Josep Fortuny

This paper discusses the taxonomic affinities of three isolated teeth discovered in the Buntsandstein facies of the Catalan Coastal Ranges and central-eastern Pyrenean basins that crop out in Catalonia, northeastern Spain. The tooth crowns are blade-like, labiolingually compressed, distally recurved, and proportionally apicobasally tall, in which the most complete of them is at least 2.4 times taller than its mesiodistal depth at base. The distal margins possess a densely serrated carina, and the mesial margins lack carina and serrations. The enamel of the crowns lacks ornamentation (e.g., wrinkles , ridges) or macroscopic wear-facets. The three teeth are referred to indeterminate crocopodan archosauromorphs based on the presence of labiolingually compressed and serrated crowns. The absence of mesial denticles resembles the condition in the non-archosauriform archosauromorph Teyujagua, proterosuchids, and some more crownward archosauriforms (e.g., some proterochampsids). We could not find evidence to determine if these teeth belong to a single or multiple closely related species. These remains represent the first direct archosauromorph remains from Lower−Middle Triassic beds of the Iberian Peninsula and add information about the geographic distribution of the group during the dawn of the evolutionary radiation of the

Purpose. Xiphosurids (horseshoe crabs) are aquatic chelicerate arthropods commonly related to marine environments. Although today only four marine species exist, in the geological record they were much more diverse (especially during Carboniferous and Triassic periods), and even inhabited non-marine settings. Here we analyze an exceptional xiphosurid trace-fossil site preserved in the lowermost Buntsandstein red-beds from the Early Triassic of the Catalan Pyrenees.
Methods. Ichnological and sedimentological analyses were mainly conducted during fieldwork. Fossiliferous surfaces were cleaned and mapped in order to recognize distribution and orientation patterns.
Results. Two main ichnotaxa were identified: (1) Selenichnites isp. (>400 trace fossils), consisting of a lunate, anteriorly convex lobe (prosoma imprint) followed by a rounded to triangular impression (opisthosoma imprint) and a posterior straight thin groove (telson imprint); and (2) Kouphichnium isp. (about 70 trace fossils), consisting of long (up to 2 m), often curved, complex series of parallel rows of morphologically variable tracks and imprints.
Conclusions Selenichnites isp., interpreted as resting and/or feeding traces (cubichnia/fodinichnia), were mostly oriented against the current, preventing tracemakers being overturned. Kouphichnium isp. correspond to locomotion traces (repichnia). Trace fossils are found at the uppermost succession of fining- and energy decreasing- upwards fluvial red beds with no marine influence. These ichnofossils are the earliest Triassic evidence of life from the Catalan Pyrenees, and thus shed light on ecosystems composition at the dawn of the Mesozoic era, when biota recovered from the greatest mass extinction in Earth history.

The Carboniferous–Permian terrestrial successions record a global climatic shift from icehouse to hothouse conditions. Our multidisciplinary study documents an aridification trend throughout the ~1000 m thick composite terrestrial succession of the western Catalan Pyrenees (NE Iberian Peninsula), representing this time period. The detailed stratigraphic framework integrates sedimentology, paleopedology, biochronology (plant fossils and tetrapod footprints) and geochronology (paleomagnetism). Additional absolute age correlation is also carried out. The newand reviewed data showthat the late Carboniferous wet environments (with short drought periods) progressively changed to a strong seasonal semi-arid and arid climate (with short humid periods) through the early Permian. This paleoclimatic trend supports the previously suggested aridification of the Pangean pan-tropical belt, and supports the hypothesis of the influence of the recurrent climatic fluctuations in Central Pangea, being tentatively correlated to the Southern Gondwanan glaciation-deglaciation periods. Therefore, the Carboniferous–Permian terrestrial succession from the Catalan Pyrenees emerges as a continuous record that can help to constrain late Paleozoic paleoenvironmental events.

