Unusually thick dinosaur eggshell fragments from the Spanish Late Cretaceous

Fieldwork carried out recently in the southeastern branch of the Iberian Range (Valencia Province, Spain) has led to the collection of a large volume of dinosaur eggshell fragments of unusual thickness. These specimens, up to 4.9 mm thick, were recovered from palustrine grey marls of the upper Campanian-lower Maastrichtian Sierra Perenchiza Formation, which comprises a wetland paleoenvironment deposit. These eggshell fragments have a characteristic compactituberculate ornamentation, dinosauroid-spherulitic organisation, and exhibit a complex canaliculate respiratory system. The external tuberculate surface of the shell as well as the internal microstructure enable referral to Megaloolithus aff. siruguei, the most common megaloolithid oospecies known from the Iberian Peninsula and southern France. The biostratigraphic range of M. siruguei matches the temporal distribution of titanosaurid dinosaurs across the Iberian Range, tentatively considered to be potential producers.     

High European sauropod dinosaur diversity during Jurassic–Cretaceous transition in Riodeva (Teruel, Spain)

Abstract:  Up to now, more than 40 dinosaur sites have been found in the latest Jurassic – earliest Cretaceous sedimentary outcrops (Villar del Arzobispo Formation) of Riodeva (Iberian Range, Spain). Those already excavated, as well as other findings, provide a large and diverse number of sauropod remains, suggesting a great diversity for this group in the Iberian Peninsula during this time. Vertebrae and ischial remains from Riodevan site RD-13 are assigned to Turiasaurus riodevensis (a species described in RD-10, Barrihonda site), which is part of the Turiasauria clade. This is the first time that a taxon is attributed to Turiasaurus genus out of its type site. A Neosauropod caudal vertebra from the RD-11 site has been classified as Diplodocinae indet., supporting the previous attribution on an ilion also found in Riodeva (CPT-1074) referring to the Diplodocidae clade. New remains from the RD-28, RD-41 and RD-43 sites, of the same age, among which there are caudal vertebrae, are assigned to Macronaria. New sauropod footprints from the Villar del Arzobispo Formation complete the extraordinary sauropod record coming to light in the area. The inclusion of other sauropods from different contemporaneous exposures in Teruel within the Turiasauria clade adds new evidence of a great diversity of sauropods in Iberia during the Jurassic–Cretaceous transition. Turiasauria distribution contributes to the understanding of European and global palaeobiogeography.     

A Sauropod Dinosaur tooth from the Lower Cretaceousof Galve (Province of Teruel,Spain)

A sauropod tooth, from the Barremian-Aptian ofGalve (Teruel), is described in Spain for the first time. This tooth probably belongs to the sauropod reported by A.F. de Lapparent (1), a Brachiosaurinae different of that reported by J.V. Santafé, M.L. Casanovas & J.L. Sanz (2) and J.L. Sanz, J.V. Santafé & M.L. Casanovas (3) from Morella (Castellón, Spain), Lower Aptian in age. It is probably a lower left piece with a developped worn surface. The subfamily Brachiosaurinae-sensuR. Steel, 1970 (4)-has a certain coherence of tooth morphology in respect of other Camarasauridae-sensuR. Steel, 1970 (4). The piece from Galve belongs to a Brachiosaurinae close to Brachiosaurus, though could differ of this genus in the structure and distribution of enamel ornamentation.     

Evolutionary Transitions Among Dinosaurs: Examples from the Jurassic of China

Dinosaurs have captured the popular imagination more than any other extinct group of organisms and are therefore a powerful tool in teaching evolutionary biology. Most students are familiar with a wide variety of dinosaurs and the relative suddenness of their extinction, but few are aware of the tremendous longevity of their time on Earth and the richness of their fossil record. We first review some of the best-known groups of dinosaurs and discuss how their less-specialized relatives elucidate the path through which each evolved. We then discuss our recent discovery of Yinlong downsi, a distant relative of Triceratops, and other fossils from Jurassic deposits in China to exemplify how the continuing discovery of fossils is filling out the dinosaur family tree.     

