Neuquenraptor argentinus Novas and Pol, 2005
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publication ID |
https://doi.org/ 10.4202/app.00348.2017 |
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persistent identifier |
https://treatment.plazi.org/id/5D3E87E0-9571-FFF4-2F34-F8F4FEDB0ABE |
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treatment provided by |
Felipe |
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scientific name |
Neuquenraptor argentinus Novas and Pol, 2005 |
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Neuquenraptor argentinus Novas and Pol, 2005
Holotype: MCF PVPH 77 View Materials , fragments of dorsal ribs, two proximal haemal arches, left proximal radius, incomplete right femur, distal end of right tibia, proximal tarsals, and most of the left foot.
Type locality: Sierra del Portezuelo ( Fig. 1), Neuquén Province, Argentina.
Type horizon: Portezuelo Formation, Coniacian, Late Cretaceous.
Emended diagnosis.—Mid-sized unenlagiid theropod ( Table 1) with the following combination of characters (autapomorphies marked with an asterisk): deep and wide extensor sulcus on proximal half of metatarsus; metatarsal III proximally pinched; metatarsal II with lateral expansion over the caudal surface of metatarsal III *; distal third of the medial surface of the metatarsal II is obliquely oriented and is delimited from the caudal surface of the metatarsal shaft by the subtle distal end of the plantar crest* distal third of metatarsal IV transversely wide*; pedal digit II with phalanges 1 and 2 sub-equal in length* and well-developed medial bump on pedal phalanx IV- 3*.
Description.— Haemal arches: Two proximal haemal arches have been preserved ( Fig. 2 View Fig ). Based on comparisons with Velociraptor and Linheraptor they likely represent two of the three cranialmost haemal arches, because they lack a distal expansion ( Norell and Makovicky 1997). The chevrons are distally curved, a feature more accentuated in the caudalmost preserved element. The cranial margin is convex in lateral view and the caudal one is concave, being deeper in the caudalmost haemal arch. The distal end of the blade is broken off in the cranial-most haemal arch, but appears to have been distally tapering. The distal end of the caudal element tapers to an acute margin. A cranial expansion is only present in the cranialmost haemal arch. It is formed by a well-developed hook-like process located at the dorsal half of the cranial surface of the bone. The caudal expansion seems to be absent.
Radius: A partial left radius was preserved ( Fig. 3 View Fig ) lacking most of its distal half. It is long, gracile, and nearly straight. The proximal end shows a subtriangular-shaped articular surface. It is cup-shaped for articulation with the humeral ectepicondyle. The caudolateral and craniomedial margins of the proximal end of the radius are slightly upturned. The brachialis tubercle is represented by a poorly convex cranial surface of the shaft. The proximal end of the lateral surface of the bone shows a flattened caudal half that is decorated by ridges, indicating strong tendinal or muscular attachments, probably for the m. supinator ( Remes 2007). The cranial half of the shaft is rounded, and lacks a surface for the anchoring of the m. adductor radialis, a condition shared with birds ( Remes 2007). In medial view, the proximal end of the bone shows two distinct areas, the cranial one is relatively smaller and is craniolaterally oriented, whereas the caudal one is medially oriented. The cranial surface attaches the m. pronator teres and the caudal surface the m. pronator quadratus ( Remes 2007).
A well-developed intermuscular line (ril 2 in Langer et al. 2007) runs from the caudolateral surface of the proximal shaft to the caudomedial margin of mid-shaft and forms a rugose crest near its distal end. The shaft is lateromedially flattened distally, as in other paravians (e.g., Velociraptor , Deinonychus ; Ostrom 1969; Norell and Makovicky 1999).
