Dots on a screen: The past, present, and future of morphometrics in the study of nonavian dinosaurs

Abstract

Using morphometrics to study nonavian dinosaur fossils is a practice that predates the origin of the word “dinosaur.” By the 1970s, linear morphometrics had become established as a valuable tool for analyzing intra‐ and interspecific variation in nonavian dinosaurs. With the advent of more recent techniques such as geometric morphometrics and more advanced statistical approaches, morphometric analyses of nonavian dinosaurs have proliferated, granting unprecedented insight into many aspects of their biology and evolution. I outline the past, present, and future of morphometrics as applied to the study of nonavian dinosaurs zeroing in on five aspects of nonavian dinosaur paleobiology where morphometrics has been widely utilized to advance our knowledge: systematics, sexual dimorphism, locomotion, macroevolution, and trackways. Morphometric methods are especially susceptible to taphonomic distortion. As such, the impact of taphonomic distortion on original fossil shape is discussed as are current and future methods for quantifying and accounting for distortion with the goal of reducing the taphonomic noise to biological signal ratio. Finally, the future of morphometrics in nonavian dinosaur paleobiology is discussed as paleobiologists move into a “virtual paleobiology” framework, whereby digital renditions of fossils are captured via methods such as photogrammetry and computed tomography. These primary data form the basis for three‐dimensional (3D) geometric morphometric analyses along with a slew of other forms of analyses. These 3D specimen data form part of the extended specimen and help to democratize paleobiology, unlocking the specimen from the physical museum and making the specimen available to researchers across the world.

Dinosaurs of all ilks bow and pay tribute to Peter Dodson, their intrepid chronicler, in an Anatomical Record Special Issue in his honor

“…Rather, to name just some, they span a glorious gamut: from detailed descriptions of unusual Therapods from New Jersey (really? hadrosaurs, Jimmy Hoffa…who knew Jersey was actually interesting; sorry, JL is a native New Yorker and has little control when commenting on New Jersey; Gallagher, 2023); reports on a new iguanodontian dinosaur from South Africa (Forster et al, 2023); new insights on evolutionary relationships from analyses of the hyolaryngeal apparatus in extant archosaurs (i.e., birds and crocodilians; Yoshida et al, 2023); new reconstructions of the pectoral girdle and forelimb musculature of Megaraptora (Rolando et al, 2023); insights from osteohistology of Dromornis stironi with implications for understanding the histology of Australian mihirung birds (Chinsamy et al, 2023); insightful observations on fracture and disease in a large‐bodied ornithomimosaur with insights into identifying unusual endosteal bone in the fossil record (Chinzorig et al, 2023); a comprehensive assessment of the history and future of the study of morphometrics in the study on non‐avian dinosaurs (Hedrick, 2023); detailed modeling to assess and predict the abundance of large carnivorous dinosaurs of the Upper Jurassic Morrison Formation and the Upper Cretaceous Dinosaur Park formation (by Peter and JL's Yale classmate, the ever‐creative James Farlow; JL is still in awe at all the super‐bright dino dudes that surrounded him at Yale “back in the day”; Farlow et al, 2023); to a number of papers—naturally—on Peter's great love, the ceratopsians, including those by lead Guest Editor Fiorillo (Fiorillo & Tykoski, 2023) and Peter's successor teaching anatomy at Penn, Ali Nabavizadeh (Nabavizadeh, 2023). Even the cover of this Special Issue has been a creative homage to Peter, lovingly created by Anatomical Record Associate Editor (and artist extraordinaire) Adam Hartstone‐Rose (Hartstone‐Rose et al, 2023).…”

Sample Size and Geometric Morphometrics Methodology Impact the Evaluation of Morphological Variation

“…GM techniques are commonly split into either two-dimensional (2D) image-based GM or three-dimensional (3D) GM. Each method has advantages and disadvantages ( Ford et al 2023 ; Hedrick 2023 ), but a primary advantage of 2DGM is that it is relatively inexpensive and possible to do within natural history collections themselves, thus not requiring specimen loans. When designing a 2DGM analysis for assessing differences in morphology among closely related taxa, workers must make decisions related to landmark number and placement, intraspecific sample size for determining intraspecific mean shape and shape variance ( Cardini et al 2015 , 2021 ; Cardini and Elton 2007 ), which element to evaluate, as well as which view or views should be used to characterize shape (e.g., differing views of the skull).…”

Introduction to Dinosaurs: New Ideas from Old Bones papers honoring Peter Dodson

“…They conclude that this latter case study suffered from sufficient data to accurately discriminate and/or too much temporal mixing (Gates et al, 2023). Hedrick (2023) examines the use of morphometrics as applied to studies of dinosaurs and identifies five aspects of non-avian dinosaur paleobiology where morphometrics has been widely utilized to advance our knowledge: systematics, sexual dimorphism, locomotion, macroevolution, and trackways. In addition, he provides a cautionary perspective on the impact of taphonomic distortion on fossil shape and proposes methods for quantifying and accounting for distortion with the goal of reducing the taphonomic noise-to-biological signal ratio (Hedrick, 2023).…”

“…In addition, he provides a cautionary perspective on the impact of taphonomic distortion on fossil shape and proposes methods for quantifying and accounting for distortion with the goal of reducing the taphonomic noise-to-biological signal ratio (Hedrick, 2023). He further comments on the growth of interest in 3D specimen data as a means for making specimens more widely available to a global audience (Hedrick, 2023).…”

“…Hedrick (2023) examines the use of morphometrics as applied to studies of dinosaurs and identifies five aspects of non‐avian dinosaur paleobiology where morphometrics has been widely utilized to advance our knowledge: systematics, sexual dimorphism, locomotion, macroevolution, and trackways. In addition, he provides a cautionary perspective on the impact of taphonomic distortion on fossil shape and proposes methods for quantifying and accounting for distortion with the goal of reducing the taphonomic noise‐to‐biological signal ratio (Hedrick, 2023). He further comments on the growth of interest in 3D specimen data as a means for making specimens more widely available to a global audience (Hedrick, 2023).…”