Leptorhynchos elegans ( Parks, 1933 )

Funston, Gregory F., Currie, Philip J. & Burns, Michael E., 2016, New elmisaurine specimens from North America and their relationship to the Mongolian Elmisaurus rarus, Acta Palaeontologica Polonica 61 (1), pp. 159-173 : 161-169

Leptorhynchos elegans ( Parks, 1933)

Figs. 1–7 , 9–10 .

Holotype: ROM 781, partial tarsometatarsus; complete left metatarsals II and IV and partial metatarsal III, partial distal tarsal III and partial distal tarsal IV.

Type locality: Dinosaur Provincial Park (Little Sandhill Creek), Canada. Type horizon: Dinosaur Park Formation (Campanian) .

Material.— Specimens from Hell Creek Formation (Upper Maastrichtian): MOR 752 , a partial left foot including a fragment of the astragalus, a partial metatarsal II, an unidentified metatarsal fragment, the distal end of phalanx II- 1, phalanx II-2, and complete digits III and IV ( MOR locality HC-147, sec. 32, T16N, R56E, Dawson County Montana, USA) ; TMP 1996.005 .0012, distal end of metatarsal III (near Jordan, Montana, USA.

Specimens from Dinosaur Park Formation (Campanian), Dinosaur Provincial Park, Canada: ROM 37163, distal portion of left metatarsal II (collected between 1920 and 1954 by a joint University of Toronto —Royal Ontario Museum expedition); TMP 1982.016 . 0006, complete right tarsometatarsus (coossified), including metatarsal V ( Wolf Coulee , legal subdivision 12, section 13, township 20, range 10, west of the 4 th Meridian); TMP 1982.039 . 0004, proximal end of right tarsometatarsus (legal subdivision 2, section 4, township 21, range 11, west of the 4 th Meridian); TMP 1984.163 . 0036, distal end of metatarsal III (legal subdivision 12, section 3, township 22, range 10, west of the 4 th Meridian); TMP 1986.036 . 0186, distal end of metatarsal III ( UTM 12 U; E 471,850, N 5,624 ,260, WGS84 ); TMP 1988.036 . 0104, distal half of metatarsal II ( UTM 12 U 0455600; 5628640); TMP 1993.036 . 0181, partial tarsometatarsus including fused distal tarsals, and metatarsals II and IV (legal subdivision 12, section 33, township 20, range 11, west of the 4 th Meridian); TMP 1993.036 . 0630, distal end of metatarsal III ( TMP Locality L 0418, Bonebed BB112 ); TMP 1994.012 . 0880, left tibia (300 m East of BB042, 10 m higher in section); TMP 1996.012 . 0141, left tarsometatarsus, including fused distal tarsals and proximal ends of metatarsals II, III, and IV, most of the shafts of metatarsals II and IV, and distal ends of metatarsals II and IV (bonebed BB047, TMP Locality L 0047, section 31, township 20, range 11, west of the 4 th Meridian); TMP 2000.012 . 0008, partial right foot including metatarsals II and III, phalanges II- 1, III-1, III-2, III-3, and IV-? 3 ( Iddelsleigh region , UTM 12U; E 473,277, N 5,623 ,497, WGS84 ); TMP 2005.049 . 0190, right metatarsal III ( UTM 12 U; E 459,250, N 5,629 ,544, WGS84 ); UALVP 55585 , distal shaft of metatarsal III used for thin-sectioning ( BB038 A) .

Description.— TMP 1994.012.0880: A crushed left tibia ( Fig. 1 ) is similar to those of Elmisaurus rarus ( Currie et al. 2016) , but there are some differences. The tibia is 280 mm long, shorter than that of MPC-D 102/007 ( Elmisaurus elegans ), but still more gracile than those of oviraptorids. The cnemial crest is laterally deflected, with a deep incisura tibialis separating it from the fibular condyle. The fibular crest has a rugose posterolateral surface, with a shallow groove for the interosseum tibiofibular ligament. There is a foramen at the distal base of this groove, as in Elmisaurus rarus , Ingenia yanshini Barsbold, 1981 , and Khaan mckennai Clark, Norell, and Barsbold, 2000 ( Balanoff and Norell 2012). The anterior surface of the shaft is flat, and the posterior surface is curved, resulting in a semi-circular shaft in cross section. The distal condyles are worn, especially the lateral (fibular) condyle, which nevertheless has a prominent postfibular flange ( Fig. 1A, D ). The contact with the ascending process of the astragalus is slightly concave mediolaterally.

