Stenonychosaurus (North American Dinosaurs)

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It’s about 50% larger than any other troodontids previously known, making it one of the largest deinonychosaurs (raptor-like dinosaurs) we currently recognize.” a b Cullen, Thomas M.; Zanno, Lindsay; Larson, Derek W.; Todd, Erinn; Currie, Philip J.; Evans, David C. (2021-06-30). "Anatomical, morphometric, and stratigraphic analyses of theropod biodiversity in the Upper Cretaceous (Campanian) Dinosaur Park Formation1". Canadian Journal of Earth Sciences. 58 (9): 870–884. doi: 10.1139/cjes-2020-0145.

Evans, D. C.; Cullen, T.M.; Larson, D.W.; Rego, A. (2017). "A new species of troodontid theropod (Dinosauria: Maniraptora) from the Horseshoe Canyon Formation (Maastrichtian) of Alberta, Canada". Canadian Journal of Earth Sciences. 54 (8): 813–826. Bibcode: 2017CaJES..54..813E. doi: 10.1139/cjes-2017-0034.

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Stenonychosaurus teeth, however, are different from most other theropods. One comparative study of the feeding apparatus suggests that Stenonychosaurus could have been an omnivore. [16] The jaws met in a broad, U-shaped symphysis similar to that of an iguana, a lizard species adapted to a plant-eating lifestyle. Additionally, the teeth of Stenonychosaurus bore large serrations, each of which is called a denticle. There are pits at the intersections of the denticles, and the points of the denticles point towards the tip, or apex, of each tooth. The teeth show wear facets on their sides. Holtz (1998) also noted that characteristics used to support a predatory habit for Stenonychosaurus – the grasping hands, large brain and stereoscopic vision, are all characteristics shared with the herbivorous/omnivorous primates and omnivorous Procyon (raccoon).

Varricchio et al. (1997) described the exact structure of the nests. They were built from sediments, they were dish shaped, about 100 cm in internal diameter, and with a pronounced raised rim encircling the eggs. The more complete nests had between 16 (minimum number in MOR 246) and 24 (MOR 963) eggs. The eggs are shaped like elongated teardrops, with the more tapered ends pointed downwards and imbedded about halfway in the sediment. The eggs are pitched at an angle so that, on average, the upper half is closer to the center of the nest. There is no evidence that plant matter was present in the nest. a b Gilmore, C. W. (1932). A new fossil lizard from the Belly River Formation of Alberta. Transactions of the Royal Society of Canada, section 4, series 3 16:117-119 Legacy: failure and success. A non-trivial part of the dinosauroid story is the community’s reaction and how this affected Russell personally. As is well known, the idea suffered “much friendly abuse” (to quote Greg Paul in Predatory Dinosaurs of the World), several dinosaur specialists using the arguments outlined at the start of this article. I’m not pretending to be original on those points: such experts as David Raup, Stephen J. Gould, Thomas R. Holtz, jr, John Hutchinson and Greg Paul made them years before I published anything on the dinosauroid. Russell was very much aware of these criticisms ( Russell 1987, p. 127), something we saw reflected in his correspondence (Naish & Tattersdill 2021). It’s telling, however, that he never responded to them. In 2017, Evans and colleagues, building on the work of Zanno and others, confirmed the currently undiagnostic nature of the holotype of Troodon formosus and suggested that Stenonychosaurus be used for troodontid skeletal material from the Dinosaur Park Formation. [6] Later in 2017, Van der Reest and Currie found Stenonychosaurus to be a valid genus, but reassigned much of the known material to the new genus Latenivenatrix. [7] Polyodontosaurus (meaning "many-toothed lizard") is a potentially dubious genus of troodontid dinosaur named in 1932 by Charles W. Gilmore for a left dentary from the Dinosaur Park Formation. [1] It had been considered a synonym of Stenonychosaurus or Troodon for a significant time, before being declared a nomen dubium. The only known species is the type, P. grandis.

