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A new, large ornithomimid from the Cretaceous Dinosaur Park Formation of Alberta, Canada: Implications for the study of dissociated dinosaur remains
Abstract
Only two ornithomimid genera, Ornithomimus and Struthiomimus, are currently known from the Upper Cretaceous of North America. However, a number of ornithomimid elements from Alberta’s Dinosaur Park Formation (Upper Campanian), cannot be assigned to either Ornithomimus or Struthiomimus. These bones, including a frontal, caudal vertebrae, and unguals of the manus and the pes, come from animals significantly larger than any previously known Judithian ornithomimid. The frontal exhibits several unusual features, including transverse expansion over the prefrontals, and extreme reduction of the supratemporal fossae. Caudal vertebrae are characterized by neural arches that are posteriorly shifted and transversely expanded. Manual unguals possess a highly concave articular surface, a flexor tubercle divided by a sulcus, and a broad claw. Pedal unguals display highly concave articular surfaces, and a ridge-like flexor tubercle dividing a deep ventral fossa. Although it is difficult to know whether these elements represent a single taxon, this is currently the most parsimonious hypothesis. This study demonstrates how isolated dinosaur bones can extend our knowledge of dinosaur faunas.
... They have a depression along the posterior part of the neural arch that receives the prezygapophysis of the successive vertebra (Fig. 7D). Similar facets for the prezygapophyses of the following vertebra were described for the posterior caudals of the Dinosaur Park Formation ornithomimid (Longrich, 2008). A low neural spine is placed anteriorly within the depression bordered by the prezygapophyses but on a flat part of the neural arch posteriorly, in contrast with the condition in Struthiomimus and the Dinosaur Park Formation ornithomimid, where it is placed in a longitudinal sulcus (Longrich, 2008). ...
... Similar facets for the prezygapophyses of the following vertebra were described for the posterior caudals of the Dinosaur Park Formation ornithomimid (Longrich, 2008). A low neural spine is placed anteriorly within the depression bordered by the prezygapophyses but on a flat part of the neural arch posteriorly, in contrast with the condition in Struthiomimus and the Dinosaur Park Formation ornithomimid, where it is placed in a longitudinal sulcus (Longrich, 2008). Manual Ungual Phalanges-The ornithomimid manual unguals can be readily identified by a poorly developed flexor tubercle, which is displaced distally from the proximal articular surface (Makovicky et al., 2004). ...
... Manual Ungual Phalanges-The ornithomimid manual unguals can be readily identified by a poorly developed flexor tubercle, which is displaced distally from the proximal articular surface (Makovicky et al., 2004). One ungual (ZIN PH 194/16) has a transverse sulcus on its flexor tubercle, as in the Dinosaur Park Formation ornithomimid (Longrich, 2008). The presence of this groove is a rare individual variation in Dzharacursor. ...
... This is known, in part, based on ornithomimosaur remains from the Cloverly Formation [119] and Arundel Clay [15], H. okladnikovi from Mongolia [120] (all small to medium-bodied species), as well as the earliest examples of large bodied species with some taxa, such as A. fridayi in North America [14] and B. grandis in Asia [69], exceeding 350 kg [37] (S1 Table). By the end of the Cretaceous (Campanian-Maastrichtian), multiple large-bodied species are known to have inhabited Laurasian landmasses, including the deinocheirid Paraxenisaurus normalensis, from the Campanian Cerro del Pueblo Formation of Mexico, indeterminate large-bodied ornithomimid materials from the Dinosaur Park Formation, Canada [25,27,114,121,122] and G. bullatus (MPC-D 100/11) from the Nemegt Formation of Mongolia [77]. Moreover, by this time ornithomimosaurs had achieved gigantism, as exemplified by D. mirificus (MPC-D 100/127), which is estimated to have weighed over 6,000 kg [113] (S1 Table). ...
... However, co-occurrences of both small/medium and large-bodied ornithomimosaur genera are rare. Few examples include the Late Cretaceous Nemegt Formation (early Maastrichtian) of Mongolia, which preserves the medium-bodied taxa Anserimimus planinychus and G. bullatus and large-bodied taxon D. mirificus [113,128,129], and the Dinosaur Park Formation (mid to late Campanian) of Canada, including the medium-bodied taxa O. edmontonicus, R. evadens, and S. altus, and potentially also an unnamed large ornithomimosaur [73,122]. ...
... Previous studies on the dissociated ornithomimosaur specimens have demonstrated that manual and/or pedal elements of ornithomimosaurs are an important source of taxonomically informative anatomical information and can be diagnostic for Ornithomimosauria [30,68,122]. This is supported by several studies describing ornithomimosaurians on the basis of solely manual or pedal elements, for example, A. tugrikinensis, A. planinychus, A. fridayi, P. normalensis, and T. packardensis [14,62,114,130,131]. ...
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 Deinocheirus 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 co-existence 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 multiple cohabiting species of ornithomimosaurian dinosaurs in Late Cretaceous ecosystems of Laurasia.
... comm. To C.-G. Yun, 2020); (2) the most richly fossiliferous exposures along the Red Deer River valley belong to the Dinosaur Park Formation (Sullivan, 2003); and (3) the Dinosaur Park Formation is much more extensively exposed and excavated than the Oldman Formation (Longrich, 2008(Longrich, , 2010. In this case, "Drumheller" is most likely an error or a very vague localization written on the record of origin for this specimen, as there are no exposures of the Dinosaur Park or the Oldman formations in this area. ...
... Assuming that the previous argumentation placing the origin of GMNH-PV 435 into the Dinosaur Park Formation is correct, a brief geological overview of the formation is presented here. The Dinosaur Park Formation is about 75 m thick, and its fluvial and floodplain sediments were derived from the erosion of mountain ranges lying to the west, and deposited during the Campanian stage, between 76.9 and 75.8 Ma (Longrich, 2008;Fowler, 2017;Yun, 2020b). Therefore, the Dinosaur Park Formation is middle-late Campanian in age. ...
... The paleoenvironment for the lower part of the Dinosaur Park Formation is interpreted as an alluvial plain dominated by winding river systems, while the upper part is considered as being formed in coastal settings (Eberth, 2005). The Dinosaur Park Formation is famous for its rich assemblage of vertebrates, including freshwater chondrichthyans and osteichthyans, mammals, plesiosaurs, turtles, squamates, crocodylians, pterosaurs,and dinosaurs including birds (e.g., Longrich, 2008;Yun, 2020b;Campbell et al., 2021). The high diversity of ectothermic taxa in the formation suggests the climate was warm for the largest part of the year, while the presence of coals and the absence of caliches in the Dinosaur Park Formation imply a high amount of annual rainfall with very rare periods of drought (Eberth, 2005;Longrich, 2010). ...
A well preserved, but isolated metatarsal III of a tyrannosaurid dinosaur, originating probably from the Dinosaur Park Formation of Alberta, Canada, is tentatively referred to Daspletosaurus torosus. The size of the specimen suggests that it likely comes from a large juvenile, since the width of the distal end is about 63 % of that of a much larger individual. The morphology of the specimen supports the recently suggested hypotheses that apomorphies of tyrannosaurid taxa may have developed at young growth stages, and that juveniles of albertosaurines and tyrannosaurines may be easier to distinguish from one another than previously thought. Additionally, the specimen reported here is important in that it provides an addition to the very poor juvenile fossil record of Daspletosaurus.
... Paraxenisaurus normalensis is referred to Ornithomimosauria based on the combination of the following characteristics: (1) an expanded medial surface of the distal end of metatarsal III (Choiniere et al., 2012); (2) a dorsoventrally thicker shaft of metatarsal IV (Choiniere et al., 2012); (3) the presence of a small flexor tubercle in the manual ungual which has a distal placement (Osmólska and Roniewicz, 1970;Sues and Averianov, 2016); (4) a well-developed, broad groove on the extensor surface of distal femur (Sues and Averianov, 2016); (5) shallow extensor ligament pits on the dorsal surface of phalanges of pedal digit IV and extensor ridges that are not sharp (Sues and Averianov, 2016); (6) pedal unguals with a triangular cross-section and relative straight ventromedial and ventrolateral edges; and (7) pedal unguals with a pronounced ventral fossa located on the ventral surface of the proximal end, surrounding a well-developed ridge-like flexor tubercle (Longrich, 2008;Choiniere et al., 2012;Sues and Averianov, 2016). ...
... The length of the caudal vertebrae centra from Paraxenisaurus normalensis is much longer than in the vast majority of previously described ornithomimosaur centra from the Cretaceous of North America and other parts of the world (see Table 1). At the moment, these axial elements are only comparable in size with the caudal vertebrae of the North American specimen TMP 1993.36.155 from the Dinosaur Park Formation in Canada (Longrich, 2008) and the Asian species Beishanlong grandis (FRDC-GS GJ (06) 01-18; Makovicky et al., 2010) and Gallimimus bullatus (DPS 100/11; Osmólska et al., 1972). However, the caudal vertebrae of P. normalensis are different from those aforementioned specimens in several aspects; P. normalensis possesses a shallow sulcus that runs along the ventral surface of the centrum in both anterior and posterior caudals, while in G. bullatus this shallow sulcus is only present in the most posterior caudals behind the transition point (see Osmólska et al., 1972). ...
... However, the caudal vertebrae of P. normalensis are different from those aforementioned specimens in several aspects; P. normalensis possesses a shallow sulcus that runs along the ventral surface of the centrum in both anterior and posterior caudals, while in G. bullatus this shallow sulcus is only present in the most posterior caudals behind the transition point (see Osmólska et al., 1972). In contrast, the posterior caudal vertebrae of the Dinosaur Park specimen (TMP 1993.36.155) possess a broad, deep groove that runs along the ventral surface (Longrich, 2008). Finally, B. grandis caudal vertebrae instead of having a ventral sulcus, they possess a midline keel (Makovicky et al., 2010), which has also been reported in the Asian ornithomimosaur Harpymimus okladnikovi (see Makovicky et al., 2010). ...
New ornithomimosaur material discovered from the Upper Cretaceous Cerro del Pueblo Formation of Coahuila, Mexico is described herein. The material includes postcraneal elements from several individuals, which are assigned to a new genus and species, Paraxenisaurus normalensis. This new taxon is characterized by the presence of a strongly curved and laterally compressed manual ungual I with a distally placed flexor tubercle divided by a deep sulcus and a deeply concave proximal, elliptical-shaped articular surface; a metacarpal III that has an expanded proximal articular end, which is similar in width to metacarpal II; a combination of posterior caudal vertebrae, where the most anterior vertebrae possess low dorsoventral prezygapophyses with nearly vertical articulation surfaces, while the most posterior vertebrae have prezygapophyses that face ventromedially; a non-arctometatarsalian pes, where the proximal end of metatarsal III is expanded and has a proximal ovoid outline; the presence of an attachment site for pedal digit I in the posterior surface of the distal quarter of metatarsal II; an expanded medial condyle of metatarsal II; a transversely wide distal end of metatarsal III, which has a semi-ginglymoid articular surface; distinctively broad and ventrally curved pedal unguals that depending on the digit, the proximodorsal process changes its position adopting a lip-shaped appearance; a rounded, large foramen on the medial side of each pedal ungual and the presence of a deep ventral fossa that surrounds a strongly developed, ridge-like flexor tubercle. This combination of characteristics separate Paraxenisaurus normalensis from other ornithomimosaurs previously described in North America and in other parts of the world. Phylogenetic analysis shows that within Ornithomimosauria, Paraxenisaurus normalensis is recovered as a deinocheirid ornithomimosaur, along with Garudimimus brevipes and Deinocheirus mirificus. Therefore, the finding of Paraxenisaurus normalensis in the Cerro del Pueblo Formation of Coahuila, Mexico represents the first record of the Deinocheiridae family in the Campanian of North America.