Femur: The right femur ( Fig. 4 View Fig ) is represented by a highly damaged and distorted portion of the shaft, lacking both proximal and distal ends. As it is broken, the shaft appears to be robust, resembling Laurasian dromaeosaurids. However, comparisons with Unenlagia and Buitreraptor reveal that the shaft was long and slender when complete. The proximal end is damaged and the articular head is missing. In spite to that, the preserved portion of the femoral neck and the base of the proximal end of the bone indicate that the femoral head was probably caudomedially oriented, as occurs in Buitreraptor and Unenlagia . Only the base of the lesser trochanter is discernible on the lateral surface. Due to the lack of preservation, it is not possible to assure the presence or absence of a cleft separating the lesser and greater trochanters. Nevertheless, its occurrence in Unenlagia comahuensis ( Novas and Puerta 1997) indicates that its presence is probable in Neuquenraptor . In contrast to Buitreraptor , but similar to Unenlagia and other paravians, an obturator ridge (sensu Baumel and Witmer 1993) is absent. The fourth trochanter is highly reduced and represented by a subtle, scar-like groove that is bounded by two low oblique ridges. This condition is also verified in Unenlagia , Buitreraptor , and Austroraptor . The fourth trochanter is located in an unusual proximal position on the caudal surface of the bone. Distal to this trochanter, the shaft forms a flattened proximodistally extended surface that is delimited by a well-developed longitudinal lateral ridge, as also occurs in Velociraptor ( Norell and Makovicky 1999) . This ridge constitutes the caudal (= posterior) intermuscular line of Hutchinson (2001), that delimits the boundary between the m. femorotibialis externus (craniolaterally), and the m. adductor femoris (caudomedially).
Tibia and fibula: The left tibia is represented by its distal end ( Fig. 5 View Fig ). A fragment of distal fibular shaft is still adhered on the craniolateral margin of the tibia. The latter bone exhibits a craniocaudally compressed and transversely expanded shaft. The distal end is transversely expanded. The outer malleolus is more distally projected than the medial. The outer malleolus is subrectangular in contour and is laterally delimited by a subtle proximodistally oriented rugose ridge. The medial malleolus bears a sharply marked medial margin.
The cranial surface of distal end of the tibia is nearly flat. The facet for the ascending astragalar process is extensive, with the medial surface obliquely oriented. Along the central portion of this surface there is a low proximodistally oriented mound-like ridge that separates the articular surface for the ascending astragalar process into two slightly concave areas.
The caudal surface of the distal tibia is transversely concave, forming an incipient trochlea cartilaginis tibialis sensu Baumel and Witmer 1993). In caudal view, there are two distinct flattened surfaces separated by a strong sub-vertical ridge. The lateral surface is transversely wide and slightly caudolaterally oriented, whereas the medial one is notably narrow and caudomedially faced.
In distal view, the tibia is saddle-shaped in contour with the medial portion thicker than the lateral one. Furthermore, the cranial margin of the bone is gently convex, whereas the caudal one is concave.
The fibular shaft is splint-like, representing approximately 12% of the tibial transverse diameter. It likely contacted the proximal end of the calcaneum, as in other basal paravians.
Astragalocalcaneum: The astragalus and calcaneum ( Fig. 6 View Fig ) are incomplete, but are anatomically informative. The astragalar ascending process is incompletely preserved, but fragments of it are attached to the cranial surface of distal tibia. The large and triangular facet of tibia accommodated the wide, laminar and proximodistally high ascending process of the astragalus. The base of the ascending process shows that the medial margin of the ascending process was obliquely oriented, whereas the lateral one is almost straight and vertical. At the base of the ascending process, there is a poorly defined and shallow subcircular fossa. Its base is separated from the astragalar body through a transversally oriented groove ( Welles and Long 1974) and delimits the “cranial platform of the ascending process” ( Langer and Benton 2006: 344). This groove probably served for anchoring of the m. tibialis cranialis ( Carrano and Hutchinson 2002). The main astragalar body is incomplete, lacking its lateral portion, and the calcaneum is slightly dorsally displaced. Nevertheless, the astragalar body seems to have been sub-cylindrical in contour. The astragalus is constricted at mid-length. The asymmetry of the condyles in distal view cannot be confirmed due to the incomplete nature of the lateral portion of the astragalar body. In medial view, the astragalus is ellipsoidal, whereas in Deinonychus ( Ostrom 1969) and Troodon (Russell 1969) it is sub-circular in shape. The medial surface has two shallow concavities, the ventral one being larger than the dorsal one. These concavities probably represent the “depressio epicondylaris medialis” ( Baumel and Witmer 1993: 111). In Neuquenraptor the caudal half of the astragalar body is proximodistally compressed and craniocaudally shortened, so that it does not “wrap” around the tibia.
The calcaneum is poorly preserved and most anatomical details are not available. Only the lateral and dorsal portions of the bone are preserved. It is transversely compressed and it is not fused to the astragalus. The medial surface is nearly flat and devoid of a well-defined concavity. The cranialmost margin of the calcaneum in proximal and distal views is slightly laterally tilted.
