Commentary: Additional observations on the skeleton of a juvenile Gryposaurus notabilis (Ornithischia: Hadrosauridae)

Recently, we published an article describing the skeleton of a juvenile Gryposaurus notabilis (Ornithischia: Hadrosauridae) from the upper Campanian of Dinosaur Provincial Park, Alberta (Mallon et al., 2023). This was in follow-up to Waldman's (1969) original description of the skull. The skeleton (Canadian Museum of Nature CMN catalogue number FV 8784) was collected in 1913 and has a rather complicated history that has not been detailed in print before. Notably, some new information on the specimen has recently come to our attention, providing us the opportunity to give a more detailed account here, and further support our results with new data on the completeness and preservation of the specimen shortly after it was first prepared. The skeleton was originally discovered by amateur fossil collector William E. Cutler, who at the time was collecting on behalf of the newly formed Calgary Syndicate of Prehistoric Research (Russell, 1966). Cutler was charged with furnishing fossils for the museum of the Calgary Natural History Society, which had recently been located in the basement of the local courthouse. However, Cutler lacked the experience necessary to collect the skeleton, so Barnum Brown (American Museum of Natural History AMNH), who was also collecting in the area at the time, secured it for the Society in consideration of another prospect (unpublished report on the 1913 paleontological expedition, AMNH). The skeleton was soon shipped to the Society's museum in Calgary, where it was partially prepared and displayed. However, the museum was subsequently overtaken by the city and shuffled between several buildings over the ensuing decades (Tanke, 2010). Correspondence on file at the CMN between James E. Thurston of the then-new Calgary Public Museum and Charles M. Sternberg of the Geological Survey of Canada states that the skeleton was damaged during these moves and because of inadequate storage conditions. Sternberg also suspected that much of the damage occurred at the hands of a pilfering public while CMNFV 8784 was on display. In 1936, arrangements were made to have CMNFV 8784 shipped to the Survey in Ottawa so that Sternberg could oversee its conservation prior to its planned exhibition at the Natural History Park on St. George's Island in Calgary (now the Calgary Zoo). Sternberg noted in correspondence that the skeleton was in such poor condition that it would make for a disappointing display. He also felt that a much larger skeleton would be a more popular showpiece. He therefore arranged to have an articulated, adult Corythosaurus skeleton sent to the Park, which has since come into the possession of the Royal Tyrrell Museum of Palaeontology (catalogue number TMP 1984.121.0001), in exchange for the small Gryposaurus skeleton. Complete Trachodon nomen dubium skeleton, young animal about 12 feet long. Specimen was found by W. E. Cutler and taken up by American Museum party for the Calgary Natural History Society, Calgary, Alta., Canada, August 1913. Belly River Formation, 200 ft. below Bearpaw Shales, Red Deer River, near mouth of Sand Little Sandhill Creek, 10 mi. below Steveville. The above measurements were likely taken in the field. They support some of the arguments in our original article (Mallon et al., 2023). For example, while Waldman (1969) estimated the total length of the skeleton at 3.3 m, we argued that the skeleton was probably closer to 4 m long, confirmed above (~3.7 m, excluding the distalmost caudal vertebrae, which were missing). The sole remaining (right) tibia is now preserved in two pieces, totaling 480 mm long. Because the two pieces do not fit snugly together, we suggested that the original length of the tibia must have been longer, also confirmed above (~495 mm). Based on the incomplete dimensions available to us at the time, we used allometric scaling equations to argue that the hindlimb of Gryposaurus probably scaled isometrically (Mallon et al., 2023). We noted that the tibia of CMNFV 8784 would have to be >550 mm long to force a negatively allometric trend, which we felt was unlikely. The actual tibial length of CMNFV 8784 confirms our skepticism and further supports an isometric trend. We trust that this more complete historical account of CMNFV 8784 provides useful background information concerning the present condition of the specimen, and that the newly supplied measurements further inform the postcranial allometry of the species. Jordan C. Mallon: Conceptualization; writing – original draft; writing – review and editing. David C. Evans: Writing – review and editing. Yuguang Zhang: Writing – review and editing. Hai Xing: Writing – review and editing. Thanks to Heather Smith for suggesting we submit this article as a Commentary, to Kiana Clark for assistance publishing the AMNH photo, and to Darren Tanke for discussion. Jordan C. Mallon is supported by funding from the Canadian Museum of Nature. David E. Evans is supported by NSERC Discovery Grant RGPIN-2018-06788. Hai Xing is supported by the National Natural Science Foundation of China, Grant/Award Number 42377447 and the BJAST Young Scholar Program, Grant/Award Number 24CE-YS-01. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.