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Journal of Systematic Palaeontology
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/tjsp20
A new hadrosaurid (Dinosauria: Ornithischia) from
the Late Cretaceous of northern Patagonia and the
radiation of South American hadrosaurids
Sebastián Rozadilla, Federico Brissón-Egli, Federico Lisandro Agnolín, Alexis
Mauro Aranciaga-Rolando & Fernando Emilio Novas
To cite this article: Sebastián Rozadilla, Federico Brissón-Egli, Federico Lisandro Agnolín, Alexis
Mauro Aranciaga-Rolando & Fernando Emilio Novas (2022): A new hadrosaurid (Dinosauria:
Ornithischia) from the Late Cretaceous of northern Patagonia and the radiation of South American
hadrosaurids, Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2021.2020917
To link to this article: https://doi.org/10.1080/14772019.2021.2020917
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Published online: 24 Feb 2022.
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A new hadrosaurid (Dinosauria: Ornithischia) from the Late Cretaceous of
northern Patagonia and the radiation of South American hadrosaurids
Sebasti
an Rozadilla
a,b
, Federico Briss
on-Egli
a,b
, Federico Lisandro Agnol
ın
a,b,c
, Alexis Mauro Aranciaga-
Rolando
a,b
and Fernando Emilio Novas
a,b
a
Laboratorio de Anatom
ıa Comparada y Evoluci
on de los Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino
Rivadavia’, Av.
Angel Gallardo 470, Buenos Aires, Argentina;
b
CONICET, Consejo Nacional de Investigaciones Cientıficas y
T
ecnicas, Argentina;
c
Fundaci
on de Historia Natural ‘F
elix de Azara’, Universidad Maim
onides, Hidalgo 775, Buenos
Aires, Argentina
(Received 30 August 2021; accepted 15 December 2021)
Here we describe a new hadrosaurid from the Upper Cretaceous (Campanian–Maastrichtian) Allen Formation of R
ıo
Negro Province, north-west Patagonia. The new taxon is based on cranial and postcranial elements from subadult and
adult specimens. The new taxon may have reached 8–9 m in total body length, and it is diagnosed by a unique
combination of characters, including a very low maxilla with respect to the dentary, and a dentary with a prominent and
elongate anterior process with a deep groove on its anterior end, among other features. The new taxon is known from
well-preserved elements and constitutes one of the most complete hadrosaurids known from South America. Features of
the teeth, cranial and postcranial bones of the new taxon overlap with those of other hadrosaurid specimens previously
recorded from this continent. This new evidence allows us to recognize that Secernosaurus koerneri,Bonapartesaurus
rionegrensis and ‘Kritosaurus’australis are valid taxa. The latter can be distinguished from the other South American
taxa, as well as from Kritosaurus from North America. Thus, a new generic name is proposed for the species
‘Kritosaurus’australis. Phylogenetic analysis recovers a new clade of South American hadrosaurids composed of the
new taxon, ‘Kritosaurus’australis,Bonapartesaurus and Secernosaurus. The new South American clade is tentatively
nested among Kritosaurini and is supported by several traits, including an ilium with a subhorizontal ridge separating
the preacetabular notch from the pubic pedicle, a longitudinal ridge on the dorsal surface of the postacetabular process,
and a twisted distal end of the postacetabular process. The recovery of a monophyletic clade of South American
hadrosaurids indicates that the history of the clade on Gondwanan landmasses is far from well understood, and new
discoveries may change the current picture of the taxonomy and phylogenetic relationships of southern duck-
billed dinosaurs.
http://zoobank.org/urn:lsid:zoobank.org:pub:6C6F0056-9D3A-4097-A10E-2E33C9DB76B9
Keywords: Hadrosauridae; Patagonia; Late Cretaceous; Secernosaurus koerneri;‘Kritosaurus’australis
Introduction
Hadrosauroidea is one of the most numerically abundant
and taxonomically diverse ornithischian clades from the
Cretaceous of the Northern Hemisphere (Horner et al.
2004). Hadrosauridae is one of the most diverse dino-
saur families (excluding birds), and most taxa are dis-
tributed in Europe, Asia and North America (Lund &
Gates 2006; Prieto-M
arquez 2010a; Prieto-M
arquez
et al. 2013). By contrast, hadrosaurids are under-repre-
sented in southern continents, being found mostly in
South America with a few remains reported from Africa
and Antarctica (Rich et al. 1999; Case et al. 2000;
Longrich et al. 2021).
As far as South America is concerned, fossil sites that
have yielded hadrosaurid bone remains are currently
limited to the southern Argentinian provinces of La
Pampa, Rio Negro, Chubut and Santa Cruz
(Casamiquela 1964; Bonaparte et al. 1984; Martinelli &
Forasiepi 2004;Ju
arez-Valieri et al. 2010; Apestegu
ıa
et al. 2012; Coria 2014,2016; Coria et al. 2012;
Gasparini et al. 2015; Cruzado-Caballero & Powell
2017; Ibiricu et al. 2021; Rozadilla et al. 2021) and
southern Chile (Magallanes Region; Soto-Acu~
na
et al. 2014).
The first fossils of Patagonian hadrosaurids were
reported by Casamiquela (1964), who proposed that the
presence of hadrosaurids in southern South America
was the consequence of a dispersal event from North
America at the end of the Cretaceous. This hypothesis
was subsequently reinforced with the discovery of more
informative and complete specimens (Bonaparte et al.
Corresponding author. Email: sebastianrozadilla@gmail.com
#The Trustees of the Natural History Museum, London 2022. All rights reserved.
Journal of Systematic Palaeontology, 2022
http://dx.doi.org/10.1080/14772019.2021.2020917
Published online 24 Feb 2022
1984). Since then, the record of hadrosaurids in South
America, and specifically Patagonia, has greatly
increased. Previously, five different hadrosaurid taxa
were named: Secernosaurus koerneri (Brett-Surman
1979), Kritosaurus australis (Bonaparte et al. 1984),
Bonapartesaurus rionegrensis (Cruzado-Caballero &
Powell 2017), Lapampasaurus cholinoi (Coria et al.
2012) and Willinakaqe salitralensis (Ju
arez-Valieri et al.
2010). Despite the fact that the Patagonian record of
hadrosaurids is the best known from Gondwana, the
fragmentary nature of these specimens makes the taxo-
nomic identities of these taxa uncertain (Prieto-M
arquez
& Salinas 2010; Coria 2014,2016; Ibiricu et al. 2021;
Rozadilla et al. 2021). Regarding ‘Kritosaurus’austra-
lis, Prieto-M
arquez & Salinas (2010) proposed that this
taxon is a junior synonym of Secernosaurus koerneri,
which was described by Brett-Surman (1979) and comes
from the Colhue Huapi Formation (Maastrichtian) of
Chubut Province, Patagonia. However, this suggestion
was analysed in depth by Coria (2014) who remarked
on the existence of strong morphological differences
between the two, and concluded that they may be
regarded as valid taxa. Furthermore, Coria (2014)
reported the presence of several undescribed hadrosaurid
morphotypes present in the Allen Formation.
Conversely, Willinakaqe salitralensis was regarded by
Cruzado-Caballero & Coria (2016)asanomen dubium
and should be considered an indeterminate hadrosaurid.
Most South American hadrosaurid taxa come from
Campanian–Maastrichtian sedimentary units in northern
Patagonia: the Los Alamitos Formation yielded remains
of ‘Kritosaurus’australis (Bonaparte et al.1984), and
the Allen Formation (Juarez-Valieri et al. 2010; Coria
2013; Cruzado-Caballero & Powell 2017) yielded the
remains of Willinakaqe,Lapampasaurus and
Bonapartesaurus. The presence of three different hadro-
saurid taxa from the Allen Formation, plus two unde-
scribed hadrosaurid morphotypes (Coria 2014,2016),
has led to a great debate about the taxonomic validity of
some of these dinosaurs, hampering the referral of
specimens to any previously known taxon (Coria et al.
2012; Coria 2014; Cruzado-Caballero & Coria 2016).
Furthermore, the phylogenetic position of Patagonian
hadrosaurids is hotly debated, with some authors sup-
porting the idea that hadrosaurids arrived in South
America via a land bridge between the Americas during
the Late Cretaceous (Casamiquela 1964; Bonaparte
1984; Prieto-M
arquez & Salinas 2010; Coria 2013),
while others suggest that South American hadrosaurids
belong to a distinct Gondwanan clade (Salinas &
Ju
arez-Valieri 2004; Agnol
ınet al.2010; Ezcurra &
Agnol
ın2012; Rozadilla et al.2021).
The aim of the present contribution is to describe a
new hadrosaurid species from the Campanian–
Maastrichtian Allen Formation of Rio Negro Province,
Argentina, and to compare it with other South American
hadrosaurids with the aim of clarifying the taxonomy
and phylogenetic relationships of southern hadrosaurids
as a whole.
Material and methods
Locality and age
The holotype specimen here described comes from
Matadero Hill (393001200S, 672201900W; Fig. 1),
located within Arriagada Farm, 70 km south of General
Roca city, R
ıo Negro Province, Argentina (Fig. 1A).
The specimen was found in an area of approximately 2
m
2
. The bones were found intermingled and disarticu-
lated. The paratype specimens were found in a quarry
approximately 23 m from the holotype. The latter were
found in close association with remains of the titanosaur
Menucocelsior arriagadai (Aranciaga-Rolando et al.
2022)(Fig. 1B).
The specimens come from the top of the Allen
Formation, Upper Cretaceous (Maastrichtian), of the
Neuqu
en Group (Garrido 2010). This stratigraphical unit
is composed of sandstones, mudstones and pelites reach-
ing about 70 m thick and represents shallow water-
courses, bearing freshwater and brackish-water
vertebrates and molluscs (Casad
ıo1994; Martinelli &
Forasiepi 2004).
Osteological nomenclature
We employ traditional or ‘Romerian’orientation terms
(Wilson 2006). ‘Anterior’and ‘posterior’, for example,
are used rather than the veterinarian alternatives ‘rostral’
or ‘cranial’and ‘caudal’. We follow the proposal of
Coria (2014) and consider Secernosaurus koerneri and
‘K.’australis as different taxa throughout the pre-
sent work.
Three-dimensional scanning
Several cranial bones were digitally scanned by surface
scanning with a Shining 3D EinScan-Pro scanner at the
Laboratorio de Desarrollo de T
ecnicas Paleontol
ogicas
(MACN). The resulting .obj files were then rendered
with 3D Slicer software and converted to image files.
Institutional abbreviations
MACN-PV, Museo Argentino de Ciencias Naturales
‘Bernardino Rivadavia’, Colecci
on de Paleovertebrados,
2 S. Rozadilla et al.
A new hadrosaurid from Patagonia 3
Ciudad Aut
onoma de Buenos Aires, Argentina; MPCA-
PV, Museo de la Ciudad de Cipoletti, Cipoletti, R
ıo
Negro Province, Argentina; MPCN, Museo Patag
onico
de Ciencias Naturales, General Roca, R
ıo Negro
Province, Argentina.
Systematic palaeontology
Superorder Dinosauria Owen, 1842
Order Ornithischia Seeley, 1887
Infraorder Ornithopoda Marsh, 1881
Family Hadrosauridae Cope, 1869
Subfamily Saurolophinae Brown, 1914
Tribe Kritosaurini Lapparent & Lavocat, 1955
Kelumapusaura machi gen. et sp. nov.
(Figs 1–10,12)
Holotype. MPCN-PV-807, partial skull preserving the
left maxilla with teeth, right prefrontal, right postorbital,
left pterygoid, left prootic, predentary, three mandibular
teeth, left dentary and the anterior end of the right den-
tary, a third cervical vertebra, sacrum preserving sacrals
1, 2 and the anterior half of 3, a caudal neural arch, left
sternal plate and a sternal rib (Fig. 1C).
Paratypes. Remains found in a bonebed located 23 m
from the site that yielded the holotype and belonging to
different individuals, including an incomplete right den-
tary (MPCN-PV-808), sacral and caudal vertebrae
(MPCN-PV-809), right scapula (MPCN-PV-810), left
ilium (MPCN-PV-811), right ischium (MPCN-PV-912),
right femur (MPCN-PV-813) and metatarsal IV
(MPCN-PV-814) (Fig. 1C).
Diagnosis. Kelumapusaura machi is diagnosed on the
basis of the following unique combination of characters
(autapomorphies marked with an asterisk): a shallow
maxilla when compared with the dorsoventral height of
the dentary; maxilla with a dorsoventrally low medial
surface dorsal to the medial row of foramina; maxilla
with a groove forming a constriction on the anteroven-
tral process; maxilla with a posterodorsal margin of the
lateral surface forming a thick ridge that houses the pal-
atine and pterygoid processes; postorbital with short to
absent medial process on the skull roof; dentary sym-
physis with anteriorly oriented sub-triangular processes,
ventrally delimited by a deep groove on its anterior end,
resulting in a bilobate outline in lateral view; anterior
end of the dentary with a crescent-shaped concavity on
its lateral surface; first sacral with anterior articular sur-
faces strongly anterodorsally facing and obliquely ori-
ented; scapula with a longitudinal groove dorsal to the
acromial process; proportionally narrow scapular neck,
being 0.5 times the dorsoventral length of the proximal
end; and scapula with a nearly straight (or weakly
arched) scapular blade.
