tarsal
is much smaller than the fourth. No other tarsal bones can be identified. The fifth
metatarsal is hooked. Both are preserved with only their dorsal sides exposed and
the location of the plantar tubera is unknown. The phalangeal formula of the pes
is the primitive count (2-3-4-5-4). As in the manus, each digit is terminated by a
short claw-supporting phalanx.
DISCUSSION
PLylogenetic position
The sister-group relationships of Zpexisaurus were established using PAUP 3.1.1
(Swofford, 1993) and the modified version of the data matrix of Estes et al. (1988)
presented in Reynoso (1998a). All informative characters presented by Evans and
Chure (1998) and data for the genus Puramacellodus were included. The analysis
was performed through an heuristic search using the random-additional-sequence
algorithm with 100 repetitions. The procedures were the same as those discussed
in Reynoso (1998a). All characters were unordered, multistate characters treated as
polymorphism, and uninformative characters 157 and 158 were ignored. With the
exclusion of Huehuecuet@aUi, character state ‘small rounded postorbital’ is autapomorphic for iguanids, thus character 15 became uninformative and was also ignored.
CRETACEOUS SCINCOMORPH FROM MkXICO
20 I
Figure 5. Detail of the left hind limb of Tepexisaurus tepemY gem et sp. nov. (IGM 7466) as
preserved.
The outgroup was composed by younginiforms, Saurostemon, Kuehneosauridae and
Rhynchocephalia.
Four equally parsimonious trees (tree length = 848, CI = 0.782, RI =0.653; see
Appendix) were obtained at replicate number two, giving a good margin of security
that all of the most parsimonious trees were found in the search. The strict consensus
suggests that Ttpexisaurus is the sister-group of scincoids and that Paramacellodur is
V.-H. REYNOSO AND G. CALLISON
202
member of the Scincoidea (Fig. 6). Curiously the tree topology does not agree in
many aspects with previously presented hypothesis (Estes et ul., 1998; Evans &
Chure, 1998; Reynoso 1998a). Anguimorpha, Scincomorpha, and Gekkotans are
grouped together forming Sukhanov’s (1976) clade Scincogekkonomorpha (Fig. 6:
Node 1; see also Russell, 1988). Uncertain position of snakes, and the clade
amphisbaenians dibamids still remain. Snakes can appear either as sister-group of
Anguimorpha Gekkota Scincomorpha, or as sister-group of amphisbaenians
dibamids. Agamst results presented in Reynoso (1998a), derived from basically the
same data matrix, the Autarchoglossa is not supported, denoting the weakness of
the clade. The radical change in position of the major groups of the Squamata
shows how far their sister-group relationships are to be understand.
Whatever the position of the taxa in the cladogram, the character distribution in
the lineage leading to Zpexisuurus is not affected significantly. In each of the four
hypotheses, the inclusion of Zpexiwurus in Squamata is supported by: straight
frontoparietal suture, ventral peg of the squamosal for the articulation of the
quadrate, absence of the ventromedial quadrate lappet of the pterygoid, vomer and
pterygoid separated by palatine, absence of palatine and pterygoid teeth, broad
interpterygoidal vacuity, paraoccipital process contacting suspensorium, pin-like
stapes, vidian canal enclosed by bone, small contact between symphyses of dentaries,
short angular, procoelous vertebrae, all cervical ribs single headed, large thyroid
fenestra, absence of the gastralia, and fifth metatarsal hooked. The condition of the
plantar tuber of the fifth metacarpal is unknown, and the presence of keeled cervical
intercentra is an unambiguous synapomorphy of squamates that is reversed in
Zpexisuurus. In the hypothesis in which snakes are sister-group of
amphisbaenians dibamids, the reduction of the palatine posterior process allowing
the pterygoid to enter the suborbital fenestra, is an ambiguous synapomorphy that
supports the inclusion of Z-exisuurusin the Squamata.
The inclusion of Zpexisuuw in Scleroglossa is supported by two unambiguous
synapomorphies:vomer extended posterior to the middle of the maxillary tooth row
and a prominent palatine choanal fossa. The presence of 26 or more presacral
vertebrae is diagnostic to scleroglossans. The reduction of the presacral count to 23
vertebrae is a unique (probably reversed) condition of Xpexisuum among scleroglossans, convergent with some agamids, chamaeleontids, and iguanids. The cervical
intercentrum sutured or fused to the preceding centrum diagnose scleroglossans if
snakes are sister-group of Anguimorpha Scleroglossa. In Zpexisauw, this character
is reversed to the primitive condition: cervical intercentrum intervertebral.
A postorbital contributing less than one half to posterior border of the orbit
supports the inclusion of Zpexisuurus in Node 1 (Fig. 6). The coracoid emarginated
will support unambiguously this hypothesis only if snakes are sister-group of
amphisbaenians dibamids. The possible presence of a forked postfrontal, coded as
unknown in the analysis because the bone is obscured by the pterygoid, would give
additional evidence that Zpexisuurus belongs to this node.
