Grallator variabilis Lapparent & Montenat, 1967

Moreau, Jean-David, Vullo, Romain, Bichr, Elsie, Thomas, Jérôme, Gand, Georges, Gagnaison, Cyril, Barrier, Pascal & Néraudeau, Didier, 2024, Crocodylomorph and dinosaur tracks from the lowermost Jurassic of Le Veillon (western France): ichnotaxonomic revision of the type material (Lapparent collection), Geodiversitas 46 (8), pp. 343-366 : 349-353

Grallator variabilis Lapparent & Montenat, 1967

( Fig. 5 )

Grallator variabilis Lapparent & Montenat, 1967: 16-20 , pls III.3, IV-VII, IX, XII.2, XIII.1-2, figs 7, 9-10. — Demathieu & Sciau 1992: 1565, fig. 3B. — Sciau 1998: 18; 2003: 27, 84; 2012: 54. — Demathieu et al. 2002: 79, pls I.1, V.

HOLOTYPE. — ULB-04C08_D (plaster cast; Fig. 5 A-C).

PARATYPES. — ULB-04C05_A ( Fig. 5 D-F) and ULB-04C08_A .

EXAMINED MATERIAL. — ULB-04C05_B , ULB-04C08_B , ULB-04C08_F , ULB-04C13_A , ULB-04C14_J , ULB-04C15_D , ULB-04C15_E , ULB-04C17_C , ULB-04C17_D , ULB-04C17_G , ULB-04C18_B , ULB-04C18_C , ULB-04D18_A , ULB-04D18_B , ULB-04D18_C , ULB-04D18_D .

EMENDED DIAGNOSIS. — Tridactyl, small-sized tracks (L = 8-14 cm), longer than wide (L/W = 1.6 in average).Quite long projection of the trace of digit III (L/D = 2.5 in average). Well-defined, thin, elongated and often separated impressions of digits. Traces of digits II and III are the shortest and the longest, respectively. Base of the digito-metatarsal pad of digit IV more proximal than trace of digit II. Variable divarication angle II-IV (35° in average). Round to oval phalangeal pads. Pointed marks of claws oriented outward on digits II and IV.

DESCRIPTION

The tracks are tridactyl, small-sized, longer than wide (L/W = 1.3-(1.6)-1.9), 8.6-(11.0)- 13.6 cm long and 5.2-(6.9)-8.0 cm wide ( Fig. 5 A-I; Table 2 ). The trace of digit III shows a long free part (L/D = 1.8-(2.4)-3). Impressions of digits are very well defined, thin, elongated and often separated. The impression of digit III is longer than traces of digits II and IV. Traces of digits II are the shortest. At the base of the trace of digit IV, the position of the digito-metatarsal pad is more proximal than that of digit II. The divarication angle II-IV is 24°-(35°)-46°. Round to oval phalangeal pads and pointed marks of claws are commonly very well marked. Marks of claws on the traces of digits II and IV are clearly oriented outward.

REMARKS

G. variabilis was erected by Lapparent & Montenat (1967) based on tracks from Le Veillon. This ichnospecies was abundantly reported in coeval tracksites from the Hettangian-Sinemurian deposits of the Causses Basin, in southern France ( Demathieu & Sciau 1992; Sciau 1992; Demathieu et al. 2002; Gand et al. 2007), as well as in northern Africa ( Bessedik et al. 2008). As mentioned by Lapparent & Montenat (1967), the morphology of G. cuneatus from the Connecticut is very close to that of G. variabilis from Le Veillon. Morphometric and statistical analyses made by Demathieu et al. (2002) and Gand et al. (2007) on G. variabilis from the Causses Basin confirmed that this last ichnospecies shows close morphological affinities with G. cuneatus ( Fig. 4 ). According to Weems (1992), G. cuneatus is a synonym of G. tenuis . However, this ichnospecies is smaller than G. variabilis from Le Veillon and from the Causses Basin; L = 6.4-6.6 cm; Fig. 4 ). Since the case of G. cuneatus remains unclear, Demathieu et al. (2002) did not synonymise G. variabilis with this ichnospecies. Considering G. variabilis as valid, Demathieu et al. (2002) erected the following diagnosis (translated from the French): “ Fingers are thin with well-marked phalangeal pads. The median digit is very elongated, the lateral digits are tightened and slightly tilted. There are three pads on digits III and IV, and two on digit II. There is no heel but digit IV is slightly prolonged posteriorly. Claws are elongated and sharp forming cuneiform marks. The ratio stride/pace corresponds to an elongated stride. The paces are arranged on a same line, the median digit in the axis of the trackway, its claw oriented inwards ”. The morphology of G. variabilis differs from the other Grallator ichnospecies from the United States ( Lull 1953). G. cursorius differs from G. variabilis in showing more slender tracks with a higher L/W ratio ( Fig. 4 ). G. gracilis is strongly smaller than G. variabilis whereas G. formosus is larger ( Fig. 4 ).

Figures

FIG. 5. — Grallator variabilis Lapparent & Montenat, 1967: A-C, plaster cast of the holotype, ULB-04C08_D, photograph (A), DEM and false-colour depth map (B) and interpretative sketch (C); D-F, paratype, ULB-04C05_A, photograph (D), DEM and false-colour depth map (E) and interpretative sketch (F); G-I, track ULB- 04C13_A, photograph (G), DEM and false-colour depth map (H) and interpretative sketch (I). Scale bars: 5 cm.

FIG. 4. — Footprints from Le Veillon compared to tridactyl tracks from the Early Jurassic of the Causses Basin (based on data from Demathieu et al. 2002; Moreau et al. 2021) and the Early Jurassic of the eastern United States (based on data from Weems 1992, 2019; Gand et al. 2018): A, bivariate diagram L vs (L–D)/D; B, bivariate diagram L vs L/W. L in metres.