Etymology. The root of the generic name, ‘Kelumapu’,
means ‘red earth’in the Mapudungun language. The
specific name ‘machi’refers to the shaman of the
Mapuche people.
Description
Skull. Available skull bones of the holotype of
Kelumapusaura machi are very well-preserved.
However, they invariably show several broken parts and
eroded surfaces, suggesting that they suffered some kind
of transportation.
Maxilla. This bone (Fig. 2) is nearly complete, lacking
only the dorsal process and part of the anterolateral sur-
face. It is dorsoventrally low, and anteroposteriorly elon-
gated. The ventral margin is slightly concave and at
least 36 tooth positions are counted. In some cases,
there are two teeth occupying the same occlu-
sal position.
In medial view (Fig. 2B, B) the maxilla of
Kelumapusaura is nearly smooth and shows a dorsal
row of foramina that delimits the dental parapet. This
row of foramina is dorsally convex and runs from the
posterior-most part of the maxillary body up to the base
of the anterodorsal process of the maxilla. Dorsal to the
row of foramina, the medial surface of the bone is con-
vex. This surface is dorsoventrally lower in
Kelumapusaura than in other hadrosaurs and is consid-
ered an autapomorphic feature of this taxon. The dorsal
edge of the bone is laterally tilted and forms a laterally
oriented shelf that extends up to the base of the antero-
dorsal process of the maxilla. The row of foramina is
separated by a very wide and flat surface from the ven-
tral groove. This groove is subparallel to the row of for-
amina and is close to the alveolar margin. Both the row
3
Figure 1. A, map of the fossiliferous locality. B, diagram showing the disposition of Kelumapusaura machi gen. et sp. nov. bones
(holotype in yellow, paratypes shaded in dark grey) in the field, together with remains of the titanosaur Menucocelsior arriagadai
(Aranciaga-Rolando et al.2022) (shaded in light grey). The oblique line represents the 23 m between the bones. The left side of the
box indicates the bones of the holotype specimen (MPCN-PV-807), whereas the right side indicates the position of paratypes in the
field. C, silhouette of Kelumapusaura machi gen. et sp. nov. The bones in yellow belong to the holotype (MPCN-PV-807) and white
bones belong to the paratypes (not to scale). The grey silhouette represents the largest paratype specimen (MPCN-PV-808).
4 S. Rozadilla et al.
and groove cited above are more distant from each other
in Kelumapusaura than in ‘K’. australis.
The anterior end of the maxilla bears anterodorsal
and anteroventral processes. The dorsal surface of the
anterodorsal process rises smoothly from the maxilla.
The anterodorsal process is long, transversely com-
pressed and anteroventrally projected. When compared
with the main axis of the bone, this process is medially
positioned. Its medial surface is convex, shows longitu-
dinal striations and exhibits two longitudinally oriented
ridges. The dorsal one of these ridges is prominent and
is ventrally delimited by a nearly straight surface that
separates it from the ventral ridge. This ventral ridge is
more anteriorly placed and forms the dorsal limit of a
ventral concavity. In medial view, it shows a longitudin-
ally concave surface that is ventrally delimited by a
thickened margin. This margin exhibits a shallow longi-
tudinal groove. Kelumapusaura differs from
Pararhabdodon,Eotrachodon and Gryposaurus (Gates
& Sampson 2007; Prieto-M
arquez et al.2013,2016)
because in the latter three genera there exists a strong
dorsal projection.
The anterodorsal process is separated from the antero-
ventral one by a deep concave margin. The
anteroventral process of Kelumapusaura is relatively
thick and short. It is more anteriorly projected than in
Aquilarhinus,Probrachylophosaurus and
Brachylophosaurus (Prieto-M
arquez 2005; Freedman-
Fowler & Horner 2015; Prieto-M
arquez et al.2019),
and it does not form a wide and sublaminar spoon-like
process, in contrast to Edmontosaurus or
Prosaurolophus (Horner 1992; Xing et al.2017). The
anterior end of the anteroventral process is nearly trans-
versely compressed, while it is sub-triangular in cross-
section posteriorly. The anterior margin of the antero-
ventral process forms a lip that is separated from the
main body of the process by a groove-like constriction.
The ventral margin of the process forms a relatively
thick and rugose crest. In lateral view the anteroventral
process is longitudinally excavated by a crescent-shaped,
deep and obliquely oriented groove that represents the
premaxillary articular surface. It is delimited by promin-
ent edges and becomes wider posteriorly. In medial
view the anteroventral process is dorsally delimited by a
concavity that extends up to the anterior portion of the
articulation facet for the premaxilla. In lateral view the
anterior half of the bone is nearly flat but badly weath-
ered. Anterior to the jugal facet, the maxilla of
Figure 2. Left maxilla of Kelumapusaura machi gen. et sp. nov. (MPCN-PV-807, holotype) in A,
A, lateral, B, B,medial, C, C,
dorsal, D, D,ventral, E,
E, anterior and F, F,posterior views. Abbreviations: adp, anterodorsal process; avp, anteroventral process;
eptr, ectopterygoid ridge; epts, ectopterygoid shelf; f, fenestra; for, foramen; gr, groove; mr, maxillary dental row; pb, posterior
buttress; pdr, posterodorsal ridge; pmx, premaxilla articular surface; rf, row of foramina; vg, ventral groove. Scale bar ¼10 cm.
A new hadrosaurid from Patagonia 5
Kelumapusaura is anteroposteriorly longer than in
‘K.’australis.
In lateral view (Fig. 2A, A) the posterodorsal margin
of the maxilla forms an angle of about 45with the
horizontal. This margin is represented by a robust ridge
that houses both the palatine and pterygoid processes.
These processes reach the end of the maxillary body
and are confluent with the dorsal row of foramina. The
anterodorsal margin of the maxilla is relatively straight
in Kelumapusaura, unlike Probrachylophosaurus and
Brachylophosaurus in which it is concave (Prieto-
M
arquez 2005; Freedman-Fowler & Horner 2015).
The palatine process of the maxilla forms a thick,
sharp ridge (Fig. 2C, C). Its surface is ornamented by
wrinkles and grooves. In medial view it extends along
half of the thickened dorsal margin. It is anteriorly
delimited by a shallow but well-defined groove repre-
senting the basal portion of the internal antorbital fenes-
tra. The pterygoid process is located posterior to the
palatine process. The base of the pterygoid process is
located at the lateral surface of the bone and is sepa-
rated from the posterior end of the bone by a concave
surface. The posterior end of the maxilla is a relatively
shallow bump. The thickened dorsal margin is separated
from the jugal facet and ectopterygoid shelf by a wide
and deep ovoid concavity.
The jugal facet is poorly preserved; it is represented
by a subvertically oriented concave surface and is ven-
trally delimited by a longitudinal thick ridge (Fig. 2A,
A). In medial view this ridge is anterodorsally to poster-
oventrally oriented and represents more than 50% of the
total length of the preserved maxilla. Its ventral surface
is gently concave and, ventral to its anterior end, an
elliptical foramen is present.
The ectopterygoid shelf is a transversely wide and
gently concave surface that becomes narrower towards
its posterior end (Fig. 2A, A). It is delimited by a sharp
and low crest that represents the dorsal margin of the
ectopterygoid ridge. The ectopterygoid ridge of
Kelumapusaura is slightly inclined posteroventrally, dif-
fering from the strongly inclined ridge of ‘K.’australis
(Prieto-M
arquez & Salinas 2010). The ventral margin of
the ectopterygoid ridge is delimited by a concave sur-
face. The surface ventral to the ectopterygoid shelf is
narrower than in ‘K.’australis,Probrachylophosaurus,
Brachylophosaurus and Acristavus (Prieto-M
arquez
2005; Prieto-M
arquez & Salinas 2010; Gates et al.
2011; Freedman-Fowler & Horner 2015). The posterior
margin of the bone is blunt and shows a striated surface
(Fig. 2F, F). It is transversely narrower than in
‘K.’australis.
Prefrontal. The right prefrontal is nearly complete (Fig.
3). It contacted the nasal medially, the lacrimal
anteroventrally and the frontal posteromedially. In dorsal
view, it is sub-triangular in contour with its apex anteri-
orly oriented (Fig. 3A, A). Its anterior half is trans-
versely thin in dorsal view and becomes two times
transversely wider posteriorly. The prefrontal is slen-
derer in ‘K.’australis. The orbital margin is ornamented
by longitudinal striations that match the morphology of
those present in the postorbital (Fig. 3C, C
). Near its
anterior end, there is an indentation on the orbital mar-
gin, which is deeper than in ‘K.’australis. At the same
level on both the dorsal and ventral surfaces of the pre-
frontal there are two foramina that do not seem to be
connected (Fig. 3B, B). By contrast, ‘K.’australis has a
single foramen on its dorsal surface and none on its
ventral surface. The lacrimal articulation is ventrally
facing and sub-triangular in contour. Medially, the nasal
suture displays a deep and well-defined groove that is
anteroposteriorly oriented and reaches the posterior end
of the prefrontal (Fig. 3D, D). This groove widens pos-
teriorly. The dorsal margin of the nasal suture is slightly
dorsally oriented.
Postorbital. The nearly complete right postorbital lacks
only the tip of the squamosal process and the ventral tip
of the jugal process. The postorbital is notably robust
and thick, with a sub-triangular and anteroposteriorly
broad central region and a convex external surface (Fig.
4A, A). In this aspect it resembles ‘K.’australis and to
some degree some specimens of Gryposaurus (the latter
has invariably less massive postorbitals; Prieto-M
arquez
2010b; Prieto-M
arquez & Salinas 2010); this contrasts
with most hadrosaurids which have gracile
postorbitals with concave lateral surfaces (e.g.
Saurolophus,Prosaurolophus,Brachylophosaurus,
Probrachylophosaurus: Horner 1992; Prieto-M
arquez
2005; Bell 2011; Freedman-Fowler & Horner 2015).
The surface for the contact with the frontal is dorso-
ventrally tall, especially on its anterior half; it is antero-
laterally oriented and deeply incised by striations (Fig.
4B, B). As in most hadrosaurids the orbital margin is
ornamented by ridges and grooves (e.g. Horner 1992;
Prieto-M
arquez 2005,2010b). Kelumapusaura lacks a
well-developed medial process, differing from ‘K.’aus-
tralis and Gryposaurus (Prieto-M
arquez & Salinas
2010; Prieto-M
arquez 2012). The jugal process is ven-
trally tapering and sub-triangular in contour when
viewed laterally (Fig. 4A, A). The anteroventral surface
of the ventral process is striated. The anterior margin of
the jugal process of the postorbital is subvertical. This
process is relatively thick and sub-triangular in cross-
section. On the ventral surface of the postorbital and
medial to the ventral process, there is a well-developed
and concave articulation for the laterosphenoid (Fig. 4B,
B). The medial surface of the jugal process bears a
6 S. Rozadilla et al.
dorsoventrally expanded and stout lamina that poster-
iorly delimits the orbit (Fig. 4C, C). The squamosal pro-
cess is sub-rectangular in contour in lateral view,
whereas in dorsal view it is posteriorly tapering. In lat-
eral view, the dorsal margin of the postorbital is flat, as
in ‘K.’australis,Brachylophosaurus and Acristavus
Figure 3. Right prefrontal of Kelumapusaura machi gen. et sp. nov. (MPCN-PV-807, holotype) in A,
A, dorsal, B, B,ventral, C, C,
lateral and D, D,medial views. Abbreviations: fas, articular surface for frontal; for, foramina; gr, groove; las, articular surface for
lacrimal; orm, orbital margin. Scale bar¼2 cm.
A new hadrosaurid from Patagonia 7
(Prieto-M
arquez 2005; Cuthbertson & Holmes 2010;
Prieto-M
arquez & Salinas 2010; Gates et al.2011), and
is not posterodorsally oriented in contrast to
Saurolophus,Prosaurolophus and several kritosaurines
such as Gryposaurus,Kritosaurus and Kundurosaurus
(Marya
nska & Osm
olska 1981; Horner 1992; Gates &
Sampson 2007; Prieto-M
arquez 2010b,2012; Bell 2011;
Godefroit et al.2012a; Lowi-Merri & Evans 2020), nor
forming a dorsal arch as in Lambeosaurinae (e.g. Evans
& Reisz 2007; Godefroit et al.2012b; Velasco et al.
Figure 4. Right postorbital of Kelumapusaura machi gen. et sp. nov. (MPCN-PV-807, holotype) in A,
A, lateral, B, B,medial, C,
C,anterior, D, D,ventral, E,
E, dorsal and F, F,posterior views. Abbreviations: ap, anterior process; fas, articular surface for
frontal; jp, jugal process; lats, articular surface for laterosphenoid; ml, medial lamina; orm, orbital margin; scaf, articular facet for
squamosal; scp, squamosal process. Scale bar ¼5 cm.
