ʻLapillitubus montjuichensisʼ, the first urban fossil found in modernist buildings in Barcelona

The findings of the new urban ichnofossil - the first one described in a modernist building in Catalonia and Europe- are reported in a scientific article published in the journal Geologica Acta by the experts Zain Belaústegui, from the Faculty of Earth Sciences and the Biodiversity Research Institute (IRBio) of the University of Barcelona, and Alejandro Belaústegui, from the Asociación Alumnos Mayores (Senior Students Association, ALMUCAT) of the Carlos III University of Madrid, in Getafe Campus.

Urban fossils: a walk around the most remote past

“Urban fossils” have taken the attention of scientists and general audience for ages. In this field, ichnology is a discipline in palaeontology which studies fossil traces and prints left by the activity of these organisms in the past. These fossil traces or ichnotaxons -old burrows, dinosaur footprints, etc. - can reveal some mysteries on the features of the organism and the palaeoenvironment from millions of years ago.

“The new urban fossil Lapillitubus montjuichensis dates back to 12 million years ago, and is a simple, cylindrical and rectilinear burrow without any branching. It shows a layer of quarzitic lithocasts, that is, small quartz fragments or stones -1 to 10 mm in diameter- randomly displayed”, says Professor Zain Belaústegui, from the Department of Earth and Ocean Dynamics of the UB.

Lapillitubus montjuichensis: from the original rock to Catalan modernism

This new ichnotaxon can be seen in the stone blocks that make up the façade in some modernist buildings of Barcelona. The buildings of Palau de la Justícia, Aduana and Casa Pascual i Pons - by the Catalan architect Enric Sagnier- have the most distinguished ones.

“In general, the conservation state of these inchofossils is good. However, since they appear in stone blocks, only longitudinal or transversal sections of the fossil burrows can be recognized”, says Belaústegui. “In Casa Pascual i Pons we found the model with the best conservation state, which defines the new ichnogenre and new ichnospecies”.

Lapillitibus montjuichensis and other similar ichnogenres (Ereipichnus, Eklexibella, etc.) are grouped within what is known as agglutinated trace fossils. All of these ichnogenres -simple and cylindric burrows- are distinguished by different kinds of materials -with or without organic origins- such as foraminifers, remains of molluscs, crinoid stem plates or fish bone remains. In the case of L. montjuichensis, it has been verified for the first time that these layers are created only by litoclasts (mostly small quartz fragments) randomly placed.

How was Barcelona 12 million years ago?

The mountain of Montjuic has been the great source of sandstone for the Catalan modernist architecture since late 19th century. The findings of Lapillitubus montjuichensis will ease the study of make the study of invertebrates of the Miocene in the deltaic area which is currently in the mountain of Montjuic.

“These fossil burrows that dress the Catalan modernism were dug by worms (Terebellidae Polychaete) in a deltaic environment, affected by the impact of waves and with many sediments. “Therefore, it would be a subaquatic environment, close to the coast and not very deep, in which these invertebrates and other marine organisms like decapod crustaceans would have dug their burrows too” says Z. Belaústegui.

Terebellidae polychaete that left a fossil trace in deltaic sediments millions of years ago would look similar to some current species. In the west coast of Madagascar, there have been some current burrows of terebellidae polychaete which are almost identical to the ones seen in Montjuicʼs Miocene.

Looking for urban fossils around the world

The fossil prints of living beings that lived in this planet millions of years ago can also be admired nowadays in historical buildings and monuments in cities around the world. In 1935, for instance, a dinosaur footprint was discovered in one of the rocks of the bandstand in Glen Rose (United States), still preserved. Also, other ichnofossils of scientific interest have been described in gravestones (Leicestershire, United Kingdom), in shopping mall walls (London, United Kingdom) or cement floor (Copenhagen, Denmark). Urban fossils have enriched the paleontological heritage of cities such as Alcoy, Barcelona, Burgos, Leon, Segovia, Toledo or Biscay for years.

“Personally, if we consider the huge architectonic heritage of Barcelona, be it modernist or not, built or not built on the stone of Montjuic, with the right amount of study time, the option of finding other ichnotacons or new places with new samples of L. montjuichensis would exist. Therefore, we expect this work to serve as a stimulus for future similar studies and that it shows the importance of these unique urban ʻbloomingʼ” concludes Alejandro Belaústegui.


Geologia Acta: international outreach on Earth Sciences

The journal Geologica Acta, promoted by the University of Barcelona and the Institute of Earth Sciences Jaume Almera (ICTJA-CSIC), is an open-access institutional journal, with a  general profile on earth sciences. Edited by the lecturer Miquel Garcés, from the Faculty of Earth Sciences of the University of Barcelona, Geologica Acta was first published in March 2003, and its origins are in the journal Acta Geológica Hispánica (1966-2002).