A new hadrosauroid ( Dinosauria : Ornithopoda ) from the Allen Formation ( Late Cretaceous ) of Patagonia , Argentina

A ne�� hadrosauroid taxon from the Late Cretaceous Allen Formation is erected, on the basis of abundant cranial and �ostcranial material from the Salitral Moreno locality of the Rio Negro Province, Argentina. The ne�� taxon is here named as Willinakaqe salitralensis gen. et s�. nov., ��hich is characterized by having an auta�omor�hous �remaxilla ��ith a long and convex rostrolateral surface rostral to the narial fossa and associated �ostcrania develo�ing an unique character combination, including: dorsal vertebrae ��ith a shallo�� fossa u�on the base of the transverse �rocesses; sacral and �roximal caudal neural s�ines more than three times the height of the centrum; distal region of the �ostacetabular �rocess of ilium ventrally deflected, among others. This ne�� hadrosauroid closely resembles Secernosaurus koerneri, the other valid hadrosauroid s�ecies from South America, based in several syna�omor�hies, as: angle greater than 115° bet��een the lateral margin of the facet for sca�ular articulation and the glenoid in the coracoid; su�ra-acetabular �rocess of the ilium asymmetrical, caudodorsal margin of ilium ��ith a ��ell-defined ridge continuous ��ith the dorsal margin of the �roximal region of the �ostacetabular �rocess. Moreover, �revious records of Lambeosaurinae from the Late Cretaceous of South America are referred to W. salitralensis, and thus, the �resence of lambeosaurines in this continent is here rejected. Accordingly, Willinakaqe salitralensis gen. et s�. nov. is currently the only hadrosauroid s�ecies re�orted from the Allen Formation.


MATERIALS AND METHODS
We follo�� the nomenclature and definition of the clades among Hadrosauroidea described by Prieto-Márquez (2010), and the suggestions of the second edition of the com�endium "The Dinosauria" by Weisham�el et al. (2004) regarding anatomical orientations.

Etymology.
The generic name is formed by the combination of the follo��ing ��ords of the Ma�uche language: willi meaning South, iná meaning mimic and kaqe meaning duck; the name thus meaning "the duck-mimic of the South".
Type species.The ty�e and only kno��n s�ecies of the genus is Willinakaqe salitralensis s�.nov.

Diagnosis.
As for the ty�e and only s�ecies (monoty�ic genus).
Occurrence.The materials corres�onding to the holoty�e, �araty�es and most referred s�ecimens of Willinakaqe salitralensis gen.nov.et s�.nov., housed at the Museo Provincial Carlos Ameghino, come from the southeastern region of the Salitral Moreno locality, in the north of the Río Negro �rovince, 20 km.south of the General Roca locality, Argentina (Fig. 1).These remains ��ere recovered in a single bone-bed together ��ith sauro�od and ankylosaurian remains (Salgado & Az�ilicueta, 2000;Coria & Salgado, 2001).The hadrosauroid remains are the most abundant in the assemblage, re�resenting individuals of different ontogenetic stages, ��ith estimated total lengths ranging bet��een one and 9 meters.The larger s�ecimens, as MPCA-Pv SM 2, dis�lay com-�letely fused centra and neural arches in dorsal vertebrae and here are thus considered as �resumable adult individuals (Irmis, 2007;Dalla Vecchia, ;Dalla Vecchia, 2009).Most of the �reserved cranial, axial and ).Most of the �reserved cranial, axial and a��endicular bones are re�resented by multi�le elements, including �artially articulated and closely associated �ieces.Because all of them corres�ond to a single mor�hoty�e, the contention that these belong to a single taxon in the site is su��orted.The referred material housed at the Museo Provincial de Historia Natural de La Pam�a, came from the Islas Malvinas locality, south��est of La Pam�a �rovince (Fig. 1).This s�ecimen, MPHN-Pv 01, is considered as belonging to Willinake salitralensis gen.et s�.nov.because it �reserves the same mor�hological traits, including these considered here as of diagnostic value in all the elements com�arable ��ith those from the ty�e locality (see belo��).Both localities, Salitral Moreno and Islas Malvinas, corres�ond to the lo��er section of the Allen Formation (Malargüe Grou�), of late Cam�anian -early Maastrichtian age (Andreis et al., 1974;Casadío, 1994).
