Dinosaur Footprints and Trackways of La Rioja (Life of the Past) - Hardcover

Pérez-Lorente, Félix

Hardcover

ISBN 10: 0253015154 ISBN 13: 9780253015150

Publisher: Indiana University Press, 2015

Synopsis

During the Early Cretaceous, lakes, meandering streams, and flood plains covered the region where the current foothills of Rioja now exist. Today the area is known for its wine and for the dozens of sites where footprints and trackways of dinosaurs, amphibians, and even pterosaurs can be seen. The dinosaurs that lived here 120 million years ago left their footsteps imprinted in the mud and moist soil. Now fossilized in rock, they have turned Rioja into one of the most valuable dinosaur footprint sites in all of Europe. Félix Pérez-Lorente and his colleagues have published extensively on the region, mostly in Spanish-language journals. In this volume, Pérez-Lorente provides an up-to-date synthesis of that research in English. He offers detailed descriptions of the sites, footprints, and trackways, and explains what these prints and tracks can tell us about the animals who made them.

About this title

About the Author

Félix Pérez-Lorente teaches geology at Universidad de La Rioja, Spain.

Excerpt. © Reprinted by permission. All rights reserved.

Dinosaur Footprints & Trackways of La Rioja

Life of the Past

By James O. Farlow

Indiana University Press

Copyright © 2015 Félix Pérez-Lorente
All rights reserved.

ISBN: 978-0-253-01515-0

Contents

1 La Rioja Footprints, 2, 
2 Ichnology, 14, 
3 The Tracksites, 36, 
4 Conservation of the Tracksites, 315, 
5 Summary, 324, 
REFERENCES, 341, 
INDEX, 353, 

CHAPTER 1

La Rioja Footprints

Introduction

THE SPANISH PROVINCE OF LA RIOJA IS AN AREA OF THE WORLD where a huge number of dinosaur footprints have been found, with many more likely yet to be discovered. This hilly region has many rock slopes with layers so full of tracks that, if the vegetation, loose rock, and debris could be removed, would yield from 8000 to as many as 25,000 footprints. Using the best estimates from some slopes – that is, the maximum estimate from that partial data – there may be as many as 70,000 footprints.

Many of the footprints are so easy to see that the first people to discover them were likely shepherds or hunters who passed through the area. However, the identity of the first person to correctly interpret them is another question. The footprints are so evocative that the inhabitants of the region have long associated them with animals. In the villages of Enciso, El Villar, and Poyales, there were people who thought the footprints now understood to be those of theropod dinosaurs had been made by giant chickens. In the village of Navalsaz, it was said that the ornithopod footprints of the Cuesta de Andorra had been made by huge lions. It is difficult to know exactly how long such claims have been made, whether the local population even knew about wild animals such as lions, or whether this interpretation was offered by visitors to the region.

The footprints have also been attributed to animals from medieval mythology, in some cases inspired by religion. For example, in Igea, it was said that the footprints had been left by the horse of the apostle James on his travels. Popular tradition has it that James helped the Christians in their wars against the Muslims. As with the legendary "mule tracks" of Setubal in Portugal, there is no end of imaginative interpretations. In some cliffs to the south of Lisbon (Portugal) there are some dinosaur footprints which the ancient Portuguese interpreted as being miraculous. Miguel Telles Antunes (1976) says that according to legend, the Virgin Mary "Santa Maria da pedra da mua" (or an image of her from the 18th century) had come out of the sea and ascended to the top of the cliff while sitting on a mule. During the ascent, the mule left the footprints on the wall. According to Antunes, this tradition may date back to the 13th century. In Igea, the "horse's" footprints are visible near the Santa Ana chapel, at the place where the apostle's horse was said to have jumped 3 km to land near the shrine of the Virgen del Villar, where it also left footprints. Interpretations such as these are to be expected, given the knowledge of the population. For example, the presence of marine fossils in many places had to be explained as a whim of nature. Even if no one could explain why, the sea must have been there. Nature is capable of wonderful things! Even today, if you ask an old farmer or shepherd how the sea could ever have been so far inland, although he may not be able to provide an explanation, no one will be able to convince him it was not so. For the people, the rocks, rivers, sea, and mountains have always been where they are at present. In their village, there was never a sea.

Nor would any of the local inhabitants have been able to predict that the sloping rock strata on which the tracks appear had once been horizontal mudflats. It is understandable that people did not consider that normal animals could leave their footprints in such hard rock, whereas the horse of Saint James might have had magical properties that allowed it to make an impression in solid rock. It may have been the wish of the saint – or even the horse – that the footprint left behind had a shape very different from that left by a typical horse.

