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A new saurolophine hadrosaurid (Dinosauria: Ornithopoda) from the Campanian of Utah, North America

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A new hadrosaurid is described from the Upper Cretaceous Neslen Formation of central Utah. Rhinorex condrupus gen. et sp. nov. is diagnosed on the basis of two unique traits, a hook-shaped projection of the nasal anteroventral process and dorsal projection of the posteroventral process of the premaxilla, and is further differentiated from other hadrosaurid species based on the morphology of the nasal (large nasal boss on the posterodorsal corner of the circumnarial fossa, small protuberences on the anterior process, absence of nasal arch), jugal (vertical postorbital process), postorbital (high degree of flexion present on posterior process), and squamosal (inclined anterolateral processes). This new taxon was discovered in estuarine sediments dated at approximately 75 Ma and just 250 km north of the prolific dinosaur-bearing strata of the Kaiparowits Formation, possibly overlapping in time with Gryposaurus monumentensis. Phylogenetic parsimony and Bayesian analyses associate this new taxon with the Gryposaurus clade, even though the type specimen does not possess the diagnostic nasal hump of the latter genus. Comparisons with phylogenetic analyses from other studies show that a current consensus exists between the general structure of the hadrosaurid evolutionary tree, but on closer examination there is little agreement among species relationships.
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A new saurolophine hadrosaurid (Dinosauria: Ornithopoda) from the Campanian
of Utah, North America
Terry A. Gates
a,b*
and Rodney Scheetz
c
a
David Clark Labs, North Carolina State University, Raleigh, NC 27695, USA;
b
North Carolina Museum of Natural Science, 11 W Jones
St., Raleigh, NC 27601;
c
BYU Museum of Paleontology, 1683 N Canyon Rd., Provo, UT 84602, USA
(Received 21 February 2013; accepted 17 June 2014)
A new hadrosaurid is described from the Upper Cretaceous Neslen Formation of central Utah. Rhinorex condrupus gen. et
sp. nov. is diagnosed on the basis of two unique traits, a hook-shaped projection of the nasal anteroventral process and
dorsal projection of the posteroventral process of the premaxilla, and is further differentiated from other hadrosaurid
species based on the morphology of the nasal (large nasal boss on the posterodorsal corner of the circumnarial fossa, small
protuberences on the anterior process, absence of nasal arch), jugal (vertical postorbital process), postorbital (high degree
of flexion present on posterior process), and squamosal (inclined anterolateral processes). This new taxon was discovered
in estuarine sediments dated at approximately 75 Ma and just 250 km north of the prolific dinosaur-bearing strata of the
Kaiparowits Formation, possibly overlapping in time with Gryposaurus monumentensis. Phylogenetic parsimony and
Bayesian analyses associate this new taxon with the Gryposaurus clade, even though the type specimen does not possess
the diagnostic nasal hump of the latter genus. Comparisons with phylogenetic analyses from other studies show that a
current consensus exists between the general structure of the hadrosaurid evolutionary tree, but on closer examination there
is little agreement among species relationships.
http://zoobank.org/urn:lsid:zoobank.org:pub:0FDD0FE6-6C20-4838-BD4A-092161179095
Keywords: Hadrosauridae; ornithopod; Cretaceous; Utah; Book Cliffs; Neslen Formation; biogeography; phylogenetics
Introduction
The Cretaceous rocks of western North America have
yielded the highest diversity of hadrosaurid dinosaurs in
the world (Horner et al.2004; Gates & Evans 2005;
Prieto-M
arquez 2010b). These megaherbivorous ornitho-
pod dinosaurs are plausibly the most common dinosaur
fossils found from the Campanian through the terminal
Cretaceous, recorded in almost every terrestrial fossilifer-
ous formation of North America. Even more remarkable
is that during the late Campanian, it appears that hadro-
saurids generally occupied relatively small geographical
ranges in the Western Interior Basin (WIB) (Gates et al.
2012).
Whereas the diversity of hadrosaurid dinosaurs has
been relatively well understood in the northern region of
the WIB for several decades, that of the southern region
has remained low until a recent acceleration in discovery
(e.g. Gates et al.2007,2011; Gates & Sampson 2007;
Wagner & Lehman 2009). This surge in identification of
new species is due in large part to the exploration of new
sedimentary formations such as the Kaiparowits and Wah-
weap formations of southern Utah (Gates et al.2013). The
Book Cliffs of central Utah (Fig. 1), likewise, are greatly
underappreciated for their fossil potential. Early in the
twentieth century, coal mines in the Book Cliffs were rec-
ognized as a repository for dinosaur tracks and have been
utilized as a rich data source since (Parker & Balsley
1989). Only two vertebrate skeletal fossil specimens have
been reported from these rocks: first, Thomson et al.
(2013) described a partial tyrannosaurid foot from the
Neslen Formation that possesses unique morphological
traits, differing from a contemporaneous species
(Carr et al.2011; Zanno et al.2013) less than 250 km
south in the Kaiparowits Formation; and secondly there is
a hadrosaurid, also from the Neslen Formation, in which
only extensive skin impressions have been the subject of
publication (Anderson et al.1999). Here we describe this
hadrosaurid specimen (BYU 13258) as a new saurolo-
phine genus, as well as discussing its biogeographical,
ecological and phylogenetic implications.
Geological and taphonomic background
The Book Cliffs of east-central Utah (Fig. 1) record an
overall regressive sequence of Late Cretaceous marine to
terrestrial rocks. Several formations have been named
within the sequence, and of these the Neslen Formation
*
Corresponding author. Email: tagates@ncsu.edu
ÓThe Trustees of the Natural History Museum, London 2014. All Rights Reserved.
Journal of Systematic Palaeontology, 2014
http://dx.doi.org/10.1080/14772019.2014.950614
has proven to be one of the most economically exploited
because of its large, laterally extensive coal beds, the
Chesterfield coal zone, which is traceable for 120 km
(Fisher et al.1960; Kirschbaum & Hettinger 2004). In
addition to coal, the formation is comprised of a full com-
plement of terrestrial to near marine siliciclastic sedi-
ments, delimited by two regional sequence boundaries
(Kirschbaum & Hettinger 2004).
Anderson et al.(1999) described the depositional envi-
ronment of BYU 13258 in detail, which corresponds to
the Facies Assemblage 2 (lenticular cross-stratified sand-
stone, tabular ripple-laminated sandstones, and inclined
heterolithic strata) of Kirschbaum & Hettinger (2004).
The former authors reported a fining upward sandstone
sequence interlaced with siltstone, abundant Teredolites
and plant debris (Anderson et al.1999) that were likely
deposited within a channel near a tidally influenced delta
(Kirschbaum & Hettinger 2004). Firmly indurated
sandstone together with a precarious ascent to the site led
excavators to remove BYU 13528 within a number of
manageable sandstone blocks air-lifted by the Utah
National Guard. Although the postcranial skeleton of
BYU 13528 has yet to be prepared, quarry maps and sand-
stone blocks suggest that the animal was mostly articu-
lated, with minor dislocation of some tails sections. The
body was found lying on its left side with neural spines
oriented into the hill. The limbs are missing from the
excavated specimen, but if they were associated prior to
burial it seems reasonable that they eroded down the steep
hillside long before its discovery.
All geological age approximations of the Neslen Forma-
tion are based on ammonite biostratigraphy from Gill &
Hail (1975) and stratigraphical correlations from Kirsch-
baum & Hettinger (2004). BYU 13528 was found approxi-
mately 12 m above the base of the Neslen Formation
(Anderson et al.1999), which falls within either the Bacu-
lites scotti or Didymoceras nebraskense ammonite zones
that Izett et al.(1998) dated to 74.5 §0.1 Ma and 74.1 §
0.1 Ma, respectively. In contrast, Cobban et al.(2006)
favoured older ages for these same biostratigraphical zones
(75.56 §0.11 Ma and 75.19 §0.28 Ma). Thomson et al.
(2013) published a recalibrated date from Izett et al.
(1998) based on recommendations from Renne et al.
(2010) to 75.15 §0.29 Ma, similar to the Cobban et al.
(2006) estimation.
Institutional abbreviations
AMNH: American Museum of Natural History, New
York, USA; BYU: Brigham Young University Museum
of Paleontology, Provo, UT, USA; CMN: Canadian
Figure 1. Map showing Book Cliffs (black fill) and approximate
position (star) of the Rhinorex condrupus gen. et sp. nov. type
locality within the state of Utah.
Figure 2. Sample of skin impressions from Rhinorex condrupus gen. et sp. nov., BYU 13528. Scale bar D15 mm.