... Although nearly straight prezygapophyses are present in several abelisauroids including Elaphrosaurus (Rauhut and Carrano, 2016) and Majungasaurus (O'Connor, 2007), some ceratosaurs have short and arched prezygapophyses ( Fig. 1 A, B) such as in Ceratosaurus (USNM 4735), Viavenator (Filippi et al., 2017) and an indeterminate abelisaurid from Lameta Formation (K27/705, Novas et al., 2004: Fig. 22), resembling the condition present in Afromimus. In addition, as noted by Sereno (2017), the prezygapophyses of the caudal vertebrae of Afromimus are short and curved, which by strongly contrast with the condition present in ornithomimids ( Fig. 1 C), in which the prezygapophyses are enlarged anteroposteriorly, sub-horizontally positioned in lateral view and tongue-shaped (Osmolska et al., 1972;Longrich, 2008). 2) Sereno (2017) noted the presence of rugosities along the prezygapophyses of the middle and distal caudals as an autapomorphy of Afromimus. ...
... Therefore, the presence of this trait on caudal vertebrae of ornithomimosaurs may be convergently acquired (Fig. 1D, F). 4) Sereno (2017) also supported the ornithomimosaurian affinities of Afromimus based on the morphology of the caudal vertebral postzygapophyses. He noted that the postzygapophyses of the middle and distal caudal vertebrae are lodged within a rimmed fossa between the prezygapophyses that interlocks adjacent vertebrae (Fig. 2), a condition present in Sinornithomimus and more advanced ornithomimids (Longrich, 2008). Nevertheless, the presence of a rimmed fossa between prezygapophyses is also present in abelisauroids such as Masiakasaurus , Majungasaurus (Carrano, 2007), "Coeluroides" and several indeterminate abelisauroids from India (Novas et al., 2004). ...
... In this way, the morphology of the pedal unguals of Afromimus neither sustains nor refutes the abelisauroid or ornithomimoid affinities of this genus (Fig. 7). It is worthy to mention that many ornithomimosaurs only show the ventral vascular groove (Longrich, 2008;Makovicky et al., 2004). ...
... The ventral embayment, which is shallower than the dorsal embayment, is absent in more posterior caudal vertebrae Masiakasaurus , Elaphrosaurus (Rauhut and Carrano, 2016), Deltadromeus (Sereno et al., 1996), alvarezsauroids (Novas, 1997), and therizinosaurids (Zanno, 2010 (Longrich, 2008). ...
... other Late Cretaceous ornithomimosaurs (Longrich, 2008). ...
... The same paired, rimmed depressions are present in CA ?24, although shallower in depth (Fig. 2.2). The postzygapophyses of mid caudal vertebrae, thus, are lodged within a rimmed fossa that interlocks adjacent vertebrae, a condition present in Sinornithomimus and more advanced ornithomimids(Longrich, 2008).The postzygapophyses are relatively short, extending only a short distance beyond the posterior centrum face in CA ?16 (Fig. 1.1). In CA ?26 and CA ?27, the postzygapophyses probably do not extend beyond the posterior centrum face(Fig. ...
A new genus and species of ornithomimosaur, Afromimus tenerensis, is described based on a fragmentary skeleton from the Lower Cretaceous (Aptian—Albian) El Rhaz Formation of Niger. The holotype and only known individual preserves caudal vertebrae, chevrons and portions of the right hind limb. Derived ornithomimosaurian features include the broad, peanut-shaped articular surfaces of mid caudal centra, parasagittal fossae on mid caudal centra for reception of the postzygapophyses of the preceding vertebra, and a raised, subtriangular platform on the ventral aspect of the pedal phalanges. New information is given for, and comparisons made to, Nqwebasaurus thwazi from southern Africa, the oldest and most basal ornithomimosaur. Unlike other coelurosaurian clades that have expansive radiations on northern landmasses, the oldest ornithomimosaur and now another basal form are known from a southern landmass, Africa.
... This material includes a partial postcranial skeleton (CMN 8902) with the diagnostic character combination of a distally straight pubic shaft and a short anterior extension of the pubic boot, and an isolated astragalocalcaneum (UALVP 53595) with the autapomorphic condition of a pit between the astragalus and calcaneum. We also describe an isolated pedal ungual (UALVP 52861) as nearly identical to the corresponding element in Q. henanensis and distinct from previously described curved ornithomimid pedal unguals from Alberta (Longrich 2008). Ornithomimids are among the most common theropods collected in Alberta (Currie and Koppelhus 2015), with a potentially high taxonomic diversity represented. ...
... Ornithomimids are among the most common theropods collected in Alberta (Currie and Koppelhus 2015), with a potentially high taxonomic diversity represented. Ornithomimid species previously reported from the Belly River Group in Alberta include Struthiomimus altus (Lambe 1902), Dromiceiomimus samueli (Parks 1928), Ornithomimus edmontonicus (Russell 1972), Rativates evadens (McFeeters et al. 2016), and an unnamed large-bodied ornithomimid (Longrich 2008). However, Makovicky et al. (2004) suggested that D. samueli and O. edmontonicus are synonymous, and Longrich (2008) opted to subsume both under "Ornithomimus sp." when referring to the material from the Belly River Group. ...
... The width of the proximal caudal vertebrae is similarly greater than half of the centrum length in G. bullatus (Osmólska et al. 1972, table 2), suggesting that this character state may be plesiomorphic for derived ornithomimids and not an autapomorphy of S. altus. The character of a robust forelimb is retained in some modern diagnoses of Struthiomimus (Longrich 2008), and we cannot recognize any significant anatomical differences between the incomplete forelimbs of CMN 8902 and S. altus (UCMZ 1980.1). However, a robust humerus is also known in the Asian ornithomimid Anserimimus planinychus (Kobayashi and Barsbold 2006, fig. ...
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 ornithomimid 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.
... These pedal unguals (Figs. 3A-3J and 4A-4O) share the presence of a flexor fossa on the ventral surface of each pedal ungual, the presence of relatively straight ventromedial edges on each of the unguals, and the presence of ventrolateral and ventromedial edges developed into keels, all diagnostic of ornithomimosaurs (Barsbold & Osmólska, 1990;Longrich, 2008;Makovicky et al., 2009;Xu et al., 2011;Choiniere, Forster & de Klerk, 2012;Lee et al., 2014). Though Choiniere, Forster & de Klerk (2012) noted that flattened pedal unguals and the presence of a flexor fossa on the ventral face of each pedal ungual were not exclusive traits to ornithomimosaurs, the two traits are mutually exclusive of other taxa. ...
... Previous studies on ornithomimosaur remains have affirmed that individual postcranial elements assignable to Dinosauria can be assigned to family level and genus level (Currie, 1987;Longrich, 2008). Notably, Longrich (2008) and Shapiro et al. (2003) demonstrated that manual and pedal material can be diagnostic for Ornithomimosauria. ...
... Previous studies on ornithomimosaur remains have affirmed that individual postcranial elements assignable to Dinosauria can be assigned to family level and genus level (Currie, 1987;Longrich, 2008). Notably, Longrich (2008) and Shapiro et al. (2003) demonstrated that manual and pedal material can be diagnostic for Ornithomimosauria. ...
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.
... Marsh (1890) established the Ornithomimidae and the type species of Ornithomimus, O. velox, based on fragmentary material from the upper Maastrichtian Denver Formation of Colorado, U.S.A. The presence of ornithomimids in the Campanian Belly River Group of Alberta, Canada, has been recognized for over a century (Lambe, 1902), but their taxonomic diversity in these units is still not fully understood (Longrich, 2008). Makovicky et al. (2004) recognized only two valid ornithomimid species from the Belly River Group, Struthiomimus altus (Lambe, 1902) and Ornithomimus edmontonicus (Sternberg, 1933). ...
... Diagnosis-Rativates evadens is diagnosed by the following autapomorphies: (1) Maxilla with the contact for the jugal short and blunt rather than long and tapered; (2) mid-caudal neural spines mound-like and anteroposteriorly reduced in the region of the transition point of the tail; (3) posterior contact of ischial shafts convex and completely fused; and (4) distal end of the third metatarsal without a concavity on the flexor surface, and with a straight flexor edge in distal view. In addition to these characters, Rativates evadens is further distinguished from the penecontemporaneous Struthiomimus altus by (a) the long antilium reaching approximately as far cranially as the distal end of the pubic shaft (excluding the boot), and (b) the comparatively straight medial edge of the third metatarsal in anterior view; from Ornithomimus sp. by the proportionately anteroposteriorly shorter antorbital fossa (unknown in the Dinosaur Park Formation material of S. altus); and from the unnamed large ornithomimid (Longrich, 2008) by (a) a relatively small adult body size, and (b) straight pedal unguals that lack the strongly angled articular facet, large proximodorsal process, and prominent flexor tubercle of that taxon. ...
... The ungual spurs (sensu Osm olska et al., 1972:134) are positioned proportionately more distally on ungual III. The ventrolateral edges of the unguals are relatively sharp, in contrast to the more rounded ventrolateral edges exemplified by CMN 930 (Longrich, 2008; but see also Cullen et al., 2013). Ventrally, the portion of the ungual proximal to the spurs on unguals II and IV (not preserved on ungual III) is approximately parallel-sided, as in Struthiomimus (CMN 930), rather than markedly widest proximally as in Ornithomimus (CMN 8632, ROM 797). ...
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
... An updated dinosaurian faunal list for the DPF was compiled from multiple sources Ryan and Evans, 2005;Longrich, 2008Longrich, , 2009Eberth and Evans, 2011;Ryan et al., 2012). Attempts have been made to survey the literature as thoroughly as possible and to use the most current taxonomy. ...
... This point marks the smallest taxon that exceeds 50% completeness, in this case 100% complete (Ornithomimus edmontonicus), and as such marks the point where the smallest nearly complete taxa are found. The second division occurs at a less precise location between the 29th and 32nd taxa (inclusive of: Unescoceratops koppelhusae (Ryan et al., 2012), the large unnamed ornithomimid (Longrich, 2008), Edmontonia rugosidens and Panoplosaurus mirus) at an estimated mass between 160 and 1600 kg. Although the sliding window mean difference method is ambiguous as to the precise location of this division, the middle of this range (between the large unnamed ornithomimid and Edmontonia rugosidens) is characterised by both the most massive relatively incomplete taxon (all larger taxa are more than 41% complete), and a distinct jump in size from 370 kg to 1400 kg. ...
... This also suggests that small-bodied taxa are under-sampled and, with future collections there should be more discoveries of new taxa, the majority of which will be small-bodied. In order to get a more complete understanding of the true DPF fauna there needs to be a concentration of worker effort towards the identification of small-bodied taxa (Longrich, 2008). This task is understandably difficult since, as we have demonstrated here, these taxa are not likely to be represented by complete or articulated specimens. ...
... The best preserved vertebra (DePalma et al., fig. 5) is dromaeosaur-like in the elongation of the prezygapophyses, yet they differ from those of dromaeosaurids in having much deeper and more posteriorly extended bases, recalling ornithomimids (e.g., Longrich, 2008). Most forelimb elements lack the majority of the articular ends (e.g, DePalma et al., 2015, figs 2 and 3) which are the most phylogenetically-informative parts of the theropod long bones. ...
