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The position of the claws in (Dinosauria: ) and its implications for abelisauroid manus...

Article in Paläontologische Zeitschrift · June 2009 DOI: 10.1007/s12542-009-0044-2

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RESEARCH PAPER

The position of the claws in Noasauridae (Dinosauria: Abelisauroidea) and its implications for abelisauroid manus evolution

Federico L. Agnolin • Pablo Chiarelli

Received: 14 April 2009 / Accepted: 24 October 2009 Ó Springer-Verlag 2009

Abstract In this note we reassess the position of putative occurs plesiomorphically in most basal theropods (e.g., pedal phalanges of some South American noasaurid thero- ). pods (Abelisauroidea). Noasaurids were considered as to be distinctive abelisauroids with a peculiar ‘‘sickle claw’’ on Keywords Abelisauroidea Á Noasauridae Á Phalanges Á the second toe of the foot, convergently developed with that Á Argentina of deinonychosaurians. Among noasaurids, the Argentinean species Noasaurus leali (latest Cretaceous) and Kurzfassung In der vorliegenden Studie wird eine Ne- andesi () are known from incomplete ubewertung der mutmaßlichen Position der Zehenglieder specimens, including dissarticulated non-ungueal pha- su¨damerikanischer noasaurider Theropoden (Abelisauroidea) langes, and, in N. leali, a claw. A detailed overview of these pra¨sentiert. Noasauride werden als unverwechselbare Abelis- elements indicates that the supposed raptorial claw of the auroide mit einer besonderen ‘‘Sichelkralle’’ am zweiten Zeh second pedal digit of N. leali actually belongs to the first or des Fußes, die konvergent zu der der Deinonychosaurier ent- second finger of the manus, and the putative pedal non- stand ist, betrachtet. Die beiden argentinischen Arten Noa- ungual phalanges of both genera also pertain to the manus. saurus leali (oberste Kreide) und Ligabueino andesi Thus, the new interpretations of noasaurid pedal morphol- (Unterkreide), die beide zu den Noasauriden geho¨ren, sind nur ogy blur the distinctions between Noasauridae and Veloci- durch unvollsta¨ndigen Exemplaren einschließlich nicht-ung- sauridae proposed by previous authors. Finally, we suggest, ualer Zehenglieder und einer Kralle von N. leali belegt. Eine on the basis of phalangeal and metacarpal morphology, that ausfu¨hrliche Untersuchung dieser Elemente deutet darauf hin, abelisaurids probably lost their manual claws by means of dass die angeblich ra¨uberische Kralle der zweiten Zehe von the loss of function of the HOXA11 and HOXD11 genes. N. leali tatsa¨chlich zum ersten oder zweiten Finger der Hand Thus Noasauridae differs from in retaining geho¨rt. Ebenso geho¨ren auch die nicht-ungualen Zehenglieder plesiomorphic long forelimbs with well developed claws, as beider Taxa zur Hand. Die unterschiedliche Fußmorphologie, wie sie von verschiedenen Autoren vorgeschlagen wurde, beeintra¨chtigt die Unterscheidung zwischen Noasauriden und Velocisauriden. Wir vermuten auf Grund der Phalangen- und F. L. Agnolin (&) Laboratorio de Anatomı´a Comparada y Evolucio´n de los Metacarpaliamorphologie, dass der Verlust der Funktion der Vertebrados, Museo Argentino de Ciencias Naturales HOXA11- und HOXD11-Gene mo¨glicherweise fu¨rdasFeh- ‘‘Bernardino Rivadavia’’, Avenida A´ ngel Gallardo 470 len von Fingerkrallen bei den Abelisauriden verantwortlich (C1405DJR), Buenos Aires, Argentina ist. Somit unterscheiden sich die Noasauriden von den e-mail: [email protected] Abelisauriden durch den Besitz der plesiomorphen langen F. L. Agnolin Á P. Chiarelli Vorderextremita¨ten mit gut-entwickelten Krallen, wie es auch Fundacio´n de Historia Natural ‘‘Fe´lix de Azara’’, bei basalen Theropoden (z.B. Coelophysis) der Fall ist. Departamento de Ciencias Naturales y Antropologı´a, CEBBAD, Universidad Maimo´nides, Valentı´n Virasoro 732 (1405), Buenos Aires, Argentina Schlu¨sselwo¨rter Abelisauroidea Á Noasauridae Á e-mail: [email protected] Phalangen Á Kreide Á Argentinien 123 F. L. Agnolin, P. Chiarelli

