Boletín de la Sociedad Geológica Mexicana ISSN: 1405-3322 Sociedad Geológica Mexicana, A.C. Rodríguez-de la Rosa, Rubén A.; Velasco-de León, María Patricia; Arellano-Gil, Javier; Lozano-Carmona, Diego Enrique Middle Jurassic ankylosaur tracks from Mexico Boletín de la Sociedad Geológica Mexicana, vol. 70, no. 2, 2018, May-August, pp. 379-395 Sociedad Geológica Mexicana, A.C. DOI: https://doi.org/10.18268/BSGM2018v70n2a8 Available in: https://www.redalyc.org/articulo.oa?id=94362562009 How to cite Complete issue Scientific Information System Redalyc More information about this article Network of Scientific Journals from Latin America and the Caribbean, Spain and Journal's webpage in redalyc.org Portugal Project academic non-profit, developed under the open access initiative Boletín de la Sociedad Geológica Mexicana / 2018 / 379 Middle Jurassic ankylosaur tracks from Mexico Rubén A. Rodríguez-de la Rosa, María Patricia Velasco-de León, Javier Arellano-Gil, Diego Enrique Lozano-Carmona ABSTRACT Rubén A. Rodríguez-de la Rosa ABSTRACT RESUMEN [email protected] Unidad Académica de Ciencias Biológicas, Unidad Académica de Ciencias de la Tierra, A track-bearing locality in one of the shores Una localidad icnofosilífera en una de las orillas del Universidad Autónoma de Zacatecas, Campus of the Ñumí River, near the City of Tlaxiaco, Río Ñumí en las cercanías de la Ciudad de Tlaxiaco, II, Calzada Solidaridad, esq. Paseo de la Bufa northwestern Oaxaca, southern Mexico, noroeste de Oaxaca, al sur de México, conserva las s/n, C.P. 98060, Zacatecas, Mexico. preserves the footprints of sauropod and huellas de dinosaurios saurópodos y terópodos; esta theropod dinosaurs; it is located within the se localiza dentro de la secuencia estratigráfica de stratigraphic sequence of the Zorrillo-Taberna María Patricia Velasco-de León la Formación Zorrillo-Taberna Indiferenciadas, de Indiferenciadas Formation, of Middle Jurassic Diego Enrique Lozano-Carmona edad Jurásico Medio (Bajociano). Se identificó un Facultad de Estudios Superiores Zaragoza, (Bajocian) age. A well-preserved manus-pes conjunto de pie-mano de afinidad anquilosauriana Universidad Nacional Autónoma de México, set of ankylosaurian affinity (Tetrapodosaurus) is (Tetrapodosaurus) en un bloque de roca procedente de Campus II, Batalla 5 de mayo s/n esquina preserved on a rock block from this formation. esta formación; las huellas se encuentran conservadas Fuerte de Loreto, Ejército de Oriente, Iztapa- These tracks are preserved as convex hypore- como hiporrelieves convexos. El pie es tetradáctilo, liefs. The pes impression is tetradactyl, with lapa, C.P. 09230, CDMX, Mexico. con las puntas de los dedos curvadas ventralmente, ventrally curved toe tips, suggesting that these sugiriendo que éstas fueron impresas profundamente were deeply impressed in the sediment. Manus Javier Arellano-Gil en el sedimento. La mano es pentadáctila, con dedos impression is pentadactyl, with short and blunt Facultad de Ingeniería, Universidad Nacional pequeños y romos. Una estructura curvada, conser- Autónoma de México, Av. Universidad 3000, digits. A curved structure preserved together with these footprints is herein interpreted vada junto a las huellas, es interpretada aquí como Ciudad Universitaria, Coyoacán C.P. 04510, un arrastre de cola. El estrato original de procedencia CDMX, Mexico. to be a tail drag. The stratigraphic unit from whence this block came was identified and two del bloque portador de las huellas, fue identificado additional ankylosaurian tracks, were found y dos huellas adicionales de anquilosaurios fueron preserved in situ as natural sandstone casts. encontradas in situ, conservadas como rellenos natu- An isolated handprint, has the same features rales de arenisca. Un relleno natural de una mano fue that fit the ankylosaurian hand morphology; encontrado de forma aislada; éste presenta los mismos however, some features such as a medio-lateral caracteres morfológicos de la mano anquilosauriana; concavity are indicative of the presence of a sin embargo, algunas características como la con- well-developed palmar pad, and could suggest cavidad medio lateral de la zona palmar indica la the functional mechanics of the ankylosaurian presencia de un cojinete, y podría sugerir la mecánica manus. The Zorrillo-Taberna Indiferenciadas funcional de la mano anquilosauriana. La Formación Formation is a coal-bearing formation; after Zorrillo-Taberna Indiferenciadas es una formación the global record, ankylosaur footprints are con estratos de carbón; en otras secuencias sedimen- concentrated in coal-bearing and floodplain tarias las huellas de anquilosaurios se concentran en facies, thus suggesting, that at least the North facies aluviales y portadoras de carbón, esto sugiere American Ankylosauria