2 T. A. Gates and R. Scheetz
Museum of Nature, Ottawa, Ontario, Canada; MOR:
Museum of the Rockies, Bozeman, MT, USA; NCSM:
North Carolina Museum of Natural Sciences, Raleigh,
NC, USA; RAM: Raymond M. Alf Museum, Claremont,
CA, USA; ROM: Royal Ontario Museum, Toronto,
Ontario, Canada; TCMI: The Children’s Museum of Indi-
anapolis, Indianapolis, IN, USA; TMP: Royal Tyrrell
Museum of Palaeontology, Drumheller, Alberta, Canada.
Systematic palaeontology
Dinosauria Owen, 1842
Ornithopoda Marsh, 1881
Hadrosauridae Cope, 1870
Saurolophinae Brown, 1914 (sensu Prieto-Marquez
2010c)
Rhinorex gen. nov.
(Figs 27)
Type species. Rhinorex condrupus sp. nov.
Diagnosis. As for type and only species.
Derivation of name. Rhino (Greek) nose; rex (Latin)
king, in reference to the large nose possessed by this taxon.
Rhinorex condrupus sp. nov.
Holotype. BYU 13258, partial, but mostly articulated
skeleton and skull. Postcranial elements include partial
pelvis and vertebral column.
Diagnosis. Species of saurolophine hadrosaurid with the
following autapomorphies: posteroventral process of pre-
maxilla possesses slight dorsal expansion on the medial
margin at approximately the midpoint; anteroventral pro-
cess of nasal resembles a fish hook being wide, triangular,
and possessing a small dorsally directed bump. Differen-
tial diagnosis: Rhinorex condrupus is also distinguished
from other hadrosaurid species by lack of lateral flaring
on the medial margin of the posteroventral process of the
premaxilla as in Gryposaurus spp.; vomer with elongated
excavation at junction of anterior and posterior processes
shared with G. monumentensis; posterodorsal margin of
the circumnarial depression gently incised and located
dorsal to the anterior half of the lacrimal as in Gryposaurus
spp.; large rugose boss on posterodorsal corner of circum-
narial fossa; small (<1 cm) bony protuberances along
anterodorsal margin of nasal, increasing in size posteriorly
(present on one specimen of Gryposaurus notabilis,
AMNH 5350); a nasal lacking a solid raised crest on the
posterior region of nasal as in Edmontosaurus spp., Acri-
stavus gagslarsoni, and a juvenile and ‘adult’ specimen of
Gryposaurus notabilis (TMP 80.22.1 and AMNH 5350,
respectively); and a jugal with a postorbital process ori-
ented perpendicular to the main jugal body as in
Kritosaurus spp. (slightly inclined posteriorly in Grypo-
saurus species except specimen MOR 553S-8-26-9-54,
greatly inclined in Edmontosaurus spp., Prosaurolophus
maximus,Saurolophus spp., Maiasaura peeblesorum,
Brachylophosaurus canadensis); deep skull as in Krito-
saurus navajovius (ratio of dorsoventral height along pos-
terior margin of quadrate/anteroposterior length from
posterior quadrate margin to predentary oral margin of
0.70 or greater; this measurement is approximated on
BYU 13258 to be 0.75); temporal bar and frontal inclined
to approximately 40to the horizontal as seen in Kritosau-
rus spp.
Derivation of name. condo (Latin) bury, in reference
to being buried in rock; rupes (Latin) cliffs, for being
discovered in the Book Cliffs of Utah.
Figure 3. Rhinorex condrupus gen. et sp. nov. skull in right lat-
eral view. A, reconstruction with labelled autapomorphies; B,
BYU 13528. Abbreviations: nap, nasal anteroventral process;
ppd, premaxilla posteroventral process dorsal expansion. Scale
bar D10 cm.
New hadrosaurid from the Campanian of Utah 3
Occurrence. Neslen Formation, ~12 m from base of for-
mation (Anderson et al.1999) in Thompson Canyon,
Grand County, Utah; average age approximately 75.88
Ma or 75.15 Ma adjusted from Cobban et al.(2006) and
modified by Thomson et al.(2013) from Izett et al.
(1998), respectively. Brian Anderson and Roger Wagerle,
students at the University of California at Riverside, dis-
covered the site in 1992 while conducting a geological
study of the Book Cliffs area. Together with their advisor
Mary Droser, and another graduate student, Reese Barrick
from the University of Southern California, they pursued
an excavation permit. William Stokes at the Utah BLM
Office suggested they use BYU as a designated repository
with Ken Stadtman’s collection expertise.
Description. See below.
Remarks. Several other characteristics of the skull are
unique to this specimen, such as the vertical orientation of
the anterior infratemporal fenestra margin and the exceed-
ingly large (80 mm) height differential between the poste-
rior skull and the dorsal orbital margin, but due to either
its fragmentary nature or possible preservational deforma-
tion, we are reluctant to diagnose the species on these fea-
tures. This is especially given that two other unambiguous
unique traits are listed above. Each of these ambiguous
traits is described further below.
Description and comparisons
The following description includes only cranial elements
because the postcranial elements are currently encased in
sandstone at the BYU Museum of Paleontology or at the
field locality. The dorsal portion and left side of the skull
were exposed prior to recovery. As a consequence, many
of the left lateral skull elements are eroded or deeply
Table 1. Measurements of the skull BYU 13258, as described in Campione & Evans (2011) and McGarrity et al.(2013). The crest
measurements were designed largely for Prosaurolophus (McGarrity et al.2013) but were co-opted here to make the datasets more com-
parable, despite the apparent lack of an ossified crest. These were taken at the apex of the nasal where crest apex is here assumed to be
the point on the nasal directly dorsal to the posteriormost edge of the narial foramen.
Measurement description Length (mm)
Length of the skull measured from the tip of the snout to the back of the quadrate Not preserved
Height of the skull measured from the apex of the crest to the maxillary tooth row 300
Length of the crest measured from its rostral inflection point to the back of the crest N/A
Length of the lateral extension of the crest measured from the back of the circumnarial depression to the
back of the crest
N/A
Crestsnout length measured from the apex of the crest to the tip of the snout 550
Crest to frontal length measured from the apex of the crest to the caudal margin of the nasal ~165
Height of the crest measured from the apex to the ventral margin of the lateral extension of the crest N/A
Preorbital length measured from the tip of the snout to the orbital contact between the lacrimal and jugal 470
Circumnarial depression length measured from the reflected margin of the premaxilla to the back of the
circumnarial depression
485
Naris length measured from the rostroventral the contact between the nasal and premaxilla to its caudal
V-shaped margin
341
Prenarial length measured from the tip of the snout to the rostral margin of the naris 460
Length of the frontal measured along the midline of the skull from the rostral contact with the nasal and the
caudal contact with the parietal
~160
Length of the parietal measured from the rostral contact with the frontals to its caudal margin between the
squamosals
170
Length of the postorbital measured from the contact with the prefrontal along the orbital margin to its caudal
bifurcation
200
Maximum width of premaxilla measured from the midline of the skull to the lateral margin of the premaxilla Not preserved
Length of the jugal measured from the orbital contact with the lacrimal and the dorsal contact with the quadrate Not preserved
Minimum height of the jugal measured beneath the orbit 55
Minimum height of the jugal measured beneath the infratemporal fenestra rostral to the jugal flange Not preserved
Height of the jugal measured beneath the infratemporal fenestra at the jugal flange Not preserved
Height of maxilla measured from its dorsal margin to the maxillary tooth row 120
Length of dentary measured from its rostral margin to the back of the coronoid process of the dentary Not preserved
Height of dentary measured from the tooth row to the ventral margin of the dentary Not preserved
Length of diastema measured from the rostrodorsal contact with the predentary to the dentary tooth row Not preserved
Maximum height of the quadrate measured from its dorsal head to the ventral mandibular condyle Not preserved
4 T. A. Gates and R. Scheetz
weathered, with the prefrontals mostly eroded from the
specimen along with the nasals on the nasofrontal contact,
exposing the suture between these two elements. The
frontals suffered weathering damage in the form of trans-
form cracking and erosion, yet retain enough morphology
for description. See Table 1 for measurements of the skull
following recent morphometric studies of Campione &
Evans (2011) and McGarrity et al.(2013).