The anterior border of the orbit formed by the maxilla and the jugal, and pointed
ventral parietal downgrowths are the only synapomorphies present in Xpexisauw
that support its inclusion in the clade Scincomorpha+Gekkota (Node 2 in Fig. 6)
and in the Scincomorpha respectively. Other characters are not known in Zpexlsuurus.
A very large symphysial process of pubis is another synapomorphy that supports
the Scincomorpha, however, this character keeps its primitive condition in ZpexzSuums
and is interpreted as a reversal.
+
+
+
+
+
+
+
CRETACEOUS SCINCOMORPH FROM MEXICO
203
a
3
0
fY
0
50
-
SClNCoMORPHA
ANGUIMORPHA
Node 2
I
Node 1
I
scLERoGLossA
I
SQUAMATA
Figure 6. Strict consensus of four equally parsimonious trees showing the sister-group relationships of
Tepexisaums tepexii, Paramacellodus and scincoids. The tree is the result of 100 replicas of a random
additional sequence heuristic search using PAUP (Swofford, 1993). The data matrix used is that of
Estes et al. ( 1988) as modified in Reynoso (1998: appendices 1 and 2), and adding informative characters
of Evans and Chure (1 998). Characters for Tepexisaunrc and Paramacellodus are presented in the Appendiu.
Tree description: Tree length =848; consistency index =0.782; retention index= 0.653, rescaled
consistency index =0.5 10. Apomorphy list (only unambiguous characters present in all trees): Squamata:
prernaxillae fused, parietals fused, straight frontoparietal suture broader than nasofrontal suture, short
parietal table with occipital region exposed dorsally, squamosal with ventral peg for quadrate, quadrate
lappet of pterygoid absent, opisthotic and exoccipital fused, palatine teeth absent, pterygoid teeth
absent, broad interpterygoidal vacuity, pterygoid and vomer separated, paraoccipital process contact
suspensorium, little or no contact between symphyses on dentaries, angular ends anterior to articular
condyle, vidian canal fully enclosed by bone, subdivided metotic fissure, pin-like stapes, stapedial artery
posterior to stapes, procoelous vertebrae, keeled cervical intercentra, cervical ribs single headed, large
thyroid fenestra in pelvic girdle, hooked fifth metatarsal with proximal head and tuber modified,
gastralia absent. Scltmglossa: descending process of frontal contacts palatine, vomer extends posterior
to midpoint of maxillary tooth row, septomaxillae meet in midline, convex expanded septomaxilla,
prominent choanal fossa of the palatine, dorsal surface of retroarticular process without sulcus or pit,
posterior border of retroarticular process obliquely twisted, 26 or more presacral vertebrae, epiphyses
fused prior to cranial fusion, muscle rectus abdominis lateralis present, posterior portion of tongue
keratinized, mid-dorsal scale row absent. Node I: postfrontal forked medially, postorbital contributes
less than one half to posterior border of orbit, anterior head of the muscle pseudotemporalis profundus
present. Node 2: anterior border of orbit formed by maxilla and jugal, 2nd ceratobranchial present,
tongue plicate. Scincomorpha: parietal tabs present, pointed parietal downgrowths, very large symphysial
process on pubis, dermal rugosities vermiculated, all tongue keratinazed. Node 3 weak zygosphene and
zygantrum intervertebral articulations. Scincoidea: ventral osteoscutes, dorsal osteoscutes. Full tree
description is given in the Appendix.
204
V.-H. REYNOSO AND G . CALLISON
The sister-group relationships of Zpexisaurus with scincoids is supported by the
presence of a posteromedial flange in the retroarticular process, and weak zygosphene
and zygantrum accessory articulations. The presence of a posteromedial flange in
the retroarticular process supports this clade unambiguously only if Paramacellodus is
sister-group of Scincidae (Appendix: tree number 1). The presence of dorsal and
ventral osteoscutes supports the inclusion of Paramacellodus within the Scincoidea
forming an unresolved trichotomy with Scincidae and Cordylidae. According to this
hypothesis, Scincoidea only can be defined if Paramacellodidae is included.
Although the four most parsimonious hypotheses agree in the position of TepexZraurus
as the sister-group of scincoids (paramacellodids included), all branch leading to this
clade does not appear to be stable. The clade 5pexisaurus+Scincoidea collapses
forming a polytomy into the node Scincomorpha after 100 bootstrap replicas using
the random additional sequence algorithm of PAUP (Swofford, 1993; see Appendix).
The branch support values (Bremer 1994) were calculated using the converse
constraint option of PAUP, and it was found that only one additional step is required
to collapse Scincidae, Cordylidae, Paramacellodus, Zpexisaurus and Lacertoidea. The
branch instability is caused mainly by the amount of unknown information for
Zpexisaurus and Paramacellodus in the data matrix, as well as the frequency of
convergence in all lineages. In light of the relative instability of the branch supporting
its sister relationships with scincoids, Zpexisaurus is referred only to the Scincomorpha.
