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Introduction
The list of Cretaceous ornithischians from South
America rapidly increased in the last few years
thanks to discoveries of bone remains belonging to
stegosaurs, ankylosaurs, basal ornithopods and
hadrosaurs (e.g., Bonaparte, 1996; Salgado and Coria,
1996; Novas, 1997; Coria, 1999). Particularly, the
Cretaceous record includes ornithopod dinosaurs re-
ferred as to hypsilophodontids (the Cenomanian No-
tohypsilophodon comodorensis from Bajo Barreal Fm.;
Martínez, 1998) and basal iguanodontians (the Ceno-
manian Anabisetia saldiviai, from the Lisandro Fm.,
and the Campanian Gasparinisaura cincosaltensisfrom
the Anacleto Fm.; Coria and Salgado, 1996; Coria,
1999; Garrido, 2000; Coria and Calvo, 2002). Such
discoveries were interpreted by Coria (1999) as sug-
gestive that a diverse evolutionary history of or-
nithopods took place in Gondwana prior to the fau-
nal interchange proposed for the end of the
Cretaceous (Bonaparte, 1986).
Here we report the discovery of an almost com-
plete skeleton of a new iguanodontian dinosaur,
Talenkauen santacrucensis n. gen. et sp. The specimen
was recovered from Late Cretaceous beds exposed in
the SW corner of Patagonia (figure 1.A), a region
poorly explored for dinosaur remains (Novas et al.,
2002a). The new basal ornithopod is odd in the pres-
ence of plate–like structures on both sides of the tho-
rax, whose anatomical meaning will be discussed be-
low. Also, this new dinosaur provides evidence for
an iguanodontian clade endemic to the Southern
Hemisphere, when considered with specimens from
other regions of Gondwana (e.g., Africa, Australia,
AMEGHINIANA (Rev. Asoc. Paleontol. Argent.) - 41 (1): 75-82. Buenos Aires, 30-03-2004 ISSN 0002-7014
©Asociación Paleontológica Argentina AMGHB2-0002-7014/04$00.00+.50
1Laboratorio de Anatomía Comparada, Museo Argentino de Cien-
cias Naturales “Bernardino Rivadavia”, Av. Ángel Gallardo 470,
1405 Buenos Aires, Argentina, fernovas@yahoo.com.ar
2Consejo Nacional de Investigaciones Científicas y Técnicas.
A new basal iguanodontian (Dinosauria, Ornithischia)
from the Upper Cretaceous of Patagonia
Fernando E. NOVAS1,2, Andrea V. CAMBIASO1and Alfredo AMBROSIO1
Key words. Dinosauria. Ornithopoda. Patagonia. Cretaceous.
Palabras clave. Dinosauria. Ornithopoda. Patagonia. Cretácico.
Abstract. We report the discovery of an almost complete skeleton of a new iguanodontian dinosaur,
Talenkauen santacrucensis n. gen. et sp., from Maastrichtiano rocks of southwestern Patagonia. Talenkauen
is odd in the presence of plate-like structures on both sides of the thorax, which are better interpreted as
uncinate processes than dermal armor. Talenkauen and the also Maastrichtian Thescelosaurus neglectus
Gilmore from North America, represent the only two ornithischians in which this peculiar feature is cur-
rently known. Some derived features unite Talenkauen with other Gondwanan ornithopods, but all the ev-
idence does not offer enough support for an iguanodontian clade endemic from the Southern Hemisphere.
Small- to medium-sized ornithischians appear to have been the dominant plant-eating dinosaurs in
Antarctica and Australia during the Cretaceous, in contrast with the outstanding abundance of medium
sized to giant sauropods in central Gondwana (e.g., South America, Africa, India).
Resumen. UNNUEVO IGUANODONTE BASAL (DINOSAURIA, ORNITHISCHIA) DEL CRETÁCICO SUPERIOR DE LA PATA-
GONIA.Se reporta el descubrimiento de un esqueleto casi completo de un nuevo dinosaurio iguanodonte,
Talenkauen santacrucensis n. gen. et sp., de rocas de edad Maastrichtiano del sudoeste de Patagonia.
