Sebecia is an extinct
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of
mesoeucrocodylia
Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day.
Diagnosis
It was long known that Me ...
n
crocodyliform
Crocodyliformes is a clade of Crurotarsi, crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the ...
s that includes
peirosaurid
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 skull, and were terrestrial carnivores. It was phylogenetically defined ...
s and
sebecids. It was first constructed in 2007 to include ''
Hamadasuchus'', Peirosauridae, and ''
Sebecus
''Sebecus'' (meaning "Sobek" in Latin) is an extinct genus of Sebecidae, sebecid crocodylomorph from Paleogene period of South America. Like other sebecosuchians, it was entirely terrestrial and carnivorous. The genus is currently represented by ...
''. It was initially considered to be the
sister taxon
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
of the clade
Neosuchia
Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all Crocodylomorpha, crocodylomorphs more closely related to ''Croc ...
, which includes living
crocodilia
Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...
ns, although some later studies have placed it within Neosuchia as a
basal clade.
Sebecians were terrestrial crocodyliforms characterized by their deep snouts and
ziphodont dentition. They first appeared in the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
, survived the
Cretaceous–Paleogene extinction event
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the extinction event, mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event cau ...
, and became extinct in the
Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
or
early Pliocene
Early may refer to:
Places in the United States
* Early, Iowa, a city
* Early, Texas, a city
* Early Branch, a stream in Missouri
* Early County, Georgia
* Fort Early, Georgia, an early 19th century fort
Music
* Early B, stage name of Jamaican d ...
epoch, making them a highly successful and long-lived group.
According to paleontologists
Hans Larsson and
Hans-Dieter Sues
Hans-Dieter Sues (born 1956) is a German-born American palaeontologist who is a Senior Research Geologist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC.
Career ...
, who constructed the clade in 2007, Sebecia also includes genera that were once assigned to
Baurusuchidae
Baurusuchidae is a Gondwanan family of mesoeucrocodylians 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, ...
, namely ''
Pabwehshi''. However, other baurusuchids, namely ''
Baurusuchus'', were placed outside Sebecia. Therefore, Baurusuchidae was considered
polyphyletic
A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
and thus not a true clade. Juan Leardi and colleagues in 2024 defined Sebecia in the ''
PhyloCode
The ''International Code of Phylogenetic Nomenclature'', known as the ''PhyloCode'' for short, is a formal set of rules governing phylogenetic nomenclature. Its current version is specifically designed to regulate the naming of clades, leaving the ...
'' as "the most inclusive clade including ''
Sebecus icaeorhinus'' and ''
Lomasuchus palpebrosus'', but not ''
Baurusuchus pachecoi'', ''
Notosuchus terrestris
''Notosuchus'' (; 'southern crocodile') is an extinct genus of South American notosuchian crocodyliforms. It was terrestrial, living approximately 85 million years ago in the Santonian stage of the Late Cretaceous.
Description
''Notosuchus'' ...
'', and ''
Crocodylus niloticus
The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed in sub-Saharan Africa, occurring mostly in the eastern, southern, and ce ...
''".
Below is the
cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
produced from Larsson and Sues'
phylogenetic
In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
analysis:
[
Larsson and Sues defined Sebecidae as all taxa more closely related to ''Sebecus'' than to '']Peirosaurus
''Peirosaurus'' is an extinct genus of peirosaurid crocodylomorph known from the Late Cretaceous period (late Maastrichtian stage) of Minas Gerais, southern Brazil. It contains a single species, ''Peirosaurus torminni''. It is the type genus of t ...
'' or ''