Cornpanson with other scincomorphs
Unfortunately no paramacellodid lizard, other than Paramacellodus, are known well
enough to be analyzed in a broader phylogenetic analysis. The several genera
referred to Paramacellodidae are known from scattered material from Werent
localities in Europe, Asia and North America. Their descriptions are based mainly
on lower jaws. In these taxa the coronoid bone is restricted anteriorly and posteriorly
by the dentary and surangular, exposing only a small lateral ridge. This condition
is known for Paramacellodus, Becklesius, and Pseudosaurillus, is not very clear in Saurillus
and Saurillodon although it might be present (Estes, 1983), and it is unknown in
Mimobecklesisaurus and Sharovisaurus. The presence of thisjaw structure is uninformative
among taxa related to the Scincoidea, since it is very similar in cordylids, skinks,
paramacellodids, and Zpexisaurus. A medial flange on the retroarticular process, the
only character informative at a lower level, is unknown in most taxa assigned to the
paramacellodids because the retroarticular process is usually broken.
On the basis of similar rectangular osteoscutes Estes (1983) has suggested a close
relationship of Paramacellodus, Becklesius, Saurillus, Pseudosaurillus, and Saurillodon, with
cordylids (grouped as cordyloids). The presence of compound osteoscutes is a major
synapomorphy supporting the monophyly of Scincoidea (including Paramacellodidae). As suggested by Evans and Chure (1998), the presence of osteoscutes
in Paramacellodus, Becklesius, SharovzSaurus, and Mimobecklesisaurus,supportstheir inclusion
within Paramacellodidae. However, those taxa without osteoscutes assigned to
Paramacellodidae (e.g. Saurillus, Pseudosaurillus and Saurillodon ) have no shared derived
characters that could assert their position as true scincoids. The lack of ventral and
dorsal osteoscutes place Zpexisaurus as sister-groupof scincoids.The lack of osteoscutes
in Saurillus, Pseudosaurillus, and Saurillodon also may indicate a basal position to
scincoids similar to that of Tepexisaurus. This indicates that the Paramacellodidae as
CRETACEOUS SCINCOMORPH FROM MEXICO
205
TABLE
2. Comparison between Ardeosaumr, EichFtmttisaumr, and libemiaunrs based on characters listed
by Evans ( 1993). (-) =condition unknown
Skull sculpture
Head scale pattern
Parietals
Frontals
Semicircular canals
Snout
Supratemporal
Prefrontals
present
present
fused
paired
prominent
pointed
behind parietal
emarginated
Frontoparietal suture
Pterygopalatine contact
Interpterygoid vacuity
Epipterygoid
Jugal/squamosal contact
Upper temporal fenestra
Presacral vertebrae number
interdigitated
broad
narrow
absent
nearly closed
absent
absent
paired
fused
no prominent
rounded
lateral to parietal
do not encroach
on frontal
smooth
narrow
broad
columnar
present
open
smooth
narrow
narrow
bowed
absent
closed
23
31
23
with kink
rounded
lateral to parietal
-
described by Estes (1983) is a paraphyletic assemblage. With the information available
it is impossible to group Saurillus, Pseudosaurillus, and Saurillodon with Zpexisaurus in
a single monophyletic group.
Atfinity between Zpexisaurus, Saurillus and Pseudosaurillus can be supported by the
presence of about 30 closely packed teeth, a condition not present in other
paramacellodids. Saurillodon Wers from these taxa in the presence of a short powerfd
dentary, less than 15 blunt, broad, conical teeth, and probably reduced limbs
(SeifTert, 1973; Evans, 1995). Some characters that distinguish Zpexisaum as a
different taxon from Saurillus and Pseudosaurillus are the almost complete overlap of
the coronoid process by a broad posterodorsal process of the dentary that extends
near to the tip of the coronoid bone, the posterior overriding of the coronoid bone
by a secondary small dorsal process of the surangular that hides most of the coronoid
laterally, a medially open Meckelian groove showing the primitive squamate pattern,
and the angular restricted laterally to the ventral edge on the jaw, while the
surangular is widely exposed.
Comparison with other earb lizards
The Late Jurassic genus Ardeosaurus and the Late Jurassic-Early Cretaceous
‘Paramacellodidae’are early fossil lizards anatomically similar to Zpexisaurus. Paramacellodids are demonstrated to be scincoids, but the position of Ardeosaurus in the
cladogram is controversial (Evans, 1993; Reynoso, 1996a,b; Reynoso and Evans, in
prep.). Although Ardeosaurus might not be a scincomorph, comparison with Zpexisaurus
is considered to be necessary.
