Baurusuchidae
Encyclopedia
Baurusuchidae is a Gondwana
n family
of mesoeucrocodylia
ns that lived during the Late Cretaceous
. It is a group of terrestrial hypercarnivorous crocodilians from South America
(Argentina
and Brazil
) and possibly Pakistan
. Baurusuchidae has been defined as a clade
containing the most recent common ancestor of Baurusuchus
and Stratiotosuchus
and all of its descendants. It may, however, be polyphyletic, as recent phylogenetic analyses have placed Baurusuchus
within Notosuchia
and other baurusuchids within the more distantly related clade Sebecia
. A recent study of the family finds it monophyletic by including the South American genera Baurusuchus, Cynodontosuchus
, Pissarrachampsa
, Stratiotosuchus
, and Wargosuchus
. Other traditional baurusuchids like Pabwehshi
are excluded. The recently named Campinasuchus
is also included in the family. Baurusuchids have been placed in the suborder Baurusuchia, and two subfamilies have been proposed: Baurusuchinae
and Pissarrachampsinae
.
Bauru Group
of Brazil
in deposits that are Turonian
- Santonian
in age. In addition to Baurusuchus, five other South American crocodyliforms have been assigned to Baurusuchidae: Campinasuchus
, Cynodontosuchus
, Pissarrachampsa
, Stratiotosuchus
, and Wargosuchus
. Cynodontosuchus was the first known baurusuchid, named in 1896 by English
paleontologist Arthur Smith Woodward
, although it was only recently assigned to Baurusuchidae. Wargosuchus was described in 2008. Cynodontosuchus and Wargosuchus are known only from fragmentary remains. Both genera are from the Santonian of Argentina
.
A fourth genus, Stratiotosuchus, was assigned to Baurusuchidae in 2001. Fossils have been found from the Turonian
- Santonian
of Brazil. Pabwehshi is the youngest genus that has been assigned to Baurusuchidae, and is from the Maastrichtian
of Pakistan
. It was named in 2001 but has since been reassigned as a basal member of Sebecia
.
A new genus, Campinasuchus, was assigned to the family in May, 2011. It is known from the Turonian-Santonian Adamantina Formation
of the Bauru Basin of Brazil. Soon after, the new genus Pissarrachampsa was named from the Campanian–Maastrichtian Vale do Rio do Peixe Formation, also in the Bauru Basin.
ian paleontologist Llewellyn Ivor Price
in 1945 to include Baurusuchus. In 1946, American
paleontologist Edwin Harris Colbert
erected the group Sebecosuchia
, which united Baurusuchidae with the family Sebecidae
(represented by the genus Sebecus
). Both Baurusuchus and Sebecus have deep snouts and ziphodont dentitions (teeth that are serrated and laterally compressed). Other forms were later found that had a close appearance to these two genera, among them Cynodontosuchus
, Stratiotosuchus
, and Wargosuchus
. Several features were used to unite these groups: a deep snout, a ziphodont dentition, a curved tooth row, an enlarged canine-like dentary tooth that fits into a deep notch in the upper jaw, and a groove on the lower jaw.
Many phylogenetic analyses within the past decades have supported a close relationship between the two families. Baurusuchids and sebecosuchids are both early members of the clade
Metasuchia
, which includes the subgroups Notosuchia
(mainly terrestrial crocodyliforms) and Neosuchia
(larger, often semiaquatic crocodyliforms, including living crocodylians). Sebecosuchians, which include both baurusuchids and sebecosuchids, were found to be closely related to notosuchians in several studies. The new genera Iberosuchus
and Eremosuchus
were later assigned to Baurusuchidae, and phylogenetic analyses encompassing these taxa continued to find Baurusuchidae to be closely related to Sebecidae. Both families were allied with notosuchians in the larger group Ziphosuchia
, composed of ziphodont crocodyliforms. More recently, sebecosuchians - including baurusuchids - have been placed within Notosuchia as derived
members of the clade. Below is a modified cladogram from Ortega et al. (2000) placing baurusuchids within Notosuchia:
In 2004, the superfamily Baurusuchoidea was established to include baurusuchids and sebecids. Phylogenetically, Baurusuchoidea was defined as the most recent common ancestor
of Baurusuchus and Sebecus and all of its descendants while Baurusuchidae was defined as the most recent common ancestor of Baurusuchus and Stratiotosuchus
and all of its descendants.
