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A redescription of Ornithomimus velox Marsh, 1890 (Dinosauria, Theropoda). Journal of Vertebrate Paleontology
Abstract
The theropod genus and species Ornithomimus velox was erected based on a partial hind limb recovered from the late Maastrichtian Denver Formation. A partial manus, which likely belonged to the same individual, was also recovered and described in the same paper. Ornithomimus edmontonicus is the only other valid species currently recognized in the genus. The validity of Ornithomimus velox has been questioned due to its fragmentary nature and because the diagnostic features identified when the species was erected are now considered characteristic for the family. The pes and manus of Ornithomimus velox were never fully prepared. In the original description, reconstructed metatarsals were figured, but manual phalanges, although preserved, were not described. Here we describe and reevaluate Ornithomimus velox based upon a new preparation of the specimen. Metacarpal proportions are diagnostic for the genus, with metacarpal I longer than metacarpal II, which in turn is longer than metacarpal III. The pes and manus of Ornithomimus velox are smaller than in the type specimen of Ornithomimus edmontonicus. Ornithomimus velox can be distinguished from Ornithomimus edmontonicus based on the robusticity of the pes. Material previously referred to Ornithomimus velox from the Kaiparowits Formation of Utah is older and morphologically distinct and does not represent the same species. The morphological disparity and temporal separation observed in specimens referred to Ornithomimus edmontonicus suggest that it may represent a species complex. The redescription and diagnosis of Ornithomimus velox provides a new framework to investigate ornithomimid systematics.
... New detailed descriptions of historic material have also been provided (e.g. Kobayashi & Barsbold, 2005a, b;Lee et al., 2014;Claessens & Loewen, 2016). Among the vast ornithomimosaurian record, the axial and appendicular skeletons are altogether well represented. ...
... Pérez-Moreno & Sanz, 1995; Kobayashi & Lü, 2003;Kobayashi & Barsbold, 2005a), with an intercondylar groove between the well-developed medial and lateral condyles. This latter condition is distinct from the shallowly developed intercondylar groove and non-ginglymoid condition observed in some derived ornithomimosaurs, such as Anserimimus (MCP-D 100/300; Kobayashi & Lü, 2003) or Ornithomimus velox (Claessens & Loewen, 2016). The medial and lateral articular condyles are evenly developed in size in dorsal view, distinct to those unevenly condyles observed in Nqwebasaurus (De Klerk et al., 2000;Choiniere et al., 2012), Harpymimus (MPC-D 100/29), the Bisskety taxon (Sues & Averianov, 2016), Deinocheirus (MPC-D 100/18; Osmólska & Roniewicz, 1970), Ornithomimus velox (Claessens & Loewen, 2016), Anserimimus (MPC-D 100/300) and Gallimimus (MPC-D 100/11; Osmólska et al., 1972). ...
... This latter condition is distinct from the shallowly developed intercondylar groove and non-ginglymoid condition observed in some derived ornithomimosaurs, such as Anserimimus (MCP-D 100/300; Kobayashi & Lü, 2003) or Ornithomimus velox (Claessens & Loewen, 2016). The medial and lateral articular condyles are evenly developed in size in dorsal view, distinct to those unevenly condyles observed in Nqwebasaurus (De Klerk et al., 2000;Choiniere et al., 2012), Harpymimus (MPC-D 100/29), the Bisskety taxon (Sues & Averianov, 2016), Deinocheirus (MPC-D 100/18; Osmólska & Roniewicz, 1970), Ornithomimus velox (Claessens & Loewen, 2016), Anserimimus (MPC-D 100/300) and Gallimimus (MPC-D 100/11; Osmólska et al., 1972). The medial ligamental pit is deeply excavated and rounded. ...
Pelecanimimus polyodon was discovered in 1993 in the Spanish Barremian fossil site of Las Hoyas, being the
first ornithomimosaur described from Europe. So far, there has been no detailed description of the holotype
of Pelecanimimus, which is composed of the anterior-half of an articulated skeleton. Here we report a new,
detailed, revised and more accurate osteological description of its postcranial skeleton, comparing this new
data to information about Ornithomimosauria from the last three decades. This osteological and phylogenetic
analysis of Pelecanimimus shows several ornithomimosaur synapomorphies and a unique combination of
characters that emend its original diagnosis. Pelecanimimus diverged early in Ornithomimosauria and reveals
an enlargement trend of the manus, shared with derived ornithomimosaurians, due to a long metacarpal I and
elongated distal phalanges. This evolutionary novelty, and other synapomorphies, has led to the definition of a
new clade, Macrocheiriformes, including Pelecanimimus and more derived ornithomimosaurs. Pelecanimimus has
the only ossified sternal plates among ornithomimosaurs and the first evidence of uncinate processes in a nonmaniraptoran theropod, indicating a convergent appearance of these structures in Coelurosauria. The character
combination in an early-diverging ornithomimosaur like Pelecanimimus found in this analysis provides a key
step in the evolution of the manus and pectoral girdle in Ornithomimosauria
... Here, we describe the specimen collected by Friday as a new Early Cretaceous ornithomimosaur. The ornithomimo- saur record is poor in North America, with more specimens better represented in Late Cretaceous units (Osborn, 1917;Gilmore, 1920;Sternberg, 1933;Ostrom, 1970;Russell, 1972;Nicholls and Russell, 1981;DeCourten and Russell, 1985;Sullivan, 1997;Longrich, 2008;Cullen et al., 2013;SerranoBra~ nas et al., 2015;Claessens and Loewen, 2016). The Arkansas fossils consist of a partial right pes, including metatarsals II, III, and IV, pedal phalanges II-1, III-1, III-2, and IV-1, and three pedal unguals. ...
... Measure- ments were taken on the specimen using digital calipers. This paper follows the terminology used by Claessens and Loewen (2016) for consistency, using 'Romerian' anatomical and direc- tional terms over veterinary alternatives (Wilson, 2006 Holotype-UAM 74-16, partial right pes, including metatar- sals II, III, and IV, pedal phalanges II-1, III-1, III-2, and IV-1, and three pedal unguals. ...
... PD II-1 is slightly longer than PD III-1 and is the longest of the preserved pedal phalanges. In the pedal pha- langes, PD II-1 has a proximal articular facet that is concave and diverges medially, more so than what is seen in Ornithomimus velox and Beishanlong, and is more similar to the condition in Harpymimus andGarudimimus (Kobayashi andBarsbold 2005a, 2005b;Makovicky et al., 2010;Claessens and Loewen, 2016). (Fig. 4G). ...
Whereas ornithomimosaurs (ostrich-mimic dinosaurs) are well known from Asia during the Early Cretaceous, they are less well known from this time in North America. Represented by a single specimen consisting of pedal elements, a new North American taxon, Arkansaurus fridayi, gen. et sp. nov., consists of a nearly complete right foot, recovered from the Lower Cretaceous (Albian–Aptian) Trinity Group of Arkansas. Arkansaurus fridayi can be distinguished from other ornithomimosaurs based on differentiated pedal unguals, a laterally compressed third metatarsal that is ovoid in proximal view, and a distal ungual with a very weak flexor tubercle, lacking spurs. The condition of this third metatarsal suggests that Arkansaurus fridayi is more basal than Asiatic ornithomimosaurs of similar age, but consistent with older North American forms. This specimen provides knowledge of a poorly understood radiation of ornithomimosaurs in Appalachia and is the only known saurischian dinosaurian fossil from the state of Arkansas.
http://zoobank.org:pub:EB6910D3-A66D-43FE-A2F6-3BFF4A7B347C
Citation for this article: Hunt, R. K., and J. H. Quinn. 2018. A new ornithomimosaur from the Lower Cretaceous Trinity Group of Arkansas. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1421209.
