Saurosuchus

Posterior view of the mount in the Ischigualasto Provincial Park

The holotype, PVL 206, was discovered by Galileo J. Scaglia and Leocadio Soria in 1957, lying in a greenish sandstone on the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina. It consists of a nearly complete, but deformed skull. Saurosuchus was formally described and named later in 1959 by Osvaldo. A. Reig. The generic name, Saurosuchus, is derived from the Greek σαῦρος (sauros, meaning lizard) and σοῦχος (souchus, meaning crocodile). The specific name, galilei, is in honour to Galileo J. Scaglia, who unearthed and prepared the holotype.[1]

Life restoration of S. galilei

Initially, Saurosuchus was estimated at 5.5 m (18 ft) long[1] with a weight over 250 kg (550 lb).[7] This would make it one of the largest "Rauisuchian", after the enormous Fasolasuchus. Two rows are on either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it.[2][4] It has a deep, laterally compressed skull. The teeth are large, recurved, and serrated. The skull is wide at its back and narrows in front of the eyes. The skull roof and maxilla are somewhat pitted.[3]

Pitting is also seen in aquatic phytosaurs and crocodilians, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The frontal bones, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in more evolved rauisuchians, a small rod projects down from the lacrimal bone in front of the eye, but it does not attach firmly to the jugal bone below it. Ridges along the upper surface of the supraoccipital bone at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck.[3][4]

Saurosuchus was considered a member of the Rauisuchia, although now it is considered part of the more basal Loricata, a clade comprising both Rauisuchia and the true crocodylians. Below is the cladogram of the Loricata conducted by Nesbitt 2011:[8]

Analysis of Saurosuchus' bite indicated that its jaws were relatively weak, as determined in a study by Bestwick et al., in 2023. The bite strength was determined to be most similar to the modern gharial in regards to strength, or around 1,015-1,885 newtons due to its relatively thinner bones compared to those of the theropod dinosaurs that would later supplant it, suggesting that Saurosuchus would feed largely on softer food such as flesh and vital organs from its prey, which it would process with its rear teeth. This avoidance of bone also would have left more meat for scavengers to feed on after Saurosuchus had finished with a meal.[9][10]

A reconstruction of the cranial endocast revealed poorly developed flocculus and optic lobes, and an anteroposteriorly short lateral semicircular canal, suggesting that Saurosuchus would have relied on smell instead of eyesight to track prey. Furthermore, the lagena is relatively long, suggesting a broad hearing sensitivity, especially in low-frequency sounds.[11]

Saurosuchus hunting a group of Hyperodapedon

Saurosuchus was unearthed in the Cancha de Bochas Member from the Ischigualasto Formation, being the major predator on its environment.[3] The Ischigualasto Formation was dominated by fluvial and floodplain environments with strongly seasonal rainfalls. Interlayered volcanic ash layers above the base and below the top of the formation provide chronostratigraphic control and have yielded ages of 231.4 ± 0.3 Ma and 227 ± 0.9 Ma respectively.[12]

• Rauisuchia
• 1959 in paleontology
• Pseudosuchia
• Crurotarsi

Wikimedia Commons has media related to Saurosuchus.

• Saurosuchus galilei at DigiMorph
• Saurosuchus at Paleofile.com (archived copy)
• ICS 2018 Timescale