... 12), the large falciform ungual referred to the second toe lacks the asymmetric placement of the collateral grooves (contra DePalma et al., 2015) diagnostic of dromaeosaurids. The flattened pedal ungual 3 with reduced flexor tuber is unusual for a dromaeosaurid and more closely recalls the ornithomimosaurs (e.g., Longrich, 2008). Since the type material of Dakotaraptor is currently housed in a private collection (DePalma et al., 2015), it is unclear if it is available for further examination. ...
Known since the 19 th Century, the compsognathids are among the smallest predatory dinosaurs, and include the first feathered non-avian species found. Traditionally, compsognathids have been considered small and unspecialized coelurosaurs, closer to birds than large-bodied forms like allosauroids and megalosaurids. Yet, all known compsognathids are based on skeletally-immature specimens, and this challenges the accuracy of their traditional phyletic placement. Despite the role of heterochrony in dinosaur evolution is widely recognized, the impact of ontogenetic-biased miscodings in shaping theropod phylogenetics is mostly underestimated. Herein, I show that the standard framework of theropod macroevolution is biased by a series of coding artifacts which violate semaphoront equality prescribed by phylogenetic systematics. I introduce "Ontogenetic State Partitioning" (OSP), a novel coding protocol which integrates ontogenetic and morphological variation under a total evidence approach, and apply it to a densely sampled data set focusing on Mesozoic theropods. The phylogenetic analysis dismissed "Compsognathidae" from being a natural group: its members are identified as juvenile morphs nested among several non-maniraptoriform tetanuran lineages. Conservatism in the immature body plan and greater disparity among large-sized adults differentiate the predatory communities dominated by non-coelurosaurian species (e.g., the so called "triumvirates") from the maniraptoriform-tyrannosaurid faunas (herein named "tyrannies"). This clade-specific differentiation among the communities is confirmed by an analysis of the predatory guild structures including all growth stages: triumvirates and tyrannies result as particular cases along a continuum of communities regulated mainly by alternative contributions of the small-and medium-sized classes. The oldest tyrannies (early Late Cretaceous in age) cluster among non-tyranny communities, supporting the hypothesis that tyrannosaurid-dominated faunas acquired their peculiar structure only after the extinction of the non-coelurosaurian components. The macroevolutionary trajectory that led the maniraptoriforms to realize the avian-like biology may have precluded them from occupying hypercarnivorous large-bodied niches: this bauplan constraint would have favored the tyrannosauroids in opportunistically assuming the apex predatory roles in Late Cretaceous Asiamerica but not elsewhere. The large-scale structure of the Cenozoic radiation of birds is coherent with the framework introduced herein.
... The frontal bone in theropod dinosaurs forms the rostral part of the roof of the braincase. Due to its compact nature, it is preserved more frequently than other cranial elements (e.g., Currie, 1987;Longrich, 2008;Jasinski, 2015;Averianov, 2016). Currie (1987) noted that the frontal bone of theropods is diagnostic at the specific level, and subsequent publications have followed this assertion that frontals are one of the most taxonomically useful elements in the entire theropod skull (Longrich, 2008;Jasinski, 2015;Averianov, 2016;Evans et al., 2017). ...
... Due to its compact nature, it is preserved more frequently than other cranial elements (e.g., Currie, 1987;Longrich, 2008;Jasinski, 2015;Averianov, 2016). Currie (1987) noted that the frontal bone of theropods is diagnostic at the specific level, and subsequent publications have followed this assertion that frontals are one of the most taxonomically useful elements in the entire theropod skull (Longrich, 2008;Jasinski, 2015;Averianov, 2016;Evans et al., 2017). Tyrannosaurid theropods, a group of gigantic carnivorous dinosaurs that are characterized by large robust skulls with incrassate teeth, short forelimbs with only two functional digits, and elongate hindlimbs with arctometatarsalian pedes (Holtz, 2004;Brusatte et al., 2010;Brusatte & Carr, 2016), are no exception for this. ...
A right frontal bone belonging to the tyrannosaurid theropod Teratophoneus curriei from the Campanian Kaiparowits Formation of Utah provides important anatomical information that is useful in understanding tyrannosaurid taxonomy and relationships. Many aspects of its anatomy indicate a subadult ontogenetic status of this individual, as they compare favorably with subadults of other tyrannosaurids such as Daspletosaurus torosus and Tyrannosaurus rex. This is consistent with the previous interpretation that this individual was subadult, based on different cranial bones such as lacrimal or maxilla. It is likely that a previous assessment of the body mass of this individual was underestimated, and it is presumed here that it was most likely around 1000 kg. This description of the frontal anatomy has several implications for previous works on tyrannosaurid cranial anatomy, and information that corrects aspects of our understanding on tyrannosaurid frontal anatomy is provided. Reanalysis of Nanuqsaurus hoglundi, a tyrannosaurid theropod that has similar frontal morphology with Teratophoneus curriei, implies that parts of its diagnosis are problematic and the proposed evidence for the supposed diminutive body size of this taxon is weak.
... Among ornithomimids, new discoveries and re-assessments of previously collected specimens have led to the recognition of a smaller-bodied taxon, Rativates evadens (McFeeters et al. 2016), distinct from the previously recognized DPF ornithomimids Struthiomimus altus and Ornithomimus edmontonicus (in the latter case, following 's suggested synonymization of Dromiceiomimus samueli with O. edmontonicus). Additionally, the presence of a currently unnamed large-bodied taxon (Longrich 2008) was hypothesized based on isolated caudal vertebrae, a frontal, and unguals, although the degree to which at least the morphology of the latter represents autapomorphic characters as opposed to individual, positional, or intraspecific variation has been questioned (Cullen et al. 2013;McFeeters et al. 2018aMcFeeters et al. , 2018b. Lastly, a partial skeleton and several isolated elements were recently re-examined and hypothesized to represent evidence of the Asian taxon Qiupalong in the DPF . ...
... This last specimen includes a complete skull, which allowed the determination that the tooth taxon "Zapsalis abradens" actually represents the premaxillary teeth of Saurornitholestes langstoni (Currie and Evans 2020). Additionally, a microraptorine dromaeosaurid, Hesperonychus elizabethae, is known from the fragmentary remains of a pelvic girdle and various referred pedal phalanges and is notable in being the smallest known theropod from the DPF (Longrich and Currie 2009). ...
The Dinosaur Park Formation (DPF) of Alberta, Canada, has produced one of the most diverse dinosaur faunas, with the record favouring large-bodied taxa, in terms of number and completeness of skeletons. Although small theropods are well documented in the assemblage, taxonomic assessments are frequently based on isolated, fragmentary skeletal elements. Here we reassess DPF theropod biodiversity using morphological comparisons, high-resolution biostratigraphy, and morphometric analyses, with a focus on specimens/taxa originally described from isolated material. In addition to clarifying taxic diversity, we test whether DPF theropods preserve faunal zonation/turnover patterns similar to those previously documented for megaherbivores. Frontal bones referred to a therizinosaur (cf. Erlikosaurus), representing among the only skeletal record of the group from the Campanian–Maastrichtian (83–66 Ma) fossil record of North America, plot most closely to troodontids in morphospace, distinct from non-DPF therizinosaurs, a placement supported by a suite of troodontid anatomical frontal characters. Postcranial material referred to cf. Erlikosaurus in North America is also reviewed and found most similar in morphology to caenagnathids, rather than therizinosaurs. Among troodontids, we document considerable morphospace and biostratigraphic overlap between Stenonychosaurus and the recently described Latenivenatrix, as well as a variable distribution of putatively autapomorphic characters, calling the validity of the latter taxon into question. Biostratigraphically, there are no broad-scale patterns of faunal zonation similar to those previously documented in ornithischians from the DPF, with many theropods ranging throughout much of the formation and overlapping extensively, possibly reflecting a lack of sensitivity to environmental changes, or other cryptic ecological or evolutionary factors.
... Hunt and Quinn (2018) noted positional variation in the incompletely preserved pedal unguals of the basal ornithomimosaur Arkansaurus fridayi, but were unable to assign each ungual to a digit. Longrich (2008) described some isolated ornithomimosaur unguals, but did not assign them to a particular digit. Cullen et al. (2013) described variation in associated ornithomimid unguals with reference to inferred position, and found some of the taxonomic characters used by Longrich (2008) to be problematic; however, the unguals described by Cullen et al. (2013) were not figured exhaustively, and no rationale for their positional identification was given. ...
... Longrich (2008) described some isolated ornithomimosaur unguals, but did not assign them to a particular digit. Cullen et al. (2013) described variation in associated ornithomimid unguals with reference to inferred position, and found some of the taxonomic characters used by Longrich (2008) to be problematic; however, the unguals described by Cullen et al. (2013) were not figured exhaustively, and no rationale for their positional identification was given. ...
Positional variation is documented in ornithomimid pedal unguals from the Dinosaur Park and Horseshoe Canyon Formations of Alberta, Canada, and characters for identifying the position of isolated ornithomimid pedal unguals are discussed. Ungual morphology has been used recently to argue for the coexistence of two distinct ornithomimosaurs, a basal taxon and distinctly more derived taxon, in the Early Cretaceous Arundel Clay of Maryland, USA. However, these conclusions are based on misconceptions of the morphology and positional variability of ornithomimosaur unguals. Some characters previously cited as diagnostic of ornithomimosaur unguals are not actually observed in this clade, or are more homoplastically distributed among theropods. Other characters proposed to distinguish between the two pedal ungual morphs in the Arundel Clay material are shown in the Albertan ornithomimid material to consistently distinguish the different ungual positions within the pes of one individual. Claims of multiple distinct ornithomimosaur taxa in the Arundel Clay are premature, as the two pedal ungual morphotypes more likely represent positional variation in a single taxon.
... The dorsal surface is dominated by a broad, parasagitally oriented groove that extends from the posterior end of the nasal suture towards the supratemporal ridge. This groove is often cited as a distinctive characteristic of troodontids Evans et al. 2014), and contrasts with the flat condition seen in adult dromaeosaurids and ornithomimids (Currie 1987b;Longrich 2008a), and the weakly concave frontals of therizinosaurs (Averianov 2016;Averianov and Sues 2016). Laterally, this groove defines a strongly upturned orbital rim. ...
... to the anterior end of the globular cerebral fossa, which loosely mimics the triangular form of the frontal as a whole. The olfactory bulb fossa and tract are long and large compared with the much shorter olfactory region in dromaeosaurids and ornithomimids, but compare readily to troodontids (Russell 1969;Sues 1978;Currie 1987b;Longrich 2008a;Evans et al. 2014). The lacrimal contact extends onto the ventral surface of the frontal, where it is expressed as a tall, transversely oriented buttress at the anterior end of the crista cranii, as is characteristic of troodontids (Evans et al. 2014). ...