... The Fairpoint phalanx also possesses morphological features observed in the proximal pedal phalanges of various ornithomimids. These characteristics, which are also represented in tyrannosaurids, include a shallowly concave proximal articular facet (Kobayashi & Barsbold, 2005;Cullen et al., 2013;Osmólska, Roniewicz & Barsbold, 1972;Chinzorig et al., 2017); a shallow extensor fossa (Shapiro et al., 2003, Although DMNH EPV.138575 is significantly larger, the specimen shares similarities with phalanx II-1 of Ornithomimus velox of the late Maastrichtian Denver Formation (Claessens & Loewen, 2015;Figs. 5, 6 and 8;YPM 548). ...
... Dissimilarities in pedal phalanx II-2 of the stratigraphically similar North American Ornithomimus velox (YPM 548) indicate either a tentative assignment of YPM VP.061705 to Ornithomimidae or reveal undocumented variation in pedal phalangeal morphology within the clade. Phalanx II-2 of O. velox is stouter with a greater width to length ratio than YPM VP.061705, and a notably shorter shaft, a less exaggerated distal condyle relative to shaft diameter in lateral view, a shallower ligament fossa, and a more acute narrowing of the distal condyle dorsally (Claessens & Loewen, 2015;Fig. 8). ...
We report here the first dinosaur skeletal material described from the marine Fox Hills Formation (Maastrichtian) of western South Dakota. The find consists of two theropod pedal phalanges: one recovered from the middle part of the Fairpoint Member in Meade County, South Dakota; and the other from the Iron Lightning Member in Ziebach County, South Dakota. Comparison with pedal phalanges of other theropods suggests strongly that the Fairpoint specimen is a right pedal phalanx, possibly III-2, from a large ornithomimid. The Iron Lightning specimen we cautiously identify as an ornithomimid left pedal phalanx II-2. The Fairpoint bone comes from thinly bedded and cross-bedded marine sandstones containing large hematitic concretions and concretionary horizons. Associated fossils include osteichthyan teeth, fin spines and otoliths, and abundant teeth of common Cretaceous nearshore and pelagic chondrichthyans. Leaf impressions and other plant debris, blocks of fossilized wood, and Ophiomorpha burrows are also common. The Iron Lightning bone comes from a channel deposit composed of fine to coarse sandstone beds, some of which contain bivalves, and a disseminated assemblage of mammal teeth, chondrichthyan teeth, and fragmentary dinosaur teeth and claws. We interpret the depositional environment of the two specimens as marginal marine. The Fairpoint bone derives from a nearshore foreset setting, above wave base subject to tidal flux and storm activity. The Iron Lightning specimen comes from a topset channel infill probably related to deposition on a tidal flat or associated coastal setting. The taphonomic history and ages of the two bones differ. Orthogonal cracks in the cortical bone of the Fairpoint specimen suggest post-mortem desiccation in a dryland coastal setting prior to transport and preservation in the nearby nearshore setting described above. The pristine surface of the Iron Lightning specimen indicates little transport before incorporation into the channel deposit in which it was found. The Fairpoint bone bed most probably lies within the Hoploscaphites nicolletii Ammonite Zone of the early late Maastrichtian, and would therefore have an approximate age of 69 Ma. The Iron Lightning bone is from the overlying H. nebrascensis Ammonite Zone, and is thus about one million years younger.
... The ornithomimids from the Kaiparowits Formation have not yet been fully described, and their relationship with other taxa in North America at the time is still unexplored (Zanno et al. 2013). Claessens and Loewen (2016) suggested they may be referable to Ornithomimus sp., but this has not yet been tested in detail. ...
... Marsh (1890) originally depicted the Ornithomimus velox holotype, YPM 542, with a series of three round bones atop the metatarsals that were interpreted as the distal tarsals at the time. Yet, the distal tarsals were largely missing in the specimen when it was redescribed (Claessens and Loewen 2016). Two small fragments of bone remain atop the metatarsus of Ornithomimus velox, situated on the posterior proximal surfaces of metatarsals II and IV and leaving metatarsal III completely uncovered (REN personal observation). ...
The ankle in non-avian theropod dinosaurs consists of the astragalus and calcaneum proximally and a distal series of tarsal bones capping the metatarsals. Nearly all theropods have only two distal tarsals, identified as distal tarsal 3 and distal tarsal 4. Historically, the morphology and anatomical relationships of these distal tarsals is uncertain in ornithomimosaurs due to loss and/or disarticulation; even in articulated specimens, the bones can be difficult to access. A previously undescribed ornithomimid fossil from the Kaiparowits Formation (upper Campanian) of southern Utah, USA, provides
unique views of the distal tarsals in articulation with their surrounding elements, allowing the most complete assessment yet of this region in an ornithomimid from North America. Distal tarsal 3 contacts both metatarsals II and III, whereas distal tarsal 4 contacts only metatarsal IV. Distal tarsal 4 also shows a tab-like process that projects laterally. Comparison of the new fossil with other ornithomimosaurs shows that distal tarsals in Ornithomimosauria can be generalized as: (i) paired as distal tarsals 3 and 4; (ii) not fused to one another or to the proximal metatarsus; and (iii) proximo-distally compressed. The distal tarsals of ornithomimosaurs vary in the antero-posterior positioning and extent to which theycover the proximal metatarsal surface.
... The condition in YPM VPPU.021795 cannot be explained by ontogeny, as the holotype of Appalachiosaurus, a subadult, possesses a deepened notch at the proximal end of metatarsal II [22], as do immature specimens of Albertosaurus [66] and Bistahieversor [67]. A deep facet at the proximal end of metatarsal II also appears in some ornithomimids, including Quipalong, Aepyornithomimus and Ornithomimus velox [60,61,69]. ...
... This condition is also present in some ornithomimids (e.g. [60,61,69,73,74]). Dryptosaurus and the Merchantville tyrannosauroid possess a different configuration wherein metatarsal III lacks developed diaphysial bulge, maintains its mediolateral width in dorsal view throughout its proximodistal run, and is only dorsally obscured at the proximal end of the metatarsus. ...
During the Cretaceous, diversifications and turnovers affected terrestrial vertebrates experiencing the effects of global geographical change. However, the poor fossil record from the early Late Cretaceous has concealed how dinosaurs and other terrestrial vertebrates responded to these events. I describe two dinosaurs from the Santonian to Early Campanian of the obscure North American paleolandmass Appalachia. A revised look at a large, potentially novel theropod shows that it likely belongs to a new clade of tyrannosauroids solely from Appalachia. Another partial skeleton belongs to an early member of the Hadrosauridae, a highly successful clade of herbivorous dinosaurs. This skeleton is associated with the first small juvenile dinosaur specimens from the Atlantic Coastal Plain. The tyrannosauroid and hadrosaurid substantiate one of the only Late Santonian dinosaur faunas and help pinpoint the timing of important anatomical innovations in two widespread dinosaur lineages. The phylogenetic positions of the tyrannosauroid and hadrosaurid show Santonian Appalachian dinosaur faunas are comparable to coeval Eurasian ones, and the presence of clades formed only by Appalachian dinosaur taxa establishes a degree of endemism in Appalachian dinosaur assemblages attributable to episodes of vicariance.
... The medial concavity is deeper than lateral one. The corresponding edge of DT-III is almost straight in Garudimimus, but is convex in Gallimimus and the Bissekty ornithomimid [33][34][35][36] . Moreover, the overall shape of DT-III is triangular with a straight medial edge in proximal view, whereas it is quadrangular with a convex medial edge in other ornithomimosaurs. ...