8 S. Rozadilla et al.
2021). On its ventral surface, a well-developed ‘V’-
shaped facet for articulation with the squamosal is pre-
sent (Fig. 4B, B).
Prootic. Only the caudal process of the left prootic is
preserved. It is wedge-shaped and its medial surface is
covered with subparallel striations representing the con-
tact for the opisthotic-exoccipital complex (Fig. 5).
Pterygoid. The pterygoid is incompletely preserved and
lacks its dorsal quadrate process (Fig. 6) (Heaton 1972).
Its anterolateral surface is convex centrally and becomes
concave towards its dorsal and ventral ends (Fig. 6B,
B). The facet for the articulation with the maxillar
ectopterygoid shelf is represented by a well-delimited
concave and crescent-like articular surface, differing
from the convex one present in Saurolophus,
Edmontosaurus and Brachylophosaurus (Prieto-M
arquez
2005; Xing et al.2017). This surface is posteromedially
overlapped by a lamina (Fig. 6B, B). The ventral tip of
the ectopterygoid process bears a shallow groove on its
ventral surface. The anterolateral surface of the ectopter-
ygoid process bears a short ridge, while on its postero-
medial surface there is a strong keel that runs from the
ventral end of this process to the dorsal end of the palat-
ine process. The surface lateral to this keel is wide and
concave. The ventral quadrate process is short and blunt.
On its posteromedial surface there is a strong keel that
runs from the ventral quadrate process to join the ectop-
terygoid-palatine ridge on the central portion of the pter-
ygoid, forming a medial buttress (Heaton 1972). These
keels delimit a deeply concave sub-triangular surface
that widens ventrally. This surface is wider than in
Saurolophus,Prosaurolophus,Edmontosaurus and
Canardia (Horner 1992; Prieto-M
arquez et al.2013;
Xing et al.2017), but narrower and dorsoventrally
higher than in Brachylophosaurus (Prieto-M
arquez
2005). Only the base of the posterior alar projection for
the quadrate is preserved, which is posteromedially con-
cave (Fig. 6A, A).
Predentary. The predentary is nearly complete (Fig. 7).
It is horseshoe-shaped with lateral rami extending sub-
parallel to each other and forming nearly a right angle
with the rostral bar. The predentary is dorsoventrally
low and transversely wide with its dorsoventral height
at the midline representing <30% of its total transverse
width (Fig. 7A, B). The predentary of Kelumapusaura is
proportionally wider than in Saurolophus (Horner 1992)
but narrower than in Brachylophosaurus (Prieto-
M
arquez 2005) when comparing the anteroposterior
length of the lateral rami to the transverse bar. The oral
margin is located anterior and dorsal to the main body
of the predentary. It is bounded posteriorly by a row of
foramina. The anterior surface of the predentary is
obliquely oriented at about 45when compared with the
main axis of the lateral rami (Fig. 8D, D). The antero-
ventral margin is pierced by several foramina (Fig. 8C,
C). On the labial surface of the rostral bar there are two
very large foramina, one at each side of the predentary
midline. The median ventral process is sub-triangular in
cross-section and bears a low median ridge, a condition
regarded as diagnostic of Saurolophinae (Prieto
M
arquez et al.2010)(Fig. 7A, A). The denticles do not
extend onto the lateral rami of the predentary, resem-
bling the condition in derived hadrosaurids. The two
central denticles are relatively large and are followed by
a row of six smaller lateral denticles. The denticles of
Kelumapusaura are sub-triangular in shape and trans-
versely narrow, differing from those of Gryposaurus
which are wider at the base (Bertozzo et al.2017), and
differing from the shorter and blunter ones of
Eotrachodon (Prieto-M
arquez et al.2016). The ventral
surface of the transverse rostral bar shows a well-devel-
oped, transversely oriented groove that is caudally
Figure 5. Preserved portion of the prootic of Kelumapusaura
machi gen. et sp. nov. (MPCN-PV-807, holotype) in A, lateral,
B, anterior and C, posterior views. Scale bar ¼1 cm.
A new hadrosaurid from Patagonia 9
delimited by the median ventral process and the bases
of the bilobate processes, which are not preserved. The
lateral rami are transversely compressed with subverti-
cally oriented lateral surfaces. In dorsal view they
slightly converge medially (Fig. 7A, A). The dorsal sur-
face of the lateral rami is raised and forms a thick ridge.
In dorsal view, this ridge is laterally concave and placed
lingually on the lateral rami.
Dentary. The left dentary of the holotype is almost com-
pletely preserved (Fig. 8). The main axis of the body rep-
resents approximately 3.5 times the dorsoventral height at
the mid-length of the dental battery. In lateral view, the
dentary is gently sigmoidal in contour (Fig. 8A, A). Its
dorsal and ventral margins are subparallel to each other,
with the exception of its anterior-most end, in which the
ventral edge turns down and forms the anterior ramus that
contacts the predentary. In cross-section, the dorsal third
of the lateral surface is slightly concave to nearly straight,
at mid-height it becomes strongly convex, and ventrally
the convexity becomes weak.
In dorsal view, the dentary is gently laterally concave.
The ventral downturn of the anterior ramus is stronger
than in Saurolophus,Brachylophosaurus,Acristavus,
Edmontosaurus and Zhanghenglong (Horner 1992;Bell
2011; Gates et al.2011;Xinget al.2014,2017). In anter-
ior view, the anterior ramus is medially tilted ventrally,
forming a wide angle with the main axis of the dentary
(Fig. 8F, F). The ventral surface of the anterior ramus has
a deep groove that is observed in lateral and medial views
(Fig. 8A, B). This groove receives the median ventral
processes of the predentary and results in a bilobate anter-
ior end of the ramus. In ‘K.’australis this groove is poorly
excavated and is more posteriorly extended, not forming a
bilobate outline. In ventral view, the medial half of the
symphyseal processes of Kelumapusaura is anteriorly pro-
jected, forming sub-triangular articular surfaces for the pre-
dentary. This differs from ‘K.’australis, which has a
straight anterior margin on the predentary articular surface
(Coria 2009). The symphyseal region is transversely nar-
rower in Kelumapusaura than in ‘K.’australis. In lateral
view, the lateral surface of the Kelumapusaura dentary has
on its anterior half a row of foramina that forms a sig-
moidal outline (Fig. 8A, A). This row of foramina is pre-
sent at the limit between the concave and convex areas of
the lateral surface of the dentary.
Figure 6. Left pterygoid of Kelumapusaura machi (MPCN-PV-807, holotype) in A,
A, dorsomedial, B, B,ventrolateral, C, C,
anterior and D, D,posterior views. Abbreviations: eas, articular surface for ectopterygoid; epp, ectopterygoid process; epr,
ectopterygoid ridge; mp, medial process; pr, palatine process; vqp, ventral quadrate process; vr, vomer ridge. Scale bar ¼2 cm.
10 S. Rozadilla et al.
Figure 7. Predentary of Kelumapusaura machi gen. et sp. nov. (MPCN-PV-807, holotype) in A,
A, dorsal, B, B,ventral, C, C,
anterior and D, D,lateral views. Abbreviations: dent, oral denticles; for, foramina; plp, posterolateral process; vmp, ventromedial
process; vr, ventral ridge. Scale bar ¼5 cm.
A new hadrosaurid from Patagonia 11
The dental battery has 35 alveoli (Fig. 8B, B). The
alveoli are transversely narrow and aligned perpendicu-
lar to the alveolar margin of the dentary. In medial
view, the dental battery is dorsoventrally higher on its
mid-portion, with relatively smaller alveoli anteriorly
and posteriorly. The ventral margin of the dental battery
is ventrally convex. There is a short edentulous area
between the anterior end of the dental battery and the
anterior margin of the dentary (Fig. 8B, B). The medial
surface of this edentulous area is dorsoventrally
Figure 8. Left dentary of Kelumapusaura machi gen. et sp. nov. (MPCN-PV-807, holotype) in A,
A, lateral, B, B,medial, C, C,
posterior, D, D,dorsal, E,
E, ventral and F, F,anterior views. Selected mandibular teeth in G, anterior and H, lingual views. I, J,
size comparison between the holotype dentary (MPCN-PV-807) and paratype MPCN-PV-808. Abbreviations: ag, anterior groove;
ar, anterior ramus; cp, coronoid process; csc, crescent-shaped concavity; db, dental battery; ds, dentary shelf; esl, edentulous slope;
for, foramina; maf, mastoid fossa; mg, meckelian groove; mr, medial ridge; prd, articular surface for predentary; spl, articular
surface for splenial. Scale bars ¼10 cm.
12 S. Rozadilla et al.
concave. Posterior to the dental battery, the dentary has
a posteriorly projected sub-triangular projection that
contacts the splenial. The coronoid process projects
anterodorsally; it is anteroposteriorly wider at its base
and becomes narrower dorsally, and shows a slight dor-
sal expansion as occurs in Acristavus (Gates et al.
2011), differing from the anteriorly inclined coronoid
process present in Gryposaurus,Kritosaurus,
Saurolophus,Edmontosaurus and Arenysaurus (Prieto-
M
arquez 2010b; Bell 2011; Cruzado-Caballero et al.
2013; Bertozzo et al.2017; Xing et al.2017). The cor-
onoid process is lateral to and separated from the dental
battery by a deep longitudinal groove (Fig. 8D, D). The
medial surface of the coronoid process has a short but
strong crest that extends anteroventrally from the poster-
odorsal end of the coronoid process. In posterior view,
the coronoid process tapers dorsally and bears a sub-tri-
angular and deep mandibular adductor fossa on its pos-
terior surface (Fig. 8C, C). Ventral to the dental battery,
the Meckelian groove runs anteroposteriorly and
becomes wider and deeper posteriorly.
Two different dentaries have been recovered.
Specimen MPCN-PV-808 is notably larger than the
Kalumapusaura holotype (nearly 70% larger than the
latter). This dentary is heavily damaged but its anterior
half is well-preserved. It shows a combination of char-
acters that are present in the holotype, including the
apomorphic bilobate anterior end of the bone. MPCN-
PV-808 differs from the holotype in that the anterior
ramus is proportionally anteroposteriorly longer and the
angle between the main axis of the bone and the ventral
slope of the anterior ramus is notably smooth. The
larger size of MPCN-PV-808 when compared with the
holotype might indicate that these differences could be
the result of different ontogenetic stages, as occurs in
Saurolophus (Bell 2011).
Dentition. Thirty-six maxillary teeth are still in place in
the maxilla (Fig. 2). Most details of the enamelled side
of the maxillary teeth are obscured by the walls of the
maxillary alveolar chamber. Each maxillary alveolus
houses at least two functional teeth, as occurs in other
hadrosaurids (Sternberg 1936; Horner 1992;
Weishampel et al. 1993). Most of the preserved maxil-
lary crowns are strongly worn from use and, conse-
quently, many of their features are lost. The crowns of
the teeth are enamelled only on the labial side, as occurs
in all hadrosaurid maxillary teeth (Horner et al.2004).
The enamelled surface bears a strong primary ridge at
mid-length. Accessory ridges are occasionally present as
poorly developed crests that reach the basal third of the
tooth. Fainter ridges define the distal and mesial ends of
the crown. Marginal denticles are hardly discernible,
probably because of wear. The lingual surface of the
crown is flat and featureless.
Three isolated dentary teeth have been recovered
(Fig. 8G, H). The crowns of the teeth are only enam-
elled on the lingual side, as in other hadrosaurids. The
enamelled surface of the crown is lanceolate with a
prominent primary ridge. The tooth crown is apicoba-
sally elongate, being nearly four times higher than
mesiodistally wide. The primary ridge is transversely
narrow and straight. The accessory ridges are repre-
sented by faint striations at the sides of the primary
ridge in the basal three-quarters of the crown. The mar-
ginal denticles are small and mammillary. In labial
view, the crown tapers apically. The crown forms an
angle of approximately 30with respect to the tooth
root, a feature common in saurolophine hadrosaurids
(Sternberg 1936; Horner 1992; Weishampel et al.1993).
Axial skeleton. An incomplete cervical, partial sacrum
and a caudal neural arch and centra are known from the
holotype specimen. A large number of incomplete cau-
dals and a nearly complete caudal are known from the
paratype. As occurs with other Patagonian hadrosaurids,
no ossified tendons of Kelumapusaura were found.
Bonaparte and Rougier (1987) remarked on the entire
absence of ossified tendons on the partially articulated
‘K.’australis skeleton. It is possible that the absence of
ossified tendons on the tail of these South American
hadrosaurids may be the result of a natural absence and
not a taphonomical bias. If this is true, it may constitute
an additional derived feature shared by these two taxa.
Cervical vertebra. A partial cervical vertebra probably
corresponds to the C3 or C4, based on comparisons
with ‘K.’australis (Coria 2014). The vertebra is par-
tially eroded, with the centrum poorly preserved.