Comparison of Zpexisaurus with Ardeosaurus is difficult because the skull in the best
preserved specimen of Ardeosaurus is exposed only in dorsal aspect (Mateer, 1982)
while the holotype of Zpexisaurus kpexii is visible in ventral view. Most of the
characters listed by Evans ( 1993) when comparing Ardeosaurus with Eichs&thaurus
are not known in Zpexisaurus (Table 2). Characters shared by Ardeosaurus and
’
206
V.-H. REYNOSO AND G . CALLISON
Zpexisaurus are: a narrow interpterygoid vacuity, the lack of contact between the
jugal and squamosal, an upper temporal fenestra closed or nearly closed, and 23
presacral vertebrae. The lack of a jugal-squamosal contact is shared by most
scleroglossans, and a restricted or closed upper temporal fenestra is a synapomorphy
of scincomorphs. Both characters are distributed broadly within Scincomorpha and
uninformative to establish more specific relationships within the group. Although
the interpterygoid vacuities of Ardeosaurus and Zpexiraurus are narrow compared to
that of Eid&aetti.raurus, the condition in the former genera does not differ significantly
from most squamates. This character is also distributed broadly and uninformative.
The presence of 23 presacral vertebrae may be the only derived character shared
by Ardeosaurus and Zpexisaurus. This feature is rare among squamates found otherwise
only in some iguanians, indicating that it must have evolved independently within
scincomorphs. Differences in the shape of the snout, position of the supratemporal,
shape of the frontoparietal suture, relative extension of the pterygopalatine contact,
and shape of the epipterygoid, indicate clearly that Ardeosaurus and Zpexisaums are
distinct (Table 2). Although Ardeosaurus has been classified as a scincomorph (Evans,
1993),results presented by Reynoso (1996a,b)suggest that this genus is not a crowngroup squamate, but a taxon basal to the squamates. Since the position of Zpexisaums
remains within Scincomorpha, the similarity between Ardeosaurus and Zpexisaums is
explained better as convergence.
STRATIGRAPHIC AND BIOGEOGRAPHIC SIGNIFICANCE
The Paramacellodidae is a very successful group of early scincomorphs distributed
worldwide and with a temporal range of about 60 Ma (Evans & Chure, 1998).They
are known from different localities in Europe, Asia, Africa, and North America.
The earliest record was reported by Waldman and Evans (1994) from Middle
Jurassic deposits of Skye, Scotland, and the latest are known from the Middle
Cretaceous deposits of Mongolia (Alifanov, 1993).
The position of Zpexisaurus in the phylogenetic tree as a basal scincoid does not
correlate with the age assigned to the Tlayua deposits where it was collected.
Zpexisaurus is only known from Albian deposits while relatively more derived
paramacellodid lizards are known since the Bathonian (42Ma before). The late
presence of this basal scincoid can be correlated with the similarly late presence of
the basal squamate Huehuecuet@alli mixtecus (Reynoso, 1998a))and late presence of
fossil sphenodontians in Tlayua (Reynoso, 1997; 2000). Zpexisaurus is the fourth
example of a relatively primitive taxon found in Tlayua and gives additional evidence
that supports the hypothesis that this locality functioned as an insular refuge in
which archaic terrestrial forms survived until the Albian (Reynoso 1998b).
CONCLUSIONS
The discovery of Zpexisaurus tepexii, together with the establishment of its phylogenetic relationships, has clarified some aspects of the phylogeny among extant
scincoids and paramacellodids. While the presence of ventral and dorsal osteoscutes
supports the inclusion of the paramacellodids Paramacellodus, Beckhius, Sharovisaurus,
CRETACEOUS SCINCOMORPH FROM MEXICO
207
and Mimobecklesisaurus within the Scincoidea, either as sister group of
Scincidae Cordylidae, or as sister-group of Scincidae alone, the absence of osteoscutes places Saurillus, Saurillodon, and Pseudosaurillus with Zpexisaurus in a position
basal to the Scincoidea. This indicates that Paramacellodidae as it has been
constituted is a paraphyletic assemblage. The trichotomy formed in the strict
consensus tree here presented suggests that it is impossible to define the Scincoidea
without the inclusion of Paramacellodidae.
Paramacellodidae is a poorly known scincoid assemblage of Middle Jurassic to
Middle Cretaceous lizards. The late presence of the basal scincoid Zpexisaurus as a
relict taxon in the Albian sediments of Tlayua, supports the hypothesis that the area
around these deposits was a refuge for ancient terrestrial lepidosaurs.
+
ACKNOWLEDGEMENTS
We are especially pleased to most gratefully acknowledge the assistance of the
Aranguty family: Don Miguel who continues to engender a generous and thoughtful
spirit of cooperation, his sons: Sebastian, Benjamin, Ranulfo, and Faustino who
work the stone quarry and alerted the palaeontological profession of their fabulous
fossil finds, Felix and his wife Magdalena who opened their home to us and provided
delicious cuisine, conversation, and counsel. Dr Shelton Applegate and M. Sc. Luis
Espinosa made the specimens available for study, and Dr Maria del Carmen Perrillat
arranged the loan of the material. Drs Jacques Gauthier, William Presch, and the
late Richard Estes made interestingcomments about the fossil, Dr. Vladimir Alifanov
lent us some photographs of Sharovisaurus, and Drs Robert Carroll, Robert Holmes,
David Dilkes, and Susan Evans read several drafts of the paper. Finally we thank
the comments of two anonymous reviewers. Photographic work was done by McGill
Image Center.