... Besides these characters, Aepyornithomimus tugrikinensis is differentiated all other ornithomimosaurs by following characters; unevenly developed pair of concavities present at posterior edge of the DT-III of Aepyornithomimus tugrikinensis. This morphology is different from any other ornithomimosaurs where posterior edge is either convex or concave [32][33][34][35] ; the proximoventral ridge of II-1 is round, II-3 is relatively larger than the other two unguals, and the pedal unguals are anteroposteriorly more slender and curve slightly downward. ...
The Upper Cretaceous Djadokhta Formation has been intensively surveyed for its fossil vertebrate fauna for nearly a century. Amongst other theropods, dromaeosaurids and parvicursorines are common in the formation, but ornithomimosaurs are extremely rare. A new ornithomimosaur material was discovered from the Djadokhta Formation, represented by eolian deposits, of the Tögrögiin Shiree locality, Mongolia. This is only the third ornithomimosaur specimen reported from this formation, and includes the astragalus, the calcaneum, the third distal tarsal, and a complete pes. The new material is clearly belonged to Ornithomimidae by its arctometatarsalian foot condition and has the following unique characters; unevenly developed pair of concavities of the third distal tarsal, curved contacts between the proximal ends of second and fourth metatarsals, the elongate fourth digit, and a laterally inclined medial condyle on phalanx IV-1. These diagnostic characters of the Djadokhtan ornithomimosaur indicate that this is a new taxon. Our phylogenetic analysis supports three clades within derived ornithomimosaurs, and the new taxon is placed a member of the derived ornithomimosaurs. The present specimen is the first ornithomimid record from eolian Tögrögiin Shiree locality, and is indicative of their capability to adapt to arid environments.
... planinychus + O. edmontonicus) clade excluding Qiupalong. However, a comparison of published measurements of ornithomimid metatarsals (Parks 1933;Sternberg 1933;Osmólska et al. 1972;Russell 1972;Barsbold 1988;Xu et al. 2011;Claessens and Loewen 2015) suggests that the variation in this ratio is not split between two discrete character states, and just as much variation can occur between specimens of a single taxon or even between different authors' measurements of the same specimen. The metatarsal II/IV ratio derived from measurements of O. edmontonicus (CMN 8632) by Claessens and Loewen (2015, appendix 1) is indistinguishable from that of Q. henanensis, as measured by Xu et al. (2011, table 1). ...
... 6d), Ornithomimus sp. (TMP 1995.110.1), and O. velox (Claessens and Loewen 2015, fig. 8c) the posterior expansion has a more pronounced ventral border distinct from the shaft, and the transition from the proximal expansion to the vertical posterior border of the shaft is abrupt. ...
Ornithomimid material from the Belly River Group (Campanian) of Alberta, Canada is described as sharing characters with Qiupalong henanensis from the Qiupa Formation of Henan Province, China. Derived characters and character combinations of the pubis and astragalocalcaneum were previously used to diagnose Q. henanensis and support the referral of this material to Qiupalong sp., representing the first known occurrences of Qiupalong outside of China. Qiupalong is the sixth orni- thomimid taxon to be reported from the Dinosaur Park Formation and the first ornithomimid genus with a transcontinental distribution. The Alberta material represents the oldest known occurrences of Qiupalong, and a reconsideration of character evidence suggests that this genus is phylogenetically nested within other North American ornithomimids. A North American origin for Qiupalong and subsequent dispersal to Asia is proposed.
... The pubis has a similar appearance in most ornithomimosaurs, but in Archaeornithomimus asiaticus AMNH 21799 and Ornithomimus sp. MNA P1.1762A the distal part of the pubic shaft is sharply curved rather than straight (Decourten and Russell, 1985;Smith and Galton, 1990;Claessens and Loewen, 2015). The distal part of the pubis is also slightly curved in Harpymimus okladnikovi, Garudimimus brevipes and even Shenzhousaurus orientalis, but not nearly to the degree seen in Archaeornithomimus asiaticus (Smith and Galton, 1990;Ji et al., 2003;Kobayashi and Barsbold, 2005a, b). ...
A newly identified ornithomimosaurian pelvis and sacrum from the Upper Cretaceous Erlian Formation of Nei Mongol, China is described in detail in this paper. This specimen is distinguished from previously described taxa by the presence of a combination of features that is unique among Ornithomimosauria: sacrum comprising five vertebrae with neural spines fused into a continuous plate, iliac posterior end rectangular, pubic shaft distally straight, ischial boot not broadened transversely, and ischial shaft proximally straight, distally curved, and 80 percent as long as the pubis. This specimen differs from at least some material assigned to the sympatric Archaeornithomimus asiaticus, showing that two distinct ornithomimosaurian taxa are present in this Late Cretaceous fossiliferous rock unit. A phylogenetic analysis places LH-02-01 in a relatively early-diverging position within Ornithomimosauria, outside the two major clades Deinocheiridae and Ornithomimidae, but its relationships with other early-diverging ornithomimosaurs remain unresolved. The primitive nature of LH-02-01 adds to the evidence from fossil vertebrates that the Erlian Formation correlates with the Turonian Bissekty Formation of Uzebekistan, while the biostratigraphic evidence from non-vertebrates instead indicates a Campanian to Maastrichtian age for the Erlian Formation. This apparent contradiction remains unresolved, pending future research aimed at reconciling the seemingly incompatible lines of evidence.
... In any case, similar pedal morphology (Farlow et al., 2013) and growth rates (Erickson et al., 2004) indicate that tracks made by species of Gorgosaurus, Daspletosaurus, and Albertosaurus would likely be comparable in their growth trajectories. (Fig. 8C, D) The taxonomic affinity of small-to-medium tridactyl theropod footprints (such as Th.Tw1.4.6B) is complicated by the presence of at least one indeterminate ornithomimid within the Wapiti Formation (Ryan and Russell, 2001;Weishampel et al., 2004;Fanti and Miyashita, 2009) and at least three ornithomimid genera identified from the Horseshoe Canyon Formation (Ryan and Russell, 2001;Cullen et al., 2013;Claessens and Loewen, 2015;Macdonald and Currie, 2018). Based on North American ornithomimid pedes that are reasonably complete (e.g., Osborn, 1916;Cullen et al., 2013) and using these to scale more fragmentary, but larger specimens (see Longrich, 2008: fig. ...
Fossil tracks should theoretically capture differences in pedal anatomy between growth stages of the same taxon, particularly those related to the soft tissue of the foot, providing a more realistic view of pedal ontogeny than skeletal material alone. However, recognizing these ontogenetic trajectories is complicated by the influence of preservation and kinematics on track morphology, as well as the inherent difficulty of referring different tracks to a single taxon. Here, we explore differences in track morphology from a collection of tracks attributed to tyrannosaurids from Unit 4 of the Wapiti Formation (upper Campanian) in western Canada. Along with morphology, close geographic and stratigraphic associations suggest that the tracks pertain to similar tyrannosaurid trackmakers. A geometric morphometric analysis of the track outlines reveals size-dependent increase in relative track robusticity, driven primarily by an increase in 'heel' breadth and surface area. This relationship is lost when the dataset is expanded to include tyrannosaurid tracks globally, which we attribute to increased stratigraphic and taxonomic 'noise' within the global dataset that masks the tightly constrained patterns obtained from the Wapiti Formation tracks. Although there is some substrate and kinematic influence on certain aspects of track morphology, we hypothesize that the observed size-dependent relationship reflects genuine expansion in the breadth of the heel soft tissues and probably their overall surface area associated with growth. Increased pedal robusticity likely assisted with weight bearing and locomotor stability as body mass increased over ontogeny, supporting previous hypotheses that some tyrannosaurids underwent a growth-related reduction in relative agility and/or cursorial performance.
