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Gnathomortis stadtmani

Reptilia - Mosasauridae

Taxonomy
Prognathodon stadtmani was named by Kass (1999). Its type specimen is BYU 13082, a partial skeleton, and it is a 3D body fossil. Its type locality is Cedar Mesa Road, East of Cedaredge, which is in a Campanian offshore siltstone in the Mancos Shale Formation of Colorado. It is the type species of Gnathomortis.

It was recombined as Gnathomortis stadtmani by Lively (2020).

Synonymy list
YearName and author
1999Prognathodon stadtmani Kass
2020Gnathomortis stadtmani Lively p. 15

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Life
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
Osteichthyes()
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
RankNameAuthor
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
Amniota
Sauropsida
classReptilia
Squamata()
familyMosasauridae
subfamilyMosasaurinaeGervais 1853
genusGnathomortis
speciesstadtmani()

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

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Diagnosis
ReferenceDiagnosis
J. R. Lively 2020Gnathomortis stadtmani is diagnosed from all other mosasaurines by the following unique combination of characters and autapomorphies (denoted by an *): a small pre- dental rostrum that resembles those of Prognathodon spp., differ- ing from the long, pointed rostrum of early-diverging mosasaurines such as Clidastes propython and the inflated, rec- tangular rostrum of Plesiotylosaurus crassidens; 13 tooth positions in the maxilla, as in Prognathodon kianda, Prognathodon overtoni, Globidens dakotensis, and Eremiasaurus heterodontus; a premaxilla-maxilla suture that ends dorsal to the fourth tooth position, as in Globidens dakotensis and some early-diverging mosasaurines, differing from the shorter suture observed in Prognathodon overtoni; shallow excavation of the dorsal maxilla by the external naris, differing from the deeper emargina- tion exhibited by Prognathodon spp. and early-diverging mosa- saurines and the lack of emargination exhibited by Mosasaurus spp. and Plesiotylosaurus crassidens; pterygoid tooth crowns that are smaller than the marginal dentition, differing from members of Prognathodon spp.; posteromedial margin of the frontal and pineal foramen separated by a distance narrower than the length of the foramen, as in Globidens dakotensis, Plesiotylosaurus crassidens, and Mosasaurus spp.; contact between the prefrontal and postorbitofrontal on the ventral surface of the frontal, as in Prognathodon spp., Globidens spp., Mosasaurus spp., Plotosaurus bennisoni, Plesiotylosaurus crassidens, and Eremiasaurus heterodontus; straight anterodorsal margin of the suprastapedial process, differing from the curved margin in other described mosasaurines*; a suprastapedial process of the quadrate that is half as tall as the total height of the element; a narrow separation between the ascending tympanic rim and the suprastapedial process*, lacking the fusion of those two structures seen in Prognathodon, Globidens, Eremiasaurus, and Plesiotylosaurus; an infrastapedial process represented by a small swelling ventral to the stapedial notch, as in Clidastes propython; a dorsoventrally expanded quadrate shaft ventral to the tympanic ala, greater than 50% the height of the ala, as in Prognathodon, Globidens, and Plesiotylosaurus; a prominent anterodorsal projection of the mandibular condyle, as in Clidastes propython; 14 tooth positions in the dentary*; medial inflection of the retroarticular process almost into the horizontal plane, as in Mosasaurus, Plotosaurus, Prognathodon, and Globidens; concave ventral margin of the atlantal synapo- physes, as in other mosasaurines except Mosasaurus spp. Gnathomortis stadtmani is currently the oldest known mosasaur- ine with a skull longer than 1 m.
Measurements
No measurements are available
Composition: phosphaticsubp
Environment: terrestrialuc
Locomotion: actively mobilec
Life habit: aquaticf
Diet: carnivoref
Vision: well-developedf
Reproduction: ovoviviparousf
Created: 2018-01-05 16:32:54
Modified: 2018-01-05 16:32:54
Source: f = family, c = class, subp = subphylum, uc = unranked clade
References: Gervais 1852, Carroll 1988, Hendy et al. 2009

Age range: Middle Campanian or 83.50000 to 70.60000 Ma

Collections: one only


Time interval Ma Country or state Original ID and collection number
Middle Campanian83.5 - 70.6USA (Colorado) Prognathodon stadtmani (type locality: 5607)