Journal of Paleontology, 91(2), 2017, p. 230–244 Copyright © 2017, The Paleontological Society 0022-3360/16/0088-0906 doi: 10.1017/jpa.2016.153 Campanian and Maastrichtian plagioptychid rudists (Hippuritida, Bivalvia) of the Chiapas Central Depression, southern Mexico Jose Maria Pons,1 Enric Vicens,1 and Pedro García-Barrera2 1Departament de Geologia, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain 〈[email protected]〉, 〈[email protected]〉 2Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico 〈[email protected]〉 Abstract.—Plagioptychids are a conspicuous, although minor, component in uppermost Cretaceous rudist-bearing outcrops of the Caribbean Province, where other rudist families are more abundant and diverse. In the Chiapas Central Depression, the plagioptychid rudist fauna includes the following taxa: Plagioptychus antillarum (Douvillé) and Mitrocaprina sp. from the middle Campanian Suchiapa Formation, Plagioptychus muellerriedi Alencáster from the early Maastrichtian Ocozocoautla Formation, and Plagioptychus fragilis Chubb and Mitrocaprina tschoppi (Palmer) from the late Maastrichtian Angostura Formation. These five species are described in detail and some probable synonymies are discussed. Analysis of the literature on American plagioptychids reveals that the characters of too many taxa are still insufficiently known to attempt any thorough phylogenetic analysis. Other lines of evidence also seem to indicate that American Plagioptychidae diversity is probably higher than recognized today, which might result in a more significant difference to Plagioptychidae of the Mediterranean Tethys. Introduction complementary taxonomic data to the knowledge of this fauna. Pons et al. (2016a) provided the inventory of rudist occurrences In the American Tethys, families Antillocaprinidae, Hippuri- in the Upper Cretaceous of the Chiapas Central Depression, tidae (mainly multiple-fold), and Radiolitidae represent the related their location to a lithostratigraphic framework and maximal rudist abundance and diversity in the uppermost paleogeographic reconstruction, identified the successive Cretaceous rudist-bearing outcrops of the Caribbean Province, rudist assemblages, and discussed their age based on the while family Plagioptychidae is a minor, although conspi- co-occurrence of other fossils. Nevertheless, current and cuous, component (Table 1). Among the latter, the genus detailed systematic description of all these rudist species is yet Coralliochama is exclusive of the American Tethys, but its to be done. presence in the Caribbean region is doubted by some. The main aim of this paper is the identification and Mitrocaprina and Plagioptychus occur on both sides of the description of the plagioptychid rudist species from the Atlantic, although with different species at each side; the Medi- Campanian and Maastrichtian of this area, based mainly on the terranean species identified in America have been shown to be specimens collected by the authors, but also on the revision of erroneous. Several among the formerly established Caribbean fossil material from different museum collections, and taking plagioptychid species were based on only one or very few speci- into account the recent taxonomic and biostratigraphic advances mens and their morphological characters are not satisfactorily on the knowledge of the Caribbean Late Cretaceous rudist known. Thus, their identification based on new findings faunas. becomes problematic. Moreover, the precise biostratigraphy of some species remains uncertain because many Upper Geologic Setting Cretaceous Caribbean outcrops correspond to short stratigraphic sections without direct field correlation among them. Localities and stratigraphy.—Specimens for this study were Mexico presents a particularly long, largely continuous and collected at five localities of the Chiapas Central Depression extensive sedimentary record of the Upper Cretaceous in rudist- (Fig. 1) corresponding to three different lithostratigraphic units bearing platforms and deeper facies. Chiapas, in southern and to three of the rudist assemblages distinguished in Pons Mexico, was clearly related to the tectonic evolution of the et al. (2016a). Coincidence with Müllerried’s localities is also Caribbean, and its sedimentary and paleontological record is indicated when appropriated; although never published by much more continuous, or at least easier to interpret than that of Müllerried, numbers and names of his fossil localities were the islands. The Upper Cretaceous rudist fauna of Chiapas is registered in the collection, and subsequently used and indicated mainly known from Alencáster (1971) and older papers by in a map by Alencáster (1971). Müllerried (1931a, 1931b, 1933, 1934, 1936). More recent P-1316, road to Paraíso del Grijalva (92º38'15.5''W, papers (Alencáster and Michaud, 1991; Alencáster and Pons, 16º15'15.94''N) in the uppermost part of the Suchiapa Forma- 1992; García-Barrera et al., 1998; Mitchell, 2013) added some tion, corresponds to Müllerried’s locality 30 Vega del Paso, and 230 Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 29 Sep 2021 at 21:52:00, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/jpa.2016.153 Pons et al.