were adapted to sim- que al menos los Ankylosauria norteamericanos ilar paleoecological conditions from Middle estaban adaptados a condiciones paleoecológicas simi- Jurassic to Early Cretaceous times. It represents lares, desde el Jurásico Medio al Cretácico Temprano. the second report of ankylosaurian tracks from Este trabajo representa el segundo reporte de huellas de Mexico and the southernmost record of the anquilosaurios en México, y el más sureño del icnogé- ichnogenus Tetrapodosaurus in North America. nero Tetrapodosaurus en Norte América; sugiriendo un In this way, it suggests a geographic continuum continuum geográfico en el registro de Ankylosauria, in the record of the Ankylosauria to southern hasta el sur de Norte América durante el Jurásico North America during Middle Jurassic times. Medio. Además, son los icnofósiles más antiguos de With their Middle Jurassic age, these footprints anquilosaurios conocidos hasta este momento. BOL. SOC. GEOL. MEX. 2018 represent the oldest ankylosaurian ichnofossils VOL. 70 NO. 2 known to date. P. 379 ‒ 395 Palabras clave: Ankylosauria, http://dx.doi.org/10.18268/BSGM2018v70n2a8 Keywords: Ankylosauria, Tetra Tetrapodosaurus, Icnología, Jurá podosaurus, Ichnology, Middle sico Medio, Oaxaca, México. Manuscript received: March 21, 2017. Jurassic, Oaxaca, Mexico. Corrected manuscript received: July 19, 2017. Manuscript accepted: September 29, 2017. Middle Jurassic ankylosaur tracks from Mexico 380 / Boletín de la Sociedad Geológica Mexicana / 2018 1. Introduction “Ankylosauripus” and/or “Tetrapodosauripus” (Kap- pus et al., 2011: 281), when both names are inex- During paleontological fieldwork in search for istent. Therefore, the purpose of this paper is to paleobotanical sites, one of the authors (MPVL) report these tracks, noting that due to their Middle INTRODUCTION / GEOLOGICAL SETTING found a locality bearing dinosaur footprints in the Jurassic age, they represent the oldest ankylosauri- Ñumí River, near the City of Tlaxiaco, northwest- an ichnofossils known to date. ern Oaxaca, in southern Mexico (figures 1, 2). The locality preserves the footprints of sauropod and theropod dinosaurs (figures 3, 4) (Lozano-Carmo- 2. Geological setting na, 2012; Rodríguez-de la Rosa, 2014, 2015; Ro- dríguez-de la Rosa et al., 2014); it is located within The study area is located in the Tlaxiaco Basin, the stratigraphic sequence of the Zorrillo-Taber- which is placed in the boundary between the na Indiferenciadas Formation, of Middle Jurassic Zapoteco and Mixteco terrains (Dávalos-Álva- age (Carrasco-Ramírez, 1981; González-Torres, rez, 2006); both terrains in contact along the 1989; Corro-Ortiz and Ruíz-González, 2011). Caltepec lateral fault (Sedlock et al., 1993). The This geological formation preserves a notable re- late Aalenian (early Middle Jurassic) Ñumí Con- cord of fossil plants of Bennettitales, Caytoniales, glomerate (or Cualac Conglomerate) is the old- Equisetales, Filicales, conifers and Ginkgoales est unit within the local stratigraphic column (Silva-Pineda et al., 2007; Lozano-Carmona, 2012; (Corro-Ortiz and Ruíz-González, 2011). The Velasco-de León et al., 2013; Velasco-de León et Tecocoyunca Group is a very fossiliferous rich al., 2015; Lozano-Carmona and Velasco-de León, unit overlying the Ñumí Conglomerate, with an 2016). The study of this dinosaur tracksite start- age that ranges from the Bajocian to Callovian ed in a consecutive field season; however, it was (Erben, 1956; Sandoval and Westermann, 1986; noted that a fallen rock block in front of the main Lozano-Carmona and Velasco-de León, 2016). track-bearing surface (Figure 4) contained dino- According to Carrasco-Ramírez (1981) the Teco- saur tracks, preserved as natural casts in its un- coyunca Group is composed of four formations derside. Among these tracks is a well-preserved that, in ascending stratigraphic order are, the Zor- manus-pes set of an ankylosaurian dinosaur. rillo-Taberna Indiferanciadas Formation, Simón, Ankylosaurian remains have been collected in Otatera, and Yucuñuti formations. Subsequently, Mexico, mainly from northern states such as Baja González-Torres (1989) divided the Tecocoyun- California, Chihuahua and Coahuila. Among the ca Group into two subgroups: a lower unit com- most common ankylosaur remains found in Mexi- prising the Zorrillo-Taberna Indiferenciadas and co are teeth and osteoderms, an isolated vertebra, Simón formations, and an upper unit comprising and a few limb elements have also been found the Otatera and Yucuñuti formations (Figure 5). (Rivera-Sylva and Espinosa-Chávez, 2006; Ri- The youngest Jurassic unit outcropping in the area vera-Sylva et al., 2011; Martínez-Díaz and Mon- corresponds to a marine environment unit named tellano-Ballesteros, 2011). Kappus et