That which must not be discussed. I’m confident that another factor contributed to the construction of the dinosauroid, but it’s something more controversial than everything discussed so far and is also harder to establish with any degree of certainty. I think that Dale Russell’s specific personal views on the nature of the universe and the position of humans within it played a role in everything that happened. 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. [22] The hips we found could ultimately open the door for dozens of new species to be discovered. Researchers with other specimens now have two new species [Latenivenatrix mcmasterae and Stenonychosaurus inequalis] for comparison, widening our ability to understand the troodontid family tree in North America.” Confusion Amongst North American Troodontids The impact was immense, leaving a crater over 100 miles across and throwing huge amounts of debris into the atmosphere. 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

For most of the 19th and 20th centuries troodontid fossils from North America tended to be assigned to T. formosus. Based on this, Troodon ranged from Mexico in the south to Montana and beyond Alberta in the north and existed as a species through some fifteen million years. A contradiction indeed, when the rapid dinosaur faunal turnover of Laramidia in the Late Cretaceous is considered. The name was originally spelled Troödon (with a diaeresis) by Joseph Leidy in 1856, which was officially amended to its current status by Sauvage in 1876. [2] The type specimen of Troodon has caused problems with classification, as the entire genus is based only on one single tooth from the Judith River Formation. Troodon has historically been a highly unstable classification and has been the subject of numerous conflicting synonymies with similar theropod specimens. [3]Alternative Timeline Dinosaurs, the View From 2019 (Part 3): the Dinosauroid and its Chums, December 2019

Currie, P. J. (1987). "Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia)". Journal of Vertebrate Paleontology. 7: 72–81. doi: 10.1080/02724634.1987.10011638. Varricchio et al. (1997) described the exact structure of the nests. They were built from sediments, they were dish shaped, about 100cm (39in) in internal diameter, and with a pronounced raised rim encircling the eggs. The more complete nests had between 16 (minimum number in MOR 246) and 24 (MOR 963) eggs. The eggs are shaped like elongated teardrops, with the more tapered ends pointed downwards and embedded about halfway in the sediment. The eggs are pitched at an angle so that, on average, the upper half is closer to the center of the nest. There is no evidence that plant matter was present in the nest. I’ll end things there. Here’s your reminder that a pdf of Naish & Tattersdill (2021) is available if you message me. Like an increasing number of my academic projects these days, the production of this paper is linked tightly to the history of this blog. It is, indeed, thanks to TetZoo that my views on the dinosauroid became findable online in the first place and it’s thanks to the funding I receive via patreon and other donors that I was able to cover financial charges associated with this work. Thanks to everyone who helped in some way, especially to Will for his co-authorship, to the Canadian Museum of Nature staff who assisted in procurement of the images, and to Jordan for co-operation and the initial invitation. Moreover, three additional specimens from the same locality are referred to L. mcmasterae. These include UALVP 55804 (a partial pelvis), TMP 1982.019.0023 (a partial skull), and TMP 1992.036.575 (a right dentary and several left metatarsals). [2] Paul, G.S. (1988). Predatory Dinosaurs of the World. New York: Simon and Schuster. pp. 398–399. ISBN 978-0-671-61946-6.Horner, John R., Weishampel, David B. (1996) "A comparative embryological study of two ornithischian dinosaurs – a correction." "Nature" 383:256–257. Stenonychosaurus inequalis is known from the Dinosaur Park Formation of southern Alberta, Canada, which at the time was a warm coastal floodplain covered by temperate forests. Apex predators included tyrannosaurids such as Daspletosaurus and Gorgosaurus. Herbivores included hadrosaurids such as Lambeosaurus, Corythosaurus, and Prosaurolophus; ceratopsids such as Styracosaurus, Centrosaurus, and Chasmosaurus; ankylosaurs such as Scolosaurus, Euoplocephalus, and Edmontonia; and pachycephalosaurs such as Stegoceras and Foraminacephale.