ROM 781: The holotype for Leptorhynchos elegans Fig. 3C ), has been described in detail ( Parks 1933; Currie 1989), so only salient details will be noted here. The metatarsus is small but well fused, leading Currie (1989) to infer that it was a mature specimen of a small taxon. The metatarsus approaches arctometatarsalian form, with metatarsal III pinched between metatarsals II and IV. Only the most proximal part of metatarsal III is obscured in anterior view by the contact of metatarsi II and IV. The posterior (palmar) surface of metatarsal III has two longitudinal (cruciate) ridges that extend most of the height of the bone and are separated by a longitudinal sulcus. The distal articular end extends onto the posterior surface as a pair of ridges. The medial one becomes less pronounced proximally until it crosses the back of the metatarsal to become continuous with the lateral cruciate ridge. The lateral ridge from the distal articulation crosses to the medial side to meet the ventral end of the medial cruciate ridge. The intersecting “X” shape ( Fig. 4 ) is more distinct in Leptorhynchos elegans than in Elmisaurus rarus , but this distinctive feature is not present in Chirostenotes (TMP 1979.020.0001). It is also absent in all of the oviraptorids examined in the collections of the Mongolian Paleontological Center (GFF, PJC personal observations). These ridges, and the medial and lateral facets they demarcate, indicate a closer association between metatarsals II and III than between metatarsals III and IV. There is a prominent faceted posteromedial ridge on metatarsal II, which gives the metatarsus a posteriorly concave outline in cross section ( Fig. 2 ); the distal part of this ridge likely contacted metatarsal I. This posteromedial ridge is absent in Caenagnathus collinsi ( Funston et al. 2015) and is poorly developed in Chirostenotes pergracilis ( Currie and Russell 1988) . Metatarsal IV of ROM 781 has a rugose posterolateral ridge, and a sharp anteromedial ridge. The latter ridge is variably present in other elmisaurine specimens from the Dinosaur Park Formation.Distal tarsal IV is fused to the proximal surface of metatarsal IV, and its lateral margin is attenuated into a posterodorsal hook-like process. In all respects the tarsometatarsus of ROM 781 is nearly identical to Elmisaurus rarus (MPC-D 102/006, ZPAL MgD-I/127). It differs in that the proximal ends of metatarsals II and IV do not coossify as extensively posteriorly, and that the distal part of metatarsal III of ROM 781 does not have the prominent horizontal sulcus seen in MPC-D 102/006 above the distal articulation.

ROM 37163: Metatarsal II assigned by Currie (1989) to Elmisaurus elegans , is slightly smaller than ROM 781 but nearly identical otherwise. In place of the medial rugosity on metatarsal II of ROM 781, ROM 37163 has a small flange of bone in the same position. This suggests that this is the insertion for the M. tibialis cranialis, which may become stronger and more pronounced with age. In addition, the medial condylar fossa is shallower in ROM 37163 than ROM 781, likely a result of muscle development in older specimens. The posteromedial ridge is strong, as in other elmisaurines, but unlike Caenagnathus collinsi and Chirostenotes pergracilis . The development of this ridge helps to distinguish elmisaurines from other caenagnathids.

TMP 1982.016.0006: An almost complete right tarsometatarsus that lacks metatarsal I and is somewhat crushed ( Figs. 3 , 5 ). It shows that the distinct proximal fusion of ROM 781 is not a result of pathology and solidifies the presence of elmisaurines in North America. The distal tarsals are fused to each other and to the proximal face of the metatarsus. Distal tarsals III and IV are fused indistinguishably and cover the proximal surfaces of metatarsals II–IV ( Fig. 5A ). Distal tarsal IV is arched posterodorsally into a hook-like process ( Fig. 5B ), which contacts and is fused to metatarsal V. In proximal view ( Fig. 5A ), the proximal surface of the tarsometatarsus is oval in shape, but wider transversely and narrower anteroposteriorly than in Elmisaurus rarus . This is due in part to the lack of the posterior protuberance caused by the coossification of the distal tarsals and metatarsals in Elmisaurus rarus .