Abbreviations Province, northwestern Argentina; , FMNH PR Field Museum of Natural History, Chicago, , latest Cretaceous; Bonaparte and Powell USA 1980)andLigabueino andesi (La Amarga locality, Neuque´n MACN-PV-N Coleccio´n de Paleontologı´a de Vertebrados, Province, northern Patagonia, Argentina; La Amarga Provincia de Neuque´n,MuseoArgentinode Formation, -early , Early Cretaceous; Ciencias Naturales ‘‘Bernardino Rivadavia’’, Bonaparte 1996), and we add some new interpretations on Buenos Aires, Argentina noasaurid and abelisaurid manus morphology. PVL Coleccio´n de Paleontologı´a de Vertebrados, In this paper we follow the phylogenetic of Instituto Miguel Lillo, Tucuma´n, Argentina Wilson et al. (2003) with the modifications introduced by Carrano and Sampson (2008). We also use the anatomical terminology employed by Carrano (2007).

Introduction Reappraisal of the noasaurid manual and pedal Abelisauroidea is a group of very specialized and bizarre anatomy carnivorous that dominated Gondwanan preda- tory niches along the (Bonaparte 1986, In the following section we discuss the morphology of the 1991a; Sereno et al. 2004). These dinosaurs inhabited ter- supposed pedal phalanges of both Noasaurus leali, and restrial ecosystems together with a large array of endemic Ligabueino andesi. Because the phalanges of these genera and allochtonous theropods, for example, basal tetanurans have been described by previous authors this brief over- (e.g., , ; Apesteguı´a view emphasizes traits that allow us to recognize the 2002; Novas et al. 2005a), and coelurosaurs (e.g., Alv- manual or pedal nature of noasaurid phalanges. arezsauridae; Bonaparte 1991a, b; Novas 1997). At least in Early and early Late Cretaceous times (Aptian through Ungual phalanges Cenomanian), together with the Carcharodontosauridae, abelisaurids constituted the dominant predatory dinosaurs Recent works have stressed the apomorphic morphology of southern continents (Bonaparte 1986). present in the abelisaurid pedal claws. As observed by To date, Abelisauroidea comprises two morphologically Novas and Bandyopadhyay (2001), these phalanges bear a divergent theropod subclades: the mid-sized Abelisauridae well defined ‘‘Y’’-shaped system of lateral grooves, a lat- and the small to mid-sized Noasauridae (Bonaparte 1991a), eral tuberosity, and a deep ventral concavity, presumably a phylogenetic arrangement recently confirmed by multiple for flexor tendon attachment (see also Novas et al. 2005b; cladistic analyses (Wilson et al. 2003; Sereno et al. 2004; Maganuco et al. 2008) that probably replaced in function Carrano and Sampson 2008; Canale et al. 2009). However, a the flexor tubercle exhibited by other theropods (Bonaparte few authors (Bonaparte 1991b; Agnolin et al. 2003) pro- and Powell 1980). posed the existence of a third abelisauroid subclade: Ve- On the other hand, noasaurid pedal unguals are very locisauridae Bonaparte 1991b on the basis of the poorly poorly known, being represented only by disarticulated known genus . As originally understood, one of specimens. The first described purported noasaurid pedal the most striking features of Noasauridae was thought to be ungual phalanx belonged to Noasaurus leali (Bonaparte the presence of a raptorial ‘‘sickle claw’’ assigned to the and Powell 1980). It has an unusual shape for a theropod second pedal digit, morphologically convergent with that of claw, and was regarded as homoplastic with that of the deinonychosaurs (Bonaparte and Powell 1980; Bonaparte dromaeosaurid and troodontid ‘‘sickle claw’’ pedal digit II 1996; see Gauthier 1986). In the original description of (Bonaparte and Powell 1980). Curiously, the Noasaurus Noasaurus leali, Bonaparte and Powell (1980) described a ungual strongly differs from all known abelisauroid pedal single non-ungual phalanx as belonging to the second pedal claws (both abelisaurid and noasaurid; e.g. those of digit. Subsequently, Bonaparte (1996) described Ligabueino , , , and Masiakasau- andesi, and reported the presence of pedal pre-ungual pha- rus; Coria and Salgado 2000; Coria et al. 2002; Carrano langes of uncertain anatomical position. Lately, several et al. 2002; Carrano 2007) in lacking the ‘‘Y’’-shaped isolated ungual and other isolated non-ungual phalanges system of lateral grooves and bump, the large and pro- attributed to noasaurids were described from the latest truding proximodorsal lip, and also in the extreme curva- Cretaceous of and (Carrano et al. 2002; ture of the claw blade (Fig. 1; Novas and Bandyopadhyay Novas et al. 2004). 2001; Sampson et al. 2001; Novas et al. 2004, 2005b). In this note we review the morphology of the known These differences were considered in preliminary analyses phalanges of Noasaurus leali (El Brete locality, Salta (Agnolin et al. 2004; Carrano et al. 2004; Carrano and 123 Manual phalanges in Noasauridae

