Gualicho shinyae Apesteguía, Smith, Valieri & Makovicky, 2016, gen. et sp. nov.

• Main Authors: Apesteguía, Sebastián, Smith, Nathan D., Valieri, Rubén Juárez, Makovicky, Peter J.
• Format: Text
• Language: unknown
• Published: Zenodo 2016
• Subjects: Biodiversity; Taxonomy; Animalia; Chordata; Saurischia; Gualicho; Gualicho shinyae; Argentina; Crest The; Fossa; Patagonia; The Arch; The Rib; Ula; Antarc*
• Online Access: https://dx.doi.org/10.5281/zenodo.6081285; https://zenodo.org/record/6081285

Gualicho shinyae gen. et sp. nov. (replaces Nototyrannus violantei Anonymous, 2011, nomen nudum) urn:lsid:zoobank.org:act:A 793 B 82 A- 972 E- 4159 - 9 D 88 - CCEB 9 CBDECB 5 Holotype. MPCN PV 0 0 0 1, comprising four articulated centra from the dorsal vertebral column, an articulated gastral basket, a section of the tail distal to the transition point, the left scapulocoracoid and forelimb, the distal end of both pubes including the pubic boot, and parts of both hind limbs (Fig 1 A). Much of the specimen had been lost to erosion when discovered, but the preserved parts including the forelimb, dorsal vertebrae, gastralia, and feet were articu- lated. Specimen measurements are provided in Table 1. Provenance. The specimen came from a sandstone layer in a section of alternating sand- and mudstones (see S 1 Fig) that make up the Cenomanian to Turonian aged Huincul Forma- tion [25] exposed along the northern flank of the Meseta de la Rentería, Río Negro Province, Argentina (Fig 1 B and 1 C). Exact locality data are on file with the authors. Permission was obtained by the senior author for this study from the Agencia Cultura de Río Negro, and com- plies with all relevant regulations. Differential diagnosis. Gualicho shinyae is distinguished by a unique combination of character states, which otherwise optimize as derived traits of very disparate theropod groups (see Description and Discussion). Posterior dorsal vertebrae very elongated and with slit-like pneumatic openings; scapular blade narrow with sinuous rostral margin marked by a shallow notch between the acromion process and blade; forelimb foreshortened with reduced muscle attachments and articulations and functionally didactyl; first and second metacarpals co-ossi- fied proximally, third metacarpal reduced to a splint; pubes with little or no pubic apron and blade-like boot; femur with mediodorsally inclined head; reduced femoral distal condyles; fib- ula with large fossa and accessory flange on proximocaudal corner; ridge-like m. iliofibularis tubercle of fibula; third metatarsal with expanded proximal articulation with posterior edge wider than rostral edge (antarctometatarsal condition [8]); pedal unguals with single claw sheath grooves that define small spur or tuber near proximal end. Etymology. Gualicho , a Spanish name derived from the Gennaken (günün-a-künna or northern Tehuelche language) watsiltsüm , for a goddess who was considered the owner of ani- mals and later, following the introduction of Christianity, reinterpreted as a demonic entity. ( Continued ) ( Continued ) ( Continued ) * element exhibits breakage, measurement represents preserved dimension † estimated measurement of broken element. doi:10.1371/journal.pone.0157793.t001 She is now considered a source of misfortune by rural settlers (gauchos) of the Southern Cone. The name was chosen to reflect the difficult circumstances surrounding the discovery and study of the specimen, and its contentious history following excavation. The specific name honors Ms. Akiko Shinya, Chief Fossil Preparator at the Field Museum, for her many contributions to paleontology including discovery of the holotype of Gualicho on February 13 th, 2007 (see S 1 Fig). Description and comparisons Axial column. Three dorsal centra are preserved in articulation, though the last one is missing the posterior half of its centrum (Fig 2). The absence of both parapophyses and ventral keels suggest they are from the caudal section of the dorsal series. The articular facets are flat, and the rims of the facets exhibit distinct longitudinal striations around the entire rims (Fig 2 C), which are often present in the posterior dorsals of theropods. The centra are spool-shaped with elliptical articular faces, and are slightly compressed dorsoventrally. The centra are very elongate, roughly 2.5 times as long as the articular facets are dorsoventrally high. Such proportions are unusual among theropods, but are approached in some coelophysoids [26], ceratosaurs like Masiakasaurus [27] and Elaphrosaurus (MB.R. unnumbered), and also in the megaraptoran Siats [28]. Poorly preserved pneumatic openings are present on all three centra (Fig 2 B). They are extremely elongate and slit-shaped, being dorsoventrally shallow, yet extending axially along the spool-portion of the centrum body. The left pneumatic opening of the first vertebra in the series is the best preserved, and