Metatarsal II of TMP 1982.016.0006 is straight along most of its length (152 mm), but the distal condyle is deflected medially. The proximal end is semi-circular in proximal view, and lacks the posterior protuberance of Caenagnathus collinsi ( Funston et al. 2015) . Near the proximal end of the shaft, there is an oval slit separating etatarsals II and III, but there is no separation between metatarsi III and IV proximal to this region. In Elmisaurus rarus there are two holes between the metatarsi: proximally, there is a foramen between metatarsi III and IV, and distal to this point, there is a slit between metatarsi II and III. Currie et al. (2016) suggest that the proximal slit between metatarsi II and III accommodated the a. tarsalis plantaris. It is likely that in Leptorhynchos elegans , the more distal slit between metatarsals II and III played the same role. This suggests that the proximal slit between metatarsal III and IV conducts another artery or vein. As in other elmisaurine specimens, Velociraptor mongoliensis Osborn, 1924 ( Norell and Makovicky 1997), and Confuciusornis sanctus Hou, Zhou, Martin, and Feduccia, 1995 ( Chiappe et al. 1999), there is a rugosity on both metatarsi II and IV, for the insertion of the M. tibialis cranialis, on the lateral side of the shaft just proximal to the distal condyle. The posteromedial ridge of metatarsal II bows laterally, probably to accommodate metatarsal I. There is a prominent ridge on the posterior surface of the distal condyle of metatarsal II that extends from the proximal edge of the articular surface.

As in caenagnathines and Elmisaurus rarus , metatarsal III of TMP 1982.016.0006 is the longest (172 mm) bone of the foot ( Table 1), and the shaft is widest (12.5 mm) about a quarter of its length from the distal end. Proximally, metatarsal III is fused with distal tarsal III, although a distinct suture is still present. Metatarsal III tapers dorsally on the anterior surface, and its proximal end is covered anteriorly by the contact between metatarsals II and IV. There is a horizontal groove on the anterior surface just proximal to the distal articular surface, although it is not as well developed as in MPC-D 102/006. Metatarsal III has nearly symmetrical distal condyles. On the posterior (palmar) surface of metatarsal III, there are two cruciate ridges that extend most of the height of the bone and are separated by a vertical sulcus that contributes to the deep longitudinal concavity of the tarsometatarsus. On the palmar surface, metatarsal III is thinnest at mid-height but expands dorsally to separate the proximal heads of metatarsals II and IV posteriorly.

The minimum shaft width of metatarsal IV (TMP 1982.016.0006) is wider (11.4 mm) than that of metatarsal II (8.4 mm) in anterior view. Metatarsal IV is straight along its entire length (160 mm). At its proximal end, it is wide (19.9 mm) and fused indistinguishably with distal tarsals III and IV. A well-developed anterior ridge ends just proximal to the distal condyle. Although the posterior (palmar) surface of metatarsal IV is damaged, it appears that it would have had a posterolateral ridge that would have accentuated the concave posterior surface of the tarsometatarsus. The distal condyle of metatarsal IV is rounded but broken.

Metatarsal V ( Fig. 5B ) of TMP 1982.016.0006 ( Fig. 3 ) is relatively short (44.3 mm) and splint-like, and has an anteriorly deflected distal end. Metatarsal V is straighter along its length in elmisaurines (MPC-D 102/006, TMP 1982.016.0006) than in caenagnathines ( Currie and Russell 1988) and other theropods ( Currie and Peng 1993). It is fused to the hooklike posterodorsal process of distal tarsal IV, and closely associated but not fused with metatarsal IV proximally.

