An unusual new basal iguanodont (Dinosauria: Ornithopoda) from the Lower Cretaceous of Teruel, Spain

Abstract

We describe a new basal iguanodont, Proa valdearinnoensis, from the Lower Cretaceous (lower Albian) Escucha Formation of Teruel Province, Spain. The new taxon is known from abundant cranial and postcranial material belonging to several individuals, and is distinguished by an autapomorphy (predentary comes to a point at its rostral margin, with divergent lateral processes) and a unique combination of characters. Proa fills part of an otherwise lengthy temporal gap (early Aptian-Santonian) in the European fossil record of basal iguanodonts. A preliminary phylogenetic analysis places Proa in a polytomy with Iguanodon bernissartensis and more derived iguanodontians (Hadrosauroidea). Proa is more basal than the Valanginian Hypselospinus and late Barremian-early Aptian Mantellisaurus, suggesting a long ghost lineage leading to Proa.

Full text

Accepted by R. Benson: 31 Oct. 2012; published: 21 Month 2012
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Copyright © 2012 · Magnolia Press
Zootaxa 3595: 61–76 (2012)
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An unusual new basal iguanodont (Dinosauria: Ornithopoda) from the Lower
Cretaceous of Teruel, Spain
ANDREW T. MCDONALD1, EDUARDO ESPÍLEZ2, LUIS MAMPEL2, JAMES I. KIRKLAND3
& LUIS ALCALÁ2
1Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, USA. Email:
mcandr@sas.upenn.edu
2Fundación Conjunto Paleontológico de Teruel-Dinópolis (Museo Aragonés de Paleontología), Teruel, Spain. Email: espilez@funda-
ciondinopolis.org, mampel@fundaciondinopolis.org, alcala@fundaciondinopolis.org
3Utah Geological Survey, Salt Lake City, Utah, USA. Email: jameskirkland@utah.gov
Abstract
We describe a new basal iguanodont, Proa valdearinnoensis, from the Lower Cretaceous (lower Albian) Escucha
Formation of Teruel Province, Spain. The new taxon is known from abundant cranial and postcranial material belonging
to several individuals, and is distinguished by an autapomorphy (predentary comes to a point at its rostral margin, with
divergent lateral processes) and a unique combination of characters. Proa fills part of an otherwise lengthy temporal gap
(early Aptian–Santonian) in the European fossil record of basal iguanodonts. A preliminary phylogenetic analysis places
Proa in a polytomy with Iguanodon bernissartensis and more derived iguanodontians (Hadrosauroidea). Proa is more
basal than the Valanginian Hypselospinus and late Barremian-early Aptian Mantellisaurus, suggesting a long ghost
lineage leading to Proa.
Key Words: Proa valdearinnoensis gen. et sp. nov., Iguanodontia, Early Cretaceous, Escucha Formation, Spain
Introduction
The European fossil record of basal, or non-hadrosaurid, members of Iguanodontia is among the richest on Earth
(Norman 2004, 2012) and is the first to have been described (Mantell 1825). The most copious European basal
iguanodont remains come from Lower Cretaceous strata. England is particularly bountiful, with an extensive basal
iguanodont record that spans the early Berriasian through the early Aptian, approximately 25 million years
(Norman 2004, 2012; Walker & Geissman 2009); this record includes Owenodon hoggii (Norman & Barrett 2002;
Galton 2009, 2012; Norman 2012), Barilium dawsoni (Norman 2010, 2011, 2012), Hypselospinus fittoni (Norman
2010, 2012), Kukufeldia tilgatensis (McDonald et al. 2010a), Iguanodon bernissartensis (Norman 1980, 2012;
McDonald 2012a), Mantellisaurus atherfieldensis (Hooley 1925; Norman 1986, 2012; Paul 2006; McDonald
2012a), and Valdosaurus canaliculatus (Galton & Taquet 1982; Galton 2009, 2012; Barrett et al. 2011).
Furthermore, complete skeletons of Iguanodon bernissartensis and Mantellisaurus atherfieldensis are known from
the Bernissart Quarry in Belgium (Norman 1980, 1986, 2012; McDonald 2012a).
Concerning Spain, Early Cretaceous iguanodont remains were cited early on by Vilanova Piera (1872, 1873) in
the first Spanish reference dealing with dinosaurs. Spain has recently produced abundant fossils of Early
Cretaceous basal iguanodonts; for a comprehensive review, see Pereda-Suberbiola et al. (2012). However, only one
new taxon of basal iguanodont has been named based upon material from Spain: Delapparentia turolensis, which is
known from a single incomplete skeleton from the lower Barremian Camarillas Formation of Teruel Province
(Ruiz-Omeñaca 2011).
Here, we describe a new basal iguanodont from lower Albian beds in the upper Aptian–lower Albian
Escucha Formation (Rodríguez-López et al. 2009) of Teruel Province. Canudo et al. (2005) previously
reported very fragmentary vertebral remains of an indeterminate basal iguanodont from the Escucha