Premaxilla
The right premaxilla (Fig. 3) is preserved better than
the left element, which has slight postfossilization
deformation. These elements display a broad, slightly
arcuate oral margin and an upturned premaxillary lip. The
latter feature is less pronounced than in the saurolophine
Edmontosaurus spp. (e.g. NCSM 23119). Angular
grooves and ridges line the underside of the oral margin,
smaller than those of Gryposaurus monumentensis (Gates
& Sampson 2007). Dorsally, as in Gryposaurus species
(Prieto-M
arquez 2012), the premaxillary shelf is divided
into anterior and posterior fossae by a low ridge running
posterolaterally from the anterior margin of the nasal
fenestra toward the lateral premaxillary oral margin. Both
the dorsal and lateral processes display typical Gryposau-
rus morphology, including the diagnostic flaring of the
lateral process, although the morphology differs subtly
from the latter clade by not protruding laterally, only
Figure 4. Unique morphology observed on Rhinorex condrupus gen. et sp. nov., BYU 13528, nasal. A, right lateral view of complete
skull of BYU 13528 with rectangles showing locations of BE; B, nasal bumps as preserved on left nasal prior to mechanical removal;
arrows show location of each protuberance below; C, close up of anteroventral nasal process with the unique fish hook morphology; D,
dorsal view of nasal posterior region; E, left lateral view of nasal posterior region. Abbreviations: cnb, circumnarial boss; Na, nasal;
Pmx, premaxilla. Scale bars: A, D, E D10 cm; B, C D5 cm.
New hadrosaurid from the Campanian of Utah 5
anterodorsally. The extent to which the lateral process
extends posterodorsally along the face in Rhinorex con-
drupus is uncertain, but it is likely that it is equivalent to
Gryposaurus spp. and Kritosaurus in reaching the lacri-
mal (Gates & Sampson 2007; Prieto-M
arquez 2014), but
not the prefrontal.
Maxilla
In general aspect, the maxilla (Fig. 3)ofRhinorex condru-
pus is very similar to species of Gryposaurus, with a broad
dorsal process positioned anterior to the anteroposterior
midpoint of the element. This taxon is similar to the type
specimen of G. notabilis (CMN 2278) in that the large
maxillary foramen is exposed slightly more posteriorly,
that is, further away from the maxillarypremaxillary
contact, than in the type specimen of G. monumentensis
(RAM 6797) and a referred specimen of G. notabilis
(ROM 873) where the foramen is partially overlapped by
the premaxillary lateral process. Gryposaurus latidens has
the maxillary foramen positioned more ventrally than in
the other Gryposaurus species (Prieto-M
arquez 2012).
The maxillary foramen is also much larger in R. condru-
pus compared to other species, which is considered here
to be variable among individuals until evidence arises to
the contrary. Similar to G. notabilis (Gates & Sampson
2007), the anterodorsal process cannot be seen laterally
through the narial foramen. There is a line of several
smaller foramina oriented anteroposteriorly from approxi-
mately the midline of the maxilla extending posteriorly to
lie almost directly ventral to the jugal process. The latter
feature of BYU 13285 is smaller than in G. monumenten-
sis (RAM 6797) and a larger specimen of G. notabilis
(CMN 2278), more similar in proportions to smaller speci-
mens of G. notabilis (e.g. ROM 873 and TMP 80.22.1).
The ectopterygoid shelf extends horizontally to the poste-
rior margin of the maxilla, yielding an ectopterygoid ridge
that is more weakly developed than in G. monumentensis
(Gates & Sampson 2007). A row of nutrient foramina arch
into the upper third of the maxillary body on the medial
side of the element, as is typical with hadrosaurids (Prieto-
M
arquez 2010c). Dorsal to the medial nutrient foramina
the maxillary body swells, with a large overhang forming
throughout the articulation with the palatine and pterygoid.
Maxillary teeth are covered in a thick iron concretion and
therefore description of the morphology is not possible
and the exact tooth count is unknown. Yet, given the close
similarity to G. notabilis and G. monumentensis, we pre-
dict that R. condrupus will have over 40 tooth positions
and over three teeth within each tooth family.
Nasal
Both nasals are preserved on BYU 13258, although only
the anterior half of the nasal (Fig. 3B) is preserved in
Figure 5. Dorsal view of the Rhinorex condrupus gen. et sp.
nov. skull roof, BYU 13528. A, line drawing; B, photograph.
Dotted lines are incomplete edges of elements. Vertical lines in
drawing represent rock matrix. Horizontal lines represent broken
bone surfaces. Abbreviations: fns, frontonasal suture; fpf, fron-
talprefrontal suture; Fr, frontal; Pa, parietal; Po, postorbital;
Sq, squamosal. Scale bars D10 cm.
6 T. A. Gates and R. Scheetz
excellent quality. The anterior process terminates prior to
the anterior margin of the narial foramen, as in Gryposau-
rus species, Acristavus gagslarsoni, some specimens
of Brachylophosaurus, and other more primitive iguano-
dontians (Gates & Sampson 2007; Gates et al.2011). At
an early stage of preparation, several protuberances were
discovered on the dorsal surface of the anterior nasal pro-
cess (Fig. 4A), but subsequently were abraded mechani-
cally. These protuberances increased in size posteriorly in
a similar fashion to Gryposaurus sp. AMNH 5350, yet
distinct from this specimen. Due to the poor preservation
of the posterior nasal on BYU 13258 it is unclear how far
the bumps would extend on the nasal, although the uner-
oded surface of the preorbital nasal apex shows that the
bumps could have extended that distance.
A ventral process of the nasal extends to contact the
lacrimal and projects anteriorly, thereby forming the
entire posterior and posteroventral borders of the narial
foramen. This configuration is seen in all Gryposaurus
species and brachylophosaurin hadrosaurids, but the
dorsoventrally broad process and dorsally oriented barb
gives the entire anteroventral process a fish hook sem-
blance (Fig. 4B) unique to R. condrupus. It should be
noted that the type specimen of G. monumentensis
(RAM 6797) is missing most of the anteroventral nasal
process.
The dorsal surface of the nasal does not demonstrate the
arched apex as seen on Gryposaurus species. Instead the
anterior process breaks from its posterodorsal ascent to
proceed nearly horizontally. A diminutive or complete
lack of a nasal hump or arch has been documented on G.
notabilis specimens such as the juvenile TMP 80.22.1
once assigned to the species G. incurvimanus (Prieto-
M
arquez 2010c). Also, the larger ‘adult’ specimen
AMNH 5350 has been attributed to G. notabilis but lacks
a nasal hump (Prieto-M
arquez 2010a), looking more simi-
lar to Rhinorex.
Adjacent to the posterior margin of the circumnarial
fossa is a large rugose boss that prominently emanates
from the nasal. A similar structure was reported for
AMNH 5350 by Prieto-M
arquez (2010a) with the latter
structure being smaller in size and lacking rugose texture.
Further examination of other Gryposaurus notabilis speci-
mens (ROM 873, CMN 2278) revealed minor bulging in
the same area. As currently observed, BYU 13258 is the
only hadrosaurid to exhibit such a large boss with rugosity
on this region of the nasal.
In the postnarial region of the nasal, the element flattens
to a thin mediolaterally oriented platform sloping postero-
dorsally toward the frontal contact. This angled orienta-
tion is different from that seen in other saurolophine
hadrosaurid taxa, which instead possess a relatively hori-
zontal surface. Configuration of the nasofrontal contact
cannot be discerned on the posterior nasal platform.
Figure 6. Palate and braincase of Rhinorex condrupus gen. et
sp. nov., BYU 13528. A, line drawing; B, photograph. The brain-
case elements are not demarcated because weathering has oblit-
erated the defining sutures. Thick lines surrounding elements are
delimiting edges of that element, whereas thin lines are contacts
between bone and rock. Dotted lines are incomplete edges of ele-
ments. Vertical lines in drawing represent rock matrix. Horizon-
tal lines represent broken bone surfaces. Note that the dentary
was omitted from A but is present at the bottom of B. Abbrevia-
tions: CN, cranial nerve; Mx, maxilla; Pal, palatine; Pta, anterior
process of pterygoid; Ptq, quadrate process of pterygoid; Vo,
vomer. Scale bar D10 cm.
New hadrosaurid from the Campanian of Utah 7
Jugal
The jugal (Fig. 3) is typical for kritosaurin (sensu Prieto-
M
arquez 2014) species (Gates & Sampson 2007;
Prieto-M
arquez 2014) with a long pointed anterior process
fitting partially between the maxilla and lacrimal, a sig-
moidal ventral margin of the anterior region, and an
enlarged lacrimal process. The triangular posteroventral
process of the anterior region is wider than tall, and over-
all less robust than on G. monumentensis (RAM 6797).
Unlike most other species, which have a slightly to exag-
gerated posteriorly inclined postorbital process, this fea-
ture is positioned at 90relative to the body of the jugal in
BYU 13528. This condition is more similar to Kritosaurus
sp. (Prieto-M
arquez 2014; although one Gryposaurus
specimen from the Two Medicine Formation (MOR
553S-8-26-9-54) also shares this condition (A. Prieto-
M
arquez pers. comm.). The posteroventral flange does
not differ from any Gryposaurus species (Gates & Samp-
son 2007) and the posterior process is not preserved for
either the left or right jugal.
