Thalattosuchus superciliosus, Young & Brignon & Sachs & Hornung & Foffa & Kitson & Johnson & Steel, 2021, Young & Brignon & Sachs & Hornung & Foffa & Kitson & Johnson & Steel, 2021

Young, Mark T., Brignon, Arnaud, Sachs, Sven, Hornung, Jahn J., Foffa, Davide, Kitson, James J. N., Johnson, Michela M. & Steel, Lorna, 2021, Cutting the Gordian knot: a historical and taxonomic revision of the Jurassic crocodylomorph Metriorhynchus, Zoological Journal of the Linnean Society 192 (2), pp. 510-553 : 538-543

THALATTOSUCHUS SUPERCILIOSUS (BLAINVILLE IN EUDES- DESLONGCHAMPS, 1852) GEN. & COMB. NOV.

( FIG. 6 )

v 1808 Espèce inconnue de crocodile – Cuvier, pp. 90–92, pl. 11, figs 1, 2. [partim]

v 1824 Tête à museau plus court – Cuvier, pp. 152–153, pl. 8, figs 1, 2. [partim]

v 1825 Steneosaurus rostro -minor [sic] sp. nov. – Geoffroy Saint-Hilaire, pp. 147, 149. [nomen oblitum]

v 1832 Streptospondylus altfordensis sp. nov. – von Meyer, p. 106. [partim]

v 1837 Metriorhynchus geoffroyi [sic] von Meyer – Bronn, 1835 –37, p. 520, pl. 26, fig. 7b [partim]

v* 1852 Crocodilus superciliosus sp. nov. – Blainville in J.-A. Eudes-Deslongchamps, p. 114.

v 1863 Teleosaurus superciliosus (Blainville) comb. nov. – J.-A. Eudes-Deslongchamps, p. 8.

v 1867 Teleosaurus superciliosus (Blainville) – J.-A. Eudes- Deslongchamps, pp. 20–21.

v 1867 Teleosaurus blainvillei sp. nov. – J.-A. Eudes- Deslongchamps, pp. 19–20.

v 1869 Metriorhynchus superciliosus (Blainville) comb.nov. – Eudes- Deslongchamps,1867–69, p. 306, pl. 20, fig.2, pl. 21, fig. 1.

v 1869 Metriorhynchus blainvillei (E-Deslongchamps) comb. nov. – Eudes-Deslongchamps, 1867 –69, p. 295, pl. 20 fig. 1, pl. 21, figs 2, 3.

v 1869 Metriorhynchus moreli sp. nov. – Eudes-Deslongchamps, 1867 –69, p. 320, pl. 21, figs 4, 5, pl. 22, figs 1, 2.

v 1869 Steneosaurus dasyceps sp. nov. – Seeley, p. 140.

v 1890 b Metriorhynchus superciliosum (Blainville) unjust. emend. – Lydekker, p. 232.

v 1904 Metriorhynchus jaekeli sp. nov. – Schmidt, p. 97, pls 11, 12.

v 1973 Metriorhynchus superciliosum [sic] (Blainville) – Steel, p. 45, figs 18 (7, 9), 19 (7).

v 1973 Metriorhynchus blainvillei (Eudes-Deslongchamps) – Steel, p. 46, fig. 19 (2).

v 1973 Metriorhynchus moreli (Eudes-Deslongchamps) – Steel, p. 46, fig. 19 (1).

v 2009 Metriorhynchus moreli (Eudes-Deslongchamps) – Young & Andrade, p. 566.

v 2009 Metriorhynchus superciliosus (Blainville) – Young & Andrade, p. 566.

v 2010 Metriorhynchus superciliosus (Blainville) – Young et al., p. 804, figs 4, 6, 8.

v 2018 Metriorhynchus superciliosus (Blainville) – Brignon, pp. 56–61, fig. 11.

Lectotype: MNHN.F.RJN 256 , incomplete skull. (Designation by Eudes-Deslongchamps, 1867 –69: 310).

Note: Young et al. (2013) followed Vignaud (1995) in calling MNHN.F. RJN 256 (formerly MNHN 8903) the neotype. As shown by Brignon (2018a), it is in fact the lectotype.

Type locality: Vaches Noires cliffs , Département du Calvados, Basse-Normandie, France.