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Formation. However, the new taxon we describe is known from plentiful material of multiple individuals,
including at least one nearly complete disarticulated but associated skull. The new taxon possesses a single
autapomorphy and a unique combination of features that serve to distinguish it. In this preliminary paper, we
offer a cursory anatomical description and comparison with other basal iguanodonts, and place the new taxon
in a global phylogenetic analysis. Much additional material of the new taxon is still undergoing excavation and
preparation; once these tasks are complete, the entire known anatomy of the new taxon will be described in
detail.
Institutional Abbreviations
CEUM Prehistoric Museum, Price, UT, USA
MAP Museo Aragonés de Paleontología (Fundación Conjunto Paleontológico de Teruel-Dinópolis),
Teruel, Spain
MIWG Dinosaur Isle Museum (formerly Museum of Isle of Wight Geology), Sandown, UK
NHMUK The Natural History Museum (formerly NHM and BMNH), London, UK
SDSM South Dakota School of Mines and Technology, Rapid City, SD, USA
YPM Yale Peabody Museum of Natural History, New Haven, CT, USA.
Systematic Paleontology
Dinosauria Owen 1842
Ornithischia Seeley 1887
Ornithopoda Marsh 1881
Iguanodontia Dollo 1888 (sensu Sereno 2005)
Styracosterna Sereno 1986 (sensu Sereno 2005)
Ankylopollexia Sereno 1986 (sensu Sereno 2005)
Hadrosauriformes Sereno 1997 (sensu Sereno 1998)
Proa valdearinnoensis gen. et sp. nov.
Etymology. The generic name is the Spanish word for prow (‘proa’), in reference to the pointed shape of the
predentary. The specific name is in reference to Val de Ariño, the traditional name of the coal mining area around
the municipality of Ariño, near which the fossils were discovered, with the Latin ending -ensis (‘from’).
Holotype. AR-1/19 (deposited at MAP), a partial skeleton consisting of a disarticulated but associated skull
including the premaxillae, partial maxillae, quadrates, supraorbitals, articulated braincase and skull roof,
predentary, left dentary, and partial right surangular (AR-1-2012); right dentary (AR-1-2013); an isolated tooth
(AR-1-2014); and several unprepared postcranial bones.
Paratype. AR-1/48 (deposited at MAP), a disarticulated but associated skull (AR-1-1364, AR-1-1367, AR-1-
1373–AR-1-1376, AR-1-1380, AR-1-1382, AR-1-1384–AR-1-1386, AR-1-1388, AR-1-1395), right dentary (AR-
1-1365, AR-1-1366), a left dentary (AR-1-1383), and six isolated teeth (AR-1-1369–AR-1-1372, AR-1-1378, AR-
1-1379).
Referred Material. AR-1/57, a disarticulated but associated skull and dentary; AR-1/58 and AR-1/70, two
partial skeletons. All referred material is deposited at MAP. Much of this material is still being prepared.
Locality and Horizon. Site AR-1 (bone concentrations AR-1/19, AR-1/48, AR-1/57, AR-1/58, AR-1/70),
Mina Santa María, Ariño, Teruel Province, Spain. Middle Interval with Coal, Lower Sedimentary Succession,
Escucha Formation (Rodríguez-López et al. 2009), lower Albian (Alcalá et al. 2012; Tibert et al. in prep.).

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FIGURE 1. Premaxillae and maxilla of Proa valdearinnoensis. Articulated premaxillae of AR-1-2012 (holotype) in ventral
(A), dorsal (B), and left lateral (D) views. Articulated premaxillae of Dakotadon lakotaensis (SDSM 8656, holotype) in dorsal
(C) view. Left maxilla AR-1-1388 (paratype) in lateral (E) and medial (F) views. Abbreviations: aof, antorbital fossa; ap,
ascending process; fo, fossa; jp, jugal process; md, marginal denticles; rm, rostral margin; rvp, rostroventral process; sf, special
foramina; vlp, ventrolateral process. Scale bars equal 10 cm.