Lacrimal
Only the posteroventral section of the right lacrimal is
preserved in BYU 13258 (Fig. 3B). As in kritosaurin spe-
cies the jugal buttress is quite robust (Gates & Sampson
2007; Prieto-M
arquez 2014), protruding posteriorly into
the orbit as in Saurolophus osborni (e.g. AMNH 5220,
CMN 8796), Acristavus (MOR 1155), Edmontosaurus
annectens (e.g. NCSM 23119), some specimens of Bra-
chylophosaurus (e.g. MOR 794), and slightly in some
specimens of Maiasaura (e.g. ROM 447701).
Frontal
The frontal (Fig. 5) appears to match the morphology of
Kritosaurus navajovius (AMNH 5799) more closely than
other species of saurolophine in that it is highly angled
posterodorsally, as opposed to being nearly horizontal.
Erosion of the frontonasal suture reveals what may be the
centrally positioned fossae that accept posterior processes
from the nasals, a characteristic unique to Gryposaurus
Figure 7. Dentary of Rhinorex condrupus gen. et sp. nov., BYU 13528. A, general view medially; B, close up of dentary teeth in medial
view. Scale bars D5 cm.
8 T. A. Gates and R. Scheetz
species (Horner 1992), yet this structure is ambiguous on
BYU 13528. The frontal also contributes a small portion
to the orbital rim. Infiltration of the parietal into the fron-
tal is obscured due to erosion.
Postorbital
Weathering has obliterated the external contacts with
adjacent bones, making it difficult to know exact dimen-
sions of this element. The orbital margin is rugose, but
weathering has likely diminished the true magnitude of
bone texturing. Descending ventrally, the jugal process is
generally similar to other kritosaurins, but seems to pro-
ceed at a more vertical angle, especially at the distalmost
end where other species tend to have a posteriorly angled
process (Fig. 3; Gates & Sampson 2007). Ascending
posterodorsally, the squamosal process meets its counter-
part in a bifurcated contact, forming the temporal bar
that resides at an angle of 40from the horizontal, as
measured from the right temporal bar. Farke & Herrero
(in press) found that the flexion of the postorbital was
correlated with the maximum width of the skull at the
orbits. BYU 13528 has a skull width of approximately
190 mm, which when applied to the dataset presented by
Farke & Herrero (in press), provides a Spearman’s r of
0.597 and a permutation p-value of 0.053, meaning
statistically insignificant correlation between postorbital
angulation and skull width. Yet, Farke & Herrero (in
press) acquired a correlation (p-value D0.039) between
these variables without the inclusion of BYU 13528.
Therefore, it appears that the angle of ascension seen in
BYU 13528 falls outside the variation of Gryposaurus
specimens in their study. The anterodorsal corner of the
infratemporal fenestra arches more gently than other
hadrosaurid species. Finally, we should note that the
postorbital angulation is a character shared with Krito-
saurus (Prieto-M
arquez 2014). We should note there is
distortion of the posterior skull, in that the left side squa-
mosals are slightly displaced dorsally compared to the
right side. This alteration could conceivably depress the
right side of the skull, making the true angulation even
greater than reported here.
Squamosal
The anterior, or postorbital, process of the squamosal
inclines steeply anteroventrally, connecting with the post-
orbital to form the temporal bar (Fig. 3). The precotyloid
fossa is relatively shallow, not as incised as in Gryposau-
rus monumentensis (Gates & Sampson 2007). Little can
be described of the quadrate cotylus and the precotyloid
and postcotyloid processes due to breakage. Medially, the
squamosals do not appear to contact, but the sagittal
region is slightly damaged. The median processes form an
anteroposteriorly protracted overhang, which differs from
Edmontosaurus annectens (e.g. NCSM 23119),
Maiasaura (e.g. TCMI 2001.89.2) and Prosaurolophus
(e.g. CMN 2870) that have median squamosal processes
that are inclined posteroventrally. The median processes
of BYU 13528 also bend anteriorly towards the sagittal
midline. The supraoccipital can be seen just below and
posterior to the squamosals, offsetting the postcotyloid
processes from the squamosals (Fig. 5). This configuration
does not differ from Gryposaurus species.
Infratemporal fenestra
Rhinorex condrupus is unique in the morphology of the
entire anterior margin of the infratemporal fenestra, which
when the confluent processes of the jugal and postorbital
are joined, form a straight, vertical margin (Fig. 3). This
differs from all other hadrosaurids in that there is an over-
all trend of anteroventral deflection of the combined jugal
and postorbital processes that form the anterior margin of
the infratemporal fenestra. At its peak, the infratemporal
fenestra approaches 80 mm higher than the dorsal margin
of the orbital cavity. This taller development of the fenes-
tra compared to the orbit could be the largest height differ-
ence within hadrosaurids and is a result of the highly
inclined temporal bar. Despite the unique fenestra mor-
phology observed in BYU 13258, we are reluctant to con-
sider the discussed traits as species-specific apomorphies
until other referred specimens confirm the infratemporal
configuration and give insights to the posterior margin.
Neurocranium
Despite exposure of the endocranium (Fig. 6), little infor-
mation can be gleaned due to weathering and erosion of
the element sutures. All cranial nerves are observable, not
differing in position or relative size compared to other
hadrosaurids (Prieto-M
arquez 2010a).
Palate
The palatal elements (Fig. 6) in BYU 13528 are in
complete articulation; however, clear observation of
morphology is only available for the vomer. The
vomerpterygoid articulation is seen, with the anterior
process of the pterygoid clearly overlapping the posterior
process of the vomer. The pterygoid is marginally seen
overlapping the posterior maxilla and the palatine slightly
anterior. Little can be seen of the palatinemaxilla
contact.
Vomer
Paired vomers are preserved in articulation within BYU
13258, but only the left is fully observable (Fig. 6). The
elongated paddle-shape of the posterior region of the
New hadrosaurid from the Campanian of Utah 9
vomer is nearly identical to that seen in UMNH VP
13970, a specimen referred by Gates & Sampson (2007)
as a juvenile Gryposaurus monumentensis, as well as the
type specimen of that species, RAM 6797. Noting the var-
iation described in Gates & Sampson (2007), it seems that
the vomer is a potentially diagnostic element, at least at
the genus level, and possibly to species level. The vomer
present in BYU 13258 possesses an excavated vomer
body. The latter specimen maintains complete closure
around the entire excavation, unlike RAM 6797 that has
the lower margin of the vomer also removed. UMNH VP
13970 has a subcircular excavation in the middle of the
element with all margins closed, which means that either
the vomer undergoes considerable reconstruction through
ontogeny, the specimen has been misidentified, or there is
extreme variation in this element among individuals.
Dentary
The dentary is broken through the anterior half (Fig. 3).
The posterior half is robust, as seen in other Gryposaurus
species (Gates & Sampson 2007), with the posteroventral
portion of the coronoid process articulated with the suran-
gular. The remainder of the right coronoid is covered with
matrix, whereas the left coronoid shows a typical hadro-
saurid morphology of anteroposterior expansion with
exclusion of the surangular from the distalmost region.
Dentary teeth (Fig. 7) are ornamented with a single
median ridge, posteriorly offset, and mostly straight (only
a small portion are distally curved). At least three, and
likely up to five, make up each tooth family.
Phylogenetic analysis
Both a parsimony and Bayesian phylogenetic analysis
were performed on the data matrix included in the Supple-
mental Material. This matrix consists of 50 OTUs, 236
characters taken mainly from Prieto-M
arquez (2010c),
using Iguanodon bernissartensis as the outgroup. The par-
simony analysis was performed in TNT (Goloboff et al.
2003) with 1000 Wagner tree replicates and tree bisection
reconnection (saving 100 trees per replicate). The 120
most parsimonious trees obtained a tree length of 682
with a Consistency Index of 0.498 and Retention Index of
0.793.
Each saved individual tree yielded a monophyletic
Gryposaurus clade, with Rhinorex condrupus outside of
the genus. G. latidens is the next taxon up the tree, with
G. notabilis and G. monumentensis as sister taxa.
Although retained in the majority rule tree, the strict con-
sensus tree collapses the Gryposaurus clade (Fig. 8).
Notable differences between the trees recovered in this
analysis compared to the recent studies of Prieto-M
arquez
(2012) and Godefroit et al.(2012) involve the position of
the genera Kritosaurus,Wulagasaurus and Edmontosau-
rus. Firstly, Kritosaurus is placed by both Prieto-M
arquez
(2012) and Godefroit et al.(2012) near the genus Grypo-
saurus, yet here the analysis placed it as the most basal
saurolophine clade. Next, Wulagasaurus is a taxon known
from few skull elements and has been placed toward the
base of Saurolophinae (Godefroit et al.2012) or at the
base of a clade containing the Kritosaurini (sensu Prieto-
M
arquez (2012)). In this study Wulagasaurus is placed at
the base of a clade containing Brachylophosaurini (sensu
Gates et al.2011), as posited by Xing et al.(2012).
