Teyumbaita sulcognathus Montefeltro, Langer, and Schultz, 2010

Veiga, Fábio Hiratsuka, Soares, Marina Bento & Sayão, Juliana Manso, 2015, Osteohistology of hyperodapedontine rhynchosaurs from the Upper Triassic of Southern Brazil, Acta Palaeontologica Polonica 60 (4), pp. 829-836 : 830-832

publication ID	https://doi.org/ 10.4202/app.00074.2014
persistent identifier	https://treatment.plazi.org/id/03B73024-FFDC-FF9A-6E5E-FB3DFA26C6CE
treatment provided by	Felipe
scientific name	Teyumbaita sulcognathus Montefeltro, Langer, and Schultz, 2010
status

Treatment

Fig. 1A–C View Fig .

Material.— UFRGS-PV-0298- T, radius; UFRGS-PV-0298- T, rib; UFRGS-PV-0298- T, humerus; UFRGS-PV-0232- T; UFRGS-PV-0290- T, tibia; from the type locality .

Description.— Radius (UFRGS-PV-0298-T): The radius shaft ( Fig. 1A 1 View Fig ) has a large medullary cavity surrounded by a narrow cortex. Secondary remodeling in the perimedullary region is extensive, as recorded by large resorption cavities. In the innermost cortex, the vascular canals are arranged mostly as longitudinally oriented primary osteons with a decrease in density toward the periphery. The cortex is formed by parallel-fibred complex. Highly organized flattened osteocyte lacunae, parallel to one another, occur mainly in the mid- and the outer cortex. Growth marks are absent.

Rib (UFRGS-PV-0298-T): The rib ( Fig. 1A View Fig 2 View Fig ) microstructure is similar to that of the radius. Longitudinal primary osteons are extensive and concentrated in the perimedullary region (secondary osteons are also present). The osteocyte lacunae are more globular in shape and mostly arranged haphazardly in the innermost cortex, around the primary osteons. Toward the periphery, the primary osteons are sparser and the osteocyte lacunae tend to be more organized, forming a parallel-fibred bone tissue. Canaliculi are extensive and radiate out in all directions from the osteocyte lacunae. A very thin avascular layer at the periosteal surface suggests the presence of an EFS, with one internal LAG. The presence of an EFS (see Cormack 1987) at the outer surface of the cortex indicates that the growth of UFRGSPV-0298-T slowed in comparison to that of earlier stages and that the specimen had reached somatic maturity.

Humerus (UFRGS-PV-0298-T): The humerus ( Fig. 1A View Fig 3 View Fig ) was sectioned near its the proximal end. The secondary remodeling in the perimedullary region is extensive with enlarged resorption cavities. The cortex is highly vascularized and varies from a mixture of longitudinal and circular-oriented primary osteons (in its innermost portion) to longitudinal primary osteons organized in circular rows (in the outer cortex). The primary bone tissue comprises lamellar-zonal bone with organized osteocyte lacunae arranged parallel to one another. Canaliculi are not preserved. Two to three annuli occur in the cortex, and are more concentrated in the outer cortex. An EFS is also present at the periosteal surface of the cortex, confirming somatic maturity.

Tibia (UFRGS-PV-0232-T): Transverse sections of the tibia ( Fig. 1B View Fig ) reveal secondary remodeling in the perimedullary region, with the formation of large resorption cavities and the presence of primary and secondary osteons. In the innermost cortex, the vascular canals are organized in a plexiform pattern, with osteocyte lacunae distributed haphazardly around the primary osteons, indicating the presence of fibrolamellar bone tissue. The same vascularization pattern remains toward the periphery; but the primary bone tissue changes to a parallel-fibred pattern, where the osteocyte lacunae are highly organized and lie parallel to one another. Three growth marks are present near the periosteal surface.

UFRGS-PV-0290-T: The secondary remodeling ( Fig. 1C View Fig ) is extensive with enlarged resorption cavities in the perimedullary region, extending across the cortex. The cortex is highly vascularized in the innermost region and tends to become more avascular in the periosteal area, formed by primary and secondary osteons organized in a sub-plexiform pattern. Osteocyte lacunae are abundant, globular and arranged haphazardly around the vascular canals in the innermost cortex, becoming more organized toward the outer cortex. This organization indicates fibrolamellar bone tissue in the perimedullary region, which becomes parallel-fibred tissue periosteally. Three growth marks are present in the cortex, but are more concentrated in the outer cortex.

Stratigraphic and geographic range.— Hyperodapedon Assemblage Zone (AZ) , Santa Maria Supersequence, Santa Maria 2 Sequence (Upper Triassic) of Rio Grande do Sul, Brazil.