Troodontid material from the Maastrichtian of North America is extremely rare, beyond isolated teeth from microvertebrate sites. Here we describe troodontid frontals from the early Maastrichtian Horseshoe Canyon Formation (Horsethief Member). The most complete specimen, TMP 1993.105.0001, is notably foreshortened and robust when compared with numerous specimens referred to Troodon from the Dinosaur Park Formation, and exhibits several characteristics that distinguish it from other Late Cretaceous troodontids. Morphometric analyses reinforce shape differences between TMP 1993.105.0001 and other North American troodontids, and show that proportional differences are independent of size. We therefore erect a new taxon, Albertavenator curriei gen. et sp. nov., which is diagnosed by the following autapomorphies: (1) primary supraciliary foramen is truncated anteriorly by the lacrimal contact; (2) superficial (ectocranial) surface of the frontal proportionally shorter than all known troodontids, with a length to width ratio under 1.3; and (3) frontoparietal contact in which an enlarged lappet of the frontal extends medially to extensively overlap the lateral region of the anteromedial process of the parietal. Interestingly, tooth and jaw morphology from the single relatively complete dentary recovered from the Horseshoe Canyon cannot be distinguished from dentaries and teeth from the Dinosaur Park Formation. If the dentary and teeth from the Horsethief Member of the Horseshoe Canyon Formation prove to belong to A. curriei, extensive overlap in tooth morphology between the Dinosaur Park and Horseshoe Canyon formations reinforces the notion that tooth morphotypes do not exhibit strong correspondence to species alpha diversity, and may encompass multiple closely related taxa.
... Near the top of the formation, mudstones and coals appear, documenting the presence of estuaries and swampy conditions and the transgression of the Bearpaw Sea (Eberth and Brinkman, 1997;Eberth, 2005). The formation contains a diverse assemblage of vertebrates, including fish (Neuman and Brinkman, 2005), amphibians (Gardner, 2005), reptiles (Brinkman, 2005;Caldwell, 2005;Gao and Brinkman, 2005;Wu, 2005), nonavian dinosaurs (Ryan and Evans, 2005;Currie, 2005;Longrich, 2008;Longrich and Currie, 2009), birds (Hope, 2002;Longrich, 2006Longrich, , 2009, and mammals (Fox, 2005;Sankey et al., 2005). The fossil record for large dinosaurs is particularly rich, but isolated teeth and bones show that small vertebrates were diverse and abundant (Brinkman, 1990). ...
... Still, other highly productive, intensively worked formations, such as the Djadokhta, Hell Creek, and Nemegt formations, have failed to produce a comparable number of species (Weishampel et al., 2004). Furthermore, new taxa continue to be recognized, both as a result of ongoing collecting activities, and as a result of the study of previously collected specimens (e.g., Holmes et al., 2001;Longrich, 2008;Longrich and Currie, 2009) such as those described here. This suggests that sampling alone does not account for all of the diversity seen in the Dinosaur Park assemblage. ...
A new genus of long-horned chasmosaurine ceratopsid is described from the Dinosaur Park Formation (upper Campanian) of Western Canada. Mojoceratops perifania is represented by a skull and a parietal from the Dinosaur Park Formation of Alberta and an isolated parietal from the Dinosaur Park Formation of Saskatchewan. Several other specimens are provisionally referred to this taxon. While Mojoceratops shares many plesiomorphies with Chasmosaurus , the animal lacks the forward-curving parietal epoccipitals and reduced postorbital horns that diagnose the genus Chasmosaurus , and it differs from all other chasmosaurines in exhibiting a prominent sulcus on the anterior margin of the parietal, swellings on the anterodorsal surface of the parietal rami, and a small accessory process on the first parietal epoccipital. Other unusual features include anteriorly extended parietal fenestrae, a broad, heart-shaped frill, and transverse expansion of the postfrontal fontanelle. The type material of “ Eoceratops canadensis ” and “ Chasmosaurus kaiseni ” are nondiagnostic and these names are therefore considered nomina dubia, but their morphology is consistent with Mojoceratops and they probably belong to this genus. The frill of Mojoceratops shows marked variation. Some of this variation probably results from intraspecific variation or ontogenetic changes, but because the Dinosaur Park Formation encompasses more than a million years of time, evolution may explain some of these differences. Phylogenetic analysis shows that Mojoceratops forms a clade with Agujaceratops mariscalensis ; Chasmosaurus is the most basal member of Chasmosaurinae.
... According to Xu et al. (2011) and Lee et al. (2014), the profile of the ventral edge is straight in all ornithomimosaurs except Garudimimus brevipes, Deinocheirus mirificus, and Qiupalong henanensis, which have pedal unguals that are ventrally concave in lateral view. Here two characters are confused: the overall curvature of the ventral edge and the angle between the proximal part and distal part beneath the lateral groove (Longrich, 2008). In Deinocheirus mirificus the distal part is perfectly straight but is angled relative to the proximal part (Lee et al., 2014, fig. ...
... 10-12). In the clade of more derived ornithomimids including Sinornithomimus dongi, Gallimimus bullatus, Qiupalong henanensis, Struthiomimus altus, and Ornithomimus edmontonicus, the flexor fossa and flexor tubercle are greatly reduced (Longrich, 2008;Xu et al., 2011;Sues and Averianov, 2016). This derived condition is also present in IZK 1432/2012 (Fig. 5C, D). ...
Parts of the hind limbs of what appears to be a single individual of a theropod dinosaur from the Upper Cretaceous (Santonian–?Campanian) Bostobe Formation of the northeastern Aral Sea region, Kazakhstan, are identified as belonging to an indeterminate ornithomimid based on combination of derived and primitive traits including one ornithomimosaurian synapomorphy (medial side of the anterior surface of the distal end of metatarsal III expanded). This is the first discovery of the associated theropod material from the Bostobe Formation. Ornithomimids were known previously from this formation only from isolated bones. Based on the reduction of the flexor fossa and flexor tubercle on the pedal ungual this material can be referred to the derived ornithomimid clade that includes Sinornithomimus, Gallimimus, Qiupalong, Struthiomimus, and Ornithomimus. The partial femur has a dorsomedially directed head similar to that of an unidentified ornithomimid from the correlative Yalovach Formation of Tajikistan and may belong to the same or a closely related taxon.
... However, lambeosaurins survived into the latest Maastrichtian in New Mexico [88]. Finally, Deinocheiridae is present in the late Campanian of Alberta [89] but disappears afterward [23] while persisting into the latest Campanian in Mexico [25]. ...
The Late Cretaceous of Western North America (Laramidia) supported a diverse dinosaur fauna, with duckbilled dinosaurs (Hadrosauridae) being among the most speciose and abundant members of this assemblage. Historically, collecting and preservational biases have meant that dinosaurs from Mexico and the American Southwest are poorly known compared to those of the northern Great Plains. However, evidence increasingly suggests that distinct species and clades
inhabited southern Laramidia. Here, a new kritosaurin hadrosaurid, represented by the anterior part of a skull, is reported from the late Campanian of the Cerro del Pueblo Formation, ~72.5 Ma, in Coahuila, Mexico. The Cerro del Pueblo Formation kritosaur was originally considered to represent the same species as a saurolophine from the Olmos Formation of Sabinas, but the Sabinas hadrosaur is now considered a distinct taxon. More recently, the Cerro del Pueblo Formation kritosaur has been referred to Kritosaurus navajovius. We show it represents a new species related to Gryposaurus. The new species is distinguished by its large size, the shape of the premaxillary nasal process, the strongly downturned dentary, and massive denticles on the premaxilla’s palatal surface, supporting recognition of a new taxon, Coahuilasaurus lipani. The dinosaur assemblage of the Cerro del Pueblo Formation shows higher diversity than the contemporaneous fauna of the Horseshoe Canyon Formation in Alberta. Furthermore, Kritosaurini, Lambeosaurini, and Parasaurolophini all persist into the latest Campanian in southern Laramidia after disappearing from northern Laramidia. These patterns suggest declining herbivore diversity seen at high latitudes may be a local, rather than global phenomenon, perhaps driven by cooling at high latitudes in the Late Campanian and Maastrichtian.
... Conversely, the expansion of both distal and proximal regions relative to the shaft in dorsal view set TMP2015.007.0015 and the Eutaw Formation specimen (MMNS VP-4949) apart from DMNH EPV.138575. Other anomalously large ornithomimid elements are known from other Cretaceous deposits in North America, including the Dinosaur Park Formation (Longrich, 2008), suggesting the presence of unidentified large-bodied taxa or upper body size limits beyond expectations based on more complete materials. Because no other skeletal elements have been found associated with DMNH EPV.138575, and because some key morphological features are either destroyed or concealed by hematitic overgrowths, we cannot conclusively assign the element to a particular non-avian theropod clade. ...
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.
... Material from the Dinosaur Park Formation has been assigned a different species name, T. inequalis, from the original T. formosus (Currie, 2005). The discovery of Talos, a partial postcranial skeleton from the Campanian Kaiparowits Formation of Utah, provided a chance to reappraise North American troodontid material, which led to the suggestion that Troodon is a nomen dubium and support for the genus Pectinodon (Longrich, 2008;Zanno et al., 2011). The latter, known from teeth and juvenile skeletal material from the Maastrichtian Lance Formation of Wyoming, was originally described as an additional species of Troodon, T. bakkeri (Carpenter, 1982). ...
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single-species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverging oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa, Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens-particularly those preserving soft tissue-remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size.
... Frontals are paired bones that form the anterodorsal part of the braincase. The frontal is considered one of the most taxonomically informative bones among theropods (Currie 1987;Longrich 2008;Averianov 2016). Additionally, due to their compact nature, theropod frontals are better represented in the fossil record than other cranial bones, making them some of the most important skeletal parts for understanding theropod paleobiology (Currie 1987;Averianov 2016). ...
Tarbosaurus bataar is a sister taxon of the well-studied theropod dinosaur Tyrannosaurus rex, and numerous fossils of
this tyrannosaurid have been discovered in the Upper Cretaceous Nemegt Formation of Mongolia. Although specimens
of different sizes of Tarbosaurus bataar have been discovered since its initial description, few rigorous studies on its
growth changes have been done. Here we examine growth changes in the frontal bones of seven Tarbosaurus bataar
specimens using bivariate analyses and the Björk superimposition method to demonstrate trends in their ontogenetic
allometry. The width and depth of the frontal undergoes positive allometry during growth, whereas the length shows a
trend of negative allometry. The details of growth changes in Tarbosaurus bataar frontals are largely similar to those
of Tyrannosaurus rex. Furthermore, generic allometric trends of tyrannosaurid frontals, including those of Tarbosaurus
bataar, are shared with other large-bodied theropod clades and may represent a consequence of strengthening parts of
the braincase as an anchor for the jaw musculature.
... This new discovery increases the known coelurosaurian diversity in the Erlian Formation, and more specifically demonstrates the presence of a second ornithomimosaur distinct from Archaeornithomimus asiaticus in the Iren Nor Region in the Late Cretaceous. Coexistence of multiple ornithomimosaur taxa in a single stratigraphic unit is not uncommon (Longrich, 2008;Sues and Averianov, 2016a). Given that both of the Erlian ornithomimosaurs are relatively poorly known, speculation regarding the palaeobiological factors that permitted them to maintain sympatry without one competitively excluding the other is difficult. ...
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.
... The Tyrants Aisle dinosaur tracksite strata from western Canada. This value was found by Enriquez et al. [35] to be approximately 40 cm based on the largest known, fragmentary ornithomimid pedal unguals recovered from the mid-late Campanian Dinosaur Park Formation in southern Alberta [65], and scaling these with reference to complete ornithomimid pedes [66,67]. Thus, below 45 cm, we acknowledge that there is potentially size overlap between multiple major theropod clades and Thescelosauridae, and refer most of these tracks to indeterminate theropod-like trackmakers. ...