Prieto-M
arquez (2012) placed Edmontosaurus as a basal
clade within Saurolophinae, whereas this study and Gode-
froit et al.(2012) place the genus nearer Prosaurolophus.
The Bayesian analysis was run in MrBayes 3.2 (Ron-
quist et al.2012) with 10 million generations, sampling
every 5000 generations, standard data, equal and variable
rates, and 25% burn-in. A complete list of analysis set-
tings can be found in the Supplemental Material. The tree
produced through the variable rate model (average stan-
dard deviation of split frequencies from last one million
generations equalled 0.008; harmonic mean 3497.86;
Fig. 9) did not differ substantially from that of a fixed
(equal) rate model (harmonic mean 3499.18) in topol-
ogy. That said, both the fixed rate and variable rate trees
are superficially similar to the variable model of Prieto-
M
arquez (2010c) in that Lambeosaurinae is nested within
the Saurolophinae instead of being a sister clade, thereby
making Saurolophinae paraphyletic. This topology is
extremely different from that of the parsimony analysis,
and given the current fossil record, seems quite unlikely.
Other small variations are present between these trees, yet
given that this avenue of hadrosaurid phylogenetic inquiry
is still new, we feel that subtle discrepancies should best
be discussed pending further investigation of model
parameters on varying datasets. Evans (2010) analyzed a
phylogenetic dataset through Bayesian algorithms, and
even though that dataset focused only on lambeosaurine
taxa, expansion of this alternative data to saurolophines
may provide more insight to the non-traditional results
presented here and in Prieto-M
arquez (2010c).
Discussion
Biostratigraphical context
Following the North American hadrosaurid biostrati-
graphical framework of Gates et al.(2012, fig. 4, Rhinorex
condrupus labelled as Gryposaurus sp. nov.) and the older
approximate ages for the type locality of R. condrupus,
this new species lived at approximately the same time as
Gryposaurus notabilis and/or Gryposaurus monumenten-
sis,Prosaurolophus maximus and an undescribed taxon
from Big Bend National Park in Texas. Alternatively, if
the younger ages are considered, the only known
10 T. A. Gates and R. Scheetz
hadrosaurid taxon that may have lived simultaneously
with R. condrupus is Prosaurolophus maximus (McGarr-
ity et al.2013). North American hadrosaurid taxa are rela-
tively sparse for the younger time period, making this
chronozone especially important for understanding shifts
in hadrosaurid diversity during the Campanian.
Biogeographical and environmental context
Rhinorex condrupus was discovered in the Book Cliffs of
central Utah, within estuarine sediments deposited by a
river on the margin of the Western Interior Seaway
(Anderson et al.1999). This is the first hadrosaurid spe-
cies known from central Utah, whereas two species of
Gryposaurus,G. sp. and G. monumentensis (Gates et al.
2012,2013), were found only 250 km south-west, in
southern Utah. Due to the dating uncertainty for the R.
condrupus type locality, it is uncertain whether this new
taxon existed contemporaneously with the aforemen-
tioned Gryposaurus species. If so, this is one of the most
dramatic cases of dinosaurian habitat partitioning
recorded; especially when one considers the relatively
short distance between occurrences in relation to the large
body size of these species.
Sediments of the Kaiparowits Formation in southern
Utah record a more upland, alluvial-style swamp environ-
ment compared to the coastal, tidally influenced swamp of
the Book Cliffs. One could speculate that such differences
in habitat could have created different plant communities
that may have led to the segregation of these hadrosaurs.
Figure 8. Maximum parsimony consensus trees. A, majority rule; B, strict consensus. Numbers are Bremer support values. Iguanodon
bernissartensis was used as the outgroup.
New hadrosaurid from the Campanian of Utah 11
However, without better assessment of the local plant
communities and more accurate dating of the Neslen For-
mation, and the R. condrupus type locality in particular,
such ecological speculation has no foundation. Nonethe-
less, it is worth noting that R. condrupus is the first of the
Gryposaurus clade to be found in a marine influenced
environment (although Prieto-M
arquez (2014) assigned
YPM-PU 16970 from the Bearpaw Shale to Gryposaurus
sp.), and that the previous hypothesis that members of the
genus were more likely generalist feeders (Gates &
Sampson 2007) possibly gains support given an increase
in the breadth of environmental preferences seen in hadro-
saurids exhibiting a ‘gryposaur’-type morphology.
Rhinorex is not the first hadrosaurid taxon to be found
near marine sediments (see Horner et al.2004 for list of
taxa). Kritosaurus (sensu Prieto-M
arquez 2014) speci-
mens from the Cerro del Pueblo Formation are also pre-
served in nearly identical environments (Eberth et al.
2004). Prieto-M
arquez (2014) supported previous phylo-
genetic hypotheses that the genera Kritosaurus and Gry-
posaurus are closely related, which may indicate a similar
habitat preference for R. condrupus and Kritosaurus sp.
Evolutionary implications
In addition to the environmental similarities mentioned
above, there are a couple of features of the Rhinorex con-
drupus skull that generally differ from Gryposaurus spe-
cies but are present in Kritosaurus specimens. First, the
large anterior maxillary foramen is generally positioned
closer to and slightly hidden by the lateroventral process
of the premaxilla (RAM 6797, ROM 873, but see the
slightly more lateral position of CMN 2278), whereas on
R. condrupus and Kritosaurus horneri (BYU 12950;
Prieto-M
arquez 2014) the foramen is positioned well pos-
terior to the contact with the posterolateral premaxillary
process. Secondly, the postorbital process of the jugal is
oriented vertically, as opposed to slightly inclined as in
Gryposaurus species (Gates & Sampson 2007). Kritosau-
rus species have a vertical postorbital process (Prieto-
M
arquez 2014). Despite Kritosaurus spp. and Gryposau-
rus spp. resolving in different clades on the cladograms
presented in Figures 8 and 9, these taxa do seem closely
related based on gross morphology, and R. condrupus
superficially seems to be even more similar to Kritosaurus
spp. than other Gryposaurus species. Interestingly, if the
later radiometric date is taken for the R. condrupus local-
ity, then this places the taxon within a small window of
time from which no hadrosaurids are known from the
south-western USA, just after the last occurrence of G.
monumentensis (Gates et al.2013) and prior to the first
occurrences of Kritosaurus in the Kirtland Formation
around 73.5 Ma (Gates & Evans 2005; Gates et al.2012).
Hadrosaurid phylogenetic conflict
Over the past decade, hadrosaurid phylogenetic informa-
tion has increased dramatically through the naming of
many new species and increasing the number of phyloge-
netic traits used in analyses. The rapid influx of traits
Figure 9. Bayesian phylogenetic consensus tree with uncalibrated branch lengths. Iguanodon bernissartensis was used as the outgroup.
Numbers are branch length values.
12 T. A. Gates and R. Scheetz
within published phylogenies has also produced as many
conflicting cladistic hypotheses as there are publications.
Here we utilize the program SplitsTree 4.13.1 (Huson &
Bryant 2006) to easily visualize areas of conflicting posi-
tion of terminal taxa within sets of phylogenetic trees.
SplitsTree 4.13.1 produces networks from inputted phylo-
genetic trees in order to identify taxa that change position
throughout the selection of trees as well as mapping the
changes in position. Those OTUs that do not move around
the tree will be represented by a single line, whereas those
that do move will have multiple lines linked to other taxa
with which they are found through the sampled trees. Split
networks do not necessarily convey any evolutionary rela-
tionships in the way phylogenetic trees are designed
(Huson & Bryant 2006). We used trees derived from the
strict consensus analyses above and those of Prieto-
M
arquez (2010c) and Godefroit et al.(2012) to test for
conflict between presented tree topologies.
Most iguanodontian relationships remained stable
through the trees (Fig. 10); however, severe conflict was
found within the Saurolophinae. The web of connections
seen within the clade demonstrates that subclades close to
Gryposaurus spp. and Prosaurolophus are labile on the
tree, but the taxa within those clades are relatively stable.
There was minor conflict in the placement of Wulagasau-
rus, and the relationships within the Brachylophosaurini.
Conclusions
Here we present Rhinorex condrupus, a new saurolophine
hadrosaurid from the Upper Cretaceous Neslen Formation
of central Utah. This species is diagnosed on a unique fea-
ture of the nasal, the anteroventral nasal process with a
small dorsal projection that gives an overall ‘fish hook’
appearance to the area, as well as the lateroventral process
of the premaxilla displaying a dorsal exaggeration. Other
characters that aid differentiation of this species are the
lack of an osseous nasal ornamentation, a large boss on
the circumnarial fossa, a series of protuberances rising on
the medial margin of the nasal, and a squamosal that rises
at a steeper angle compared to most other hadrosaurid
species.