Hoof-Like Unguals,Skin, and Foot Movements Deduced from Deltapodus Casts of the Galve Basin (Upper Jurassic-Lower Cretaceous,Teruel, Spain)

Galve (Teruel, Spain) is a town in the interior of a synclinal fold with Upper Jurassic marine limestones along its flanks, and, in its core, Upper Jurassic–Lower Cretaceous continental and shoreline sediments crop out. The core sediments cover an area about 8 km², and contain a concentration of sites with footprints, bones, and eggshells of dinosaurs. The footprints are both shafts and natural casts. Some casts are attributed to stegosaurs (Deltapodus). The Deltapodus casts are characterized by features that allow us to make direct observations on the skin formed by polygonal scales, and ellipsoidal “hooves,” as well as deductions on the movement of the limbs during walking. According to the opinion of some authors, dinosaur footprints are indicators of the motion of their limbs and sometimes of the whole body. So far, results have been deduced from theropod, ornithopod, and sauropod footprints. This article shows the results obtained from analis of the aforementioned Deltapodus casts, i.e., forelimb movement similar to that of the forelimbs of sauropods, and the rigid structure of the autopodial part of the hind limb.     

NEW MULTITUBERCULATE MAMMALS FROM THE HAUTERIVIAN/BARREMIAN TRANSITION OF EUROPE (IBERIAN PENINSULA)

Abstract: New multituberculate mammals from the Hauterivian/Barremian transition of Europe are described. They were found in the late Hauterivian‐early Barremian fossiliferous locality of La Cantalera (Josa, Teruel, Spain), one of the Early Cretaceous sites in the Aragonese branch of the Iberian Ranges, in northeastern Iberia. The fossils have been assigned to at least three taxa on the basis of nine isolated teeth: a new pinheirodontid taxon, Cantalera abadi gen. et sp. nov.; a representative of the eobaatarid Eobaatar; a taxon described as Plagiaulacidae or Eobaataridae gen. et sp. indet.; and other as Plagiaulacida indet. These fossils have increased the resolution of European Early Cretaceous multituberculate mammalian biostratigraphy and palaeobiogeography: the oldest representative of Eobaatar is described here; a taxon is assigned to ?Plagiaulacidae, in which case it would be the first of this family in the Iberian Peninsula; and the discovery of a new late Hauterivian pinheirodontid taxon demonstrates greater biodiversity and a wider distribution for these multituberculates than was previously known. The mutituberculate fauna of La Cantalera consists of endemic taxa (Pinheirodontidae), which were restricted to what is now Western Europe, and others (Eobaataridae) which have also been described in Asia. Consistent with the Iberian record of late Barremian gobiconodontid mammals, the presence of Eobaatar in Iberia with representatives from the late Hauterivian to late Barremian, as well as in the Aptian or Albian of Mongolia, indicates that faunal exchanges between Europe and Asia could have existed for most of the Early Cretaceous, either sporadically or constantly.     

The first 50Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity

The evolutionary radiation of dinosaurs in the Late Triassic and Early Jurassic was a pivotal event in the Earth's history but is poorly understood, as previous studies have focused on vague driving mechanisms and have not untangled different macroevolutionary components (origination, diversity, abundance and disparity). We calculate the morphological disparity (morphospace occupation) of dinosaurs throughout the Late Triassic and Early Jurassic and present new measures of taxonomic diversity. Crurotarsan archosaurs, the primary dinosaur 'competitors', were significantly more disparate than dinosaurs throughout the Triassic, but underwent a devastating extinction at the Triassic-Jurassic boundary. However, dinosaur disparity showed only a slight non-significant increase after this event, arguing against the hypothesis of ecological release-driven morphospace expansion in the Early Jurassic. Instead, the main jump in dinosaur disparity occurred between the Carnian and Norian stages of the Triassic. Conversely, dinosaur diversity shows a steady increase over this time, and measures of diversification and faunal abundance indicate that the Early Jurassic was a key episode in dinosaur evolution. Thus, different aspects of the dinosaur radiation (diversity, disparity and abundance) were decoupled, and the overall macroevolutionary pattern of the first 50Myr of dinosaur evolution is more complex than often considered.     