The Wapiti Formation of northwest Alberta and northeast British Columbia, Canada, preserves an Upper Cretaceous terrestrial vertebrate fauna that is latitudinally situated between those documented further north in Alaska and those from southern Alberta and the contiguous U.S.A. Therefore, the Wapiti Formation is important for identifying broad patterns in vertebrate ecology, diversity, and distribution across Laramidia during the latest Cretaceous. Tracksites are especially useful as they provide a range of palaeoecological, palaeoenvironmental, and behavioural data that are complementary to the skeletal record. Here, we describe the Tyrants Aisle locality, the largest in-situ tracksite known from the Wapiti Formation. The site occurs in the lower part of Unit 4 of the formation (~72.5 Ma, upper Campanian), exposed along the southern bank of the Redwillow River. More than 100 tracks are documented across at least three distinct track-bearing layers, which were deposited on an alluvial floodplain. Hadrosaurid tracks are most abundant, and are referable to Hadrosauropodus based on track width exceeding track length, broad digits, and rounded or bilobed heel margins. We suggest the hadrosaurid trackmaker was Edmontosaurus regalis based on stratigraphic context. Tyrannosaurids, probable troodontids, possible ornithomimids, and possible azhdarchid pterosaurs represent minor but notable elements of the ichnofauna, as the latter is unknown from skeletal remains within the Wapiti Formation, and all others are poorly represented. Possible social behaviour is inferred for some of the hadrosaurid and small theropod-like trackmakers based on trackway alignment, suitable spacing and consistent preservation. On a broad taxonomic level (i.e., family or above), ichnofaunal compositions indicate that hadrosaurids were palaeoecologically dominant across Laramidia during the late Campanian within both high-and low-latitude deposits, although the role of depositional environment requires further testing.
... seen in dromaeosaurids, which is formed by a prominent groove separating medial and lateral hemicondyles (e.g., Fowler et al. 2011;Hattori 2016). Derived ornithomimids, which dominated Campanian-Maastrichtian ornithomimosaur faunas in western North America (e.g., Hattori 2016), lacked a hallux with only a few possible exceptions (Longrich 2008;Serrano-Brañas et al. 2020). All known first metatarsals in basal ornithomimosaurs (e.g., Beishanlong, Garudimimus) have a mediolaterally constricted shaft, and a pronounced concavity at the distal end formed by a sulcus separating the two distal hemicondyles, which nonetheless is less well-developed than in the ginglymoid condyles of dromaeosaurids. ...
A well-preserved left theropod metatarsal I from the Campanian Mesaverde Formation of Wyoming is described and identified as belonging to a caenagnathid, representing the first occurrence of this clade from the formation. The specimen is unique in being relatively small, but featuring a suite of characters (triangular shaft, relatively minimal constriction between the shaft and the distal condyle, spherical distal condyle) that are seen in larger-bodied caenagnathids such as Anzu wyliei and “Macrophalangia canadensis”. This suggests that the previously-observed differences in metatarsal I morphology between small and large caenagnathids are not solely the result of allometry, but may represent phylogenetically informative variation. This new specimen lends some support to the hypothesis that “Macrophalangia canadensis” does not repre- sent a large Chirostenotes pergracilis. Furthermore, the specimen is important in establishing the presence of caenagnathids within the Mesaverde Formation fauna, in which theropods are rare.
... A broad and shallow sulcus is present on the ventral surface, and it is laterally delimited by two prominent ridges (Fig. 29E, J). All these features are present in ornithomimosaurs (Osmolska et al. 1972;Longrich 2008) (Fig. 30D). There is no 51 medial buttress to accommodate the ascending process as in many basal tetanurans and ceratosaurs, including Berberosaurus, Masiakasaurus, Majungasaurus and Ceratosaurus. ...
This contribution describes the continental micro- and macrovertebrate fauna of Angeac-
Charente (Berriasian, Early Cretaceous). The rich and diversified fauna includes at least 38
different vertebrate taxa from all major clades, and is represented by more than 50 000
specimens. The Angeac–Charente locality includes the most diverse earliest Cretaceous mixed continental bonebed and Lagerstätte known to date in the World, and it provides a good picture of a Purbeckian paleocommunity. It includes remarkable taxa such as a new ornithomimosaur, a large turiasaur, an helochelydrid turtle and numerous mammals. The vertebrate fauna of Angeac has beyond all a Purberckian character. Many exclusively European genera and species belong to families with an essentially Laurasian paleogeographic distribution. Some taxa nevertheless suggest dispersal events between Africa and Europe at the Jurassic/Cretaceous transition. The successive Charente faunas of Chassiron (Tithonian), Cherves–de–Cognac (Berriasian) and Angeac–Charente improve our poor knowledge of the evolution of continental vertebrate faunas at the Jurassic/Cretaceous transition. Rather than reflecting an important faunal turnover between the Tithonian and the Berriasian, they record environmental changes related to the sea–level regression that characterizes the end of the Jurassic.
... (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. 10), we suggest that theropod footprints ≥45 cm in length described in this paper (i.e., Ty.I.8C and the BADP2019 pes track natural cast) are large enough that they could not have been produced by any Late Cretaceous North American theropod other than a tyrannosaurid. ...
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.
... Given that the sedimentation rates for the upper 22 meters of the Dinosaur Park Formation and Bearpaw Formation transition were slow (Carr et al., 2017), the top of the Dinosaur Park Formation is likely slightly older than 75.46 Ma. The formation is famous for the rich abundance of vertebrate fossils including fishes, amphibians, turtles, squamates, crocodiles, pterosaurs, dinosaurs and mammals (e.g., Currie & Koppelhus, 2005;Longrich, 2008). The Dinosaur Park Formation is partly equivalent in age and partly correlates with the Campanian deposits in Montana such as Judith River Formation (Eberth, 1997). ...
An isolated frontal bone of Daspletosaurus torosus (Theropoda: Tyrannosauridae) is desecribed which was probably found in the Dinosaur Park Formation (Upper Cretaceous) of Dinosaur Provincial Park, Alberta (Canada). It is important in terms of the first detailed osteological description of the frontal of Daspletosaurus torosus. The size and anatomical details of the specimen indicates the frontal belongs to a large subadult individual. This subadult frontal suggests that although ontogeny of Daspletosaurus torosus was generally similar to that of Tyrannosaurus rex, there were some distinct differences. Finally, certain features of this frontal bone indicate that some autapomorphies that have recently suggested for some tyrannosaurid taxa are inadequate due to their broad distribution within a clade.
... Material from the Dinosaur Park Formation has been assigned a different species name, T. inequalis, from the original T. formosus (Currie, 2005). The discovery of Talos, a partial postcranial skeleton from the Campanian Kaiparowits Formation of Utah, provided a chance to reappraise North American troodontid material, which led to the suggestion that Troodon is a nomen dubium and support for the genus Pectinodon (Longrich, 2008;Zanno et al., 2011). The latter, known from teeth and juvenile skeletal material from the Maastrichtian Lance Formation of Wyoming, was originally described as an additional species of Troodon, T. bakkeri (Carpenter, 1982). ...
An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single-species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverging oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa, Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens-particularly those preserving soft tissue-remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size.
... Therefore, the peri-Adriatic carbonate platforms, along with smaller ones recognised in wells, were considered in previous palaeogeographic interpretations as a sort of 'string of pearls' between the Gondwana and Laurasia mainlands (Nicosia et al., 2007). This general framework provided the basis for interpretation of some peculiar aspects of the fauna, defined as endemic dwarf or significantly smaller (Benton et al., 1997;Jianu and Weishampel, 1999;Dalla Vecchia, 2002, 2008, relict (Signore et al., 2001;Evans et al., 2004), endemic (Grigorescu et al., 1999) and depauperate (Benton et al., 1997). These biological properties, according to Nicosia et al. (2007), somehow seemed to confirm the arrangement of isolated platforms proposed in the accepted geodynamic setting. ...
After about thirty years of investigation, the Cretaceous tetrapod track record from Italy has proved to be a 'Rosetta Stone' for improving understanding of the palaeogeographical and palaeoenvironmental evolution of the peri-Adriatic area. In the present contribution, we summarize current knowledge and different interpretations proposed on the basis of twelve ichnosites from northern, central and southern Italy. The tetrapod track record is represented by few ichnosites in the earliest Cretaceous, with the bulk of the record reported from carbonate platform deposits of the Aptian-Cenomanian interval and, in the Late Cretaceous, from a mega-tracksite in Apulia preserving thousands of dinosaur footprints. On the whole, the ichnological diversity documented by the material indicates a high diversity of trackmakers, among which are sauropods, different kinds of theropods, ankylosaurs and hadrosaurs. The persistent occurrence of dinosaur footprints at different stratigraphic levels produced significant questions and constituted a dramatic constraint for the understanding the palaeogeographical and geodynamical evolution of the Mediterranean area during the Mesozoic, suggesting new and different interpretations that challenged previous reconstructions.
... 35 and 36), much like those of Boverisuchus vorax, a pristichampsine eusuchian (e.g., see Fig. 1 of Brochu, 2013) also inferred to be cursorial. Similar hooflike terminal unguals, with flanges running along the lateral surfaces, have been described for the basal ornithischian dinosaurs Zalmoxes (Weishampel et al., 2003), Hypsilophodon (Galton, 1974), and Thescelosaurus (Gilmore, 1915), and to a lesser degree in ornithomimid theropods (e.g., Longrich, 2008;Makovicky et al., 2010), and an allosauroid (White et al., 2013). Gauthier et al. (2011) calculated a body mass for this specimen of Poposaurus as approximately 60-75 kg, and the holotype as 90-100 kg following the methods of Anderson et al. (1985), which falls well within the optimal weight range identified for cursorial mammals (van Damme and Vanhooydonck, 2001). ...
Poposaurus gracilis is a bipedal pseudosuchian archosaur that has been poorly understood since the discovery of the holotype fragmentary partial postcranial skeleton in 1915. Poposaurus. gracilis is a member of Poposauroidea, an unusually morphologically divergent clade of pseudosuchians containing taxa that are bipedal, quadrupedal, toothed, edentulous, and some individuals with elongated thoracic neural spines (i.e., sails). In 2003, a well preserved, fully articulated, and nearly complete postcranial skeleton of P. gracilis was discovered with some fragmentary cranial elements from the Upper Triassic Chinle Formation of Grand Staircase‐Escalante National Monument of southern Utah, USA. The aim of this work is to describe the osteology of this specimen in detail and compare P. gracilis to other closely related pseudosuchian archosaurs. The open neurocentral sutures throughout the majority of the vertebral column, the small size of this individual, and the presence of seven evenly spaced cyclic growth marks in the histologically sectioned femur indicate that this specimen was a skeletally immature juvenile, or subadult when it died. The pes of P. gracilis contains multiple skeletal adaptations and osteological correlates for soft tissue structures that support a hypothesis of digitigrady for this taxon. When coupled with the numerous postcranial characters associated with cursoriality, and the many anatomical traits convergent with theropod dinosaurs, this animal likely occupied a similar ecological niche with contemporaneous theropods during the Late Triassic Period. Anat Rec, 303:874–917, 2020. © 2019 American Association for Anatomy
... The skull could be referred to a higher taxonomic level that encompasses all such materials (such as Neosauropoda or Brachiosauridae), be referred to Brachiosaurus sp. or B. altithorax, or given a new epithet. Longrich (2008) outlined several hypotheses for testing referrals in such a situation, but as noted by Wilson et al. (2009), these hypotheses become less powerful with low sample sizes and individuals of unknown ontogenetic stage (and therefore unknown expected body size). Regardless, some degree of individual research preference and argumentation is unavoidable in such situations. ...