The most severe biotic crisis on Earth history occurred during the Permian–Triassic (PT) transition around 252 Ma. Whereas in the marine realm such extinction event is well constrained, in terrestrial settings it is still poorly known, mainly due to the lack of suitable complete sections. This is utterly the case along the Western Tethys region, located at Pangaea's equator, where terrestrial successions are typically build-up of red beds often characterised by a significant erosive gap at the base of the Triassic strata. Henceforth, documenting potentially complete terrestrial successions along the PT transition becomes fundamental. Here, we document the exceptional Coll de Terrers area from the Catalan Pyrenees (NE Iberian Peninsula), for which a multidisciplinary research is conducted along the PT transition. The red-bed succession, located in a long E-W extended narrow rift system known as Pyrenean Basin, resulted from a continuous sedimentary deposition evolving from meandering (lower Upper Red Unit) to playa-lake/ephemeral lacustrine (upper Upper Red Unit) and again to meandering settings (Buntsandstein facies). Sedimentary continuity is suggested by preliminary cyclostratigraphic analysis that warrants further analysis. Our combined sedimentological, mineralogical and geochemical data infer a humid-semiarid-humid climatic trend across the studied succession. The uppermost Permian strata, deposited under an orbitally controlled monsoonal regime, yields a relatively diverse ichnoassemblage mainly composed of tetrapod footprints and arthropod trace fossils. Such fossils indicate appropriate life conditions and water presence in levels that also display desiccation structures. These levels alternate with barren intervals formed under dry conditions, being thus indicative of strong seasonality. All these features are correlated with those reported elsewhere in Gondwana and Laurasia, and suggest that the Permian–Triassic boundary might be recorded somewhere around the Buntsandstein base. Consequently, Coll de Terrers and the whole Catalan Pyrenees become key regions to investigate in detail the Permian extinction event and the Triassic ecosystems recovery.

We describe crocodylian remains from the Early Miocene (MN4) site of Els Casots (Subirats,
VallèsPenedès
Basin, NE of the Iberian Peninsula). Referral to Diplocynodon (Alligatoroidea:
Diplocynodontidae) is justified by several cranial and postcranial features, including: (1)
the subequal and confluent alveoli of the maxilla (fourth and fifth) and dentary (third and
fourth); (2) the position of the foramen aëreum on the quadrate; (3) the small and ventrally
reflected medial hemicondyle of the quadrate; (4) the distinct dorsoventral step on the
frontal; and (5) the bipartite ventral osteoderms. Multiple morphological features are consistent
with an attribution to Diplocynodon ratelii, previously known from the Early Miocene
(MN2) of France, and discount an alternative attribution to other species of the genus,
including Diplocynodon ungeri from the Middle Miocene (MN5) of Austria. The described
material from Els Casots is smaller in size than the French material of D. ratelii, possibly
reflecting an earlier ontogenetic stage. The described remains constitute the first report
of D. ratelii and the youngest record of Diplocynodon in the Iberian Peninsula, where only
Diplocynodon muelleri and Diplocynodon tormis have been previously reported. The presence
of Diplocynodon further supports the lacustrine depositional environment previously
inferred for Els Casots and also indicates a relatively high temperature.

The Middle Triassic successions of coastal and distal alluvial systems are often characterized by the presence of the tetrapod ichnotaxon Rhynchosauroides. Nevertheless, few studies paid attention on the paleoenvironmental implications of this widely distributed ichnogenus. The finding of a new Rhynchosauroides-dominated tracksite opens the window to the use of such footprints in paleoenvironmental studies. The tracksite is located in the active quarry of Pedrera de Can Sallent, at Castellar del Vallès (Catalan Basin, NE Iberian Peninsula). The footprints were recovered from the Middle Muschelkalk detrital unit, composed of a claystone-sandstone-gypsum succession from a sabkha setting of late Anisian-middle Ladinian age. This unit was deposited during a short regression interval within the main Middle Triassic transgression represented by the Muschelkalk facies. The ichnoassociation is composed of Rhynchosauroides isp., and a single, partially preserved, undetermined large footprint. Among Rhynchosauroides specimens, three different preservation states were recognized, corresponding to substrates in (1) subaqueous conditions (surfaces with scarce, deformed, and deeply impressed ichnites), (2) occasionally flooded (mostly trampled surfaces, footprints commonly well preserved), and (3) subaerial exposition (surfaces with few footprints, sometimes corresponding to faint impressions or only preserved by claw marks). The footprint morphological variations of Rhynchosauroides are correlated to substrate rheology and further to the environmental conditions. Rhynchosauroides is a characteristic morphotype that often dominates in the Anisian-Ladinian coastal and distal alluvial settings of several European tracksites. Therefore, these ichnoassociations in such environments, awaiting further detailed analyses, may constitute a distinct ichnocoenosis.