Increases in sampling support the southern Gondwanan hypothesis for the origin of dinosaurs

Dinosaurs were ubiquitous in terrestrial ecosystems through most of the Mesozoic and are still diversely represented in the modern fauna in the form of birds. Recent efforts to better understand the origins of the group have resulted in the discovery of many new species of early dinosaur and their closest relatives (dinosauromorphs). In addition, recent re‐examinations of early dinosaur phylogeny have highlighted uncertainties regarding the interrelationships of the main dinosaur lineages (Sauropodomorpha, Theropoda and Ornithischia), and questioned the traditional hypothesis that the group originated in South Gondwana and gradually dispersed over Pangaea. Here, we use an historical approach to examine the impact of new fossil discoveries and changing phylogenetic hypotheses on biogeographical scenarios for dinosaur origins over 20 years of research time, and analyse the results in the light of different fossil record sampling regimes. Our results consistently optimize South Gondwana as the ancestral area for Dinosauria, as well as for more inclusive clades including Dinosauromorpha, and show that this hypothesis is robust to increased taxonomic and geographic sampling and divergent phylogenetic results. Our results do not find any support for the recently proposed Laurasian origin of dinosaurs and suggest that a southern Gondwanan origin is by far the most plausible given our current knowledge of the diversity of early dinosaurs and non‐dinosaurian dinosauromorphs.     

Bite traces on dicynodont bones and the early evolution of large terrestrial predators

Nied?wiedzki, G., Gorzelak, P. & Sulej, T. 2010: Bite traces on dicynodont bones and the early evolution of large terrestrial predators. Lethaia, Vol. 44, pp. 87–92. Dicynodont (Synapsida: Anomodontia) bones from the Late Triassic (late Norian/early Rhaetian) of Poland yield characteristic tooth marks that can be attributed to three ichnotaxa (Linichnus serratus, Knethichnus parallelum and Nihilichnus nihilicus). The general shape and dimension of these traces perfectly match the dental morphology of a co‐occurring carnivorous dinosaur. It is therefore concluded that early carnivorous dinosaurs were feeding on dicynodonts. This discovery constitutes one of the oldest evidence of dinosaur predator–prey interaction. It is suggested that an evolutionary increase in the size of dicynodonts across the Late Triassic may have been driven by selection pressure to reach a size refuge from early dinosaur predators. □Bite traces, dicynodonts, dinosaurs, predation, Triassic.     

A new Aspleniutn hybrid from Valencia (Spain) related to A. majoricum Litard

PANGUA, E., PRADA, C, PAJARON, S. & SALVO, E., 1992. A new Aspleniutn hybrid from Valencia (Spain) related to A. majoricum Litard . A new diploid Asplenium hybrid, found in the Iberian Peninsula (Valencia, Benifairo de Valldigna), is described and the name Asplenium x protomajoricum proposed. The plants exhibit c. 72^I at meiosis. The cytology and morphology of the hybrid and its occurrence between the assumed parentals suggest that it originated from a cross between A. fontanum and A. petrarchae subsp. bivalens. The occurrence of A. petrarchae subsp. bivalens in eastern Spain is confirmed cytologically. The occurrence of A. majoricum on the mainland is also discussed.     

Dinosaurs and the Cretaceous Terrestrial Revolution

The observed diversity of dinosaurs reached its highest peak during the mid- and Late Cretaceous, the 50 Myr that preceded their extinction, and yet this explosion of dinosaur diversity may be explained largely by sampling bias. It has long been debated whether dinosaurs were part of the Cretaceous Terrestrial Revolution (KTR), from 125-80 Myr ago, when flowering plants, herbivorous and social insects, squamates, birds and mammals all underwent a rapid expansion. Although an apparent explosion of dinosaur diversity occurred in the mid-Cretaceous, coinciding with the emergence of new groups (e.g. neoceratopsians, ankylosaurid ankylosaurs, hadrosaurids and pachycephalosaurs), results from the first quantitative study of diversification applied to a new supertree of dinosaurs show that this apparent burst in dinosaurian diversity in the last 18 Myr of the Cretaceous is a sampling artefact. Indeed, major diversification shifts occurred largely in the first one-third of the group's history. Despite the appearance of new clades of medium to large herbivores and carnivores later in dinosaur history, these new originations do not correspond to significant diversification shifts. Instead, the overall geometry of the Cretaceous part of the dinosaur tree does not depart from the null hypothesis of an equal rates model of lineage branching. Furthermore, we conclude that dinosaurs did not experience a progressive decline at the end of the Cretaceous, nor was their evolution driven directly by the KTR.     