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Diagnosis of genus and species by monotypy. Diagnosed by a single autapomorphy: predentary comes to a
point at its rostral margin, with divergent lateral processes. Also diagnosed by the following unique combination of
characters: dentary tooth row is convex dorsally in lateral view (otherwise known in only Owenodon hoggii
[Galton 2009], and this might be due to crushing [Norman 2012]; if so, this feature would be another
autapomorphy of Proa); dentary tooth row extends caudal to the base of the coronoid process; platform between
the dentary tooth row and the base of the coronoid process; coronoid process expanded along rostral and caudal
margins; maxilla lacks a rostrodorsal process; quadrate straight in lateral view; ilium with dorsal margin convex
dorsally, non-pendant supraacetabular process, and postacetabular process that tapers without a break in slope
along its dorsal margin; cranial pubic process concave along its dorsal margin but lacks expansion of distal end.
Description. Each premaxilla bears two rostrocaudally elongated denticles, as in Dakotadon (SDSM 8656),
Iguanodon (Norman 1980), and Mantellisaurus (NHMUK R5764; Norman 1986); between the two denticles is a
deep circular fossa (Fig. 1A). The premaxillae are slightly expanded transversely, giving the rostral margin of the
oral cavity a rounded shape in dorsal view (Fig. 1B); this is similar to other styracosternans such as Dakotadon
(Fig. 1C) (SDSM 8656; Weishampel & Bjork 1989) and Iguanodon (Norman 1980), although the premaxillae of
Proa taper more towards their rostral ends (Fig. 1B). The caudoventral corner of the rostral margin is a broad,
gentle curve comparable to those of Dakotadon (Weishampel & Bjork 1989), Iguanodon (Norman 1980), and
Mantellisaurus (Norman 1986). The ventrolateral process of the premaxilla is extremely robust and gradually
expands dorsoventrally towards its caudal end (Fig. 1D).
The maxilla lacks a rostrodorsal process, as in Fukuisaurus (Kobayashi & Azuma 2003). The rostroventral
process of the maxilla projects rostrally (Fig. 1E). The ventral margin of the tooth row is gently concave. The
ascending process of the maxilla is rostrocaudally broad and subtriangular with a rounded apex in lateral view (Fig.
1E). The caudal margin of the ascending process bears a small semicircular depression, a remnant of the antorbital
fossa, as in Iguanodon (Norman 1980), Mantellisaurus (NHMUK R5764; Norman 1986), and Ouranosaurus
(Taquet 1976). Caudoventral to the base of the ascending process on the lateral surface of the maxilla is a shelf that
would have been overlapped by the maxillary process of the jugal, forming a ‘scarf’ contact as in Hippodraco
(McDonald et al. 2010b), Iguanacolossus (McDonald et al. 2010b), Dakotadon (SDSM 8656; Weishampel &
Bjork 1989), and Fukuisaurus (Kobayashi & Azuma 2003). A row of ‘special foramina’ forms an arch dorsal to the
tooth row on the medial surface of the maxilla (Fig. 1F).
The lateral wing of the quadrate bears a semicircular quadratojugal notch (Fig. 2A, B), as in many other basal
iguanodonts, such as Iguanacolossus (McDonald et al. 2010b), Lurdusaurus (Taquet & Russell 1999), Fukuisaurus
(Kobayashi & Azuma 2003), Iguanodon (Norman 1980), Mantellisaurus (Norman 1986), Ouranosaurus (Taquet
1976), and Jinzhousaurus (Barrett et al. 2009). The medial wing of the quadrate is a broad triangular flange that
projects rostrally to contact the pterygoid (Fig. 2C). The quadrate is straight in lateral view (Fig. 2A, B), as in
Iguanacolossus (McDonald et al. 2010b), Lurdusaurus (Taquet & Russell 1999), Fukuisaurus (Kobayashi &
Azuma 2003), Iguanodon (Norman 1980), and Protohadros (Head 1998). The dorsal condyle is subtriangular, with
a broader rostral margin and tapering towards the caudal margin (Fig. 2D). The ventral condyle of the quadrate is
rostrocaudally compressed and mediolaterally wide with an enlarged lateral condylar surface (Fig. 2E).
Two exceptionally well preserved braincases are known for Proa; that of the holotype, AR-1-2012, is briefly
described herein. This specimen includes not only the complete uncrushed braincase and skull roof, but also the left
postorbital and squamosal. The postorbital forms the caudodorsal margin of the orbit and consists of a central
portion and three processes: a medially-projecting platform that contacts the frontal, a rostroventrally-directed
process that meets the jugal, and a caudally-directed process that contacts the squamosal to form the dorsal margin
of the infratemporal fenestra and the lateral margin of the supratemporal fenestra (Fig. 3A–D). The caudal end of
the squamosal process is rounded, as in Hippodraco (McDonald et al. 2010b), Mantellisaurus (Norman 1986),
Ouranosaurus (Taquet 1976), Altirhinus (Norman 1998), Jinzhousaurus (Barrett et al. 2009), Equijubus (You et al.
2003b), and Xuwulong (You et al. 2011). The squamosal exhibits a deep glenoid to receive the dorsal condyle of
the quadrate, bounded rostrally by the prequadrate process and caudally by the longer postquadrate process (Fig.
3A, B). Rostral to the glenoid is the rostrally-directed postorbital process. Medial to the glenoid, the caudomedial
process of the squamosal curves rostromedially; the articulated left squamosal and contact surface for the right
squamosal on the parietal indicate that the squamosals were separated by only a narrow sliver of the parietal (Fig.
3C, D), as in Jinzhousaurus (Barrett et al. 2009), Jintasaurus (You & Li 2009), Probactrosaurus (Norman 2002),
Eolambia (McDonald et al. 2012), and Bactrosaurus (Godefroit et al. 1998).

