The singular Upper Cretaceous vertebrate sites of the Guadalajara Province (Central Spain): New data on the faunas from the Cenomanian of Algora and the Uppermost Cretaceous of Poyos
Abstract
The Cretaceous vertebrate fauna of the Guadalajara Province (Castilla-La Mancha, Central
Spain) was unknown until a few years ago. In fact, the systematic excavation campaigns in
Guadalajara began in 2013, those carried out in 2016 and 2017 being especially relevant.
These works were performed in two fossiliferous areas, separated from each other by about
60 km, both located in the Castilian Branch of the Iberian Ranges: the Cenomanian area of
Algora, especially the ALG-B site (Algora municipality); and the uppermost Cretaceous
outcrops of the western margin of the Buendía Reservoir, especially the Poyos site
(Sacedón municipality).
Localities with fossil vertebrates from the lower part of the Upper Cretaceous are very
scarce in Europe and, to date, the locality of Algora shows the highest concentration of
vertebrate remains recognized in the Cenomanian of this continent. Thus, the fossils from
Algora add important data for the understanding of the faunal turnover recognized when
the Lower Cretaceous and the uppermost Cretaceous faunas are compared. The study of
the new remains presented here allows us to analyze in more detail the fauna of fishes,
characterize the primitive turtle members present in this locality, know new anatomical
characters for the oldest European pleurodiran turtles, identify and describe remains of
elasmosaurids, recognize the presence of eusuchian crocodyliforms, describe the oldest
lithostrotian titanosaurs of the Iberian Peninsula, and perform a detailed analysis of the
theropod fauna. Several lineages from this site show a Gondwanan origin.
Poyos is an uppermost Cretaceous site located in one of the worldwide largest dinosaur
nesting areas, found in 2016. Thus, these fossiliferous levels extends over more than 10
km. With the exception of an isolated vertebral centrum of a titanosaur sauropod, no other
specimen from this locality has been published so far. The preparation of the fossils found
in 2006 and 2017 allows us to analyze both oological and osseous remains. Not only
isolated sauropod eggshells, but also complete eggs and several dinosaur clutches, have
been found. They show several singularities relative to both the microstructure of the
eggshells and the disposition of the eggs, in relation to those previously found in other
uppermost Cretaceous Iberian regions. In addition to elements of bothremydid turtles and
probably allodaposuchid crocodiles, the remains of dinosaurs are abundant in this region,
including several partial skeletons. Among them, a probable new middle-sized theropod is
identified.
Grant Information
Ministerio de Economía, Industria y Competitividad (CGL2015-68363-P, IJCI-2016-
30427) and Viceconsejería de Cultura de Castilla-La Mancha (SBPLY/0021-0070).