indicates that the openings are confined to the centrum body, but rims are difficult to make out on the other elements. Unfortunately the poor preservation does not allow for an assessment of their depth, nor whether they deeply invade the centra. Dorsoventrally narrow pneumatic openings are observed on the dorsal vertebrae of some carcharodontosaurians such as Siats (FMNH PR 2716) and Aerosteon [29] (MCNA-PV- 3137), but are absent in non-abelisaurid ceratosaurs with elongate dorsal centra such as Spinostropheus [30] and Masiakasaurus [27], as well as in coelophysoids [31], and other outgroups. A few fragments of bone that are likely from the neural arch of the first vertebra in the series are still connected by matrix, but little detail regarding their morphology can be discerned. An isolated partial centrum of another posterior dorsal is preserved, but was crushed considerably dorsoventrally. This element exhibits a tight fit with the block of three centra and constitutes the fourth element in the series. It also bears an elongate, slit-like pneumatic foramen (Fig 2 B), though this is partially obscured by taphonomic distortion. Three caudal vertebrae from the middle of the tail are preserved (Fig 3). The articular facets are circular in end view and concave and the centra are spool-shaped and elongate, varying from about 1.5 to 2.0 times as long as the dorsoventral height of the articular facets. No sulci or ridges are observed on the ventral faces of the centrum bodies in the first two caudals. However, the last caudal, which is also the most axially elongated of the three, bears a faint midline ventral sulcus that is confined to the anterior half of the centrum body. The largest of the three caudals is also the most complete. It retains transverse processes in the form of axially elongated, elliptical projections on the sides of the neural arch, slightly posterior to its midpoint, indicating it is close to or at the transition point (Fig 3 A– 3 D). The prezygapophyses are stalked and project well beyond the anterior articular facet, further than the postzygapophyses, which only extend slightly past the posterior articular facet. The prezygapophyses are incomplete distally, and are angled anterodorsally rather than anteriorly. Stout ridges extend from the posterior base of the neural spine out to the tips of the postzygapophyses, which are canted with articular facets facing ventrolaterally. A strong ridge of bone also connects the lateral edge of the postzygapophysis to the middle of the lateral face of the neural arch. Only the posterior opening of the neural canal is visible and is rectangular and slightly wider than tall. A small depression is present dorsal to the neural canal, between the bases of the medial edges of the postzygapophyses. The base of a short neural spine is present, but is abraded and broken posteriorly. Another caudal (Fig 3 E– 3 H) exhibits even more reduced transverse processes, which are represented by low ridges on the sides of the neural arch. The neural spine is shallow, rectangular and axially elongate, unlike the tall, strap-like spines of many ceratosaurs including Ceratosaurus (UMNH VP 5278), Masiakasaurus [27] and Carnotaurus [32] (MACN-CH 894), but similar to the basal ceratosaur Elaphrosaurus (MB.R. unnumbered). The dorsal border of the spine has a weakly concave dorsal margin, giving it a saddle-shaped appearance in lateral aspect, though not to the degree that it appears bifid, as in e.g., Allosaurus [33]. The bifid condition is observed in many basal tetanuran lineages and is potentially a synapomorphy of a monophyletic Carnosauria [26]. Both pre- and postzygapophyses are broken in this specimen, but a low ridge spanning across the lateral face of the arch connects the base of the prezygapophysis to that of the postzygapophysis on each side. The third caudal (Fig 3 I– 3 K) is missing the posterior half of the centrum and postzygapophyses. The neural arch bears no trace of transverse processes suggesting this element represents a posterior caudal. The indented dorsal margin of the rectangular neural spine is below the level of the dorsal edges of the prezygapophyses. The prezygapophyses are relatively short and lobate in lateral aspect, and are significantly shorter than the length of the centrum. Gastral basket. A near-complete and articulated gastral basket comprising 16 or 17 gastral rows was collected with the holotype. As in carcharodontosaurids [2], megaraptorans [29], and some other theropod groups [34], multiple arches are fused at the midline. At least six arches exhibit midline fusion in MPCN PV 0 0 0 1, with fusion between elements observed in one anterior arch, and also in the five most posterior arches (Fig 4). These last five fused arches exhibit a progressively more acute angle between their rami posteriorly suggesting they are approaching the pubic boot. Notably, midline gastralia