Biology:Stangerochampsa

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Short description: Extinct genus of reptiles

Stangerochampsa
Temporal range: Late Cretaceous, 70.6–66 Ma[1]
Stangerochampsa NMNH.jpg
Skeletal mount on display at the National Museum of Natural History
Scientific classification e
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Superfamily: Alligatoroidea
Clade: Globidonta
Genus: Stangerochampsa
Wu et al., 1996
Type species
Stangerochampsa mccabei
Wu et al., 1996

Stangerochampsa is an extinct genus of globidontan alligatoroid, possibly an alligatorine or a stem-caiman, from the Late Cretaceous of Alberta. It is based on RTMP.86.61.1, a skull, partial lower jaws, and partial postcranial skeleton discovered in the late Campanianearly Maastrichtian-age Horseshoe Canyon Formation. Stangerochampsa was described in 1996 by Wu and colleagues. The type species 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 20.0 centimetres (7.9 in) long from the tip of the snout to the occipital condyle, and is 13.0 centimetres (5.1 in) wide at its greatest, while the thigh bone is 14.2 centimetres (5.6 in) long. It had heterodont dentition, with large crushing teeth at the rear of the jaws.[2]

Classification

Wu and colleagues, using phylogenetic analyses, found their new genus to be closest to Brachychampsa, and then Albertochampsa and Hylaeochampsa successively, as part of a clade within Alligatorinae that also included Allognathosuchus, Ceratosuchus, and Wannaganosuchus. This arrangement also unites most Mesozoic and Paleogene alligatorines.[2] Brochu (1999), in an analysis of all alligatoroids, found Stangerochampsa and Brachychampsa to be just outside Alligatoridae, and suggested that Stangerochampsa and Albertochampsa were synonymous.[3] Brochu (2004)[4] and Hill and Lucas (2006)[5] also found Stangerochampsa to be outside of Alligatorinae; Hill and Lucas found Albertochampsa to its sister taxon.[5]

Below is a cladogram based on the results of a 2018 tip dating study by Lee & Yates that simultaneously used morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data, which shows Stangerochampsa's placement within Globidonta.[6]

Crocodylia
Alligatoroidea

Leidyosuchus

Diplocynodon

Globidonta

Stangerochampsa

Brachychampsa

Navajosuchus

Alligatoridae
Caimaninae

Caiman Caiman crocodilus llanos white background.JPG

Melanosuchus Melanosuchus niger white background.jpg

Paleosuchus Dwarf Caiman white background.jpg

Alligatorinae

Alligator Alligator white background.jpg

extinct basal Crocodilians (including Mekosuchinae)

Longirostres
Crocodyloidea

extinct basal crocodiles

Crocodylidae Siamese Crocodile white background.jpg

Gavialoidea

extinct basal Gavialoids

Gavialidae

Gavialis Gavialis gangeticus (Gharial, Gavial) white background.jpg

Tomistoma Tomistoma schlegelii. white background.JPG

On the other hand, in the phylogenetic analysis conducted by Bona et al. (2018) Stangerochampsa was recovered as an alligatorid, specifically as a stem-caiman, as shown in the cladogram below.[7]

Alligatoroidea

Leidyosuchus

Diplocynodon

Alligatoridae
Alligatorinae

Ceratosuchus

Allognathosuchus

Navajosuchus

Arambourgia

Procaimanoidea

Wannaganosuchus

Alligator prenasalis

Alligator mcgrewi

Alligator olseni

Alligator sinensis Chinese alligator

Culebrasuchus

Alligator mississippiensis American alligator

Alligator mefferdi

Alligator thomsoni

(stem‑based group)
Caimaninae

Stangerochampsa

Albertochampsa

Brachychampsa

Protocaiman

Gnatusuchus

Globidentosuchus

Eocaiman

Notocaiman

Kuttanacaiman

Purussaurus

Mourasuchus

Necrosuchus

Tsoabichi

Paleosuchus trigonatus Smooth-fronted caiman

Paleosuchus palpebrosus Cuvier's dwarf caiman

Centenariosuchus

Caiman latirostris Broad-snouted caiman

Melanosuchus niger Black caiman

Caiman yacare Yacare caiman

Caiman crocodilus Spectacled caiman

Caiman brevirostris

La Venta Caiman

Caiman wannlangstoni

(stem‑based group)
(crown group)
(stem‑based group)

References

  1. Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ 9: e12094. doi:10.7717/peerj.12094. PMID 34567843. 
  2. 2.0 2.1 Wu, Xiao-Chun; Brinkman, Donald B.; Russell, Anthony P. (1996). "A new alligator from the Upper Cretaceous of Canada and the relationships of early eusuchians". Palaeontology 39 (2): 351–375. http://palaeontology.palass-pubs.org/pdf/Vol%2039/Pages%20351-375.pdf. 
  3. Brochu, C. A. (1999). "Phylogenetics, taxonomy, and historical biogeography of Alligatoroidea". Society of Vertebrate Paleontology Memoir 6: 9–100. doi:10.2307/3889340. 
  4. Brochu, Christopher A. (2004). "Alligatorine phylogeny and the status of Allognathosuchus Mook, 1921". Journal of Vertebrate Paleontology 24 (4): 857–873. doi:10.1671/0272-4634(2004)024[0857:APATSO2.0.CO;2]. 
  5. 5.0 5.1 Hill, Robert V.; Lucas, Spencer G. (2006). "New data on the anatomy and relationships of the Paleocene crocodylian Akanthosuchus langstoni". Acta Palaeontologica Polonica 51 (3): 455–464. http://www.app.pan.pl/archive/published/app51/app51-455.pdf. 
  6. Michael S. Y. Lee; Adam M. Yates (27 June 2018). "Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil". Proceedings of the Royal Society B: Biological Sciences 285 (1881). doi:10.1098/rspb.2018.1071. PMID 30051855. 
  7. Paula Bona; Martín D. Ezcurra; Francisco Barrios; María V. Fernandez Blanco (2018). "A new Palaeocene crocodylian from southern Argentina sheds light on the early history of caimanines". Proceedings of the Royal Society B: Biological Sciences 285 (1885): 20180843. doi:10.1098/rspb.2018.0843. PMID 30135152. 

Wikidata ☰ Q7598843 entry