Description of a partialDromiceiomimus(Dinosauria: Theropoda) skeleton with comments on the validity of the genus

Abstract

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.

A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight

“…Rounding out the controversial basal ornithomimosaurs is Pelecanimimus , recovered as the first branching alvarezsauroid based on characters such as an elongate anterior maxillary ramus (311:1), posterior tympanic recess in the otic recess (27:1), lateral teeth set in grooves (302:1), over 30 dentary teeth (90:3), and a proximally expanded metacarpal II (370:0). Constraining it as an ornithomimosaur only requires two additional steps, however, where it emerges just above Shenzhousaurus as in Macdonald & Currie (2018). As only two of their characters supporting an ornithomimosaurian identification were not used by us, and only one from Brusatte et al (2014), its true position is unclear pending a detailed osteology such as Perez-Moreno’s (2004) unreleased description.…”

Maniraptoran pelvic musculature highlights evolutionary patterns in theropod locomotion on the line to birds

“…Compared to hips of earlier-branching theropods like tyrannosaurids and ornithomimids (Fig. 7) (Russell, 1972;Paul, 1998;Carrano, 2000;Hutchinson, 2001a;Carrano & Hutchinson, 2002;Hutchinson et al, 2005;Macdonald & Currie, 2019), Falcarius is much smaller in the postacetabulum and brevis fossa ( Figs. 2A-2B).…”

A limping dinosaur in the Late Jurassic: Pathologies in the pes of the neornithischianOthnielosaurus consorsfrom the Morrison Formation (Upper Jurassic, USA)

“…On the other hand, the impact fractures located in the phalanges III-1 and IV-4, which supported the weight of Othnielosaurus on the ground, might had causing chronic pain and, consequently, a limp. Similar cases of pedal pathologies affecting an individual's mobility have been described in the fossil record of dinosaurs, crocodyliforms and mammals, including hominoids (Hanna 2002;Farke and O'Connor 2007;Cabral et al 2011;Anné et al 2014;Foth et al 2015;McCrea et al 2015;Macdonald and Currie 2018;Hunt et al 2019). Survival of lesions of weight-bearing bone would have greater consequence for obligate bipeds and evidence of lesions healing in these bones is rare (Hearn and Williams 2019).…”