#ornithomimid

Dromiceiomimus brevitertius

A male in breeding plumage takes shelter from the sleet of a spring coldsnap

The second of my Horseshoe Canyon series. I didn't have any particular knowledge of ornithomimids before this piece and I think I might actually know less now that I've completed it. Specifically, this taxon in particular has been problematic for nearly it's entire existence. Originally it was named as a new species of Struthiomimus, and later given it's own genus by Russell in his review of the ornithomimids of Alberta. One of his chief characters for distinguishing this taxon was the ratio of tibia to femur length. This has proven very problematic as this ratio can be affected by individual variation and/or growth stage and subsequently Dromiceiomimus has been subsumed into Ornithomimus by various authors. Though the issue of whether it's synonymous with O. edmontonicus or a valid species within Ornithomimus is not agreed upon even by them. The most recent publication I could find was the Macdonald and Currie (2019) description of a near complete specimen. Therein they run a series of tests to see if the limb ratio is even a valid character, and to my surprise it seems to be so. Of the tested taxa (Dromiceiomimus, Ornithomimus, Struthiomimus, and Gallimimus) all kept a consistent ratio of tibia/femur length across absolute sizes, and therefore the ratio is independent of growth stage at least, suggesting that it could be a diagnostic character (Gallimimus is a small outlier, it had a slight negative allometry, the tibia shortened in comparison to the femur as the specimens got bigger). Combining this with subtle features of the hand and claws they reasoned that Dromiceiomimus was distinct at both the specific and generic levels.

As for depicting it, my best sources were the photos of the fossil from Macdonald and Currie (2018), the skeletal diagrams and thigh muscle reconstructions provided in Russel (1972), the "Ornithomimus brevitertius" skeleton in Paul (1989), and the image of the holotype pelvic girdle provided in Parks (1926). The integument of Ornithomimus has been fossilized in a couple specimens described in Zelenitsky et. al. (2012) and van der Reest, Wolfe, & Currie (2015). given the taxonomic issues, I figured the Ornithomimus integument would be appropriate. What surprised me about the integument was the wings. Specimen TMP 1995.110.1 preserves on its ulna carbonized traces of feather shafts. These traces disappear towards both the proximal and distal ends, meaning that the wing (pennibrachium of their terminology) would have been limited to the forearm and wouldn't continue onto the hand and 2nd finger, nor up to the shoulder as is the case in more derived maniraptors. It feels like a cardinal sin to depict dinosaur wings that way, but that's what the evidence shows for Ornithomimus at least.

The composition, colors, and pose were all inspired by Poodonkis (and if you get the reference maybe take something for your back pain). My challenge was to make him believably pink and spotted and to have him be 'snowed in.' I eventually settled on the idea that the bright pink would be male breeding plumage and since bullfinch, pine grosbeak, and pink headed fruit doves manage the color without filtering crustaceans like flamingoes or spoonbills I figured it could be justified. The spots could be either camouflage like a northern flicker or display like a peacock pheasant, so I done a little of both. The 'snowed in' was tougher, luckily there have been some determinations of paleoclimate for the Horseshoe Canyon Formation, most relevant here are the paleosol samples of Quinney et. al. (2013). Most of the specimens referred to Dromiceiomimus are from the Tolman Member of the formation, which was deposited in a cooler and drier interval. The mean annual temperature and precipitation determined by Quinney et. al. was comparable to those of modern Belgium and Luxembourg, which gives us a rough ballpark to play in. Close enough that I think a cold spring could reasonably produce a sleet storm, not quite a snow-in but close enough for the composition.

References:

Macdonald, I., Currie, P. J. (2018) Description of a partial Dromiceiomimus (Dinosauria: Theropoda) skeleton with comments on the validity of the genus. Canadian Journal of Earth Sciences 56: pg. 129-157. doi.org/10.1139/cjes-2018-0162

Russell, D. A. (1972) Ostrich Dinosaurs from the Late Cretaceous of Western Canada. Canadian Journal of Earth Sciences 9: pg. 375-402.

