A new species of Diaulax Bell, 1863 (Brachyura: Dialucidae) in the Early Cretaceous of the Rosablanca Formation, Colombia

Abstract

The oldest record of the brachyuran Diaulax Bell, 1863 is based on the description of Diaulax rosablanca n. sp. from the middle part of the Rosablanca Formation (Early Cretaceous, early Valanginian, Department of Santander, Colombia). This is also the oldest record for fossil crustaceans from Colombia. The new species is represented by numerous specimens showing ontogenic variation in size and shape, with adults becoming larger and wider at the anterior portion of carapace. Differences with the other five species of the genus are subtle but sufficient to erect a new species. The associated ammonites Lissonia riveroi (Lisson, 1907), Acantholissonia gerthi (Weaver, 1931) and Raimondiceras sp. confirm an age corresponding to the middle part of the early Valanginian. The paleoenvironment is interpreted as a shallow, restricted low-energy carbonate platform or lagoon within well-oxygenated warm waters. The outcrop includes other decapod remains, too incomplete to offer a preliminary identification.Keywords: Brachyura, Dialucidae, Diaulax, ammonites, Valanginian, Colombia. (Lisson, 1907), Acantholissonia gerthi (Weaver, 1931 Resumen El registro más antiguo del género Diaulax Bell, 1863 se basa en la descripción de Diaulax rosablanca n. sp. de la parte media de la Formación Rosablanca (Cretácico Temprano, Valanginiano temprano, Departamento de Santander, Colombia). El reporte representa también el registro más antiguo de crustáceos fósiles para Colombia. La nueva especie está representada por numerosos especímenes que muestran variación ontogénica en tamaño y forma, con adultos que presentan un caparazón más grande y ancho en la porción anterior. Las diferencias con las otras cinco especies del género son sutiles pero suficientes para proponer una nueva especie. Los ammonites asociados Lissonia riveroi

Systematics and convergent evolution of multiple reef-associated Jurassic and Cretaceous crabs (Decapoda, Brachyura)

“…The number and types of changes are quite remarkable for crabs, however. For example, brachyuran carapaces usually become proportionally wider instead of longer through ontogeny as shown quantitatively (e.g., Barnes, 1968;Davidson and Marsden, 1987;Negreiros-Fransozo et al, 2003;Klompmaker et al, 2012Klompmaker et al, , 2015bGómez-Cruz et al, 2015; but see Finney and Abele, 1981, for the opposite). A change from a carapace with small tubercles to a combination of small and large tubercles is uncommon in crabs.…”

Magnetostratigraphy and magnetic properties of the Jurassic to Lower Cretaceous Girón Group (northern Andes, Colombia)

“…11B), are approximately valid and provide an improved chronologic control for Upper Jurassic to Lower Cretaceous strata in the northern Andes. Based on a Berriasian age for the Los Santos and Cumbre Formations (Cediel, 1968;Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989) and a Valanginian age for the Rosablanca Formation (Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989;Cooper et al, 1995;Sarmiento-Rojas et al, 2006;Gómez-Cruz et al, 2015;Rojas and Sandy, 2019), the compiled magnetic polarity succession of the Girón Group can be compared with the Geomagnetic Polarity Time Scale (GPTS) (Ogg et al, 2016). The age of the Girón Group is estimated to be between early Kimmeridgian and early .…”

“…11B), we assign the youngest (Bayona et al, 2006) Girón Formation (Bayona et al, 2006) Los Santos Formation Angostura del Río Lebrija Formation Girón Group Perijá Range (Gose et al, 2003) Perijá Range (Nova et al, 2012) Girón-Tibasosa Formation (Bayona et al, 2006 (Torsvik et al, 2012) Confidence interval (Kent and Irving, 2010) Unflattened paleolatitude Girón Group (7.0°N) Observed paleolatitude Girón Group (4.2°N) Perijá Range (Nova et al, 2012) Merida Andes (Castillo et al, 1991) Santa Marta Massif (Bayona et al, 2010) Bucaramanga (Bayona et al, 2006) Age (Ma) Berriasian Cumbre Fm (Cediel, 1968;Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989) and concordant contact (Laverde and Clavijo, 1985;Osorio-Afanador, 2016) with Valanginian Rosablanca Fm (Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989;Gomez-Cruz et al, 2015;Rojas and Sandy, 2019). possible age to the succession based on the Valanginian age for the Rosablanca Formation (Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989;Cooper et al, 1995;Sarmiento-Rojas et al, 2006;Gómez-Cruz et al, 2015;Rojas and Sandy, 2019) and thus a Berriasian age for the Los Santos Formation (Cediel, 1968;Etayo-Serna and Rodriguez, 1985;Etayo-Serna, 1989). In doing so, the observed magnetic polarity stratigraphic record can be compared with the Geomagnetic Polarity Time Scale (GPTS) (Ogg et al, 2016) for this time interval.…”

“…2). Gómez-Cruz et al (2015) and Rojas and Sandy (2019) suggested an early Valanginian age for the Rosablanca Formation based on crustaceans and brachiopod fauna (Fig. 2).…”

Geotourism in caves of Santander as a novel strategy for the protection of natural and cultural heritage associated to underground ecosystems

“…10 In the department of Santander there is a complex karstic system of approximately sixty-six (66) caverns associated with the Lower Cretaceous Rosablanca Formation, which consists of mudstones and marine limestones, [32][33][34] and is highly fossiliferous with an abundant fauna of ostracods, foraminifera, mollusks and echinoderms. 35 The Rosablanca Formation has a diverse richness of speleothems (zenithal, parietal and pavement) and fauna and flora, with geomorphological characteristics of slopes and steep escarpments, which visibly differentiate it from the adjacent formations. It differs from them, in addition, by its extensive valleys with relatively low topographies, high degree of dissolution and a remarkable jointing in surface, 36 generating lapiaz (karren), sinkholes, uvalas, poljes, blind valleys, chasms, among others.…”