TMP 1982.039.0004: A fused proximal tarsometatarsus described by Currie (1989). The proximal ends of those metatarsi have coossified and are fused with the distal tarsals. Distal tarsal IV has a hook-like posterodorsal process that would have contacted and fused with metatarsal V. Currie (1989) notes that the shape of the proximal face of the tarsometatarsus has a posteromedial emargination that is not seen in Elmisaurus rarus . This emargination is present to a lesser degree in other specimens of Leptorhynchos elegans (TMP 1993.036.0181; TMP 1996.012.0141), but it may serve to distinguish Leptorhynchos from Elmisaurus . This feature is not present in TMP 1982.016.0006, probably because of post-mortem crushing. Posteriorly, between metatarsals III and IV, there is a rounded hole, which probably accommodated the a. tarsalis plantaris. The second slit between metatarsals II and III, which are completely fused, cannot be seen, but it may have been situated more distally.

TMP 1993.036.0181: A pathological partial metatarsus, including metatarsals II and IV and the coossified distal tarsals III and IV ( Figs. 3 , 6 ). It is the largest elmisaurine tarsometatarus recovered from Alberta ( Table 1), comparable in size with “ Macrophalangia canadensis ” (CMN 8538). Metatarsal II is 221 mm in length, and if the proportions are similar between TMP 1982.016.0006 and TMP 1993.036.0181, the total length of the tarsometatarsus would exceed 250 mm. The shaft of metatarsal II is mediolaterally expanded by a large tuberosity of twisted bone ( Fig. 6B, C ). Two holes pierce the distal shaft near the tuberosity, one on the medial side oblique to the shaft, and one on the lateral side parallel with the long axis of the shaft. Metatarsal IV is 221 mm long and appears unaffected by the pathology. Distal tarsal III covers metatarsals II and IV ( Fig. 6A ) and is fused to both, although there is a suture between distal tarsal III and metatarsal II. Distal tarsal IV has the posterodorsal process typical of elmisaurines, although metatarsal V is missing, so it is unclear if they were fused. The proximal tarsometatarsus is 50 mm wide transversely, narrower than “ Macrophalangia ” despite the greater lengths of the metatarsi.

The proximal end of metatarsal II is coossified with metatarsal IV but not metatarsal III, as indicated by the clean bone surface on the facet for metatarsal III. The shaft of metatarsal II is pathologically deformed, but the posteromedial ridge is still discernable. The distal condyle is rounded and faces ventrolaterally. The shaft of metatarsal IV has a prominent anterior ridge, separated from the facet for metatarsal III by a groove. The distal condyle faces laterally, and there is a poorly developed scar for the insertion of the M. tibialis cranialis. The proximal end of metatarsal IV TMP 1993.036.0181) is separated from metatarsal II posteriorly by the wedge-shaped proximal end of metatarsal III, which is missing. These bones apparently had not coossified or fused, as the edge between metatarsals II and IV is natural, despite the great size (> 250 mm) of the tarsometatarsus.

TMP 1996.012.0141: Another partial tarsometatarsus Fig. 3 ), includes distal tarsals III and IV and metatarsals II, III, IV. The distal tarsals are fused without visible sutures to metatarsals II, III, and IV, and the posterodorsal process of distal tarsal IV is present but worn. Most of the shafts of metatarsals II and IV are preserved, as well as the distal condyles of each. Metatarsal II is fused to distal tarsal III and proximally to metatarsals III and IV, and there is a suture between metatarsals II and III. The shaft of metatarsal II has a well-developed and rugose posteromedial ridge, and a distinct facet for metatarsal III extends onto the anterior face of the shaft. The distal condyle is rounded and bulbous, and has a distinct lateral rugosity proximal to the distal condyle for M. tibialis cranialis with a medial rugosity opposite it.

Metatarsal III of TMP 1996.012.0141 is preserved only proximally, where it is appressed between metatarsals II and IV, to which it is fused. It is triangular in cross section, but the anterior wedge does not separate metatarsals II and IV anteriorly, as it does in Elmisaurus rarus .

Metatarsal IV of TMP 1996.012.0141 is fused indistinguishably with metatarsals II and IV and distal tarsals III and IV at its proximal end. There is a strong anteromedial ridge on the shaft, and a well-developed posterolateral ridge. The shaft is teardrop-shaped in cross section as a result. The distal condyle is gnarled and rugose, with a prominent medial rugosity for M. tibialis cranialis.