The vertebrate recovery after the end-Permian mass extinction can be approached through the ichnological record, which is much more abundant than body fossils. The late Olenekian (Early Triassic) tetrapod ichnoassemblage of the Catalan Pyrenean Basin is the most complete and diverse of this age from Western Tethys. This extensional basin, composed of several depocenters, was formed in the latest phases of the Variscan orogeny (Pangea breakup) and was infilled by braided and meandering fluvial systems of the red-beds Bunt-sandstein facies. Abundant and diverse tetrapod ichnites are recorded in these facies, including Prorotodactylus mesaxonichnus isp. nov. (tracks possibly produced by euparker-iids), cf. Rotodactylus, at least two large chirotheriid morphotypes (archosauriform track-makers), Rhynchosauroides cf. schochardti, two other undetermined Rhynchosauroides forms, an undetermined Morphotype A (archosauromorph trackmakers) and two types of Characichnos isp. (swimming traces, here associated to archosauromorph trackmakers). The Pyrenean ichnoassemblage suggests a relatively homogeneous ichnofaunal composition through the late Early Triassic of Central Pangea, characterized by the presence of Pro-rotodactylus and Rotodactylus. Small archosauromorph tracks dominate and present a wide distribution through the different fluviatile facies of the Triassic Pyrenean Basin, with large archosaurian footprints being present in a lesser degree. Archosauromorphs radiated and diversified through the Triassic vertebrate recovery, which ultimately lead to the archo-saur and dinosaur dominance of the Mesozoic.

The neuroanatomy of hadrosaurid dinosaurs is well known from North America and Asia. In Europe only a few cranial remains have been recovered that include the braincase. Arenysaurus is the first European endocast for which the paleoneu-roanatomy has been studied. The resulting data have enabled us to draw ontogenetic, phylogenetic and functional inferences. Arenysaurus preserves the endocast and the inner ear. This cranial material was CT scanned, and a 3D-model was generated. The endocast morphology supports a general pattern for hadrosaurids with some characters that distinguish it to a subfamily level, such as a brain cavity that is anteroposteriorly shorter or the angle of the major axis of the cerebral hemisphere to the horizontal in lambeosaurines. Both these characters are present in the endocast of Arenysaurus. Osteological features indicate an adult ontogenetic stage, while some paleoneuroanatomical features are indicative of a subadult ontogenetic stage. It is hypothesized that the presence of puzzling mixture of characters that suggest different ontogenetic stages for this specimen may reflect some degree of dwarfism in Arenysaurus. Regarding the inner ear, its structure shows differences from the ornithopod clade with respect to the height of the semicircular canals. These differences could lead to a decrease in the compensatory movements of eyes and head, with important implications for the paleobiology and behavior of hadrosaurid taxa such as Edmontosaurus, Parasaurolophus and Arenysaurus. The endocranial morphology of European hadrosaurids sheds new light on the evolution of this group and may reflect the conditions in the archipelago where these animals lived during the Late Cretaceous. INTRODUCTION Hadrosaurids are the most abundant ornithopod dinosaurs from the Late Cretaceous of Laurasia, with a very complete record including ontogenetic series, mummies, eggs,