It is likely that almost all settlements with dinosaur footprints had traditions and legends surrounding them that have since been lost or that the older generation do not want to tell to strangers.

History of Discoveries

The first publication about dinosaur footprints in the Iberian Peninsula that I have in my possession is from Jacinto Pedro Gomes (1915–1916) for Cabo Mondego (Portugal), and the first in Spain is from Albert F. de Lapparent (1965) for the east (province of Valencia). Although geological research began in La Rioja a long time ago, the footprints were not recognized until 1969, when the first publication about dinosaur footprints in La Rioja appeared in the newspaper El Correo Español – El Pueblo Vasco. The authors were Moisés Iglesias Ponce de León, a geologist, and Luis Vicente Elias, an ethnologist, who found the footprints while doing fieldwork on the customs of the people from the Cameros region. After this discovery, a number of favorable events occurred.

The first was that the news was not published just in the newspaper. Almost immediately, a learned researcher, Blas Ochoa, who was a schoolteacher from Enciso, began collaborating with a team of vertebrate paleontologists, Maria Lourdes Casanovas and José Vicente Santafé. The team described five sites in two publications in 1971 and 1974. The two publications and comments from townspeople who had known the paleontologists inspired two groups of amateurs to search for new sites in their spare time and publish their findings as a challenge to other researchers. By 1979, nine sites had been identified, all near the village of Enciso. (These groups are still working, partly because they have active members and partly because we have followed in their footsteps in looking for new track sites.) Later, a schoolteacher from Igea, Angel Gracia, taught his pupils the importance of fossils and showed them how to search for, classify, and preserve them. His students found sites with footprints near the village, one of which remains to be studied.

More recently, traces of other vertebrates have been discovered: birds, turtles, and pterosaurs (Moratalla and Hernán, 2009; Moratalla and Sanz, 1992; Moratalla, Sanz, and Jiménez, 1992), crocodiles (Ezquerra and Pérez-Lorente, 2002, 2003), and fishes (Costeur and Ezquerra, 2008; Ezquerra and Costeur, 2009; Ezquerra and Pérez-Lorente, 2002, 2003). Today, the followers of Blas and Angel have their own specialist centers. In Enciso, there is a paleontological museum, and the first phase of a learning center on "the lost ravine" has been built, as well as another center in Igea that houses some interesting paleontological material collected mostly by those pupils, who in 2010 are about 40 years old. Both centers are strongly committed to scientific activities and educating tourists.

Just as dinosaur track sites are still being found in La Rioja, so are they also being found in other locations of the Iberian Peninsula, although in rocks of different ages. There are examples of dinosaur footprints from the Late Triassic, Middle and Upper Jurassic, and Early and Late Cretaceous periods.

Cameros Basin

The geological diagram in Fig. 1.1 shows the locations and ages of outcrops of Mesozoic rocks in the Iberian Peninsula that potentially contain dinosaur fossils. The Iberian sites with dinosaur tracks occur in the regions with Mesozoic outcrops. Thus, this figure indicates the geographic limits for the areas of possible dinosaur remains in Iberia.

The Iberian Peninsula consists of four major geological areas, as follows:

1. A central region of ancient volcanic and sedimentary rocks, metamorphic rocks, and plutonic rocks (Paleozoic and Precambrian), considered a stable zone (not folded) during the Alpine Orogeny. The Alpine Orogeny is the mountain-building event that created the Alps and in Spain the Pyrenees, Iberian Range, and Betic Cordillera. The Alpine Orogeny affects (folds) the Mesozoic strata between or adjacent to the stable Paleozoic and Precambrian zones.

2. A border with outcrops of Mesozoic sedimentary rocks, sometimes mixed (at the eastern edge) with older ones.

3. Two Tertiary depressions filled with Tertiary and Quaternary rocks (depressions associated with the Ebro River to the northeast and the Guadalquivir River to the south).

4. Two external Alpine chains with deformed ancient and modern sedimentary rocks (the Pyrenees bordering France and the Betic Cordillera to the south).

The Cameros Basin is located on the northeastern edge of the stable zone, where the Paleozoic and Precambrian Mesozoic sedimentary rocks, folded by the Alpine Orogeny, are found. It is between the Ebro Basin and the stable zone. The Cameros Basin was named by Brenner and Wiedmann (1974), although Götz Tischer (1966) and Gerhard Richter (1930) have previously used the word "basin" to encompass the Wealdian sediments ranging from the province of Burgos to north of Ricla (Zaragoza Province).

