Batrachopus gilberti ” 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 : 353-356

“ Batrachopus gilberti ” Lapparent & Montenat, 1967

( Fig. 7 )

Batrachopus gilberti Lapparent & Montenat, 1967: 11-13 , pl. I, fig. 4.

STATUS. — Subjective junior synonym of Batrachopus deweyi (Hitchcock, 1843) Hitchcock, 1845 .

EXAMINED MATERIAL. — Holotype: ULB-04C10_A . — Other specimens: ULB-04C02_B , ULB-04C04_A , ULB-04C09_B , ULB-04C10_E , ULB-04C14_A , ULB-04C14_C , ULB-04C14_D , ULB-04C14_F , ULB-04C14_G , ULB-04C14_H .

DESCRIPTION

The material includes a single trackway (ULB-04C10_E; Fig. 7 A-C) and several isolated pes/manus sets ( Fig. 7 D-L; Table 1 ).The trackway is narrow, 76 cm long and 8 cm wide and is composed of five consecutive pes/manus sets. Pes and manus track strides are 33.0-(35.5)-38.0 cm long. Pes track and manus track pace is 16.0-(17.7)- 19.5 cm long. Pes and manus tracks show a small positive rotation angle relative to the trackway axis (15-(20)-25°). Pes and manus tracks show a pronounced heteropody. Pes imprints are digitigrade and functionally tetradactyl, longer than wide to as wide as long (2.7-(3.2)- 3.9 cm long and 2.1-(3.0)- 3.8 cm wide; Table 1 ). The ratio PL /PW varies from 0.8 to 1.4. On pes tracks, impressions of digits are clearly marked, straight to curved, and short to quite elongated. Their apices are rounded and can sometimes bear tiny marks of claws. On pes tracks, impression of digit III is always the longest, and impression of digit I the smallest ( Fig. 7 D-L). Track of digit II is often the second longest. The divarication angle of digits I-IV strongly varies (36-(64)-82°).On pes tracks,the traces of digits II and III are the deepest. Pes tracks can show a short and large plantar-like impression.Manus tracks are pentadactyl and smaller than pes tracks, wider than long to as long as wide, 1.1-(1.8)- 2.4 cm long and 1.6-(1.8)- 2.2 mm wide (ML/MW = 0.7-(0.)-1.9). On manus tracks, digit imprints are very short and rounded. When preserved, digit V is oriented posteriorly.

REMARKS

These tracks were first ascribed to Cheirotherium (synonym of Chirotherium Kaup, 1835 ) by Bessonnat et al. (1965). This Triassic ichnogenus differs from the tracks from Le Veillon in showing larger tracks, pentadactyl pes tracks with a trace of digit V much more proximal than the group I-IV. Based on the following morphological characters, tracks from Le Veillon can be confidently ascribed to Batrachopus Hitchcock, 1845 (see the emended diagnosis in Olsen & Padian 1986): small quadrupedal trackway; pes tracks are digitigrade and functionally tetradactyl; digit III of the pes is the longest and digit I the shortest; pentadactyl and digitigrade manus, usually rotated so that digit II points forward, digit IV points laterally, and digit V points posteriorly; and manus much smaller than the pes.

The gross morphology of Batrachopus is close to those of Antipus Hitchcock, 1858 and Crocodylopodus Fuentes Vidarte & Meijide Calvo, 1999. Olsen & Padian (1986) considered Antipus as a subjective synonym of Batrachopus . However, Coombs (1996) and Lockley & Meyer (2004) rejected this proposition. According to Lockley & Meyer (2004), Antipus differs from Batrachopus in showing: much longer impressions of digits on the manus tracks; slender, tapering, quite curvated digit tracks with higher divarication angles and narrow claw impressions. The tracks from Le Veillon clearly differ from Antipus in showing shorter blunt-toed digits. Crocodylopodus differs from tracks of Le Veillon in showing more slender and divergent digits, less outward rotation of the pes and more outward rotation of the manus ( Lockley & Meyer 2004).

Based on ULB-04C10_ A, Lapparent & Montenat (1967) erected B. gilberti . The validity of the diverse ichnospecies of Batrachopus was strongly debated ( Olsen & Padian 1986; Rainforth 2005, 2007). In their revision of Batrachopus, Olsen & Padian (1986) considered only three valid ichnospecies for this ichnogenus and emended the diagnosis of each of them: B. deweyi (Hitchcock, 1843) Hitchcock, 1845 , B. parvulus ( Hitchcock, 1841) Hitchcock 1845 and B. dispar Lull, 1904 . Based on the following characters, the tracks from Le Veillon can be confidently ascribed to B. deweyi (see emended diagnosis in Olsen & Padian 1986): range size of pes length (between 2 and 6 cm); manus tracks about 75% of the length of the pes; on pes tracks, imprints of digit II and IV are sub-equal in length. We consider “ B. gilberti ” as a junior synonym of B. deweyi . B. parvulus (see emended diagnosis in Olsen & Padian (1986)) differs from tracks of Le Veillon in showing a very short impression of digit I on pes tracks. According to Rainforth (2005), B. parvulus can be synonymised with the type ichnospecies B. deweyi . B. dispar (see emended diagnosis in Olsen & Padian (1986)) differs from tracks of Le Veillon in showing a stronger heteropody. Rainforth (2005) considered three additional valid ichnospecies: B. bellus ( Hitchcock, 1858) Lull, 1904 , B. gracilior (Hitchcock, 1865) Lull, 1904 , B. gracilis (Hitchcock, 1848) Lull, 1904 . It contrasts with Olsen & Padian (1986) who subjectively synonymised these ichnospecies in B. deweyi . According to Rainforth (2005), B. bellus cannot be synonymised with B. deweyi because it differs from this ichnospecies in showing tridactyl pes (not concordant with the sketch of B. bellus in fig. 20.2B of Olsen & Padian (1986)). Rainforth (2007) tentatively synonymised B. gracilior and B. gracilis . Olsen & Padian (1986) explained that “apart from its smaller, longer pace and the lack of impressions of digit V in the pes” B. gracilis is identical to B. deweyi .

Figures

FIG. 7. — Batrachopus deweyi (Hitchcock,1843) Hitchcock, 1845: A-C, trackway ULB-04C10_E, photograph (A), DEM and false-colour depth map (B) and interpretative sketch (C); D-F, pes/manus set 04C10_A_1 (holotype of “B. gilberti” that is here invalidated), photograph (D), DEM and false-colour depth map (E) and interpretative sketch (F); G-I, pes/manus set 04C14_C, photograph (G), DEM and false-colour depth map (H) and interpretative sketch (I); J-L, pes/manus set 04C14_C, photograph (J), DEM and false-colour depth map (K) and interpretative sketch (L). Scale bars represent: A-C, 10 cm; D-L, 1 cm.