Paramacellodus sp.

Allain, Ronan, Vullo, Romain, Rozada, Lee, Anquetin, Jérémy, Bourgeais, Renaud, Goedert, Jean, Lasseron, Maxime, Martin, Jeremy E., Pérez-García, Adán, Fabrègues, Claire Peyre De, Royo-Torres, Rafael, Augier, Dominique & Bailly, Gilles, 2022, Vertebrate paleobiodiversity of the Early Cretaceous (Berriasian) Angeac-Charente Lagerstätte (southwestern France): implications for continental faunal turnover at the J / K boundary, Geodiversitas 44 (25), pp. 683-752 : 702

Paramacellodus sp.

( Fig. 15 A-C)

DESCRIPTION

ANG M-20 ( Fig. 15 A-C) is a jaw fragment bearing two closely spaced teeth, with the anterior tooth slightly larger than the posterior. Curvature of the teeth suggests that this fragment might come from a premaxilla or the anterior part of a dentary. Tooth implantation is pleurodont. Both tooth crowns are gently recurved and twisted so that the lingual face is slightly inclined posteriorly. The anterior marginal zone has a shoulder or angulus mesialis, following the terminology of Richter (1994). A similar shoulder, that would represent the angulus distalis, is absent in the distal marginal zone. The labial face is cambered and smooth whereas the lingual face is ornamented with longitudinal ridges, which are more numerous in the anterior tooth. The sharp and pointed tooth apex shows two small cusps (i.e., cuspis labialis and cuspis lingualis) closely adpressed and linked by a short carina (i.e., carina intercuspidalis). The ornamented central zone of the lingual face (i.e., pars furcata), delineated by long striae dominantes, is moderately wide. In lingual view, several foramina are present between the columnar roots of the teeth ( Fig. 15A ). The tooth crown shape (which is twisted with an acute apex and shows an angulus mesialis) and ornamentation combined with the presence of cuspis labialis and cuspis lingualis united by a short carina intercuspidalis is consistent with referral of ANG M-20 to Paramacellodus (Broschinski & Sigogneau-Russell 1996; Evans & Searle 2002). The other closely related genus Parasaurillus has more pointed crowns, no angulus mesialis, and longer lingual ridges ( Evans & Searle 2002). Three species of Paramacellodus are known to date: P. oweni from the Late Jurassic of U.S. A and the Berriasian of England, P. marocensis from the Tithonian and/or Berriasian of Morocco, and P. sinuosus from the Barremian of Spain ( Hoffstetter 1967; Richter 1994; Broschinski & Sigogneau-Russell 1996; Evans & Chure 1998; Evans & Searle 2002). A fourth species from the late Early Cretaceous (Aptian-Albian) of the United States, characterized by a welldeveloped cuspule on the anterior carina, was tentatively referred to Paramacellodus (cf. P. keebleri ; Nydam & Cifelli 2002). Other occurrences tentatively referred to Paramacellodus have been reported from the Bathonian-Barremian of Europe, North America, Asia and Africa ( Evans & Searle 2002). The Angeac-Charente form might belong to P. oweni or P. marocensis ; however, pending the discovery of additional material, we refer it to Paramacellodus sp.

Numerous osteoderms ( Fig. 15 D-F) have been collected from Angeac-Charente. These elongated plate-like elements are subrectangular and show more or less numerous pits visible on their external surface. A low, longitudinal ridge can be present, either in the midline or displaced laterally. The unornamented imbrication shelf is variably developed. These isolated osteoderms are morphologically consistent with scincomorph osteoderms (e.g., Krause et al. 2003; Nydam et al. 2013), including those referred to paramacellodids (e.g., Hoffstetter 1967; Richter 1994; Broschinski & Sigogneau-Russell 1996; Nydam & Cifelli 2002; Sweetman & Evans 2011).

Figures

FIG. 15. — Scincomorph lizard remains from Angeac-Charente: A-C, fragment of left dentary of cf. Paramacellodus sp. (ANG M-20) in lingual (A), labial (B) and distal (C) views; D-F, osteoderms of Scincomorpha indet., ANG M-46 (D), ANG M-49 (E), ANG M-58 (F) in dorsal view. Scale bar: 500 µm.