Nevertheless, the preserved part suggests that this elem-
ent was wider transversely than long anteroposteriorly,
as occurs in most hadrosaurids (Lull & Wright 1942)
(Fig. 9A–D). The neural canal is ovoidal and very wide,
representing one-third of the total vertebral width. The
neural canal is delimited by thick neural arch pedicles,
that are much longer anteroposteriorly than transversely
wide. The neural spine and zygapophyses are partially
eroded. The bases of the diapophyses are preserved.
They are sub-triangular in cross-section and are located
roughly at the same height as the prezygapophyses. A
shallow but wide supraprezygodiapophyseal fossa is pre-
sent. The neural spine is relatively low, transversely
broad and strongly posteriorly oriented. The prespinal
lamina is transversely thick.
Sacrum. The sacrum is strongly weathered and pre-
serves the right half of sacrals 1–3(Fig. 9E). The neural
arches of sacrals 2 and 3 preserve parts of their
A new hadrosaurid from Patagonia 13
14 S. Rozadilla et al.
transverse processes. The tip of the transverse process is
expanded and forms a wide sub-triangular surface for
articulation with the ilium. In dorsal view, the transverse
process is sub-rectangular in outline and is slightly
anteriorly projected. The ventral surface of the trans-
verse process is anteroposteriorly compressed, forming a
keeled lamina. This lamina is sub-triangular in outline
when viewed laterally and shows strongly concave
anterior and posterior surfaces.
The sacral centra have strongly concave lateral surfaces.
Sacral 1 has several ovoidal foramina on its lateral surface.
Sacrals 1 and 2 exhibit a prominent and thick ventral keel
(Fig. 9F), differing from Bonapartesaurus, which only
shows a ventral keel on its first sacral centrum (Cruzado-
Caballero & Powell 2017). In lateral view, sacral centrum
1 is dorsoventrally higher than the posterior ones; its
height decreases posteriorly. The anterior articular surface
is strongly obliquely oriented, with its ventral margin more
anteriorly positioned than the dorsal one. This condition is
unknown in other hadrosaurids and may be an autapomor-
phy of Kelumapusaura. Sacral ribs project laterally and
are fused to each other by means of a subhorizontally ori-
ented thick ridge that is strongly eroded. Dorsal to this lat-
eral ridge, the sacral ribs are represented by subhorizontal
laminae that are dorsally tapering.
Caudal vertebrae. A single caudal neural arch from the
holotype and 10 proximal, middle and distal caudal ver-
tebrae from the paratypes were recovered. The most
proximal and distal caudal vertebrae are represented by
isolated centra. The centra of the proximal caudals are
anteroposteriorly short and amphiplatyan, with hex-
agonal-shaped articular surfaces, subhorizontally ori-
ented dorsal and ventral surfaces, ventral surfaces
excavated by a shallow longitudinal groove bounded by
two longitudinal keels that end in well-developed
haemal facets, and lateral surfaces pierced by a large
number of elongate nutrient foramina. Distal caudals are
very similar but differ in having a more elongate cen-
trum and a shallower ventral excavation. This combin-
ation of characters is present in most hadrosaurids
(Rozadilla et al.2021).
A mid-distal paratype vertebra (MPCN-PV-809) is
nearly completely preserved, lacking only its left trans-
verse process. The neural spine is sub-rectangular in
outline in lateral view and projects posterodorsally,
forming an angle of about 70. In anterior view, the
neural spine is transversely narrow and shows a slight
dorsal thickening, very different from the strongly thick-
ened condition in Bonapartesaurus (Cruzado-Caballero
& Powell 2017). Shallow fossae are present that separ-
ate the prespinal lamina and prezygapophyses. The pre-
zygapophyses are sub-quadrangular in outline in lateral
view, and do not surpass the level of the anterior surface
of the centrum. The postzygapophyses are short, with
their articular surfaces located ventral to the base of the
neural spine. Both the pre- and postzygapophyses bear
elliptical articular surfaces. The transverse process is
strongly dorsally projected. It is sub-triangular in cross
section, with a strong ventral lamina running from the
tip to the base of the transverse process and reaching
the posterodorsal corner of the centrum. This lamina is
excavated anteriorly and posteriorly. The anterior mar-
gin of the transverse process is connected with the pre-
zygapophysis by a well-developed lamina. In posterior
view, there is a deep ovoidal fossa located between the
transverse process and the postzygapophysis. The neural
canal is sub-circular in contour and relatively wide. The
centrum is slightly opisthocoelous with heart-shaped
articular surfaces. The lateral surfaces of the centrum
are gently concave and show several elliptical nutritive
foramina. The ventral surface bears a sharp ventral keel
(Fig. 9G–L).
Appendicular skeleton
Sternal plate. The sternal plate is represented by its
paddle-like anteromedial part. Its medial margin is con-
vex and the lateral margin is concave. The anteromedial
corner is prominent and the posteromedial process is
relatively short and rounded. The dorsal surface of the
plate is concave, while the ventral surface is convex
(Fig. 9G, H). The sternal plate of Kelumapusaura is
more expanded and laterally projected than in ‘K.’aus-
tralis, while the posteromedial process is rela-
tively shorter.
Scapula. The scapula is elongated with subparallel ven-
tral and dorsal margins. The proximal end is relatively
robust and separated from the scapular blade by a well-
defined neck. The coracoidal facet of the scapula is
3
Figure 9. Selected postcranial elements of Kelumapusaura machi gen. et sp. nov. Cervical vertebra (MPCN-PV-807, holotype) in A,
anterior, B, left, C, posterior and D, right views. Sacrum (MPCN-PV-807, holotype) in E, lateral and F, ventral views. Left sternal
plate in G, dorsal and H, ventral views. Mid-distal caudal vertebra (MPCN-PV-809, paratype) in I, anterior, J, posterior, K, right, L,
left and M, ventral views. Abbreviations: alp, anterolateral process; di, diapophysis; fos, fossae; lam, laminae; nc, neural canal; ns,
neural spine; pmp, posteromedial process; pos, postzygapophysis; prz, prezygapophysis; S, sacral vertebra; sas, anterior articular
surface of sacrum; spdp, supraprezygodiapophyseal fossa; sr, sacral ribs; tp, transverse process; vb, ventral buttress; vk, ventral keel.
Scale bars; A–D¼5 cm; E, F ¼10 cm; G, H ¼5 cm; I–M¼10 cm.
A new hadrosaurid from Patagonia 15
kidney-shaped in proximal view. Its dorsal margin proj-
ects dorsally with respect to the dorsal margin of the
acromion process, resulting in a lip-like prominence.
The glenoid fossa is deep and crescent-shaped in prox-
imal view. A strong ventrolateral process partially enc-
loses the glenoid fossa in lateral view. The acromial
process is prominent and represented by a lamina that
projects laterally. In dorsal view it has a gently sig-
moidal outline. A groove runs dorsally from the base of
the acromion to the point of maximum dorsal curvature
of the scapular blade. This groove becomes shallower
and narrower posteriorly. Ventral to the acromion pro-
cess there is a wide, deep deltoid fossa. In anterior
view, the acromion process is ventrally deflected.
Posterior to the acromion process, the lateral surface of
the scapula has a shallow deltoid ridge. The scapular
neck is notably narrow, being 50% of the dorsoventral
depth of the proximal end of the element, differing from
the poorly defined scapular neck present in
Secernosaurus and ‘K.’australis (Prieto-M
arquez &
Salinas 2010). The lateral surface of the scapular blade
is dorsoventrally convex, while its medial surface is flat
(Fig. 10A–E). As indicated above, the dorsal and ventral
margins of the scapular blade are heavily weathered, but
it does not show the strong bending present in
Secernosaurus,‘K.’australis and Gryposaurus (Prieto-
Figure 10. Selected postcranial elements of Kelumapusaura machi gen. et sp. nov. Right scapula (MPCN-PV-810, paratype) in A,
lateral, B, dorsal, C, medial, D, ventral and E, proximal views. Left ilium (MPCN-PV-811, paratype) in F, lateral, G, medial, H,
posterior, I, dorsal and J, ventral views. Right ischium (MPCN-PV-812, paratype) in K, lateral, L, medial, M, dorsal, N, posterior
and O, distal views. Abbreviations: ac, acetabulum; acr, acromion process; ar, anterior ridge; cf, coracoidal facet; df, deltoid fossa;
dg, dorsal groove; gf, glenoid fossa; gp, glenoid process; ilp, iliac process; isp, ischial process; mc, medial crest; op, obturator
process; poac, postacetabular process; pocr, postacetabular ridge; pp, pubic process; prac, preacetabular process; sacp,
supraacetabular process; sb, scapular blade; sn, scapular neck. Scale bars ¼10 cm.
16 S. Rozadilla et al.
M
arquez & Salinas 2010; Prieto-M
arquez 2012); rather,
it resembles the condition of Saurolophus,
Brachylophosaurus,Zhanghenglong and Olorotitan
(Marya
nska & Osm
olska 1984; Cuthbertson & Holmes
2010; Godefroit et al.2012b; Xing et al.2014)
(Fig. 11).
Ilium. A nearly complete left ilium is preserved
(MPCN-PV-811, paratype), lacking only the anterior-
most portion of the preacetabular process. The preace-
tabular process is strongly anteroventrally oriented, but
less so than in Gryposaurus and Secernosaurus (Brett-
Surman 1979; Prieto-M
arquez 2012). The preacetabular
notch is strongly concave and is separated from the
pubic peduncle by a small bony ‘step’as in
Secernosaurus, but unlike ‘K.’australis (Brett-Surman
1979; Prieto-M
arquez & Salinas 2010) in which the pre-
acetabular notch is homogeneously concave. The central
plate of the ilium is anteroposteriorly longer than dorso-
ventrally deep. The dorsal surface of the ilium is con-
cave at the level of the supraacetabular process, as in all
hadrosaurids (Horner et al.2004). The supraacetabular
process is anteroposteriorly long, prominent and laterally
oriented. Its lateral surface is separated into two distinct
surfaces that are oriented in oblique planes, a dorsal and
a ventral one. A similar condition is observed in
Bonapartesaurus and MPCA-Pv SM39, a left ilium ori-
ginally assigned to ‘Willinikaqe salitralensis’(Cruzado
Caballero & Powell 2017) and ‘K.’australis (Prieto-
M
arquez & Salinas 2010). The anterior margin of the
supraacetabular process is represented by a ridge that
merges with the laterodorsal margin of the ilium at an
angle of approximately 45. This ridge reaches the level
of the pubic peduncle and is confluent with the base of
the preacetabular process. This contrasts with ‘K.’aus-
tralis and Bonapartesaurus in which the anterior margin
of the supraacetabular process forms a nearly straight
angle with the main axis of the iliac plate (Cruzado
Caballero & Powell 2017). In lateral view, the supraace-
tabular process is ovoid, as in Secernosaurus (Brett-
Surman 1979), differing from Bonapartesaurus and ‘K.’
australis, in which it is sub-triangular (Prieto-M
arquez
& Salinas 2010; Cruzado-Caballero & Powell 2017),
and from Gryposaurus and Saurolophus in which it is
Figure 11. Comparisons of right scapulae between selected hadrosaurids. Not to scale.
A new hadrosaurid from Patagonia 17
sub-rectangular (Marya
nska & Osm
olska 1984; Prieto-
M
arquez 2012). The supraacetabular process represents
about half of the length of the iliac plate, a condition
similar to that observed in the indeterminate hadrosaurid
MPCA-Pv SM39 (Coria 2014) and contrasting with the
anteroposteriorly long supraacetabular process of
Bonapartesaurus (Cruzado Caballero & Powell 2017).
In dorsal view, the anterior end of the supraacetabular
process tapers anteriorly as in ‘K.’australis and
Secernosaurus, whereas in Bonapartesaurus it is deeply
concave (Prieto-M
arquez & Salinas 2010; Cruzado
Caballero & Powell 2017). The pubic peduncle is par-
tially eroded and is sub-triangular in lateral view. The
ischial peduncle is represented by two separate knobs as
in other hadrosaurids. The posterior one is more dorsally
placed and is more ventrally projected than in
Secernosaurus (Brett-Surman 1979). The acetabulum is
narrower than in Bonapartesaurus and ‘K.’australis
(Bonaparte & Rugier 1987; Prieto-M
arquez & Salinas
2010; Cruzado-Caballero & Powell 2017), but wider
than in Secernosaurus (Brett-Surman 1979). The posta-
cetabular process is shorter than the iliac plate. The
postacetabular process is slightly posterodorsally ori-
ented and does not surpass the level of the dorsal mar-
gin of the preacetabular process, a condition shared with
MPCA-Pv SM39 (Coria 2014) and Secernosaurus koer-
neri (Juarez Valieri et al.2010; Brett-Surman 1979). In
Bonapartesaurus and ‘K.’australis the postacetabular
process is markedly dorsally oriented, as typically
occurs in hadrosaurids (Horner 2004; Prieto-M
arquez
2012; Cruzado Caballero & Powell 2017). The postace-
tabular process is dorsomedially twisted along its axis
so that the lateral surface is dorsolaterally facing, as
occurs in other Patagonian hadrosaurids (Prieto M
arquez
& Salinas 2010). Along the dorsal surface of the posta-
cetabular process there is a median longitudinal ridge, a
condition shared with ‘K.’australis,Secernosaurus and
the unnamed hadrosaurid MPCA-Pv SM39 (Ju
arez-
Valieri et al.2010; Prieto-M
arquez & Salinas 2010)
(Fig. 10F–J).