In a 2005 analysis, Sebecidae was found to be a paraphyletic grouping, or a grouping that includes some descendants of a common ancestor but not all. Sebecids formed an assemblage of basal
sebecosuchians, while baurusuchids remained a valid grouping of derived sebecosuchians. Below is a modified cladogram
from Turner and Calvo (2005):
Later studies noted many features that distinguished baurusuchids from sebecosuchids. Sebecosuchids were often considered to be more closely related to Neosuchia
, a group that includes modern crocodylians, while baurusuchids were thought to be a more distantly related clade. In a 1999 phylogenetic analysis, Baurusuchus formed a clade with notosuchians to the exclusion of other ziphosuchians. This placement has been upheld by recent analyses, which place Baurusuchus within Notosuchia.
In 2007, a new clade called Sebecia
was erected. Sebecia included sebecids and peirosaurids
. Peirosauridae, a family of small terrestrial crocodyliforms, had often been placed in or near Neosuchia in previous studies. The assignment of sebecids to Sebecia placed the family closer to Neosuchia than Notosuchia. In this study, baurusuchids were split up, with Baurusuchus placed as a more basal metasuchian and the remaining baurusuchids (Bretesuchus and Pabwehshi
) placed as sebecians. Therefore, the family Baurusuchidae was paraphyletic. Below is a modified cladogram from Larsson and Sues (2007):
More recent studies have nested Baurusuchus deep within Notosuchia, just as the larger group Sebecosuchia once was, while the remaining sebecosuchian genera have been placed more distantly in Metasuchia. A new baurusuchid called Pissarrachampsa
was named in 2011, and a comprehensive phylogenetic analysis of baurusuchids was conducted along with its description. Montefeltro et al. (2011) found Baurusuchidae to be a monophyletic group with the genera Baurusuchus, Cynodontosuchus, Pissarrachampsa, Stratiotosuchus, and Wargosuchus. They adopted the name Baurusuchia in a phylogenetic sense to distinguish baurusuchids from related crocodyliforms. Baurusuchia was first erected as an infraorder in 1968, but in the 2011 analysis it was found to be in an identical position to Baurusuchidae in the final tree. The only difference between Baurusuchidae and Baurusuchia is that the former is a node-based taxon and the latter is a stem-based taxon. Baurusuchidae is defined as the least inclusive clade containing Baurusuchus, Cynodontosuchus, Pissarrachampsa, Stratiotosuchus, and Wargosuchus. As in all node-based clades, there is a most recent common ancestor
; these genera are all of its known descendants. Baurusuchia is defined as Baurusuchus pricei and all Crocodyliformes that share a more recent common ancestor with B. pricei than with Notosuchus terrestris, Mariliasuchus amarali, Armadillosuchus arrudai, Araripesuchus gomesi, Sebecus icaeorhinus, Bretesuchus bonapartei, Peirosaurus tormini, or Crocodylus niloticus.
In contrast to the node-based Baurusuchidae, the stem-based Baurusuchia does not include a common ancestor and all its descendants, but rather all forms more closely related to a specific baurusuchid than a non-baurusuchid. As a stem-based taxon, Baurusuchia is more inclusive than Baurusuchidae; a new taxon could potentially be placed outside Baurusuchidae because it is not a descendant of the most recent common ancestor of baurusuchids, but would still be a baurusuchian because it is more closely related to baurusuchids than it is to other crocodyliforms. For now, however, Baurusuchidae and Baurusuchia are essentially identical in scope.