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FIGURE 2. Quadrate of Proa valdearinnoensis. Left quadrate of AR-1-2012 (holotype) in lateral (A), tracing in lateral (B),
medial (C), dorsal (D), and ventral (E) views. Abbreviations: bf, bone fragment; dc, dorsal condyle; lcs, lateral condylar
surface; mw, medial wing; qjn, quadratojugal notch; vc, ventral condyle. Scale bars equal 10 cm.
The frontal forms part of the dorsal margin of the orbit (Fig. 3A–D). The laterosphenoid curves laterally to
meet the medial surface of the postorbital (3C, D). The supraoccipital is excluded from the foramen magnum by the
left and right exoccipitals (Fig. 3E, F). The paroccipital process is pendant and ventrally directed (Fig. 3A, B, E, F),
as in Hippodraco (McDonald et al. 2010b), Iguanodon (Norman 1980), Bolong (Wu & Godefroit 2012),
Jintasaurus (You & Li 2009), and Probactrosaurus (Norman 2002), but in contrast to the rostrally curved process
of Ouranosaurus (Taquet 1976). The basipterygoid processes project ventrolaterally and curve caudally along their
lengths. Caudal to the bases of the basipterygoid processes are the rugose basal tubera (Fig. 3A, B). The occipital
condyle is directed caudoventrally (Fig. 3A). The foramen magnum is formed entirely by the exoccipitals, without
participation of the basioccipital (Fig. 3E, F).
The predentary of Proa is unique among iguanodontians in its overall shape; the lateral processes diverge from
each other and the predentary comes to a point at its rostral margin (Fig. 4A). This morphology is reminiscent of
the predentaries of non-iguanodontian ornithischians such as Lesothosaurus (Sereno 1991), Haya (Makovicky et
al. 2011), and Hypsilophodon (Galton 1974). In other iguanodontians, the predentary is arcuate, with a broad,
rounded rostral margin and rounded rostrolateral corners (Fig. 4B–F). The unusual morphology of the predentary
of Proa, in conjunction with the tapered premaxillae described above, suggests a feeding ecology different from
those of other basal iguanodonts. In other features, the predentary of Proa is similar to those of other basal
iguanodonts. There are two grooves on the rostral margin of the predentary, one on either side of the median
marginal denticle (Fig. 5A). The ventromedial process is bifurcated (Fig. 5B, C). The dorsomedial process is a
short, caudally-projecting prong that arises caudodorsal to the base of the ventromedial process (Fig. 5D). The
predentary bears a large conical median denticle with a large denticle on either side of it and smaller denticles along
the lateral processes (Fig. 5A), as in Dakotadon (SDSM 8656; Weishampel & Bjork 1989), Iguanodon (Norman
1980), Mantellisaurus (Norman 1986), and Ouranosaurus (Taquet 1976).

