Redescription of the Extinct Species Callopistes bicuspidatus Chani, 1976 (Squamata, Teiidae)
We redescribe the holotype and only known material of the extinct teiid lizard Callopistes bicuspidatus Chani, 1976, from the late Miocene–early Pliocene of the Atlantic coast of Argentina. It would constitute a fossil record of the genus outside the present range of distribution restricted west of the Andes, but the characters used in the original description for the systematic assignation have had little attention and have been questioned in part. In this study, we confirm the generic assignation of these remains (as well as the validity of the species), based on characters different from those used in the original description. We also recognize many characters shared by Callopistes and the rest of the Tupinambinae teiids indicating the affinity of the genus to this subfamily. The paleoenvironmental conditions inferred from the accompanying vertebrate fauna for the late Miocene–early Pliocene of the fossil locality indicate that C. bicuspidatus exploited different environmental conditions than the extant species of the genus, especially regarding humidity and water availability. En este trabajo redescribimos el holotipo y únicos restos conocidos del lagarto teido Callopistes bicuspidatus Chani, 1976, del Mioceno tardío–Plioceno temprano de la costa atlántica Argentina. Constituiría un registro fósil del género fuera de su actual rango de distribución, el cual se encuentra restringido al oeste de los Andes. Sin embargo, poca atención han recibido los caracteres utilizados para su asignación sistemática original, algunos de los cuales han sido cuestionados. En este estudio reconocemos distintos caracteres que confirman su asignación genérica y su validez específica. La mayoría de estos caracteres no fueron reconocidos en la descripción original. También reconocimos caracteres compartidos entre Callopistes y los restantes Tupinambinae indicando la afinidad del género con esta subfamilia. Las condiciones paleoambientales para el Mioceno tardío–Plioceno temprano de la costa Atlántica inferidas a partir de la fauna acompañante de vertebrados indican que C. bicuspidatus explotaba ambientes distintos a los de sus congéneres actuales, en particular en lo relacionado a la disponibilidad de agua y humedad.Abstract
Resumen
Location map of the Farola Monte Hermoso locality (38°58′S, 61°41′W), Argentina. Buenos Aires province in gray; star, Farola Monte Hermoso.
Skull of Callopistes maculatus. Skull MNHNC 4112 in dorsal (A) and lateral (B) views; parietal and supratemporals MNHNC 4113 in ventral view (C); braincase MNHNC 4113 in dorsal view (D); right hemimandible (MNHNC 4113) in medial (E) and lateral (F) views; pterygoid in ventral view (G). Abbreviations: av.d, anteroventral depression of the pterygoid; P.f, parietal fossa; poF.p, postfrontal protuberance; P.p.b, parietal plateau border; sc.f, subcoronoid fenestra (the bone exposed is the surangular); sO.g, supraoccipital groove.
Skull of Callopistes bicuspidatus Chani (1976) from the late Miocene–early Pliocene of Argentina. PVL 4618-1 in lateral (A), ventral (B), and medial (C) views. Abbreviations: c.t, crista transversalis; Ju, jugal; f.p, frontal process; p.b; posterior buttress; pF, prefrontal; pf.p, prefrontal process; Pal, palatine; pal.p, palatine process; mx.p, maxillary process of the palatine; nl.r, nasolacrimal ridge; V.a.f, vomer articulation facet.
Skull elements of Callopistes bicuspidatus Chani (1976) from the late Miocene–early Pliocene of Argentina. Frontal (PVL 4618-2) in dorsal (A), lateral (B), and ventral (C) views; postorbital and postfrontal (PVL 4618-3) in lateral (D) and medial (E) views. Abbreviations: al.p, anterolateral process; am.p, anteromedial process; d.p, descendant process; S.a.f, squamosal articulation facet; f.t, frontal tab; J.a.f, jugal articulation facet; l.p, lateral process; p.f, parietal fossa; poF, postfrontal; poF.p, postfrontal protuberance; pm.p, posteromedial process, poO, postorbital.
Hemimandible elements of Callopistes bicuspidatus Chani (1976) from the late Miocene–early Pliocene of Argentina. Right dentary (PVL 4618-5) in medial view (A); left hemimandible (PVL 4618-5) in lateral (B) and medial (C) views. Abbreviations: a.f, anterior surangular foramen; al.f, alveolar foramen; a.mh.f, anterior mylohyoid foramen; An, angular; Co, coronoid; Mc, Meckel's canal; m.f, mental foramina; S.a.f, splenial articulation facet; S, splenial; Su, surangular; sy, symphysis.
Maxillae length vs. height relation of different Teiidae genera. In blue, Teiinae (square, Ameiva; triangle, Cnemidophorus; diamond, Aspidoscelis; circle, Teius; dash, Kentropyx); in green, Tupinambinae (triangle, Crocodilurus; circle, Callopistes; diamond, Tupinambis; square, Dracaena); and red circle, Callopistes bicsupidatus.
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