Figure 10. Supernetwork of parsimony strict consensus trees obtained from this study, Prieto-M
arquez (2010c) and Godefroit et al.
(2012).
New hadrosaurid from the Campanian of Utah 13
Rhinorex is found in a coastal, tidally influenced envi-
ronment, which when considered with the other environ-
mental and geographical occurrences (ranging from
southern Canada through Texas and arid uplands through
coastal plain) of the genus Gryposaurus adds additional
evidence to the hypothesis that species of this skull mor-
phology could have been more generalist feeders (Gates
& Sampson 2007). Not tackled, but of critical importance
for future studies of feeding habits and cranial ornamenta-
tion in hadrosaurids, is the supposed difficulty of main-
taining nearly identical cranial ornamentation, which
should act as a uniting factor, while at the same time dif-
ferentiating into different species with seemingly different
environmental preferences.
Finally, new parsimony and Bayesian phylogenetic
analyses demonstrate similarity with prior analyses in
basic respects but differ with regard to the placement of
certain mobile taxa. As shown through the use of consen-
sus tree networks, within individual studies those mobile
taxa include basal hadrosauroids and higher order taxa
with sparser skeletal remains. Combining the phyloge-
netic trees from multiple analyses into a single supertree
network shows that overall, little consensus exists
between hadrosaurid phylogenies.
Acknowledgements
We thank Ken Stadtman for insight into the original excava-
tion and location of the site; Jeff Higgerson for relocating the
excavation site; Austin Andrus, Shamra Smith and Josie New-
bold for initial preparation; Eric Lund for help relocating the
excavation site and preparation expertise; Lindsay Zanno and
Lisa Hertzog for final preparation. We thank citizen scientists
Andrea, Claire, and Joshua for their help naming this dinosaur.
Virginia Greene illustrated the reconstruction and palate. Fund-
ing was provided by Patrick O’Connor and the Ohio Univer-
sity Heritage College of Osteopathic Medicine Postdoctoral
Fellowship (to TAG) and the National Geographic Waitt
Foundation [#W246-12] (to TAG).
Supplemental data
Supplemental material for this article can be accessed at:
http://dx.doi.org/10.1080/14772019.2014.950614
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New hadrosaurid from the Campanian of Utah 15
... A nasal arch is also present in Rhinorex condrupus, a sister taxon to Gryposaurus spp. from the Neslen Formation of eastern Utah, in late Campanian strata dated to 75-74.5 Ma (Gates & Scheetz 2015). Despite sharing an arcuate dorsal profile of the nasal, A. palimentus is clearly different from R. condrupus and Gryposaurus spp. ...
... Finally, the anterior process of the jugal of Gryposaurus (e.g. G. notabilis, CMN 2278) and R. condrupus (Gates & Scheetz 2015, fig. 3) is substantially deeper with a relatively short anterior apex, compared to the shallow process and long apex of A. palimentus (Fig. 9A). Naashoibitosaurus ostromi is a kritosaurin saurolophine (Prieto-M arquez 2014) originally described by Hunt & Lucas (1993) on the basis of a skull and fragmentary postcranium. ...
... specimens of Gryposaurus notabilis (Prieto-Marquez 2010c) and Naashoibitosaurus ostromi (Prieto-M arquez 2014,fig. 21) or Rhinorex(Gates & Scheetz 2015). ...
Article
We describe a new genus and species of hadrosaurid dinosaur, Aquilarhinus palimentus, from the lower shale member of the Aguja Formation (lower Campanian) of Big Bend National Park, south-western Texas. This species is characterized by several autapomorphies of the facial skeleton and mandible, including a crest composed of broadly arched nasals. Notably, the symphyseal processes of the dentary are elongated and reflected dorsally, causing the dentaries to meet with a ‘W’-shaped anterior profile. A hypothesized shovel-shaped ‘bill’, associated with widening of the skull, in A. palimentus might have been used in shovelling out and scooping up semiaquatic vegetation. This animal is otherwise superficially similar to kritosaurins like Gryposaurus but differs in the retention of key plesiomorphic character states in the maxilla and jugal. Phylogenetic analysis reveals Aquilarhinus to be a non-saurolophid hadrosaurid allied to Latirhinus from the late Campanian of Mexico, which bears a similar broadly arched nasal. The recognition of this lineage adds to the diversity of non-saurolophid hadrosaurids and points to the existence of a hitherto unknown diversity of ‘duck-billed’ dinosaurs outside of the saurolophine-lambeosaurine radiation. Cranial crests were ancestral for early hadrosaurids and evolved before the saurolophid radiation. Ancestrally, crests were ‘solid’, and consisted of arched nasals. These were retained among kritosaurins and subsequently modified into the diverse crest morphologies observed among derived saurolophines. Lambeosaurine ‘hollow-crested’ crest morphology departed from the ancestral, ‘solid-crested’ pre-saurolophid condition early following the origin of that clade. http://www.zoobank.org/urn:lsid:zoobank.org:pub:F7CE1BE7-1A76-4628-8510-93C37A1A807E
... Another hadrosaur closely related to the gryposaur tribe is Rhinorex condrupus. It was discovered in the Book Cliffs of central Utah, within estuarine sediments deposited by a river on the margin of the Western Interior Seaway (Gates & Scheetz, 2014). Considered initially as a basal kritosaurine, recently Xing et al. (2017) placed it as sister taxon to G. latidens. ...
... Considered initially as a basal kritosaurine, recently Xing et al. (2017) placed it as sister taxon to G. latidens. Rhinorex condrupus is thought coeval with G. monumentensis, but, as pointed out by Gates & Scheetz (2014), the absence of accurate dating of the sediments might have falsified the contemporaneity of these two closely related species and renders premature any palaeobiogeographic discussion including the former. ...
... 26). The most recent additions to the Kritosaurini are Rhinorex condrupus, placed at the base of the gryposaur node in the Kritosaurini phylogeny by Gates & Scheetz (2014), and ?Gryposaurus alsatei, placed within the genus Gryposaurus in an analysis by Lehman et al. (2016), pending more complete material. Vialli (1960) referred MSNM V345 to Kritosaurus notabilis on the basis of the cranial osteology. ...
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Abstract - MSNM V345 is a partial skeleton of the North American hadrosaur species Gryposaurus notabilis, Lambe 1914, discovered in 1922 in the Dinosaur Park Formation of Dinosaur Provincial Park, Alberta, Canada. It was shipped in several crates to the Museo di Storia Naturale di Milano (MSNM), Italy, where it arrived in October 1958. Careless transportation during its long journey to Milan meant that the skeleton arrived extremely damaged and required heavy restoration work by MSNM staff. A preliminary study of the specimen was conducted by Vittorio Vialli in 1960 while part of it was still under preparation. That study was followed by a more detailed, although still partial, osteological description by Giovanni Pinna in 1979. On the centennial of the species’ discovery, we decided to examine the specimen in even greater detail in order to improve knowledge on the dinosaur’s skeletal anatomy and help clarify the taxonomy of the genus. Here, we redescribe the dinosaur’s osteology, focusing on unpublished elements, such as metapodials, phalanges, sacral vertebrae, and some caudal vertebrae, recently discovered to be located at the MSNM. Isolated appendicular elements found at the same quarry and tentatively referable to other individuals of the same taxon or to other dinosaur species are also briefly mentioned. Histological analysis of a core obtained from the femur revealed that it was made of fibrolamellar bone with a high number of Haversian systems. The presence of an external fundamental system indicates that the individual was fully adult at the moment of death. Of note, the skeletal remains present with traces of at least four pathological conditions: a cavity in the predentary is speculated to be the result of osteomyelitis; the fifth dorsal vertebra is fused to the left rib through a overgrowth of bone, and is interpreted as osteosclerosis subsequent to a fracture; the neural spine of the 26th caudal vertebra is fractured and healed, and the centrum has a strap of bone growing up to the side of the preceding centrum, explainable as idiopathic skeletal hyperostosis. A review of the skeletal reconstructions of the genus is also presented, followed by a summary of the skin remains and remarks on other anatomical traits. Altogether, the new data obtained on MSNM V345 have allowed us to present a more accurate and up-to-date skeletal reconstruction and in vivo restoration of G. notabilis.
... The acquisition of a greatly enlarged narial fenestra in Brachylophosaurus was, in Horner's view, possibly related to the more seaward, lowland palaeoenvironments preferred by this taxon. Gates and Scheetz (2015) invoked a similar hypothesis of habitat partitioning among closely related hadrosaurines between upland versus coastal lowland palaeoenvironments to explain the possibly coeval occurrences of Rhinorex condrupus (Gates and Scheetz 2015) and Gryposaurus monumentensis (Gates and Sampson 2007) only 250 km apart in central and southern Utah. Cullen and Evans (2016) demonstrated that the broad composition of dinosaur taxa in microsite assemblages is generally stable across varying palaeonvironments in the Upper Cretaceous of Alberta, and questioned the role of environmental sensitivity as a driver of dinosaur distribution in Laramidia. ...