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FIGURE 3. Braincase of Proa valdearinnoensis. Articulated skull roof and braincase of AR-1-2012 (holotype) in left lateral
(A), left lateral tracing (B), dorsal (C), dorsal tracing (D), caudal (E), and caudal tracing (F) views. Abbreviations: bbpt, base of
basipterygoid process; boc, basioccipital; bt, basal tubera; cmp, caudomedial process of squamosal; fm, foramen magnum;
lexo, left exoccipital; lf, left frontal; llsp, left laterosphenoid; lop-exo, left fused opisthotic and exoccipital; lpo, left postorbital;
lpoc, left paroccipital process; lpro, left prootic; lsq, left squamosal; nuc, nuchal crest; oc, occipital condyle; orf, orbital rim of
frontal; p, parietal; poc, paroccipital process; poq, postquadrate process; prq, prequadrate process; ps-bsp, fused parasphenoid
and basisphenoid; psp, parasphenoid process; rbpt, right basipterygoid process; rexo, right exoccipital; rf, right frontal; rlsp,
right laterosphenoid; rpoc, right paroccipital process; rpro, right prootic; rsq/p, contact surface on parietal for right squamosal;
rsq/rexo, contact surface on right exoccipital for right squamosal; sgc, sagittal crest; soc, supraoccipital; stf, supratemporal
fenestra. Scale bar equals 10 cm.

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FIGURE 4. Predentary of Proa valdearinnoensis (AR-1-2012, holotype) in dorsal (A) view. Predentaries of Zalmoxes robustus
(B, NHMUK R3410), Camptosaurus dispar (C, YPM PU14553; image copyright YPM), Dakotadon lakotaensis (D, SDSM
8656, holotype, missing left half), Mantellisaurus atherfieldensis (E, MIWG 6344), and Eolambia caroljonesa (F, CEUM
35742) in dorsal view. Scale bars equal 1 cm.
In dorsal view, the dentary tooth row is straight from the first alveolus to approximately the twelfth, at which
point it curves caudolaterally towards the base of the coronoid process (Fig. 6A). The dentary tooth row is convex
dorsally in lateral and medial views (Fig. 6B, C), a feature otherwise observed in only Owenodon (NHMUK
R2998; Galton 2009), though this morphology might be due to crushing in the latter case (Norman 2012). The
dentary tooth row extends caudally past the base of the coronoid process (Fig. 6C), as in hadrosaurids (Horner et al.
2004) but in contrast to other non-hadrosaurid iguanodontians, such as Mantellisaurus (Norman 1986),
Ouranosaurus (Taquet 1976), Altirhinus (Norman 1998), Probactrosaurus (Norman 2002), and Jeyawati
(McDonald et al. 2010c); this feature appears to have evolved independently in Proa. The alveoli mirror the shape
of the dentary teeth as in Iguanodon (Norman 1980), Mantellisaurus (Norman 1986), Ouranosaurus (Taquet
1976), and Altirhinus (Norman 1998), and in contrast to the alveoli formed by parallel vertical walls in
Probactrosaurus (Norman 2002), Eolambia (McDonald et al. 2012), Jeyawati (McDonald et al. 2010c),
Protohadros (Head 1998), Shuangmiaosaurus (You et al. 2003a), Bactrosaurus (Godefroit et al. 1998), Levnesovia
(Sues & Averianov 2009), Telmatosaurus (Weishampel et al. 1993), and hadrosaurids (Horner et al. 2004). The
dorsal and ventral margins of the dentary are parallel, and the ventral margin is inflected ventrally towards the
symphysis (Fig. 6B, C). The coronoid process is laterally offset from the tooth row by a narrow shelf, as in
Altirhinus (Norman 1998), Probactrosaurus (Norman 2002), Jeyawati (McDonald et al. 2010c), Protohadros
(Head 1998), Shuangmiaosaurus (You et al. 2003a), Bactrosaurus (Godefroit et al. 1998), and hadrosaurids
(Horner et al. 2004). The vertical coronoid process is rostrocaudally expanded along its rostral and caudal margins
as in Altirhinus (Norman 1998), Probactrosaurus (Norman 2002), and Bactrosaurus (Godefroit et al. 1998) (Fig.
6B, C).
The maxillary teeth bear a distally offset primary ridge with multiple fainter accessory ridges mesial and distal
to it (Fig. 7A). Unworn dentary teeth bear parallel secondary and distally offset primary ridges of similar
prominence with multiple faint accessory ridges arising from the marginal denticles (Fig. 7B). There appears to be
only one replacement tooth per dentary alveolus, and only one active tooth participating in the occlusal plane.
The preacetabular process of the ilium terminates in a horizontal boot (Fig. 8A), as in many other styracosternans,
including Iguanacolossus (McDonald et al. 2010b), Cedrorestes (Gilpin et al. 2006), Barilium (Norman 2011),
Iguanodon (Norman 1980), Mantellisaurus (Hooley 1925; Norman 1986; McDonald 2012a), and Eolambia