3 ungual oval cross-section (subtriangular cross-section in theropod pedal unguals); and 4 strong curvature ungual, describing an arch of nearly 90° along its ventral margin (nearly ventrally flat in most theropod pedal claws) (Ostrom 1969; Madsen 1976; Gauthier 1986; Currie and Zhao 1993; Russell and Dong 1993; Novas and Bandyopadhyay 2001; Novas et al. 2004). Although traits 2 and 4 may occasionally be present in the pedal phalanges of some theropod groups (i.e., the raptorial ‘‘sickle claw’’ of pedal digit II of Dromaeosauri- dae and Troodontidae; Rauhut and Werner 1995), all four features are found in the vast majority of (if not all) the- Fig. 1 Manual elements of Noasaurus leali (holotype PVL 4061). a ropod manual claws. Thus, this combination of features manual ungual of digit II or III, in lateral view; b–d Digit ?III phalanx suggests that the putative pedal ungual of Noasaurus is in: b lateral; c dorsal; and d ventral views. CLP, collateral ligamental actually a manual ungual, as previously indicated by pre- pit; HP, hyperextensor pit; LG, lateral groove; MK, median keel; liminary studies (Agnolin et al. 2004; Carrano et al. 2004; MVR, median ventral ridge; N, phalangeal neck; PDP, proximodorsal process; PVP, proximoventral process. Scale bar 1cm Carrano and Sampson 2008). Moreover, in addition to the traits mentioned above the Noasaurus claw clearly differs from pedal elements previously reported for noasaurids in Sampson 2008) to be suggestive of the possibility that the lacking a medial deflection of the shaft and in having an Noasaurus claw actually belongs to the manus rather than acute and small proximodorsal lip and a sharp ventral edge the pes. Furthermore, the Noasaurus claw shows several (Fig. 2; Carrano et al. 2002; Novas et al. 2004). Based on traits that are atypical for a theropod pedal claw, but con- its strong curvature and general morphology the Noasaurus sistent with manual unguals (Fig. 2), as follows: manual claw may belong to the first or second digit, 1 proximal articular surface dorsoventrally tall and being rather similar to that of other carnivorous dinosaurs mediolaterally flattened, being deeply concave when (e.g., ; Madsen 1976). viewed medially or laterally (dorsoventrally extended The only previous mention of a noasaurid manual claw and slightly concave in most theropod pedal unguals, are two isolated specimens attributed to including those of dromaeosaurids and troodontids); knopfleri (Carrano et al. 2002). These materials differ from 2 proximal articular surface with a sharp median keel that of Noasaurus leali in possessing a true flexor tubercle (low-keeled or smooth proximal surface in theropod and in lacking a ventral sulcus. However, this phalanx was pedal claws, especially in those of Abelisauridae); not found in articulation with any definite bone of