Talenkauen posee placas en ambos lados del tórax, las cuales son interpretadas como procesos uncinados
en lugar de armadura dérmica. Talenkaueny Thescelosaurus neglectus (Maastrichtiano, América del Norte),
son los únicos dos ornitisquios en los que se conoce esta peculiar característica. Algunos caracteres de-
rivados unen a Talenkauen con otros ornitópodos gondwánicos, pero el conjunto de la evidencia disponible
no ofrece sustento suficiente para reconocer un clado de iguanodontes endémico del Hemisferio Sur. Los
ornitisquios de pequeño y mediano tamaño parecen haber sido los dinosaurios herbívoros dominantes en
Antártida y Australia durante el Cretácico, contrastando con la gran abundancia de saurópodos de medi-
ano a gran tamaño registrada en Gondwana central (p. ej., América del Sur, África, India).
F.E. Novas and A.V. Cambiaso76
New Zealand). The new material helps to under-
stand better the adaptive radiation of basal or-
nithopods in Gondwana and the paleobiogeography
of dinosaur faunas at the end of the Mesozoic.
Abbreviations. MPM, Museo Padre Molina, Río
Gallegos, Santa Cruz.
Systematic paleontology
ORNITHISCHIA Seeley, 1888
ORNITHOPODA Marsh, 1871
IGUANODONTIA Dollo, 1888
EUIGUANODONTIA Coria and Salgado, 1996
Genus Talenkauen Novas, Cambiaso
and Ambrosio n. gen.
Derivatio nominis. “Talenk”, small, ”kauen”, skull, in
Aonikenk Indian language (Moreno, 1997), in refer-
ence to the proportionally small head of the animal.
Type species. Talenkauen santacrucensis Novas,
Cambiaso and Ambrosio n. sp.
Diagnosis. Same as species.
Talenkauen santacrucensis Novas, Cambiaso
and Ambrosio n. sp.
Figures 1.B, C and 2.A, B
Diagnosis. Autapomorphies diagnosing Talenkauen
santacrucensis include: well–developed epipophysis
on cervical 3, and plate–like uncinate processes on
the rib cage. The following reversals emerge from the
cladistic analysis: lacrimal and premaxilla not in con-
tact, and dentaries convergent rostrally.
Derivatio nominis. Santacrucensis, referring to the
southern Argentine province of Santa Cruz.
Holotype. MPM–10001, partially articulated speci-
men preserving rostrum, jaws, and teeth, precaudal
vertebral column and ribs, pectoral and pelvic gir-
dles, and fore– and hind limb bones (figures 1.B,C).
The specimen was found articulated in a cross–bed-
ded, fining–upward, medium–grained sandstone, in-
terpreted as a fluvial channel body. The material was
collected in February 2000.
Locality and horizon. Los Hornos Hill, southern
coast of Viedma Lake, Santa Cruz Province,
Argentina (Lat. 49° 51’ 16.2” S, Long. 72° 06’ 26.3”
W) (figure 1.A). Pari Aike Fm., Upper Cretaceous,
Maastrichtian (Kraemer and Riccardi, 1997;
Ambrosio, 2003). This Maastrichtian age is also
supported by recently collected samples with
foraminifera and dinoflagellates from beds under-
lying the Pari Aike Formation (Ambrosio, 2003;
Ottone and Ronchi, pers. com.), thus superceding
previous assumptions for an older age (Novas et al.,
20002a). The Pari Aike Fm. also yielded ti-
tanosaurid remains of medium to gigantic sizes, as
well as fragmentary bones of theropods, crocodiles,
and turtles.