Pes: An almost complete left pes is preserved. It is represented by metatarsals I, II, III, and IV, and most of their pedal phalanges. Metatarsals II, III, and IV lack their proximal part and the distal end of metatarsal IV is missing.
The metatarsus ( Fig. 7 View Fig ) is long and slender. Metatarsals II–IV are tightly apressed each other. As is typical of most theropods, metatarsal III is the longest of the pes, with metatarsal IV and II being sub-equal in length. Metatarsal III is partially covered proximally by metatarsals II and IV, but trochlea cartilaginis tibialis medial malleolous outer malleolous still being exposed along most of the metapodium in cranial and caudal views, constituting a subarctometatarsalian pes Xu and Wang 2000; Snively et al. 2004; White 2009).
Metatarsal I ( Fig. 7E–H View Fig ) lacks its proximal end. When found, metatarsal I was lying on the caudal surface of metatarsal II. The cranial surface of the metatarsal I was caudomedially oriented. The medial pit faces caudally. In spite to that, it is uncertain if the metatarsal I occupied that position when the animal was alive. The absence on metatarsal II of a clear facet for articulation with metatarsal I results in that the orientation of the latter is difficult to assess.
Metatarsal I lacks medial or lateral torsion. The shaft is proximodistally short, representing less than 16% of metatarsal II length, and tapers proximally. In cross-section the shaft is strongly craniocaudally compressed, having a transversely expanded shaft. The distal trochlea is asymmetrical and medially twisted with respect to the main shaft. Its ascending process
A B of the astragalus C
external condyle is large and it has a transversely expanded trochlear ring. It is more distally projected than the medial condyle. The lateral ligament pit is wide and deep, which shows a bump on its proximal margin. The medial trochlear ring is barely developed, being proximodistally short. It lacks a well-developed collateral extensor pit.
Both hemicondyles are slightly medially oriented, and in cranial view they are in contact each other, lacking a deep intercondylar groove and thus resulting in a “ball-like” distal end. In caudal view, the intercondylar groove is wide and deep, and it is slightly obliquely oriented.
Metatarsal II ( Fig. 7 View Fig ) lacks its proximal end. The shaft of metatarsal II is transversely wider than that of metatarsal IV. It is nearly straight along all of its length, but flares slightly medially on its distal end. In cranial view, the distal portion of metatarsal II is covered by a well-developed medial expansion of metatarsal III. In caudal view, the distal portion of metatarsal II has a lateral expansion over the caudal surface of metatarsal III forming a flat and wide surface. Additionally, metatarsal II shows a moderately developed plantar crest that is relatively low but transversally thick. This low plantar crest gives the metatarsal shaft a subtle sub-triangular cross-section on its proximal portion.
In medial view, the proximal half of metatarsal II is craniocaudally wider than its distal half. On its distal third the medial surface of the bone is obliquely oriented and is delimited from the caudal surface by the subtle distal end of the plantar crest. This condition was not observed in Buitreraptor (MPCN-Pv-598) or Pamparaptor , in which this crest is notably more extended. Metatarsal II ends in a well-developed ginglymoid articulation with a well-developed intercondylar groove that extends along cranial and caudal surfaces. The lateral trochlear ring is incomplete. The medial one is deep and well-developed and bears a strong lateral ligament pit.
The third metatarsal ( Fig. 7 View Fig ) lacks its proximal end. Although broken, it can be observed that the proximal portion of the shaft is compressed between metatarsals II and IV. The proximal half of metatarsal III is notably craniocaudally thin. The cranial surface of the shaft shows a long extensor groove, which could represent the area of origin of the m. digitorum brevis ( Hutchinson et al. 2005). Near its distal end, the shaft has a medial expansion that partially covers the distal portion of metatarsal II. This expansion is gently concave cranially. In caudal view, the shaft of metatarsal III is ridge-like and is almost completely covered by metatarsals II and IV. It is subtriangular in cross-section.
Proximally, metatarsal III is more caudally located with respect to the shaft of metatarsals II and IV. Towards the distal end, this metatarsal is notably cranially oriented. The distal articulation is moderately ginglymoid, with a weak cranial groove. Both lateral ligament pits are well-developed and sub-equal in size and shape, being deeper than those of metatarsal II.