Fig. 2 Left lateral view of manual and pedal claws of selected (a modified from Bonaparte and Powell 1980; b, e modified from theropod dinosaurs. a–d manual claws; e–h pedal claws. a probable II Madsen 1976; c, g modified from Ostrom 1969; d modified from or III of Noasaurus leali; b claw II of Allosaurus fraglis; c claw II of Charig and Milner 1997; f modified from Currie and Zhao 1993; Deinonychus antirrhopus; d claw II of walkeri; e claw III h modified from Maganuco et al. 2008). Not to scale. LG, lateral of Allosaurus fragilis; f claw III of dongi; g claw III of groove; MK, median keel; FT, flexor tubercle; LB, lateral bump Deinonychus antirrhopus; h claw III of unidentified abelisaurid. 123 F. L. Agnolin, P. Chiarelli

Masiakasaurus; accordingly, the assignment of this claw to unknown; thus, the raptorial condition of noasaurid pedal that taxon is currently equivocal. unguals is currently equivocal. Accordingly, the distinction Consequently, the only unquestionable clear evidence of between noasaurids and velocisaurids presently lacks sup- a noasaurid manual ungual pertains to the holotype of port, and we propose to considering Velocisauridae Noasaurus leali (PVL 4061). Thus, Autapomorphic traits Bonaparte, 1991 as a junior synonym of Noasauridae present on the manual phalanx of Noasaurus, and absent in Bonaparte and Powell 1980. remaining theropods include: 1 the presence of a median ventral ridge distal to the Non-ungual phalanges proximo ventral concavity, and 2 a very deep and subtriangular ventral concavity, which Non-ungual phalanges of the pes are well known in the was probably the insertion area of powerful flexor noasaurids Masiakasaurus and Velocisaurus, and in musculature (Bonaparte and Powell 1980; Novas and noasaurid-like abelisauroids from India (Bonaparte 1991b; Bandyopadhyay 2001). Carrano et al. 2002; Novas et al. 2004). In contrast, in Noasaurus (Bonaparte and Powell 1980) and Ligabueino The only other ceratosaurian in which manual unguals (Bonaparte 1996), only isolated phalanges of the pes have have been preserved is in the problematic been described. However, as was indicated briefly in a (Xu et al. 2009). In Limusaurus the unguals are short, stout, previous report, these elements actually may belong to the and small, being mediolaterally expanded on their proxi- manus (Agnolin et al. 2004). mal ends (Xu et al. 2009), being rather different from that In Noasaurus leali, the only known non-ungual phalanx of Noasaurus, and lacking the proposed autapomorphies of is a very short and stout element (Fig. 1b–d). It has a the latter. However, because manual ungual phalanges are rectangular-shaped proximal articular surface which bears unknown in other abelisauroids and , both a sharp and well defined median keel. This bone also has a proposed autapomorphies may eventually be shown to well defined, strikingly narrow, and short proximoventral diagnose more inclusive clades within (sensu process, as also occurs in known abelisaurid manual pha- Rauhut 2003). In addition, as proposed by Novas and langes (e.g., those of and Aucasaurus; Bandyopadhyay (2001), a deep fossa and a reduced flexor Bonaparte et al. 1990; Coria et al. 2002), whereas in the tubercle of the pedal unguals are probably abelisauroid manual phalanges of other theropods this process is absent synapomorphies. As the same morphology is present in or extremely wide, its mediolateral width being subequal to noasaurids, both traits can now be considered as abelisau- that of the distal articular surface. The proximodorsal roid synapomorphies. process is nearly quadrangular in contour, a trait regarded Furthermore, our reconsideration of the manual unguals by previous authors as a noasaurid synapomorphy, because of Noasaurus sheds some light on the validity of the clade it is present in both Ligabueino and Noasaurus (Coria and Velocisauridae Bonaparte, 1991. This theropod group was Salgado 1998). In Noasaurus the constriction between the erected by Bonaparte (1991b) to include the single species proximal and distal articular surfaces is strong; the distal Velocisaurus unicus Bonaparte, 1991 from the Santonian articular condyle is nearly rounded in lateral view and (Upper Cretaceous) Bajo de la Carpa Formation of Neuque´n exhibits a large, ellipsoidal, collateral ligamental pit on the Province, Argentina. More recently, the Malagasy noa- dorsal half of each condyle. The distal articular surface saurid theropod Masiakasaurus knopfleri Sampson et al. shows a deep median sulcus. (2001), from the Campanian–Maastrichtian Maevarano The characters that suggest that the only known non- Formation, was also included within Velocisauridae ungual phalanx of Noasaurus is a manual element are as (Agnolin et al. 2003). Agnolin et al. (2003) supported this follows: hypothesis on the presence of common characters, allowing these authors to recognize the close phylogenetic rela- 1 the collateral ligamental pit is located on the dorsal half tionship of Noasauridae and Velocisauridae. This view was on the lateral side of each distal articular condyle in subsequently corroborated by Carrano and Sampson (2008) lateral view; in a comprehensive cladistic analysis of abelisauroid 2 the distal articular condyles are displaced ventrally interrelationships. Agnolin et al. (2003) distinguished relative to the main axis of the shaft in medial and velocisaurids from noasaurids only on the basis of the lateral views; presence of non-raptorial pedal unguals in the former 3 the lateral and medial margins of the distal articular group, in contrast with the ‘‘sickle claw’’ supposedly condyles are oriented subparallel to each other when exhibited by Noasaurus. However, following the current viewed dorsally (anterodorsally convergent in most interpretation, Noasaurus pedal unguals are currently theropod pedal phalanges); and