... Similarly, some of the morphological characteristics that Funston et al. (2015) used to distinguish the second metatarsals they describe from those of Chirostenotes pergracilis and Citipes elegans are similar in some ways to ornithomimids. These include the well-developed posterior process on the proximal end, which is similar to those of Ornithomimus velox (Claessens and Loewen 2016) and Struthiomimus altus (Osborn, 1917). The termination of the articular facet for metatarsal III near the midpoint of the metatarsal is also more similar to ornithomimids than other caenagnathids, which have a less well-developed arctometatarsalian condition than ornithomimids (Snively et al. 2004), and therefore have more anterior exposure of metatarsal III. ...
Our understanding of caenagnathid anatomy, diversity, and ecology has improved considerably in the past twenty years, but numerous issues still remain. Among these, the diversity and taxonomy of caenagnathids from the Dinosaur Park Formation of Alberta, Canada, have remained problematic. Whereas some authors recognize three genera, others suggest only two were present, and there is considerable disagreement about which specimens are referable to which genus. This study aims to resolve this issue by reviewing the known specimens and using osteohistology, to establish a testable taxonomic framework of Dinosaur Park Formation caenagnathids. Numerous new specimens from all regions of the skeleton provide insight into morphological variation in caenagnathids, and three morphotypes are recognized based on a combination of morphological features and body size. Osteohistology shows that representatives in each body size class are at skeletal maturity, and therefore supports the delineation of three taxa: the smaller Citipes elegans gen. nov., the intermediate Chirostenotes pergracilis, and the larger Caenagnathus collinsi, new material of which shows it rivalled Anzu wyliei in size. However, these analyses also raise concerns about the referral of isolated material to each taxon in the absence of skeletal overlap between specimens or osteohistological analysis. Caenagnathids are consistently recovered throughout the Dinosaur Park Formation interval, and two geographic clusters of increased abundance probably reflect collection and taphonomic biases. The coexistence of three taxa was apparently facilitated by differences in both adult body size and functional morphology of the dentary and pes, which suggests that caenagnathids minimized niche overlap rather than subdividing niche space. Regardless, little is known of the exact roles caenagnathids played in Late Cretaceous ecosystems. Incorporation of the new material and taxonomic framework into a phylogenetic analysis drastically improves our understanding of the relationships between caenagnathines, and sheds light on the evolution of body size in caenagnathids and its role in their diversification.
... Members of this group show high morphological variation in their manual structures, the phalangeal proportions and the shapes of their unguals, including curvature and robustness. These variations may be related to functional diversity (Osmόlska et al., 1972;Russell, 1981, 1985;Makovicky et al., 2004;Barsbold, 2005a, 2005b;Choiniere et al., 2012;Lee et al., 2014;Claessens and Loewen, 2016). ...
... Members of this group show high morphological variation in their manual structures, the phalangeal proportions and the shapes of their unguals, including curvature and robustness. These variations may be related to functional diversity (Osmόlska et al., 1972;Russell, 1981, 1985;Makovicky et al., 2004;Barsbold, 2005a, 2005b;Choiniere et al., 2012;Lee et al., 2014;Claessens and Loewen, 2016). ...
The Upper Cretaceous Nemegt Formation of Mongolia is rich in well-preserved dinosaurs and Ornithomimosauria is one of the most common taxa in the formation. Three ornithomimosaur taxa, Anserimimus planinychus, Deinocheirus mirificus, and Gallimimus bullatus, have been discovered from the formation so far. However, the recently discovered specimens suggest there is even greater morphological variation of ornithomimosaurs in the Nemegt Formation than are presently recognized. This study focuses on the structures of manual elements among Nemegt ornithomimosaurs and reveals their remarkable diversity. The manual structures of seven individuals, including aforementioned three known taxa and four new individuals, are morphologically distinct from each other. Numerical analyses on metacarpals, phalanges, and unguals also support high morphological diversity of the Nemegt ornithomimosaurs. The large diversity of manual morphology may be related to large variety of palaeoecological niches were prevailed in the Nemegt ecosystem.
... The known portion of the metatarsal III described by Lull (1911) andGilmore (1920) suggests that at least one ornithomimosaur taxon found at the Arundel had a subarctometatarsalian condition similar to that of Kinnareemimus and derived ornithomimosaurs (e.g. Makovicky, Kobayashi & Currie, 2004;Buffetaut, Suteethorn & Tong, 2009;Claessens & Loewen, 2015), while in Nedcolbertia the dorsal face of metatarsal III is still completely visible along the entire portion of the metatarsus. Additional differences between the derived Arundel ornithomimosaur material and Nedcolbertia include the presence of noticeable flexor tubercles on the manual unguals of the latter taxon and the slightly more recurved nature of the derived Arundel ornithomimosaur's pedal unguals in comparison with those of Nedcolbertia. ...
The fossil record of dinosaurs from the Early Cretaceous of Eastern North America is scant, especially since a few stratigraphic units from the east are fossiliferous. Among these stratigraphic units, the Arundel Clay of the eastern seaboard has produced the best-characterized dinosaur faunas known from the Early Cretaceous of Eastern North America. The diverse dinosaur fauna of the Arundel Clay has been thoroughly discussed previously, but a few of the dinosaur species originally described from the Arundel Clay are still regarded as valid genera. Much of the Arundel material is in need of review and redescription. Among the fossils of dinosaurs from this stratigraphic unit are those referred to ornithomimosaurs. Here, the researcher describes ornithomimosaur remains from the Arundel Clay of Prince George’s County, Maryland which may be from two distinct ornithomimosaur taxa. These remains provide key information on the theropods of the Early Cretaceous of Eastern North America. Recent discoveries of small theropod material from the Arundel Clay possibly belonging to ornithomimosaurs are also reviewed and described for the first time. The description of the Arundel material herein along with recent discoveries of basal ornithomimosaurs in the past 15 years has allowed for comparisons with the coelurosaur Nedcolbertia justinhofmanni , suggesting the latter animal was a basal ornithomimosaur rather than a “generalized” coelurosaur as it was originally described. Comparisons between the Arundel ornithomimosaur material and similar Asian and European specimens suggest that both extremely basal ornithomimosaurs and more intermediate or derived forms may have coexisted throughout the northern hemisphere during the Early Cretaceous.
... Russell (1972:table 7) also included some measurements of the postcranial skeleton, demonstrating the proportional similarity between ROM 1790 and other specimens referred to S. altus. Measurements of ROM 1790 have been used in various other studies (Holtz, 1995;Gatesy and Middleton, 1997;Currie, 2000;Rainforth, 2003;Kobayashi and Barsbold, 2005a;Cullen et al., 2013;Claessens and Loewen, 2015), but the anatomy of ROM 1790 remains otherwise undescribed, and the specimen has never been figured outside of Russell's composite skull reconstruction. This paper describes the anatomy of ROM 1790 in greater detail and compares it with other ornithomimids in order to reevaluate its taxonomic placement. ...