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(McDonald et al. 2012). The dorsal margin of the ilium is strongly convex dorsally (Fig. 8A), as in Barilium (Norman
2011), Iguanodon (Norman 1980), Bolong (Wu & Godefroit 2012), and Equijubus (You et al. 2003b). Dorsal to the
ischial peduncle, the dorsal margin of the ilium expands laterally to form a bulbous, non-pendant supraacetabular shelf
(Fig. 8A), as in Bactrosaurus (Godefroit et al. 1998) and Gilmoreosaurus (Prieto-Márquez & Norell 2010). This
structure appears to have evolved convergently in Proa, as other, more derived styracosternans, such as
Mantellisaurus (Norman 1986), Ouranosaurus (Taquet 1976), Xuwulong (You et al. 2011), and Probactrosaurus
(Norman 2002), possess only a thickened laterally-everted rim at this location on the ilium. The postacetabular
process tapers caudally with no break in slope along its dorsal margin, as in Iguanodon (Norman 1980).
FIGURE 5. Predentary of Proa valdearinnoensis (AR-1-2012, holotype) in rostral (A), ventral (B), caudal (C), and right lateral
(D) views. Abbreviations: dm, dorsomedial process; md, marginal denticle; mmd, median marginal denticle; rg, rostral groove;
vm, ventromedial process. Scale bar equals 1 cm.
The cranial pubic process of the pubis is remarkably similar to those of Camptosaurus (YPM 7334; McDonald
2011: fig. 5), Uteodon (Carpenter & Wilson 2008; McDonald 2011), and Iguanacolossus (McDonald et al. 2010b);
the process is concave along its dorsal margin but its distal end is not expanded (Fig. 8B). The morphology of the
cranial pubic process of Proa is in strong contrast to the broadly expanded processes of Lanzhousaurus (You et al.
2005), Iguanodon (Norman 1980), Mantellisaurus (Hooley 1925; Norman 1986), Delapparentia (Ruiz-Omeñaca
2011), Ouranosaurus (Taquet 1976), Xuwulong (You et al. 2011), Probactrosaurus (Norman 2002); and Eolambia
(McDonald et al. 2012).
The intercondylar extensor groove of the femur is a canal that is fully enclosed by expansion and fusion of the lateral
and medial distal femoral condyles (Fig. 8C, D), as in Bactrosaurus (Godefroit et al. 1998) and hadrosaurids (Horner et
al. 2004). The intercondylar flexor groove is partially enclosed by the lateral expansion of the medial condyle (Fig. 8C,
E). The distal half of the femoral shaft is straight in lateral and medial views (Fig. 8F). The fourth trochanter is
proximodistally broad and triangular, and arises at approximately the midpoint of the femoral shaft (Fig. 8E, F).

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FIGURE 6. Dentary of Proa valdearinnoensis (AR-1-1365, AR-1-1366, paratype) in dorsal (A), lateral (B), and medial (C)
views. Abbreviations: cma, caudal-most alveolus; cp, coronoid process; cvr, convex tooth row; sym, symphysis. Scale bars
equal 10 cm.