The first stratigraphic summary of this region was published by Palacios and Sánchez Lozano (1885), who divided the "Wealdian formation" into strata of lacustrine sediments divided into different superimposed lithological parts called "sections (B and C), bank (A) and levels (a, b, c)." The terms are literal translations from the Spanish (sección, banco, nivel) used in an ancient geological language. The possible equivalents are "unit" or "member," "bed," and "level." Rafael Sánchez Lozano's five superimposed lithological parts (Fig. 1.2) correspond in part to the Tera, Oncala, Urbión, Enciso, and Oliván groups of Tischer (1966). The names of the groups are still used, with virtually the same meaning and positions defined by Tischer.

Long before footprints were discovered, the Early Cretaceous (Wealdian) age of the rocks containing them was already known and had been more precisely classified into five sedimentary groups defined by Tischer and by other followers of Professor Hans Mensink (Bochum University). It was also known that the lowest group (Tera), with abundant conglomerates at its base, was underlain by marine rocks of Late Jurassic age.

The exact age of the base and the top of the sediments in the Cameros Basin is difficult to establish because they lack appropriate fossils. The transition from the Late Jurassic to the Early Cretaceous occurs in continental sediments. The uppermost Jurassic marine sediments are limestone reefs of Kimmeridgian age (Alonso, Meléndez, and Mas, 1986–1987; Mas et al., 2002). The age of the continental sediments in the Cameros Basin ranges from the mid-Kimmeridgian (sensu lato) to the mid–late Albian (see Doublet, 2004) (Fig. 1.3). This period extends from the base of the Tera Group to the top of the Oliván Group. So far, all dinosaur footprints in La Rioja are of Early Cretaceous age (Fig. 1. 2). Two sites, El Encinar and La Vuelta de los Manzanos (Moratalla, Sanz, and Jiménez, 1996, 2000b), situated at the boundary of the Tera and Oncala groups, have been assigned to the Late Jurassic (see Cámara and Durantez, 1982) (Fig. 1.4, Tables 1.1, 1.2).

The Cameros Basin is situated at the northeast end of the Iberian Range. Sites with dinosaur footprints or bones occur from this point to the Mediterranean coast. Correlation of the Cretaceous sediments in La Rioja is simple in all directions except toward the north. The Cameros Basin continues into the provinces of Burgos to the west, Soria to the south, and Zaragoza to the east (Fig. 1.2). To the north, the continuity of Mesozoic outcrops is lost because the Tertiary rocks of the Ebro Basin cover them.

Outcrops in the south and southwest of the Cameros Basin reveal rocks of detrital material, the source of which was further south and west. The five stratigraphic groups come together in the northern outcrops in a spectacular pattern of thinning and overlap, and both the limestones and shales and dark sandstones of the Urbión and Enciso groups grade into light (sand, silt, and clay) and red-colored siliciclastic rocks (Doublet, 2004).

The deepest part of the Cameros Basin was initially in the province of Soria (the Oncala and Urbión/Berriasian–Barremian) and later in La Rioja (first the Enciso Group to the southwest/Barremian–lower Albian, and finally in the Oliván Group situated more to the northeast/Albian). It seems, therefore, that the center of subsidence of the basin drifted from Soria to La Rioja during the Early Cretaceous, at least for the Oncala, Urbión, Enciso, and Oliván groups. All fossils found in this sequence are continental freshwater, or brackish at most. Only two stratigraphic levels, located in the Oncala Group, have been shown to contain marine microfossils (Alonso and Mas, 1993; Suárez-González et al., 2011).

In the Cameros Basin area of La Rioja, dinosaur bones have been found that are attributed (Fig. 1.5) to Baryonyx (Torres and Viera, 1997; Viera and Torres, 1995a) and Hypsilophodon (Torres and Viera, 1994); also found were eroded vertebra and bones from sauropods and ornithopods related to Iguanodon. In addition, theropod and ornithopod teeth have been discovered, and some theropod phalanges are being studied. In addition to dinosaur bones, fossils include osteodermal and other bony elements of turtles, crocodiles, pterosaurs, and various kinds of fish (Lepidotes, Hybodus); charophytes, ostracods, and shells from bivalves and turritellid gastropods. Many sedimentary layers are composed of algal laminations, and in some layers there are higher plants, such as transported conifers and ginkgoales, as well as abundant roots of variable thickness, but less than 10 cm in diameter.