This work was supported by the Instituto de Geologia, Universidad Nacional
Autonoma de MCxico; by a Doctoral Grant and Grant No. IN210394 from the
Direccibn General de Asuntos del Personal AcadCmico, UNAM; Grant No. 5086
from the CONABIO, and by a Research Grant to Dr Carroll from the Natural
Science and Engineering Council of Canada.
A complete version of the data' matrix used in the cladistic analysis can be
obtained via e-mail from the senior author: [email protected].
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Peoples Republic. Kaupia 3: 9-1 3.
Bremer K. 1994. Branch support and tree stability. CMktics Short Papers: 295-304.
Brinkman D. 1980. Structural correlates of tarsals and metatarsal functioning in Iguana (Lacertilia:
Iguanidae) and other lizards. Canadian Journal o f < o o l o ~ 5 8 277-289.
Carroll RL. 1977. The origin of lizards. In: Mahala S, Miles RS, Walker AD, eds. h b h in Vertebrate
Evolution, Volume 4.Linnean Society Symposium Series, 359-396.
Edmund C. 1960. Tooth replacement phenomena in the lower vertebrates. Contributions tu the Ryal
Ontario Museum 52: 1-178.
Estes R. 1983. Sauna tmstria, Amphisbmia. Stuttgart: Gustav Fischer Verlag.
V.-H. REYNOSO AND G . CALLISON
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Estes R Qpeiroz Kd Gauthier JA. 1988. Phylogenetic relationships within Squamata. In: Estes R,
Pregdl G, eds. Phylogeneh Rehtionshhips ofthe Lzard Families. Stanford Stanford University Press.
Etheridge R. 1967. Lizard caudal vertebrae. Cop& 4 699-72 1.
Evans SE. 1993. Jurassic lizard assemblages. Revue de Pahbwbgie 7: 55-65.
Evans SE. 1994. The Solnhofen (Jurassic: Tithonian) lizard genus BavariSaurus: New skull material
and reinterpretation. News Jahrbuch j h r Geologie und Palaontologie, Abhandlungen 192: 37-52.
Evans SE. 1995. Lizards: Evolution, early radiation and biogeography. In: Sixth Symposium on Mesozoic
T i s t r i a l E c o ~ y s hand Biota, Short Papers. Beijing: China Ocean Press, 51-55.
Evans SE Barbadillo J. 1997. Early Cretaceous lizards from Las Hoyas, Spain. <oologicalJoumal of
the Linnean Socieg 119 23-49.
Evans SE Chure DC. 1998. Paramacellodid lizard skulls from the Jurassic Morrison Formation at
Dinosaur National Monument, Utah. Journal of Vihrate Paleontology 1 8 99-1 14.
Frazzetta TH.1962. A functional consideration in cranial kinesis in 1izards.Jouml ofMorphologv 111:
287-320.
Hecht MK Hecht BM. 1984. A new lizard from the Jurassic deposits of Middle Asia. Paleontological
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3 133- 138.
Hoffstetter R. 1964. Les sauria de Jurassique suptrieur et sptcialement les Gekkota de Baviere et
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Hoffstetter R. 1967. Coup d’oeil Sur les sauriens (= Lacertiliens)des couches de Purbeck (Jurassique).
P m b h e s Actuels de Palkontohgie (Evolution des V d b v h ) 163: 349-37 1.
Hoffstetter R Gasc J-P, 1969. Vertebrae and Ribs of Modern Reptiles. In: Gans C, ed. Biologv of
the Reptilia, Volume 1. London: Academic Press 201-310.
LiJL. 1985. A new lizard from Late Jurassic of Subei, Gansu. Vhtebrata PalAsiatica 23: 13-18.
Mateer NJ. 1982. Osteology of the Jurassic lizard Ardeosaurus b@es (Meyer).Palaeontology 25: 46 1-469.
Pantoja-AlorJ. 1992. Geologia y Paleoambiente de la Cantera Tla@a, Tepexi de Rodriguez, Estado
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Prothero DR Estes R. 1980. Late Jurassic Lizards from Como Bluff, Wyoming, and their paleoboiological significance. Nature 286 484-486.
Renous-LCcuru S. 1973. Morphologie comparke du carpe chez les Lepidosauriens actuels (Rhyncoctphales, Lacertiliens, Amphisbtniens). Gegenbaurs rnorphologk?,Jarhbuch, L&ig 119 727-766.