Metatarsal IV ( Fig. 7 View Fig ) has shaft with a proximally convex and a distally slightly concave cranial surface. The lateral surface of the metatarsal is longitudinally concave, and shows a faint longitudinal groove. This surface is deeper at mid-length as a result of the caudal extension of the plantar crest. This crest is notably deeper than that of metatarsal II. In caudal view the shaft transversely broadens towards its distal end. The caudal surface of the shaft is slightly convex and shows a longitudinal plantar crest. It is slightly medially tilted on its caudal end and delimits a concavity on the medial surface of the plantar crest. The distal end of this crest is laterally oriented, and forms the lateral margin of the metatarsal. The distal articulation was not preserved, although its base indicates that it was transversely expanded.
The first digit ( Fig. 8 View Fig ) is represented by phalanges I-1 and I-2.Phalanx I-1 is nearly completely preserved. It is relatively robust and is sub-equal in length to metatarsal I. In lateral view, the phalanx shows a dorsal concave profile. The shaft has a very narrow dorsal surface that is transversely thinner than the ventral surface. The proximal articular facet is relatively large and sub-circular in contour, lacking any sign of a median keel. This morphology is due to its articulation with the “ball-like” distal articular surface of metatarsal I, and probably it allowed a wide range of motion of this digit. The distal end of the phalanx is more transversely compressed than the proximal portion, and it is slightly asymmetrical, since the medial collateral ligament pit is smaller than the
III III lateral one. In ventral view, the proximal end of the bone is notably expanded and shows two shallow concavities for the anchoring of flexor tendons, that are separated by a poorly developed posteroventral process.
The ungual of digit I ( Fig. 9A View Fig ) is relatively short when compared with the other pedal unguals. It is transversely compressed and ventrally curved. The proximal articular facet is dorsoventrally tall and asymmetrical, in order to match the distal articular surface of the preceeding phalanx. A flexor tubercle is present, which is moderately developed and is laterally located on the proximoventral corner of the ungual. The lateral and medial surfaces of the proximal portion of the ungual bears fine longitudinal striations. Single lateral and medial grooves are nearly symmetrical, being the lateral one slightly dorsally displaced.
Pedal digit II is completely preserved ( Fig. 9B View Fig ). Phalanx II- 1 is sub-equal in length to phalanx II- 2. Phalanx II- 1 shows a straight ventral margin, whereas its dorsal margin is notably concave in lateral view. The posteroventral heel of pedal phalanx II- 1 is transversally narrow, and medially offset. The proximal articular facet is relatively tall and asymmetrical, with the medial portion dorsoventrally taller and transversely wider than the lateral one. There is a well-developed median keel separating both articular facets. The shaft is dorsoventrally compressed near the distal end, where is formed a well developed neck. The distal end shows a well-developed ginglymoid articulation with both lateral and medial trochlear margins sub-equally extended. The distal end also presents dorsally extended condyles, a feature correlated with the hyperextensible nature of pedal digit II. On the dorsal surface, a well-developed extensor fossa is present, which is nearly confluent with the well-developed cranial intercondylar groove. The lateral collateral ligament pit is well-developed and deep, being located in the middle of the outer trochlear surface, whereas the medial one is slightly shallower, and proximally it shows an additional small pit.
Phalanx II- 2 shows the typical basal paravian morphology. The phalanx shaft is dorsoventrally constricted at mid-length, forming a deep neck. The proximoventral heel is well-developed and low. It is medially offset, as in phalanx II- 1. The proximal articular facet is asymmetrical and sub-divided by a vertical median keel. The distal end is highly symmetrical. The trochlear rings are large and bear dorsally displaced collateral ligament pits, as usual among paravians. These pits are ellipsoidal in shape, being dorsoventrally low and craniocaudally elongated. The dorsal margins of these pits can be seen in dorsal view, due to a dorsal constriction of the trochlear margins.
The ungual phalanx of digit II ( Fig. 10B View Fig ) is hypertrophied as in other paravians ( Gauthier 1986). It is long, ventrally curved, and it is relatively low and narrow with a well-developed flexor tubercle. This tubercle is slightly rugose. Both lateral and medial sides of the claw bear single asymmetrical longitudinal grooves. The lateral one is more dorsally positioned than the medial one. The cutting edge of the ungual is medially displaced, and distally confluent with the medial surface of the claw, resulting in an apparently flat medial surface of the blade.