Montefeltro et al. (2011) also divided Baurusuchidae into two subfamilies, Pissarrachampsinae
and Baurusuchinae
. Pissarrachampsinae includes Pissarrachampsa and Wargosuchus while Baurusuchinae includes Stratiotosuchus and Baurusuchus. Cynodontosuchus is not a member of either of these subfamilies, but the most basal
baurusuchid. Many of the unique features that separate Cynodontosuchus may also be associated with a juvenile individual. The material that Cynodontosuchus is based on has been suggested to be a juvenile form of Baurusuchus, and the two taxa may be synonymous.
Below is a cladogram from Montefeltro et al. (2011):
A sixth genus of baurusuchid, Campinasuchus
, was named just a few months before Pissarrachampsa, and was not included in the analysis.
of Brazil
that may have been laid by a baurusuchid, most probably Baurusuchus. A new oospecies called Bauruoolithus fragilis
was named on the basis of these remains. The eggs are about twice as long as they are wide and have blunt ends. At about a quarter of a millimeter in thickness, the shells are relatively thin. Some eggs may have already hatched by the time they were buried, but none show extensive degradation. In living crocodilians (the closest living relatives of baurusuchids), eggs undergo extrinsic degradation to allow hatchlings to easily break through their shells. The fossils indicate that baurusuchid hatchlings probably broke through thin egg shells rather than shells that had been degraded over their incubation period.
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
n family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of mesoeucrocodylia
Mesoeucrocodylia
Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
ns that lived during the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
. It is a group of terrestrial hypercarnivorous crocodilians from South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
(Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
) and possibly Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
. Baurusuchidae has been defined as a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
containing the most recent common ancestor of Baurusuchus
Baurusuchus
Baurusuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil. It was a terrestrial predator and scavenger, about 3.5 to 4 meters long. Baurusuchus lived during the Turonian to Santonian stages of the Late Cretaceous Period, in Adamantina Formation, Brazil...
and Stratiotosuchus
Stratiotosuchus
Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Adamantina Formation, Brazil during the late Cretaceous period . It was first named by Campos, D.A., Suarez, J.M., Riff, D. and Kellner, A.W.A. in 2001 and the type species is Stratiotosuchus maxhechti...
and all of its descendants. It may, however, be polyphyletic, as recent phylogenetic analyses have placed Baurusuchus
Baurusuchus
Baurusuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil. It was a terrestrial predator and scavenger, about 3.5 to 4 meters long. Baurusuchus lived during the Turonian to Santonian stages of the Late Cretaceous Period, in Adamantina Formation, Brazil...
within Notosuchia
Notosuchia
Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Cretaceous. Fossils have been found from South America, Africa, and Asia...
and other baurusuchids within the more distantly related clade Sebecia
Sebecia
Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include Hamadasuchus, Peirosauridae, and Sebecus. It was initially considered to be the sister taxon of the clade Neosuchia, which includes living...
. A recent study of the family finds it monophyletic by including the South American genera Baurusuchus, Cynodontosuchus
Cynodontosuchus
Cynodontosuchus is an extinct genus of baurusuchid mesoeucrocodylian. Fossils have been found from Argentina of Late Cretaceous age from the Bajo de la Carpa Formation as well as the Pichi Picun Leufu Formation...
, Pissarrachampsa
Pissarrachampsa
Pissarrachampsa is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil...
, Stratiotosuchus
Stratiotosuchus
Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Adamantina Formation, Brazil during the late Cretaceous period . It was first named by Campos, D.A., Suarez, J.M., Riff, D. and Kellner, A.W.A. in 2001 and the type species is Stratiotosuchus maxhechti...
, and Wargosuchus
Wargosuchus
Wargosuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Argentina...