TMP 2000.012.0008: A partial foot ( Fig. 7 ), provides information on the pedal anatomy of Leptorhynchos elegans that was formerly unknown. The specimen includes partial distal tarsals III and IV, metatarsals II and III, and seven pedal phalanges, including two pedal unguals. As in Elmisaurus rarus , distal tarsals III and IV are fused to the proximal ends of metatarsals II and III. Metatarsals II and III are preserved in articulation, although there is a small gap between their shafts that would not have been present in life. The proximal end of metatarsal II is roughly trapezoidal in anterior view where it contacted metatarsal IV in life, and tapers distally in medial view. The facet on metatarsal II for the contact with the expanded distal half of metatarsal III invades the anterior surface of metatarsal II, creating a sharp ridge. A small, triangular sheet of bone adheres to the proximal end of metatarsal II on the medial surface; it also contacts metatarsal III, and possibly distal tarsal III. The identification of this fragment is unknown, and it presumably does not belong in this position. The posteromedial ridge of metatarsal II is well defined and has a flat, rugose facet ( Fig. 7B, D ). The insertion for the M. tibialis cranialis is visible just proximal to the distal condyle of metatarsal II, as in other elmisaurines. The distal end of metatarsal II is medially inflected to a greater degree than other specimens, but faces ventromedially.

Metatarsal III of TMP 2000.012.0008 is preserved in its entirety, including the proximal end, which tends to break off in isolated specimens. In lateral view, the proximal end of metatarsal III tapers distally, whereas in anterior view it expands distally. Metatarsal III is inclined longitudinally so that its anterior surface is posterior to the anterior surface of metatarsal II for the proximal two thirds of its length, but is anterior to the distal end of metatarsal II ( Fig. 7D ). Unlike other elmisaurine specimens, the posteromedial ridge of metatarsal III (the medial cruciate ridge) is poorly developed. Instead of a horizontal sulcus on the anterior surface of the bone proximal to the distal condyle, the flat surface of the shaft has two small rugosities marking the insertion of the M. tibialis cranialis. The distal condyle of metatarsal III is symmetrical.

The phalanges preserved with TMP 2000.012.0008 ( Fig. 7E–G ) appear to represent at least a portion of each digit. The distal condyles of all of the phalanges are relatively smaller than those of Chirostenotes pergracilis (CMN 1149, CMN 8538) and do not extend dorsally above the margin of the shaft. Digit two ( Fig. 7E ) has one proximal phalanx and the ungual phalanx, but lacks II-2. Phalanx II-1 is elongate and asymmetrical, with a single ventral ridge and a depression above the distal condyles. The proximal end is damaged, but the bone is longer than III-1. The ungual phalanx (II-3) is long and flat, with a pentagonal proximal articular surface. On the ventral surface there is a fossa bisected by a median protuberance for attachment of the flexor ligaments. The ungual is deflected medially, but the tip is missing.

The third pedal digit of TMP 2000.012.0008 ( Fig. 7F ) is complete, with four phalanges including a small ungual III- 4. Phalanx III-1 is the largest preserved, and is symmetrical mediolaterally. The dorsal surface is flat, although there is a depression proximal to the distal condyles. The proximal articular surface is deeply concave and oval, although the proximal surface extends ventromedially and ventrolaterally (reflecting ridges on the ventral surface of the bone). Phalanx III-2 is nearly identical in shape and morphology to III-1, except that it is smaller, and the proximal articular surface is semicircular in cross section and lacks the ventromedial and ventrolateral extensions. Pedal III-3 is elongate and symmetrical, but lacks the dorsal depression proximal to the distal condyles. The proximal articular surface is kidney-shaped, with a shallow ventral invagination. The ungual (III-4) is similar to but smaller than II-3, but is not medially deflected. It is long and straight and has a similar ligamentous fossa and protuberance on the ventral surface.

The fourth digit of TMP 2000.012.0008 ( Fig. 7G ) is represented by a single phalanx. It is neither IV-1 nor IV-4 based on morphology, and the ratio of its length (22.3 mm) to the rest of the phalanges suggests it is IV-2. The proximal end is symmetrical, and the distal end is asymmetrical, with almost no shaft in between.

