New biological insights into the Middle Triassic capitosaurs from India as deduced from limb bone anatomy and histology

Abstract

Multiple limb bones of different Middle Triassic capitosaurs from India including Cherninia denwai and Paracyclotosaurus crookshanki were examined to reveal differences in palaeobiology and lifestyle adaptations. Limb bone anatomy of Cherninia is characterized by distinct torsion and its absence in the fore and hindlimb bones, respectively. Substantial torsion is seen in all the limb bones of P. crookshanki. Woven fibred bone tissue, a very rapidly deposited tissue mostly seen in the embryos and very young individuals of higher vertebrates, is reported for the first time in a juvenile temnospondyl. Predominance of incipient fibrolamellar bone tissue is seen in a large bodied Middle Triassic temnospondyl suggesting that such tissues in non‐amniotes helped in achieving large body sizes rapidly. Highly vascularized woven fibred bone tissue in the early ontogeny, transforming to a more stable incipient fibrolamellar bone tissue associated with growth marks later in ontogeny characterizes C. denwai. This suggests rapid sustained growth slowed down and became punctuated later in ontogeny. A continuous slow growth throughout ontogeny is suggested for P. crookshanki as parallel fibred bone and azonal lamellar bone tissue are seen in all the examined limb bones. The growth of C. denwai and P. crookshanki had variable susceptibility to seasonal fluctuations. The onset of sexual maturity was at 55% adult size for Cherninia as implied from the change in tissue type. Cherninia inhabited the bottom of the water column and acted as a passive benthic predator whereas Paracyclotosaurus was a shallow water predator that retained a high level of terrestriality.

Climatic influence on the growth pattern ofPanthasaurus maleriensisfrom the Late Triassic of India deduced from paleohistology

“…Studies including osteohistological research on Indian temnospondyls are rare (Ray, Mukherjee & Bandyopadhyay, 2009;Mukherjee, Ray & Sengupta, 2010;Mukherjee, Sengupta & Rakshit, 2020). Ray, Mukherjee & Bandyopadhyay (2009) provided preliminary results on the osteohistology of limb bones, ribs, and intercentra of three temnospondyl taxa from different Indian Triassic localities.…”

“…In the study by Mukherjee, Sengupta & Rakshit (2020), a larger dataset was analyzed histologically including 17 limb bones ranging from juvenile to adult ontogenetic stages. The studied taxa included Middle Triassic capitosaurids, such as Cherninia denwai (nine limb bones), Paracyclotosaurus crookshanki (five limb bones) and an indetermined capitosaurid (five limb bones).…”

Description of the metoposauridAnaschisma brownifrom the New Oxford Formation of Pennsylvania

“…Indeed, finite element analysis (FEA) of various stereospondyls to infer feeding behavior has identified the potential for ecological differentiation among the distinct morphotypes (e.g., Fortuny et al, 2011, 2012, 2016, 2017; Lautenschlager et al, 2016; Konietzko-Meier et al, 2018). Additionally, an increasing body of histological literature has identified disparate physiological capabilities and growth patterns among closely related taxa (e.g., Konietzko-Meier and Klein, 2013; Muhkerjee et al, 2020), indicating differing responses to local environmental conditions. Metoposaurids are actually the best sampled clade in this regard.…”

“…However, a number of studies do hint at cryptic ecological and physiological differentiation that could in turn explain the different geographic ranges of various clades. Muhkerjee et al (2010, 2020) suggested that some paracylotosaurid capitosaurs were more terrestrially capable than other stereospondyls, perhaps indicating a more shallow-water spatial occupation when in water. Some differences could also relate to the tolerance of various taxa.…”

Gondwana Vertebrate Faunas of India: Their Diversity and Intercontinental Relationships

“…The lower Denwa comprises multistoried, sheet-like medium-fine grained sandstone bodies interleaved with red mudstones, while the upper Denwa is a mudstone-dominated unit characterized by layers of ribbon-shaped channel-fill bodies and sandy to heterolithic sheet sandstones encased within the mudstones. The vertebrate assemblage (Table 1) includes the ceratodontid Ceratodus, the capitosaurs Paracyclotosaurus, Cherninia, and three indeterminate taxa, the undescribed brachyopid, the lonchorhynchine trematosaurid, an undescribed rhynchosaur, and various medium-large dicynodonts (Mukherjee and Sengupta, 1998;Bandyopadhyay and Sengupta, 1999;Mukherjee et al, 2019). Recently the horned allokotosaur Shringasaurus (Fig.…”