We describe crocodylian remains from the Early Miocene (MN4) site of Els Casots (Subirats, Vallès-Penedès Basin, NE of the Iberian Peninsula). Referral to Diplocynodon (Alligatoroidea: Diplocynodontidae) is justified by several cranial and postcranial features, including: (1) the subequal and confluent alveoli of the maxilla (fourth and fifth) and dentary (third and fourth); (2) the position of the foramen aëreum on the quadrate; (3) the small and ventrally reflected medial hemicondyle of the quadrate; (4) the distinct dorsoventral step on the frontal; and (5) the bipartite ventral osteoderms. Multiple morphological features are consistent with an attribution to Diplocynodon ratelii, previously known from the Early Miocene (MN2) of France, and discount an alternative attribution to other species of the genus, including Diplocynodon ungeri from the Middle Miocene (MN5) of Austria. The described material from Els Casots is smaller in size than the French material of D. ratelii, possibly reflecting an earlier ontogenetic stage. The described remains constitute the first report of D. ratelii and the youngest record of Diplocynodon in the Iberian Peninsula, where only Diplocynodon muelleri and Diplocynodon tormis have been previously reported. The presence of Diplocynodon further supports the lacustrine depositional environment previously inferred for Els Casots and also indicates a relatively high temperature.

Permian and Triassic tetrapods are very rare in Turkey. Yet this group bears important paleoenvironmental and paleogeographical signals to better understand Pangean models, and especially the geodynamic history of the Permian and Triassic in Turkey, which remains highly debated. Here we present and describe the first temnospondyls from Turkey (SE Ana- tolia) which consist of a Middle Permian branchiosaurid and an Early Triassic stereospondyl. The branchiosaurid is the first representative of its group in Gondwana and the first from the Middle Permian: it therefore brings important paleogeographic implications and sup- ports the hypothesis that anamniotic tetrapods may have used trans-Pangean migration routes between Europe and Gondwana. It also brings new data to the debated depositional environment of the Permian of SE Anatolia. The Triassic stereospondyl represents one of the few tetrapods known from paleoequatorial areas and confirms a relatively rapid faunal turnover of the anamniotic fauna after the Permian-Triassic mass extinction.

The continental Permian-Triassic transition in southern Europe presents little paleontological evidence of the Permian mass extinction and the subsequent faunal recovery during the early stages of the Triassic. New stratigraphic, sedimentological and paleontological analyses from Middle-Upper Permian to Lower-Middle Triassic deposits of the Catalan Pyrenees (NE Iberian Peninsula) allow to better constrain the Permian-Triassic succession in the Western Tethys basins, and provide new (bio-) chronologic data. For the first time, a large vertebra attributed to a caseid synapsid from the ?Middle Permian is reported from the Iberian Peninsula - one of the few reported from western Europe. Osteological and ichnological records from the Triassic Buntsandstein facies reveal a great tetrapod ichnodiversity, dominated by small to medium archosauromorphs and lepidosauromorphs (Rhynchosauroides cf. schochardti, R. isp. 1 and 2, Prorotodactylus-Rotodactylus, an undetermined Morphotype A and to a lesser degree large archosaurians (chirotheriids), overall suggesting a late Early Triassic-early Middle Triassic age. This is in agreement with recent palynological analyses in the Buntsandstein basal beds that identify different lycopod spores and other bisaccate and taeniate pollen types of late Olenekian age (Early Triassic). The Permian caseid vertebra was found in a playa-lake setting with a low influence of fluvial water channels and related to the distal parts of alluvial fans. In contrast, the Triassic Buntsandstein facies correspond to complex alluvial fan systems, dominated by highenergy channels and crevasse splay deposits, hence a faunal and environmental turnover is observed. The Pyrenean biostratigraphical data show similarities with those of the nearby Western Tethys basins, and can be tentatively correlated with North African and European basins. The Triassic Pyrenean fossil remains might rank among the continental oldest records of the Western Tethys, providing new keys to decipher the Triassic faunal biogeography and recovery.