Reynoso V-H. 1996a. Early Cretaceous lepidosaurs (Reptilia: Diapsida) from Central Mtxico and
the phylogeny of the Lepidosauromorpha. Unpublished Ph. D. thesis. McGill University, MontrCal.
Reynoso V-H. 1996b. A primitive lizard from the Early Cretaceous of Mexico and the phylogenetic
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of Central Mexico. Journal of Vdbrate Paleontology 17: 52-59.
Reynoso V-H. 1998a. Huehaecuet@allimixtecm gen. et sp. nov. a primitive lizard from the Early
Cretaceous limestones of Tepexi de Rodriguez, Central Mtxico. Philosophical Eamactions ofthe Royal
Socieg ofbndon 353: 477-500.
Reynoso V-H. 1998b. Acatliintida y el origen insular de la fauna terrestre de Tla@a. Avances en
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Autdnoma del f i t d o de Hida?go. Publicacibn especial 1: 4-1 1.
Reynoso V-H. 2O00. An unusual aquatic sphenodontian from the Tlayua Formation (Albian)Central
Mtxico. Journal ofPaleontology 7 4 133-148.
Richter A. 1994. Lacertilia aus der Unteren Kreide von Ufia und Galve (Spanien) und Anoual
(Marokko). Berlincr GeowissenchJluhe Abhandluqen 1 4 1-147.
Russell AP. 1988. Limb musculature in relation to lizard systematics: a reappraisal. In: Estes R,
Pregill G, eds. Plylogenetic Rehtiomhhips of the Lizard Families. Stanford: Stanford University Press,
493-568.
Seibertz E Buitr6n BE. 1987. Paleontologia y Estratigrafia de 10s Neohibolites del Albiano de Tepexi
de Rodriguez, Edo. de Puebla (Crethcico Medio, MCxico). Sociedad Mexicana de Paleontolo& 1:
285-299.
Seiffert J. 1973. Upper Jurassic lizards from central Portugal. Memoires do Servicio Geologko, Portugal 22:
1-85.
Sukhanov VD. 1976. Some problems of the phylogeny and systematics of lacertilia. Smithoniun
Herpetological Information Senice 3 8 1-15.
Swofford DL. 1993. H U P : Phylogenetic Anabsis Uiing Parsimony, version 3.1.1. Computer program
distributed by The Illinois Natural History Survey, Champaign.
CRETACEOUS SCINCOMORPH FROM MEXICO
209
Waldman M Evans SE. 1994. Lepidosauromorph reptiles from the MiddleJurassic of Skye. <oological
Journal ofthe Linnean Socieh 112: 135-1 50.
Zils WC Werner C Mortiz A Saanane C. 1995. Tendagaru, the most famous dinosaur locality of
Africa. Review survey and future prospects. Docurnenta Naturae, Munich 97: 1-41.
APPENDIX
Data matrix has 25 taxa and (191 - 18 =) 173 characters. All character were unordered. Cells 20,
26, 29, 59, 68, 70, 89, 96, 98, 101, 103, 105, 106, 108, 1 13, 168, 179, and 185 have no character
assigned (excluded), and characters 15, 157, and 158 are uninformative (ignored). Characters 188-191
correspond to characters 203, 190, 207, and 212 from Evans and Chure (1998) respectively.
Designated outgroup taxa: Rhynchocephalia, Kuehneosauridae, Saumshon, and Younginiformes.
Data for Zpexisaums (X =excluded redundant characters; & = and;/ =or):
????0?0????0?000
102X??1??xo?x??oo?o?
I? 1???O 10001????? 10?02x2??0001oxox loo?? 1O??OO 1 1O( 1/
2)00?X???1? 1XOX?OX(1/3)X 1xxox(2/3)? 1 1X?O1?0???020?00????????????????????0?
1 I 1 1 1 1 1?? 12 1 ?
11 110x1 121 1 I 1 112X12(2/3)1lXOOOl12
Data for Paramacellodus:
10000000100010001 1 2X 1 100(0&3)XO(O&
1)X?OOO1? I ?O????O 1001??????
10002x21 (0&1)1001oxox 1OO? 1ooo?oooooooo?x??01O( 1&2)X?X1?X?X?Xx?X??O
1X?????????2??
1 1 1 . . . . . . . . . . . . . . . . . . . . 1 1 1 1 1? 1 1???? 1? 1 1 1??X?1????????X?22??XOOO
1 12
Heuristic search, random addition sequence with 100 replicates and starting seed = 1. Tree-bisectionreconnection (TBR) branch-swapping was performed and MULPARS option was in effect. Multi-state
taxa wcre interpreted as polymorphism.
Length of shortest trees found=848. Four equally parsimonious trees retained; 4th tree found at
replicate number one. Statistics of most parsimonious trees: Tree length =848. Consistency index
(CI)=0.782. Homoplasy index (HI)= 0.745. Retention index (RI)=0.653. Rescaled consistency index
(RC)=0.510.