Description.In the �resent study ��e describe the elements that �resent useful mor�hological traits for the taxonomical and �hylogenetic analysis of the s�ecies.Additional mor�hological traits of this taxon ��ere codified by Prieto-Márquez (2010) for inclusion in their data matrix ��here it is informally named as "Salitral Moreno OTU" and are briefly treated in the Discussion section.A more detailed anatomical descri�tion of Willinakaqe salitralensis gen.nov.et s�.nov.��ill be �ublished else��here.

Cranial skeleton
Premaxilla.This bone (MPCA-Pv SM 8; Fig. 3A, B) is the most distinctive element available for Willinakaqe salitralensis gen.et s�.nov.It dis�lays a suite of �lesiomor�hic and derived character states, ��hose combination is unique among Hadrosauroidea.Accordingly, this element ��as designed as the holoty�e of the ne�� taxon.The �remaxilla is almost com�lete, lacking the ventrolateral surface of the corner of the oral border and the caudal extremities of the caudodorsal and caudolateral �rocesses.The denticles are �oorly �reserved in the available material and it is not �ossible to assert if they ��ere as �rominent as in basal hadrosauroids, such as Telmatosaurus transsylvanicus (Weisham�el et al., 1993).Although a slight groove se�arates the denticle layer from the remaining �remaxillary ventral surface, an inner �alatal rim distinct from the denticle layer is not evident, as occurs in other saurolo�hids such as Prosaurolophus (Horner, 1992).In dorsal vie��, the oral and lateral margins are rounded and �oorly transversely ex�anded.This mor�hology is also �resent in the �rimitive forms Eolambia caroljonesa, Bactrosaurus johnsoni, and Telmatosaurus transsylvanicus, and is not so transversely ex�anded as in the saurolo�hines, nor ��ith the deflected rostroventral corner �resent in the lambeosaurines (Prieto Márquez et al., 2006).The area com�rised bet��een the oral margin and the rostroventral border of the circumnarial fossa is noticeably more extense than in basal forms like Eolambia, Telmatosaurus, or the lambeosaurines (Ostrom, 1961;Weisham�el et al., 1993;Head, 2001).This area may be considered homologous ��ith the area occu�ied by the external circumnarial fossa of the saurolo�hines, but Willinakaqe gen.nov.does not �resent the de�ression, nor the invaginated oral or lateral margins in this region, unlike the condition seen in Saurolo�hinae (Hadrosaurinae sensu Horner et al., 2004), and is considered as a �ossible auta�omor�hy of Willinakaqe salitralensis gen et s�.nov.(if not �resent also in near relatives such as Secernosaurus koerneri).A single foramen is �resent at the rostroventral end of the internal circumnarial fossa, ��hich �ierces the �remaxillary body and o�ens at the ventral surface of the bone.This character is not currently kno��n in any lambeosaurine, and is considered as a syna�omor�hy of the Saurolo�hinae (Horner et al., 2004;Prieto-Márquez, 2010).T��o additional foramina are �resent on the rostral region of the dorsal surface of the �remaxilla.At the caudal region of the �remaxilla, the �reserved �ortions of the caudodorsal and caudolateral �rocesses do not �resent evidence of enclosing the narial �assage, as occurs in lambeosaurines.Nevertheless, more com�lete skulls are necessary to confirm the latter assum�tion.
Maxilla.T��o almost com�lete maxillae ��ere recovered from the Salitral Moreno locality (MPCA-Pv SM 10 and 12, Fig. 3C-E); the first corres�onding �ossibly to an adult and the second to a subadult individual.This element is rostrocaudally elongated, ��ith a rostrocaudally symmetrical mor�hology.The dorsal �rocess of the maxilla is only slightly elevated, contrasting ��ith the derived condition �resent in Lambeosaurinae, in ��hich is dorsoventrally ��ell-develo�ed.In lateral vie��, a maxillary foramen is located belo�� the base of the dorsal �rocess and a second foramen is observed more caudally, ��ith a ventral orientation.Abbreviations in text.