A partial ornithomimid skeleton, ROM 1790, from the lower Dinosaur Park Formation (upper Campanian) of Alberta was previously referred to Struthiomimus altus, but lacks diagnostic characters of that species. It is here described as the holotype of a new species, Rativates evadens, gen. et sp. nov., diagnosed by the form of the maxilla-jugal contact, the reduction of the mid-caudal neural spines, the convex fusion of the left and right ischial shafts, the straight-edged distal end of the third metatarsal, and possibly the relatively enlarged medial condyle of the tibia. A histological section of the femur confirms that the type specimen is not a juvenile, despite its relatively small size (approximately 50% the size of large individuals of Struthiomimus altus). Phylogenetic analysis recovers Rativates as a member of a derived ornithomimid clade that includes Ornithomimus, Struthiomimus, and the Asian taxa Anserimimus and Qiupalong. Fusion of the proximal tarsals to the tibia in some ornithomimid specimens was observed to be more complete than previously recognized, increasing the suite of features that these non-avian dinosaurs share homoplastically with birds. http://zoobank.org/urn:lsid:zoobank.org:pub:E0163526-7C26-4E8C-90C9-C72A3E90ED2D SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: McFeeters, B., M. J. Ryan, C. Schröder-Adams, and T. M. Cullen. 2016. A new ornithomimid theropod from the Dinosaur Park Formation of Alberta, Canada. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1221415. 2016
Reconstructing the evolution, diversity, and paleobiogeography of North America's Late Cretaceous dinosaur assemblages require spatiotemporally contiguous data; however, there remains a spatial and temporal disparity in dinosaur data on the continent. The rarity of vertebrate-bearing sedimentary deposits representing Turonian-Santonian ecosystems, and the relatively sparse record of dinosaurs from the eastern portion of the continent, present persistent challenges for studies of North American dinosaur evolution. Here we describe an assemblage of ornithomimosaurian materials from the Santonian Eutaw Formation of Mississippi. Morphological data coupled with osteohistological growth markers suggest the presence of two taxa of different body sizes, including one of the largest ornithomimosaurians known worldwide. The regression predicts a femoral circumference and a body mass of the Eutaw individuals similar to or greater than that of large-bodied ornithomimosaurs, Beishanlong grandis, and Gallimimus bullatus. The paleoosteohistology of MMNS VP-6332 demonstrates that the individual was at least ten years of age (similar to B. grandis [~375 kg, 13-14 years old at death]). Additional pedal elements share some intriguing features with ornithomimosaurs, yet suggest a larger-body size closer to Deino-cheirus mirificus. The presence of a large-bodied ornithomimosaur in this region during this time is consistent with the relatively recent discoveries of early-diverging, large-bodied ornithomimosaurs from mid-Cretaceous strata of Laurasia (Arkansaurus fridayi and B. grandis). The smaller Eutaw taxon is represented by a tibia preserving seven growth cycles, with osteohistological indicators of decreasing growth, yet belongs to an individual approaching somatic maturity, suggesting the coexistence of medium-and large-bodied ornithomimosaur taxa during the Late Cretaceous Santonian of North America. The Eutaw ornithomimosaur materials provide key information on the diversity and distribution of North American ornithomimosaurs and Appalachian dinosaurs and fit with broader evidence of PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.
Herein we report the first caenagnathid dinosaur (Theropoda, Oviraptorosauria) material from the Upper Cretaceous Cerro del Pueblo (CdP) Formation of Coahuila, Mexico, comprising three partial tibiae. Caenagnathids are an unusual group of oviraptorosaur theropod dinosaurs mostly known by way of their toothless, beak-like jaws. Fossils ascribed to Caenagnathidae are well-known from many Late Cretaceous localities in Asia and North America, with a high number of specimens found in the mid-latitudes of North America. The postcranial material described in this study represents the southernmost Laramidian locality in which caenagnathids have been found to date and adds to the scant number of caenagnathid fossils found in southern North America. Overall, these discoveries underscore the high diversity of the dinosaurian fauna found in the CdP Formation.
Despite an abundance of ornithomimid fossils from the Late Cretaceous of Alberta, Canada, only isolated elements are known from the upper Maastrichtian Scollard Formation. Ornithomimus velox and Struthiomimus sedens are the two taxa recognized from penecontemporaneous formations in the U.S.A., but the incomplete nature of these specimens and the lack of contemporary material from Alberta creates a gap in our understanding of ornithomimid diversity during the late Maastrichtian of North America. Here, I describe the first diagnostic ornithomimid fossils from the upper Maastrichtian Scollard Formation of central Alberta, Canada, providing new information about the taxonomic composition of North American ornithomimids during the late Maastrichtian. The first fossil, an articulated forelimb, exhibits metacarpal ratios and features of the manual unguals that support its referral to the genus Ornithomimus. The second fossil, an associated hind limb, belongs to a large-bodied ornithomimid, and based on characteristics of the pedal unguals is assigned to the genus Struthiomimus. Based on these taxonomic designations, the stratigraphic ranges of both Ornithomimus and Struthiomimus are extended from the upper Campanian Dinosaur Park Formation through to the upper Maastrichtian Scollard Formation of Alberta, which constitutes more than 10 million years of time. These specimens offer new knowledge on the taxonomic composition of ornithomimids in Alberta, but the unusually long stratigraphic range coupled with the difficulty in diagnosing either specimen to species underscores the need for review of North American ornithomimid taxonomy.
Isolated metatarsals III and IV of a caenagnathid theropod likely referable to Anzu wyliei are described from a locality of the Hell Creek Formation in northwestern South Dakota of the U.S.A. These bones are missing from the holotype and only partial shafts have been described for a specimen referable to this species. Accordingly, the present description adds further anatomical information on this already well-known species of Caenagnathidae. The present finding also demonstrates the significance of isolated or fragmentary specimens found in multitaxic bone beds.
A characteristic fauna of dinosaurs and other vertebrates inhabited the end-Cretaceous European archipelago, some of which were dwarves or had other unusual features likely related to their insular habitats. Little is known, however, about the contemporary theropod dinosaurs, as they are represented mostly by teeth or other fragmentary fossils. A new isolated theropod metatarsal II, from the latest Maastrichtian of Spain (within 200,000 years of the mass extinction) may represent a jinfengopterygine troodontid, the first reported from Europe. Comparisons with other theropods and phylogenetic analyses reveal an autapomorphic foramen that distinguishes it from all other troodontids, supporting its identification as a new genus and species, Tamarro insperatus. Bone histology shows that it was an actively growing subadult when it died but may have had a growth pattern in which it grew rapidly in early ontogeny and attained a subadult size quickly. We hypothesize that it could have migrated from Asia to reach the Ibero-Armorican island no later than Cenomanian or during the Maastrichtian dispersal events.
Dromiceiomimus brevitertius is a North American ornithomimid diagnosed primarily by the ratio of tibia length to femur length. It has recently, and perhaps incorrectly, been considered synonymous with Ornithomimus edmontonicus, with several authors questioning the utility of limb ratios in diagnosing taxa. While isolated ornithomimosaur material is common, specimens with sufficient diagnostic material to explore the question of synonymy are comparatively rare. The putative Dromiceiomimus specimen UALVP 16182 represents one of the few specimens in which diagnostic elements are available. It is therefore an important specimen for assessing the validity of Dromiceiomimus and for examining the utility of using limb proportions to diagnose ornithomimid taxa. In this paper, UALVP 16182 is described, the tibia/femur ratio is examined in closely related ornithomimid taxa, and the ratio is found to distinguish Dromiceiomimus from Gallimimus, Ornithomimus, and Struthiomimus. A phylogenetic analysis recovered Anserimimus and Ornithomimus as sister taxa with Dromiceiomimus as an outgroup. Comparison of the manus revealed differences in the morphology of metacarpal I and the flexor tubercle of manual ungual II-3. Differences also appear in the surangular and scapula. An examination of stratigraphic positions of various specimens indicates that Dromiceiomimus is generally higher in section than Ornithomimus, although there are too few specimens to be statistically significant. This study agrees with other studies in concluding that limb proportions are roughly isometric in small theropods like ornithomimids and that the tibia/femur ratio may therefore be useful for diagnosing certain small taxa. These findings suggest that Dromiceiomimus may indeed be a valid taxon.
