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RESEARCH PRODUCT

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

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Purpose Histological studies on temnospondyl amphibian bones remain rare. A systematic revision of the histology was applied for the purpose of testing the histovariability in the humeri and becoming new information about the growth pattern. Methods The present study includes 12 humeri of Metoposaurus krasiejowensis, which originate from the Late Triassic clay pit near Krasiejo´w, southwestern Poland. The specimens were scanned with a microCT and the histological thin-sections have been obtained with the standard petrographic method. Results The evaluation of the studied bones shows a uniform growth series resulting in one morphotype. Strikingly, the histological analysis reveals a greater diversity with two different histotypes: Histotype I shows a distinct differentiation between alternating zones and annuli with poor to moderate vascularization and increase of bone remodeling during growth. Histotype II does not show any distinct zones and annuli but is characterized by a high vascularization and fast growth coexisting with an extensive bone remodeling. Conclusions Based on these two different growth patterns, several hypotheses can be established: The specimens do not show any pattern of histological variation; humeri represent a taxonomic diversity; the analyzed Metoposaurus bones stem from two different populations separated by space and; or time or sexual dimorphism