Naish, D. & Tattersdill, W. 2021. Art, anatomy and the stars: Russell and Séguin’s dinosauroid. Canadian Journal of Earth Sciences https://doi.org/10.1139/cjes-2020-0172 However, Russell's thought experiment has been met with criticism from other paleontologists since the 1980s, many of whom point out that his Dinosauroid is overly anthropomorphic. Gregory S. Paul (1988) and Thomas R. Holtz, Jr., consider it "suspiciously human" and Darren Naish has argued that a large-brained, highly intelligent troodontid would retain a more standard theropod body plan, with a horizontal posture and long tail, and would probably manipulate objects with the snout and feet in the manner of a bird, rather than with human-like "hands". [9] Description [ edit ] Size compared to a human

If that unwelcome intruder from outer space hadn’t slammed into our planet 65 million years ago might Russell’s "dinosaurids" have used all this millennia to develop a civilisation far in advance of our own? The holotype of Stenonychosaurus inequalis, CMN 8539, is a partial skeleton consisting of six caudal vertebrae, hand bones, the distal end of the left tibia and astragalus, and a complete left foot. A couple of cranial specimens were also referred to the genus: UALVP 52611 (a nearly complete skull roof) and TMP 1986.036.0457 (a partial braincase). Varricchio et al. also found evidence for iterative laying, where the adult might lay a pair of eggs every one or two days, and then ensured simultaneous hatching by delaying brooding until all eggs were laid. MOR 363 was found with 22 empty (hatched) eggs, and the embryos found in the eggs of MOR 246 were in very similar states of development, implying that all of the young hatched approximately simultaneously. The embryos had an advanced degree of skeletal development and empty eggs were relatively uncrushed, implying that hatchlings were precocial. The authors estimated 45 to 65 total days of adult nest attendance for laying, brooding, and hatching. [21] However, the concept that all Late Cretaceous North American troodontids belong to one species began to be questioned soon after Currie's 1987 paper was published, including by Currie himself. Currie and colleagues (1990) noted that, while they believed the Judith River troodontids were all T. formosus, troodontid fossils from other formations, such as the Hell Creek Formation and Lance Formation, might belong to different species. In 1991, George Olshevsky assigned the Lance formation fossils, which had first been named Pectinodon bakkeri but later synonymized with Troodon formosus to the species Troodon bakkeri, and several other researchers (including Currie) reverted to keeping the Dinosaur Park Formation fossils separate as Troodon inequalis. [4]Latenivenatrix was found to be a derived troodontid (part of the newly defined Troodontinae), probably related to coeval Asian forms such as Linhevenator and Philovenator. [2] Paleobiology [ edit ] a b c d Russell, D. A.; Séguin, R. (1982). "Reconstruction of the small Cretaceous theropod Stenonychosaurus inequalis and a hypothetical dinosauroid". Syllogeus. 37: 1–43. The first specimens currently assigned to Troodon that were not teeth were both found by Sternberg in 1928, in the Dinosaur Park Formation of Alberta. The first was named Stenonychosaurus inequalis by Sternberg in 1932, based on a foot, fragments of a hand, and some tail vertebrae. A remarkable feature of these remains was the enlarged claw on the second toe, which is now recognized as characteristic of early paravians. Sternberg initially classified Stenonychosaurus as a member of the family Coeluridae. The second, a partial lower jaw bone, was described by Gilmore (1932) as a new species of lizard which he named Polyodontosaurus grandis. Later, in 1951, Sternberg recognized P. grandis as a possible synonym of Troodon, and speculated that since Stenonychosaurus had a "very peculiar pes" and Troodon "equally unusual teeth", they may be closely related. No comparable specimens were available at that time to test the idea.

Xu X, Tan Q, Sullivan C, Han F, Xiao D (2011) A Short-Armed Troodontid Dinosaur from the Upper Cretaceous of Inner Mongolia and Its Implications for Troodontid Evolution. PLoS ONE 6(9): e22916. doi:10.1371/journal.pone.0022916The teeth of these types of dinosaurs are recurved and have large serrations, unlike any dinosaur teeth found previously and so Leidy erected a new genus – Troodon (the name means “wounding tooth”). This staple of dinosaur books and academic literature for the best part of 160 years had been established on fairly shaky ground to begin with. Now thanks to some new research from University of Alberta graduate student Aaron van der Reest, T. formosus has been replaced by two taxa, one new one Latenivenatrix mcmasterae and one resurrected one. One of the first ever dinosaurs named from North America has officially bitten the dust in taxonomic terms as the troodontid Troodon formosus is no longer a valid genus. Varricchio et al.(1997) were able to extract enough evidence from the nests to infer several characteristics of troodont reproductive biology. The results are that they appear to have had a type of reproduction that is intermediate between crocodiles and birds, as phylogeny would predict. The eggs are statistically grouped in pairs, which suggests that the animal had two functional oviducts, like crocodiles, rather than one, as in birds. Crocodiles lay many eggs that are small proportional to adult body size. Birds lay fewer, larger, eggs. The Two Medicine troodont was intermediate, laying an egg of about 0.5kg (1.1lb) for a 50kg (110lb) adult. This is 10 times larger than reptiles of the same mass, but two troodont eggs are roughly equivalent to the 1.1kg (2.4lb) egg predicted for a 50kg (110lb) bird. The holotype of Stenonychosaurus inequalis, CMN 8539, is a partial skeleton consisting of six caudal vertebrae, hand bones, the distal end of the left tibia and astragalus, and a complete left foot. A couple of cranial specimens were also referred to the genus: UALVP 52611 (a nearly complete skull roof) and TMP 1986.036.0457 (a partial braincase). My research and writing (including the material that appears here) is supported by the contributions I receive via patreon. If you value what I do, please consider supporting it here.

Eberth, David A. (1997). "Judith River Wedge". In Currie, Philip J.; Padian, Kevin (eds.). Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 199–204. ISBN 978-0-12-226810-6. Varricchio, D. J. (1993). Bone microstructure of the Upper Cretaceous theropod dinosaur Troodon formosus. J. Vertebr. Paleontol. 13, 99–104. JSTOR 4523488 Stenonychosaurus lived approximately 12 million years before the end of the age of the dinosaurs and, according to Russell, may well have been as intelligent as the first humans. Given the time to develop, the descendants of Stenonychosaurus could well have evolved into an animal at least as capable as mankind.

Disclaimer

Troodons laid eggs in communal nests just like modern ostriches". Popular Science. 2023-04-03 . Retrieved 2023-04-05. Age determination studies performed on the Two Medicine troodont using growth ring counts suggest that this dinosaur reached its adult size probably in 3–5 years. [16] A scale drawing of a typical member of the Troodontidae dinosaur family. Picture credit: Everything Dinosaur.