... The acquisition of a greatly enlarged narial fenestra in Brachylophosaurus was, in Horner's view, possibly related to the more seaward, lowland palaeoenvironments preferred by this taxon. Gates and Scheetz (2015) invoked a similar hypothesis of habitat partitioning among closely related hadrosaurines between upland versus coastal lowland palaeoenvironments to explain the possibly coeval occurrences of Rhinorex condrupus (Gates and Scheetz 2015) and Gryposaurus monumentensis (Gates and Sampson 2007) only 250 km apart in central and southern Utah. Cullen and Evans (2016) demonstrated that the broad composition of dinosaur taxa in microsite assemblages is generally stable across varying palaeonvironments in the Upper Cretaceous of Alberta, and questioned the role of environmental sensitivity as a driver of dinosaur distribution in Laramidia. ...
Article
We describe a new partial skull with braincase of a maiasaurin hadrosaurid from the Milk River Ridge Reservoir near Warner, southern Alberta, as the first diagnostic occurrence of Maiasaura in Canada. This material was collected in the Oldman Formation, at approximately the same stratigraphic level as a nearby bonebed of the ceratopsid Coronosaurus brinkmani. The assignment of this specimen to Maiasaura, rather than to Brachylophosaurus, is supported by the narrow and acute posterior margin of the external naris, the relationship between the postorbital and squamosal in the supratemporal bar, and the morphology of the frontals, which are greatly thickened and elevated anteriorly, with the dorsal surface not completely covered by the nasofrontal contact at adult size. The occurrence of both Maiasaura and Brachylophosaurus in approximately similar-aged deposits of the Comrey Sandstone zone in southern Alberta provides support for some cladogenesis in the evolutionary history of Maiasaurini. Geographically, the more western distribution of Maiasaura localities with respect to all Brachylophosaurus localities is consistent with the hypothesis that a preference for more inland versus seaway-adjacent habitats may have influenced the phylogenetic divergence of these taxa.
... Therefore, paleobiological and faunal studies that utilize isolated teeth can provide more faunal information than those that rely strictly on skeletal elements (Rensberger & Krentz, 1988;Currie, Rigby & Sloan, 1990;Farlow et al., 1991;Fiorillo, 1999;Sankey, 2001Sankey, , 2008aSankey, , 2008bHeckert, 2004;Vullo, Neraudeau & Lenglet, 2007;Schoch et al., 2018). Furthermore, due to the wide morphological diversity of theropod teeth, they can be used to identify new taxa (Currie, Rigby & Sloan, 1990;Baszio, 1997aBaszio, , 1997bSankey, 2001;Sankey et al., 2002;Larson, 2008;Gates & Scheetz, 2015). Some theropod clades that were present in the Mussentichit Member such as oviraptorosaurs (Makovicky, Zanno & Gates, 2015), or likely present such as ornithomimosaurs, were toothless and thus would not be represented in microvertebrate samples. ...
... To better constrain the diversity of theropod species represented in our sample, we followed the approach of several recent studies (Smith, Vann & Dodson, 2005;Larson & Currie, 2013;Hendrickx, Mateus & Araújo, 2014;Williamson & Brusatte, 2014;Gates & Scheetz, 2015) by performing principal component (PCA) and discriminant (LDA) analyses in the program PAST version 3.19 (Hammer, Harper & Ryan, 2001) on two, independently derived, taxonomically comprehensive databases of theropod tooth measurements including the eight theropod teeth from the COI. Measurements follow Smith, Vann & Dodson (2005) andLarson & Currie (2013) (Fig. 2) and were taken in the program ImageJ (Rasband, ImageJ & National Institutes of Health, 2011). ...
Article
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The vertebrate fauna of the Late Cretaceous Mussentuchit Member of the Cedar Mountain Formation has been studied for nearly three decades, yet the fossil-rich unit continues to produce new information about life in western North America approximately 97 million years ago. Here we report on the composition of the Cliffs of Insanity (COI) microvertebrate locality, a newly sampled site containing perhaps one of the densest concentrations of microvertebrate fossils yet discovered in the Mussentuchit Member. The COI locality preserves osteichthyan, lissamphibian, testudinatan, mesoeucrocodylian, dinosaurian, metatherian, and trace fossil remains and is among the most taxonomically rich microvertebrate localities in the Mussentuchit Member. To better refine taxonomic identifications of isolated theropod dinosaur teeth, we used quantitative analyses of taxonomically comprehensive databases of theropod tooth measurements, adding new data on theropod tooth morphodiversity in this poorly understood interval. We further provide the first descriptions of tyrannosauroid premaxillary teeth and document the earliest North American record of adocid remains, extending the appearance of this ancestrally Asian clade by 5 million years in western North America and supporting studies of pre-Cenomaninan Laurasian faunal exchange across Beringia. The overabundance of mesoeucrocodylian remains at the COI locality produces a comparatively low measure of relative biodiversity when compared to other microvertebrate sites in the Mussentuchit Member using both raw and subsampling methods. Much more microvertebrate research is necessary to understand the roles of changing ecology and taphonomy that may be linked to transgression of the Western Interior Seaway or microhabitat variation.
... solid-crested hadrosaurids Saurolophinae. Although this new name has gained some acceptance in the literature (e.g., [8][9][10]), not all current phylogenies recover Hadrosaurus apart from the solid-crested hadrosaurids (e.g., [11,12]). Therefore, in keeping with tradition and some recent phylogenies, we use the clade name Hadrosaurinae, which is practically synonymous with Saurolophinae, except for the inclusion of Hadrosaurus [13]. ...
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Background Dinosaur eggs containing embryos are rare, limiting our understanding of dinosaur development. Recently, a clutch of subspherical dinosaur eggs was discovered while blasting for a construction project in the Upper Cretaceous red beds (Hekou Formation) of the Ganzhou Basin, Jiangxi Province, China. At least two of the eggs contain identifiable hadrosauroid embryos, described here for the first time. Results The eggs, attributable to Spheroolithidae indet., are thin-walled and small (~ 660 mL) compared to those of Lambeosaurinae. The shape of the embryonic squamosal is reminiscent of that seen in the Late Cretaceous hadrosauroids Levnesovia transoxiana , Tanius sinensis , and Nanningosaurus dashiensis , suggestive of possible affinities. Conclusion The small size of the eggs and embryos, similar to those of Hadrosaurinae, indicates that the larger eggs and hatchlings typical of Lambeosaurinae are evolutionarily derived.
... Farke & Herrero (2014) showed that ontogeny plays a critical role in angulation with larger (presumably older) individuals possessing more Squamosal-The squamosal (Fig. 11) meets the postorbital anteriorly (as described above). The precotyloid fossa is deep and triangular, similar to that described in the hadrosaurid Gryposaurus monumentensis , Rhinorex (Gates & Scheetz, 2015), as well as Altirhinus (Norman, 1998;Fig. 4), Proa (McDonald et al., 2012b), and Jinzhousaurus (Wang & Xu, 2001;Barrett et al., 2009). ...
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We describe a new iguanodontian ornithopod, Choyrodon barsboldi gen. et sp. nov. from the Albian-aged Khuren Dukh Formation of Mongolia based on several partial skeletons interpreted to represent a subadult growth stage based on osteohistological features. This new taxon is diagnosed by many autapomorphies of the maxilla, nasal, lacrimal, opisthotic, predentary, and surangular. Choyrodon displays an unusual combination of traits, possessing an open antorbital fenestra (a primitive ornithopod trait) together with derived features such as a downturned dentary and enlarged narial fenestra. Histological imaging suggests that the type specimen of Choyrodon would have been a subadult at the time of death. Phylogenetic analysis of two different character matrices do not posit Choyrodon to be the sister taxon or to be more primitive than the iguanodontian Altirhinus kurzanovi , which is found in the same formation. The only resolved relationship of this new taxon is that it was hypothesized to be a sister-taxon with the North American species Eolambia caroljonesa . Though discovered in the same formation and Choyrodon being smaller-bodied than Altirhinus , it does not appear that the former species is an ontogimorph of the latter. Differences in morphology and results of the phylogenetic analyses support their distinction although more specimens of both species will allow better refinement of their uniqueness.