A new Triassic actinopterygian specimen including the skull and the anterior portion of the squamation is described. The specimen represents the first find of a colobodontid from the Muschelkalk of Odèn locality (Pyrenean Basin, NE Iberian Peninsula). Although fragmentarily preserved in part and counterpart, the specimen shows considerable morphological details and fine preservation of bone structure. Comparisons to several well-known species of Colobodus AgAssiz, 1844 and Crenilepis Dames, 1888 from the Middle Triassic of the Besano Formation (northern Italy and southern Switzerland) and two specimens from Alcover outcrops (Catalonian Basin, NE Iberian Peninsula) previously assigned to Perleidus giganteus Beltan, 1972 enables a taxonomical re-assessment of Iberian colobodontids. The three specimens from the Iberian Peninsula are transferred to the genus Colobodus and re-named as Colobodus giganteus (Beltan, 1972) comb. nov. This taxon is the largest within the genus Colobodus and it is characterized by three diagnostic features: the series of supraorbitals, with more numerous and small ossifications in comparison with the rest of Colobodus species; the branchiostegal rays, more slender than in C. bassanii; and the teeth on the jaw margins not as well developed as in all other species of Colobodus, despite its considerable size.

A small accumulation of bones from the Norian (Upper Triassic) of the Seazza Brook Valley (Carnic Prealps, Northern Italy) was originally (1989) identified as a gastric pellet made of pterosaur skeletal elements. The specimen has been reported in literature as one of the very few cases of gastric ejecta containing pterosaur bones since then. However, the detailed analysis of the bones preserved in the pellet, their study by X-ray microCT, and the comparison with those of basal pterosaurs do not support a referral to the Pterosauria. Comparison with the osteology of a large sample of Middle-Late Triassic reptiles shows some affinity with the protorosaurians, mainly with Langobardisaurus pandolfii that was found in the same formation as the pellet. However, differences with this species sugges that the bones belong to a similar but distinct taxon. The interpretation as a gastric pellet is confirmed.

Miocene small-bodied anthropoid primates from Africa and Eurasia are generally considered to precede the divergence between the two groups of extant catarrhines—hominoids
(apes and humans) and Old World monkeys—and are thus viewed as more primitive than the stem ape Proconsul. Here we describe Pliobates cataloniae gen. et sp. nov., a small-bodied (4 to 5 kilograms) primate from the Iberian Miocene (11.6 million years ago) that displays a mosaic of primitive characteristics coupled with multiple cranial and postcranial shared derived features of extant hominoids. Our cladistic analyses show that Pliobates is a stem hominoid that is more derived than previously described small catarrhines and Proconsul. This forces us to reevaluate the role played by small-bodied catarrhines in ape evolution and provides key insight into the last common ancestor of hylobatids (gibbons) and hominids (great apes and humans)

Recent finds of tetrapod ichnites in the red-bed and volcaniclastic succession of the Iberian Pyrenean Basin permits an assessment of the faunal diversity and palaeoenvironment of a late early Permian setting. The tetrapod ichnoassemblage is inferred with the aid of photogrammetry and constituted by Batrachichnus salamandroides, Limnopus isp., cf.  Amphisauropus (these three ichnotaxa present associated swimming traces, assigned to Characichnos), cf. Ichniotherium, Dromopus isp., cf. Varanopus, Hyloidichnus isp. and Dimetropus leisnerianus. These ichnotaxa suggest the presence of temnospondyls, seymouriamorphs, diadectomorphs, araeoscelids, captorhinids and synapsid pelycosaurs as potential trackmakers. These faunas correlate to the late early Permian. Two ichnoassociations correspond to two different palaeoenvironments that were permanently or occasionally aquatic (meandering fluvial systems and unconfined runoff surfaces, respectively). Ichnotaxa in the fluvial system is more diverse and abundant than in the runoff surfaces system. The Iberian Pyrenean ichnoassemblage reveals the faunistic connection and similarities among nearing basins (Spain, southern France and Morocco) differing from the Central European basins (i.e. German Tambach Formation). Based on the palaeogeography and the climate models of the early Permian, we suggest the correlation of ichnofaunal composition with different palaeoclimate biomes. This results in a diffuse boundary of Gondwana–Laurasia land masses, indicating no geographic barriers but a possible climate control on the faunal distribution. Further studies, integrating data from distant tracksites, should refine these biome boundaries.

