Ornamentation of dermal bones of Metoposaurus krasiejowensis and its ecological implications

Abstract

BackgroundAmphibians are animals strongly dependent on environmental conditions, like temperature, water accessibility, and the trophic state of the reservoirs. Thus, they can be used in modern palaeoenvironmental analysis, reflecting ecological condition of the biotope.MethodsTo analyse the observed diversity in the temnospondyl Metoposaurus krasiejowensis from Late Triassic deposits in Krasiejów (Opole Voivodeship, Poland), the characteristics of the ornamentation (such as grooves, ridges, tubercules) of 25 clavicles and 13 skulls were observed on macro- and microscales, including the use of a scanning electron microscope for high magnification. The different ornamentation patterns found in these bones have been used for taxonomical and ecological studies of inter- vs. intraspecific variation.ResultsTwo distinct types of ornamentation (fine, regular and sparse, or coarse, irregular and dense) were found, indicating either taxonomical, ecological, individual, or ontogenetic variation, or sexual dimorphism in M. krasiejowensis.DiscussionAnalogies with modern Anura and Urodela, along to previous studies on temnospondyls amphibians and the geology of the Krasiejów site suggest that the differences found are rather intraspecific and may suggest ecological adaptations. Sexual dimorphism and ontogeny cannot be undoubtedly excluded, but ecological variation between populations of different environments or facultative neoteny (paedomorphism) in part of the population (with types of ornamentations being adaptations to a more aquatic or a more terrestrial lifestyle) are the most plausible explanations.

Redescription ofAnaschisma(Temnospondyli: Metoposauridae) from the Late Triassic of Wyoming and the phylogeny of the Metoposauridae

“…49C) reported one specimen (WT 3007, in part) from the Rotten Hill population with Metoposaurus-like ornamentation. Antczak & Bodzioch (2018) also document intraspecific variability in the ornamentation of pectoral elements in M. krasiejowensis. Another example includes the contact between the prefrontal and the maxilla; this is prominent in K. perfectus and typically absent in M. krasiejowensis owing to an anteromedial expansion of the lacrimal, but a few specimens of the latter (Sulej 2007, figs 5, 12) feature a slight contact, and one specimen (Sulej 2007, fig.…”

“…Furthermore, recent work on the clade (e.g. Sulej 2007;Lucas et al 2016) seems to actually confound attempts to discretely bin taxa because of a greater recognition of intraspecific variation in large samples (see also Antczak & Bodzioch 2018;Teschner, Sander, & Konietzko-Meier 2018). It is thus our interpretation that while the lack of taxonomic resolution is a direct result of low character sampling, the latter is influenced by a real biological phenomenon, namely the lack of morphological variation within Metoposauridae.…”

First occurrence of brachyopid temnospondyls in Southeast Asia and review of the Mesozoic amphibians from Thailand

“…The Plagiosauroidea possess cylindrical intercentra (Warren and Snell, 1991;Konietzko-Meier et al, 2014). The Brachyopoidea commonly show a wedge-shaped intercentrum in lateral view (Shishkin, 1991;Warren and Snell, 1991;Warren et al, 1997Warren et al, , 2011Warren and Dammiani, 1999;Averianov et al, 2008).…”

“…Based on the shape of the intercentrum and ornamentation pattern, these specimens could refer to either the late Triassic Mastodonsauroidea (e.g. Cyclotosaurus) or Metoposauroidea (Chowdhury, 1965;Warren and Snell, 1991;Sulej and Majer, 2005;Sulej, 2007;Brusatte et al, 2015;Antczak and Bodzioch, 2018). Therefore, more evidence is required for a familylevel identification.…”

Cranial suture biomechanics in Metoposaurus krasiejowensis (Temnospondyli, Stereospondyli) from the upper Triassic of Poland

“…The extensive record of osteohistological and 3D‐computational studies on the Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis is a good example in this respect. This taxon has been well described in terms of osteology (Dzik, Sulej, Kaim, & Niedźwiedzki, ; Barycka, ; Sulej, , ; Dzik & Sulej, ; Konietzko‐Meier & Wawro, ; Antczak & Bodzioch, ), histology (Gruntmejer, ; Gruntmejer et al, ; Gruntmejer, Konietzko‐Meier, Bodzioch, & Fortuny, ; Konietzko‐Meier et al, ; Konietzko‐Meier, Bodzioch, & Sander, ; Konietzko‐Meier, Danto, & Gądek, ; Konietzko‐Meier & Klein, ; Konietzko‐Meier & Sander, ; Teschner, Sander, & Konietzko‐Meier, ), and computational biomechanics (Fortuny, Marcé‐Nogué, & Konietzko‐Meier, ; Konietzko‐Meier et al, ). From these studies, a picture has emerged that describes Metoposaurus as an elongate, aquatic, animal that used its long and flattened tail for swimming (Konietzko‐Meier et al, ).…”