Ischium. A nearly complete right ischium (MPCN-PV-
811, paratype) is available. The proximal end is partially
weathered precluding the analysis of its main anatomical
characters. The iliac peduncle is dorsally projected and
dorsally tapering. The pubic peduncle is anteriorly pro-
jected; the preserved portion of the articular surface
indicates that it was concave, with its ventral margin
narrower and more anteriorly projected than the dorsal
one. The lamina connecting the two processes is gently
concave. The ischium becomes thicker at the level of
the obturator process, where it is laterally convex and
medially concave. The obturator process is roughly fan-
shaped and is poorly projected ventrally. The base of
the obturator process is constricted, forming a neck. In
anterior view, the distal end of the obturator process is
ventrolaterally oriented. The ischial shaft is almost
straight in lateral view, showing a smooth ventral curva-
ture towards its distal end. The ischial shaft is sub-tri-
angular in cross-section, with a flat medial surface that
contacts the other ischium on its distal half. This surface
is crossed by longitudinal striations. The dorsal margin
is formed by a thick and rounded crest. The distal end
of the ischium shows a lateral longitudinal crest that
becomes sharper distally. The distal end of the ischium
is slightly expanded, forming a small foot, being sub-tri-
angular in outline in lateral view and in cross-section.
The posterior end of the ischium is not expanded, in
contrast to Eolambia and some lambeosaurines, which
show a well-developed distal process (Godefroit et al.
2012b; McDonald et al.2012)(Fig. 10K–O).
Femur. A right femur with a weathered proximal end is
preserved (MPCN-PV-813, paratype). The femoral head
is dorsomedially projected and has a relatively long
neck. The greater and lesser trochanters are fused. The
greater trochanter is sub-rectangular in outline in prox-
imal view. The shaft of the bone is nearly straight and
has a sub-rectangular cross-section, which is wider
transversely than long anteroposteriorly. The fourth tro-
chanter is crescent-shaped and proximodistally long and
narrow transversely, as occurs in ‘K.’australis but dif-
fering from the robust condition in Bonapartesaurus
(Cruzado-Caballero & Powell 2017). In posterior view,
the basitrochanteric fossa is deep and well defined,
being proximodistally extensive. The distal condyles are
anteroposteriorly longer than they are high proximodis-
tally and wide transversely. The intercondylar extensor
groove is closed by the two condyles, forming a tunnel
(Horner et al.2004)(Fig. 12).
Huallasaurus gen. nov.
Diagnosis. Hadrosaurid dinosaur distinguished by the
following unique combination of characters (autapomor-
phies marked with an asterisk): maxilla having an
obliquely oriented and strongly posteriorly inclined
ectopterygoid ridge (Fig. 13D); jugal with a dorsoven-
trally low anterior process (Fig. 13E); postorbital with a
finger-like medial process that projects medially and
forms the anterior margin of the supratemporal fenestra
(Fig. 13F–H); dentary with a ventrally concave shallow
groove at the anterior margin (Fig. 13J); dentary with a
wide symphyseal region with a straight anterior margin;
‘V’-shaped nasofrontal suture where the anterior margin
of each frontal forms an anterior triangular process that
is transversely deep with an anterior surface that is
anteriorly excavated, and has an anteriorly offset ventral
18 S. Rozadilla et al.
margin(Prieto-M
arquez & Salinas 2010); postacetabu-
lar process bearing a longitudinal groove on its dorsal
surface, parallel to the dorsal crest (Fig. 13K, L).
Etymology. The generic name ‘Hualla’means ‘duck’in
the Mapudungun language.
Type and only included species. Huallasaurus australis
comb nov.
Huallasaurus australis comb. nov.
(Fig. 13)
1984 Kritosaurus australis Bonaparte, Franchi, Powell
& Sep
ulveda: 156, fig. 1.
2001 Secernosaurus australis (Bonaparte, Franchi,
Powell & Sep
ulveda 1984); Wagner: 120.
2010 Scernosaurus koerneri Brett Surman 1979; Prieto
M
arquez & Salinas: 815, figs 2–16.
Holotype. MACN-PV 2: right prefrontal, left postorbital,
a partial sacrum including four fused centra, several dis-
articulated sacral vertebrae and ribs and various middle
caudal vertebrae, left and right sternals, right coracoid
and scapula, left and right ilia, left and right ischia lack-
ing the distal half of each shaft, left and right pubes,
left femur and proximal right femur.
Paratypes. MACN-PV 142: an oral fragment of the pre-
maxilla (Fig. 13A–C), fragmentary braincase with par-
ietal, frontal and postorbital, a right frontal, right
maxilla (Fig. 13D), anterior fragment of the right jugal
(Fig. 13E), anterior regions of the dentaries (Fig. 13I, J),
subadult left dentary and a left scapula. MACN-PV 143:
Figure 12. Right femur of Kelumapusaura machi (MPCN-PV-813, paratype) in A, anterior, B, posterior, C, lateral, D, medial, E,
proximal and F, distal views. Abbreviations: ef, extensor fossa; ff, flexor fossa; fh, femoral head; ft, fourth trochanter; lc, lateral
condyle; lt, lesser trochanter; mc, medial condyle. Scale bar ¼10 cm.
A new hadrosaurid from Patagonia 19
Figure 13. Selected elements of Huallasaurus australis comb nov. (MACN RN 142). Left premaxilla in A, ventral, B, anterior and
C, posterior views. D, right maxilla in lateral view. E, right jugal in lateral view. Right postorbital in F, lateral, G, dorsal and H,
ventral views. Dentary symphysis in I, anterior and J, dorsal views. Left postacetabular process in K, dorsal and L, posterodorsal
views. Abbreviations: ap, anterior process; dc, dorsal crest; dg, dorsal ridge; eptr, ectopterygoid ridge; jap, jugal anterior process;
jp, jugal process; ml, medial lamina; mp, medial process; od, oral denticles; pd, posterior row of denticles; sacp, supraacetabular
process; scaf, articular facet for squamosal; scp, squamosal process; vc, ventral concavity. Not to scale.
20 S. Rozadilla et al.
fragmentary braincase including parts of the basioccipi-
tal, prootic and basisphenoid. MACN-PV 144: partial
skull roof and braincase including supraoccipital, par-
ietal, frontals, postorbitals and a fragment of squamosal.
MACN-PV 145: left radius and ulna, distal end of a
femur, left metatarsals II and III, and various middle
dorsal vertebrae. MACN-PV 146: right scapula, left
ilium lacking the preacetabular process, fragmentary
preacetabular process, proximal region of a left ischium.
MACN-PV 826: right sternal, proximal half of a right
scapula, left ilium lacking the pubic and ischial
peduncles, and various cervical and anterior and middle
dorsal vertebrae. MACN-PV 987: articulated series of
distal caudal vertebrae. MACN-PV 990: pedal phalanx
III-1. MACN-PV 991: fragment of left squamosal, frag-
ment of right surangular. MACN-PV 997: right tibia.
MACN-PV 998: right dentary (heavily reconstructed
with plaster).
Diagnosis. Same as for the genus, by monotypy.
Comments. Huallasaurus is known from numerous
specimens recovered from the Los Alamitos Formation
(Bonaparte et al.1984). Among those specimens,
Bonaparte & Rougier (1987) described a predentary oral
fragment (MACN-PV 142), that was later redescribed
by Prieto-M
arquez & Salinas (2010). This bone exhibits
a gently concave external surface whereas its medial
surface is crossed by denticle-like ornamentation. This
condition contrasts with most known hadrosaurid pre-
dentaries. However, an oral margin with strong denticles
and accessory medial denticles is found on the premaxil-
lae of several hadrosaurids, such as Eotrachodon,
Prosaurolophus and Edmontosaurus (Horner 1992;
Prieto-M
arquez & Salinas 2016; Xing et al.2017;
Takasaki et al.2020). In this regard, this bone is here
reinterpreted as an anterior fragment of the left premax-
illa. The specimen preserves five denticles, with the
medial-most represented by its base only. The premaxil-
lary denticles are strong and finger-shaped, and the
mesial ones are wider at the base than the distal ones.
In lateral view, the anterior margin of the bone is gently
convex and in ventral view it is anterolaterally concave.
The medial surface is rugose and bears a posterior row
of denticles, which are sub-triangular in outline and that
are separated from the anterior denticles by a deep
groove. The Huallasaurus premaxilla differs from that
of Willinakaqe in being anteriorly concave in ventral
view and in the presence of large anterior denticles and
strong posterior denticles in the former taxon. Ju
arez-
Valieri et al.(2010) considered the absence of well-
developed denticles an autapomorphy of Wilinakaqe, but
Cruzado-Caballero & Coria (2016) argued that the den-
ticles might be eroded in the latter specimen.
The postorbital of Huallasaurus bears a finger-like,
medially projecting process that forms the anterior mar-
gin of the supratemporal fenestra. This process extends
for almost 80% of this margin, being mediolaterally lon-
ger than in Gryposaurus,Brachylophosaurus and
Kelumapusaura, and represents an autapomorphic fea-
ture of Huallasaurus. Furthermore, the ilium of
Huallasaurus shows a conspicuous groove that extends
anteroposteriorly over the dorsal surface of the postace-
tabular process.
Discussion
Comparisons between Kelumapusaura and other
Allen Formation hadrosaurids
Because of their close geographical and stratigraphical
provenance, detailed comparisons between
Kelumapusaura machi and previously described hadro-
saurids from the Los Alamitos and Allen Formations
(Maastrichtian), namely Huallasaurus,Willinakaqe sali-
tralensis,Lapampasaurus cholinoi and Bonapartesaurus
rionegrensis (Ju
arez-Valieri et al.2010; Coria et al.
2012; Cruzado-Caballero & Powell 2017), are carried
out in detail below.
The holotype of Bonapartesaurus comprises the post-
cranial remains of an individual about 7 m long, repre-
senting the largest known hadrosaurid from Patagonia
(Cruzado-Caballero & Powell 2017). The larger speci-
men of Kelumapusaura (MPCN-PV-808) could have
reached a comparable size. Kelumapusaura differs from
Bonapartesaurus in having transversely compressed
neural spines and in lacking the strong transversely
thickened caudal neural spines unique to the latter
(Powell 1987; Cruzado-Caballero & Powell 2017). The
ilium of Kelumapusaura is more lightly built than that
of Bonapartesaurus and shows a dorsoventrally low pre-
acetabular processes. Both taxa have a supraacetabular
process with a trapezoidal outline when viewed dorsally,
a condition that distinguishes them from other
Patagonian hadrosaurids. However, the supraacetabular
process in Kelumapusaura is dorsoventrally lower and
less prominent than in Bonapartesaurus. Further, the
supraacetabular process of Kelumapusaura, in contrast
to Bonapartesaurus, is not anteriorly delimited by a
strong concavity. In Kelumapusaura the postacetabular
process is dorsoventrally low and transversely narrow,
differing from the robust condition observed in
Bonapartesaurus (Cruzado-Caballero & Powell 2017).
Lapampasaurus cholinoi is a small, incompletely
known hadrosaurid that has few overlapping bones with
Kelumapusaura (Coria et al.2012). However,
Kelumapusaura differs from Lapampasaurus in lacking
A new hadrosaurid from Patagonia 21
foramina dorsal to the diapophyses on the cervical verte-
brae, in having proportionally higher sacral centra, and
in possessing a scapula with a thick deltoid crest (which
is notably sharp in Lapampasaurus; Coria et al.2012).
Willinakaqe salitralensis is based on an isolated, frag-
mentary premaxilla (Ju
arez-Valieri et al.2010), so com-
parisons between this taxon and Kelumapusaura are not
possible. Because of the incomplete nature of the
Willinakaqe salitralensis holotype, its validity has been
questioned (Coria 2014; Cruzado-Caballero & Coria
2016). In the original description of Willinakaqe,
Ju
arez-Valieri et al.(2010) assigned all hadrosaurid
material coming from different localities within the
Allen Formation to this taxon. Subsequent analysis of
the Willinakaqe salitralensis hypodigm and referred
materials indicate that it likely includes more than one
hadrosaurid taxon (Coria 2012,2014,2016; Cruzado-
Caballero & Coria 2016; Cruzado-Caballero & Powell
2017). In this regard, Coria et al.(2014) erected
Lapampasaurus cholinoi and Cruzado-Caballero &
Powell (2017) named Bonapartesaurus rionegrensis
based on materials originally referred to Willinakaqe by
Ju
arez-Valieri et al.(2010). In addition, because
Willinakaqe is based on an isolated premaxilla, many
elements previously referred to it might represent other
taxa. However, some of the materials originally referred
by Ju
arez-Valieri et al.(2010)toWillinakaqe are here
compared with Kelumapusaura.