The first phalanx of digit III ( Fig. 10C View Fig ) is the largest phalanx of the pes. The ventral margin is strongly concave in lateral view, whereas the dorsal margin is gently convex. The proximal articular surface is damaged, but seems to be slightly asymmetrical and without a median keel. The shaft is dorsoventrally compressed just proximal to the distal articulation. The distal end is slightly ginglymoid. The collateral ligament pits are sub-equally developed, being deep and teardrop-shaped. The extensor fossa is crescent-shaped, notably wide, shallow, and with well-defined margins.
Phalanx III- 2 is somewhat damaged, lacking portions of its distal and proximodorsal ends. The proximal articular facet is slightly asymmetrical, with the medial facet larger than the lateral one. Both lateral and medial proximal articular facets are divided by a very low median keel. On the proximoventral corner of the phalanx, there is a shallow flexor fossa, which is medially delimited by a low and thick flexor ridge. The distal end is slightly ginglymoid. Both trochlear rings slightly converge dorsally. The extensor fossa is well-defined and relatively shallow. Both collateral ligamental pits are well-defined and moderately deep.
Phalanx III- 3 is sub-equal in length to phalanx III- 2. The proximal articular facet is nearly identical to that of phalanx III- 2, being slightly asymmetrical, but more transversely compressed. The extensor fossa is not well defined. The distal end is ginglymoid, and the trochlear margins show dorsally displaced collateral ligamental pits.
Digit IV is almost complete ( Fig. 9D View Fig ). It lacks phalanx IV- 4 and the proximal end of phalanx IV- 5. All the phalanges of the fourth digit are relatively short and stout.
The phalanx identified by Novas and Pol (2005) as pedal IV- 2 is re-interpreted here as pedal IV- 1 because of the shape of the proximal articular surface. Phalanx IV- 1 is medially tilted and its shaft narrows proximally. The dorsal surface of the shaft is transversely narrower than the ventral surface. The proximal end of the phalanx shows strong rugosities in lateral and medial views. On the proximoventral corner of the phalanx there is a well-defined and shallow flexor fossa. The proximal articular surface is dorsoventrally tall and slightly asymmetrical, with the lateral side ventrally projected. It lacks a median keel. The distal end is ginglymoid and is notably transversely expanded when compared with the proximal end of the phalanx. The trochlear margins are notably distally divergent and bear large and deep collateral ligament pits. At the caudal margin of the lateral pit there exists a small bump, as occurs on metatarsal I. The extensor fossa is shallow and sub-triangular in contour.
Phalanx IV- 2 is shorter than phalanx IV- 1. The shaft is slightly medially tilted in dorsal view. There is a weak median keel that divides the proximal articular facet in two distinct surfaces. This facet is asymmetrical, with the lateral cotyle sub-triangular in contour and laterally extended on its ventral half. Ventrally, a small flexor depression is bounded by two flexor heels on both lateral and medial sides. The shaft of the phalanx is transversely compressed on its dorsal half. The distal end is ginglymoid, with the trochlear margins bearing well-developed ligament pits. The extensor fossa is shallow and sub-triangular in contour. The medial collateral ligament pit is well developed and is caudally continuous with a slightly concave surface on the medial surface of the phalanx.
Phalanx IV- 3 is nearly sub-equal in length to the preceding phalanx, but it is notably transversely narrower. It is slightly asymmetrical when viewed in dorsal view. It main axis is obliquely oriented. The proximal articular facet is divided by a very shallow median dorsoventral keel, and has a large and laterally expanded lateral cotyle. The shaft is short and highly transversely compressed on its dorsal surface. On the medial side, and located at mid-shaft length, there is a well-developed bump ( Fig. 8A View Fig ), a feature that seems to be unique of Neuquenraptor . The distal end is ginglymoid with the trochlear rings bearing well-developed collateral ligament pits that are located on the middle of the trochlea. In the dorsal surface, the extensor fossa is shallow and poorly defined.
The ungual of digit IV is incomplete, lacking its proximal end. The claw is weakly curved, transversely compressed and lacks a cutting ventral edge. Instead, its ventral edge is represented by a flattened surface. On both lateral and medial surfaces, single, symmetrical longitudinal grooves are present. A portion of the flexor tubercle is preserved. Although incomplete, it seems to be large and rounded in contour.
Stratigraphic and geographic range.— Type locality and horizon only.
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