. Other traditional baurusuchids like Pabwehshi
Pabwehshi
Pabwehshi is an extinct genus of mesoeucrocodylian. It is based on GSP-UM 2000, a partial snout and corresponding lower jaw elements, with another snout assigned to it...
are excluded. The recently named Campinasuchus
Campinasuchus
Campinasuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Minas Gerais State, Brazil during the late Cretaceous period . It is known from four partial skulls from the Honorópolis District of the Adamantina Formation, Bauru Basin. The specimens were collected at Três...
is also included in the family. Baurusuchids have been placed in the suborder Baurusuchia, and two subfamilies have been proposed: Baurusuchinae
Baurusuchinae
Baurusuchinae is a subfamily of baurusuchid crocodyliforms from the Late Cretaceous of Brazil. Named in 2011, it contains the baurusuchids Baurusuchus and Stratiotosuchus. Baurusuchinae is one of two subfamilies of Baurusuchidae, the other being Pissarrachampsinae.Several features distinguish...
and Pissarrachampsinae
Pissarrachampsinae
Pissarrachampsinae is a subfamily of baurusuchid crocodyliforms from the Late Cretaceous of Brazil and Argentina. It was named in 2011 with the description of Pissarrachampsa sera and includes P. sera from Brazil and the related Wargosuchus australis from Argentina...
.
Genera
Several genera have been assigned to Baurusuchidae. Baurusuchus was the first, being the namesake of the family. Remains of Baurusuchus have been found from the Late CretaceousLate Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Bauru Group
Bauru Group
The Bauru Group is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation. The Bauru Group was divided by Fernandes and Coimbra in four formations,namely Adamantina, Uberaba Araçatuba and...
of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in deposits that are Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
- Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
in age. In addition to Baurusuchus, five other South American crocodyliforms have been assigned to Baurusuchidae: Campinasuchus
Campinasuchus
Campinasuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Minas Gerais State, Brazil during the late Cretaceous period . It is known from four partial skulls from the Honorópolis District of the Adamantina Formation, Bauru Basin. The specimens were collected at Três...
, Cynodontosuchus
Cynodontosuchus
Cynodontosuchus is an extinct genus of baurusuchid mesoeucrocodylian. Fossils have been found from Argentina of Late Cretaceous age from the Bajo de la Carpa Formation as well as the Pichi Picun Leufu Formation...
, Pissarrachampsa
Pissarrachampsa
Pissarrachampsa is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil...
, Stratiotosuchus
Stratiotosuchus
Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Adamantina Formation, Brazil during the late Cretaceous period . It was first named by Campos, D.A., Suarez, J.M., Riff, D. and Kellner, A.W.A. in 2001 and the type species is Stratiotosuchus maxhechti...
, and Wargosuchus
Wargosuchus
Wargosuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Argentina...
. Cynodontosuchus was the first known baurusuchid, named in 1896 by English
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
paleontologist Arthur Smith Woodward
Arthur Smith Woodward
Sir Arthur Smith Woodward was an English palaeontologist.-Biography:Woodward was born in Macclesfield, Cheshire, England and was educated there and at Owens College, Manchester. He joined the staff of the Department of Geology at the Natural History Museum in 1882. He became assistant Keeper of...
, although it was only recently assigned to Baurusuchidae. Wargosuchus was described in 2008. Cynodontosuchus and Wargosuchus are known only from fragmentary remains. Both genera are from the Santonian of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
A fourth genus, Stratiotosuchus, was assigned to Baurusuchidae in 2001. Fossils have been found from the Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
- Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...
of Brazil. Pabwehshi is the youngest genus that has been assigned to Baurusuchidae, and is from the Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
of Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
. It was named in 2001 but has since been reassigned as a basal member of Sebecia
Sebecia
Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include Hamadasuchus, Peirosauridae, and Sebecus. It was initially considered to be the sister taxon of the clade Neosuchia, which includes living...
.
A new genus, Campinasuchus, was assigned to the family in May, 2011. It is known from the Turonian-Santonian Adamantina Formation
Adamantina Formation
The Adamantina Formation is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation...
of the Bauru Basin of Brazil. Soon after, the new genus Pissarrachampsa was named from the Campanian–Maastrichtian Vale do Rio do Peixe Formation, also in the Bauru Basin.