from the posterior portion of the gastral series found in contact with the pubic boot of Deltadromeus (SGM-Din 2) do not appear to be fused. The rostralmost gastralia are thicker in girth than more posterior ones and also meet at a much shallower angle on the midline, as is typical for theropods [34]. More posterior elements are hooked at the midline where they form an expanded but flattened surface for fusion with the opposite medial element. Unlike some tyrannosaurid specimens [34], pronounced medioventral or mediodorsal facets for articulation with adjacent gastral rows are not observed in the holotype of Gualicho . The medial gastralia taper toward their lateral ends and some exhibit shallow grooves for articulation with lateral gastralia. Fragments of lateral gastralia are preserved in articulation with two of the medial rows, but none are complete so it is unknown whether lateral elements were shorter than medial ones, or vice versa. None of the gastral elements, whether fused or not, exhibit pneumatic openings such as those described in Aerosteon [29]. Pectoral girdle. The majority of the left scapula and coracoid are preserved (Fig 5), though the distal tip of the scapula is broken off, rendering its total length uncertain. The blade is strap-like, with a preserved scapular length more than 10 times the width at the narrowest point of the blade, a proportion similar to that observed in carcharodontosaurids including Acrocanthosaurus [35], and Mapusaurus [2], but also Allosaurus [7] and Deltadromeus (SGM-Din 2). Following Rauhut [26], Carrano et al. [7] found this elevated ratio to be a synapomorphy of some carcharodontosaurids, and possibly also Allosauridae, as well as of Coelurosauria. In contrast to these taxa, however, the blade appears short and less than twice the length of the acromion-glenoid distance in Gualicho , resembling Deltadromeus (SGM-Din 2) and Masiakasaurus [27], though the dorsal-most portion of the blade is not preserved in Masiakasaurus [27]. Unlike most tetanurans [26], the blade does not exhibit a subequal width throughout most of its length, and rather appears to taper distally from its base as in Masiakasaurus [27], Limusaurus [36] and Deltadromeus (SGM-Din 2). The blade is weakly convex laterally throughout its length implying low curvature of the rib cage. The lateral surface is weakly rounded while the medial surface is almost completely flat, and the ventral edge is slightly thicker than the dorsal edge. Near the base of the blade, the dorsal edge expands dorsally, but then arcs weakly back ventrally adjacent to the base of the expanded acromion process (Fig 5 C). This sinuous margin creates a weak, rostrocaudally elongate flange along the dorsal edge that is separated from the base of the acromion process anteriorly by a broad and shallow indentation along the dorsal margin. A sinuous dorsal margin of the scapula adjacent to the acromion process defining a low flange is also observed in the African theropod Deltadromeus (SGM-Din 2), which also shares the presence of a relatively short, narrow, and distally tapering scapular blade with Gualicho . The scapula of Limusaurus [36] exhibits a deep, semicircular embayment of the rostral edge of the scapula at the transition between the acromion process and blade. Rostral to this indentation, the scapular margin expands smoothly dorsally to define the acromion process. The angle between the acromion process and the scapular blade is oblique, in contrast to the derived, perpendicular orientation seen in Allosauria and Coelurosauria [7]. Only the very base of the acromion process retains a natural edge, with the rest of the edges broken. However, the preserved edge is extremely thin, and likely did not continue much further, so that the outline of the preserved process is close to its original shape. The acromion process appears to have been shallow as in Deltadromeus (SGM-Din 2), Giganotosaurus (MUCPv-Ch 1), Mapusaurus [2], and Acrocanthosaurus [35], but not Megaraptor (MUCPv 341), Allosaurus [33], and Sinraptor [37]. The base of the coracoid process of the scapula is preserved with the scapular blade, but the glenoid portion is broken off and preserved with the coracoid. The scapula and coracoid are fused but not completely co-ossified, and a line of fusion can still be discerned on both sides, though it is more visible on the medial side (Fig 5 B and 5 C). The scapula contributes about two thirds of the glenoid articulation, whereas the coracoid contributes the remaining third (Fig 5 A). The articular surface of the glenoid is angled outward slightly, such that it faces ventrolaterally. A small lip is formed by the scapula and coracoid at the dorsal and ventral margins of the glenoid, respectively. These lips are not laterally everted, and instead project caudally (Fig 5 B). Similar lips are present in many ceratosaur taxa including Elaphrosaurus (MB. R. unnumbered), Masiakasaurus [27], and Carnotaurus (MACN Ch 895), but also are observed in the megaraptoran Aerosteon [29] (MCNA-PV- 3137). Unlike Elaphrosaurus (MB. R. unnumbered), the glenoid lips do not merge to form a rim around the entire glenoid, but rather are restricted to the ventral and dorsal limits of the articulation. A large, oval coracoid foramen is present about eight centimeters anterior to the glenoid (Fig 5 A– 5 C). The majority of the coracoid is weakly convex laterally, with the exception of a small area just dorsal to the coracoid foramen and anterior to the suture between the scapula and coracoid that is shallowly depressed. A coracoid (= 'biceps') tubercle is absent, as is the case in Masiakasaurus [25], Deltadromeus (SGM Din 2), and many Megalosaurians [7], but in contrast to the condition in most tetanurans, which possess an oblique ridge-like tubercle [7]. The posteroventral process of the coracoid is hooked and extends far ventral to the glenoid, to a degree similar to that seen in Deltadromeus (SGM-Din 2), and Megaraptor (MUCPv 341). A well-developed posterovental process is only present in Masiakasaurus [27] and Elaphrosaurus (MB.R. unnumbered) within Ceratosauria, and in these two taxa, the process is not as extensive as in Gualicho . Within Tetanurae, a pronounced posteroventral process is absent in basal members such as ' Dilophosaurus ' sinensis , Torvosaurus , Megalosaurus , and Yangchuanosaurus hepingensis , but is a synapomorphy of Allosauria [7]. Its posterior edge below the glenoid is also everted slightly laterally, much like the glenoid articulation. This everted edge is widest just below the glenoid, and it thins ventrally along the posteroventral process. This area of the posteroventral process also lacks the distinct fossa (Fig 5 A) that is present in megaraptoran taxa [38]. Forelimb. Parts of both forelimbs were collected with MPCN PV 0 0 0 1, including a complete left forelimb. The right forelimb is represented by the radius and ulna. The humerus is almost straight with only a slight laterally convex bow (Fig 5 A and 5 B). The distal condyles are twisted laterally about 15 degrees relative to the humeral head (Fig 6 C and 6 D), which is mediolaterally elongate, unlike the spherical humeral head of many ceratosaurs [26] including Deltadromeus (SGM-Din 2) and Elaphrosaurus (MB. R. unnumbered). There is a very weak cleft between the head and the pointed internal tuberosity (Fig 6 B). The internal tuberosity is distinctly thinner than the head in proximal view. There is no evidence of a deep, longitudinal furrow on the caudomedial side of the proximal humerus, as is present in Australovenator [39], Fukuiraptor [40], Chilantaisaurus [41], and Megaraptor [11]. Although this feature has also been suggested to be present in tyrannosaurids [12], this is based on misinterpretation of a pathology in one specimen of Tyrannosaurus rex [42, 43] (FMNH PR 2081). Two broad depressions are present on the anterior face of the humerus, though these are slightly accentuated by crushing of the element. The proximal depression is just below the humeral head and is mediolaterally elongate, extending across the breadth of the bone. The distal depression is more elongate and situated in the middle of the bone just medial to the deltopectoral crest. The deltopectoral crest is set perpendicular to the long axis of the humeral head (Fig 6 A and 6 B), as in a majority of theropods with the exception of some megalosaurians that have an anterolaterally directed deltopectoral crest [7]. It is proximodistally elongate and spans approximately one quarter the length of the humerus. Among theropods, a deltopectoral crest with such a limited proximodistal extent is only seen in Deltadromeus (SGM Din- 2) and Ornithomimosauria [26], although Masiakasaurus [27] and Elaphrosaurus (MB.R. unnumbered) approach this condition. It tapers to a thin (and abraded) edge proximally, but its apex is thickened mediolaterally into a lobate tuberosity that is a proximodistally elongate ellipse in anterior aspect. A distinctly offset and lobate apex on the deltopectoral crest is widespread among allosauroid species including Acrocanthosaurus [35], Neovenator [44], and Fukuiraptor [40], but is not observed in megalosauroids [45], ceratosaurs (e.g., Ceratosaurus UMNH VP 5278), coelophysoids ( Dilophosaurus UCMP 37302), and coelurosaurs (e.g., Compsognathus MB.R. 2003.2; Guanlong IVPP V 14531). There is a small, circular divot on the posterior surface of the humerus (Fig 6 B), just below the midpoint of the head that is located in a topologically identical position to a large fossa on th : Published as part of Sebastián Apesteguía, Nathan D. Smith, Rubén Juárez Valieri & Peter J. Makovicky, 2016, An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina, pp. 1-41 in PLoS ONE 11 (7) on pages 5-30, DOI: 10.1371/journal.pone.0157793, http://zenodo.org/record/269955