Description. The holotype specimen of Talenkauen
santacrucensis n. gen. et n. sp. (figures 1.B,C) mea-
sures no more than 4 meters long, thus representing
one of the first large, non–hadrosaurian euornitho-
pod bone remains reported from South America. The
head looks comparatively small with respect to body
size, being slightly larger than in Dryosaurus. The
premaxilla (figure 2.A.) is dorsally concave, and de-
fines much of the external nares. Two empty alveoli
are indicative of the presence of premaxillary teeth, a
plesiomorphic character for an iguanodontian. The
posterior process of the premaxilla is elongate, but it
does not contact the lacrimal, in contrast with more
derived iguanodontians. The maxilla is triangular,
with a single dorsal process almost centrally posi-
tioned, resembling Dryosaurus (Galton, 1983). Worn
maxillary teeth are rhomboid in side view, each with
a prominent primary ridge on the labial crown sur-
face, representing an euiguanodontian synapomor-
phy (Coria and Salgado, 1996). The V–shaped pre-
dentary bears, as in most iguanodontians, a pair of
elongate tapering processes and a bilobate ventral
process for articulation with the dentaries. The den-
tary is primitive in possessing anteriorly tapering
dorsal and ventral margins.
The presacral vertebral column of Talenkauen is
composed of 9 cervicals and 16 dorsals, a normal
count for a basal iguanodontian. A net of ossified ten-
dons extends along both sides of the neural spines
from the first dorsal through at least the first four
preserved sacral vertebrae. Cervical vertebrae exhib-
it moderately developed neural spines and slightly
down–curved postzygapophyses, characters that are
less derived than in dryomorph ornithopods. Howe-
ver, cervical 3 exhibits prominent epipophysis, a fea-
ture uncommon in ornithischian dinosaurs. As a
whole, the neck of Talenkauen looks elongate com-
pared to those of Hypsilophodon and Dryosaurus
(Sues and Norman, 1990).
AMEGHINIANA 41 (1), 2004
Figure 1. A, Map indicating fossil locality. B, C, Talenkauen santacrucensis n. gen. et n. sp. MPM 10001 (holotype). B, Partially articulat-
ed skeleton in right lateral aspect. C,Reconstructed skeleton. Abbreviations: ax, axis; cv 9, ninth cervical vertebra; d, dentary; d1, first dor-
sal vertebra; d16, sixteen dorsal vertebra; f, femur; fib, fibula; h, humerus; il, ilium; mtt, metatarsals II-IV; mx, maxilla; ot, ossified ten-
dons; p, pubis; pd, predentary; ph, pedal phalanges; pmx, premaxilla; sc, scapula-coracoid; sk, skull; r, radius; t, tibia; up, uncinate
processes / A, Mapa indicando la localidad del hallazgo. B, C, Talenkauen santacrucensis n. gen. et n. sp. MPM 10001 (holotipo). B,Esqueleto
parcialmente articulado en vista lateral derecha. C, Esqueleto reconstruído. Abreviaturas: ax, axis; cv 9, novena vértebra cervical; d, dentario; d1,
primera vértebra dorsal; d16, dieciséisava vértebra dorsal; f, fémur; fib, fíbula; h, húmero; il, ilion; mtt, metatarsos II-IV; mx, maxilar; ot, tendones os-
ificados; p, pubis; pd, predentario; ph, falanges del pie; pmx, premaxilar; sc, escápula-coracoides; sk, cráneo; r, radio; t, tibia; up, procesos uncinados.
Cretaceous ornithischian from Patagonia 77
AMEGHINIANA 41 (1), 2004
F.E. Novas and A.V. Cambiaso78
The humerus is slender, weakly expanded at its
extremities, and the deltopectoral crest is extremely
reduced, differing from the remaining ornithopods
in which this crest is more developed (e.g.,
Thescelosaurus, Dryosaurus, Camptosaurus, Iguano-
don). This peculiar morphology is shared with the
hypsilophodontid Notohypsilophodon (Martínez,
1998) and the iguanodontian Anabisetia (Coria and
Calvo, 2002), both from the Cenomanian of
Patagonia.
The ilium is slender, dorsoventrally low, and
shorter than the femur. The dorsal margin is sig-
moidal in outline, as is usual in iguanodontians
(Coria and Salgado, 1996; Coria and Calvo, 2002).