123 Manual phalanges in Noasauridae

Fig. 3 Left lateral view of preungueal phalanges of selected thero- pods. a–c manual elements; d–f pedal elements. a digit ?III phalanx of Noasaurus leali; b digit ?III phalanx of Ligabueino andesi; c phalanx 1 digit III of Allosaurus fragilis. d phalanx 2 digit II of Deinonychus antirrhopus; e phalanx 3 digit IV of Allosaurus fragilis; f phalanx 3 digit IV of Velocisaurus unicus.(a modified from Fig. 4 Ligabueino andesi (holotype MACN PV-N 42). Digit ?III Bonaparte and Powell 1980; b modified from Bonaparte 1996; phalanx in: a lateral view; b dorsal view; c lateroventral view; c, e modified from Madsen 1976; d modified from Ostrom 1969; d proximal view. CLP, collateral ligamental pit; HP, hyperextensor f modified from Bonaparte 1991b). Not to scale pit; MK, median keel; PDP, proximodorsal process; PVP, proximo- ventral process. Scale bar 2mm 4 the proximal surface has an acute median keel that separates deep articular cotyles (Fig. 3; Ostrom 1969; manual phalanges are not especially productive because the Madsen 1976; Currie and Zhao 1993;Xuetal. 2002). latter clade exhibits a high degree of modification of the hand (Bonaparte et al. 1990; Coria et al. 2002; Burch and Although traits 1 and 2 are occasionally present in pedal Carrano 2008). Nevertheless, the manual phalanges of both phalanx II-2 of the deinonychosaurian coelurosaurs Noasauridae (e.g., Ligabueino, Noasaurus; Bonaparte and (Xu et al. 2002), the combination of features mentioned Powell 1980; Bonaparte 1996; this paper) and Abelisauri- above only occurs, as a whole, in theropod manual ele- dae (e.g., Aucasaurus, Carnotaurus; Bonaparte et al. 1990; ments. Moreover, the non-ungual phalanx of Noasaurus Coria et al. 2002) possess a short and wide proximoventral further differs in several aspects from the pedal phalanx process that is unknown in other theropods; consequently, II-2 of troodontids and dromaeosaurids; the former element this character is a probable synapomorphy of has less dorsally deflected distal condyles, a poorly medi- Abelisauroidea. olaterally compressed distal end, and a less constricted The robust non-ungual phalanges, large, recurved rap- phalangeal neck. (Rauhut and Werner 1995). torial manual claws, and elongated humerus are features In the original description of Noasaurus, Bonaparte and indicative of the presence of elongated forelimbs in Powell (1980) considered that the ungual and non-ungual Noasauridae (Sereno et al. 1996; Carrano et al. 2002), phalanges of the holotype were probably II-2 and I-3I, clearly contrasting with the reduced arm and manus present respectively. However, in this contribution, we suggest that in other ceratosaurians (e.g., Ceratosaurus, Carnotaurus, these phalanges are not sequential because they do not Aucasaurus, Majungasaurus; Gilmore 1920; Bonaparte articulate properly; in conclusion, they may belong to et al. 1990; Madsen and Welles 2000; Coria et al. 2002; different digits (Fig. 1). Burch and Carrano 2008). Elongated forelimbs are also Our review of the holotype of Ligabueino andesi present in basal saurischians and basal theropods (e.g., (MACN-PV-N 42; Bonaparte 1996) revealed the presence , ; Rowe and Gauthier of manual phalanx features in a putative pedal phalanx, for 