''Stangerochampsa'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of alligatorid, possibly an

alligatorine Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genera in Alligatorinae are described, but only the genus ''A ...

or a

stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...

caiman A caiman ( (also spelled cayman) from Taíno language, Taíno ''kaiman'') is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family (biology), family, the other being alligators. ...

, from 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 ...

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

. It is based on

RTMP RTMP may refer to: * Real-Time Messaging Protocol, a multimedia streaming and remote procedure call protocol primarily used in Adobe Flash * Routing Table Maintenance Protocol, part of the AppleTalk network stack * Royal Tyrrell Museum of Palaeon ...

.86.61.1, a skull, partial lower jaws, and partial postcranial skeleton discovered in the late Campanian– early Maastrichtian-age

Horseshoe Canyon Formation The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta. It takes its name from Horseshoe Canyon, an area of badlands near Drumheller. The Horseshoe Canyon Formation is part of th ...

. ''Stangerochampsa'' was described in 1996 by Wu and colleagues. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''S. mccabei''. The generic name honors the Stanger family, the owners of the ranch where the specimen was found, and the species name honors James Ross McCabe, who discovered, collected, and prepared it. ''Stangerochampsa'' is described as "small to medium–sized"; the type skull is long from the tip of the snout to the

occipital condyle The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the Atlas (anatomy), atlas vertebra. The condyles are oval or reniform (kidney-shaped) in shape ...

, and is wide at its greatest, while the

thigh bone The femur (; : femurs or femora ), or thigh bone is the only bone in the thigh — the region of the lower limb between the hip and the knee. In many four-legged animals the femur is the upper bone of the hindleg. The top of the femur fits in ...

is long. It had

heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...

dentition, with large crushing teeth at the rear of the jaws.

Classification

Wu and colleagues, using

phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...

, found their new genus to be closest to '' Brachychampsa'', and then '' Albertochampsa'' and ''

Hylaeochampsa ''Hylaeochampsa'' is an extinct genus of eusuchian crocodylomorphs. It is known only from a partial skull recovered from Barremian-age rocks of the Lower Cretaceous Vectis Formation (Wealden Group) of the Isle of Wight. This skull, BMNH R 177, ...

'' successively, as part of a

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 ...

within

Alligatorinae Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genera in Alligatorinae are described, but only the genus ' ...

that also included ''

Allognathosuchus ''Allognathosuchus'' (meaning "other jaw crocodile") is an extinct genus of alligatorine crocodylian with a complicated taxonomic history. It was named in 1921. Description ''Allognathosuchus'' was a medium-sized predator up to 1.5 m in length. ...

'', ''

Ceratosuchus ''Ceratosuchus'' ("horned crocodile") is an extinct genus of alligatorine crocodylian from latest Paleocene rocks of Colorado's Piceance Basin and earliest Eocene rocks of Wyoming's Bighorn Basin in North America, a slice of time known as the ...

'', and '' Wannaganosuchus''. This arrangement also unites most

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

and

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

alligatorines. Brochu (1999), in an analysis of all alligatoroids, found ''Stangerochampsa'' and ''Brachychampsa'' to be just outside

Alligatoridae The family (biology), family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives. Phylogeny The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the Am ...

, and suggested that ''Stangerochampsa'' and ''Albertochampsa'' were

synonymous A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

. Brochu (2004) and Hill and Lucas (2006) also found ''Stangerochampsa'' to be outside of Alligatorinae; Hill and Lucas found ''Albertochampsa'' to its

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 ...

. Below is a

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 ...

based on the results of a 2018

tip dating Tip dating is a technique used in molecular dating that allows the inference of time-calibrated phylogenetic trees. Its defining feature is that it uses the ages of the samples to provide time information for the analysis, in contrast with traditio ...

study by Lee & Yates that simultaneously used morphological, molecular (

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, thymine, cytosine, and guanine. The ...

), and

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

(

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

age) data, which shows ''Stangerochampsa's'' placement within

Globidonta Globidonta is a clade of alligatoroids that includes alligators, caimans, and closely related extinct forms. It is defined as a Stem-based taxon, stem-based clade including ''Alligator mississippiensis'' (the American Alligator) and all forms mor ...

. On the other hand, in the phylogenetic analysis conducted by Bona ''et al.'' (2018) ''Stangerochampsa'' was recovered as an alligatorid, specifically as a

-caiman, as shown in the cladogram below. ''Stangerochampsa'' was recovered as a stem-group caiman in 2021, but it was also recovered as a basal alligatorine in 2022.

References

{{Taxonbar, from=Q7598843 Alligatoroidea Late Cretaceous crocodylomorphs of North America Late Cretaceous reptiles of North America Prehistoric pseudosuchian genera Paleontology in Alberta