The prepubic process of the pubis is cranially elon-
gate, ending at the level of the 13th dorsal. It is latero-
medially flat and dorsoventrally deep, a condition
shared with derived iguanodontians (Norman and
Weishampel, 1990; Coria, 1999). The femur and tibia
are massive, the latter being shorter than the femur
(tibia/femur ratio: 0.94), as is usual for graviportal
ornithopods. The anterior trochanter of the femur is
appressed, but not fused, to the greater trochanter.
Metatarsal III of Talenkauen is a robust bone (3.3 cm
wide), whereas metatarsal II is notably narrow trans-
versely (1.9 cm wide), thus departing from the more
robust proportions of metatarsal II seen in most or-
nithopods (e.g., Tenontosaurus, Hypsilophodon, Dryos-
aurus, Camptosaurus, Iguanodon).
An outstanding feature of Talenkauen is the pres-
ence of plate–like, polygonal structures on both sides
of the thorax (figure 2.B). The plates are thin (no
more than 3 mm thick) and dorsoventrally elongate
(the major diameter is 180 mm). The external surface
of the plates is smooth, lacking foramina or grooves,
and no muscle scars are apparent. The plates are lo-
cated mid–length on dorsal ribs 1 through 8, but are
not fused to the ribs.
Discussion
Among the anatomical features of Talenkauen, the
presence of polygonal plates on both sides of the tho-
rax is outstanding. This character is shared with the
Maastrichtian hypsilophodontid Thescelosaurus ne-
glectus from North America (Fischer et al., 2000), and
these are the only two ornithopods in which such
plates are documented. At first glance, the shared
presence of plate–like structures on the chest raised
the possibility that Talenkauen and Thescelosaurus
were closely related. However, no other derived
characters uniting these ornithopods were recog-
nized. Moreover, several iguanodontian features pre-
sent in Talenkauen are absent in Thescelosaurus. As
well, many features distinctive of the latter taxon are
lacking in the Patagonian genus. The presence of pla-
te–like structures in the hypsilophodontid Thescelo-
saurus and the iguanodontian Talenkauenimplies that
such plates may have been independently acquired.
However, because ossification depends on maturity,
size, and sex, their presence among ornithopods may
be more widespread than thought.
The plate–like structures of Talenkauen are dis-
missed as defensive devices because of their fragility
and their arrangement in a restricted portion of the
thorax. This contrasts with the thick and profusely
ornamented dermal ossifications of armored di-
nosaurs (e.g., ankylosaurs, stegosaurs, titanosaurids).
The absence of vascular grooves on their surfaces,
their proximity to the caudal margin of ribs, as well
as their serial arrangement on the thorax, support
their homology with the uncinate processes present
in living and extinct diapsids (e.g., Sphenodon, croco-
diles, basal maniraptorans, and most birds;
Heilmann, 1926; Paul, 2002). It is remarkable, howev-
er, that the supposed uncinate processes of
Talenkauen and Thescelosaurus are considerably ex-
panded and widely overlap each other, representing
a condition not yet recorded in other extinct diapsids,
in which such processes are modest, strip–like pro-
jections. The presence and development of uncinate
processes is far from being functionally understood
(Paul, 2002). As far as birds are concerned, uncinate
processes participate in thoracic movements for lung
ventilation (Fedde, 1987). Because the length of the
uncinate processes in birds is proportional to the ef-
fectiveness of the external intercostal muscles to set
the ribs into motion, a particularly well–developed
AMEGHINIANA 41 (1), 2004
Figure 2. Talenkauen santacrucensis n. gen. et n. sp. MPM 10001 (holotype). A, Rostrum in left lateral aspect. B, Detail of uncinate
processes on ribs corresponding to 5th through 9th dorsal vertebrae. C, Cladogram depicting phylogenetic relationships of Talenkauen
santacrucensis within Ornithopoda. Most parsimonious tree generated by NONA (Goloboff, 1993) using exact solutions (L= 82, CI= 63,
RI= 74). For characters and taxa see: Coria and Salgado (1996), Winkler et al. (1997) and Sereno (1999). Data matrix and character list is
in the Appendix. Topology of the present cladogram differs from that obtained by Coria and Calvo (2002), in which Gasparinisaura,
Anabisetia, and Dryomorpha form an unresolved polytomy. Abbreviations: d, dentary; mx, maxilla; pd, predentary; pm, premaxillary;
r, ribs; up, uncinate processes./ A, B, Talenkauen santacrucensis n. gen. et n. sp. MPM 10001 (holotipo). A, Rostro en vista lateral izquierda.
