The discrepancy between morphological and microanatomical patterns of anamniotic stegocephalian postcrania from the Early Permian Briar Creek Bonebed (Texas)

Abstract

a b s t r a c tThe histological framework of thirteen Early Permian tetrapod long bones from a single locality, the Briar Creek Bonebed in Archer County, Texas, USA, is described from a series of transverse sections through the midshafts. The bones were morphologically categorized and belong to one of three taxa: Eryops, Archeria, and Diadectes. However, five histotypes are recognized. The first category includes the juvenile bone. The second histotype is characterized by the presence of radial vascular canals. The third histotype is characterized by the numerous longitudinal canals arranged in regular rows. In the fourth histotype, there is strong remodeling in the deep part of the cortex, creating a distinct border with the external layer of lamellar bone. In the fifth histotype, the deep part of the cortex is progressively remodeled towards osteoporosis with distinct layers of large circumferentially arranged erosion cavities. For femora and humeri, histotypes match morphology. Histotype II is characteristic for Diadectes propodials, histotype III is characteristic for Eryops propodials, and histotype IV is characteristic for Archeria propodials. A discrepancy between morphology and histology is observed in the ulnae, fibula and radius. This discrepancy may be explained by interspecific or intraspecific variability.

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

“…However, in one bone the increase of bone mass was observed through secondary deposition and cortex compactness increase; in second bone the opposite process was observed-the cortex was highly eroded. It was not possible to determine if this variation has interspecific or intraspecific origin (Konietzko-Meier et al 2016). In the light of the results obtained here based on the Metoposaurus humeri, it is possible that the bimodal growth pattern of long bones is a character typical for Temnospondyli and represent the sexual dimorphism.…”

“…The discrepancy between the morphological and microstructural characters in temnospondyls was first observed for Eryops (Konietzko-Meier et al 2016). Among other bones from the Early Permian Briar Creek Bonebed (Texas), three ulnae were studied.…”

Bone histology of varanopids (Synapsida) from Richards Spur, Oklahoma, sheds light on growth patterns and lifestyle in early terrestrial colonizers

“…From a palaeoecological perspective, the diverse assemblage of Richards Spur also offers a window into the growth rhythms of Permian amniotes living at approximately palaeoequatorial latitudes, and, by extension, potential environmental impacts on their life histories. Histological data have been applied widely to other palaeoecological systems, including the Permian-aged Briar Creek assemblage [64] and the Beaufort Group assemblages of the Karoo Basin [65], as well as dinosaur assemblages of Inner Mongolia [66] and the Hell Creek Formation in Montana [67], to name a few. Peabody [68] offered the first survey of cyclic growth mark formation in Richards Spur vertebrates, recognizing at least two or three zones in different skeletal elements attributed to Captorhinus.…”

Postcranial anatomy and histology ofSeymouria, and the terrestriality of seymouriamorphs

“…It may relate to overall body size, as extant lissamphibians, relatively small in comparison to Seymouria, typically lack medullary spongiosa; however, the larger cryptobranchids possess a spongiosa (e.g., Laurin, Canoville & Germain, 2011). Similarly, small, semi-terrestrial to terrestrial temnospondyls also have little to no spongiosa (e.g., McHugh, 2015) compared to the larger Eryops with a much denser spongiosa (e.g., Konietzko-Meier, Shelton & Sander, 2016).…”

“…Comparisons with other Paleozoic tetrapods are also limited by a paucity of comparative work. Of the major Paleozoic clades (e.g., pelycosaurian synapsids, 'lepospondyls'), temnospondyls are the best-sampled (Sanchez et al, 2010a;Sanchez et al, 2010b;McHugh, 2014;Konietzko-Meier, Shelton & Sander, 2016). The relative thickness of the cortex and the development of the medullary spongiosa are most comparable to that of the co-occurring trematopid Acheloma dunni, a terrestrial taxon (Sanchez et al, 2010b;Quemeneur, de Buffrénil & Laurin, 2013).…”