It's not #TemnospondylTuesday anymore - the post this week was a little delayed due to personal travel - but it's Thursday now, so it can be #TemnospondylThursday! This week is part 2 of #MetoposauridMay and covers the latest research into metoposaurids (since 2016) that was done by people other than me (there are a fair bit)! Publications ordered chronologically. Up next week will be the riveting story of how I ended up working on temnospondyls!
Title: Feeding biomechanics of Late Triassic metoposaurids (Amphibia: Temnospondyli): a 3D finite element analysis approach. Authors: Fortuny J, Marcé‐Nogué J, Konietzko‐Meier D Published: March 2017 Journal: Journal of Anatomy DOI: 110.1111/joa.12605 Summary: Fortuny and colleagues used 3D finite element analysis (FEA) to assess stress distribution under various feeding models in the typically large Polish metoposaurid Metoposaurus krasiejowensis and the much smaller North American metoposaurid Apachesaurus gregorii. They showed that a bilateral (biting on both sides) mode of feeding, probably via ambush, was the most likely strategy employed by metoposaurids but also suggested that lateral (striking to one side) biting was also possible (though it induced higher stresses) and might be associated with more active hunting while swimming through the water column and passing a prey item on one side. Having two occipital condyles (rather than one as in many amniotes) that would articulate with the vertebral column would have limited the lateral striking to some degree. Stresses were most concentrated toward the back of the skull and the back of the palate, which may explain why many of the elements in these regions are thicker and more robustly constructed than the anterior regions. There aren't many differences between the two metoposaurids, but Apachesaurus had higher stress values in the various simulations, which the authors propose may have restricted the available food options a bit more. Title: Variability of growth pattern observed in Metoposaurus krasiejowensis humeri and its biological meaning. Authors: Teschner E, Sander P, Konietzko-Meier D Published: October 2017 Journal: Journal of Iberian Geology DOI: 10.1007/s41513-017-0038-y Summary: Teschner and colleagues sectioned 12 humeri of the Polish metoposaurid Metoposaurus krasiejowensis to examine growth patterns of this taxon. Although the humeri all share a high degree of similarity in their external anatomy, the internal histology and microanatomy could be divided into two histotypes that differ remarkably in vascularity, division of discrete growth zones and annuli, and a number of other features. These authors ruled out accidentally capturing some other temnospondyl in their sample (there are only two temno species from the Krasiejow pit) and thus favoured some hypothesis of infraspecific variation, but the precise driver(s) is difficult to determine. They suggested it could represent separate populations whose variable histology reflects variable climate conditions but also tossed out the ever-popular (and ever-hard-to-prove) hypothesis of sexual dimorphism, for which there is little evidence in temnospondyls. The two histotypes documented in humeri of Metoposaurus krasiejowensis (figure from Teschner et al., 2017).
Title: Taxonomy, morphometry and morphospace of cranial bones of Panthasaurus gen. nov. maleriensis from the Late Triassic of India. Authors: Chakravorti S, Sengupta D Published: October 2018 Journal: Journal of Iberian Geology DOI: 10.1007/s41513-018-0083-1 Summary: Chakravorti & Sengupta re-appraised the metoposaurids from India, which were first described by Chowdhury (1965). For a while, these specimens had been of disputed taxonomic relationship to the North American Koskinonodon perfectus (either congeneric or synonymous), but these authors clarified (hopefully for the last time) their relationships (neither of the previous options) and placed the Indian metoposaurid within its own genus, Panthasaurus. The authors were also the first to perform a full computer-assisted phylogenetic analysis of the Metoposauridae using primarily continuous data. The methods are...interesting, in my opinion, but readers should examine the paper themselves to assess how continuous data are turned into discrete characters in this analysis. Title: Reappraisal of 'Metoposaurus hoffmani' Dutuit, 1978, and description of new temnospondyl specimens from the Middle-Late Triassic of Madagascar (Morondava Basin). Authors: Fortuny J, Arbez T, Mujal E, Steyer J-S Published: April 2019 Journal: Journal of Vertebrate Paleontology DOI: 10.1080/02724634.2019.1576701 Summary: Fortuny and colleagues re-examined the metoposaurid record from Madagascar, which was essentially the worst known before their study because it was described on the basis of pretty fragmentary and cursorily described material by Dutuit (1978). As was conventional for the time, a new species was given for the material (Metoposaurus hoffmani), but Fortuny et al. concluded that the material is not sufficient to be diagnostic. Much of the material (example below) is complete enough to show metoposaurid affinities but not enough to identify distinctive features. As I often complain about, geography is not a taxonomic feature, so simply saying "it's from Madagascar" is not enough justification. The Malagasy metoposaurids are one of the few Gondwanan occurrences of the clade, which otherwise occurs across much of Laurasia, and they show a few similarities to the Indian metoposaurids that suggest some degree of north-south separation.
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