Ornithomimosauria is a group of medium to large, lightly built theropods that are mainly known from Cretaceous sediments of central Asia and western North America. This chapter examines the diagnostic features, evolution, and paleobiology, and phylogenetic relationships among ornithomimid taxa. Ornithomimosaurs are represented by Pelecanimimus, Gallimimus, Garudimimus, Ornithomimus, Struthiomimus, Harpymimus, Archaeornithomimus, Shenzhousaurus, and Anserimimus. They are characterized by short, delicate skulls, elongate forelimbs with a weak, nonraptorial manus, and long hindlimbs. The chapter also compares the biogeographic history of ornithomimosaurs within the broader context of several other dinosaur groups that display a predominantly Asian-North American distribution during the Cretaceous.
We performed additional preparation on the holotype skeleton of Nqwebasaurus thwazi and discovered new skeletal material. We describe this material, which includes a maxilla with small, conical, unserrated teeth and bones of the braincase, as well as parts of the holotype postcranial anatomy that were previously poorly documented. We incorporate this new anatomical information into a broadly sampled matrix designed to test theropod relationships. Our phylogenetic results hypothesize that Nqwebasaurus is the basalmost ornithomimosaur, and recover numerous characters supporting this relationship, including features of the maxilla, frontal, dentition, axial skeleton, forelimb and hindlimb. Nqwebasaurus is the first African ornithomimosaur and the first Gondwanan member of this group known from articulated skeletal material, supporting the hypothesis that coelurosaurian groups were cosmopolitan during their early evolutionary history. The presence of reduced dentition and a gastric mill in Nqwebasaurus strongly suggest that this taxon was herbivorous.
At least fourteen ornithomimid skeletons were recovered from the Upper Cretaceous Ulansuhai Formation in Nei Mongol (Inner Mongolia) Autonomous Region of China. They are assigned to a new genus and species. Sinornithomimus dongi. The anatomy of the species is described. Comparative and phylogenetic studies of ornithomimosaurs prove that these skeletons represent a new taxon that is more derived than Archaeornithomimus and more basal than the clade of [(Anserimimus + Gallimimus) + [Struthiomimus + (Dromiceiomimus + Ornithomimus)]]. The phylogenetic analysis suggests that the structure of the hand is similar to Archaeornithomimus and represents an intermediate condition between the primitive (Harpymimus) and the derived (Anserimimus. Gallimimus, Struthiomimus, Dromiceiomimus, and Ornithomimus) conditions. The monophyly of Ornithomimidae is supported by a single synapomorphy (arctometatarsalian condition) in this analysis, indicating that the family is not as strongly supported as previously suggested. The analysis also implies that the shape of the rhamphotheca in North American taxa may have been different from that in Asian taxa. Previous study suggests herbivorous habits of this dinosaur based on characteristics of the gastroliths. The skeletons of Sinornithomimus were collected from a single monospecific bonebed with a high ratio of juvenile individuals (11 of the 14), suggesting gregarious behavior for protection from predators. The abundance of juveniles indicates high mortality of juveniles or a catastrophic mass mortality of a population with a high proportion of juveniles. An increase in the relative ratio of the tibia to femur through the ontogeny of Sinornithomimus suggests higher cursoriality in adult individuals than in juveniles.
The Cretaceous theropod families Ornithomimidae, Tyrannosauridae, Troodontidae, Elmisauridae, and Avimimidae share an unusual condition of the metatarsus. The central (third) metatarsal is greatly reduced proximally, completely excluded from anterior view and nearly to completely excluded in dorsal aspect. This bone forms a wedge shape distally, triangular in transverse cross section, which is buttressed against the more columnar metatarsals II and IV. This morphology forms a tightly bound structure, here termed the arctometatarsalian condition.Morphometric analysis indicates that the arctometatarsalian structure is significantly more elongate and gracile than underived metatarsi, and this structure is associated with relatively elongate distal hind limbs per unit femoral length. When compared with limb proportions of modern and extinct mammals and flightless birds, these limb proportions are seen to be consistent with a hypothesis of enhanced cursoriality in the derived theropods. In some genera, intrametatarsal mobility in this structure may have served as an energy storage system analogous to the snap-ligaments of modern equids. The wedge-and-buttress morphology would have resulted in a more direct transmission of locomotory forces to the epipodium than in less derived theropods. Biomechanical analysis indicates that this type of relatively gracile pes was not significantly weaker than pedes of underived theropods with regards to bending stresses, due to elongation into the parasagittal plane. To the contrary, these metatarsi were well designed to withstand the forces and stresses associated with enhanced cursorial ability.
Postcranial remains of a small theropod dinosaur, including vertebrae, incomplete pubes, tibiae, an incomplete fibula, metatarsals and phalanges, from the Early Cretaceous Sao Khua Formation of Phu Wiang, Khon Kaen Province, NE Thailand, are described as a new taxon of ornithomimosaur, Kinnareemimus khonkaenensis, gen. et sp. nov. This early 'ostrich dinosaur' is characterized by a fairly advanced metatarsus, in which metatarsal III, although still visible proximally between metatarsals II and IV in cranial view, is markedly 'pinched' more distally and becomes triangular in cross-section. The condition of its metatarsus shows that Kinnareemimus khonkaenensis is more derived than the geologically younger primitive ornithomimosaurs Harpymimus and Garudimimus, but less derived than Archaeornithomimus. Its occurrence in the Early Cretaceous of Thailand suggests that advanced ornithomimosaurs may have originated in Asia.
Laser-fusion 40Ar/39Ar analysis of four bentonite horizons produces the first absolute ages for the 860-m-thick Kaiparowits Formation and resolves previous age uncertainty caused by ambiguous biostratigraphy. A late Campanian (Judithian) age of ca. 76.1–74.0Ma is determined, resulting in a high-resolution temporal framework for the richly fossiliferous formation. Detailed stratigraphic correlation reveals that the Kaiparowits Formation is contemporaneous with many of the most important vertebrate fossil-bearing formations in the Western Interior Basin, and with other well-studied strata across Utah and southeastern Wyoming, including portions of the Book Cliffs sequence. The Judithian age determination and correlations for the Kaiparowits Formation presented here provide a new chronological basis for addressing questions relating to mammal biostratigraphy, vertebrate evolution, biodiversity and paleobiogeography (e.g., dinosaur provincialism) in the Cretaceous Western Interior Basin.
We report the well preserved skeleton of a small theropod dinosaur, Nqwebasaurus thwazi, gen. et sp. nov., from the Lower Cretaceous Kirkwood Formation of South Africa. Nqwebasaurus has an elongate three-digit manus with a partially opposable first digit, a long and slender pes with a highly reduced metatarsal IV, and preserves gastroliths (stomach stones) in its abdominal region. As a basal coelurosaurian, Nqwebasaurus pushes back the Gondwanan record of this derived group of tetanuran theropods approximately 50 million years. This confirms that coelurosaurians were present on the Gondwana supercontinent well before its main phase of fragmentation and supports the hypothesis that this clade could have achieved a global distribution early in their evolution. Nqwebasaurus is one of the most complete and best preserved Cretaceous theropods described thus far from Africa.