Paul, G. S. (1989) Predatory Dinosaurs of the World, Touchstone Simon & Schuster. pg. 391

Parks, W. A. (1926) Struthiomimus brevetertius - A new species of dinosaur from the Edmonton Formation of Alberta. Transactions of the Royal Society of Canada, series 3. 20(4), 65-70 (digitized, pg. 949-955)

Zelenitsky, D. K., et. al. (2012) Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins. Science 338: pg. 510-514. DOI: 10.1126/science.1225376

van der Reest, A. J., Wolfe, A. P., Currie, P. J. (2015) A densely feathered ornithomimid (Dinosauria: Theropoda) from the Upper Cretaceous Dinosaur Park Formation, Alberta, Canada. Cretaceous Research 58: pg. 108-117. doi.org/10.1016/j.cretres.2015.10.004

Quinney, A. et. al. (2013) Palaeoenvironmental and palaeoclimatic reconstruction of the Upper Cretaceous (late Campanian-early Maastrichtian) Horseshoe Canyon Formation, Alberta, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology 371: pg. 26-44. doi.org/10.1016/j.palaeo.2012.12.009

Ornithomimiosaurs!! I have a few more planned but this is the group I have so far. Arkansaurus - Gallimimus

Deinocheirus

Ornithomimus - Struthiomimus

This is a potential entry into the current design challenge, with a strong message... And an even stronger kick on that Ornithomimus!

toopid looking elephant goose

High in Coahuila, Mexico, a newly uncovered dinosaur sporting unusually extended forelimbs has been declared a “Mexican dragon.” Scientists say this bizarre species, some 73 million years old, offers further proof of Mexican dinosaurs’ remarkable but under-appreciated diversity.

Surprising New Find In Mexico

Mexico has emerged as a hotbed for unexpected dinosaur discoveries. The most recent addition to the roster is Mexidracon longimanus, dubbed by researchers as the “long-handed Mexican dragon.” It belongs to the ornithomimid or “ostrich-mimic” group, a clan of theropods famed for toothless beaks and slender, fast-running forms.

The first clue that Mexidracon wasn’t just another ostrich mimic? It’s unbelievably elongated metacarpals. The dinosaur’s slim palm bones made its hands exceed the length of its upper arms, which points to unique ways it found food. The forelimbs resembled present-day tree sloths, leading scientists to think it used such extended arms to collect plants for eating. Alternatively, some propose that this dino’s multi-jointed grasp might have been perfect for fishing in muddy waters, a scenario that fits the sedimentary environment brimming with oysters and other marine fauna.

Paleo-enthusiasts know that most of Mexico’s dinosaur finds date only to the 21st century. The roster includes horned ceratopsians, duck-billed hadrosaurs, and imposing tyrannosaurs. Each new genus emphasizes that the region’s Late Cretaceous habitats produced specialized lineages distinct from their northern counterparts in the U.S. or Canada. Such differences could point to partial geographic isolation that led to separate evolutionary paths.

The surface details also support the idea that Coahuila had pockets of rich biodiversity, possibly including wetlands or estuary-like ecosystems. That might explain why Mexidracon bones come from strata associated with watery deposits. If it inhabited marshy edges, those long arms may have assisted in rummaging through reeds or capturing small aquatic prey. Fragments from the same site reveal an environment dense with shellfish—an indicator that these dinosaurs likely contended with brackish shallows and migrating fish.

Odd And Extinct: Ornithomimid Lore

Ornithomimids—literally “bird mimics”—constitute a family of lightly built, bipedal dinosaurs with ostrich-like proportions, minus the feathers. Fossil impressions from Canada confirm that many sported a feathery coat, though whether that extended to flamboyant plumage remains unclear. Typically, these creatures possessed toothless beaks and were reputedly omnivorous, feeding on everything from leaves to small invertebrates. Unlike T. rex or raptors, they would not have been top predators. Instead, they roamed the land for fruit, seeds, insects, or maybe smaller reptiles, employing agility and speed to elude carnivores.

