New teeth of a basal Macronarian (Sauropoda) from the Jurassic-Cretaceous transition of Spain

In this work, a dentary, and several teeth from the Valdepalazuelos-Tenadas del Carrascal site (Burgos, Spain) are studied. Geologically,this site is situatedat the base of the Rupelo Formation (Cuenca de Cameros), of Tithonian-Berriasian age. This formation has been interpreted as lacustrine-palustrine deposits with low gradient margins and with periodic changes in the water level. MDS-VPCR,851 is a fragment of the rostral symphyseal zone of a right dentary, a robust bone with a rostral ridge on its lingual surface, large diameter foramina on the lingual surface, a wide Meckelian canal extending from the rostroventral margin, semicircular symphysis arranged rostrolingually, and with two alveoli preserving two erupting teetheach. Although the functional teeth have not been preserved, each alveolus could contain one active tooth and at least two replacement teeth. Eight maxillary and mandibular teeth are described, with a spatulate crown, a rough enamel surface, a D-shaped croos-section, and a very marked cingulum. The dentary and teeth from this site have evident differences with those of other taxa and specimens described in the Kimmeridgian-Berriasian of the Iberian Peninsula. Its greatest similarities are with Camarasaurus, but in the specimens from Valdepalazuelos there are characters that seem to be unique and differ from that taxon. Consequently. the specimens described here are identified as belonging to a basal macronarian, close to Camarasaurus. This work points to the existence of two macronarian sauropods in the Tithonian-Berriasian transit of the Cameros Basin, and increases the diversity of the Iberian record of that time period. En este trabajo se estudian un dentario y varios dientes procedentes del yacimiento Valdepalazuelos-Tenadas del Carrascal (Burgos, Spain), situado geologicamente en la base de la Formacion Rupelo (Cuenca de Cameros), de edad Titoniense-Berriasiense. Esta formacion se ha interpretado como depositos lacustres-palustres con margenes de gradiente bajo y con modificaciones periodicas del nivel del agua. MDS-VPCR,851 es un fragmento de la zona rostral sinfisial de un dentario derecho, es un hueso robusto con una cresta rostral en su superficie labial, foramenes de gran diametro en la superficie lingual, un canal meckeliano amplio y extendido desde el margen rostroventral, sinfisis semicircular y dispuesta rostrolingualmente, y con dos alveolos que contienen dos dientes en erupcion cada uno. Aunque los dientes funcionales no se han conservado, cada alveolo podria contener un diente activo y al menos dos dientes de reemplazo.. Se describen ocho dientes maxilares y mandibulares, de corona espatulada, superficie del esmalte rugosa, corona de seccion transversal con forma en D y cingulo muy marcado. El dentario y los dientes de este yacimiento tienen diferencias evidentes con los de otros taxones y especimenes descritos en el Kimmeridgiense-Berriasiense de la peninsula iberica. Sus mayores similitudes se dan con Camarasaurus, pero en los especimenes de Valdepalazuelos hay caracteres que parecen ser unicos y le diferencian de ese taxon. Por consiguiente los especimenes descritos aqui se identifican como pertenecientes a un macronario basal, proximo a Camarasaurus. Este trabajo apunta a la existencia de dos sauropodos macronarios en el transito Titoniense-Berriasiense de la cuenca de Cameros, y aumenta la diversidad del registro iberico de ese periodo temporal.

Automated summary

In this study, a dentary and several teeth from the Valdepalazuelos-Tenadas del Carrascal site in Burgos, Spain, were examined. The specimens were identified as belonging to a basal macronarian, closely related to Camarasaurus. This discovery indicates the presence of two macronarian sauropods in the Tithonian-Berriasian transition of the Cameros Basin, and expands the diversity of the Iberian record during that time period.