Like many long‐standing dinosaur taxa, Brachiosaurus altithorax from the Upper Jurassic Morrison Formation of North America suffers from taxonomic issues stemming from a relatively incomplete holotype. Lack of anatomical overlap has precluded definitive referral of important specimens, including a mostly complete skull discovered in 1883. We redescribe this skull and some other significant brachiosaurid specimens based on new preparation and computed tomographic (CT) data. We argue that these elements are most parsimoniously referred to B. altithorax. Including these tentatively referred elements in a phylogenetic analysis does not alter the hypothesized relationships of B. altithorax, congruent with the presence of a single brachiosaurid taxon across western North America in the Late Jurassic. Based on CT data, we estimate that B. altithorax had a slower tooth replacement rate than Camarasaurus or the diplodocoids it shared Morrison Formation landscapes with, which suggests a difference in diet and/or feeding strategy. Anat Rec, 303:732–758, 2020. © 2019 Wiley Periodicals, Inc.
... The size of MAPS A1210a (Fig. 1A-F) is consistent with tyrannosauroid affinities for the bone, as is the mediolaterally "pinched" nature of the diaphysis (such that the ratio between the bone's width at its diaphysis and its total length is greater than 3.0), and heavily deepened collateral ligament pits (Lambe 1917;Brochu 2003;Holtz 2004;Brusatte and Carr 2016). Large dromaeosaurids and ornithomimids are also known from the Late Cretaceous of the continent (Longrich 2008;DePalma et al. 2015), but the most massive members of these groups present in North America during that time possess phalanges appreciably smaller than MAPS A1210a. Ornithomimid pedal phalanges are also more gracile than the MAPS phalanx, and dromaeosaurid pedal phalanges are more proximodistally compressed and possess a more heavily arched ventral surface in lateral view than the New Jersey bone (e.g., Osmólska et al. 1972;Makovicky et al. 2004;Norell and Makovicky 2004;Longrich and Currie 2009;Turner et al. 2012;Cullen et al. 2013;McFeeters et al. 2016;Tsogtbaatar et al. 2017). ...
The extinction of the non-avian dinosaurs during the Cretaceous-Paleogene event is one of the most discussed subjects in paleontology. However, the diversity, biogeography, and ecology of this and other clades of terrestrial vertebrates proximal to the extinction are poorly
known. The terrestrial record from this period comes almost exclusively from a relatively small region in western North America. This scarcity of fossil evidence has contributed to a fairly poor understanding of the effects of the extinction on ecosystems on land. Here, I describe three foot bones of large tyrannosauroid theropods collected from marine deposits near the coastal margin of the Cretaceous Atlantic Ocean that add to the notoriously poor dinosaur fossil record from eastern North America. Despite their late Maastrichtian age, these bones retain characteristics that indicate a basal position relative to the coeval Tarbosaurus bataar and Tyrannosaurus rex. The new pedal elements represent the largest known tyrannosauroid dinosaurs from eastern
North America, suggesting multiple lineages of tyrant dinosaur approaching 9 meters persisted into the latest Cretaceous. Emphasizing that non-avian dinosaurs remained a diverse clade until their demise, the new bones provide a rare glimpse at the anatomical and evolutionary diversity of megapredatory theropods during the eve of the Mesozoic.
... One is a partial tibia shaft, the other the distal end of a femur. The partial femur is assignable to an as-yet-unrecognized large ornithomimosaur of similar size to the Asian taxon Gallimimus and an unnamed animal from the Campanian Dinosaur Park Formation of Alberta (Longrich, 2008). Both New Jersey specimens show marks attributable to feeding, the tibia shaft bearing ones from crocodyliforms and the femur from sharks, allowing for insight into the faunal composition and paleoecology of Maastrichtian communities along the coast of the Cretaceous Atlantic Ocean (Fiorillo, 1991;Gallagher, 1995;Schwimmer, 1997;Chure, Fiorillo & Jacobsen, 1998;Schwimmer, 2002;Rogers, Krause & Rogers, 2003;Jennings & Hasiotis, 2006;Reisz & Tsuji, 2006;Schwimmer, 2010;Noto, Main & Drumheller, 2012;Main, Noto & Weishampel, 2014;Adams, Noto & Drumheller, 2017). ...
Direct evidence of paleoecological processes is often rare when the fossil record is poor, as in the case of the Cretaceous of eastern North America. Here, I describe a femur and partial tibia shaft assignable to theropods from two Late Cretaceous sites in New Jersey. The former, identifiable as the femur of a large ornithomimosaur, bears several scores interpreted as shark feeding traces. The tibia shaft has punctures and flaked bone from the bites of mid-sized crocodyliforms, the first documented occurrence of crocodyliform traces on dinosaur bone from the Maastrichtian of the Atlantic Coastal Plain. The surface of the partial tibia is also littered with indentations interpreted as the traces of invertebrates, revealing a microcosm of biological interaction on the coastal seafloor of the Cretaceous Atlantic Ocean. Massive crocodyliforms, such as Deinosuchus rugosus and the slightly smaller Deltasuchus motherali , maintained the role of terrestrial vertebrate taphonomic process drivers in eastern North America during the Cretaceous. The report of crocodyliform bite marks on the ornithomimosaur tibia shaft in this manuscript reinforces the importance of the role of crocodyliforms in the modification of terrestrial vertebrate remains during the Cretaceous in North America. The preserved invertebrate traces add to the sparse record of the presence of barnacles and other marine invertebrates on dinosaur bone, and the evidence of shark feeding on the ornithomimosaur femur support the “bloat-and-float” model of terrestrial vertebrate fossil deposition in marine deposits from the Cretaceous of eastern North America.
... Finally, the North American record has also provided new material within Ornithomimosauria from the Lower Cretaceous beds of the United States (Ornithomimosaur indet: Brownstein, 2017) to the Upper Cretaceous beds of Mexico (Tototlmimus packardensis: Serrano-Brañas et al., 2016) and Canada (Ornithomimid indet: Longrich, 2008). ...
The first expedition to Las Hoyas fossil site took place in 1985, led by José Luis Sanz. A decade later, Pelecanimimus polyodon was discovered, being the first non-avian dinosaur found in the site and the first ornithomimosaurian described in Europe. Ornithomimosauria is one of the major coelurosaurian groups, and a clade of highly specialized theropods. Over the last 25 years, the known diversity of the ornithomimosaurs has increased throughout the world. The review of the holotype of Pelecanimus and the integration of new information about Ornithomimosauria are key to understanding the evolutionary history of this theropod lineage.
... Here, we describe the specimen collected by Friday as a new Early Cretaceous ornithomimosaur. The ornithomimosaur 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;Serrano-Brañas 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. ...
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.
... Although theropods exhibit an overall phylogenetic decrease in body size toward the origin of birds (Turner et al. 2007; also see Carrano 2006;Benson et al. 2014), several clades of theropods and ornithischians show trends of increase in body size in the Late Cretaceous (e.g., ceratopsids, oviraptorosaurs, dromaeosaurs; Turner et al. 2007;Zanno and Makovicky 2013;Benson et al. 2014; also see Funston et al. 2015). Among small theropods, occurrences of unusually large taxa during the upper Maastrichtian of North America are known for ornithomimosaurs, dromaeosaurids, and oviraptorosaurs (Longrich 2008;Zanno and Makovicky 2013;Lamanna et al. 2014;DePalma et al. 2015). The St. Mary River eggshell provides support for the previously noted trend of increase in eggshell thickness of theropod ootaxa, particularly in Continuoolithus and Prismatoolithus, which may document an in-crease in body size among oviraptorosaurs and troodontids, respectively, between the upper Santonian and the upper Maastrichtian in North America ( Fig. 7; Table 3). ...
North America is known for its rich uppermost Cretaceous record of dinosaur egg remains, although a notable fossil gap exists during the lower Maastrichtian. Here we describe a diverse dinosaur eggshell assemblage from the St. Mary River Formation of southern Alberta that, in conjunction with recently described eggs from the same formation in Montana, helps fill this gap and sheds light on the dinosaur diversity in this poorly fossiliferous formation. Three theropod eggshell types (Continuoolithus cf. C.canadensis, Montanoolithus cf. M.strongorum, and Prismatoolithus cf. P.levis) and one ornithopod (Spheroolithus cf. S.albertensis), are reported from Albertan exposures of the St. Mary River Formation, increasing the ootaxonomic diversity of the formation from two to five ootaxa. The taxonomic composition of the eggshell assemblage is consistent with the dinosaurian fauna known from the St. Mary River Formation based on skeletal remains. Spheroolithus eggshells constitute the majority of identifiable eggshells in our assemblage, a trend also observed in several other Upper Cretaceous formations from North America. Continuoolithus is shown to be synonymous with Spongioolithus, thus expanding the Maastrichtian geographic range of the ootaxon to include Utah. The St. Mary River eggshell assemblage supports a general trend of increase in eggshell thickness among theropod ootaxa from the uppermost Santonian through the Maastrichtian, which is inferred to reflect an increase in body size among some clades of small theropods through the Upper Cretaceous. Eggshell preservation in the St. Mary River Formation may be related to the semiarid climatic and environmental conditions that prevailed.
... Multivariate statistical analyses were performed in order to ascertain the variation among the theropod teeth from El Oterillo II site. The statistical analyses (discriminant function analyses) were performed using PAST v3.0 (Hammer et al. 2001) and SPSS 20.0 (SPSS Inc., Chicago, Illinois) on the dataset of Hendrickx et al. (2015b), which includes data from Farlow et al. (1991), Sankey et al. (2002), Currie and Varrichio (2004), Sankey et al. (2005), Smith et al. (2005), Smith and Lamanna (2006), Smith and Dalla Vecchia (2006), Fanti and Therrien (2007), Brusatte (2008), Longrich (2008), Sankey (2008), Hocknull et al. (2009), Molnar et al. (2009), Rauhut et al. (2010), Ö si et al. (2010, Larson and Currie (2013) and Hendrickx et al. (2015b); data from White et al. (2015) and Csiki-Sava et al. (2016) were also included. The dataset comprises 1022 teeth from different theropod taxa including El Oterillo II teeth (see Table 1). ...
... Such a configuration results in a proportionally very narrow metatarsal (typical condition of arctometatarsalia, see Holtz, 1994), compatible with the long and narrow traces of the metatarsals in the Italian specimens. Based on the dimensions of a complete skeleton of Struthiomimus altus figured in Longrich (2008, fig. 6, p. 985) the putative trackmaker would have had a hip height of about 1.06 m and a total body length of about 2.8 m. ...
We compare theropod footprints with elongate metatarsal prints from central Italy with known autopod structures in major theropod groups, in order to more accurately define the trackmaker attribution. Our work, using morphometric analysis, shows the considerable potential of explorative methods such as PCA (principal component analysis) and cluster analysis when describing important characters for a given taxonomic group (body and ichnofossils) and identifying important anatomical regions. Moreover, the results of the analysis suggest that the putative trackmaker is likely a member of Ornithomimosauria, with significant affinities in the posterior autopod structure with the genus Struthiomimus . The fundamental importance of integrating both osteological and ichnological data, when investigating locomotor and behavioural hypotheses, is highlighted. This approach could also contribute positively to the complex cognitive process of trackmaker identification and be favourable for the attainment of a more natural definition of ichnotaxa.