Whereas the anatomy of birds, domesticated mammals, and humans is described by standardized terminology, the anatomy of most fossil vertebrates is described by nonstandardized terminology. New fossil discoveries increasingly resolve the transitions between these living groups and their fossil outgroups, diminishing morphological differences between them, and vertebrate paleontologists can easily apply more than one system of anatomical terms to such groups. This plurality of systems has led to recent proposals to standardize anatomical terminology for tetrapods, either by applying avian and mammalian anatomical terminology to their respective stem groups (Sauropsida and Synapsida) or by creating an all-encompassing terminology for Tetrapoda from a combination of existing terminologies. The main rationale for implementing standardized anatomical terminology, which requires abandoning competing terminologies, is that it reflects homology and evolutionary descent, eliminates ambiguity, and enhances interdisciplinary communication. The proposed standardized anatomical terminology, however, entails many negative consequences, including reversing character trajectories, misrepresenting complex anatomical transformations and uncertain homologies, and requiring far-reaching terminological conversions. These negative consequences result from increasing the taxonomic scope of standardized anatomical terms that were developed for a specific group, but now: (1) apply to a broader hierarchy of character states; (2) involve additional phylogenetic interpretations or assumptions; and (3) are used for basal, often more generalized conditions. In contrast, traditional non-standardized anatomical terminology, although not strictly phylogenetic, is anatomical ‘lingua franca’ that has been in usage for nearly two centuries and is consistent, ubiquitous, and descriptive.
Did dinosaurs grow in a manner similar to extant reptiles, mammals or birds, or were they unique? Are rapid avian growth rates an innovation unique to birds, or were they inherited from dinosaurian precursors? We quantified growth rates for a group of dinosaurs spanning the phylogenetic and size diversity for the clade and used regression analysis to characterize the results. Here we show that dinosaurs exhibited sigmoidal growth curves similar to those of other vertebrates, but had unique growth rates with respect to body mass. All dinosaurs grew at accelerated rates relative to the primitive condition seen in extant reptiles. Small dinosaurs grew at moderately rapid rates, similar to those of marsupials, but large species attained rates comparable to those of eutherian mammals and precocial birds. Growth in giant sauropods was similar to that of whales of comparable size. Non-avian dinosaurs did not attain rates like those of altricial birds. Avian growth rates were attained in a stepwise fashion after birds diverged from theropod ancestors in the Jurassic period.
Whereas the anatomy of birds, domesticated mammals, and humans is described by standardized terminology, the anatomy of most fossil vertebrates is described by nonstandardized terminology. New fossil discoveries increasingly resolve the transitions between these living groups and their fossil outgroups, diminishing morphological differences between them, and vertebrate paleontologists can easily apply more than one system of anatomical terms to such groups. This plurality of systems has led to recent proposals to standardize anatomical terminology for tetrapods, either by applying avian and mammalian anatomical terminology to their respective stem groups (Sauropsida and Synapsida) or by creating an all-encompassing terminology for Tetrapoda from a combination of existing terminologies. The main rationale for implementing standardized anatomical terminology, which requires abandoning competing terminologies, is that it reflects homology and evolutionary descent, eliminates ambiguity, and enhances interdisciplinary communication. The proposed standardized anatomical terminology, however, entails many negative consequences, including reversing character trajectories, misrepresenting complex anatomical transformations and uncertain homologies, and requiring far-reaching terminological conversions. These negative consequences result from increasing the taxonomic scope of standardized anatomical terms that were developed for a specific group, but now: (1) apply to a broader hierarchy of character states; (2) involve additional phylogenetic interpretations or assumptions; and (3) are used for basal, often more generalized conditions. In contrast, traditional non-standardized anatomical terminology, although not strictly phylogenetic, is anatomical ‘lingua franca’ that has been in usage for nearly two centuries and is consistent, ubiquitous, and descriptive.
Fragmentary, but partially well-preserved, remains of Ornithomimus velox are recognized for the first time as a component of the dinosaur fauna of the late Maastrichtian Kaiparowits Formation of southern Utah. This specimen enhances the current understanding of the skeletal morphology of the species previously known only from an incomplete type specimen. The discovery of Ornithomimus velox in the Kaiparowits Formation supports the terminal Cretaceous (Lancian) age assigned to this unit on the basis of fossil palynomorphs.-Authors
The holotype of Deinocheirus mirificus was collected by the 1965 Polish-Mongolian Palaeontological Expedition at Altan Uul III in the southern Gobi of Mongolia. Because the holotype consists mostly of giant forelimbs (2.4 m in length) with scapulocoracoids, for almost 50 years Deinocheirus has remained one of the most mysterious dinosaurs. The mosaic of ornithomimosaur and non-ornithomimosaur characters in the holotype has made it difficult to resolve the phylogenetic status of Deinocheirus. Here we describe two new specimens of Deinocheirus that were discovered in the Nemegt Formation of Altan Uul IV in 2006 and Bugiin Tsav in 2009. The Bugiin Tsav specimen (MPC-D 100/127) includes a left forelimb clearly identifiable as Deinocheirus and is 6% longer than the holotype. The Altan Uul IV specimen (MPC-D 100/128) is approximately 74% the size of MPC-D 100/127. Cladistic analysis indicates that Deinocheirus is the largest member of the Ornithomimosauria; however, it has many unique skeletal features unknown in other ornithomimosaurs, indicating that Deinocheirus was a heavily built, non-cursorial animal with an elongate snout, a deep jaw, tall neural spines, a pygostyle, a U-shaped furcula, an expanded pelvis for strong muscle attachments, a relatively short hind limb and broad-tipped pedal unguals. Ecomorphological features in the skull, more than a thousand gastroliths, and stomach contents (fish remains) suggest that Deinocheirus was a megaomnivore that lived in mesic environments.
A high-resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous) of southern Alberta provides evidence for at least three dinosaurian assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom to top the zones comprise unique assemblages of ornithischians and are named as follows: (1) Edmontosaurus regalis – Pachyrhinosaurus canadensis (lower zone); (2) Hypacrosaurus altispinus – Saurolophus osborni (middle zone); and (3) Eotriceratops xerinsularis (upper zone). Whereas the lower and middle zones are well defined and based on abundant specimens, the validity of the uppermost zone (E. xerinsularis) is tentative because it is based on a single specimen and the absence of dinosaur taxa from lower in section. The transition from the lower to the middle zone coincides with the replacement of a warm-and-wet saturated deltaic setting by a cooler, coastal-plain landscape, characterized by seasonal rainfall and better-drained substrates. Whereas changes in rainfall and substrate drainage appear to have influenced the faunal change, changes in mean annual temperature and proximity to shoreline appear to have had little influence on faunal change. We speculate that the
faunal change between the middle and upper zones also resulted from a change in climate, with ornithischian dinosaurs responding to the re-establishment of wetter-and-warmer climates and poorly-drained substrates. Compared with the shorter duration and climatically-consistent dinosaurian assemblage zones in the older Dinosaur Park Formation of southern Alberta, HCFm assemblage zones record long-term morphological stasis in dinosaurs. Furthermore, the coincidence of faunal and paleoenvironmental changes in the HCFm suggest climate-change-driven dinosaur migrations into and out of the region.
The family Ornithomimidae is defined on the basis of the skeletal morphology of the three genera Ornithomimus, Struthiomimus, and Dromiceiomimus known in continental strata in Alberta, which are temporally equivalent to the Upper Campanian substage. At least two genera occur in Canadian Lance (Upper Maestrichtian) equivalent strata, but cannot be identified at present. A group of more primitive ornithomimoid theropods is represented else-where by the late Jurassic Elaphrosaurus and early Cretaceous Archaeornithomimus.Ornithomimid attributes include a general body form which parallels that of the ratites; elongate forelimbs, a kinetic skull, enormous eyes, a relatively highly evolved brain, and possibly a secondary palate and supertemporal fenestrae which were nearly encircled by alae of the squamosal. A reconstruction of the myology of the thigh indicates that ornithomimids were extremely fleet, but lacked the agility characteristic of modern large ground birds. They probably subsisted on small, soft-bodi...