Type horizon: Either the Marnes de Dives Formation or Marnes de Villers Formation. Either upper Callovian or lower Oxfordian, Middle or Upper Jurassic.

Occurrence: Callovian/Oxfordian of northern France and England ( UK). LSID

Zoobank registration: urn: lsid: zoobank. org:act: 151309F9-ED14-43C6-A00F-6BFFED2DD3A2

Etymology: The genus is derived from the Greek θάλαττα, sea, and σοῦχος crocodile (after the Egyptian crocodile god). The species name derives from Latin, the prefix super-, above, and ciliosus, with eyelashes,

referring to the expanded prefrontals above the orbits.

Diagnosis: Metriorhynchid crocodylomorph with the following unique combination of characters: conical teeth with little mediolateral compression, crowns have a continuous smooth keel at mesial and distal edges (lacks serrations), enamel on labial and lingual surfaces have conspicuous ornamentation composed of accessory ridges orientated to the apicobasal axis of the crown. Enamel ornamentation is stronger on the lingual face than on the labial face. Dental formula: three premaxillary pairs; 23–27 maxillary pairs, of which 14–15 are anterior to the palatines; 20–22 dentary pairs, of which 16–17 are adjacent to the symphyseal suture and nine to ten are anterior to the splenials. Premaxillary alveoli are consistent in size, with the P1 and P3 being more oval in shape, with the P2 being more subcircular. The skull is narrow with a mesorostrine snout ( sensu Young et al. 2010 ). No transverse expansion of the premaxilla (only present in dorsoventrally crushed specimens). Little to no constriction at the premaxilla–maxilla contact. Nasals and premaxillae always separated; in specimens with a basicranial length of 600 mm or more, the distance between the nasals and premaxillae range from 50 to 132 mm. The nasals terminate anteriorly level to the M9-to-M12 alveoli. Both the frontal and prefrontal bones have a conspicuous pitted ornamentation, although the expression of frontal ornamentation is highly variable. Approximately 90-degree angle formed by the lateral and medial processes of the frontal, with the rostromedial border of the frontoparietal fossa being either rounded or forming a right angle (variability most likely due to taphonomic distortion). A thin sclerotic ring composed of seven ossicles, which do not fill the entire orbit. The deltopectoral crest is moderately developed, with the width of the humerus distal articular head being greater than the width of the deltopectoral crest projecting out from the humerus shaft. (Modified from Young et al., 2013.)

