Steneosaurus, GEOFFROY SAINT-HILAIRE, 1825

Johnson, Michela M, Young, Mark T & Brusatte, Stephen L, 2020, REVIEW Emptying the wastebasket: a historical and taxonomic revision of the Jurassic crocodylomorph Steneosaurus, Zoological Journal of the Linnean Society 189 (2), pp. 428-448 : 435-437

publication ID	https://doi.org/10.1093/zoolinnean/zlaa027
persistent identifier	https://treatment.plazi.org/id/03AB87AD-DA24-4415-FC95-03F3459F4D7D
treatment provided by	Plazi
scientific name	Steneosaurus
status

Treatment

STENEOSAURUS GEOFFROY SAINT-HILAIRE, 1825

STENEOSAURUS ROSTROMAJOR GEOFFROY SAINT-HILAIRE, 1825 (TYPE SPECIES, DESIGNATED HERE)

( FIG. 1 View Figure 1 )

Etymology: Named rostro-major (from Latin major, elongated, and rostrum, snout) by Geoffroy Saint-Hilaire (1825), to emphasize the elongation of the maxillae. According to the ICZN Code, Article 32.5.2.3: ‘In a compound species-group name published as words united by an apostrophe or a hyphen, the words are to be united by removing the mark concerned.’ Therefore, S. rostro-major is recognized as S. rostromajor .

v 1800 ‘Crocodilian’ snout; Cuvier, p. 159

v 1808 ‘Crocodilian’ snout; Cuvier, pp. 20–21, pl.II, figs 3, 4

v 1812 ‘Crocodilian’ snout; Cuvier, pp. 20–21, pl. II, figs 3, 4

v 1824 ‘ Tête à museau plus allongé ’; Cuvier, p. 148, pl. VII, figs 3, 4; pl. X, fig. 1

v 1825 Steneosaurus rostromajor nov. sp.; Geoffroy Saint-Hilaire, pp. 146–147

v 1829 Steneosaurus longirostris ; Holl, p. 88

v 1831 Gavialis bacheleti ; Gray, p. 57

v 1831 Steneosaurus rostromajor ; Geoffroy Saint-Hilaire, p. 40

v 1832 Streptospondylus altdorfensis ; von Meyer, p. 227

v 1835 –37 Leptocranius nov. gen.; Bronn, p. 516

v 1841 Steneosaurus rostromajor ; Owen, p. 88

v 1846 Leptocranius ; Geinitz, p. 87

v 1847 Leptocranius ; Giebel, p. 113–114

Designation of type species: JacquesAmand and Eugène Eudes-Deslongchamps (1867 –69) attempted to rectify the taxonomic issues associated with S. rostromajor (MNHN.RJN 134c-d) and selected a new type species for Steneosaurus (either ‘ S.’ megistorhynchus or ‘ S.’ edwardsi, see above). However, the ICZN did not exist during that time and, unfortunately, their selection does not conform to the current articles of the Code. Herein we formally designate S. rostromajor as the type species of Steneosaurus . In order to be in full accordance of Article 67 of the ICZN Code, in particular Article 67.2, we make the following statements:

1. This designation is made with the express purpose of clarifying the taxonomic status of S. rostromajor .

2. MNHN. RJN 134 About MNHN c-d is an originally included nominal specimen and, therefore, is eligible to be fixed as the type. In addition, the name Steneosaurus rostromajor was established for MNHN. RJN 134 About MNHN c-d before 1931 and, therefore, is deemed to be the only originally included nominal species .

3. The type species can be recognized through both the description below and Figure 1 View Figure 1 , as well as in the works of Cuvier (1808, pl. II, figs 3, 4; 1812, pl. II, figs 3, 4; 1824, pl. VII, figs 3, 4; pl. X, fig. 1) and Geoffroy Saint-Hilaire (1825, 1831).

4. Cuvier’s ‘ tête à museau plus allongé ’ specimen (1808, 1812, 1824) was attributed to the name Steneosaurus rostro-major by Geoffroy Saint-Hilaire in 1825 as the ‘ première espèce ’ (‘first species) of Steneosaurus (i.e. position precedence).