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FIGURE 7. Dentition of Proa valdearinnoensis. Maxillary teeth in left maxilla of AR-1-2012 (holotype) in labial (A) view.
Dentary teeth in right dentary AR-1-2013 (holotype) in lingual (B) view. Abbreviations: dar, distal accessory ridge; mar, mesial
accessory ridge; prr, primary ridge; sr, secondary ridge. Scale bars equal 1 cm.
Discussion
Proa fills part of a long temporal gap in the fossil record of European basal iguanodonts. Its early Albian age places
Proa several million years younger than other iguanodonts from Spain (Pereda-Suberbiola et al. 2012), Belgium
(Yans et al. 2012), and the extensive record of basal iguanodonts from England that spans the Berriasian through
the early Aptian (Norman 2012). The English record of basal iguanodonts is truncated in the early Aptian by the
inundation of epicontinental seas (Rawson 2006). Prior to the discovery of Proa, only fragmentary iguanodontian
fossils were known from Europe (Head 1998; Norman 2004) between Mantellisaurus in the early Aptian
(McDonald 2012a; Norman 2012) and Mochlodon vorosi from the Santonian of Hungary ( si et al. 2012). Proa
not only fits within this temporal gap, but by virtue of its well-preserved and extensive material, such as the nearly
complete holotype skull (Fig. 9), also adds substantial morphological information to the European iguanodont
record.
To explore its phylogenetic relationships, Proa was included in the global analysis of basal iguanodonts
recently published by McDonald (2012b: “Second Run”). Proa was coded for nearly all of the cranial, dental,
pelvic, and hind limb characters, but not for any of the vertebral, pectoral, or forelimb characters (Table 1); these
data will be available once preparation of the fossils is finished. With the addition of Proa, the matrix consisted of
67 taxa and 135 characters. The matrix was analyzed in TNT (Goloboff et al. 2008) using the same parameters as
the “Second Run” of McDonald (2012b): a traditional search was performed using the tree bisection reconnection
algorithm; all characters were equally weighted; 12 characters (10, 14, 20, 25, 46, 67, 81, 82, 83, 100, 127, 130)
were ordered; starting trees were Wagner trees with a random seed of 1; 9,999 replicates were used with 10 trees
saved per replication; and five OTUs (“Camptosaurus” valdensis, Draconyx, NHMUK R8676, Delapparentia, and
Glishades) were excluded through safe taxonomic reduction (Wilkinson 2001).

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TABLE 1. Character codings for Proa valdearinnoensis in the matrix of McDonald (2012b). Character numbers begin at
0, in the format of TNT.
This resulted in 24,460 most parsimonious trees (MPTs) of 396 steps each. As in McDonald (2012b), the strict
consensus cladogram was poorly resolved. There was a polytomy at the base of Iguanodontia that included
Rhabdodontidae (Muttaburrasaurus, Rhabdodon, (Zalmoxes robustus, Z. shqiperorum)), Tenontosaurus,
Callovosaurus, Dryosaurus, Kangnasaurus, and a clade with the topology (Dysalotosaurus, (Elrhazosaurus,
Valdosaurus)); the only resolution within more derived iguanodontians (Ankylopollexia) was a clade with the
topology (Bactrosaurus, (Shuangmiaosaurus, Tanius, Telmatosaurus, Claosaurus, Lophorhothon, Hadrosaurus,
Edmontosaurus, Corythosaurus)). The Adams consensus tree was obtained using PAUP (Swofford 2005) and is
more resolved (Fig. 10). The maximum agreement subtree was also calculated in PAUP, but Proa was among the
28 taxa excluded from the subtree.
In the Adams consensus tree, Proa appears at the base of Hadrosauriformes in a polytomy with Iguanodon and
a clade composed of more derived iguanodontians, i.e., Hadrosauroidea (sensu Sereno 2005) (Fig. 10). Proa is
more basal than the older European iguanodonts Hypselospinus (Valanginian [Norman 2012]) and Mantellisaurus
(late Barremian–early Aptian [McDonald 2012a; Norman 2012]), indicating a ghost lineage of approximately 25
million years leading to Proa. These results suggest a hitherto unrecognized diversity of basal hadrosauriforms in
the Early Cretaceous of Europe. The phylogenetic and biogeographic implications of Proa will be refined as
additional material is prepared and described, and as new material of other taxa and new taxa are added to the
phylogenetic analysis (McDonald et al. in prep.).
0–6, predentary
0 1 2 3 4 5 6
7–23, dentary
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
24–27, surangular and angular
24 25 26 27
0 0 1 1 1 0 1 0 1 0 1 2 0 0 4 1 1 0 1 1 1 1 1 0 ? ? 2 1
28–38, premaxilla and nasal
28 29 30 31 32 33 34 35 36 37 38
39–46, maxilla
39 40 41 42 43 44 45 46
47–52, lacrimal, prefrontal, and
postorbital
47 48 49 50 51 52
1 1 1 1 0 1 1 1 ? ? 1 0 0 1 1 2 1 1 2 ? ? ? ? ? 1
53–58, jugal and
quadratojugal
53 54 55 56 57 58
59–67, quadrate and squamosal
59 60 61 62 63 64 65 66 67 68–79, braincase
68 69 70 71 72 73 74 75 76 78 79
? ? ? ? ? ? 1 0 ? 2 0 0 0 0 1 0 1 0 0 1 0 0 0 0 1 1
80–92, teeth
80 81 82 83 84 85 86 87 88 89 90 91 92
93–95,
vertebrae
93 94 95
96–102, pectoral girdle
96 97 98 99 100 101 102
1 0 0 0 0 1 1 2 1 0 1 0 0 ? ? ? ? ? ? ? ? ? ?
103–108, forelimb
103 104 105 106 107 108 109–120, pelvic girdle
109 110 111 112 113 114 115 116 117 118 119 120
? ? ? ? ? ? 1 0 1 4 2 0 0 1 ? ? ? ?
121–130, hind limb
121 122 123 124 125 126 127 128 129 130 131–134, newly added in McDonald (2012b)
131 132 133 134
1 1 1 1 ? 1 4 1 ? ? 0 0 1 ?