... Non-avian dinosaurs were especially diverse, with over 45 known species 6 , making this the most diverse known dinosaur assemblage. Ornithischians included hadrosaurs, ceratopsians, ankylosaurs, thescelosaurs, and pachycephalosaurs 5,6,40,41 and theropods included tyrannosaurids, ornithomimids, caenagnathids, troodontids, and dromaeosaurs [42][43][44][45] and eight species of ornithurine bird 46 . A diverse mammalian fauna occurs as well 47,48 . ...
The horned dinosaur Chasmosaurus from the late Campanian Dinosaur Park Formation of Alberta, is known from numerous skulls and skeletons, but over a century after its description, the taxonomy of the genus is controversial. Two species, Chasmosaurus belli and C. russelli, are currently recognized, with a third species, C. irvinensis, recently placed in a new genus, Vagaceratops. Here, the Yale Chasmosaurus skull is described, and implications for Chasmosaurus systematics are explored. The Yale skull is intermediate between typical C. belli and C. irvinensis. C. belli-like features include large, triangular lateral epiparietals, large parietal fenestrae, and an emarginate parietal. Yet the skull also exhibits derived features of C. irvinensis, including a posteriorly inclined narial strut, brow horns replaced by rugose bosses, reduced parietal emargination, five pairs of epiparietals, and epiparietals that fuse at their bases and hook forward over the frill. Specimen-level phylogenetic analysis provides a hypothesis of relationships upon which to base the taxonomy of Chasmosaurus. C. belli is paraphyletic with respect to C. irvinensis, and the Peabody skull is closer to C. irvinensis than to other C. belli. The holotype of C. russelli clusters with C. belli, making C. russelli a junior synonym of C. belli. Accordingly, Chasmosaurus can be divided into three species: C. belli, C. irvinensis, and C. priscus sp. nov, including specimens previously referred to C. russelli. The systematics of Chasmosaurus show how specimen level phylogeny can provide an evolutionary framework upon which to establish taxonomies. However, the resulting phylogenies may lead to paraphyletic species and genera.
Ornithomimosauria consists of the ostrich-mimic dinosaurs, most of which showing cursorial adaptations, that often exhibit features indicative of herbivory. Recent discoveries have greatly improved our knowledge of their evolutionary history, including the divergence into Ornithomimidae and Deinocheiridae in the Early Cretaceous, but the early part of their history remains obscured because their fossil remains are scarce in the Aptian–Albian sediments. In recent years, many isolated ornithomimosaur remains have been recovered from the Aptian Kitadani Formation of Fukui, central Japan. These remains represent multiple individuals that share some morphological features common to them but unknown in other ornithomimosaurs, suggesting a monospecific accumulation of a new taxon. As a result of the description and phylogenetic analysis, the Kitadani ornithomimosaur is recovered as a new genus and species Tyrannomimus fukuiensis, the earliest definitive deinocheirid that complements our knowledge to understand the early evolutionary history of Ornithomimosauria. Due to its osteological similarity to Tyrannomimus, a taxon previously considered an early tyrannosauroid based on fragmentary specimens, namely Aviatyrannis jurassica, may represent the earliest ornithomimosaur from the Upper Jurassic of Europe, significantly expanding the temporal and biogeographic range of Ornithomimosauria. This finding fills a 20-million-year ghost lineage of Ornithomimosauria implied by the presence of the oldest fossil record of Maniraptora from the Middle Jurassic and is consistent with the hypothesis that their biogeographic range was widespread before the Pangaean breakup in the Kimmeridgian.
Sexual dimorphism – sex-specific differences in morphology and appearance – can be observed in many animals and is most obvious when it involves external and soft-tissue features, such as reproductive organs or brightly coloured feathers. In many cases, these features are accompanied by corresponding variations in the skeleton which can be subtle, but still sufficient to confidently tell the sexes apart. However, identifying differences in extinct animals remains a significant challenge, with a clear-cut example of sexual dimorphism in dinosaurs proving particularly elusive.
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.
Abstract: Tyrannosaurids were the apex predators of Late Cretaceous Laurasia and their status as dominant carnivores has garnered considerable interest since their discovery, both in the popular and scientific realms. As a result, they are well studied and much is known of their anatomy, diversity, growth, and evolution. In contrast, little is known of the earliest stages of tyrannosaurid development. Tyrannosaurid eggs and embryos remain elusive, and juvenile specimens — although known — are rare. Perinatal tyrannosaurid bones and teeth from the Campanian–Maastrichtian of western North America provide the first window into this critical period of the life of a tyrannosaurid. An embryonic dentary (cf. Daspletosaurus) from the Two Medicine Formation of Montana, measuring just 3 cm long, already exhibits distinctive tyrannosaurine char- acters like a “chin” and a deep Meckelian groove, and reveals the earliest stages of tooth development. When considered to- gether with a remarkably large embryonic ungual from the Horseshoe Canyon Formation of Alberta, minimum hatchling size of tyrannosaurids can be roughly estimated. A perinatal premaxillary tooth from the Horseshoe Canyon Formation likely pertains to Albertosaurus sarcophagus and it shows small denticles on the carinae. This tooth shows that the hallmark characters that distinguish tyrannosaurids from other theropods were present early in life and raises questions about the ontogenetic variability of serrations in premaxillary teeth. Sedimentary and taphonomic similarities in the sites that pro- duced the embryonic bones provide clues to the nesting habits of tyrannosaurids and may help to refine the prospecting search image in the continued quest to discover baby tyrannosaurids.
Here we report the discovery of a non-avian theropod manus claw and various closely associated caudal vertebrae from a Lower Cretaceous exposure of the Tugulu Group, in the Junggar Basin. The gross anatomy of the vertebrae indicate an ornithomimosaur affinity, and a morphometric analysis of the claw supports this diagnosis. As is consistent with the known morphology of basal ornithomimisaur manual unguals, the claw is strongly curved, relatively robust, and possesses a prominent distoventral flexor tubercle. The centrum of one caudal vertebra narrows noticeably anteroposteriorly, suggesting that it is from very near the terminus of the tail. This fragmentary material constitutes the first record of an ornithomimosaur known from the Junggar Basin.
The vertebrate fauna of the Late Cretaceous Mussentuchit Member of the Cedar Mountain Formation has been studied for nearly three decades, yet the fossil-rich unit continues to produce new information about life in western North America approximately 97 million years ago. Here we report on the composition of the Cliffs of Insanity (COI) microvertebrate locality, a newly sampled site containing perhaps one of the densest concentrations of microvertebrate fossils yet discovered in the Mussentuchit Member. The COI locality preserves osteichthyan, lissamphibian, testudinatan, mesoeucrocodylian, dinosaurian, metatherian, and trace fossil remains and is among the most taxonomically rich microvertebrate localities in the Mussentuchit Member. To better refine taxonomic identifications of isolated theropod dinosaur teeth, we used quantitative analyses of taxonomically comprehensive databases of theropod tooth measurements, adding new data on theropod tooth morphodiversity in this poorly understood interval. We further provide the first descriptions of tyrannosauroid premaxillary teeth and document the earliest North American record of adocid remains, extending the appearance of this ancestrally Asian clade by 5 million years in western North America and supporting studies of pre-Cenomaninan Laurasian faunal exchange across Beringia. The overabundance of mesoeucrocodylian remains at the COI locality produces a comparatively low measure of relative biodiversity when compared to other microvertebrate sites in the Mussentuchit Member using both raw and subsampling methods. Much more microvertebrate research is necessary to understand the roles of changing ecology and taphonomy that may be linked to transgression of the Western Interior Seaway or microhabitat variation.
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.
The Cretaceous landmass of Appalachia has preserved an understudied but nevertheless important record of dinosaurs that has recently come under some attention. In the past few years, the vertebrate faunas of several Appalachian sites have been described. One such locality, the Ellisdale site of the Cretaceous Marshalltown Formation of New Jersey, has produced hundreds of remains assignable to dinosaurs, including those of hadrosauroids of
several size classes, indeterminate ornithopods, indeterminate theropods, the teeth, cranial, and appendicular elements of dromaeosaurids, ornithomimosaurians, and tyrannosauroids, and an extensive microvertebrate assemblage. The theropod dinosaur record of the Ellisdale site is currently the most extensive and diverse known from the Campanian of Appalachia. Study of the Ellisdale theropod specimens suggests that at least four or more non-avian theropod taxa are represented at the site, including tyrannosauroids, ornithomimosaurs, several different morphotypes of dromaeosaurids that are the first of that clade described from New Jersey, and indeterminate theropods. The specimens are important for increasing current knowledge about the theropod diversity of the Atlantic Coastal Plain (ACP) during
the Campanian by representing the most speciose assemblage of the group during the time in the ACP as well as for shedding light on Appalachian dinosaur ecology and biogeography generally.
Direct documentation of the ecology of past life is often rare when the fossil record is comparatively poor, as in the case of the terrestrial fauna of the Maastrichtian of eastern North America. Here, I describe a femur and partial tibia shaft assignable to theropods from the Maastrichtian Big Brook locality of New Jersey. The former, identifiable to a previously undetected morphotype of large ornithomimosaur, bears several scrapes identifiable as the feeding traces of sharks, adding to the collection of terrestrial vertebrate remains bearing such marks from the state. The latter is littered with tooth marks and punctures from possibly multiple crocodyliform individuals, the first documented occurrence of such traces on dinosaur bone from the Maastrichtian of the Atlantic Coastal Plain. Additionally, its surface is dotted with likely traces of invertebrates, revealing a microcosm of biological interaction from the Maastrichtian New Jersey shoreline. Previously, the massive Campanian crocodylian taxon Deinosuchus rugosus and the slightly smaller Cenomanian-age Texas crocodyliform Deltasuchus motherali have been shown as important drivers of terrestrial vertebrate taphonomy in eastern North America. The report of crocodyliform bite marks on the ornithomimosaur metatarsal shaft in this manuscript reveals that crocodylians continued to play role in the taphonomy of large dinosaurs in eastern North America through the end of the Mesozoic. The preserved invertebrate traces add to the sparse record of their traces on dinosaur bone, and the presence of shark scrapes on the femur supports the “bloat-and-float” model of terrestrial vertebrate fossil deposition in eastern North America.
Introduction
The relationship between dinosaur carcasses and isolated theropod teeth is well known in the fossil record. The usual explanation is that theropod dinosaurs fed on the herbivore carcass. Other evidence is provided by theropod tooth marks on the surface of herbivore skeletal remains. In this work we study isolated theropod teeth and the tooth marks in evidence on the bones of the sauropod from El Oterillo II (Salas de los Infantes, Spain, Lower Cretaceous). Theropod and crocodylomorph teeth have been found in relationship with the sauropod carcass. The fossils lie on channel lag deposits composed of sandstones with quartzite gravel.
Materials and methods
Thirty theropod teeth have been studied using qualitative features, statistical and cladistics analysis in addition to the tooth marks present on the vertebrae.
Results
The morphology of the theropod teeth has revealed greater palaeobiodiversity in these faunas than previously known, including baryonychine spinosaurids, basal tetanurans, dromaeosaurids and a singular coelurosaurian. The presence of tooth marks and isolated theropod teeth in close relationship with the sauropod carcass could also provide new evidence of the scavenging of theropod dinosaurs on the sauropods of this age and location.