Teeth.Multi�le teeth of Willinakaqe gen.nov.have been recovered adhered to some maxillae (MPCA-Pv 10 and 12) and dentaries (MPCA-Pv SM 3 and 4, Fig. 4B, C).Isolated dental elements are also �resent (MPCA-Pv SM 7 and 9), ��hich are tentatively associated to Willinakaqe salitralensis gen.et s�.nov.because of their close association to the remaining cranial and �ostcranial material, , and close similarity to the teeth �reserved in articulation ��ith bones.The dentary teeth are dis�osed in a dental battery ��ith three �ieces �er alveolus.In the most rostral dentary teeth (MPCA-Pv SM 4, Fig. 4C), there is a com�lete absence of denticulations.These rostral dentary teeth �resent a single central carina and are mesiodistally symmetrical.In o��osition, the teeth located in the middle and caudal section of the dental battery (MPCA-Pv SM 3) �resent small denticles on the distal borders.The mor�hology of these caudal dentary teeth is reminiscent to those found in the hadrosauroids from Antarctica described by Case et al. (2000) and some saurolo�hines (Horner et al., 2004).those of Secernosaurus in the �resence of a ��eak cavity located in the lateral face of the neural arc, u�on the base of the transverse �rocess (Fig. 5H).This trait is here considered as an auta�omor�hy of Willinakaqe salitralensis gen.et s�.nov.
Sacral and caudal vertebrae.An articulated series of t��enty five �roximal and medial caudal vertebrae, continuing the com�lete sacral sequence, is �resent in the s�ecimen MPCA-Pv SM 2 (Po��ell 1987, Fig. 2).Isolated caudals are also �resent in the Salitral Moreno (MPCA-Pv SM 23 to 25) and the Islas Malvinas material (MPHN-Pv 01, González Riga & Casadío 2000, Fig. 4F).The sacrum of an adult individual of Willinakaqe gen.nov., MPCN-Pv SM 2, is com�osed of eight fused vertebrae, as in Pararhabdodon isonense (Prieto-Márquez et al., 2006).This sacral number is lo�� in com�arison ��ith most saurolo�hids, ��hich �resent more than nine sacral vertebrae in adults (Horner et al., 2004).In Willinakaqe gen.nov., the first sacral vertebra �resents a ventral keel, but it is not �resent in the follo��ing sacrals.All the sacral vertebrae, as ��ell as the �roximal caudal vertebrae, dis�lay dorsoventrally ��ell-de-velo�ed neural s�ines, ��ith a height com�rising 4.8 times the centrum height in the first caudal of the articulated sequence (Po��ell, 1987, Figs 2, 3).Additional isolated vertebrae from the Salitral Moreno locality, MPCA-Pv SM 23 and 24 (Fig. 5I-K), are considered here as �roximal caudals due to the dorsal �rojection of their neural s�ines, and the similar ratio bet��een the centrum and the neural s�ine heights.The caudal vertebrae recovered in the Islas Malvinas locality (González Riga & Casadío, 2000) �reserve incom�lete neural s�ines, but the mor�hology of the centrum and neural arch is identical to that of the other elements belonging to Willinakaqe gen.nov (see belo��).Another character also described by Po��ell (1987) and �resent in all the available elements is the �rogressive distal ex�ansion of the neural s�ines, in both the �roximodistal (along the axis of the tail) and transverse �lanes.A slight �roximodistal (along the axis of the tail) constriction in the caudals at the base of the neural arch ��as observed by González Riga & Casadío (2000, Fig. 4F) in the Islas Malvinas material, and the same mor�hology is �resent in the caudal vertebrae from Salitral Moreno.These authors also noted the distinctive location of the �ostzyga�o�hysis, situated dorsal to the �rezyga�ho�hysis, a condition also seen in all kno��n s�ecimens of Willinakaqe gen.nov.By contrast, Secernosaurus koerneri �resents both zyga�ho�hyses at almost the same level.The centra of the �roximal caudal vertebrae are subcircular in contour in �roximal vie��, ��ith a convex ventral margin.Mid-and distal caudal vertebrae sho�� a sagittal sulcus at their ventral surface.

Appendicular skeleton
Scapula.This bone is re�resented by four s�ecimens, MPCA-Pv SM 2, 27, 28 and MPHN-Pv 01, the second of them being the most com�letely �reserved (Fig. 6A, B).The entire mor�hology of the bone can be assessed on the basis of the currently available material.As mentioned by Po��ell (1987), the sca�ular blade is slightly distally ex�anded in adult and subadult individuals, as in Secernosaurus koerneri and non-saurolo�hid taxa, such as Bactrosaurus and Telmatosaurus (Godefroit et al., 1998;Weisham�el et al., 1993).The distal border of the sca�ula is �er�endicular to the shaft.In the �roximal end, the sca�ula �resents a large and �rominent acromial bridge.A difference bet��een the sca�ulae of Willinakaqe salitralensis gen.et s�.nov.and Secernosaurus koerneri is �resent in the dorsal border of the �roximal region, ��hich in the former is almost straight, as �reviously noted for the Islas Malvinas material by González Riga & Casadío (2000).