1990; Sereno 1993) and some ceratosaurians (e.g. Elaph- example, distal articular surface and collateral ligamental rosaurus, Limusaurus; Janensch 1920; Xu et al. 2009), pits dorsally displaced and proximal heel narrow and short suggesting that the condition exhibited by Noasauridae (Fig. 4). As a result, we conclude that both the known non- may be plesiomorphic within Ceratosauria. ungual phalanges of both Noasaurus leali and Ligabueino andesi belong to the manus rather than the pes. The precise position of the manual non-ungueal pha- langes of Ligabueino and Noasaurus within the hand Brief overview of abelisaurid manual morphology remains unknown, because the manus is not preserved and in other noasaurid taxa is unknown. However, the short Regrettably, in most ceratosaurians the manus in unknown and transversely broad condition of the available elements or nearly so. The only genera of non-abelisauroid cerato- suggests that they may belong to the third digit. Regrettably, saurians in which the manus is known are Ceratosaurus comparisons between noasaurid and abelisaurid non-ungual and Limusaurus (Gilmore 1920; Xu et al. 2009). Although 123 F. L. Agnolin, P. Chiarelli in both genera the manus is reduced, distalmost non-un- unguals. Large theropod manual ungual phalanges are also gueal phalanges still retain pulley-like well excavated absent in the richly fossiliferous Late Cretaceous forma- distal articular surfaces, and in the case of Limusaurus tions of India and Madagascar, from which hundreds of manual unguals of digits II and III have been preserved abelisaurid bones have been recovered, including abundant (Xu et al. 2009). In contrast with the well developed pedal unguals (Novas et al. 2004; Maganuco et al. 2008). manual non-ungual phalanges exhibited by other thero- In summary, we suggest that abelisaurid forelimb reduction pods, including noasaurids, the phalanges of abelisaurids not only included phalangeal shortening and simplification, are shortened and reduced (Novas 1991, 1992). In abeli- but also the loss of manual unguals. The reduction or loss of saurids, manual phalanges are only known in Carnotaurus, manual elements is not an uncommon phenomenon and has Aucasaurus, and Majungasaurus (Bonaparte et al. 1990; been reported in several tetrapod groups, including squamates Coria et al. 2002; Burch and Carrano 2008), and all of these (Greer 1991; Palci and Caldwell 2007) and titanosaurian bear several features that are worthy of mention. Several sauropod dinosaurs (Salgado et al. 1997). manual features are apomorphic for abelisaurids, including the discoidal morphology of proximal phalanges and car- pals, the absence of hyperextensor pits on the dorsal sur- Conclusions face of phalanges and metacarpals, the shallowness of collateral ligament pits, and the poorly excavated distal In this paper we arrive at the following conclusions: articular surface. These traits indicate, as a whole, the 1. The putative ‘‘sickle claw’’ of the second toe of the pes reduction of flexor and extensor movements in the abeli- of Noasaurus, is actually a first or second manual saurid manus (Rauhut 2003). Moreover, the shortened ungual. nature of the distal non-ungual phalanges indicates the lack 2. In Ligabueino and Noasaurus, the supposed