Phylogeny
The family Baurusuchidae was named by BrazilBrazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
ian paleontologist Llewellyn Ivor Price
Llewellyn Ivor Price
Llewellyn Ivor Price was one of the first Brazilian paleontologists.-Biography:Price's work contributed not only to the development of Brazilian but also to global paleontology...
in 1945 to include Baurusuchus. In 1946, American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
paleontologist Edwin Harris Colbert
Edwin Harris Colbert
Edwin Harris Colbert was a distinguished American vertebrate paleontologist and prolific researcher and author. He received his A.B. from the University of Nebraska, then his Masters and Ph.D. from Columbia University, finishing in 1935.Born in Clarinda, Iowa, he grew up in Maryville, Missouri...
erected the group Sebecosuchia
Sebecosuchia
Sebecosuchia is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group first appeared in the Late Cretaceous with the baurusuchids and went extinct in the Miocene with the last sebecids. Fossils have been found primarily from South...
, which united Baurusuchidae with the family Sebecidae
Sebecidae
Sebecidae is an extinct family of prehistoric crocodylomorphs. They lived mostly in Argentina.This group included many medium and large - sized genera, from Sebecus to a giant indeterminate unnamed species from the Miocene.-Phylogeny:...
(represented by the genus Sebecus
Sebecus
Sebecus is an extinct genus of sebecid crocodylomorph from the Eocene of South America. Fossils have been found in Patagonia. Like other sebecosuchians, it was entirely terrestrial and carnivorous. The genus is currently represented by a single species, the type S. icaeorhinus...
). Both Baurusuchus and Sebecus have deep snouts and ziphodont dentitions (teeth that are serrated and laterally compressed). Other forms were later found that had a close appearance to these two genera, among them Cynodontosuchus
Cynodontosuchus
Cynodontosuchus is an extinct genus of baurusuchid mesoeucrocodylian. Fossils have been found from Argentina of Late Cretaceous age from the Bajo de la Carpa Formation as well as the Pichi Picun Leufu Formation...
, Stratiotosuchus
Stratiotosuchus
Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Adamantina Formation, Brazil during the late Cretaceous period . It was first named by Campos, D.A., Suarez, J.M., Riff, D. and Kellner, A.W.A. in 2001 and the type species is Stratiotosuchus maxhechti...
, and Wargosuchus
Wargosuchus
Wargosuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Argentina...
. Several features were used to unite these groups: a deep snout, a ziphodont dentition, a curved tooth row, an enlarged canine-like dentary tooth that fits into a deep notch in the upper jaw, and a groove on the lower jaw.
Many phylogenetic analyses within the past decades have supported a close relationship between the two families. Baurusuchids and sebecosuchids are both early members of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Metasuchia
Metasuchia
Metasuchia is a major clade within the superorder Crocodylomorpha. It is split into two main groups, Notosuchia and Neosuchia. Notosuchia is an extinct group that contains primarily small-bodied Cretaceous taxa with heterodont dentitions. Neosuchia includes extant crocodylians and basal taxa such...
, which includes the subgroups Notosuchia
Notosuchia
Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Cretaceous. Fossils have been found from South America, Africa, and Asia...
(mainly terrestrial crocodyliforms) and Neosuchia
Neosuchia
Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris...
(larger, often semiaquatic crocodyliforms, including living crocodylians). Sebecosuchians, which include both baurusuchids and sebecosuchids, were found to be closely related to notosuchians in several studies. The new genera Iberosuchus
Iberosuchus
Iberosuchus is an extinct genus of sebecid mesoeucrocodylian from the Eocene of western Europe. It was described in 1975 by Antunes from remains from Portugal as a sebecosuchian crocodilian. The type species is I. macrodon...
and Eremosuchus
Eremosuchus
Eremosuchus is an extinct genus of sebecosuchian mesoeucrocodylian. Fossils have been found from El Kohol, Algeria of Eocene age. It had serrated, ziphodont teeth....
were later assigned to Baurusuchidae, and phylogenetic analyses encompassing these taxa continued to find Baurusuchidae to be closely related to Sebecidae. Both families were allied with notosuchians in the larger group Ziphosuchia
Ziphosuchia
Ziphosuchia is a clade of mesoeucrocodylian crocodyliforms that includes notosuchians and sebecosuchians. First constructed in 2000, it was considered to include Notosuchus, Libycosuchus, and Sebecosuchia...