Skeletal remains of dinosaurs are abundant in the Early Cretaceous of Spain; they perhaps constitute the richest fossil association in the sediments of continental Europe in the Hauterivian–Aptian interval. Proof of this diversity is that remains from 15 different dinosaur taxa have been found at a single site from the Early Barremian of Teruel (Canudo et al., 2009, 2010; Ruiz-Omeñaca, 2011). Another significant aspect of the Spanish dinosaurs of the Early Cretaceous is their great paleobiogeographical complexity, including taxa with Asiatic, Gondwanan, and North American affinities as well as European ones (Canudo, Royo-Torres, and Cuenca-Bescós, 2008; Canudo et al., 2009; Ortega, Escaso, and Sanz, 2010; Pereda-Suberbiola et al., 2007; Ruiz-Omeñaca et al., 2004). The best-represented dinosaurs are the sauropods. Representatives of neosauropods have been found, both diplodocimorphs such as Demandasaurus (Torcida et al., 2011) and macronarians such as Tastavinsaurus and Aragosaurus (Canudo, Royo-Torres, and Cuenca-Bescós, 2008; Sanz et al., 1987). Nonavian theropods are represented by basal tetanurans such as allosauroids and spinosaurids and by derived tetanurans such as ornithomimosaurs and dromaeosaurids. To date, two taxa have been described: the ornithomimosaur Pelecanimimus (Pérez-Moreno et al., 1994) and the carcharodontosaur Concavenator (Ortega, Escaso, and Sanz, 2010). Thyreophorans are scarce, though remains of "polacanthid" ankylosaurs and stegosaurs have been described (Pereda-Suberbiola and Galton, 2001; Pereda-Suberbiola et al., 2007). Ornithopods are represented by basal iguanodontoids, dryosaurids, and "hypsilophodontid"-like basal euornithopods. The iguanodontoid Delapparentia has been described (Ruiz-Omeñaca, 2011). The basal iguanodontoids are the most abundant dinosaurs in terms of the number of dinosaur specimens in the Early Cretaceous of Spain.

Sedimentological studies indicate that a large portion of the sedimentary succession is lake or marsh deposits, with both siliceous and limestone strata, as well as other fluvial siliciclastic (silt, sand, and conglomerate) sediments. In some places there are sebka-type deposits containing gypsum and other salts.

The Enciso Group was the subject of a study that detected the presence of a large lake (about 500 km2) (Doublet, 2004), the existence of which is demonstrated by, among other things, the great lateral continuity (in composition and thickness) of certain distinctive sedimentary layers. After the sedimentary filling of the subsiding Cameros Basin in the earliest Cretaceous came the compressive and thermal stage. The Alpine Orogeny began in the Albian period with compression and metamorphism. Silt and loose sand were compacted and their minerals recrystallized. Where the temperature was greater, veins of quartz and phyllosilicates grew. Chloritoid was formed, which indicates that the maximum temperature reached nearly 400°C, with large pyrite crystals forming at the same locations. The high temperature had a positive impact on the preservation of the tracks because it hardened the rocks in which they are located without destroying structures directly or indirectly related to them.

Number, Distribution, and Area of Sites

Dinosaur footprints occur in all the stratigraphic groups of the Cameros Basin (Fig. 1.2) except the Oliván Group. In La Rioja, the distribution of the sites is approximately linear in association with outcrops of the Enciso Group (Fig. 1.4) (Blanco et al., 1999b; Casanovas and Santafé, 1995; Moratalla, 2002; Moratalla and Hernán, 2007; Pérez-Lorente, 2006). The number of outcrops containing footprints is difficult to quantify. In some cases, multiple sites were recognized along the same layer as they were being discovered (such as six in Era del Peladillo). In other cases (e.g., La Torre in the same area), multiple sites were grouped together because they all occur in a particular exposure (e.g., one side of a hill), even though there may be no continuity between them and they may occur in different sedimentary layers. The number is in the range of 110 to 156 sites or exposures with footprints (Table 1.1) (Caro, Pavía, and Pérez-Lorente, 1997; Pérez-Lorente, 2003a, 2003b).

Outcrops with easily recognizable footprints are more abundant in the Enciso Group than in the other groups. However, this is not necessarily an indication of the number of prints that actually exist because the footprint-bearing stratification surfaces may be obscured as a result of the nature of the rocks. The interaction between the composition and structure of the rock and weathering is the main factor in how well footprints are displayed. Many of the rocks in the Urbión Group, for example, contain many footprints that go unnoticed by observers. Isolated footprints in single rock surface fragments on the slopes are not considered to be sites.

(Continues...)

Excerpted from Dinosaur Footprints & Trackways of La Rioja by James O. Farlow. Copyright © 2015 Félix Pérez-Lorente. Excerpted by permission of Indiana University Press.
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Edition details

• Publisher: Indiana University Press
• Publication date: 2015
• Language: English
• ISBN 10: 0253015154
• ISBN 13: 9780253015150
• Binding: Hardcover
• Number of pages: 376