Dynamosuchus

Like other ornithosuchids, the snout of Dynamosuchus had a hooked premaxilla with three teeth, followed by a gap (a diastema) and a deep maxilla with six to eight teeth. The maxilla was similar to that of Ornithosuchus due to possessing pitting on its outer surface (absent in Venaticosuchus and Riojasuchus) and a not particularly deep antorbital fossa (unlike Riojasuchus). Preserved skull bones generally reconstruct a skull with small orbits and temporal fenestration like Riojasuchus, but the squamosal is not as thick as in that taxon. The quadratojugal bone was roughly textured and L-shaped, not as acute in angle as Riojasuchus. A hole known as a quadrate foramen separates the quadratojugal from the quadrate, and an additional smaller hole on the quadrate opens up into the quadrate foramen. The additional hole is an autapomorphy (unique characteristic) of Dynamosuchus absent in other ornithosuchids.[1]

The parabasisphenoid bone at the bottom of the braincase has a semilunar depression like that of Venaticosuchus, but the gap between its basipterygoid processes and basitubera is less acute than in that taxon. Dynamosuchus's basipterygoid processes are also more closely spaced and pointed further rearwards compared to Venaticosuchus. The surangular is similar to that of Riojasuchus, with a pronounced blade-like crest on its outer surface and a large hole (a surangular foramen) at the rear of the jaw. The jaw as a whole deepens towards the chin and has a long mandibular fenestra.[1]

Postcranial material

The cervical (neck) vertebrae have a variety of features shared with various pseudosuchians, such as pits below the postzygapophyses (rear connecting plates), expanded neural spines, and a strong keel on the underside. Dorsal vertebrae near the shoulder have a pair of centrodiapophyseal laminae, buttress-like crests connecting the diapophyses (rib facets) to the centrum (spool-shaped lower portion of each vertebra). These crests are shared with Ornithosuchus but absent in Riojasuchus and unknown in Venaticosuchus. In most other respects, the dorsal vertebrae of Dynamosuchus are more similar to Riojasuchus than Ornithosuchus. For example, Dynamosuchus lacks prezygodiapophyseal and postzygodiapophyseal laminae. These crests, present in Ornithosuchus, connect the diapophyses to the zygapophyses (vertebral connecting plates).[1]

Dynamosuchus's osteoderms are set in two rows along the back, are somewhat square-shaped, and are densely textured by radiating ridges and grooves. Osteoderms at the front of the body often have a sideways-oriented peak-like projection. The forelimb bones are thick and generally strongly built. The radius expands towards the wrist moreso than Ornithosuchus, while the humeral head is not as developed as that of Riojasuchus. The hip has an overall shape like that of Ornithosuchus, with a smooth and straight upper portion of the ilium, a long pubis, and three sacral vertebrae. Like other ornithosuchids, the hindlimb bones are large and have prominent and/or unusual muscle scars. These include an anterior trochanter at the top of the femur, and a knob-like scar for the iliofibularis muscle on the shaft of the fibula. The iliofibularis attachment is located about 1/3rd down the shaft of the fibula in Dynamosuchus, while it is about halfway down in Riojasuchus.[1]