Article
Diagnostic dinosaur fossils of the southeastern United States are rare discoveries, and even more precious are those fossils that preserve a large portion of a skeleton. Sixty years ago, the dinosaur Lophorhothon atopus was described from Upper Cretaceous sediments of Alabama. It then represented the oldest, most complete, dinosaur in the southeast United States. Based on a reexamination of the holotype material and a new specimen collected from the same beds, we provide a new diagnosis of this taxon. In particular, the solid nasal crest has several autapomorphies including caudally projecting frontal processes that are oval in cross-section, meaning that they did not coalesce at the midline. Other autapomorphies are found on the prefrontal and squamosal. Combining the two Lophorhothon specimens provides nearly the entire skeleton for phylogenetic analysis, which we find as a hadrosauromorph just outside of Hadrosauridae. The original diagnosis of this taxon included the frontonasal fontanelle as a distinguishing character, but comparing the many examples of frontonasal openings across hadrosauromorph taxa shows that in at least a few species, such as Lophorhothon , the structures should be considered a frontonasal fenestra instead of a fontanelle. Additionally, the notion that dinosaurs from the East Coast of the United States represent primitive relicts is an idea that originated before many of the European and Asian hadrosauromorphs known today had been discovered. With new dating and phylogenetic information, it appears that Appalachian dinosaurs are on par evolutionarily with most of the global community and the term ‘relict fauna’ should be abandoned.
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Although only recognized as a discrete stratigraphic unit since 1944, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This field guide represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence stratigraphy, chemostratigraphy, and biostratigraphy of these medial Mesozoic strata that document the dynamic and complex geological history of this region. Additionally, these data provide a framework by which to examine the history of terrestrial faunas during the final breakup of Pangaea. In fact, the medial Mesozoic faunal record of eastern Utah should be considered a keystone in understanding the history of life across the northern hemisphere. Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
Article
Full-text available
Although only recognized as a discrete stratigraphic unit since 1944, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This field guide represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence stratigraphy, chemostratigraphy, and biostratigraphy of these medial Mesozoic strata that document the dynamic and complex geological history of this region. Additionally, these data provide a framework by which to examine the history of terrestrial faunas during the final breakup of Pangaea. In fact, the medial Mesozoic faunal record of eastern Utah should be considered a keystone in understanding the history of life across the northern hemisphere. Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
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The diagnosis of the hadrosaurine Wulagasaurus dongi is revised in this paper, based on both original and new material recovered from the Upper Cretaceous Yuliangzi Formation at the Wulaga locality in Heilongjiang Province, China. However, we also demonstrate that some specimens previously referred to W. dongi, including braincases, maxillae and scapulae, actually belong to typical lambeosaurines. Wulagasaurus shares strong morphological similarities with the North American taxa Brachylophosaurus and Maiasaura: a long, wedge-shaped rostral apex positioned at the level of the dorsoventral midpoint of the jugal rostral ramus; a fan-shaped caudal ramus of the jugal with a nearly straight or slightly convex caudal margin; a relatively elongate and slender ventral process of the coracoid; a weakly developed humeral deltopectoral crest that is moderately expanded craniolaterally; and an asymmetrical, strongly convex margin of the iliac supracetabular process, lacking a strong ridge connecting its caudal portion with the dorsal margin of the postacetabular process. Phylogenetic analysis indicates that Wulagasaurus, Brachylophosaurus and Maiasaura form a monophyletic basal clade of hadrosaurines. This basal clade originated in Asia during the Santonian age of the Late Cretaceous. No later than the middle Campanian, the lineage split and then dispersed via the Bering land bridge to North America, where Brachylophosaurus and Maiasaura diverged from one another.
Article
A new species of the hadrosaurine hadrosaurid Gryposaurus was discovered in the late Campanian Kaiparowits Formation of southern Utah. Gryposaurus monumentensis, sp. nov. is distinguished from other Gryposaurus species by possessing a more robust skull, enlarged clover-shaped prongs on the predentary oral margin, an anteroposteriorly narrow infratemporal fenestra, and other autapomorphies plausibly associated with feeding adaptations. The derived morphology revealed in G. monumentensis necessitates revision of the generic diagnosis of Gryposaurus, including the addition of synapomorphies that further aid in distinguishing this taxon from Kritosaurus. A revised phylogenetic analysis places Gryposaurus within a monophyletic clade that includes Brachylophosaurus and Maiasaura. Gryposaurus monumentensis represents the most southern example of Gryposaurus, and underlines the remarkable diversification and long duration of this genus. Based on the phylogenetic, geographical, and stratigraphic evidence at hand, Gryposaurus was the most diverse genus within Hadrosaurinae; it also possessed one of the largest geographical and stratigraphic distributions, spanning more than five million years of the Campanian, and ranging from Alberta in the north to Utah (and possibly Texas) in the south. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 151, 351–376.
Chapter
More is known about hadrosaurids than about virtually any other group of dinosaurs. Remains are often abundant and range from fully articulated skeletons (sometimes complete with sclerotic rings, stapes, hyoids, and ossified tendons) to disartic-ulated and isolated material. In addition, remains of eggs, embryos , hatchlings (perinates), and juveniles, as well as footprints and trackways, skin impressions, and coprolites have provided investigators with glimpses of dinosaur biology that are not generally afforded for other groups of dinosaurs. Hadrosaurids, the so-called duck-billed dinosaurs, were large (7–12 m long, average adult body weight 3,000 kg) and had broad edentulous beaks, long, low skulls, and complex dentitions organized into dental batteries. Of this group, lambeosaurines exhibit radical modifications and elaborations of the nasal cavity, which is moved from the front of the face to a supraorbital position. Hadrosaurids were the most diverse and abundant large vertebrates of Laurasia during the closing stages of the Late Cre-taceous (table 20.1). They were also the last major clade of ornithopods to evolve in the Mesozoic (as early as the Ceno-manian, based on Protohadros), and they show a number of remarkable anatomical characteristics in their dentition and facial skeleton, which have attracted considerable research attention relating particularly to feeding mechanisms and strategies and to social behavior.
Article
Prosaurolophus maximus Brown is a saurolophine hadrosaurid known from numerous complete, articulated skulls from the Dinosaur Park Formation (Campanian, Alberta, Canada) that range in size by approximately half a metre in total skull length. Therefore, it is an important taxon for understanding patterns of growth and variation in saurolophines. This study describes the cranial anatomy of P. maximus from the type locality of Dinosaur Provincial Park (Dinosaur Park Formation: Campanian) on the basis of ten articulated skulls, quantitatively examines its range of osteological variation, and provides the first hypothesized ontogenetic series for this taxon. A second species, Prosaurolophus blackfeetensis Horner, was named on the basis of geologically younger material from Montana (Two Medicine Formation: Campanian) that is diagnosed by putative morphological differences in the nasal crest. However, considerable nasal crest variation in the sample from the Dinosaur Park Formation does not permit quantitative differentiation of P. blackfeetensis from P. maximus. Furthermore, a species-level phylogenetic analysis of saurolophines that includes both P. maximus and P. blackfeetensis as originally defined recovers them as sister taxa that do not differ morphologically in the character matrix. Based on both the morphometric and phylogenetic data, this study supports the hypothesis that P. blackfeetensis is a junior synonym of P. maximus, thereby substantially increasing its temporal range to 1.6 million years, and a concomitant period of morphological stasis in this taxon. © 2013 The Linnean Society of London
Article
The osteology of the hadrosaurid dinosaur Kritosaurus navajovius (late Campanian of southern North America) is documented in detail, and the taxonomy and phylogenetic relationships of the genus are revised. Kritosaurus is rediagnosed based on the extensive length of the dorsolateral margin of the maxilla and a unique combination of characters that includes a jugal with orbital constriction deeper than infratemporal one, infratemporal fenestra greater than orbit and with dorsal margin greatly elevated above dorsal orbital margin in adults, frontal participating in orbital margin, and paired caudal parasagittal processes of nasals resting over frontals. The taxonomy of numerous hadrosaurid specimens previously referred to Kritosaurus is reassessed; the vast majority of these cannot be positively referred to Kritosaurus. One exception is a specimen collected from the Cerro del Pueblo Formation that extends the geographical range of K. navajovius further south in Laramidia, to present-day northern Mexico. Anasazisaurus is regarded a junior synonym of Kritosaurus; their holotypes are indistinguishable from each other when considering the overlapping elements. However, many characters support distinction of Naashoibitosaurus ostromi as a valid taxon. Kritosaurus, consisting of the sister species K. navajovius and K. horneri, is deeply nested within Saurolophinae as a member of Kritosaurini. The latter clade includes also Naashoibitosaurus, Gryposaurus, and the South American Secernosaurus. Kritosaurini is characterized by a rostral nasal dorsal process not reaching the rostral margin of the narial foramen, frontal with triangular rostrolateral projection ending in a narrow apex (convergent in Brachylophosaurini), and a subrectangular dorsal region of infratemporal fenestra, among other characters. Kritosaurin hadrosaurids are hypothesized to have originated in southern Laramidia no later than the early Campanian. Subsequently, members of the clade reached northern Laramidia and South America via dispersal no later than the early and late Campanian, respectively.