Cranial Anatomy of New Specimens of Saurornitholestes langstoni (Dinosauria, Theropoda, Dromaeosauridae) from the Dinosaur Park Formation (Campanian) of Alberta

Abstract

The holotype of the dromaeosaurid Saurornitholestes langstoni was described in 1978 on the basis of fewer than 30 associated cranial and postcranial bones of a single individual from Dinosaur Provincial Park. Four additional partial skeletons of Saurornitholestes were recovered from Campanian (Upper Cretaceous) beds of Alberta and Montana over the next 25 years, although reasonably complete skeletons remained elusive, and virtually nothing was known about the skull. The lack of truly diagnostic material has been problematic, and the relationships of Saurornitholestes to other dromaeosaurids have been difficult to resolve because of the incomplete knowledge of its anatomy. In 2014, an almost complete skeleton, including the skull, was collected less than a kilometer from where the holotype had been found. Although similar in body size to Velociraptor, the facial region of the skull is relatively shorter, taller, and wider. The nasals are pneumatic. The premaxillary teeth are distinctive, and teeth previously identified in the Dinosaur Park Formation as Zapsalis abradens can now be identified as the second premaxillary tooth of S. langstoni. Morphology and wear patterns suggest that these may have been specialized for preening feathers. Many traits define a Campanian North American clade, Saurornitholestinae, that is distinct from an Asian clade that includes Velociraptor (Velociraptorinae). This new information on the skull allows a more complete evaluation of its systematic position within the Dromaeosauridae and supports the suggestion of at least two major faunal interchanges between Asia and North America during the Cretaceous. Anat Rec, 303:691–715, 2020. © 2019 American Association for Anatomy

New Dromaeosaurid Dinosaur (Theropoda, Dromaeosauridae) from New Mexico and Biodiversity of Dromaeosaurids at the end of the Cretaceous

“…The first phylogenetic analysis used 38 operational taxonomic units (34 ingroup OTUs) and 180 characters. These data were based on the study of Currie and Evans 22 , which was, in turn, based on the studies of Bell and Currie 30 , Evans et al 13 , and Longrich and Currie 10 . Data were run with TNT version 1.5 66 .…”

“…The dorsolateral process of the left lacrimal is subtriangular with a rounded point laterally, a conspicuous lacrimal fenestra, and is similar to those in other dromaeosaurids see refs. 22,23 (Fig. 2G).…”

“…Teeth of S. sullivani are gently curved, have slightly apically hooked denticles, less dense denticles (14-15 denticles per 5 mm compared to 18-20 in Dineobellator), and possess mesial denticles. It is also noted that one of the diagnostic features of S. langstoni are distal denticles that are strongly hooked apically 22 . Additionally, the maxillary and dentary teeth of S. langstoni are vertical and perpendicular to the alveolar margin and possess mesial carinae (although these tend to be mainly or completely proximal on the teeth) that are distinctly smaller than distal carinae.…”

Caenagnathids of the Dinosaur Park Formation (Campanian) of Alberta, Canada: anatomy, osteohistology, taxonomy, and evolution

“…Another concentration of caenagnathids has been recovered in the Steveville area ( Fig. 23B), which has historically produced numerous well-preserved specimens of the smaller-bodied animals of the DPF (Gilmore 1924b;Sternberg 1932;Fox 2005;Currie and Evans 2020). Caenagnathid abundance is low elsewhere in Dinosaur Provincial Park, but specimens have been recovered from almost all legal Sections with extensive outcrop ( Fig.…”

Paleobiology in the 21st Century

“…Our authors describe anatomy today in ways and from perspectives that were not available 100 years ago. This is still a vibrant component of paleobiology and as such makes up nearly half of this issue (Currie and Evans, 2020, in In addition to their description, they also examined bone histology and discussed the biology of the animal using quantitative body mass estimations. Even anatomical descriptions focused solely on primary anatomy and comparisons with other taxa often include cladistic analyses (quantitative assessments of the relationships between taxa), computed tomographic (CT) scans (Schachner et al, 2020, in this issue), and they also typically incorporate measurements that can be used in macroevolutionary analyses (Gatesy and Middleton, 1996;Hedrick et al, 2015).…”