MOR 752: Varricchio (2001) described a partial foot (MOR 752) from the Hell Creek Formation that he referred to “ Elmisaurus ” elegans . The morphology of the foot has been well described, and it shares several features with Leptorhynchos elegans from Alberta. Left metatarsal II is about 135 mm long, but the medial side of the proximal end is missing, so its fusion to the rest of the tarsometatarsus cannot be evaluated. The lateral side of the shaft has a facet for metatarsal III and suggests that metatarsal II excluded the third from the anterior surface proximally. Above the distal condyle, there is a rugose knob for M. tibialis cranialis, as in Leptorhynchos elegans and Elmisaurus rarus . The posteromedial ridge of metatarsal II is not as well developed as in other elmisaurine specimens, but this may be explained by the small size of the specimen. Interestingly, Varricchio (2001) notes that the penultimate phalanges of the third and fourth digits are longer than those immediately proximal to them. This is untrue for Leptorhynchos elegans from the Dinosaur Park Formation, as demonstrated by TMP 2000.012.0008, where the penultimate phalanx of the third digit is shorter than the one immediately proximal to it. Varricchio (2001) suggests that the elongation of the penultimate phalanges is an adaptation for a grasping foot, which is therefore less developed in the Leptorhynchos elegans from Alberta. Although it is possible that this is evidence against the referral of MOR 752 to Leptorhynchos elegans , it is more conservative to include it until it can be definitively separated.

Isolated elmisaur metatarsals: Six isolated metatarsal IIIs ( Fig. 8 ) and one isolated metatarsal II attributable to Leptorhynchos elegans have been recovered from North America. Metatarsals III (TMP 1984.163.0036, TMP 1986.036.0186, TMP 1993.036.0630, TMP 1996.005.0012, TMP 2005.049.0190, and UALVP 55585) all include the distal portions of the shafts. Invariably, the shaft is flat anteroposteriorly, and expands mediolaterally towards the distal end. The posterior surface has two cruciate ridges (medial and lateral), which are continuous with the lateral and medial postcondylar ridges ( Fig. 4 ). In each case, the crossing of these ridges forms a chiasmata, distinctive enough to identify them as elmisaurine. Where the distal condyle is present, it is invariably thicker anteroposteriorly than wide mediolaterally, a feature that distinguishes Leptorhynchos elegans from Elmisaurus rarus and Chirostenotes pergracilis .

One of these metatarsals, UALVP 55585 ( Fig. 9 ), was thin-sectioned to determine its histological age. The specimen represents the distal portion of the shaft, which is anteriorly concave and has well-developed, paired cruciate ridges ( Fig. 9C ). The minimum transverse shaft width is 11.4 mm, which is intermediate in size compared to other isolated elmisaurine metatarsals III.

The thin-sectioned metatarsal III ( Fig. 9D ) shows an average relative bone wall thickness (RBT) of 40% of the diameter; however, cortical thickness varies from 0.088 mm at the anterior cortex to 0.267 mm in the anterolateral corners of the cross-section. The cortex exhibits roughly equal quantities of primary fibrolamellar and secondarily remodeled Haversian bone; however, they are not distributed evenly throughout the cortex. The highest proportion of Haversian bone occurs in the thicker anteromedial and anterolateral corners of the cortex. Blood vessel canals in the primary bone show predominantly longitudinal orientations. There is a thin (0.016 mm) region along the periosteal surface of the medial cortex consisting of more highly vascularized primary woven-fibered bone with simple longitudinal blood vessel canals. No cyclical growth marks were observed anywhere in the cortex, including an external fundamental system. An inner circumferential layer, composed of avascular parallel-fibered bone, is present lining the entire wall of the medullary cavity, although it is variable in thickness.