B, Detalle de los procesos uncinados en las costillas correspondientes a las vértebras dorsales 5ta a 9na. C, Cladograma que ilustra las relaciones filo-
genéticas de Talenkauen santacrucensis dentro de Ornithopoda. El resultado (consistente en un único árbol) fue generado por NONA (Goloboff,
1993) usando soluciones exactas (L= 82, CI= 63, RI= 74). Para los caracteres y taxones ver: Coria y Salgado (1996), Winkler et al. (1997) y Sereno
(1999). La matriz de datos y la lista de caracteres se muestra en el apéndice. Abreviaturas: d, dentario; mx, maxilar; pd, predentario; pm, premaxi-
lar; r, costillas; up, procesos uncinados.
Cretaceous ornithischian from Patagonia 79
AMEGHINIANA 41 (1), 2004
F.E. Novas and A.V. Cambiaso80
musculature would be expected in Talenkauen. This
suggests an important participation in rib cage dy-
namics through well–developed intercostal muscles.
The available fossil record clearly shows that dur-
ing the Cretaceous, ornithopod dinosaurs were di-
verse on southern landmasses (Taquet, 1976;
Bartholomai and Molnar, 1981; Rich and V.–Rich,
1989; Hooker et al., 1991; Coria, 1999; Novas et al.,
2002b), including a wide array of Mid– to Late
Cretaceous hypsilophodontids (e.g., Fulgurotherium,
Notohypsilophodon, Antarctic hypsilophodontid; Rich
and V.–Rich, 1989; Hooker et al., 1991; Martínez,
1998) and basal iguanodontians (e.g., Gasparinisaura,
Anabisetia, Talenkauen, Muttaburrasaurus, Ourano-
saurus, Kangnasaurus, Lurdusaurus, Antarctic iguan-
odontian; Taquet, 1976; Bartholomai and Molnar,
1981; Cooper, 1985; Coria and Salgado, 1996; Salgado
et al., 1997; Coria, 1999; Taquet and Russell, 1999;
Coria and Calvo, 2002; Novas et al., 2002b).
Although documentation of ornithopod diversity
in the southern continents has considerably in-
creased in the last years, the recognition of an iguan-
odontid clade endemic to Gondwana has not been
possible. Some features emerged in the present study
as potential synapomorphies uniting Talenkauenwith
some of these Gondwanan iguanodontians. For ex-
ample, the greatly reduced deltopectoral crest on the
humerus is shared with Anabisetia (Coria and Calvo,
2002) and Notohypsilophodon (Martínez, 1998), and a
transversally compressed second metatarsal is sha-
red with the Patagonian Anabisetia and Gasparinisaura
(Salgado et al., 1997), the South African Kangnasaurus
(Cooper, 1985), and an unnamed Late Cretaceous
iguanodontian from the Antarctic Peninsula (Novas
et al., 2002b). However, in the context of all anatomi-
cal data no support currently exists for the identifica-
tion of a clade of southern iguanodontians (figure
2.C). Moreover, the South American Anabisetia,
Talenkauen, and Gasparinisaura constitute succesively
more remote outgroups of the globally distributed
Dryomorpha.