But “Mexidracon longimanus” sets itself apart with its uncommonly proportioned arms. The name “longimanus,” meaning “long-handed,” is apt, given that the palm alone outmatches the entire upper arm in length. Similar but less exaggerated builds in other ornithomimids prompted evolutionary debates: Did they rummage in trees or drag branches down to munch leaves? Could they have had a partial wading lifestyle, snapping up small fish? Despite theories, paleontologists seldom find direct evidence of feeding from fossilized intestines or last meals. Claws can hold clues: If robust or hooked, they might have aided in gleaning fruits or hooking small creatures.

To complicate matters, some have compared these elongated limbs to the arms of modern-day sloths—an apt analogy if the dinosaur’s joints and claws were adapted for snagging overhead vegetation or water prey. This radical shape diverges from the simpler designs in older or more typical “ostrich mimics,” suggesting unique ecological roles in the watery environment. Paleontologists think specialized foraging might have made Mexidracon a partial outlier among its broader group.

Seventy-Three Million Years Ago: Coahuila’s Cretaceous Scene

Geologically, the strata that entombed Mexidracon date to around 73 million years old, firmly placing it in the Campanian stage of the Late Cretaceous. At that time, vast shallow seas covered North America, leaving silt and sandy deposits brimming with marine creatures. Coahuila’s fossil trove, primarily discovered in the last two decades, has yielded an impressive variety of dinosaurs. These finds might eventually rival those in U.S. or Canadian badlands, rewriting the typical narrative that big, showy dinosaur species only roamed further north.

The presence of big hadrosaurs in Coahuila, plus local tyrannosaurids, suggests robust ecosystems, complete with migratory herbivores and apex predators. That Mexidracon thrived in watery margins is unsurprising, given how many dinosaur bones in Mexico are in brackish or nearshore contexts. The environment also explains the shell accumulations, leading to speculation that Mexidracon scavenged from tidepools or devoured tiny marine organisms on the muddy banks.

Such adaptability speaks volumes about how these creatures lived. They weren’t solely farmland roamers or pure forest dwellers: They were opportunists, taking advantage of coastal edges to feed on aquatic or semi-aquatic resources. That’s a far cry from how we often imagine “ostrich mimic” dinosaurs as land-lubbers. If more skeletons of this species or similar forms come to light, paleontologists can refine theories about how they hunted or gathered food.

Future Of Mexican Dino Discoveries

Morphological oddities like enormous metacarpals invite more profound evolutionary questions. Why are these elongated arms in a group typically known for quickness and minimal weaponry? Did the dinosaur face competition from other herbivores, prompting it to exploit resources in the treetops or shallow waters? Or was it a specialized fisher? Paleo-art and speculation are sure to flourish. Imaginative reconstructions already feature a small, lithe dinosaur wading in an estuary, arms extended like multi-pronged spears to snatch unsuspecting fish—be it romantic or purely hypothetical- underscores how morphological adaptation shapes survival strategies.

Beyond Mexidracon, the region’s trove includes some horned dinosaurs akin to Triceratops, crested hadrosaurs resembling the likes of Parasaurolophus, and fearsome predatory lineages, plus distinctly local forms that never ventured north. Each discovery cements the notion of a partial “Mexican province” in Late Cretaceous times, cut off enough from northern neighbors to evolve distinct species. That perspective redefines how we see North American dinosaur biogeography.

Looking ahead, paleontologists hope for more complete skeletons or, ideally, a well-preserved skull for Mexidracon. A more finished blueprint might confirm if its muzzle shape or crest variation (if any) influenced its feeding. The impetus rests on local field teams: Each year, advanced mapping, high-resolution imaging, and improved excavation methods uncover once-hidden remains in the region’s chalky rock layers.

Mexico is forging its identity as a cradle of improbable and specialized species. If the “Mexican dragon” stirs enough curiosity, it might become a local icon, spurring further hunts for the next big find.

While “Mexidracon” evokes dramatic imagery of a scaly beast, it’s grounded in credible scientific data. Those who imagine flamboyant sails or spines might be disappointed; the real appeal is the dinosaur’s improbable arms. Yet the richly varied environment it inhabited and the abiding puzzle of how it used those limbs keep the find in the public eye. Combined with Mexico’s rising star in paleontology, the “long-handed Mexican dragon” seems set to fascinate dinosaur enthusiasts and casual observers for years to come.