, composed of ziphodont crocodyliforms. More recently, sebecosuchians - including baurusuchids - have been placed within Notosuchia as derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
members of the clade. Below is a modified cladogram from Ortega et al. (2000) placing baurusuchids within Notosuchia:
In 2004, the superfamily Baurusuchoidea was established to include baurusuchids and sebecids. Phylogenetically, Baurusuchoidea was defined as the most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
of Baurusuchus and Sebecus and all of its descendants while Baurusuchidae was defined as the most recent common ancestor of Baurusuchus and Stratiotosuchus
Stratiotosuchus
Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Adamantina Formation, Brazil during the late Cretaceous period . It was first named by Campos, D.A., Suarez, J.M., Riff, D. and Kellner, A.W.A. in 2001 and the type species is Stratiotosuchus maxhechti...
and all of its descendants.
In a 2005 analysis, Sebecidae was found to be a paraphyletic grouping, or a grouping that includes some descendants of a common ancestor but not all. Sebecids formed an assemblage of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
sebecosuchians, while baurusuchids remained a valid grouping of derived sebecosuchians. Below is a modified cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
from Turner and Calvo (2005):
Later studies noted many features that distinguished baurusuchids from sebecosuchids. Sebecosuchids were often considered to be more closely related to Neosuchia
Neosuchia
Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris...
, a group that includes modern crocodylians, while baurusuchids were thought to be a more distantly related clade. In a 1999 phylogenetic analysis, Baurusuchus formed a clade with notosuchians to the exclusion of other ziphosuchians. This placement has been upheld by recent analyses, which place Baurusuchus within Notosuchia.
In 2007, a new clade called Sebecia
Sebecia
Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include Hamadasuchus, Peirosauridae, and Sebecus. It was initially considered to be the sister taxon of the clade Neosuchia, which includes living...
was erected. Sebecia included sebecids and peirosaurids
Peirosauridae
Peirosauridae is a Gondwanan family of mesoeucrocodylians that lived during the Cretaceous period. It was a clade of terrestrial crocodyliforms that evolved a rather dog-like form, and were terrestrial carnivores. It was phylogenetically defined in 2004 as the most recent common ancestor of...
. Peirosauridae, a family of small terrestrial crocodyliforms, had often been placed in or near Neosuchia in previous studies. The assignment of sebecids to Sebecia placed the family closer to Neosuchia than Notosuchia. In this study, baurusuchids were split up, with Baurusuchus placed as a more basal metasuchian and the remaining baurusuchids (Bretesuchus and Pabwehshi
Pabwehshi
Pabwehshi is an extinct genus of mesoeucrocodylian. It is based on GSP-UM 2000, a partial snout and corresponding lower jaw elements, with another snout assigned to it...
) placed as sebecians. Therefore, the family Baurusuchidae was paraphyletic. Below is a modified cladogram from Larsson and Sues (2007):
More recent studies have nested Baurusuchus deep within Notosuchia, just as the larger group Sebecosuchia once was, while the remaining sebecosuchian genera have been placed more distantly in Metasuchia. A new baurusuchid called Pissarrachampsa
Pissarrachampsa
Pissarrachampsa is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil...
was named in 2011, and a comprehensive phylogenetic analysis of baurusuchids was conducted along with its description. Montefeltro et al. (2011) found Baurusuchidae to be a monophyletic group with the genera Baurusuchus, Cynodontosuchus, Pissarrachampsa, Stratiotosuchus, and Wargosuchus. They adopted the name Baurusuchia in a phylogenetic sense to distinguish baurusuchids from related crocodyliforms. Baurusuchia was first erected as an infraorder in 1968, but in the 2011 analysis it was found to be in an identical position to Baurusuchidae in the final tree. The only difference between Baurusuchidae and Baurusuchia is that the former is a node-based taxon and the latter is a stem-based taxon. Baurusuchidae is defined as the least inclusive clade containing Baurusuchus, Cynodontosuchus, Pissarrachampsa, Stratiotosuchus, and Wargosuchus. As in all node-based clades, there is a most recent common ancestor
Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...