Referred specimens

AMNH FR 997: Incomplete skull with mandible, and 23 assorted vertebrae (including cervicals and dorsals); CAMSM J64398 : skull (holotype of Steneosaurus dasyceps ); CAMSM J64900 : midportion of skull; CAMSM J64918 : rostrum; GLAHM V 942: skull with mandible from a young individual; GLAHM V 963: incomplete skull and mandible, eight dorsal vertebrae, one caudal vertebra, both coracoids, left scapula, right ilium, left ischium and right ischium blade, distal half of the right pubis (from a young individual); GLAHM V 964: skull, mandible, atlas–axis, four cervical vertebrae, cervical and dorsal ribs; GLAHM V 965: skull with right dentary; GLAHM V 971: skull in various fragments, atlas–axis, five cervical vertebrae, ten dorsal vertebrae; GLAHM V 982: broken skull, mandible, cervical vertebra centrum, atlas left rib; GLAHM V 983: broken skull, mandible, sclerotic ring ossicles, dorsal rib; GLAHM V 984: broken skull and mandible fragments from two individuals; GLAHM V 985: broken skull and mandible fragments, sclerotic ring ossicles; GLAHM V 987: broken skull and mandible fragments, sclerotic ring ossicles, rib fragments; GLAHM V 988: skull, mandible, atlas–axis, one dorsal vertebra, left ilium, fragment of right pubis, right femur; GLAHM V 989: skull with mandible; GLAHM V 996: skull with bite marks consistent with that of a metriorhynchid; GLAHM V 1004: skull and mandible fragments, atlas–axis; GLAHM V 1015: incomplete skull, disarticulated mandible, atlas–axis, right atlas rib, both coracoids, right ischium, femora, right tibia and fibula, two coprolites; GLAHM V 1027: incomplete skull and mandible, atlas–axis, four cervical vertebrae (from a young individual); GLAHM V 1140: broken skull, mandible showing pathological damage, one hyoid, atlas–axis, five cervical vertebrae, 14 dorsal vertebrae, scapulae, both coracoids, humeri, both radii, femora; GLAHM V 1142: skull, disarticulated mandible, one hyoid, atlas–axis, right atlas rib, four cervical vertebrae, 19 dorsal vertebrae, two sacral vertebrae, four caudal vertebrae, pubes, ilia, ischia – fused, femora; GLAHM V 1143: skull broken in two, mandible, atlas ribs, five cervical vertebrae, four cervical ribs, 17 dorsal vertebrae, right scapula, right coracoid, right humerus (atlas–axis and forelimb lost); MGCL 9959: skull, mandible, associated dorsal and caudal vertebrae, humerus, femur; MGCL 9960: skull, mandible, associated cervical, dorsal and caudal vertebrae, isolated ribs, humerus, pubis, ischium, femur; MNHN.F RJN 116: lower jaw (lectotype of Steneosaurus rostrominor , nomen oblitum); NHMUK PV R 1530: incomplete skull with mandible, atlas–axis, five cervical vertebrae, 16 dorsal vertebrae, two sacral vertebrae, 35 caudal vertebrae, cervical and dorsal ribs, coracoid, scapula, humeri, ilia, ischia, pubes, femora, tibiae, fibulae, isolated pes bones, numerous chevrons; NHMUK PV R 1529: skull and mandible (from a young individual); NHMUK PV R 1666: skull and mandible; NHMUK PV R 2030: incomplete skull with mandible; NHMUK PV R 2032: incomplete skull and mandible, atlas–axis, four cervical vertebrae, 17 dorsal vertebrae, two sacral vertebrae, 37 caudal vertebrae, cervical and dorsal ribs, scapula, coracoids, humerus, ilium, ischium, femur; NHMUK PV R 2033: fragmentary skull with mandible, atlas–axis, five cervical vertebrae, 17 dorsal vertebrae, two sacral vertebrae, 29 caudal vertebrae, cervical and dorsal ribs, ilia – fused, ischia – fused, pubes, one tibia, one fibula, two metatarsals; NHMUK PV R 2036: fragments of skull and mandible, one cervical vertebra; NHMUK PV R 2041: incomplete skull; NHMUK PV R 2044: skull and mandible; NHMUK PV R 2049: incomplete skull and mandible, two dorsal vertebrae, one sacral vertebra, ilia, ischia, femora, tibiae, fibulae, isolated bones of the pes; NHMUK PV R 2051: incomplete skull with mandible, atlas–axis, four cervical vertebrae, 15 dorsal vertebrae, two sacral vertebrae, 32 caudal vertebrae, coracoid, scapula, ilia, ischia, pubes, femora, broken tibiae and fibulae, isolated pes bones; NHMUK PV R 2053: incomplete skull; NHMUK PV R 2054: skull, mandible, atlas–axis, four cervical vertebrae, 18 dorsal vertebrae, two sacral vertebrae, 28 caudal vertebrae, cervical and dorsal ribs, ilium, ischium, pubes, tibia, fibula, isolated pes bones, numerous chevrons; NHMUK PV R 2055: incomplete skull; NHMUK PV R 2056: fragments of skull and mandible (from a young individual); NHMUK PV R 2058: skull with mandibular symphysis; NHMUK PV R 2065: skull fragments (from a young individual); NHMUK PV R 2069: fragments of skull and mandible, atlas–axis, three cervical vertebrae (from a young individual); NHMUK PV R 3016: incomplete skull, mandible, right coracoid, scapulae, humeri, radius, ulna; NHMUK PV R 6859: skull with disarticulated mandible; NHMUK PV R 6860: skull with disarticulated mandible; PETMG R8: skull lacking rostrum; PETMG R10: incomplete skull; PETMG R20: incomplete skull; PETMG R42: incomplete skull; PETMG R180: incomplete skull; SMNS 10115: skull with disarticulated mandible; SMNS 10116: skull with disarticulated mandible.

Note: The possibility that Thalattosuchus superciliosus is a species-complex and that the epithets moreli or blainvillei could represent cryptic species is not investigated. That is beyond the scope of this contribution and will be examined in future studies.

Figures

Figure 6. Thalattosuchus superciliosus lectotype MNHN.F RJN 256. A, dorsal view; B, palatal view; C, left lateral view. Scale bar = 10 cm.