Paleobiogeographical isolation between Gondwa-
na and Laurasia has been postulated for most of the
Cretaceous (Bonaparte, 1986). Some dinosaur clades
with outstanding autapomorphies (e.g., abelisaurid
theropods) have been considered as the result of this
prolonged endemism (Bonaparte, 1986; Novas, 1997).
Notably, the effects of such physical isolation are
weakly manifested in the morphology of the south-
ern ornithopods. With the exception of some bizarre
features such as the developed cranial bulla of the
Australian Muttaburrasaurus (Bartholomai and Mol-
nar, 1981), the elongate neural spines of the African
Ouranosaurus (Taquet, 1976), and possibly the ex-
panded uncinate processes of Talenkauen, the anato-
my of basal iguanodontians from Gondwana resem-
bles that of their Jurassic and Cretaceous relatives
from Laurasia.
Available evidence suggests that Cretaceous di-
nosaur faunas of South America were dominated by
the herbivorous Sauropoda, represented by abun-
dant skeletal remains belonging to diplodocimorphs
and titanosauriforms (Novas, 1997). Even in south-
ern Patagonia, including the fossil locality where
Talenkauen was found, remains of titanosaurs are
quite abundant. Contrary to expectations, the
Cretaceous record of Antarctic dinosaurs does not in-
clude at the moment any sauropod remains, but it
does ornithischians. A remarkable disparity in the
relative abundance and taxonomic diversity of
sauropods and ornithischians is apparent in the
Gondwanan realm: whereas in South America,
Madagascar and India the Cretaceous record of
sauropods overwhelms that of ornithischians, in
southern Gondwana (e.g., Antarctica, Australia, and
New Zealand; Bartholomai and Molnar, 1981;
Gasparini et al., 1987; Rich and V.–Rich, 1989; Hooker
et al., 1991; Wiffen, 1996; Rich et al., 1999; Case et al.,
2000; Novas et al., 2002b) the sauropod record is
sparse. Instead, ornithischians of different affiliation
(e.g., iguanodontians, hypsilophodontids, nodosau-
rids) have been frequently found in the higher paleo-
latitudes of Gondwana. It is concluded that herbivo-
rous dinosaurs were not evenly distributed on the
Gondwanan landmasses, but a certain degree of
provincialism is apparent.
Acknowledgements
We thank D.A. Russell, R.A. Coria, D. Weishampel, Pat V.
Rich, T. Rich and G. Paul for their clever observations and review
of the manuscript; A. Chinsamy for access to South African
Museum collections; E. Vidal and his family for logistic support in
the field; E. Bellosi, D. Hauk, M. Isasi, J. Canale, A. Scanferla, for
their participation in the field; C. Pappolio for noting that a previ-
ous genus name we had chosen for the new dinosaur was already
occupied for the Patagonian coleopteran Chaltenia; G. Ottone and
D. Ronchi for indentification of palynological and microfaunistic
associations, respectively. Thanks to National Geographic Society,
Agencia Nacional de Promoción Científica y Tecnológica, the
Jurassic Foundation Akapol S.A. (Buenos Aires), and Renault
Argentina for their valuable financial assistance. Specimen prepa-
ration was done by M. Isasi and S. Reuil. Photographs were taken
by H. Canuti and S. Peralta.
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Recibido: 6 de febrero de 2003.
Aceptado: 4 de agosto de 2003.
Appendix
List of characters and data matrix used to analyze the phylo-
genetic relationships of Talenkauen santacrucensis n. gen. et n. sp.
The list of characters is modified from the following sources:
Winkler et al.(1997), Coria and Salgado (1996), and Sereno (1999).
The data matrix was analyzed cladistically using the NONA (ver.
