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Actinopterygii: Teleostei

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Actinopterygii: Teleostei Boletín de la Sociedad Geológica Mexicana / 2019 / 831 Short note The first occurrence of a freshwater percomorph fish (Actinopterygii: Teleostei) in the Ixtapa Formation (Miocene), Chiapas, southeastern Mexico Kleyton M. Cantalice, Jesús Alvarado-Ortega ABSTRACT Kleyton M. Cantalice ABSTRACT RESUMEN [email protected] Jesús Alvarado-Ortega Instituto de Geología, Universidad Nacional In this paper we describe a single and Aquí se describe un único e incompleto pez Autónoma de México, Circuito de la incomplete fossil fish specimen col- Investigación S/N, Ciudad Universitaria, fósil colectado en los depósitos fluvio-lacus- lected in the Ixtapa fossiliferous site, Coyoacán, CDMX, 04510, México. tres del sitio fosilífero de Ixtapa, localizado located at the Ixtapa municipality, en el Municipio del mismo nombre, cerca de near Tuxtla Gutiérrez City, Chiapas, southeastern Mexico. The Ixtapa site la ciudad de Tuxtla Gutiérrez, Chiapas, en contains ashfall sediments deposited el sureste de México. En este sitio se exponen under fluvio-lacustrine conditions, cenizas del Mioceno superior pertenecientes which belong to the Upper Miocene a la Formación Ixtapa. La asociación fósil continental sediments of the Ixtapa recuperada en esta formación incluye una Formation. The fossil assemblage amplia diversidad de hojas de angiospermas, previously recovered in this formation algas carofitas, gasterópodos acuáticos y includes abundant angiosperm leaves, también registros de mamíferos terrestres charophytes, and aquatic gastro- cómo, por ejemplo, caballos, rinocerontes y pods, as well as terrestrial mammals including horses, rhinoceros, and proboscidios. Este es el primer registro de un proboscideans. This first fossil fish pez fósil en la localidad Ixtapa y es consi- from Ixtapa is considered a member derado como un miembro de la Subdivisión of the Subdivision Percomorphaceae Percomorphaceae por la presencia de espinas because its dorsal and anal fins have no-segmentadas en las aletas dorsal y anal, unsegmented spines and its caudal además de la ausencia de centro ural 2 en fin lacks the ural centrum 2. The el esqueleto caudal. La imperfecta preser- imperfect preservation of this spec- vación no permite una determinación taxo- imen impedes a taxonomical deter- nómica más precisa, sin embargo, este fósil mination at species level; however, this fossil reveals the occurrence of desvela la presencia de peces percomorfos primary freshwater percomorphs in dulceacuícolas en el sur de México desde el the southern end of Mexico since the Mioceno-Plioceno. Por lo tanto, el presente Miocene–Pliocene. Hence, the pres- descubrimiento constituye un complemento ent discovery constitutes an import- importante para comprender la diversidad de ant complement to understand the BOL. SOC. GEOL. MEX. 2019 peces dulceacuícolas en esta región a través freshwater fish diversity in this region VOL. 71 NO. 3 del tiempo. P. 831 ‒ 839 through time. http://dx.doi.org/10.18268/BSGM2019v71n3a12 Keywords: Percomorph, Fresh- Palabras clave: Percomorfo, Manuscript received: April 9, 2018. water, Cenozoic, Ixtapa, Chi- Dulceacuícola, Cenozoico, Ixta- Corrected manuscript received: May 5, 2018. Manuscript accepted: May 11, 2018. apas, Mexico. pa, Chiapas, México. Freshwater percomorph fish of Ixtapa 832 / Boletín de la Sociedad Geológica Mexicana / 2019 1. Introduction fish, which despite not being well preserved, could be an important clue to understand the paleobio- The Ixtapa fossiliferous site is located at the coor- geographic patterns of the percomorph fishes in dinates 16°48ʹ42.31ʺN, 92°54ʹ33.58ʺW, 28 km east the extreme south of North and Central America. INTRODUCTION / MATERIAL AND METHODS from Tuxtla Gutiérrez City. This site is exposed at This fossil also represents the oldest primary fresh- the east side of the Soyaló-Ixtapa highway (State water percomorph fish known in Mexico. Road 195), next to the bridge that goes through the Río Hondo, one-kilometer North from down- town Ixtapa (Figure 1). 