Conclusions
Six morphotypes of theropod teeth have been distinguished; the combination of basal and derived tetanurans is congruent with the known record from the Early Cretaceous of the Iberian Peninsula. The most probable explanation for the association of isolated theropod teeth and sauropod remains is the scavenging of the carcass by theropod dinosaurs.
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.
Centrosaurus brinkmani (sp. nov) is distinguished from Centrosaurus apertus by key features of its cranial ornamentation, including the shape and orientation of the postorbital horn and parietal ornamentation at parietal locus 3, the shape of the parietal ornamentation at locus 2, and the possession of accessory parietal ossifications developed as short spines on the caudal parietal ramus. This species is restricted to the Oldman Formation of southern Alberta and is the oldest ceratopsid represented by diagnostic material in Canada. Phylogenetic analysis of the Centrosaurinae suggests that the development of spike-like ornamentation at the parietal locus 3 parietal locus is inversely related to the development of the P1 parietal ornamentation. Résumé : Centrosaurus brinkmani (sp. nov) se distingue de Centrosaurus apertus par d'importants caractères de son ornementation crânienne dont la forme et l'orientation de la corne post-orbitale et de l'ornementation pariétale au locus pariétal no 3, la forme de l'ornementation pariétale au locus no 2 et la présence d'ossifications pariétales accessoires formant de courtes épines sur la rame caudale pariétale. La présence de cette espèce se limite à la Formation d'Oldman du sud de l'Alberta et il s'agit du plus ancien Cératopsidé représenté par du matériel diagnostique au Canada. L'analyse phylogénique des Centrosaurinés indique qu'il existe une relation inverse entre le développement de l'ornementation en forme de pointe au locus pariétal no 3 et le développement de l'ornementation au locus pariétal no 1.
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 remains of the omithomimid dinosaur Archaeomithomimus asiaticus from the Upper Cretaceous of the People's Republic of China are described and comparisons made with the bones of Elaphrosaurus, Gallimimus, Struthiomimus, Ornithomimus, Dromiceiomimus, Deinocheirus, and Allosaurus. The diagnosis of the Ornithomimidae of Russell (1972) is expanded to include the characters of Elaphrosaurus and Archaeomithomimus. Some of the remains from the Arundel Formation of Maryland that have been referred to Archaeomithomimus affinis are probably ornithomimid but are generically and specifically indeterminate.
The partial carpometacarpus of a basal ornithurine bird from the late Campanian of Dinosaur Provincial Park is described. Complete proximal fusion of the wrist and the presence of a pisiform process place this taxon in Ornithothoraces. Ornithurine synapomorphies include the large ventral ridge of the carpus and the concave proximal margin of the alular metacarpal, but the primitive structure of the pisiform process and extensor process preclude placement in Neornithes. The relatively thick walls of the bone and the distal placement of the extensor process are consistent with diving habits.
Stegoceras (sensu lato) has been the recipient of a number of species. Most have been placed into synonymy with S. validum, some have been transferred to other genera (i.e., Gravitholus, Ornatotholus), whereas others have been interpreted as being sexual dimorphs. A parsimonious phylogenetic analysis using 49 characters, which include 9 new cranial characters based on pachycephalosaur frontoparietal domes, now permits a revision of the genus Stegoceras. This analysis concludes that Stegoceras validum (sensu stricto) is a primitive, incipiently-domed pachycephalosaur that is characterized by a well-developed squamosal shelf and open supratemporal fossae. It is the sister taxon to the fully-domed Pachycephalosaurinae. The taxon Ornatotholus browni has a parietal and displays features identical to S. validum and is therefore a subjective junior synonym. Specimens consisting of flat, paired frontals are immature individuals of S. validum. The holotype of “Stegoceras” lambei, and all morphotypes of this species, are unique in the construction of the posterior squamosal region and are placed in a new genus, Colepiocephale. Colepiocephale lambei is known solely from the Foremost Formation and is the oldest diagnostic pachycephalosaur from North America. An incomplete, and indeterminate, skull from the upper part of the Milk River Formation (upper Santonian) has the distinction of being the oldest known North American pachycephalosaur. “S.” sternbergi lacks a posterior squamosal shelf and has squamosals directed laterally and is placed in a new genus, Hanssuesia, as H. sternbergi. Although the taxon Gravitholus albertae displays some characters (i.e., retention of the posterior squamosals separated by a distinct median parietal) and is similar to H. sternbergi in some respects, the holotype is too incomplete for any definitive diagnosis and thus it is considered a nomen dubium. Sphaerotholus is a subjective junior of Prenocephale and the species Sphaerotholus buchholtzae is a subjective junior synonym of Prenocephale edmontonensis. The taxa Prenocephale brevis, P. edmontonensis, and P. goodwini, form a monophyletic clade with monotypic Asian taxa Prenocephale prenes and Tylocephale gilmorei as an unresolved sister group. They are united by the possession of a distinct row of nodes on the squamosal and parietals. Tylocephale, if valid, is interpreted as the sister taxon to the Prenocephale clade. Stenotholus kohleri is formally recognized as a junior synonym of Stygimoloch spinifer. Based on the presence of hypertrophied nodes Stygimoloch spinifier and Pachycephalosaurus wyomingensis are united in the clade Pachycephalosaurini new taxon. Small-to-medium size Late Cretaceous pachycephalosaurs were rather diverse, especially during the late Campanian (Judithian), and many species coexisted during Campanian and Maastrictian times. Ancestry and directionality of dispersal (in part) of the North American and Asian taxa remains uncertain and certainly antedates Campanian time.
A new ornithomimosaur from the Yixian Formation of Liaoning Province People's Republic of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen is interesting because it has several primitive characters for ornithomimosaurs such as teeth and a short first metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we comment on the biogeographic history of this group.
THE Lower Cretaceous lithographic limestones from Las Hoyas (province of Cuenca, Spain) have yielded important vertebrate fossil remains. We report here a new specimen, the first ornithomimosaur theropod found in Europe. Pelecanimimus polyodon gen. et sp. nov., has some striking elements preserved, such as the hyoid, sternum and integumentary impressions. The fossil has revealed other unexpected features, including a derived hand in an ancient ornithomimosaur, and a large number of teeth (over 200) with a distinctive morphology. This specimen suggests an alternative evolutionary process towards the toothless condition in Ornithomi-mosauria, which could be explained by an exaptation. Pelecanimimus polyodon stresses the relationship between Troodontidae and Ornithomimosauria.
Tyrannosauridae can be subdivided into two distinct subfamilies-the Albertosaurinae and the Tyrannosaurinae. Previously recognized subdivisions Aublysodontinae and Shanshanosaurinae are rejected because they are based on insufficient material and juvenile specimens. Our results are based upon a phylogenetic analysis using PAUP program (Swofford 1999) of 77 skull characters and seven genera (Albertosaurus, Alioramus, Daspletosaurus, Gorgosaurus, Nanotyrannus, Tarbosaurus, and Tyrannosaurus); with Allosaurus as outgroup. Of the 77 characters used, more than half were parsimony informative. A single most parsimonious tree was obtained with the Tree Length being 88. The analysis of cranial characters and comparison of postcranial features reveal that Tarbosaurus bataar is not the sister taxon of Tyrannosaurus rex (contra Holtz 2001). Their similarities are partially due to the fact that both are extremely large animals. Thus, Tarbosaurus should be considered a genus distinct from Tyrannosaurus.
Chasmosaurus irvinensis (sp. nov.) is distinguished from other species of this genus by the possession of a broad snout, absence of a brow horn (the position of which is occupied by a pit or rugosities suggestive of bone resorption), broadly rounded and open jugal notch, subrectangular squamosal, straight posterior parietal bar bearing 10 epoccipitals, eight of which are flattened, strongly curved anterodorsally, and nearly indistinguishably coossified to their neighbours, and small, transversely oriented parietal fenestrae restricted to the posterior portion of the frill. This species, restricted to the upper part of the Dinosaur Park Formation, is significantly younger than the other recognized Canadian Chasmosaurus species, C. belli and C. russelli. Phylogenetic analysis shows that C. irvinensis is most closely related to the other Canadian Chasmosaurus species and more distantly related to Chasmosaurus mariscalensis from Texas.
Type material of the three original species of the genus Diclonius Cope consists of isolated hadrosaur teeth, none of which are adequate to define a taxon. A urodele vertebra orginally included in the type of D. perangulatus is removed to a new specimen number. Hadrosaurian teeth have too much variability within a single individual and too much morphologic overlap between species that can be distinguished by other anatomical features to be reliable sources of taxonomic characters at the specific, generic, and possibly subfamilial levels. Trachodon mirabilis is nomen dubium, although the name may be used in historical, but not taxonomic discussions. Claosaurus agilis should be redefined on the basis of non-dental characters. Anatosaurus copei, whose type was originally called Diclonius mirabilis, is a valid species, although not necessarily referable to the genus Anatosaurus. -Author
A collection of over 1,700 small theropod teeth from the Judith River Group (Campanian; ∼79.5–74 Ma) allows our understanding of the diversity and variation of small theropods in this assemblage to be refined. In addition to the previously recognized taxa, a series of morphologically distinct groups are recognized that may represent distinct taxa in some cases. Teeth with the Paronychodon-like features of a flat surface with longitudinal ridges on one side are resolved into a few discrete morphotypes. Two of these are included in Paronychodon lacustris and two additional morphotypes are hypothesized to represent distinct taxa, here referred to as ?Dromaeosaurus morphotype A and Genus and species indet. A. The teeth of Paronychodon lacustris and ?Dromaeosaurus morphotype A share a distinctive wear pattern that suggests tooth functioning involved contact between the flat surfaces of opposing teeth. Two species of Richardoestesia, R. gilmorei and R. isosceles, are present in the assemblage. Additionally, bird teeth are identified in the assemblage and are described in this review. Bivariate plots were used to document the variation in the theropod teeth, especially in the features that distinguish between Richardoestesia gilmorei, R. isosceles, Saurornitholestes, and Dromaeosaurus. Considerable overlap is present in all plots, so although the teeth are morphologically distinct, they are not easily distinguished by quantitative means.
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...
Sediments of the Upper Cretaceous (Campanian) Oldman Formation at Dinosaur Provincial Park, Alberta, have yielded an exceedingly rich fauna of dinosaurs. These fluviatile sediments show characteristics of both meandering and braided channels. Fossil molluscs, plants, and diverse salamanders indicate that Oldman sediments were deposited in fresh water, and the very sparse agglutinated Foraminifera recovered fail to controvert this conclusion. Annual growth rings in wood and vertebrate of Champsosaurus demonstrate that the climate was seasonal, and current botanic interpretations suggest that the climate was an equable, warm temperate one. Dinosaurian remains represent all stages of disarticulation from complete skeletons to isolated bones. They are common in channel sediments and rare in overbank deposits, suggesting that the animals preserved died in the water of channels. The persistence of the characteristics sedimentary association of fossils over a 200 ft. stratigraphic interval demonstrates that regular, not catastrophic events determined the preservation of individuals. Stages of progressive decomposition of dinosaurs are inferred from the condition of fossils collected from the Park. Disarticulated small bones occur at interfaces between mudstone and sandstone in which the sandstone lies above the mudstone, and also in intraformational conglomerates. Ceratopsians are identified as dwellers of the swampy lowlands along with hadrosaurs. Hadrosaurs, ceratopsians, and possibly even carnosaurs spent significant portions of their daily lives in water. These dinosaurs did not breed in “uplands”, but possibly in dry areas lateral to the streams.
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