; these genera are all of its known descendants. Baurusuchia is defined as Baurusuchus pricei and all Crocodyliformes that share a more recent common ancestor with B. pricei than with Notosuchus terrestris, Mariliasuchus amarali, Armadillosuchus arrudai, Araripesuchus gomesi, Sebecus icaeorhinus, Bretesuchus bonapartei, Peirosaurus tormini, or Crocodylus niloticus.
In contrast to the node-based Baurusuchidae, the stem-based Baurusuchia does not include a common ancestor and all its descendants, but rather all forms more closely related to a specific baurusuchid than a non-baurusuchid. As a stem-based taxon, Baurusuchia is more inclusive than Baurusuchidae; a new taxon could potentially be placed outside Baurusuchidae because it is not a descendant of the most recent common ancestor of baurusuchids, but would still be a baurusuchian because it is more closely related to baurusuchids than it is to other crocodyliforms. For now, however, Baurusuchidae and Baurusuchia are essentially identical in scope.
Montefeltro et al. (2011) also divided Baurusuchidae into two subfamilies, Pissarrachampsinae
Pissarrachampsinae
Pissarrachampsinae is a subfamily of baurusuchid crocodyliforms from the Late Cretaceous of Brazil and Argentina. It was named in 2011 with the description of Pissarrachampsa sera and includes P. sera from Brazil and the related Wargosuchus australis from Argentina...
and Baurusuchinae
Baurusuchinae
Baurusuchinae is a subfamily of baurusuchid crocodyliforms from the Late Cretaceous of Brazil. Named in 2011, it contains the baurusuchids Baurusuchus and Stratiotosuchus. Baurusuchinae is one of two subfamilies of Baurusuchidae, the other being Pissarrachampsinae.Several features distinguish...
. Pissarrachampsinae includes Pissarrachampsa and Wargosuchus while Baurusuchinae includes Stratiotosuchus and Baurusuchus. Cynodontosuchus is not a member of either of these subfamilies, but the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
baurusuchid. Many of the unique features that separate Cynodontosuchus may also be associated with a juvenile individual. The material that Cynodontosuchus is based on has been suggested to be a juvenile form of Baurusuchus, and the two taxa may be synonymous.
Below is a cladogram from Montefeltro et al. (2011):
A sixth genus of baurusuchid, Campinasuchus
Campinasuchus
Campinasuchus is an extinct genus of baurusuchid mesoeucrocodylian which existed in the Minas Gerais State, Brazil during the late Cretaceous period . It is known from four partial skulls from the Honorópolis District of the Adamantina Formation, Bauru Basin. The specimens were collected at Três...
, was named just a few months before Pissarrachampsa, and was not included in the analysis.
Paleobiology
In 2011, fossilized eggs were described from the Late Cretaceous Adamantina FormationAdamantina Formation
The Adamantina Formation is a geological formation in Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation...
of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
that may have been laid by a baurusuchid, most probably Baurusuchus. A new oospecies called Bauruoolithus fragilis
Bauruoolithus
Bauruoolithus is an oogenus of fossilized eggs belonging to an extinct crocodyliform from the Late Cretaceous of Brazil. Bauruoolithus eggs were most likely laid by the notosuchian crocodyliform Baurusuchus. Eggs of Bauruoolithus were described in 2011 from the Adamantina Formation. The type...
was named on the basis of these remains. The eggs are about twice as long as they are wide and have blunt ends. At about a quarter of a millimeter in thickness, the shells are relatively thin. Some eggs may have already hatched by the time they were buried, but none show extensive degradation. In living crocodilians (the closest living relatives of baurusuchids), eggs undergo extrinsic degradation to allow hatchlings to easily break through their shells. The fossils indicate that baurusuchid hatchlings probably broke through thin egg shells rather than shells that had been degraded over their incubation period.