Bone Microstructure of the Stereospondyl Lydekkerina Huxleyi Reveals Adaptive Strategies to the Harsh Post Permian‐Extinction Environment

Abstract

The small-bodied stereospondyl Lydekkerina huxleyi, dominated the amphibian fauna of the South African Lower Triassic. Even though the anatomy of this amphibian has been well described, its growth strategies and lifestyle habits have remained controversial. Previous studies attributed the relative uniformity in skull sizes to a predominance of subadult and adult specimens recovered in the fossil record. Anatomical and taphonomic data suggested that the relatively small body-size of this genus, as compared to its Permo-Triassic relatives, could be linked to a shortened, rapid developmental period as an adaptation to maintain successful breeding populations under harsh environmental conditions. Moreover, Lydekkerina's habitat has been hypothesized to be either aquatic or mainly terrestrial. The current study, utilizes bone microstructure to reassess previous hypotheses pertaining to the biology and ecology of Lydekkerina. Various skeletal elements of different-sized specimens are analyzed to understand its growth dynamics, intraskeletal variability, and lifestyle adaptations. Bone histology revealed that our sample comprises individuals at different ontogenetic stages i.e., juveniles to mature individuals. Our results show that these amphibians, despite exhibiting plasticity in growth, experienced an overall faster growth during early ontogeny (thereby attaining sexual maturity sooner), as compared to most other temnospondyls. The microanatomy of the long bones with their thick bone walls and distinctive medullary cavity suggests that Lydekkerina may have been amphibious with a tendency to be more terrestrial. Our study concludes that Lydekkerina employed a peculiar growth strategy and lifestyle adaptations, which enabled it to endure the harsh, dry conditions of the Early Triassic. Anat Rec, 298:1237Rec, 298: -1254Rec, 298: , 2015. V C 2015 Wiley Periodicals, Inc.

Oxygen isotopes suggest elevated thermometabolism within multiple Permo-Triassic therapsid clades

“…Also from South Africa, five Lystrosaurus specimens from the lower Lystrosaurus AZ have δ 18 O p values similar to those of the co-existing semi-aquatic stereospondyl Lydekkerina (Schoch, 2008; Canoville and Chinsamy, 2015). In addition, an indeterminate lystrosaurid from the Induan Jiucaiyuan Formation of the Xinjiang Province has a δ 18 O p value similar (with a difference of −0.1 ± 0.6‰; Figure 2B) to that of the proterosuchid ‘ Chasmatosaurus ’ yuani , a basal archosauriform considered terrestrial and possessing an intermediate thermometabolsim based on a palaeohistological study (Botha-Brink and Smith, 2011).…”

“…A study dedicated to Rhinesuchus palaeohistology concluded that it had a fully aquatic lifestyle (McHugh, 2014), whereas Lydekkerina , a basal stereospondyl, was amphibious with a tendency to be terrestrial (Canoville and Chinsamy, 2015). …”

Variability of growth pattern observed in Metoposaurus krasiejowensis humeri and its biological meaning

“…Histological analyses of the postcranial skeleton of Temnospondyli are usually based on long bones, vertebrae or dermal bones (de Buffrénil et al 2016;Canoville and Chinsamy 2015;Damiani 2000;Gee et al 2017;Konietzko-Meier and Klein 2013;Konietzko-Meier and Sander 2013;Konietzko-Meier and Schmitt 2013;Konietzko-Meier et al 2012McHugh 2014;Mukherjee et al 2010;Ray et al 2009;de Ricqlès 1979;Sanchez and Schoch 2013;Sanchez et al 2010a, b;Steyer et al 2004;Witzmann 2009;Witzmann and Soler-Gijon 2010). However, only two histological studies are applied on humeri (Konietzko-Meier and Sander 2013; Mukherjee et al 2010).…”

A Juvenile Specimen of the Trematopid Acheloma From Richards Spur, Oklahoma and Challenges of Trematopid Ontogeny

“…Similar developmental plasticity is thus to be expected in temnospondyls and indeed is documented within the clade (e.g., Sanchez and Schoch, 2013;Schoch, 2014;Canoville and Chinsamy, 2015). We believe that this conservative approach is appropriate, given the relatively poor knowledge of early stages of ontogeny in trematopids.…”