Stenaulorhynchus

Dentition The teeth of Stenaulorhynchus were conical, pointed, and composed mostly of dentine, although new unworn teeth may have had a thin layer of enamel. They were set deeply into and fused with the jaw bones. Their postorbital The occipital condyles are significantly anterior to the quadrates and the quadrate and articular fit tightly together to form a jaw joint that wouldn't have allowed for much rotation. They are also known for their beak, formed at the front of their upper and lower jaws. Postcranial The dorsal vertebrae have a centrum that is taller than it is wide and slightly amphicoelous in shape. The parapophyses and prezygapophyses are distinct that have articular surfaces about 30 degrees above horizontal. The caudal vertebrae have tall neural spines and the second cervical rib has a backwards pointing spine. Their ischium fans out towards the rear of the animal. The humerus is robust. At the proximal end, the shaft is bent backwards and expanded along the coronal plane. The distal humerus has a flat posterior surface and a curved ectepicondylar groove. The radius and ulna are the same length. The femur is circular in cross-section and, as with the humerus, the proximal end is bent backwards. Both ends of the femur are expanded and the proximal end has no neck and a prominent greater trochanter. The distal end has thickened condyles with a groove on the lateral side. == Paleobiology ==

Microscopic analysis of thin-sections of bone have shown that Stenaulorhynchus had a determinant growth pattern, reaching 2/3 of their adult size within one year. Older teeth would wear down with use and be resorbed where they contacted other teeth. Stenaulorhynchus may have been adapted for scratch-digging. == Discovery ==

The fossils were collected in 1930 by the British geologist G. M. Stockley during a survey commissioned by the Tanganyika Geological Survey Department. The goal was to better understand the "economic possibilities" of the Ruhaha Basin within Tanganyika Territory. He primarily collected fossils that had weathered out of the rock on the surface. The specimens weren't all correctly labeled since bones from different localities fit together. More surprisingly, a coprolite was mislabeled as a maxillary fragment. Haughton also described a species which he named Stenaulorhynchus major, which he said differed primarily in size, based on a distal left and right humerus fragments. Those specimens were later identified as Stagonosuchus nyassicus, a suchian archosaur from the same locality and horizon. == Classification ==

Stenaulorhynchus shares characteristics with other early rhynchosaurs, including their ankylothecodont dentition (teeth within deep sockets and fused to the bone) and precision-shear bite. One of the differences between them is that Stenaulorhynchus had smaller maxillary teeth with a larger gap between the tooth rows. Stenaulorhynchus has also been labeled as a sister-taxa to the Brazilian genus Brasinorhynchus which also has three or more tooth rows medial to the main maxillary groove but lacks the centrum contribution to the parapophyses and diaphophyses. == Geology ==

Stenaulorhynchus is found in the Upper Bone Bed in the Njalili locality, part of the Lifua Member of the Manda Formation. It is composed of proximal floodplain paleosol deposits. Articulated specimens of Stenaulorhynchus have been found, suggesting that they may have mummified before burial. The surface of the bed has been exposed by tributaries eroding away the rock. During the Triassic, the floodplain would have been covered by springs and ponds. Rises in precipitation and mean annual temperature may have led to an increase in perennial vegetation, as well. == References ==