Strict consensus tree:
7
Paramacellodus
-'- r4
I
-
Cordylidae
Scincidae
Tepexisawvs
Xantusiidae
'
2
-
_ .
Anguidae
Helodematidae
-3-
Lanthanotus
Varanw
Amphisbaenia
32
Dibamidae
I
31
I
I
e
I
2
F
Serpentes
Agamidae
lguiidae
L
Chamaeleontidae
OUTGROW
List of Apomorphies. Character-state optimization =ACCTRAN. Asterisk (*) indicates ambiguous
characters:
Node 31: U ) , 21(1), 24(1),37(1),48(1), 51(1), 65(2)*,82(1),83(1),93(1), 145(2), 150(1), 153(1), 155(1),
156(1), 159(1), 160(2),162(1), 163(1), 164(1), 166(1),167(1), 178(2), 182(2), 184(1), 191(2).
Node 33: 9(1), 10(1)*,23(2)*, 34(1)*, 39(1),40(1),41(1), 44(1), 49(1)*, 58(2)*,60(1),74(1), 75(1)*, 79(1),
2 10
V.-H. REYNOSO AND G . CALLISON
85(1)*,97(1), 104(2),116(1)*, 123(2)*,124(1)*, 130(1),134(1),137(4)*,138(1), 146(1), 147(1)*,189(2)*.
Node 38: 13(1), 17(1), 23(0)*, 54(1)*, 65(0)*,66(0)*,88(1)*, 107(1)*, 112(1), 114(0)*, 133(1), 189(1)*.
Node 4 0 19(2)*, 31(0),85(0)*,90(0)*, 91(0), 97(0)*, 102(2)*, 137(1)*, 139(1), 140(1)*, 144(1)*.
Node 4 4 10(0)*, 22(1), 23(1), 24(0)*, 60(2)*, 71(1)*, 102(3)*, 124(2), 129(2), 138(2), 140(2)*.
Node 45: 36(1)*,76(1), 95(1), 107(0)*, 128(1)*.
Node 46: 18(1)*,83(0)*,97(1)*, 126(1), 127(1), 148(1)*.
Purumacellodu.r 23(0), 47(l), 6 1(l), 63(l), 66(I)*, 76(0),82(0).
Cordylidae: 18(0)*, 19(l), 139(0, 2).
Scincidae: 17(2), 24(1)*, 43(1), 78(1), 141(1), 144(0)*.
EpemSaum 66(1)*,85(1, 2), 104(1), 109(2, 3), 111(1), 124(0), 167(0).
Node 43: 6(1)*, 12(1)*, 73(1), 74(0), 75(0), 79(0), 97(2)*, 100(1)*,121(l)*, 131(1), 132(1).
Node 42: 31(1)*, 37(0), 48(0)*, 60(1)*, 71(0)*,81(1), 87(1), 95(2), 137(3)*, 140(1)*, 142(1)*.
Node 41: 12(0)*, 19(0)*, 24(1)*, 54(0)*, 73(2), 90(1)*, i12(2), 122(1), 137(4)*, 143(1).
Gymnophthalmidae: 11(1), 141(1).
Teiidae: 9(0), 45(l), 46(l), 124(1).
Lacertidae: 23(0), 36(l), 53(l), 1 14(l), 128(l), 139(2).
Xantusiidae: 19(1),27( I), 38(1), 46(1), 52(1), 55(2), 65(l), 66(1)*, 72(l), 125(1).
Node 39: 16(1),28(2), 32(1), 35(1)*, 38(1)*, 52(1)*, 55(2), 65(1)*, 77(1), 78(1), 125(1)*, 134(0), 135(1),
141(1), 145(1).
Gekkonidae: 99(0), 1 1 1(l), 133(0), 147(0)*.
Pygopodidae: 79(0), 109(3), 118(1),156(0).
Node 37: 14(1)*,53(1),56(1), 57(1), 58(0)*, 63(1), 127(1), 128(1), 136(1), 147(0)*.
Node 3 4 7(1)*, 10(0)*, 25(0), 36(1), 137(2)*.
Anguidae: 78(l), 124(2), 126(l), 147(l)*.
Xenosauridae: 18(1), 75(0), 129(2).
Node 36: 2(1)*,4(2)*, 5(1)*, 16(1)*, 27(1),45(1), 58(1)*,61(1)*,64(1),66(1)*,67(1), 69(1),85(2)*,86(1),
88(2)*,92(1), 114(1)*,142(1),156(0), 186(2).
Helodermatidae: 37(0), 65(1), 90(0), 112(0), 119(1), 129(1), 137(3)*, 143(1), 167(0).
Node 35: 3(1), 30(1), 54(0)*, 61(2)*, 62(1), 63(2), 94(1), 107(2), 109(2)*.
hthmotus: 10(0)*,60(3), 66(2), 83(0), 109(3)*.
kranuc: 5(0)*, 9(0), 16(0)*,25(0), 32(l), 36(l), 42(l), 53(0), 88(0), 1 12(2), 124(0), 132(l), 137(5)*.