Isolated metatarsal II (TMP 1988.036.0104) has several characters that distinguish it as Leptorhynchos elegans . Unfortunately only the distal half is preserved, so it is unclear if the proximal end was fused to the other metatarsals. The facet for metatarsal III invades the anterior face of the shaft, as in other elmisaurines, and there is a distinct Canada. RSM P2161.1, complete left metatarsal II. Upper Maastrichtian Frenchman Formation, Grasslands National Park, Canada. Collected by Kevin Conlin in 1989.

lateral rugosity for M. tibialis cranialis, a feature absent in Chirostenotes . The distal shaft is deflected anteriorly, and there is a large, well-developed posteromedial ridge with a rugose apex. The strong development of the posteromedial ridge and the rugosity for M. tibialis cranialis are features that appear to be present only in elmisaurines, so they can be used to identify metatarsals II of the group.

Stratigraphic and geographic range.—Upper Campanian DinosaurParkFormation,DinosaurProvincialPark, Alberta, Canada, to Upper Maastrichtian Hell Creek Formation, Montana, USA.

Figures

Fig. 1. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (TMP 1994.012.0880) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Left tibia in anterior (A), posterior (B), proximal (C), and distal (D) views.

Fig. 2. Cross section demonstrating the deep plantar concavity of the tarsometatarsus of elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (ROM 781) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada.

Fig. 3. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. A. TMP 1993.036.0181. B. TMP 1982.016.0006. C. ROM 781. D. TMP 1996.012.0141. Tarsometatarsi in proximal (A1–D1), anterior (A2–D2), and posterior (A3–D3) views.

Fig. 4. Posterior surface of metatarsal III in elmisaurine dinosaurs. A. Leptorhynchos elegans (Parks, 1933) (TMP 1986.036.0186) from Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. B. Chirosenotes pergracilis Gilmore, 1924 (TMP 1979.020.0001) from Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. C. Ingenia yanshini Barsbold, 1981 (MPC-D 102/011), provenance unknown: confiscated specimen. Photographs (A1–C1), annotated photographs (A2–C2), black lines indicate longitudinal ridges; arrow indicates cruciate ridge feature of Leptorhynchos elegans.

Fig. 5. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (TMP 1982.016.0006) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Right tarsometatarsus in proximal (A), anterior (B), posterior (C), and distal (D) views.

Fig. 6. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (TMP 1993.036.0181) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Right tarsometatarsus in proximal (A), anterior (B), posterior (C), and distal (D) views.

Fig. 7. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (TMP 2000.012.0008) from Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Partial foot, articulated metatarsals II and III in anterior (A), posterior (B), medial (C), and lateral (D) views. Pedal phalanges of digits II (E), III (F), and IV (G) in dorsal (E1–G1), lateral (E2–G2), and ventral (E3–G3) views. Reconstruction of foot in anterior view (H).

Fig. 9. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) (UALVP 55585) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. Metatarsal III in anterior (A), posterior (B), and cross-sectional (C) views. D. Full petrographic thin section in proximal cross-sectional view (anterior is up). E–G. Details of D. E. Thin anterior cortex showing development of the inner circumferential layer. F. Posterior cortex showing extent of secondary bone relative to primary bone. G. Anteromedial corner showing localized development of highly vascularized periosteal bone. Images in plane-polarized light (D, E, G) and 90° cross-polarized light (F).

Fig. 10. Elmisaurine dinosaur Leptorhynchos sp. from Upper Maastrichtian Frenchman Formation, Saskatchewan, Canada. A. RSM P2600.1, distal portion of left tibia and astragalocalcaneum in posterior (A1), lateral (A2), and medial (A3) views; distal portion of right second metatarsal in anterior (A4) and posterior (A5) views; distal portion of third metatarsal in anterior (A6), posterior (A7), and distal (A8) views. B. RSM P2161.1, left second metatarsal in anterior (B1), medial (B2), posterior (B3), lateral (B4), distal (B5), and proximal (B6) views.

Fig. 8. Elmisaurine dinosaur Leptorhynchos elegans (Parks, 1933) from the Upper Campanian Dinosaur Park Formation, Dinosaur Provincial Park, Alberta, Canada. A. TMP 1995.403.0010. B. TMP 1984.163.0036. C. TMP 1986.036.0186. D. TMP 1996.5.12. Isolated metatarsals III in anterior (A1– D1), posterior (A2–D2), and lateral (A3–D3) views.