“Dragons” on the landscape: Modeling the abundance of large carnivorous dinosaurs of the Upper Jurassic Morrison Formation (USA) and the Upper Cretaceous Dinosaur Park Formation (Canada)

Abstract

Counts of the number of skeletal specimens of "adult" megaherbivores and large theropods from the Morrison and Dinosaur Park formations-if not biased by taphonomic artifacts-suggest that the big meat-eaters were more abundant, relative to the number of big plant-eaters, than one would expect on the basis of the relative abundance of large carnivores and herbivores in modern mammalian faunas. Models of megaherbivore population density (number of individuals per square kilometer) that attempt to take into account ecosystem productivity, the size structure of megaherbivore populations, and individual megaherbivore energy requirements, when combined with values of the large theropod/megaherbivore abundance ratio, suggest that large theropods may have been more abundant on the landscape than estimates extrapolated from the population density versus body mass relationship of mammalian carnivores. Models of the meat production of megaherbivore populations and the meat requirements of "adult" large theropods suggest that herbivore productivity would have been insufficient to support the associated number of individuals of "adult" large theropods, unless the herbivore production/biomass ratio was substantially higher, and/or the large theropod meat requirement markedly lower, than expectations based on modern mammals. Alternatively, or in addition to one or both of these other factors, large theropods likely included dinosaurs other than megaherbivores as significant components of their diet.

Big boned: How fat storage and other adaptations influenced large theropod foraging ecology

“…The apex predator role in Komodo National Park is at least partially vacant, yet scavenging resources and low metabolic costs allow Komodo dragons to exist at high biomass densities when compared to mammalian carnivores [ 105 ]. Because Allosaurus , and many other theropods in sauropod-dominated systems, also were highly abundant compared to modern mammalian carnivores [ 12 ], and were exposed to an overabundance of sauropod carrion meat resources, it is likely that the apex predator niche was ecologically vacant for them as well.…”

“…Agents were initialized with resource needs commensurate with those of a 2,000 kg carnivore, based on the field metabolic rate (FMR) equation for birds, yielding energy demands of ca. 29 kg of meat per day [ 11 , 12 ]. Importantly, Agents were written with dynamic metabolic budgets, so their individual resource needs were recalculated continually based on body mass, a preferred modelling approach in this kind of ABM, and allowed us to estimate adaptive optimum body mass [ 7 ].…”

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).…”

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

“…Farlow et al (2023) postulate in their study that the dominant contributing factor to supporting such large populations of large theropods was simply that megaherbivorous dinosaurs, while likely very important components of large theropod diets, were not their only prey, and at times and places possibly not even their most important prey. Rather, they suggest that adult “mid‐sized” dinosaurs were regularly killed by large theropods, along with juveniles of the megaherbivores (Farlow et al, 2023).…”

“…Counts of adult specimens of megaherbivores and large theropods from the very well‐studied Jurassic Morrison and Cretaceous Dinosaur Park formations suggest that large dinosaurian meat‐eaters were more abundant, relative to the number of megaherbivores, in contrast to patterns observed among mammal‐dominated terrestrial ecosystems (Farlow et al, 2023). Farlow et al (2023) postulate in their study that the dominant contributing factor to supporting such large populations of large theropods was simply that megaherbivorous dinosaurs, while likely very important components of large theropod diets, were not their only prey, and at times and places possibly not even their most important prey. Rather, they suggest that adult “mid‐sized” dinosaurs were regularly killed by large theropods, along with juveniles of the megaherbivores (Farlow et al, 2023).…”