Ilium.Three ilia have been recovered, MPCA-Pv SM 2, 39 and 40, of ��hich the first t��o are almost com�lete.The general mor�hology of this bone (Fig. 8) is com�arable to those of derived hadrosauroids, in the �resence of a deflection on the dorsal surface and the occurrence of a ��ell-develo�ed �ostacetabular �rocess.The su-�racetabular �rocess is ��ide and as re�orted by Po��ell (1987) for MPCA-Pv SM 2, and the distal rim slightly bo��s ventrolaterally.This results in a dorsally convex and ventrally concave antitrochanter.The �ostacetabular �rocess of the ilium is ��ide and �resents a distinctive caudoventral curvature at the distal region.The overall mor�hology of the ilium of Willinakaqe salitralensis gen.et s�.nov.more closely resembles that of Secernosaurus koerneri than that of other hadrosauroids (see belo��).
Femur.Five femora are �reserved.Com�lete femora re�resenting adult and subadult individuals are �reserved in MPCA-Pv SM 2, 42 and 43, ��ith sizes ranging from 35 centimeters to near a meter in �roximodistal length.The overall femoral mor�hology is similar to that of other hadrosauroids.There is no com�lete enclosure of the cranial intercondylar groove by the �rojections of the condyles (Fig. 9C, D), contrasting ��ith the condition �resent in Secernosaurus koerneri (Bona�arte & Rougier, 1987).The character does not a��ear to be ontogenetically variable in Willinakaqe gen.nov., because the o�en condition is �resent in all the subadult and adult s�ecimens.This character is considered as homo�lastic among hadrosauroids, but valid for s�ecific differentiation (Godefroit et al., 1998).

DISCUSSION AND CONCLUSIONS
Willinakaqe salitralensis gen.et s�.nov.and Secernosaurus koerneri exhibit several anatomical similarities, mainly sym�lesiomor�hies, but several of these allo�� differentiating these South American s�ecies from hadrosauroids less derived than Telmatosaurus transsylvanicus or Tanius sinensis, and from the different saurolo�hine and lambeosaurine subclades.Follo��ing to Prieto-Márquez (2010), Willinakaqe salitralensis gen.et s�.nov.can be included in the Saurolo�hidae and more inclusive clades among Hadrosauroidea on the basis of the follo��ing character states: location of the origin of the ventral deflection of the dentary near to the origin of the dental battery; bulging of the ventral lateral margin of the dentary straight or slightly bo��ed rostral to the coronoid �rocess; thick and dorsoventrally elongated ridge on the medial side of the coronoid �rocess absent; dentary lingual arching of the occlusal �lane absent, ��ith rostrocaudally straight occlusal �lane; length of the ecto�terygoid shelf relative to the total rostrocaudal length of the alveolar margin of the maxilla greater than 0.35; develo�ment of the �ostzyga�o�hyseal �roceses of cranial and middle cervical vertebrae three times or more longer than the breadth of the neural arch; length of the delto�ectoral crest of the humerus devel-o�ed greater than 55 �ercent of the �roximodistal length of the humerus; lateroventral ex�ansion of the delto�ectoral crest of the humerus ��ell ex-�anded; ventral margin of the delto�ectoral crest extending abru�tly from the humeral shaft to give a distinct angular �rofile; ventral deflection of the �reacetabular �rocess of the ilium ��ith an angle of less than 150°; su�raacetabular �rocess craniocaudally broad; mor�hology of the �ubic �eduncle of the ilium relatively short and triangular, ��ith a �roximal region that is craniocaudally much ��ider than the distal end; ischial �eduncle of the ilium formed by t��o �rotrusions of similar size; �ostacetabular �rocess of the ilium ��ith a caudodorsally oriented dorsal margin, rising dorsally relative to the acetabular margin; distal articular surface of the iliac �eduncle of the ischium cranially oriented; and acetabular and caudodorsal margins of the iliac �eduncle of the ischium becoming slightly to greatly divergent near the �roximal region of the �eduncle.Willinakaqe salitralensis gen.et s�.nov.also dis�lays the follo��ing syna�omor�hies of Saurolo�hinae: �resence of a �remaxillary foramen located rostrally and ventrolaterally to the rostral margin of the external naris; and �ubic �eduncle of ischium �arallel ��ith the ischial shaft.
