Grallator olonensis 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 : 347-349

Grallator olonensis Lapparent & Montenat, 1967

( Fig. 3 )

Grallator olonensis Lapparent & Montenat, 1967: 14-16 , pl. III.1- 2, fig. 6.

SYNTYPES. — ULB-04D19_A1 to ULB-04D19_A13 . Lapparent & Montenat (1967) defined the “type” of G. olonensis as a surface bearing 25 footprints (surface “B1” in Lapparent & Montenat, 1967). A fragment of this surface is conserved in the Lapparent collection. It consists of the slab ULB-04D19_A ( Fig. 3A, B ) which bears thirteen tracks preserved as concave epireliefs. The slab ULB-04C12_A (“B1bis” in Lapparent & Montenat, 1967) corresponds to the convexe hyporeliefs of the slab ULB-04D19_A.

EXAMINED MATERIAL. — ULB-04C03_B , ULB-04C03_C , ULB-04C03_D , ULB-04C03_E , ULB-04C03_F , ULB-04C05_C , ULB-04C07_A , ULB-04C08_C , ULB-04C08_E , ULB-04C08_G , ULB-04C09_A , ULB-04C09_C , ULB-04C11_A , ULB-04C17_E , ULB-04C19_A , ULB-04D17_A , ULB-04D17_B , ULB-04D17_C , ULB-04D22_B .

DIAGNOSIS. —Tridactyl, very small-sized tracks (L = 3-5 cm), longer than wide and with a long projection of the trace of digit III (L/D = 2.1 in average). L/W ratio quite variable (1.2-2.5). Well-defined, very thin, elongated and often separated impressions of digits. Impression of digit III longer than traces of digits II and IV. Trace of digit III often curved distally. Traces of digits III and IV quite similar in length. Bases of digits II and IV proximally located at the same height. Variable but low divarication angle II-IV (35° in average). Tiny, oval and well-marked phalangeal pads. Tiny marks of acuminate claws.

DESCRIPTION

The material includes two trackways (T1-Go and T2-Go) preserved on the same slab and each composed of at least three consecutive footprints (ULB-04D19_A; Fig. 3A, B ). The longest trackway (T1-Go) is 43.5 cm long. The stride is 34.0-(36.7)- 39.5 cm long and the pace is 15.1-(17.8)- 20.5 cm long. Tracks form a narrow angle with the trackway midline. The material also includes several partial trackways (ULB-04C19_A, ULB-04D17_A, ULB-04D19_A). The tracks are tridactyl, very small-sized, 3.3-(4.3)- 4.9 cm long and 1.5-(2.5)- 3.3 cm wide ( Fig. 3 C-H; Table 2 ). Tracks are longer than wide and show a long projection of the traces of digit III. The L/W and L/D ratios are quite variable, being 1.2-(1.8)-2.5 and 1.8-(2.1)-2.4, respectively. Impressions of digits are well defined, very thin, elongated and often separated. The impression of digit III is longer than those of digits II and IV. The trace of digit III is often curved distally. The traces of digits II and IV are quite similar in length. Typically, the bases of digits II and IV are proximally located at the same height. The position of the digito-metatarsal pad of digit IV is rarely more proximal than that of digit II. The angle between digits II and IV is 24°-(34°)-44°. Phalangeal pads are tiny, oval and commonly well marked. Tracks commonly bear tiny marks of acuminate claws.

REMARKS

Based on material from Le Veillon, Lapparent & Montenat (1967) erected G. olonensis . Although they defined a type and describe the material, they did not erect a formal diagnosis. In France and throughout the world, G. olonensis was only reported from Le Veillon. Other very small-sized tridactyl tracks assigned to distinct ichnospecies of Grallator were described from Early Jurassic strata in Connecticut ( Lull 1953): G. cursorius Hitchcock, 1858 , G. gracilis Hitchcock, 1865 (synonym of G. tuberosus according to Weems 1992) and G. tenuis Hitchcock, 1858 . G. cursorius differs from G. olonensis in showing more slender, longer tracks (type material with L = 7.0- 7.9 cm according to Weems 1992) and a base of IV much more proximal than II ( Fig. 4 ). Although G. gracilis falls in the range size of G. olonensis , it differs from the latter in showing lower projection of III (type material with L/D = 2.6 according to Weems 1992; Fig. 4 ). G. tenuis differs from G. olonensis in showing longer tracks (type material with L = 6.4-6.6 cm according to Weems 1992) and the base of IV which is more proximal than II ( Fig. 4 ). G. olonensis is strongly smaller than G. cuneatus Hitchcock, 1858 , G. variabilis and G. formosus Hitchcock, 1858 .

Figures

FIG. 3. — Grallator olonensis Lapparent & Montenat,1967:A, B, slab ULB-04D19 bearing the trackway T1-Go, as well as T2-Go; photograph (A) and interpretative sketch (B); C-E, track 04D19_A_4 (syntype) of the trackway T1-Go, photograph (C), DEM and false-colour depth map (D) and interpretative sketch (E); F-H, ULB- 04C11_A_6, photograph (F), DEM and false-colour depth map (G) and interpretative sketch (H). Scale bars: A, B, 20 cm; C-H, 2 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.