1.8) software package (Goloboff, 1993), available from http:
//www.cladistics.org. Lesothosaurus, Scutellosaurus, and
Marginocephalia were employed as outgroups, and the tree was
rooted on Lesothosaurus. One tree was obtained, which has the fol-
lowing values: L = 82, Ci = 63, Ri = 74 / Lista de caracteres y matriz
de datos utilizados para analizar las relaciones filogenéticas de
Talenkauen santacrucensis. La lista de caracteres ha sido modificada de
las siguientes fuentes: Winkler et al. (1997), Coria y Salgado (1996) y
Sereno (1999). La matriz de datos fue analizada cladísticamente utilizan-
do el software de NONA (ver. 1.8) (Goloboff, 1993), disponible en http:
//www.cladistics.org. Lesothosaurus, Scutellosaurus y Margino-
cephalia fueron utilizados como grupos externos, y el árbol fue enraizado
en Lesothosaurus. Se ha obtenido un solo árbol, el cual presenta los
siguientes valores: L = 82, Ci = 63, Ri = 74.
List of characters / Lista de caracteres
1. Contact of lacrimal / premaxilla: (0) absent; (1) present.
2. Premaxillary teeth: (0) present; (1) absent.
AMEGHINIANA 41 (1), 2004
F.E. Novas and A.V. Cambiaso82
3. Eversion of premaxilla: (0) absent; (1) present.
4. Anterior processes on maxilla: (0) 1 process; (1) 2 processes.
5. Tooth ridges connect to denticles: (0) absent; (1) present.
6. Strong central ridge on maxillary tooth: (0) absent; (1) present.
7. Denticles on predentary: (0) absent; (1) present.
8. Ventral processes on predentary: (0) single; (1) double; (2)
wedge–shaped predentary.
9. Size of antorbital fenestra or fossa: (0) large; (1) small.
10. Quadratojugal size: (0) large; (1) reduced.
11. Ossified sternal ribs: (0) absent; (1) present.
12. Ossified hypaxial tendons: (0) present; (1) absent.
13. Humerus/scapula lenght ratio: (0) <1; (1) >=1.
14. Number of phalanges on manus digit III: (0) 4; (1) 3.
15. Number of vertebrae in sacrum (ordered): (0) 5; (1) 6; (2) >6.
16. Prepubic process (ordered): (0) absent; (1) short; (2) long rod;
(3) long shallow blade; (4) deep anteriorly.
17. Femur–distal anterior intercondylar groove (ordered): (0)
none, (1) shallow = <10% of anterior–posterior width; (1) deep
= >10% anterior–posterior width.
18. Metatarsal V/III length ratio: (0) > 0.3; (1) < 0.3; (2) MT V ab-
sent.
19. Relative size of the palpebral: (0) 80% or more of the maximal
anteroposterior width of the orbit; (1) 70% or less of the maxi-
mal anteroposterior width of the orbit.
20. Antorbital fossa shape: (0) triangular; (1) circular or ovate.
21. Dorsal and ventral margins of the dentary: (0) rostrally con-
vergent; (1) parallel.
22. Dorsal margin of iliac blade: (0) convex; (1) sinuous.
23. Size of the external nares relative to the basal skull length: (0)
less than 15%; (1) 20% or more.
24. Enamel of the medial side of maxillary tooth: (0) present; (1)
absent.
25. Participation of the jugal in the antorbital fenestra: (0) includ-
ed; (1) excluded.
26. Jugal–postorbital articulation: (0) medially–faced; (1) lateral-
ly–faced.
27. Brevis shelf: (0) reduced; (1) well developed.
28. Metatarsal I: (0) present; (1) reduced or absent.
29. Maxillary tooth crowns: (0) low; (1) high.
30. Foot on the distal ischial shaft: (0) absent; (1) present.
31. Ischial shaft: (0) laterally flattened; (1) rounded in cross sec-
tion.
32. Caudal process of jugal: (0) well developed; (1) reduced.
33. Relative position of the ventral margin of the infratemporal
fenestra: (0) below the base of the orbit; (1) above the base of the
orbit.
34. Position of the obturator process on the ischial shaft: (0) prox-
imal; (1) distal.
35. Deltopectoral crest, form: (0) projecting from shaft; (1) low or
rounded in lateral or medial view.
36. Premaxilla, orientation of lower rim: (0) ventrolateral; (1) later-
al.