Finite Element Analysis (FEA) is a great tool for biologists, palaeontologists, doctors, veterinarians, and other biosciences specialities in which researchers face questions about biomechanics of living and extinct organisms. Elements like bone, arthropod exoskeleton, mollusc shells, or the stems and leaves of plants can be analysed using this technique. FEA is a non-invasive modelling technique, based on the principle of dividing a system into a finite number of discrete elements where the equations are applied. Although static and dynamic analysis can be solved using FEA, in this course only static analysis will be covered.
In this course, there will be an introduction to the Finite Element in order to model biological structures and understand how they worked. It will cover all the steps involved in FEA (for static analysis) except the creation or reconstruction of the model, which will be covered in the previous course 3D Model Generation in Biosciences. That is how to define the material properties of biological structures, the use of a consistent Mesh Generation Methods, the proper definition of biomechanical boundary conditions and finally, how understand and analyse the results obtained in a computational simulation.
After the theoretical introduction we will build and analyse 2D and 3D finite element models of skeletal elements and deepen on the methods and software’s required to perform FEA. Key questions as mesh size, boundary conditions, applied forces, scaling and numerical singularities will be thoroughly addressed. The last day attendees will have opportunity for trying to analyse by themselves their own data or other examples with the help of both instructors.

This course is addressed to bioscience researchers and technicians who routinely work with complex biological structures and need to analyze them in three dimensions, and who digitise their samples for any reason, such as digital preservation or retrospective analysis of a previously scanned sample. You may arrive at this course from a diversity of different backgrounds (laser, photogrammetry, CT, etc.) and use it as a basis to move on to further analyses.
The course is designed to enable participants to arrive at a three-dimensional image solution by concentrating on not just one methodology or technology but by considering the range that is available. This range is now quite extensive, including such things as 3D imaging, 3D printing, image processing, image filtering, laser imaging, photogrammetry, computed tomography (CT), and more. Images resulting from one methodology or technology should not be the end of the road but a starting point from which you can gain much more by performing other analyses, applying other methodologies or using different technologies, even with existing data. It is easy to become satisfied by one methodology that you know well, yet there may be much more you can achieve. And there are other advantages. Not only will your final result be more precise and accurate, you also have the potential of finding a more efficient approach than the one originally chosen, even though a multi-solution approach might seem inefficient at the outset.
The goal of this course is to explain how you can work with a range of technologies with the aim of obtaining a 3D model from different sources. By the end of the course participants should be able to work in an autonomous way to develop high quality digitalizations of samples with the most commonly used techniques and also be able to edit and manipulate the digital models that are produced.

Tetrapod footprints are the most abundant vertebrate record of the Late Paleozoic and therefore crucial in the understanding of early tetrapod locomotion, habitats, and evolution. The Early Permian ichnological record is known worldwide and particularly well represented. It is often encountered in red-bed deposits resulting from the aridization of Pangea. In this period, the Pyrenees (NE Iberian Peninsula) existed in
the equatorial region of the supercontinent as sedimentary basins infilled by volcanosedimentary deposits. In the recent years, we analyzed several outcrops bearing abundant tetrapod trace fossils in the Catalan Pyrenees. As a result, we were able to identify a wide diversity of ichnomorphotypes attributed to temnospondyls, possible seymouriamorphs, possible diadectomorphs, araeoscelids, bolosaurids, captorhinids and synapsids. Of particular interest for the track maker’s behavior, we discovered three different forms of swimming traces, corresponding to the ichnogenus Characichnos and associated with small- and large-sized temnospondyls (Batrachichnus salamandroides and Limnopus sp., respectively), and possible seymouriamorphs (cf. Amphisauropus).These remains represent an excellent tool to deepen the understanding of early tetrapod locomotion.
The swimming traces correspond to digit tip prints dragged over the surface, i.e., scratches. The ichnites occur in groups of two to four digit scratches, ranging in length from 5 to 60 mm. Scratches are mostly curved or slightly sinuous (sigmoidal), but sometimes also straight. These traits, together with the expulsion rims commonly observed in the posterior part, record the limb movement of the trackmakers.
Moreover, several surfaces present transitions from walking to swimming traces. Trackways composed of scratches and rounded digit tip impressions display irregular patterns indicating a relatively buoyant gait of the trackmaker. In all, these early tetrapods were capable of both terrestrial and subaqueous locomotion, which permitted a wide environmental distribution and colonization of the continental realm.