Some isolated maxillae from the Salitral Moreno site
(MPCA-SM-12; MPCA-SM-90) assigned by Ju
arez-
Valieri et al.(2010)toWillinakaqe are similar to the
maxilla of Kelumapusaura in the presence of a stout
ridge-like posterodorsal margin, a feature also shared
with Huallasaurus. Additionally, MPCA-SM-90 shows
an extensive and subhorizontal ectopterygoid shelf, and
the medial surface of the bone dorsal to the longitudinal
row of foramina is dorsoventrally low, features consid-
ered here to be autapomorphies of Kelumapusaura. On
the basis of the shared features, it is possible that these
maxillae belong to Kelumapusaura.
Among the cranial remains originally referred to
Willinakaqe by Ju
arez-Valieri et al.(2010) there are
several dentaries (MPCA-Pv-SM3; MPCA-Pv-SM4;
MPCA-Pv-SM7), showing notable morphological vari-
ability, which may indicate the existence of more than
one taxon (Cruzado-Caballero & Coria 2016). All of
these dentaries differ from that of Kelumapusaura in the
absence of a deep crescent-shaped lateral concavity at
the anterior end of the dentary and in the morphology
of the symphyseal region, which lacks the autapomor-
phic features of Kelumapusaura.
Scapulae MPCA-SM-2/MPCA-SM-1971 differ from
that of Kelumapusaura in having a dorsoventrally wider
and ventrally deflected scapular blade and a poorly
defined scapular neck (Coria 2009;Ju
arez-Valieri et al.
2010). In this regard, specimen MPCA-SM-2/MPCA-
SM-1971 is more similar to Huallasaurus and
Secernosaurus koerneri (Bonaparte & Rougier 1987;
Prieto-M
arquez & Salinas 2010) than to
Kelumapusaura.
The ilium MPCA-Pv SM39, originally referred as to
Willinikaqe (Cruzado-Caballero & Powell 2017), shares
with other Patagonian hadrosaurids, including
Kelumapusaura, a long and anteroventrally oriented pre-
acetabular process, a preacetabular notch with a horizon-
tal bony step (absent in Huallasaurus), and a dorsally
oriented and twisted postacetabular process. In contrast
to Kelumapusaura, MPCA-Pv SM39 shows a sub-tri-
angular supraacetabular process in lateral view, with a
slightly lateroventrally oriented lateral surface, as occurs
in Huallasaurus and Bonapartesaurus (Cruzado-
Caballero & Powell 2017). In Kelumapusaura the supra-
acetabular process is elliptical in contour, and its apex is
entirely laterally oriented. The postacetabular process of
MPCA-Pv SM39 has its dorsal apex more posteriorly
positioned than in Kelumapusaura (Fig. 10). Thus, in
spite of their similarities, the differences enumerated
above suggest that MPCA-Pv SM39 does not belong to
Kelumapusaura. It is worth mentioning that the ilium
exhibits strong intraspecific variation among hadrosaurid
species (see Brett-Surman & Wagner 2006), and that
such differences might not be taxonomically important.
Kelumapusaura is very similar to Huallasaurus in
several features of its cranial and postcranial skeleton,
particularly with respect to the postorbital and maxilla,
as well as the ilium. In spite of these similarities, sev-
eral features clearly distinguish them. For example, the
postorbital of Huallasaurus has a unique medial process
that is absent in Kelumapusaura. The part of the maxilla
anterior to the jugal facet in Kelumapusaura is antero-
posteriorly longer than in Huallasaurus. The prefrontal
of Kelumapusaura is more robust than in Huallasaurus,
shows a deeper indentation on the orbital margin and
possesses several additional foramina, whereas in
Huallasaurus this bone has a single foramen on its dor-
sal surface. Strong differences between the two taxa are
noted in the dentary, especially in the symphyseal
region, which is shovel-shaped in Huallasaurus and
very different from the narrower, more complex morph-
ology in Kelumapusaura. The scapulae in the two taxa
are also very different: Kelumapusaura has a relatively
narrower scapula with a nearly straight scapular blade
and well-defined neck, in contrast to the robust and
strongly arched condition seen in Huallasaurus
(Bonaparte & Rougier 1987). In spite of the strong simi-
larities in the ilia of Kelumapusaura and Huallasaurus,
22 S. Rozadilla et al.
the ilium of the former shows a small bony step separat-
ing the pubic peduncle from the preacetabular notch that
is absent in the latter.
In summary, the Allen Formation of northern
Patagonia contains at least three well-defined taxa,
namely Lapampasaurus cholinoi,Bonapartesaurus rio-
negrensis and Kelumapusaura machi, and some indeter-
minate hadrosaurids that were originally included in the
material referred to ‘Willinakaqe salitralensis’, the val-
idity of which is still in doubt.
Are ‘Kritosaurus’australis and Secernosaurus
koerneri synonyms?
Secernosaurus koerneri was the first named hadrosaurid
from the Southern Hemisphere. It was described by
Brett-Surman (1979) on the basis of an incomplete
braincase and postcranial bones belonging to a relatively
small-sized hadrosaurid, about 5 m long. The specimen
comes from Campanian–Maastrichtian beds in Chubut
Province, central Patagonia. Bonaparte et al.(1984)
described ‘Kritosaurus’australis on the basis of several
specimens from the Campanian–Maastrichtian Los
Alamitos Formation of northern Patagonia. The speci-
mens include valuable anatomical information and most
bones are represented by multiple individuals. Bonaparte
(1996) compared ‘Kritosaurus’australis with
Secernosaurus and noted important differences in ilium
shape. Wagner (2001), in an unpublished MSc thesis,
indicated that Secernosaurus koerneri and ‘Kritosaurus’
australis were phylogenetically close to each other,
coining the combination Secernosaurus australis for the
latter. Horner et al. 2004 called attention to the features
recognized by Bonaparte et al.(1984) in assigning
‘Kritosaurus’australis to Kritosaurus, noting that these
features are widespread among hadrosaurids, and thus
questioned whether this species could be assigned to
this genus. More recently, Prieto-M
arquez & Salinas
(2010) synonymized ‘Kritosaurus’australis with
Secernosaurus koerneri, claiming that the main differen-
ces between these taxa (those present on ilium and
pubis) were the result of taphonomic deformation. They
regarded the holotype of Secernosaurus koerneri as a
subadult or juvenile individual, while specimens
assigned to ‘Kritosaurus’australis mostly represent
adults (see Coria 2016). However, Coria (2014,2016)
queried whether these differences were the result of
deformation, supporting the suggestion that these taxa
are distinct.
A detailed comparison between the holotype speci-
mens of ‘Kritosaurus’australis and Secernosaurus koer-
neri (FMNH P13423) demonstrates several differences,
including features previously noted by Brett-Surman
(1979), Bonaparte (1996) and Coria (2016). First, the
postacetabular process is notably elongate and narrow
(both dorsoventrally and transversely) in Secernosaurus,
resembling Edmontosaurus annectens and
Kundurosaurus (Godefroit et al.2012a), but different
from ‘K.’australis and other Patagonian taxa that have
deeper processes. Additionally, the postacetabular pro-
cess of ‘K.’australis has a longitudinal groove on its
dorsal surface, parallel to the dorsal crest, a derived
character that is not present in Secernosaurus koerneri
or any other Patagonian taxon. The posterior lobe of the
ischial pedicle is notably lower in Secernosaurus koer-
neri compared with ‘K.’australis and Bonapartesaurus.
Furthermore, the scapula of Secernosaurus koerneri has
a marked scapular neck and a longitudinally shorter
scapular blade, compared with both ‘K.’australis and
Kelumapusaura.
We follow the criteria of Bonaparte (1996) and Coria
(2014,2016) in regarding Secernosaurus koerneri as
different from ‘K.’australis and other Patagonian hadro-
saurids. Furthermore, we concur with Horner et al.
(2004) and Coria (2014,2016) that ‘K.’australis does
not belong to Kritosaurus, as supported by our phylo-
genetic analysis. Hence, we coin the new genus
Huallasaurus for ‘Kritosaurus’australis, to distinguish
it from Secernosaurus and Kritosaurus.
Phylogenetic analysis
Methods. The phylogenetic analysis was conducted on
a modified version of the data matrix of Takasaki et al.
(2020), using TNT v. 1.564 (Goloboff et al.2008), with
Ouranosaurus nigeriensis as the outgroup. We added
three taxa (Kelumapusaura machi,Bonapartesaurus rio-
negrensis and Huallasaurus australis) and coded
Huallasaurus australis and Secernosaurus koerneri as
separate species. Five new characters were added to the
data matrix (characters 355–359; see Supplemental
material). Character 181 was rewritten, including a
modified state 2 and adding a new third (3) state (see
Supplemental material). The data matrix consists of 74
operational taxonomic units and 359 characters (see
Supplemental material). All characters were treated as
equally weighted and unordered. The maximum number
of trees was set to 10,000 in memory. A traditional
New Technology search was carried out with 10,000
replicates of Wagner trees, followed by the Three
Bisection Reconnection (TBR) branch swapping that
held 100 random addition sequences after each search.
One hundred trees were saved after each iteration. With
the aim of testing branch support, Bremer values were
calculated. The Patagonian clade has low Bremer sup-
port (2), so the strength of this relationship is weak.
A new hadrosaurid from Patagonia 23
Results. The phylogenetic analysis resulted in the recov-
ery of 144 most parsimonious trees with lengths of
1235 steps, a consistency index of 0.417 and a retention
index of 0.830 (see the strict consensus of these in
Fig. 14).
A monophyletic clade of South American hadrosaur-
ids. The phylogenetic position of Patagonian hadrosaur-
ids is far from well known. Patagonian hadrosaurids
have been considered members of the Kritosaurus lin-
eage since the original description of Huallasaurus aus-
tralis by Bonaparte et al.(1984), an interpretation
followed by several other authors (Ju
arez-Valieri et al.
2010; Apestegu
ıaet al.2012; Coria et al.2013; Coria
2014,2016; Ibiricu et al.2021), who proposed, follow-
ing Casamiquela (1964), that these dinosaurs arrived
from North America in the latest Cretaceous.
Bonapartesarus was considered a lambeosaurine in a
Figure 14. A, strict consensus tree recovering the Patagonian hadrosaurids forming a clade as the sister taxon of North American
Kritosaurini. B, Bremer support values for Hadrosauridae. Abbreviations: HMORPHA, Hadrosauromorpha; HOIDEA,
Hadrosauroidea; P, Patagonian clade.
24 S. Rozadilla et al.
preliminary work by Powell (1987) but later re-assessed
as a saurolophinine by Cruzado-Caballero & Powell
(2017). Conversely, Coria (2009) indicated that all
Patagonian hadrosaurids might be basal members of
Lambeosaurinae. Furthermore, Salinas & Ju
arez-Valieri
(2004), Agnol
ınet al.(2010) and Rozadilla et al.(2021)
proposed that Patagonian hadrosaurids may be represen-
tatives of an endemic Gondwanan radiation.
Our phylogenetic analysis recovers the Patagonian taxa
Kelumapusaura,Huallasaurus,Bonapartesaurus and
Secernosaurus in a clade within Kritosaurini (Fig. 14), fol-
lowing the traditional idea of Bonaparte et al. (1984). This
arrangement is supported by three cranial synapomorphies:
angle of about 56–74between the anteroventral surface
of the anterior end and the dorsal surface of the lateral
process of the predentary in lateral view (ch. 27-1); angle
between the edentulous slope of the dentary anterior por-
tion and the horizontal portion <150(ch. 39-0); and
angle between the dorsal margin of the maxillary antero-
ventral process and the ventral margin of the maxillary
anterior portion where the dental battery occurs greater
than 40(ch. 98-2). However, these features show a com-
plex distribution among hadrosaurids and are widespread
in different lineages of duck-billed dinosaurs. Furthermore,
these cranial features can be scored only in
Kelumapusaura and Huallasaurus and are unknown in
Bonapartesaurus and Secernosaurus. For these reasons,
we recognize that the positions of Patagonian hadrosaurids
are far from certain, as also shown by the low Bremer
support for the clade.
This Patagonian clade is also supported by three iliac
features, namely: presence of a subhorizontal ridge sepa-
rating the preacetabular notch from the pubic pedicle
(ch. 358-1); a twisted distal end of the postacetabular
process (ch. 359-1); and a longitudinal ridge running
along the dorsal surface of the postacetabular process
(ch. 362-1). The latter two features were considered
autapomorphies of Secernosaurus koerneri by Prieto-
M
arquez & Salinas (2010), but we found both to be
widespread among Patagonian taxa.
The presence of a bony ridge separating the preace-
tabular notch and the pubic pedicle is documented for
the first time among hadrosaurids. The morphology of
the preacetabular notch is variable among hadrosaurids
(Brett-Surman 1979); however, only in Patagonian taxa
is the preacetabular notch interrupted by a bony step at
the base of the pubic pedicle.
The presence of a longitudinal ridge extending along
the dorsal surface of the postacetabular process (ch.
