Adam Bodzioch

Cranial bone histology of Metoposaurus krasiejowensis (Amphibia, Temnospondyli) from the Late Triassic of Poland

In this study, 21 skull bones of Metoposaurus krasiejowensis from the Late Triassic of Poland were investigated histologically. Dermal bones show a diploë structure, with an ornamented external surface. The ridges consist of mostly well vascularized parallel-fibered bone; the valleys are built of an avascular layer of lamellar bone. The thick middle region consists of cancellous bone, with varying porosity. The thin and less vascularized internal cortex consists of parallel-fibered bone. The numerous Sharpey’s fibers and ISF are present in all bones. The cyclicity of growth is manifested as an alternation of thick, avascular annuli and high vascularized zones as well as a sequence of resting lines. The detailed histological framework of dermal bones varies even within a single bone; this seems to be related to the local biomechanical loading of the particular part of the skull. The dynamic processes observed during the ornamentation creation indicate that the positions of the ridges and grooves change during growth and could be a specific adaptation to changing biomechanical conditions and stress distribution during bone development. In the supratemporal, the cementing lines show that the remodeling process could be involved in the creations of sculpture. The common occurrence of ISF suggests that metaplastic ossification plays an important role during cranial development. Endochondral bones preserved the numerous remains of calcified cartilage. This indicates that ossification follows a pattern known for stereospondyl intercentra, with relatively slow ossification of the trabecular part and late development of the periosteal cortex. The large accumulation of Sharpey’s fibers in the occipital condyles indicates the presence of strong muscles and ligaments connecting the skull to the vertebral column.

Diversity of Fish Scales in Late Triassic Deposits of Krasiejów (SW Poland)

Abstract. Taxonomy of extinct fishes is mostly based on the shapes of their bodies, teeth and skeletons and sometimes the coverage of the body. Analysis of modern fishes shows that sometimes even single-scale morphology can also be used as a taxonomic tool. In spite of the fact that variation in scales character in one species can be broad, some specific features distinguish species of the same genus. Analysis of the fossilized scales of fishes found in the Late Triassic deposits of Krasiejów (SW Poland) shows that the microstructure of the external surface of scales can also be considered as a taxonomic tool in the fossil record. Description of the ornamentation pattern of several scales of fishes from the same group shows diversity of the sculpture, which might be assigned to variation in morphology between several genera or species. Among the scales from Krasiejów there occur the oldest known ctenoid scales (sensu stricto) belonging to acanthopterygians.

Ornamentation of dermal bones of Metoposaurus krasiejowensis and its ecological implications

Background Amphibians 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. Methods To 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. Results Two 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. Discussion Analogies 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.

Morphology and preliminary biomechanical interpretation of mandibular sutures in Metoposaurus krasiejowensis (Temnospondyli, Stereospondyli) from the Upper Triassic of Poland

AbstractThe morphology of the mandibular sutures in the Late Triassic temnospondyl Metoposaurus krasiejowensis has been examined in order to determine their role in mandible biomechanics. Until now, no histological studies of mandibular sutures in extinct vertebrates were performed, in contrast to cranial sutures. As a consequence, mandibular suture interpretations herein are based mainly on comparisons with previous studies of cranial sutures and with 3D cranial finite element analysis of this species. A total of 32 standard thin sections were studied under standard petrographic microscope observations in order to differentiate the morphology of mandibular sutures. Five mandibular suture types are present in this taxon: interdigitated, shallowly interdigitated, overlapping, tongue and groove and abutting. Based on previous work, it has generally been assumed that the shallowly interdigitated, tongue, groove and abutting suture types are associated with tension, the interdigitated type with compression and the overlapping type with absorption and counteraction of variable loads. The sutures associated with tension occur mainly in the anterior part of the mandible, principally in the dentary; overlapping sutures have been noted in medial portions of the mandible and sutures associated with compression mainly in posterior portions, i.e., in the angular and prearticular. The variability of suture types along the mandible suggests a complex loading regime of compression and tension. Sutures associated with tension and a flexible symphysis potentially allowed an increase of oral volume during gape opening, whereas sutures associated with compression represent adaptations for strong bite forces.ResumenSe ha examinado la morfología de las suturas mandibulares del temnospóndilo del Triásico Superior Metoposaurus krasiejowensis para determinar su papel en la biomecánica mandibular. Hasta la fecha, no se han realizado estudios histológicos de las suturas mandibulares de vertebrados fósiles, en contraste con los estudios histológicos en suturas craneales. Como consecuencia, las interpretaciones sobre las suturas mandibulares están aquí basadas en la comparación con estudios previos en suturas craneales y con análisis 3D de elementos finitos para esta misma especie. En total 32 laminas delgadas estándares fueron estudiadas con observaciones de microscopio petrográfico con el fin de diferenciar la morfología de las suturas mandibulares. Cinco tipos de suturas mandibulares son presentes en este taxón: interdigitales, levemente interdigitales, superposición, lengua, ranura y lindante. En base a estudios previos, se ha asumido generalmente que las suturas levemente interdigitales, lengua, ranura y lindantes se asocian con cargas de tensión, mientras que las de tipo interdigitales se asocian con compresión y el tipo sutural de superposición con distintas cargas de absorción y neutralización. Las suturas asociadas con tensión ocurren mayormente en la parte anterior de la mandíbula, principalmente en el dentario; las suturas de superposición se han encontrado las porciones mediales de la mandíbula y las suturas asociadas con compresión se han encontrado mayormente en las porciones posteriores, por ejemplo, en el angular y el prearticular. La variabilidad de los tipos suturales a lo largo de la mandíbula sugiere un complejo régimen de cargas de compresión y tensión. Suturas asociadas con tensión y una sínfisis flexible potencialmente permitieron un incremento del volumen oral durante la abertura bucal, mientras que las suturas asociadas con compresión representan adaptaciones a fuertes fuerzas de mordida.