Bone Microstructure of Pareiasaurs (Parareptilia) from the Karoo Basin, South Africa: Implications for Growth Strategies and Lifestyle Habits

Abstract

Numerous morphological studies have been carried out on pareiasaurs; yet their taxonomy and biology remain incompletely understood. Earlier works have suggested that these herbivorous parareptiles had a short juvenile period as compared to the duration of adulthood. Several studies further suggested an (semi-) aquatic lifestyle for these animals, but more recent investigations have proposed a rather terrestrial habitat. Bone paleohistology is regarded as a powerful tool to assess aspects of tetrapod paleobiology, but few studies have been conducted on pareiasaurs. The present study assesses intra and inter-specific histovariability of pareiasaurs and provides fresh insights into their paleobiology, thereby permitting a re-evaluation of earlier hypotheses. Our sample comprises various skeletal elements and several specimens covering most of the taxonomic and stratigraphic spectrum of South African pareiasaurs, including large and basal forms from the Middle Permian, as well as smaller and more derived forms from the Late Permian. Our results concerning size of elements and histological tissues show that for pareiasaurs, element size is not a good indicator of ontogenetic age, and furthermore, suggest that the specific diversity of the Middle Permian pareiasaurs may have been underestimated. The bone histology of these animals shows that they experienced a relatively rapid growth early in ontogeny. Periosteal growth later slowed down, but seems to have been protracted for several years during adulthood. Pareiasaur bone microanatomy is unusual for continental tetrapods, in having spongious stylopod diaphyses and thin compact cortices. Rigorous paleoecological interpretations are thus limited since no modern analogue exists for these animals. Anat Rec, 300:1039-1066, 2017. © 2016 Wiley Periodicals, Inc.

Long bone histology of Chersina angulata : Interelement variation and life history data

“…This study represents the first histological study of long bones of the endemic Western Cape tortoise C. angulata . The study focuses on limb bones since they display less bone remodeling (Enlow, ) in the diaphyseal regions, and therefore preserve a more precise record of bone deposition through ontogeny (Canoville & Chinsamy, ; Chinsamy‐Turan, ; Francillon‐Vieillot et al, ). As vertebrates show a wide range of variation in histological characteristics and depositional rates (Ray et al, ; Ray & Chinsamy, ; Starck & Chinsamy, ), multi‐element studies of individuals provide a better assessment of their growth patterns, life habits and evolutionary history (Botha & Chinsamy, ; Ray, Mukherjee, & Bandyopadhyay, ).…”

Passive-Dynamic Walkers of the Late Paleozoic

“…A possible important evidence for the validity of the pareiasaurian walking technique proposed here is supplied by the available data on the limb bone histology of pareiasaurs (Canoville & Chinsamy, 2017;Boitsova et al, 2019). One of the major purposes of the investigations cited was to solve the old-standing terrestrial-vs.-semiaquatic dilemma of the pareiasaurian lifestyle.…”

“…The classic tubular bones could be expected for pareiasaurs, based on the recent isotopic analysis that supports their terrestriality (Canoville et al, 2014). However, the bone histology shows a much unexpected structure (Canoville & Chinsamy, 2017;Boitsova et al, 2019). Both the peripheral compacta and the marrow cavity were replaced by spongiosa in the long bones of the pareiasaurian limbs (and to a less extent in the other bones).…”

“…Therefore, it can be concluded that the spongy structure could have been better for pareiasaurians because it saved their limb bones from compression fractures at high-energy impacts. Furthermore, the intense internal remodeling of their bones (Canoville & Chinsamy, 2017;Boitsova et al, 2019) may indicate that the microscopic fractures did frequently occur but were persistently repaired. It is herein hypothesized that the lifetime microscopic compression fractures will be found in future studies of pareiasaurian bone histology.…”

“…Plausibility of the reconstruction have been tested by a reverse-engineering of the natural-sized walking model with pareiasaurian body proportions. The required mechanical properties of the limb skeleton have been tested against pareiasaurian bone histology which was recently discovered (Canoville & Chinsamy, 2017;Boitsova et al, 2019).…”