5. The type species is the property of a recognized scientific institution, MNHN, which maintains a research collection with proper facilities for preserving name-bearing types and is accessible for study .

Designation of type specimen: Given that the type specimen of Steneosaurus rostromajor is a chimera of teleosauroid and metriorhynchid material (see above), we herein rectify this issue. Following Article 74.7 of the ICZN Code we hereby designate MNHN.RJN 13c-d as the lectotype of S. rostromajor . This ensures that the teleosauroid component of the original specimen is now formally the type specimen of S. rostromajor , and ensures taxonomic stability.

Lectotype: MNHN. RJN 134 About MNHN c-d, a partial rostrum covered in ironstone sediment and oysters, and severely broken and dorsally displaced in the middle.

Lectotype age: Callovian or Oxfordian , Middle or Late Jurassic (Lower Oxfordian if from Marnes de Villiers Formation).

Lectotype locality and stratigraphic horizon: Vaches Noires , Calvados , France. Suggested to be from the Marnes de Villiers Formation.

Description: The type specimen of Steneosaurus , Steneosaurus rostromajor (MNHN.RJN 134c-d), is represented by a partial rostrum that is preserved up until the 27 th maxillary alveolar pair. The majority of the premaxillae are missing, so none of the premaxillary alveoli are preserved. At approximately the 12 th maxillary alveolus, the remaining posterior portion of the specimen has been distorted and dorsally displaced ( Fig. 1A, B View Figure 1 ). In dorsal view, there is a large posteriorly directed crack in this area, which is also covered with an array of fossilized oysters. In ventral view ( Fig. 1C, D View Figure 1 ), there is a massive, anteroposteriorly directed crack running through the midline of the rostrum. At approximately the 19 th alveolus, a missing section of the palatal surface continues to the end of the specimen.

Premaxillae: As mentioned previously, the majority of the premaxillae are not preserved, so neither the external nares nor any of the premaxillary alveoli can be described. However, the posterior-most portion of the paired premaxillae is robust and horizontally straight in lateral view; these bones would have surrounded the external nares, as in other teleosauroids (e.g. Indosinosuchus potamosiamensis Martin et al., 2019 , PRC-11; ‘ Steneosaurus ’ leedsi Andrews, 1909, NHMUK PV R 3806 and ‘ Steneosaurus ’ edwardsi NHMUK PV R 2865). In dorsal view, the premaxilla–maxilla suture is subcircular in shape and moderately interdigitating, most notably at the midline ( Fig. 1A, B View Figure 1 ); in lateral view, it is slightly anteroposteriorly curved; and in ventral view, the posterior area is vertically directed, similar to that found in other teleosauroids (e.g. ‘ S.’ leedsi NHMUK PV R 3806; ‘ S.’ edwardsi NHMUK PV R 2865 and NHMUK PV R 3701). The premaxillae are ornamented with numerous, irregular grooves with varying degrees of depth.

Maxillae: The paired maxillae ( Fig. 1 View Figure 1 ) are elongate, anteriorly separate from the premaxillae, transversely narrow and make up the majority of the rostrum. The dorsal surface of the maxillae are ornamented with conspicuous, weakly-to-deeply excavated grooves. In lateral view, one line of small, sparsely spaced neurovascular foramina is present dorsally parallel to the maxillary tooth row. The reception pits are relatively deep in the anterior maxilla, but gradually become much shallower nearer to the posterior part of the rostrum. The anterior maxillae are unornamented in ventral view, and it is near impossible to observe any palatal features posterior to the 11 th maxillary alveolus due to poor preservation. There are at least 27 maxillary alveoli per side, which are subcircular, large and well spaced. There is an extensive interalveolar region between each adjacent alveoli, with each being between 9 and 11 mm throughout the entirety of the maxilla (excluding the first two alveoli). Two anterior alveoli ( Fig. 1C, D View Figure 1 ) have partially preserved teeth in the sockets.

Dentition: Only two partial teeth are preserved in situ in MNHN.RJN 134c-d (at the third and fourth left maxillary alveoli), both of which consist of the area near the base (they are both missing the apex and half of the tooth body). The teeth are slightly laterally compressed with numerous, well-developed and pronounced enamel ridges (see Fig. 5A View Figure 5 ).