Willinakaqe gen.nov.dis�lays the follo��ing characters su��orting its inclusion into the unnamed clade com�rising those taxa closer to Gryposaurus than to Brachyolophosaurus in the �hylogeny �ublished by Prieto-Márquez (2010, figure 5): Dorsoventral de�th of the central �late of the ilium lo��; and ratio bet��een the length of metatarsal III and its mediolateral breadth at midshaft lesser than 4.50.No unambiguous syna�omor�hies are �resent in all the resulting trees of this analysis su��orting the association bet��een the Gryphosaurus s�ecies and Willinakaqe salitralensis gen.et s�.nov.and their closer relatives, the unnamed Big Bend taxon of Prieto-Márquez (2010) and Secernosaurus koerneri.Four characters associate these latter three s�ecies: coracoid ��ith slightly longer sca�ular facet res�ect to the lateral margin of the glenoid; �resence of a brevis shelf at the base of the �ostacetabular �rocess of the ilium (see discussion in Prieto-Márquez's character 244); iliac medioventral ridge on the medial side of the �ostacetabular �rocess ��ell-develo�ed, oblique, and ex�anded into a flange forming the medial margin of an extensive brevis shelf that faces more ventrally than medially; and �resence of a craniocaudally oriented median ridge on the dorsolateral surface of the �ostacetabular �rocess of the ilium.Finally, Willinakaqe salitralensis gen.et s�.nov. is su��orted as the sister taxon of Secernosaurus koerneri by five character states in the Prieto-Márquez analysis: height of the neural s�ine greater than 2.10 times that of the centrum in the tallest caudal dorsal or sacral vertebrae; angle greater than 115° bet��een the lateral margin of the facet for sca�ular articulation and the glenoid in the coracoid; su�ra-acetabular �rocess of the ilium asymmetrical, ��ith a caudally ske��ed lateral �rofile; caudodorsal margin of ilium ��ith a ��ell-defined ridge continuous ��ith the dorsal margin of the �roximal region of the �ostacetabular �rocess; mid-shaft of the ischium ��ith a very thick shaft.
Some characters indicating a derived �lacement for Willinakaqe gen.nov.and Secernosaurus in relation to Telmatosaurus and more basal taxa includes: diamond-sha�ed dentary teeth ��ith only one straight medial keel and ��ith small denticles; dentary ��ith more than thirty alveoli and ��ith more than t��o teeth �osition; strong inflection of the dentary dorsal border forming a lo�� mandibular sym�hysis; coronoid �rocess of the dentary bone vertically oriented, lacking a rostral��ard inclination; sca�ular blade slightly distally ex�anded; sternal caudoventral �rocess ��ell develo�ed, relatively long, and thick relative to the sternal 'handle'; ilium ��ith dorsal border dis�laying an inflexion bet��een a convex cranial region and a concave caudal one u�on the acetabulum; large and extensive su�raacetabular �rocess located dorsal to the acetabulum; �rominent �ostacetabular �rocess of the ilium; ischial shaft straight and caudoventrally oriented; ischium ��ithout foot-like ex�ansion.Like��ise, Willinakaqe gen.nov.and Secernosaurus �resent several characters ��hich could be considered as �lesiomor�hic relative to Saurolo�hidae, such as a jugal ��ith a ventral margin of the rostral �rocess dorsal to level of lateral ridge of the ecto�terygoid shelf, a maxilla-jugal contact restricted to a finger-like jugal �rocess on the caudal margin of maxilla, less than thirty-five tooth �ositions in both dentary and maxillary dental batteries during ontogeny, no less than four foramina arranged in a sub-horizontal ro�� along the lateral ��all of the maxilla, and less than nine sacrals.