pedal non- of grasping abilities (Sereno 1993) and, perhaps, the total ungual phalanges probably pertain to the manus lack of mobility, as is probably the case for the several (probably digit III), an hypothesis based on several fused phalanges within the manus of Majungasaurus features exhibited by their proximal and distal articular (Burch and Carrano 2008). A similar morphology may be surfaces. observed in the manus of titanosauriform sauropods, in 3. The presence of an acute and short proximoventral which phalangeal reduction has been correlated with pae- process may be a diagnostic trait of non-ungual manual domorphic phenomena (Salgado 2003). In the same way, phalanges of Abelisauroidea. the extreme forelimb reduction seen in abelisaurids was 4. The reinterpretation of noasaurid unguals allows us to interpreted as the consequence of the loss of function of the propose that the clade Velocisauridae Bonaparte, 1991 HOXA11 and HOXD11 genes (Vargas 2002). The pres- be considered a junior synonym of Noasauridae ence of flat, broad, and rugose distal articular surfaces on Bonaparte and Powell 1980. the distalmost non-ungual phalanges of Aucasaurus and 5. We propose, on the basis of skeletal morphology and Carnotaurus, together with the reduction of flexor and negative evidence, that members of Abelisauridae extensor pits and overall size, are features that suggest not probably lacked their manual ungual phalanges. only the absence of flexor and extensor movements in the Additionally, abelisaurids probably lost manual flexor abelisaurid manus, but also the total absence of unguals. In and extensor movements thus these theropods lacked Aucasaurus, as was noted by Coria et al. (2002), and in grasping abilities. Majungasaurus, as indicated by Burch and Carrano (2008), metacarpals I and IV are conical structures that appear to have carried no phalanges. The same appears to be true for Acknowledgments We wish to thank Jose´ Bonaparte (Fundacio´nde ´ Carnotaurus, in which the metacarpal IV is a splint-like Historia Natural Felix de Azara) for allowing us to study the holotypes of Ligabueino andesi and Noasaurus leali, Gabriel structure and metacarpal I is extremely reduced (Bonaparte Lio (FHNFA) for some drawings of the holotypical material of et al. 1990). Aucasaurus, the only abelisaurid in which non- Noasaurus, and Martı´n Ezcurra (MACN) for photographs of ungual phalangeal formula may be clearly established, has Ligabueino andesi. only one phalanx in digit II and two phalanges in digit III, indicating that these digits bear no unguals. The same morphology may be also observed in Majungasaurus, References which has a perfectly preserved manus without any sign of claws (Burch and Carrano 2008). Moreover, in other Agnolin, F.L., F.E. Novas, and S. Apesteguı´a. 2003. Velocisaurids in abelisaurids, including the beautifully preserved skeletons and Madagascar. Ameghiniana 40: 77R. Agnolin, F.L., S. Apesteguı´a, and P. Chiarelli. 2004. The end of a of Aucasaurus and Carnotaurus, in which most elements of myth: The mysterious ungual claw of Noasaurus leali. Journal the manus are known, there is no evidence of manual of Vertebrate Paleontology 24: 33A. 123 Manual phalanges in Noasauridae

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