MCDONALD ET AL.
72 · Zootaxa 3595 © 2012 Magnolia Press
FIGURE 8. Pelvic elements and femur of Proa valdearinnoensis. Left ilium AR-1-4413 (bone concentration AR-1-58) in
lateral (A) view. Left pubis AR-1-4439 (bone concentration AR-1-70) in lateral (B) view. Left femur AR-1-4370 (bone
concentration AR-1-58) in distal (C), cranial (D), caudal (E), and medial (F) views. Abbreviations: crp, cranial pubic process;
cxm, convex dorsal margin; ftr, fourth trochanter; hb, horizontal boot; ieg, intercondylar extensor groove; ifg, intercondylar
flexor groove; poap, postacetabular process; sap, supraacetabular process. Scale bars equal 10 cm.
FIGURE 9. Reconstructed skull of the holotype of Proa valdearinnoensis (AR-1-2012, AR-1-2013) in right lateral (A), rostral
(B), and left lateral (C) views. Scale bar equals 10 cm.

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NEW IGUANODONT FROM SPAIN
FIGURE 10. Adams consensus of 24,460 MPTs showing the phylogenetic relationships of Proa valdearinnoensis (highlighted
in blue). Placement of clade names at certain nodes follows the definitions of Sereno (2005).

MCDONALD ET AL.
74 · Zootaxa 3595 © 2012 Magnolia Press
Acknowledgments
We appreciate the ongoing collaboration of SAMCA Group staff and Ariño-based members, especially its
president, Ángel Luengo. This study is part of the paleontology research projects of the Departamento de
Educación, Universidad, Cultura y Deporte, Gobierno de Aragón and has been supported by its Dirección General
de Patrimonio Cultural (exp. 201/2010, 201/10-2011, 201/10-11-2012), DINOSARAGÓN CGL2009-07792 R&D
project (Ministerio de Ciencia e Innovación and FEDER Funds), FOCONTUR (Grupo de Investigación
Consolidado E-62, Departamento de Industria e Innovación, Gobierno de Aragón and Fondo Social Europeo),
Instituto Aragonés de Fomento, Fundación SAMCA, and Fundación Conjunto Paleontológico de Teruel-Dinópolis.
We thank all our colleagues who excavated in Ariño and prepared the fossils. The skull reconstruction and plate
were prepared by Daniel Ayala. ATM thanks the following people for access to specimens under their care: Jeff
Bartlett and John Bird (CEUM); Steve Hutt (Dinosaur Isle Museum); Paul Barrett, Sandra Chapman, and Lorna
Steel (NHMUK); Sally Shelton (SDSM); and Dan Brinkman (YPM). ATM’s research was funded by the Jurassic
Foundation, Evolving Earth Foundation, University of Pennsylvania Paleobiology Summer Stipend, and Utah
Friends of Paleontology. TNT is provided free by the Willi Hennig Society. Technical reviews by Don DeBlieux,
Mike Lowe, and Mike Hylland of the Utah Geological Survey are appreciated. This paper benefitted greatly from
reviews by Roger Benson, Peter Galton, and David Norman.
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