Skeletochronology and Paleohistology of Hyposaurus rogersii (Crocodyliformes, Dyrosauridae) from the Early Paleogene of New Jersey, USA

The paleohistology of dyrosaurids is known from a small sample, despite being common fossils and representing a rare lineage of crocodylomorphs that survived the Cretaceous–Paleogene extinction. Their lifestyle has been inferred only from sections of the snout, vertebrae, partial femur, and tibia. T...

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Bibliographic Details
Published in:Animals (Basel) 2021-10, Vol.11 (11), p.3067
Main Authors: Pellegrini, Rodrigo A., Callahan, Wayne R., Hastings, Alexander K., Parris, David C., McCauley, John D.
Format: Article
Language:English
Subjects:
Animals
Aquatic reptiles
Biomedical materials
Bone remodeling
Bones
Cretaceous
Crocodiles
Dinosaurs
Dyrosauridae
external fundamental system
Extinct animals
Extinction
Femur
Fossils
Histology
Holes
Hyposaurus
Laboratories
Lamellae
Lamellar bone
Light
Mass extinctions
Osteons
Osteoporosis
Osteosclerosis
Paleogene
paleohistology
Predators
Sexual dimorphism
sexual size dimorphism
skeletochronology
Skeleton
Species extinction
Swimming
Tibia
Vertebrae
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Summary:The paleohistology of dyrosaurids is known from a small sample, despite being common fossils and representing a rare lineage of crocodylomorphs that survived the Cretaceous–Paleogene extinction. Their lifestyle has been inferred only from sections of the snout, vertebrae, partial femur, and tibia. To improve this, we conducted a skeletochronological and paleohistological study of midshaft cross-sections of both femora and humeri of a nearly complete Hyposaurus rogersii skeleton. We found lamellar-zonal bone that underwent remodeling, evidenced by resorption cavities and abundant secondary osteons within the primary periosteal cortex. The osteons, mostly longitudinally oriented and arranged in circular rows, often anastomose radially along a linear path, resembling radial rows. The medullary cavity is completely open, lacking trabeculae: endosteal deposition is limited to thin lamellae surrounding the cavity. Analysis of cyclical growth marks and the presence of an external fundamental system indicate the specimen was a fully mature adult 17–18 years of age. Comparison of the skeleton to others suggests sexual dimorphism and that it was female. The open medullary cavity, and no evidence for pachyosteosclerosis, osteosclerosis, osteoporosis, or pachyostosis indicate H. rogersii was not a deep diver or a fast swimmer in the open ocean but a near-shore marine ambush predator.
ISSN:2076-2615
2076-2615
DOI:10.3390/ani11113067