Stenonychosaurus (North American Dinosaurs)

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SPECULATION: Some scientists believe dinosaurs would eventually have achieved full sentience (Image: Canadian Museum of Nature / Getty) The scientific paper: “Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a Description of a Unique New Taxon: Implications for Deinonychosaur Diversity in North America” by Aaron J. van der Reest and Philip J. Currie published in the Canadian Journal of Earth Sciences. 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. Kidadl provides inspiration to entertain and educate your children. We recognise that not all activities and ideas are appropriate and suitable for all children and families or in all circumstances. Our recommended activities are based on age but these are a guide. We recommend that these ideas are used as inspiration, that ideas are undertaken with appropriate adult supervision, and that each adult uses their own discretio a b Sternberg, C.M. (1951). "The lizard Chamops from the Wapiti Formation of Northern Alberta: Polyodontosaurus grandis is not a lizard". Annual Report of the National Museum of Canada Bulletin. 123: 256–258.

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. Unfortunately, no comparable specimens were available at that time to test the idea. 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. This fast-running, bird-like dinosaur was first named and described in 1856 by the American palaeontologist Joseph Leidy and right from the very beginning there were problems over its description and classification. Troodon ( T. formosus), a dinosaur whose name provided the inspiration behind the erection of an entire dinosaur family, the Troodontidae (part of the Deinonychosauria clade), was described on the basis of the discovery of a fossilised tooth. Troodon formosus = Nomen Dubium Troodon formosus has been found from Mexico all the way to Alaska, spanning a 15 million year period — a fantastic and unlikely feat,” van der Reest said. For Aaron, being able to name a new dinosaur has been an especially emotional experience. The species name for Latenivenatrix mcmasterae honours his late mother, Lynne (McMaster) van der Reest who did so much to encourage him to pursue a career in palaeontology.

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Dinosaurs had been the dominant form of animal life on Earth for over 100 million years. For comparison, humans have been around only for about one million years. Currie, P. (1987). "Theropods of the Judith River Formation". Occasional Paper of the Tyrrell Museum of Palaeontology. 3: 52–60.

He goes on to envision a "dinosauroid" with a shorter muzzle and chillingly similar to contemporary popular representations of UFO pilots. In 1982, Dale A. Russell, then curator of vertebrate fossils at the National Museum of Canada in Ottawa, conjectured a possible evolutionary path for Stenonychosaurus, if it had not perished in the Cretaceous–Paleogene extinction event, suggesting that it could have evolved into intelligent beings similar in body plan to humans. Over geologic time, Russell noted that there had been a steady increase in the encephalization quotient or EQ (the relative brain weight when compared to other species with the same body weight) among the dinosaurs. Russell had discovered the first Troodontid skull, and noted that, while its EQ was low compared to humans, it was six times higher than that of other dinosaurs. Russell suggested that if the trend in Stenonychosaurus evolution had continued to the present, its brain case could by now measure 1,100cm 3 (67cuin), comparable to that of a human (on average, 1,260cm 3 (77cuin) for men and 1,130cm 3 (69cuin) for women). [1]Discovered in central Montana in 1855, it was among the first dinosaurs found in North America. Its species ranged widely, with fossil remains recovered from as far north as Alaska, and the Judith River formation of Alberta, and as far south as Wyoming and even possibly Texas and New Mexico. [2] Stenonychosaurus became a well-known theropod in the 1980s, when the feet and braincase were described in more detail. Along with Saurornithoides, it formed the family Saurornithoididae. Based on differences in tooth structure, and the extremely fragmentary nature of the original Troodon formosus specimens, saurornithoidids were thought to be close relatives while Troodon was considered a dubious possible relative of the family. Phil Currie, reviewing the pertinent specimens in 1987, showed that supposed differences in tooth and jaw structure among troodontids and saurornithoidids were based on age and position of the tooth in the jaw, rather than a difference in species. He reclassified Stenonychosaurus inequalis as well as Polyodontosaurus grandis and Pectinodon bakkeri as junior synonyms of Troodon formosus. Currie also made Saurornithoididae a junior synonym of Troodontidae. [2] In 1988, Gregory S. Paul went farther and included Saurornithoides mongoliensis in the genus Troodon as T. mongoliensis, [3] but this reclassification, along with many other unilateral synonymizations of well known genera, was not adopted by other researchers. Currie's classification of all North American troodontid material in the single species Troodon formosus became widely adopted by other paleontologists, and all of the specimens once called Stenonychosaurus were referred to as Troodon in the scientific literature through the early 21st century. Stenonychosaurus teeth, however, are different from most other theropods. One comparative study of the feeding apparatus suggests that Stenonychosaurus could have been an omnivore. [15] 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 herbivorous or omnivorous primates and omnivorous Procyon (raccoon). 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

Stenonychosaurus (meaning "narrow claw lizard") is a genus of troodontid dinosaur from the Late Cretaceous Dinosaur Park Formation of Alberta, Canada, as well as possibly the Two Medicine Formation. The type and only species, S. inequalis, was named by Charles Mortram Sternberg in 1932, based on a foot, fragments of a hand, and some caudal vertebrae from the Late Cretaceous of Alberta. S. inequalis was reassigned in 1987 by Phil Currie to the genus Troodon, which was reverted by the recognition of Stenonychosaurus as a separate genus from the possibly dubious Troodon in 2017 by Evans et al. and also later in the same year by Van der Reest and Currie. 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.But it’s an enticing thought. Douglas Dixon’s book The New Dinosaurs explores how dinosaurs might have adapted to exploit current evolutionary niches. He anticipates dino whales, dino giraffes…but could there be dino humans? 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. Troodons size ranged widely. In general, individuals that lived further north were larger than those that lived in more southern areas. Troodons in Alaska were especially large, up to 12 feet long, 5 feet tall, and weighing up to 175 pounds. Meanwhile, Troodons that lived in more southern locations were only around 7 feet long, 3 feet tall, and weighed up to 50 pounds, about the size of a Velociraptor. Very likely Troodon had feathers, but no fossil evidence for feathers has yet been found.

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). Troodon is considered to be one of the most derived members of its family. Along with Zanabazar, Saurornithoides, and Talos, it forms a clade of specialized troodontids. [3] In 2011, Zanno and colleagues reviewed the convoluted history of troodontid classification in Late Cretaceous North America. They followed Longrich (2008) in treating Pectinodon bakkeri as a valid genus and noted that it is likely the numerous Late Cretaceous specimens currently assigned to Troodon formosus, but that a more thorough review of the specimens is required. Because the holotype of T. formosus is a single tooth, this renders Troodon a nomen dubium. [3]He focused on a lesser-known dino – Stenonychosaurus inequalis – which boasted a large brain, opposable fingers with a very human-like grip and stereo vision that was at least the equal of ours.