37. Quadrate, free portion of shaft: (0) 10% or less; or (1) 30% or
more of quadrate height.
38. Maxillary crown, anteroposterior width: (0) equal; or (1) nar-
rower than dentary crowns.
39. Maxillary crown, shape: (0) subtriangular; (1) dia-
mond–shaped; (2) lanceolate.
40. Maxillary primary ridge strength: (0) less; or (1) more promi-
nent than dentary primary ridge.
41. Postaxial cervicals, neural spine height: (0) prominent; (1)
rudimentary.
42. Cervicals 4–9, form of central surfaces: (0) slightly amph-
icoelous; (1) slightly opisthocoelous; or (2) strongly opistho-
coelous.
43. Manual digit I ungual, length: (0) shorter; or (1) longer than
manual digit II ungual.
44. Premaxilla–maxilla diastema: (0) absent ; (1) present.
45. Ischial obturator process: (0) absent; (1) present.
46. MT II transverse compression: (0) absent; (1) present.
47. Deltopectoral crest: (0) well developed; (1) less developed.
Diagnostic characters / Caracteres diagnósticos
Unambiguous character support for clades found in the analy-
sis of the data set is presented below. The first number refers to the
character on the list above, and the derived state is given in brack-
ets./ Se presentan a continuación los caracteres no ambiguos diagnósti-
cos de cada nodo resultantes del análisis de datos. El primer número se
refiere al carácter mientras que los estados derivados se expresan entre
paréntesis.
Ornithopoda 1(1), 44(1)
Euornithopoda 25(1), 45(1)
Hypsilophodontia 11(1), 15(0), 16(2), 32(1), 34(1)
Thescelosaurus 18(1)
Hypsilophodon 33(1)
Iguanodontia 3(1), 7(1), 9(1), 14(1), 17(1), 20(1), 21(1), 23(1), 36(1)
Tenontosaurus 24(1), 33(1), 42(1)
Muttaburrasaurus + Euiguanodontia 6(1), 10(1)
Euiguanodontia 37(1), 41(1), 46(1)
Gasparinisaura 16(2), 17(0), 28(1), 32(1)
Talenkauen santacrucensis + Anabisetia saldiviai + Dryomorpha 38(1)
Talenkauen santacrucensis 1(0), 21(0)
Anabisetia saldiviai + Dryomorpha 5(0), 39(1), 40(1)
Dryomorpha 28(1), 29(1), 46(0)
Dryosaurus 41(0)
Ankylopollexia 18(2), 43(1)
AMEGHINIANA 41 (1), 2004
Lesothosaurus 00000 00000 00000 00000 00000 00000 000x0 0000x 00?00 00
Scutellosaurus 00000 00000 00000 000?? 00?00 00000 000x0 0000x 00000 00
Marginocephalia 00001 10001 0?001 31000 00000 00000 000x0 00000 00000 00
Heterodontosaurus 1000? 00200 01001 10?00 00000 00000 00000 00000 00010 00
Talenkauen 00101 111?? ??1?? 3???? 01?0? ??00? ????1 1?100 10?1? 11
Thescelosaurus ?0??1 0???? 10100 2010? 01?0? ?0000 01011 ??000 00?11 00
Hypsilophodon 10000 00000 10100 20010 00001 ?0000 01111 00000 00111 00
Gasparinisaura ????1 1??11 ????1 20101 11??1 11100 01000 ?100? 1??11 10
Anabisetia ????0 1???? ??1?? 311?? 11??? ?1001 1??01 ???11 ????1 11
Muttaburrasaurus 1???1 1??11 ????1 31??1 ?1101 ??00? ?00?1 1000x 00?11 00
Tenontosaurus 10100 01010 00011 31011 11111 00000 00100 10000 01011 00
Dryosaurus 11110 11111 01011 31111 11110 11111 10001 11111 01011 00
Ankylopollexia 11110 11111 01011 31211 11110 11111 10001 11111 12111 00
Data matrix / Matriz de caracteres
