FERNANDEZ mariela soledad
congresos y reuniones científicas
Parasitism in dinosaur clutches?
Salas de los Infantes, Burgos
Jornada; VI Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno. Salas de los Infantes, Burgos, España; 2013
Institución organizadora:
Universidad de Zaragoza, Universidad del País Vasco, Universidad de Salamanca, Museo de Dinosaurios (Salas de los Infantes, Burgos)
Northern Patagonian outcrops contain a number of excellent localities where Upper Cretaceous rocks are well exposed. Among these, the Allen Formation is dated as middle Campanian- early Maastrichtian in age, based on foraminifera presence (Ballent, 1980) and it is composed by a thick succession of sandstones and mudstones intercalated by carbonate and evaporitic rocks in its upper part (Salgado et al., 2007). In 2008, two clutch, ?a? containing 4 and ?b? containing 10 eggs, in the egg-level 4 at the Bajos de Santa Rosa locality were found (Salgado et al., 2007; Fernández 2013). These clutches were mapped with a 1m x 1m grid. For the very first time, we describe herein a new faveoloolithid clutch with an unexpected megaloolithid egg found in the middle of this clutch (Fig. 1.2 y 1.3). The Bajos de Santa Rosa clutch is unique and differs from the Sanagasta (La Rioja) eggs because in the latter locality the eggs are characterized by two different microstructure patterns probably caused by diagenetic processes (Grellet-Tinner & Fiorelli, 2010). Clutch ?a? contain 4 faveoloolithid eggsand lies 1.4 meters from the other group (Fig. 1.3) clutch ?b? contain 10 eggs, 9 of them belong to the filispherulitic morphotype, while one egg is attributed to the tubosferulitc morphotype (Fig. 1.3-letter D). Both clutches exhibit an irregular pattern of egg-laying. Clutch b consist in two levels of circular, randomly distributed eggs. The clutches have been worn out and it only preserves the bottom part of the laid eggs (most of them have preserved less than a half of their structure). The eggshells have an external compactituberculate ornamentation. The filispherulitic eggs have an average of 5 mm eggshell thickness while the tubospherulitic egg have 4.3 mm of thickness, Tipo 1 d (Fernández 2013). Usually, Megaloolithid clutches show a nesting structure (Chiappe, 1998, Coria et al., 2010, Vila et al. 2010a,b) but the studied clutch does not display it. On the contrary, the eggs are arranged in a circular and randomly distributed eggs without apparent sedimentary structure (Moratalla & Powell, 1994). We propose one possible explanations. It could be related to the resemblance to a Cuco-like reproductive behavior. The dinosaur would show a parasite behavior by laying its eggs in other nests. Externally, the eggs show a very similar morphology, just like extant birds with a similar behavior do. The biomineralization of eggshells and its well defined eggshell ultrastructure and texture arise from the control of crystal morphology and growth by the organic matrix and from proteins specific to the uterus and eggshell (ovocleidins and ovocalyxins) (Nys et al., 2004). In Río Negro province, few eggshells of this kind, Tipo 1 d, have been found. These eggshells appear always related to filisferulitics ones, but this is the first time that were found a partial egg inside of a filisferulitic clutch. Further investigation on extant avian and reptile reproductive behaviors, and more prospecting work is necessary in order to understand these real relationship involved in this clutch. Keywords: Nesting, dinosaurs, eggshell microstructure, Upper Cretaceous, Santa Rosa, Argentina References Ballent, S.C. (1980): Ostrácodos de ambiente salobre de la Formación Allen (Cretácico Superior) en la Provincia de Río Negro (República Argentina). Ameghiniana 17, 67-82. Chiappe, L.M., Schmitt, J.G., Jackson, F.D., Garrido, A., Dingus, L., Grellet-Tinner, G. (2000): Nest structure for Sauropods: Sedimentary Criteria for recognition of dinosaur nestin trace. Palaios v.19, p. 89-95. Chiappe, L.M., Schmitt, J.G., Jackson, F.D., Garrido, A., Dingus, L., Grellet-Tinner, G. (2004): Nest structure for sauropods: sedimentary criteria for recognition of dinosaur nesting traces. Palaios 19, 89-95. Coria, R.A., Salgado, L. and Chiappe, L.M. (2010): Multiple dinosaur egg-shell ocurrente in a Upper Cretaceous nesting site from Patagonia. Ameghinana 47(1), 107-110. Fernández, M.S. (2013): Análisis de cáscaras de huevos de dinosaurios de la Formación Allen, Cretácico Superior de Río Negro (Campaniano-Maastrichtiano): utilidades de los macrocaracteres de interés parataxonómico. Ameghiniana 50 (1), 79 ? 97. Grellet-Tinner, G. and Fiorelli, L.E. (2010): A new Argentinean nesting site showing neosauropod dinosaur reproduction in a Cretaceous hydrothermal environment. 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