2. Material and methods The Ixtapa Formation is Late Miocene in age and is deposited in low-energy fluvio-lacustrine The specimen described here is deposited in the conditions, over the Middle Miocene continen- National Collection of Paleontology of Mexico tal sandstones of the Coyolar Formation and (Colección Nacional de Paleontología), at the the Eocene marine limestones of the El Bosque Autonomous National University of Mexico Formation. The Ixtapa Formation is covered by (Universidad Nacional Autónoma de México). the Pliocene–Pleistocene volcanic deposits of the This fossil fish preserves partially both part and Punta de Llano Formation (e.g., Ferrusquía-Vil- counterpart and contains only undefined isolated lafranca, 1996; Martínez-Amador et al., 2004; bones on the head. Furthermore, it lacks the ante- Hernández-Villalba et al., 2013). rior portion of the vertebral column, the pectoral The fossil-bearing rocks of the Ixtapa site belong and pelvic fins, and the tip of the dorsal, anal, and to the volcano-sedimentary sequence known as the caudal fins. Ixtapa Formation, an Upper Miocene geological The olive gray sediments, formed by volcanic unit which was originally named by González-Al- tuff rocks, cover the skeleton. The small patches varado (1965). According to Ferrusquía-Villa- of rock matrix over many parts of the body were franca (1996), the Ixtapa Formation is a sequence mechanically removed with thin excavators and of pyroclastic materials interbedded with calcite needles, and chemically removed with punctual pebbly gravels and tuffs. Tuffs are more frequent brushstrokes and 5% sulfamic acid. To obtain bet- towards the base of the formation, forming part of ter contrast between the bones and the sediment, interbedded layers of conglomerates, sandstones, the specimen was coated with magnesium smoke. and clays, where crystalline and calcareous con- A total of 11 anatomic measures and 10 counts glomerates are sporadically present. compose the morphometric and meristic data Martínez-Hernández (1992) reported that, at of the specimen. The bone nomenclature follows the base of the formation, the thick and thin the classic works on acanthomorph osteology (e.g., well-stratified tuff–shales bear carbonized Stiassny, 1986; Johnson and Patterson, 1993). The remains of leaves and stems of angiosperms, interpretation from the Upper Miocene to the as well as gastropods and charophytes oogonia; Lower Pliocene of the Ixtapa Formation follows whereas above, dark-gray conglomerates preserve previous paleontological and geological studies remains of silicified wood and mammal remains, of the area (i.e., Martínez-Hernández, 1992; Fer- such as teeth of horses, rhinoceros, and probos- rusquía-Villafranca, 1996; Hernández-Villalba et cideans (e.g., Daily and Durham, 1966; Menez- al., 2013). es-Rocha, 2001; Hernández-Villalba et al., 2013). All the taxa used for comparison belong to the The most abundant fossils at the base of the Ixtapa same institution of the species here described Formation are carbonized leaves; therefore, the and include the Paleocene species Eekaulostomus finding of a fish in this unit was unexpected. The cuevasae Cantalice and Alvarado-Ortega, 2016 aim of the present paper is to describe this fossil (IGM 4716); Kelemejtubus castroi Cantalice and Freshwater percomorph fish of Ixtapa Boletín de la Sociedad Geológica Mexicana / 2019 / 833 MATERIAL AND METHODS / RESULTS Figure 1 Map of the State of Chiapas, showing the Ixtapa fossiliferous site (black and white circle) and nearby municipalities (black circles). Modified of Hernández-Villalba et al. (2013). Alvarado-Ortega, 2015 (IGM 4864-67, 4908-09); (= PERCOMORPHACEA, sensu Paleoserranus lakamhae Cantalice, Alvarado-Or- Wiley and Johnson, 2010) tega, and Alaniz-Galvan, 2018 (IGM 9469-9477; Family INCERTAE SEDIS IHNFG 6876), from Chiapas State; Tapatia occi- Gen. and sp. undetermined dentalis Álvarez and Arriola-Longoria, 1972 (IGM 7966), from the Pliocene of Barranca de Santa Referred specimen. IGM 7968, incomplete specimen Rosa locality, at Amatitlán, Jalisco State; and the preserved in part and counterpart. The anterior dubious cyprinodontiform (IGM 7967; see discus- third (including the head, pectoral, and pelvic sion below) of Oligocene outcrops of Ahuehuetes, fins), as well as the antero-ventral portion of the at Tepexi de Rodriguez, Puebla (Espinosa-Pérez et body, are not preserved (Figure 2). The posterior al., 1991). extremity of the rays that composes the dorsal, anal, and caudal fin is also lost. Type locality and horizon. Ixtapa locality, Upper 3. Results Miocene tuff sediments at the base of the Ixtapa Formation (Ferrusquía-Villafranca, 1996), Ixtapa 3.1. SYSTEMATIC PALEONTOLOGY Municipality, Chiapas, Mexico. Morphological sources of taxonomic characters. This fossil Class ACTINOPTERYGII Woodward, 1891 fish belongs to the Subsection Acanthomorphata Infraclass TELEOSTEI Müller, 1845 (or only acanthomorphs) because it has true Subsection ACANTHOMORPHATA unsegmented spines before soft rays on both dorsal (sensu Wiley and Johnson, 2010) and anal fins. Inside acanthomorphs, the species Subdivision PERCOMORPHACEAE here described belongs to the Subdivision Perco- Freshwater percomorph fish of Ixtapa 834 / Boletín de la Sociedad Geológica Mexicana / 2019 morphaceae to have autogenous haemal spine on Axial skeleton. The anterior portion of the axial the second preural centrum (PU2); five autogenous skeleton is not preserved. No prezygapophysis hypural plates on the caudal skeleton; and the or apophysis is observed.
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