Three-dimensional Finite Element Analysis is a powerful tool in understanding ecomorphological patterns because it shows how deformation and stress distribution relates to different biological geometries. Over the last years, FE analysis has often been combined with Geometric Morphometrics. FEA may also be complemented with
other techniques, such as osteohistological investigations, although this has thus far not been tested. In this respect, digital models can be directly assessed with histology, as bone microstructure reflects loading regime. We used Finite Element Analysis to deepen the understanding of the feeding ecology of the early tetrapod group Temnospondyli, and in particular of the Late Triassic taxon Metoposaurus krasiejowensis, with the aim to assess the stress pattern of the skull under different biomechanical loads. FEA investigations were conducted under three different biomechanical feeding simulations: bilateral, unilateral and lateral biting. In parallel, 18 thin-sections from the dermal skull roof and palatal bones of a well-preserved Metoposaurus skull were examined to collect information about the microanatomical variability of the selected bones. Bone thickness and bone porosity influence the biomechanical stress distribution. The bones lose strength and stiffness with increasing porosity; this can be partly compensated for by increasing the thickness of the structure. The bones from the anterior and posterior parts of skull roof, e.g. the maxilla, nasal, lacrimal, postparietal, quadratojugal and supratemporal, have the optimal histological properties (high thickness and low porosity) to resist biomechanical forces. The bones from the palatal side, e.g. vomer and parasphenoid, possess the weakest mechanical resistance (low thickness and high
porosity). The histological model of stress distribution was compared with the threedimensional FEA model. Both methodologies reveal that unilateral biting was probably not performed by these animals. Osteohistological results suggest that Metoposaurus krasiejowensis was particularly optimized for lateral biting while FEA revealed that bilateral biting could also be supported by these animals. Regarding
lateral biting, the high levels of stress simulated on the posterior parts of the skull palate correlates with the histological variability and microanatomical properties for most of the examined bones.

Gallotia stehlini is the only species of lacertid living in the canarian island of Gran Canaria (with exception of the recently introduced Gallotia atlantica). The identity of subfossil populations in all islands is still debated because many extinct species have been subsequently synonymised or their rank has changed. The presence of small specimens among material from La Isleta locality (Pleistocene) posed a problem regarding whether they corresponded to a juvenile of G. stehlini or to an adult of a small species now extinct in the island. Accordingly, a proper identification of subfossil material from Gran Canaria was important in its potential to highlight differences between the subfossil and extant populations that could reveal the presence of a different species or subspecies, or in assessing the presence of G. stehlini as a subfossil.
We performed a deep study of subfossil remains of Gallotia from Gran Canaria for the first time in order to investigate the identity of the subfossil populations. The remains studied were collected in the late XIXth century from the classical locality of la Isleta and are housed at Museu de Geologia de Barcelona, but had not been previously reported or investigated. Other specimens from the same locality have been cited and shallowly described, but their identification as G. stehlini had a weak
morphological basis. These previous vague descriptions of otherwise well-preserved specimens were a consequence of the presence of a crust covering the articulated bones, what precluded a proper observation of morphological details. We performed a Micro CT-Scan of one of the small previously unpublished specimens in order to provide an accurate account of the osteological characters and compare them with the states in different species of Gallotia. Our results indicate that this specimen unequivocally represents a juvenile of G. stehlini, and no evidence for the presence of a different species or subspecies has been identified. The exceptional preservation of the specimens from La Isleta suggest a high potential for investigating a subfossil population in Gran Canaria (including ontogenetic changes), but may necessarily rely in the acquisition of Micro CT-Scans of the remaining specimens.