Baurusuchidae

Baurusuchidae is a family of land-dwelling, hypercarnivorous crocodilians that existed during the Late Cretaceous. Their fossils have been found across the ancient southern supercontinent of Gondwana, specifically in South America (Argentina and Brazil) and Asia (Pakistan). Under the rules of the PhyloCode, the family is officially defined as the smallest clade that includes *Cynodontosuchus rothi*, *Pissarrachampsa sera*, and *Baurusuchus pachecoi*. These animals are grouped within the suborder Baurusuchia, and researchers have proposed two subfamilies: Baurusuchinae and Pissarrachampsinae.

The first genus named in the family was *Baurusuchus*, which also gives the group its name. Its remains come from the Late Cretaceous Bauru Group in Brazil, dating to the Turonian–Santonian stages. Besides *Baurusuchus*, five other South American crocodyliforms have been placed in Baurusuchidae: *Campinasuchus*, *Cynodontosuchus*, *Pissarrachampsa*, *Stratiotosuchus*, and *Wargosuchus*. *Cynodontosuchus* was the first baurusuchid ever described, named in 1896 by English paleontologist Arthur Smith Woodward, though it was only recently recognized as part of this family. *Wargosuchus* was described in 2008. Both *Cynodontosuchus* and *Wargosuchus* are known only from fragmentary fossils, and both come from the Santonian of Argentina. *Stratiotosuchus* was assigned to Baurusuchidae in 2001. The youngest genus once thought to belong to the family is *Pabwehshi*, from the Maastrichtian of Pakistan, named in 2001, but it has since been reclassified as a basal member of Sebecia. A new genus, *Campinasuchus*, was added in May 2011, based on fossils from the Turonian–Santonian Adamantina Formation of the Bauru Basin in Brazil. Shortly after, *Pissarrachampsa* was named from the Campanian–Maastrichtian Vale do Rio do Peixe Formation, also in the Bauru Basin.

The family Baurusuchidae was first named by Brazilian paleontologist Llewellyn Ivor Price in 1945, with *Baurusuchus* as its core. In 1946, American paleontologist Edwin Harris Colbert created the group Sebecosuchia, which united Baurusuchidae with the family Sebecidae (represented by the genus *Sebecus*). Both *Baurusuchus* and *Sebecus* share deep snouts and ziphodont teeth—serrated and flattened from side to side. Later discoveries of similar-looking forms, such as *Cynodontosuchus*, *Stratiotosuchus*, and *Wargosuchus*, led to a set of common features used to link these groups: a deep snout, ziphodont teeth, a curved tooth row, an enlarged canine-like tooth in the lower jaw that fits into a deep notch in the upper jaw, and a groove on the lower jaw.

For decades, many phylogenetic studies supported a close relationship between baurusuchids and sebecids. Both families are early members of the clade Metasuchia, which includes the subgroups Notosuchia (mostly land-dwelling crocodyliforms) and Neosuchia (larger, often semiaquatic crocodyliforms, including modern crocodilians). Several analyses found that sebecosuchians—including baurusuchids and sebecids—were closely related to notosuchians. Later, the genera *Iberosuchus* and *Eremosuchus* were also assigned to Baurusuchidae, and phylogenetic studies continued to show a close link between Baurusuchidae and Sebecidae. Both families were grouped with notosuchians in the larger clade Ziphosuchia, which includes all ziphodont crocodyliforms. More recently, sebecosuchians—baurusuchids included—have been placed within Notosuchia as derived members of that group. A cladogram from Ortega et al. (2000) shows baurusuchids inside Notosuchia.

In 2004, the superfamily Baurusuchoidea was established to include both baurusuchids and sebecids. Phylogenetically, Baurusuchoidea was defined as the most recent common ancestor of *Baurusuchus* and *Sebecus* and all its descendants, while Baurusuchidae was defined as the most recent common ancestor of *Baurusuchus* and *Stratiotosuchus* and all its descendants. A 2005 analysis found Sebecidae to be paraphyletic—a grouping that includes some but not all descendants of a common ancestor. In that view, sebecids formed a collection of basal sebecosuchians, while baurusuchids remained a valid group of derived sebecosuchians. A cladogram from Turner and Calvo (2005) illustrates this.

Later studies pointed out many features that distinguish baurusuchids from sebecosuchids. Sebecosuchids were often considered more closely related to Neosuchia (which includes modern crocodilians), while baurusuchids were thought to be a more distantly related clade. In a 1999 analysis, *Baurusuchus* formed a clade with notosuchians, to the exclusion of other ziphosuchians. This placement has been supported by more recent studies, which place *Baurusuchus* within Notosuchia.

In 2007, a new clade called Sebecia was erected, including sebecids and peirosaurids. Peirosauridae, a family of small land-dwelling crocodyliforms, had often been placed in or near Neosuchia in earlier work. Assigning sebecids to Sebecia moved them closer to Neosuchia than to Notosuchia. In that study, baurusuchids were split: *Baurusuchus* was placed as a more basal metasuchian, while the remaining baurusuchids (*Bretesuchus* and *Pabwehshi*) were placed as sebecians, making Baurusuchidae paraphyletic. A cladogram from Larsson and Sues (2007) shows this arrangement.

More recent studies have placed *Baurusuchus* deep within Notosuchia, much as the larger group Sebecosuchia once was, while other sebecosuchian genera have been placed more distantly in Metasuchia. A new baurusuchid, *Pissarrachampsa*, was named in 2011, and a comprehensive phylogenetic analysis of baurusuchids was conducted alongside its description. Montefeltro et al. (2011) found Baurusuchidae to be a monophyletic group containing the genera *Baurusuchus*, *Cynodontosuchus*, and others.