Node 32: 4(1), 16(1)*, 22(1)*, 27(1), 32(1)*, 35(1),42(1), 45(1)*, 53(2)*, 55(2)*, 60(2)*, 72(1)*, 75(0)*,
100(2)*, 109(3)*,118(1)*, 122(1)*, 156(0), 175(0)*, 186(1), 188(1), 190(0)*.
Amphisbaenia: 5(1), 34(0)*,58(0, 1)*, 138(2), 141(1), 150(3), 187(1).
Dibamidae: 10(0)*, 13(1), 28(2), 43(1), 49(0)*, 51(0), 78(1), 100(3)*, 110(1), 137(0)*, 139(2), 145(0),
148(1),189(0)*,191(0).
Serpentes: 28(2), 33(1), 47(1), 64(I), 65(1), 66(2), 67(1), 85(2)*, 95(2), 136(l), 137(5)*, 145(l), 150(2),
187(1).
Node 27: 6(1), 7(1), 8(1), 12(1), 18(1)*,84(1)*, 143(1).
Node 26: 25(l)*, 80(l)*, 107(l)*, 1 12(l), 137(1).
Agamidae: 97(2).
Iguanidae: 60(1, 3), 84(0)*.
Chamaeleontidae: 38(1), 47(1), 109(3)*, 110(1), 115(1), 118(1), 122(1), 142(1).
-
Two equally parsimonious solutions for Paramacellodidade within Scincoidea:
Paramacellalus
-
47
7
'
scincidae
-
26
List of apomorphies:
Node 4 6 36(1)*, 76(1), 95(1), 107(0)*, 128(1)*.
Node 47: 83(0)*,97(1)*, 126(1), 127(1), 148(1)*.
Node 48: 18(1), 23(0)*, 141(1)*,144(0)*.
Purumacellodus: 47(1), 61(l), 63(1), 66(1)*, 76(0), 82(0).
Scincidae: 17(2),24(l)*, 43(l), 78( 1).
Cordylidae: 19(1), 139(0, 2).
Epehuuw. 66(1)*, 85(1, 2), 104(1), 109(2, 3), 111(1), 124(0), 167(0).
Cordylidae
Tepexisaurus
CRETACEOUS SCINCOMORPH FROM MBXICO
21 1
Tree number 2:
I
Paramacellodus
46
- 4
8
4
Cordylidae
Scincidae
Tepexisaurus
7
List of apomorphies:
Node 46: 36(I)*, 76(l)*, 95(I), 107(0)*,128(I)*.
Node 48: 18(1)*,83(0)*, 97(1)*, 126(1), 127(1), 148(1)*.
Paramacellodus: 23(0), 47(1), 61(1), 63(1), 76(0)*, 82(0).
Node 47: 24(1)*, 66(0), 78(1)*.
Cordylidae: 18(0)*, 19(l), 139(0, 2).
Scincidae: 17(2),43(1), 141(1), 144(0)*.
Tepexzsaum: 85(1, 2), 104(1), 109(2, 3), 111(1), 124(0), 167(0).
Branch support values
Branch support values calculated using the converse constraint option of PAUP and 100 replicates
of random addition sequence heuristic search. Starting seed = 1, branch swapping by tree-bisectionreconnection, and MULPARS option in effect. Multi-state taxa were interpreted as polymorphism.
€
(4)
(2)
r (1)
(4)
- (8) -
r
I
(1)
Paramacellodus
Cordylidae
Scincidae
Tepexisaurus
Gymnophthalmidae
Teiidae
Lacertidae
Xantusiidae
Gekkonidae
Pygopodidae
Anguidae
Helodermatidae
Lanthanotus
Varanus
Amphisbaenia
Dibamidae
Sementes
Agkidae
Iguanidae
Chamaeleontidae
OUTGROUP
I
Total support index, ti=O.O754.
Bootstrap anabsis
Bootstrap method with heuristic search, 100 bootstrap replicates = 100 with starting seed = 1
Bootstrap sampling over non-excluded/non-ignored characters only. Random addition sequence with
10 replicates and starting seed = 1. Tree-bisection-reconnection (TBR) branch-swapping performed
and MULPARS option in effect. Multi-state taxa interpreted as polymorphism.
Bootstrap 50% majority-rule consensus tree:
88
+-
100
- 99
Agamidae
Iguanidae
Chamaeleontidae
456
-51
- - - 52 f 73
56
- 83
-
V.-H. REYNOSO AND G . CALLISON
212
- 99 6,
92
+'-
84
98
zi%idae
Helodermatidae
Lanthanotus
varanus
Gymnophthalmidae
Teiidae
Lacertidae
Xantusiidae
Cordylidae
Scincidae
Paramacellodus
Tepexisaurw
Amphisbaenia
Dibamidae
Gekkonidae
Pygopodidae
I==:
+
-
OUTGROUP