The ne�� taxon Willinakaqe salitralensis re�resents the second hadrosauroid s�ecies recognized from South America, because it dis�lays several differences ��ith Secernosaurus koerneri, ��hich contains the material �reviously assigned to "Kritosaurus" australis ( Prieto-Márquez & Salinas, 2010).These differences include the cervical vertebrae ��ith a lo��er angle of divergence bet��een the �ostzyga�o�hyses; dorsal vertebrae ��ith a shallo�� fossa �ositioned on the lateral surface of the neural arch, u�on the base of the transverse �rocess; tall neural s�ines in sacral and �roximal caudals more than four times the centrum height; �resence of a ventral keel in the �roximal sacral vertebrae; the �ostzyga�o�hysis of the �roximal caudal vertebrae situated at a level dorsal to the �rezyga�ho�hysis; distal region of the �ostacetabular �rocess of the ilium ventrally deflected; and femur ��ith o�en cranial intercondylar groove, among others.Other characters diagnostic of Willinakaqe salitralensis gen.et s�.nov., as those �resent in the �remaxilla, are not com�arable ��ith those of Secernosaurus koerneri because this element is unkno��n in the latter genus.
Based on the �hylogenetic scheme of the hadrosauroids �resented by Prieto-Márquez (2010), Willinakaqe salitralensis gen.et s�.nov.(their Salitral Moreno OTU) is found as the sister taxon to Secernosaurus koerneri ��ithin Saurolo�hinae.This analysis �resent decay index values of only one ste�, and bootstra� frequency values of less than fifty �ercent, for su��ort of all the successive clades including the South American taxa ��ith other saurolo�hines different of the "Big Bend Moreno" taxon.Furthermore, no less than nine reversal events are necessary along the hy�othesized evolutionary history of the clade com�rising Willinakaqe gen.nov., Secernosaurus and the Big Bend Moreno taxon to su��ort their derived �osition ��ithin Saurolo�hinae.A more detailed study of the South American forms and additional s�ecimens are necessary in order to confirm the �osition of both Secernosaurus and Willinakaqe gen.nov.
The �resence of hadrosauroid remains in the Late Cretaceous of Patagonia is of �articular interest for understanding the �aleobiogeogra�hic dis�ersal events occurring during this times�an, given that this grou� of dinosaurs is considered as being of Laurasian origin (Sues & Averianov, 2009).The original referral of the material from the Los Alamitos Formation to the genus Kritosaurus (Bona�arte et al., 1984) and the �ur�orted lambeosaurine condition of MPCA-Pv SM 2 advanced by Po��ell (1987) suggested than at least t��o different grou�s of hadrosauroids dis�ersed to South America during the Late Cretaceous.The �hylogenetic �lacement of the South American hadrosauroids �resented by Prieto-Márquez (2010) suggests only a dis�ersal event for the grou� follo��ed by a local radiation.Whether or not these biogeogra�hical events ocurred during the Cam�anian, and through the Isthmus of Panama or an alternative route, is still uncertain, �ending of a better understanding of the Late Cretaceous terrestrial vertebrate faunas from South America.
To date, all the diagnostic hadrosauroid material recovered from the Allen Formation of the Neuquén Basin belong to a single taxon, Willinakaqe salitralensis gen.et s�.nov., suggesting a slight tem�oral difference bet��een this stratigra�hic unit and those containing the taxon Secernosaurus australis.

Fig. 1 .
Fig. 1.Ma� indicating the northern Patagonian localities from ��hich the hadrosauroid fossils here studied have been recovered (indicated as stars).
The best �reserved cervical vertebrae are those of MPHN-Pv 01, ��hich have been �reviously described and illustrated by González Riga & Casadío (2000, Fig. 4A-C).Additional material came from the Salitral Moreno locality (MPCA-Pv SM 11, 13 and 14).The cervical vertebrae of Willinakaqe salitralensis gen.et s�.nov.dis�lays the same basic mor�hology �resent in Telmatosaurus and more derived hadrosauroids.As originally noted by González Riga & Casadío (2000), the cervical vertebrae of this taxon can be distinguished from those of Secernosaurus on the basis of the angle of divergence bet��een the �ostzyga�o�hyses, ��hich is greater in the latter taxon, and this re�resents one of the key characters allo��ing the association of the Salitral Moreno and the Islas Malvinas s�ecimens in a single taxon.Dorsal vertebrae.Isolated dorsal vertebrae com�rising different regions of the column are �resent (MPCA-Pv SM 15 to 22, MPHN-Pv 01, Fig. 5A-H; González Riga & Casadío, 2000, Fig. 4D), as evidenced by the different angles bet��een the transverse �rocesses and neural s�ines and the size and orientation of the neural s�ines, ��hich increases along the sequence and gets a more vertical orientation.Most of these vertebrae belong to juvenile individuals.As noted by González Riga & Casadío (2000) for the Islas Malvinas material, although their mor�hology is mostly usual for saurolo�hids, these vertebrae are different to