360-1) is a feature shared by all Patagonian specimens
(Huallasaurus,Kelumapusaura,Bonapartesaurus,
Secernosaurus, MPCA-Pv SM39) and an unnamed
hadrosaurid from the Campanian of Big Bend National
Park, USA (Davis 1983;Ju
arez-Valieri et al.2010;
Prieto-M
arquez & Salinas 2010).
The presence of a twisted distal end of the postace-
tabular process (char. 359-1), resembling a brevis shelf,
was identified by Prieto-M
arquez & Salinas (2010)as
an autapomorphic character of Secernosaurus koerneri,
although these authors mention it is also present in
specimens referred to ‘Willinakaqe’(MPCA-Pv SM39).
Later, Cruzado-Caballero & Powell (2017) considered
this trait diagnostic of Bonapartesaurus. Among ornitho-
pods, a morphology similar to a brevis shelf is conver-
gently present in some basal forms (e.g. Iguanodon;
Norman 2004) and in derived lambeosaurines such as
Hypacrosaurus (Prieto-M
arquez & Salinas 2010).
In addition to the above-mentioned characters derived
from the phylogenetic analysis, Patagonian hadrosaurids
share several additional features that may support the
monophyly of the clade. In Huallasaurus and
Kelumapusaura the postorbital is notably stout and
shows a nearly flat dorsal margin, a globose central sub-
triangular surface, and short jugal and squamosal proc-
esses. In other hadrosaurids the postorbital is relatively
slender and shows more elongate jugal and squamosal
processes (e.g. Lambeosaurus,Tlatolophus,
Prosaurolophus,Gryposaurus,Brachylophosaurus;
Horner 1992, Horner et al.2004; Evans & Reisz 2007;
Cuthberson & Holmes 2010; Prieto-M
arquez 2010b;
Velasco et al.2021). In Edmontosaurus (Xing et al.
2017) the postorbital shows a massive central region,
but it differs from the Patagonian hadrosaurids in the
presence of a well-developed squamosal process.
The prepubic process of the pubis is remarkable in
Huallasaurus, with a sub-trapezoidal outline in lateral
view. This differs from the ovoidal or sub-circular shape
seen in Laurasian hadrosaurids (Horner et al. 2004). The
known specimens of Secernosaurus have an incomplete
prepubic process that lacks its anterior-most end. In spite
of this, the preserved portion indicates a shape similar to
that of Huallasaurus, which may be characteristic of
southern hadrosaurids.
The possible recognition of a clade of South
American hadrosaurids might indicate that these dino-
saurs had a more complex evolutionary history in the
southern continents than previously thought. Patagonian
hadrosaurids had their own history and particular evolu-
tion in South America, which remains a nearly unknown
chapter on dinosaur evolution.
Conclusions
The discovery of a new species of hadrosaurid ornithis-
chian, based on cranial and postcranial remains from the
A new hadrosaurid from Patagonia 25
Allen Formation, sheds new light on the evolution of
duck-billed dinosaurs in southern South America. The
new hadrosaurid is very similar to other taxa described
from coeval beds, including Secernosaurus,
Bonapartesaurus,Lapampasaurus and Huallasaurus.
Anatomical comparisons between the available hadro-
saurid remains indicate that more than three species
inhabited northern Patagonia at roughly the same time.
Phylogenetic analysis recognizes Kelumapusaura,
Huallasaurus,Bonapartesaurus and Secernosaurus as
members of a Patagonian hadrosaurid clade. These
results also imply that the species ‘Kritosaurus’austra-
lis should be assigned to a new genus. More import-
antly, it indicates that the history of duck-billed
dinosaurs is far from resolved. These records, far from
Laurasia, show that hadrosaurids were not just vagrants
and scarcely present, but instead were members of an
independent radiation that took place in this region of
Gondwana and formed a key part of the latest
Cretaceous faunas of Patagonia.
Supplemental material
Supplemental material for this article can be accessed
here: http://doi.org/10.1080/14772019.2021.2020917.
Acknowledgements
We sincerely thank the crew of the Laboratorio de
Anatom
ıa Comparada y Evoluci
on de los Vertebrados
(LACEV), especially Julia D’Angelo, Ana P. Moreno,
Marcelo P. Isasi, Gonzalo L. Mu~
noz, Gabriel Lio and
Adriel R. Gentil, for their hard work on the field trip
where the Kelumapusaura specimens were recovered.
We thank Santiago Miner for scanning and 3D
modelling the material. Special thanks to the Arriagada
family for their support and help in the field. We thank
Pablo Chafrat, Franco Migliaro and all the staff of the
Museo Patag
onico de Ciencias Naturales (General Roca
City) for giving us valuable help during our expeditions.
Special thanks to Agust
ın Martinelli and Mart
ın Ezcurra
for access to the Huallasaurus australis specimens.
Thanks to Penelope Cruzado-Caballero for discussion
about hadrosaurids and the identification of some of the
material here described. This project was supported by
the National Geographic Society (grant number
CP050ER17 to AAMR) and by KUNDRAT (to FEN)
and ANPCyT (to FEN). We thank Richard Butler, Paul
Barrett, Phil Bell and an anonymous reviewer who
provided valuable comments that notably improved the
quality of the manuscript.
References
Agnol
ın, F. L.,Ezcurra, M. D.,Pais, D. F. &Salisbury,
S. W. 2010. A reappraisal of the Cretaceous non-avian
dinosaur faunas from Australia and New Zealand:
evidence for their Gondwanan affinities. Journal of
Systematic Palaeontology,8(2), 257–300.
Apestegu
ıa, S., Cambiaso, A. &Agnol
ın, F. L. 2012.
Vertebrados de la Formaci
on Paso del Sapo (Campaniano/
Maastrichtiano), Provincia de Chubut, Argentina.
Ameghiniana,49(3), 395–400.
Aranciaga-Rolando, M. A.,Mars
a, J. A. G.,Agnol
ın, F. L.,
Motta, M. J.,Rozadilla, S. &Novas, F. E. 2022. The
sauropod record of salitral ojo del agua: An Upper
Cretaceous (Allen Formation) fossiliferous locality from
northern Patagonia, Argentina. Cretaceous Research,129,
105029. doi:10.1016/j.cretres.2021.105029
Bell, P. R. 2011. Cranial osteology and ontogeny of
Saurolophus angustirostris from the Late Cretaceous of
Mongolia with comments on Saurolophus osborni from
Canada. Acta Palaeontologica Polonica,56(4), 703–722.
Bertozzo, F.,Dal Sasso, C.,Fabbri, M.,Manucco, F. &
Maganuco, S. 2017. Redescription of a remarkably large
Gryposaurus notabilis (Dinosauria: Hadrosauridae) from
Alberta, Canada. Societa Italiana di Scienze Naturali e
Museo Civico di Storia Naturale,43,1–56.
Bonaparte, J. F. 1996. Cretaceous Tetrapods of Argentina.
M€
unchner Geowissenschaftliche Abhandlungen,30A,
73–130.
Bonaparte, J. F., Franchi, M. R., Powell, J. E. &
Sep
ulveda, E. G. 1984. La Formaci
on Los Alamitos
(Campaniano–Maastrichtiano) del sudeste de R
ıo Negro,
con descripci
on de Kritosaurus australis n. sp.
(Hadrosauridae). Significado paleogeogr
afico de los
vertebrados. Revista de la Asociaci
on Geol
ogica
Argentina,39(3&4), 284–299.
Bonaparte, J. F. &Rougier, G. 1987. The Late Cretaceous
fauna of Los Alamitos, Patagonia, Argentina. VII: The
hadrosaurs. Revista del Museo Argentino de Ciencias
Naturales Bernardino Rivadavia e Instituto Nacional de
Investigaci
on de las Ciencias Naturales. Paleontolog
ıa,
3(3), 155–161.
Brett-Surman, M. K. 1979. Phylogeny and
paleobiogeography of hadrosaurian dinosaurs. Nature,277,
560–562.
Brett-Surman, M. K. &Wagner, J. R. 2006. Discussion of
character analysis of the appendicular anatomy in
Campanian and Maastrichtian North American
hadrosaurids –Variation and ontogeny. Pp. 135–169 in
Kenneth Carpenter (ed.), Horns and Beaks - Ceratopsian
and Ornithopod Dinosaurs. Indiana University Press,
Bloomington, Indiana.
Brown, B. 1914. Corythosaurus casuarius, a new crested
dinosaur from the Belly River Cretaceous, with
provisional classification of the family Trachodontidae.
Bulletin of the American Museum of Natural History,33,
559–565.
Casad
ıo, S. 1994. Estratigraf
ıa y paleontolog
ıa del intervalo
Maastrichtiano–Daniano en el occidente de la provincia
de La Pampa, Argentina. Unpublished PhD thesis,
Universidad Nacional de C
ordoba, C
ordoba, 420 pp.
Casamiquela, R. M. 1964. Sobre un dinosaurio hadrosaurido
de la Argentina. Ameghiniana,3(9), 285–312.
26 S. Rozadilla et al.
Case, J. A.,Martin, J. E.,Chaney, D. S.,Reguero, M.,
Marenssi, S. A.,Santillana, S. M. &Woodburne, M. O.
2000. The first duck-billed dinosaur (Family
Hadrosauridae) from Antarctica. Journal of Vertebrate
Paleontology,20(3), 612–614.
Cope, E. D. 1869. Remarks on Holops brevispinus,
Ornithotarsus immanis, and Macrosaurus proriger.
Proceedings of the Academy of Natural Sciences of
Philadelphia,21, 123.
Coria, R. A. 2009. Osteolog
ıa, filogenia y evoluci
on de los
Hadrosauridae (Dinosauria: Ornithischia, Ornithopoda)
de la Patagonia, Argentina. PhD. Universidad Nacional de
Lujan, Lujan, Provincia de Buenos Aires, 421p.
Coria, R. A. 2013. South American hadrosaurids. The gentle
geodispersal. Pp. 31–39 in P. Huerta Hurtado & F.
Torcida Fernandez-Baldor (eds) Actas de las IV jornadas
internacionales sobre Paleontologıa de Dinosaurios y su
entorno. Colectivo Arqueologico y Paleontologico de
Salas. Salas de los Infantes, Burgos.
Coria, R. A. 2014. South American hadrosaurs: considerations
on their diversity. Pp 332–339 in D. A. Eberth & D. C.
Evans (eds) Hadrosaurs. Indiana University Press,
Bloomington and Indianapolis.
Coria, R. A. 2016. An overview of the ornithischian
dinosaurs from Argentina. Contribuciones del MACN,6,
109–117.
Coria, R. A., Gonzalez-Riga, B. &Casad
ıo, S. 2012. Un
nuevo hadros
aurido (Dinosauria, Ornithopoda) de la
Formaci
on Allen, provincia de La Pampa, Argentina.
Ameghiniana,49(4), 552–572.
Cruzado-Caballero, P. &Coria, R. A. 2016. Revisiting the
hadrosaurid (Dinosauria: Ornithopoda) diversity of the
Allen Formation: a re-evaluation of Willinakaqe
salitralensis from salitral Moreno, R
ıo Negro province,
Argentina. Ameghiniana,53(2), 231–237.
Cruzado-Caballero, P. &Powell, J. 2017. Bonapartesaurus
rionegrensis, a new hadrosaurine dinosaur from South
America: implications for phylogenetic and biogeographic
relations with North America. Journal of Vertebrate
Paleontology,37(2), e1289381. doi:10.1080/02724634.
2017.1289381
Cuthbertson, R. S. &Holmes, R. B. 2010. The first
complete description of the holotype of
Brachylophosaurus canadensis Sternberg, 1953
(Dinosauria: Hadrosauridae) with comments on
intraspecific variation. Zoological Journal of the Linnean
Society,159(2), 373–397.
Davis, T. L. 1983. Late Cenozoic structure and tectonic
history of the western “Big Bend”of the San Andreas
fault and adjacent San Emigdio Mountains [Ph. D. thesis]:
Santa Barbara. University of California, 579.
Evans, D. C. &Reisz, R. R. 2007. Anatomy and relationships
of Lambeosaurus magnicristatus, a crested hadrosaurid
dinosaur (Ornithischia) from the Dinosaur Park Formation,
Alberta. Journal of Vertebrate Paleontology,27(2),
373–393.
Ezcurra, M. D. &Agnol
ın, F. L. 2012. A new global
palaeobiogeographical model for the late Mesozoic and
early Tertiary. Systematic Biology,61(4), 553–566.
Freedman Fowler, E. A. &Horner, J. R. 2015. A new
brachylophosaurin hadrosaur (Dinosauria: Ornithischia)
with an intermediate nasal crest from the Campanian
Judith River Formation of northcentral Montana. PLoS
ONE,10(11), e0141304. doi:10.1371/journal.pone.0141304
Garrido, A. 2010. Estratigraf
ıa del Grupo Neuqu
en, Cret
acico
Superior de la Cuenca Neuquina (Argentina): nueva
propuesta de ordenamiento litoestratigr
afico. Revista del
Museo Argentino de Ciencias Naturales, nueva serie,
12(2), 121–177.
