Investigating the connection between paleopathology, histology, and caudal biomechanics of diplodocids (Dinosauria: Sauropoda)

Grace Ann Goetcheus

doi:10.17918/00011180

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Investigating the connection between paleopathology, histology, and caudal biomechanics of diplodocids (Dinosauria: Sauropoda)

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Investigating the connection between paleopathology, histology, and caudal biomechanics of diplodocids (Dinosauria: Sauropoda)

Grace Ann Goetcheus

Doctor of Philosophy (Ph.D.), Drexel University

Jun 2025

DOI:

https://doi.org/10.17918/00011180

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Abstract

Diplodocidae

Paleopathology

Sauropoda

Histology

A detailed investigation of the microscopic (material properties and histology), macroscopic (osteological and cartilaginous neutral poses and range of motion), and population (paleoepidemiological study of a monodominant bonebed) level connections to the high prevalence of vertebral pathologies in diplodocid dinosaurs is presented. Using gross morphologic examinations and computed tomography, a survey of a single population of Diplodocus sp. at the Mother's Day Quarry from the Morrison Formation of southern Montana reaffirms the significant concentration of pathologies in caudal vertebrae, with the extent and degree of fusion, especially through ligamentous ossification, increasing throughout ontogeny. Nanoindentation to determine the elasticity and hardness of Alligator mississippiensis vertebrae as an analog for diplodocid caudals reveals that mid-caudal vertebrae are the stiffest and act as a buttress for muscular force transmission, while distal caudal vertebrae are the most pliant under stress. These regions correspond to where vertebral fusion is highest and where vertebrae become "whip-tailed" in flagellicaudatans like diplodocids, respectively. Anterior caudal vertebrae also exhibit high stiffness to accommodate for both the distribution and absorption of forces from the large caudal muscles that propel crocodilians through water--or in the case of sauropods, aid in stabilizing and powering the tail during flexion. Further analysis of the mobility of the tail of Diplodocus hallorum suggests that the species held its caudal series almost entirely linearly and horizontally while in a neutral position. Vertebral co-ossification is associated with the loss of the m. caudofemoralis longus and the area where the risk of ventral inclination is at its highest, supporting the theory that ligamentous ossification in diplodocids is not strictly pathologic but instead acts to reinforce and support this particular region of the tail. The capacity for lateral range of motion in the tail of D. hallorum is greater than that along the dorsal or ventral planes, with fusion at the point of vertebrae with the longest centra acting as a buttress for forces associated with tail whipping in defense or combat, as is observed in many extant archosaurs with long bony tails. The results emphasize the importance of variances in caudal material properties, morphology, and pathology to the paleobiological function and behavior of the whip-tailed diplodocids.

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Title: Investigating the connection between paleopathology, histology, and caudal biomechanics of diplodocids (Dinosauria: Sauropoda)
Creators: Grace Ann Goetcheus
Contributors: Edward B. Daeschler (Advisor)
Loÿc Vanderkluysen (Advisor)
Awarding Institution: Drexel University
Degree Awarded: Doctor of Philosophy (Ph.D.)
Publisher: Drexel University; Philadelphia, Pennsylvania
Number of pages: xviii, 274 pages
Resource Type: Dissertation
Language: English
Academic Unit: Biodiversity, Earth, and Environmental Science (BEES); College of Arts and Sciences; Drexel University
Other Identifier: 991022093052204721

Investigating the connection between paleopathology, histology, and caudal biomechanics of diplodocids (Dinosauria: Sauropoda)

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