A new specimen of Struthiomimus altus is described from the Oldman Formation of Alberta. Ossified xiphisternal structures are present, which are similar to the posterolateral processes of the sternum of some birds. The gastralia are found to consist of two, rather than three, overlapping segments. Four genera of Upper Cretaceous ornithomimids are recognized: Struthiomimus, Ornithomimus, Dromiceiomimus, and Gallimimus. The structure of the manus is found to be the most reliable character suite distinguishing them. Dromiceiomimus, however, can still be distinguished only on the basis of limb proportions, and its recognition remains tentative until further material is forthcoming. Refs.
The Denver Basin preserves >800 m of Laramide synorogenic strata, which record basin accommodation, orogenic topography, and resultant orographic climatic effects. The basin also records the Cretaceous-Tertiary boundary event and the subsequent recovery of terrestrial ecosystems. Outcrops in the basin are modest and commonly consist of temporary construction-related excavations. The Denver Museum of Nature & Science has coordinated a decade-long multidisciplinary program that includes paleontological research, stratigraphic studies, aquifer analyses, and basin evolution studies in this area. As part of this effort, the synorogenic strata were continuously cored in 1999. Unusually diverse floras exhibiting rainforest physiognomy, episodic sedimentation linked to pulsed orogeny, and stratigraphic controls on aquifer distribution and quality have emerged from beneath the urbanizing landscape. Results of this work, summarized in painted reconstructions, have helped Colorado residents and museum visitors gain insight into past climates and settings, and have helped inform decisions regarding the ongoing development of the region.
Three classifications of the Dinosauria have been proposed, which differ from each other in the principles on which their authors proposed to make the divisions. First in time is Professor Cope’s classification (‘Philadelphia, Acad. Nat. Sci. Proc.,’ November 13th, 1866, and December 31st, 1867; ‘Amer. Phil. Soc. Trans.,’ vol. 14, Part I). He relied upon the characters of the tarsus and the ilium; and on their varied condition divided Dinosaurs into three orders named Orthopoda, Goniopoda, and Symphopoda. In the Orthopoda , the generic types associated are Scelidosaurus, Hylæosaurus, Iguanodon, and Hadrosaurus. And in this group the relations of the tibia and fibula are compared to those of modern Lizards, the proximal tarsals being distinct from each other and from the tibia. The ilium has a narrowed anterior prolongation.
A fragment of the proximal phalanx of a wing finger (IV) from the Oldman Formation (Campanian) of Alberta probably represents the first record of a pterosaur from Canada. The animal from which it was derived had a wingspan of about 3.5 m.
Mass extinctions manifest in Earth's geologic record were turning points in biotic evolution. We present 40Ar/39Ar data that establish synchrony between the Cretaceous-Paleogene boundary and associated mass extinctions with the Chicxulub
bolide impact to within 32,000 years. Perturbation of the atmospheric carbon cycle at the boundary likely lasted less than
5000 years, exhibiting a recovery time scale two to three orders of magnitude shorter than that of the major ocean basins.
Low-diversity mammalian fauna in the western Williston Basin persisted for as little as 20,000 years after the impact. The
Chicxulub impact likely triggered a state shift of ecosystems already under near-critical stress.
A partial skeleton of the ornithomimid dinosaur, discovered from the Late Cretaceous Qiupa Formation of Luanchuan County, Tantou Basin, Henan Province, China, is described here and assigned to a new genus and species, Qiupalong henanensis, with unique features (a notch on the lateral surface of the lateral posterior process of the proximal end of tibia and a small pit at the contact between astragalus and calcaneum). A phylogenetic analysis in this study suggests that it is a derived ornithomimid and form a monophyly with North American ornithomimids (Struthiomimus altus and Ornithomimus edmontonicus), sharing two characters (straight pubic shaft and large acute angle between pubic shaft and boot). Some characters (small anterior process of the pubic boot and curved pedal unguals) are seen in basal ornithomimosaurs as well, but these features in Q. henanensis are reversal. Qiupalong is the first definitive ornithomimid from outside of the Gobi Desert and is the southern-most occurrence of Late Cretaceous ornithomimid from eastern Asia, demonstrating southern extension of ornithomimid distribution in Asia.
Centrosaurine ceratopsians are characterized by well developed nasal horncores or bosses, relatively abbreviated supraorbital horncores or bosses, and adorned parietosquamosal frills. Recent study of several paucispecific (low diversity) bonebed assemblages in Alberta and Montana has contributed greatly to our understanding of ontogenetic and taxonomic variation in the skulls of centrosaurines. Relative age determination of centrosaurines is now possible through examination of ontogenetic change in several characters, including the surface bone morphology of specific skeletal elements. The within-group taxonomy of centrosaurines is based almost entirely on characters of the skull roof, relating particularly to horns and frills. Juvenile and sub-adult centrosaurines are characterized by relatively simple, unadorned skulls compared to their adult counterparts. As in numerous living taxa, the cranial ornaments of centrosaurines developed late in ontogeny, as individuals approached or attained adult size. An important implication arising directly from this study is that juvenile and sub-adult centrosaurines are difficult to distinguish taxonomically at the specific level. Two monospecific genera represented only by immature materials,Brachyceratops montanensisandMonoclonius crassus, cannot be defended and should be considerednomina dubia. The late ontogenetic development and diverse taxonomic variation of horn and frill morphologies support the contention that these structures are best interpreted as reproductive characters employed in mate competition.
Many tyrannosaurid skeletons have been collected in Canada, the United States, and Mongolia. These fossils tend to represent mature individuals, but juveniles are also known. Skeletons of five genera of tyrannosaurids representing two distinct clades (albertosaurines and tyrannosaurines) were measured, and bivariate analysis was done on 85 dimensions. Allometric differences among mature specimens of different species are shown to be trivial when compared with the allometric differences associated with growth. Nevertheless, albertosaurines tend to be more lightly built than tyrannosaurines. When compared with a tyrannosaurine of the same absolute size, albertosaurines had slightly shorter, lower skulls, shorter ilia, longer tibiae, longer metatarsals, and longer toes. The arms of albertosaurines and tyrannosaurines are the same size, with the exception of Tarbosaurus, which has shorter front limb elements. Tooth counts show individual and interspecific variation, but there is no evidence that tooth numbers are controlled by the size or age of an animal. Dinotyrannus, Jenghizkhan, Maleevosaurus, Shanshanosaurus, Stygivenator, and possibly Nanotyrannus have proportions that suggest they are ontogenetic stages of either Tarbosaurus or Tyrannosaurus.
Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn basin area, Wyoming and Montana
- J H Ostrom
Ostrom, J. H. 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn basin area, Wyoming
and Montana. Bulletin of the Peabody Museum of Natural History
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Late Paleozoic and Mesozoic Ecosystems in SE Asia
- G Cuny
- J Le Loeuff
- V Suteethorn
, G. Cuny, J. Le Loeuff, and V. Suteethorn (eds.), Late
Paleozoic and Mesozoic Ecosystems in SE Asia. Geological Society
of London, London.
- R M Sullivan
Sullivan, R. M. 1997. A juvenile Ornithomimus antiquus (Dinosauria:
Theropoda: Ornithomimosauria) from the Upper Cretaceous Kirtland Formation (De-Na-Zin Member), San Juan Basin, New Mexico; pp. 249-254 in O. Anderson, B. Kues, and S. Lucas (eds.),
Mesozoic Geology and Paleontology of the Four Corners Area.
New Mexico Geological Society Guidebook, 48th Field Conference.
New Mexico Geological Society, Socorro, New Mexico.
Variation in the Late Jurassic theropod dinosaur Allosaurus: ontogenetic, functional, and taxonomic implications
- M A Loewen
Loewen, M. A. 2009. Variation in the Late Jurassic theropod dinosaur Allosaurus: ontogenetic, functional, and taxonomic implications. Ph.D. dissertation, University of Utah, Salt Lake City,
Utah, 326 pp.
Classification of the Dinosauria. The American Journal of
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