Gasparini, Z.,Sterli, J.,Parras, A.,O'Gorman, J. P.,
Salgado, L.,Varela, J. &Pol, D. 2015. Late Cretaceous
reptilian biota of the La Colonia Formation, central
Patagonia, Argentina: occurrences, preservation and
paleoenvironments. Cretaceous Research,54, 154–168.
doi:10.1016/j.cretres.2014.11.010
Gates, T. A. &Sampson, S. D. 2007. A new species of
Gryposaurus (Dinosauria: Hadrosauridae) from the late
Campanian Kaiparowits Formation, southern Utah, USA.
Zoological Journal of the Linnean Society,151(2),
351–376.
Gates, T. A.,Horner, J. R.,Hanna, R. R. &Nelson, C. R.
2011. New unadorned hadrosaurine hadrosaurid
(Dinosauria, Ornithopoda) from the Campanian of North
America. Journal of Vertebrate Paleontology,31(4),
798–811.
Godefroit, P.,Bolotsky, Y. L. &Lauters, P. 2012a. A new
saurolophine dinosaur from the latest Cretaceous of far
Eastern Russia. PLoS ONE,7(5), e36849. doi:10.1371/
journal.pone.0036849
Godefroit, P.,Bolotsky, Y. L. &Bolotsky, I. Y. 2012b.
Osteology and relationships of Olorotitan arharensis,a
hollow-crested hadrosaurid dinosaur from the latest
Cretaceous of Far Eastern Russia. Acta Palaeontologica
Polonica,57(3), 527–560.
Goloboff, P. A.,Farris, J. S. &Nixon, K. C. 2008. TNT, a
free program for phylogenetic analysis. Cladistics,24(5),
774–786.
Heaton, M. J. 1972. The palatal structure of some Canadian
Hadrosauridae (Reptilia: Ornithischia). Canadian Journal
of Earth Sciences,9(2), 185–205.
Horner, J. R. 1992. Cranial morphology of Prosaurolophus
(Ornithischia: Hadrosauridae): with descriptions of two
new hadrosaurid species and an evaluation of hadrosaurid
phylogenetic relationships. Museum of the Rockies
Occasional Paper,2,1–119.
Horner, J. R., Weishampel, D. B. &Forster, C. A. 2004.
Hadrosauridae. Pp. 438–463 in D. B. Weishampel, P.
Dodson & H. Osm
olska (eds) The Dinosauria. Second
edition. University of California Press, Berkeley.
Ibiricu, L. M., Casal, G. A., Alvarez, B. N., Tomas,
A. D. S., Lamanna, M. C. &Cruzado-Caballero, P.
2021. New hadrosaurid (Dinosauria: Ornithopoda) fossils
from the uppermost Cretaceous of central Patagonia and
the influence of paleoenvironment on South American
hadrosaur distribution. Journal of South American Earth
Sciences 10, 103369. doi:10.1016/j.cretres.2017.07.022
Ju
arez-Valieri, R.,Haro, J.,Fiorelli, L. &Calvo, J. 2010.
A new hadrosauroid (Dinosauria: Ornithopoda) from the
Allen Formation (Late Cretaceous) of Patagonia,
Argentina. Revista del Museo Argentino de Ciencias
Naturales, nueva serie,12(2), 217–231.
Lapparent, A. F. &Lavocat, R. 1955. Dinosauriens. Pp.
785–962 in J. Piveteau (ed.) Trait
e de Pal
eontologie,
Tome 5. Masson Cie Editeurs Paris.
Longrich, N. R.,Pereda Suberbiola, X.,Pyron, R. A. &
Jalil, N. E. 2021. The first duckbill dinosaur
(Hadrosauridae: Lambeosaurinae) from Africa and the role
A new hadrosaurid from Patagonia 27
of oceanic dispersal in dinosaur biogeography. Cretaceous
Research,120, 104678. doi:10.1016/j.cretres.2020.104678
Lowi-Merri, T. M. &Evans, D. C. 2020. Cranial variation in
Gryposaurus and biostratigraphy of hadrosaurines
(Ornithischia: Hadrosauridae) from the Dinosaur Park
Formation of Alberta, Canada. Canadian Journal of Earth
Sciences,57(6), 765–779. doi:10.1139/cjes-2019-0073
Lull, R. S. &Wright, N. E. 1942. Hadrosaurian dinosaurs of
North America. Geological Society of America Special
Papers,40,1–242.
Lund, E. K. &Gates, T. A. 2006. A historical and
biogeographical examination of hadrosaurian dinosaurs.
New Mexico Museum of Natural History Science, Bulletin,
35, 263–276.
Marsh, O. C. 1881. Principal characters of American Jurassic
dinosaurs. Part IV. American Journal of Science,21,
417–423.
Martinelli, A. &Forasiepi, A. 2004. Late Cretaceous
vertebrates from Bajo de Santa Rosa (Allen Formation),
R
ıo Negro Province, Argentina, with the description of a
new sauropod dinosaur (Titanosauridae). Revista del
Museo Argentino de Ciencias Naturales, nueva serie,6(2),
257–305.
Marya
nska, T. &Osm
olska, H. 1981. Cranial anatomy of
Saurolophus angustirostris with comments on the Asian
Hadrosauridae (Dinosauria). Palaeontologia Polonica,42,
5–24.
Marya
nska, T. &Osm
olska, H. 1984. Postcranial anatomy
of Saurolophus angustirostris with comments on other
hadrosaurs. Palaeontologia Polonica,46, 119–141.
McDonald, A. T.,Bird, J.,Kirkland, J. I. &Dodson, P.
2012. Osteology of the basal hadrosauroid Eolambia
caroljonesa (Dinosauria: Ornithopoda) from the Cedar
Mountain Formation of Utah. PLoS ONE,7(10), e45712.
doi:10.1371/journal.pone.0045712
Norman, D. B. 2004. 19. Basal Iguanodontia. Pp. pp.
413–437 in The Dinosauria (second edition). University of
California Press, Berkeley.
Owen, R. 1842. Report on British fossil reptiles. Part II.
Reports of the British Association for the Advancement of
Science,11,60–204.
Powell, J. E. 1987. Hallazgo de un dinosaurio hadrosaurido
(Ornithischia, Ornithopoda) en la Formacion Allen
(Cretacico superior) de Salitral Moreno, Provincia de R
ıo
Negro, Argentina. Pp. 149–152 in Asociaci
on Argentina
de Geolog
ıa (eds) Actas X Congreso Geologico Argentino.
San Miguel de Tucuman, Tucuman.
Prieto-M
arquez, A. 2005. New information on the cranium of
Brachylophosaurus canadensis (Dinosauria,
Hadrosauridae), with a revision of its phylogenetic
position. Journal of Vertebrate Paleontology,25(1),
144–156. doi:10.1671/0272-4634(2005)025[0144:NIOTCO]
2.0.CO;2
Prieto-M
arquez, A. 2010a. Global historical biogeography of
hadrosaurid dinosaurs. Zoological Journal of the Linnean
Society,159(2), 503–525. doi:10.1111/j.1096-3642.2010.
00642.x
Prieto-M
arquez, A. 2010b. The braincase and skull roof of
Gryposaurus notabilis (Dinosauria, Hadrosauridae), with a
taxonomic revision of the genus. Journal of Vertebrate
Paleontology,30(3), 838–854. doi:10.1080/
02724631003762971
Prieto-M
arquez, A. 2012. The skull and appendicular
skeleton of Gryposaurus latidens, a saurolophine
hadrosaurid (Dinosauria: Ornithopoda) from the early
Campanian (Cretaceous) of Montana, USA. Canadian
Journal of Earth Sciences,49(3), 510–532. doi:10.1139/
e11-069
Prieto-M
arquez, A. &Salinas, G. C. 2010. A re-evaluation
of Secernosaurus koerneri and Kritosaurus australis
(Dinosauria, Hadrosauridae) from the Late Cretaceous of
Argentina. Journal of Vertebrate Paleontology,30(3),
813–837. doi:10.1080/02724631003763508
Prieto-M
arquez, A.,Dalla Vecchia, F. M.,Gaete, R. &
Galobart, A. 2013. Diversity, relationships, and
biogeography of the lambeosaurine dinosaurs from the
European Archipelago, with description of the new
aralosaurin Canardia garonnensis.PLoS ONE,8(7),
e69835. doi:10.1371/journal.pone.0069835
Prieto-M
arquez, A.,Erickson, G. M. &Ebersole, J. A.
2016. Anatomy and osteohistology of the basal
hadrosaurid dinosaur Eotrachodon from the uppermost
Santonian (Cretaceous) of southern Appalachia. PeerJ,4,
e1872. doi:10.7717/peerj.1872
Prieto-M
arquez, A.,Fondevilla, V.,Sell
es, A. G.,Wagner,
J. R. &Galobart,
A. 2019. Adynomosaurus arcanus,a
new lambeosaurine dinosaur from the Late Cretaceous
Ibero-Armorican Island of the European archipelago.
Cretaceous Research,96,19–37. doi:10.1016/j.cretres.
2018.12.002
Rich, T.,Vickers-Rich, P.,Fernandez, M. &Santillana, S.
1999. A probable hadrosaur from Seymour Island,
Antarctic Peninsula. National Science Museum
Monographs,15, 219–222.
Rozadilla, S.,Agnol
ın, F.,Manabe, M.,Tsuihiji, T. &
Novas, F. E. 2021. Ornithischian remains from the
Chorrillo Formation (Upper Cretaceous), southern
Patagonia, Argentina, and their implications on
ornithischian paleobiogeography in the southern
hemisphere. Cretaceous Research,125(2), 104881. doi:10.
1016/j.cretres.2021.104881
Salinas, G. C. &Juarez-Valieri, R. D. 2004. Breve
comentario acerca de los hadrosauriformes de America del
sur y sus implicancias paleobiogeograficas. Pp. 24–25 in
Anon (eds) Reunion de comunicaciones de la Asociacion
Paleontologica. Res
umenes. Diamante, Argentina.
Seeley, H. G. 1887. On the classification of the fossil animals
commonly called Dinosauria. Proceedings of the Royal
Society London,43, 165–171.
Soto-Acu~
na, S.,Jujihara, T.,Novas, F. E.,Leppe, M.,
Gonz
alez, E.,Stinnesbeck, W.,Isasi, M. P.,Rubilar-
Rogers, D. &Vargas, A. O. 2014. Hadrosaurios
(Ornithopoda: Hadrosauridae) en el Cret
acico Superior del
extremo austral de Am
erica del Sur. P. 73 in Anon (eds)
IV simposio paleontolog
ıa en Chile. Res
umenes.
Universidad Austral de Chile, Valdivia.
Sternberg, C. M. 1936. The systematic position of
Trachodon.Journal of Paleontology,10, 652–655.
Takasaki, R.,Fiorillo, A. R.,Tykoski, R. S. &Kobayashi,
Y. 2020. Re-examination of the cranial osteology of the
Arctic Alaskan hadrosaurine with implications for its
taxonomic status. PLoS ONE,15(5), 0232410. doi:10.
1371/journal.pone.0232410
Velasco, A. A. R.,Aguilar, F. J.,Hern
andez-Rivera, R.,
Mauss
an, J. L. G.,Rodr
ıguez, M. L. &Alvarado-
Ortega, J. 2021. Tlatolophus galorum, gen. et sp. nov., a
parasaurolophini dinosaur from the upper Campanian of
the Cerro del Pueblo Formation, Coahuila, northern
28 S. Rozadilla et al.
Mexico. Cretaceous Research,126, 104884. doi:10.1016/j.
cretres.2021.104884
Wagner, J. R. 2001. The hadrosaurian dinosaurs
(Ornithischia: Hadrosauria) of Big Bend National Park,
Brewster County, Texas, with implications for Late
Cretaceous Paleozoogeography. Unpublished MSc thesis,
Texas Tech University, Austin, Texas, 417 pp.
Weishampel, D. B.,Norman, D. B. &Grigorescu, D. 1993.
Telmatosaurus transsylvanicus from the Late Cretaceous
of Romania: the most basal hadrosaurid. Palaeontology,
36, 361–385.
Wilson, J. A. 2006. Anatomical nomenclature of fossil
vertebrates: standardized terms or ‘lingua franca’?Journal
of Vertebrate Paleontology,26, 511–518.
Xing, H.,Wang, D.,Han, F.,Sullivan, C.,Ma, Q.,He, Y.,
Hone, D. W. E.,Yan, R.,Du, F. &Xu, X. 2014. A new
basal hadrosauroid dinosaur (Dinosauria: Ornithopoda)
with transitional features from the Late Cretaceous of
Henan Province, China. PLoS ONE,9(6), e98821. doi:10.
1371/journal.pone.0098821
Xing, H.,Mallon, J. C. &Currie, M. L. 2017.
Supplementary cranial description of the types of
Edmontosaurus regalis (Ornithischia: Hadrosauridae), with
comments on the phylogenetics and biogeography of
Hadrosaurinae. PLoS ONE,12(4), e0175253. doi:10.1371/
journal.pone.0175253
Associate Editor: Richard Butler
A new hadrosaurid from Patagonia 29