—Campanian and Maastrichtian plagioptychid rudists of Chiapas 231 Table 1. American plagioptychid rudist taxa. Anatomical conventions.—AM = anterior myophore, AS = American Plagioptychidae attachment surface of the right valve, AT = anterior tooth, CT = central tooth, ISL = inner shell layer, LG = ligament Coralliochama White C. flourei Damestoy groove, LV = left valve, MC = main body cavity, OSL = outer C. gboehmi Böse shell layer, PAC = posterior accessory cavity, PM = posterior C. orcutti White = = Mitrocaprina Boehm myophore, PT posterior tooth, RV right valve. All trans- M. costaricaensis Pons et al. verse sections are figured in standard orientation, that is, in M. multicanaliculata Chubb M. palmeri MacGillavry adapical view and with the dorsal side up. In cross-section M. tschoppi (Palmer) drawings, the OSL is represented in black, RV’s ISL in pale Plagioptychus Matheron gray, and LV’s ISL in dark gray. Lateral views of specimens P. antillarum (Douvillé) P. fragilis Chubb with conjoined valves have been oriented with the RV’s P. jamaicensis (Whitfield) attachment area horizontal and down. P. minor Chubb P. muellerriedi Alencáster P. trechmanni Chubb Repositories and institutional abbreviations — = P. zansi Chubb . MNHNCu Museo Nacional de Historia Natural, Havana, Cuba; NMNH = Smithsonian, National Museum of Natural History, to the lower rudist assemblage, middle Campanian. Co-occurring New York, USA; UCBL-EM = École nationale supériéure rudists are: Alencasteria macrotubularis Mitchell, Stellacaprina? des Mines de Paris, Université Claude Bernard Lyon I, macgillavryi (Alencáster), Barrettia monilifera Woodward, Villeurbanne, France; UWIGM = University of West Indies Whitfieldiella gigas (Chubb), Parastroma trechmanni Chubb, Geology Museum, Mona, Kingston, Jamaica. Alencasterites mooretownensis (Trechmann), Bournonia bailei fi Chubb, and Thyrastylon? nicholasi (Whit eld). Systematic paleontology P-0743, Campo de Tiro (93º22'52.49''W, 16º46'55.41''N) and P-1358, Los Chamaquitos (93º22'44.9''W, 16º46' 35.58''N), both along the Cuesta NW of Ocozocoautla, in the Family Plagioptychidae Douvillé, 1888 upper part of the Ocozocoautla Formation, correspond to Genus Plagioptychus Matheron, 1842 Müllerried’s locality 6 Ocozocoautla, and to the middle rudist assemblage, early Maastrichtian. Co-occurring rudists Type species.—Plagioptychus paradoxus Matheron, 1842 are: Praebarrettia sparcilirata (Whitfield), Biradiolites [= Caprina aguilloni d’Orbigny, 1840, after Douvillé (1888)], cardenasensis Böse, Chiapasella radiolitiformis (Trechmann), from the Santonian? of Le Beausset, Bouches-du-Rhône, Huasteca ojanchalensis (Myers), Thyrastylon? nicholasi France. (Whitfield), and Trechmannites rudissimus (Trechmann). P-0748, Rancho la Peregrina (93º22'11.27''W, Plagioptychus antillarum (Douvillé, 1927) 16º48'38.12''N) and P-1369, Old Quarry (93º20'56.97''W, Figures 2.1–2.14, 3.1–3.5, 4.1 16º48'1.33''N), at 189 km and 195.3 km, respectively, road fi (Mex145) from Ocozocoautla to Las Choapas, in the Angostura 1927 Coralliochama antillarum Douvillé, p. 53, text- g. 2. fi – Formation, correspond to the upper assemblage, late 1933 Plagioptychus Toucasi; Müllerried, p. 9, text- gs. 6 11. fi Maastrichtian. Co-occurring rudists are: Antillocaprina non 1936 Plagioptychus antillarum; Rutten, p. 140, text- g. 4c, pugniformis (Palmer), Caenosarcolites oddsensis (Stephenson), d, f, j. Caenosarcolites scholaris Mitchell, Eosarcolites radiatus non 1937 Plagioptychus antillarum; MacGillavry, p. 156. Mitchell, Biradiolites cardenasensis Böse, Bournonia 1971 Plagioptychus cf. P. jamaicensis; Alencáster, p. 21, fi – fi fi = cancellata (Whitfield), and Thyrastylon adhaerens (Whitfield). pl. 1, gs. 1 4, pl. 17, g. 5. (pl. 1, g. 1 same specimen as in Müllerried, 1933, text-fig. 7) Materials and Methods 2016a Plagioptychus sp.; Pons et al., p. 217. Methods.—Specimens collected and used for this study are Types.—Holotype UCBL-EM-15901, figured in Douvillé maintained in the Paleontological Collections of the Universitat (1927, text-fig. 2), from Arroyo Hondo, Camagüey Autònoma de Barcelona (PUAB) and the Museo de Paleonto- Province, Cuba. logía, Facultad de Ciencias, Universidad Nacional Autónoma de México (FCMP).