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Puberty in a Mesozoic reptile

The histology of bone can be preserved virtually unaltered for hundreds of millions of years in fossils from all environments and all vertebrate taxa, giving rise to the flourishing field of paleohistology. The shafts of long bones are formed by the apposition of periosteal bone tissue, similar to the growth of wood, and preserve (an often cyclical) record of the growth of the individual and events in its life history. One such event is sexual maturation or puberty, during which hormonal changes transform the juvenile into a sexually mature adult. Puberty has been well studied in humans and some other living vertebrates. Here we describe puberty in Keichousaurus, a small sexually dimorphic and live-bearing marine reptile from Middle Triassic rocks of SW China, about 240 million years old. Using a combination of bone histology and morphology, we detected puberty as one of four life stages (the others being foetus, juvenile, and adult). Adult Keichousaurus males have a more robust humerus than females with pronounced muscle attachment sites and a triangular shaft cross section. Mid-shaft sections of the humeri of the males show the transition from the rounded juvenile cross section to the triangular adult cross section, as reflected in the contour of the growth marks. This shape change is produced by differential bone apposition of the periosteum, presumably triggered by sex hormones, as in humans, and influenced by changes in loading regime during puberty. This is the first report of puberty in a fossil amniote.

Details

Author
Qiang Li1, Jun Liu1, Nicole Klein2, Yasuhisa Nakajima3, P. Martin Sander4
Institutionen
1Division of Geology, School of Resources and Environmental Engineering, Hefei University of Technology, 230009 Hefei, China;Section Paleontology, Institute of Geosciences, University of Bonn, 53115 Bonn, Germany; 2Section Paleontology, Institute of Geosciences, University of Bonn, 53115 Bonn, Germany; 3Department of Natural Sciences, Faculty of Science and Engineering, Tokyo City University, 1588557 Tokyo, Japan; 4Division of Geology, School of Resources and Environmental Engineering, Hefei University of Technology, 230009 Hefei, China;Section Paleontology, Institute of Geosciences, University of Bonn, 53115 Bonn, Germany;The Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, 90007 CA, USA
Veranstaltung
GeoBerlin 2023
Datum
2023
DOI
10.48380/rtyn-1h76