Dinosaur extinction: closing the '3 m gap'

Modern debate regarding the extinction of non-avian dinosaurs was ignited by the publication of the Cretaceous-Tertiary (K-T) asteroid impact theory and has seen 30 years of dispute over the position of the stratigraphically youngest in situ dinosaur. A zone devoid of dinosaur fossils reported from the last 3 m of the Upper Cretaceous, coined the '3 m gap', has helped drive controversy. Here, we report the discovery of the stratigraphically youngest in situ dinosaur specimen: a ceratopsian brow horn found in a poorly rooted, silty, mudstone floodplain deposit located no more than 13 cm below the palynologically defined boundary. The K-T boundary is identified using three criteria: (i) decrease in Cretaceous palynomorphs without subsequent recovery, (ii) the existence of a 'fern spike', and (iii) correlation to a nearby stratigraphic section where primary extraterrestrial impact markers are present (e.g. iridium anomaly, spherules, shocked quartz). The in situ specimen demonstrates that a gap devoid of non-avian dinosaur fossils does not exist and is inconsistent with the hypothesis that non-avian dinosaurs were extinct prior to the K-T boundary impact event.     

Do feathered dinosaurs exist? Testing the hypothesis on neontological and paleontological evidence

The origin of birds and avian flight from within the archosaurian radiation has been among the most contentious issues in paleobiology. Although there is general agreement that birds are related to theropod dinosaurs at some level, debate centers on whether birds are derived directly from highly derived theropods, the current dogma, or from an earlier common ancestor lacking suites of derived anatomical characters. Recent discoveries from the Early Cretaceous of China have highlighted the debate, with claims of the discovery of all stages of feather evolution and ancestral birds (theropod dinosaurs), although the deposits are at least 25 million years younger than those containing the earliest known bird Archaeopteryx. In the first part of the study we examine the fossil evidence relating to alleged feather progenitors, commonly referred to as protofeathers, in these putative ancestors of birds. Our findings show no evidence for the existence of protofeathers and consequently no evidence in support of the follicular theory of the morphogenesis of the feather. Rather, based on histological studies of the integument of modern reptiles, which show complex patterns of the collagen fibers of the dermis, we conclude that "protofeathers" are probably the remains of collagenous fiber "meshworks" that reinforced the dinosaur integument. These "meshworks" of the skin frequently formed aberrant patterns resembling feathers as a consequence of decomposition. Our findings also draw support from new paleontological evidence. We describe integumental structures, very similar to "protofeathers," preserved within the rib area of a Psittacosaurus specimen from Nanjing, China, an ornithopod dinosaur unconnected with the ancestry of birds. These integumental structures show a strong resemblance to the collagenous fiber systems in the dermis of many animals. We also report the presence of scales in the forearm of the theropod ornithomimid (bird mimic) dinosaur, Pelecanimimus, from Spain. In the second part of the study we examine evidence relating to the most critical character thought to link birds to derived theropods, a tridactyl hand composed of digits 1-2-3. We maintain the evidence supports interpretation of bird wing digit identity as 2,3,4, which appears different from that in theropod dinosaurs. The phylogenetic significance of Chinese microraptors is also discussed, with respect to bird origins and flight origins. We suggest that a possible solution to the disparate data is that Aves plus bird-like maniraptoran theropods (e.g., microraptors and others) may be a separate clade, distinctive from the main lineage of Theropoda, a remnant of the early avian radiation, exhibiting all stages of flight and flightlessness.     

On the spinosaurid theropod teeth from the early Barremian (Early Cretaceous) Blesa Formation (Spain)

Spinosaurids are one of the most abundant theropods from the Early Cretaceous of the Iberian Peninsula. The published fossil record consists mainly of teeth. A good example is La Cantalera-1 site in the Blesa Formation (Spain). This site represents a marshy environment with periodic droughts, resulting in a non-permanent body of water. Theropod dinosaur teeth are frequent. Seventeen spinosaurid teeth have been studied using qualitative and quantitative features, including a statistical analysis, in order to compare them with the known spinosaurid record from Spain. In La Cantalera-1 we recognise two different morphotypes: Baryonychinae indet. and Spinosaurinae? indet. Baryonychinae indet. was produced by baryonychines close to Baryonyx; teeth with similar morphology have been described in other sites from the Early Cretaceous of the Iberian Peninsula. Teeth tentatively attributed to Spinosaurinae? indet. were produced by spinosaurines close to Spinosaurus. This morphotype could provide new evidence of the presence of spinosaurines in the Early Cretaceous of the Iberian Peninsula. The small size of the teeth from La Cantalera-1 when compared with those from other sites is interpreted as the result of the conditions characteristic of the deposit area, which represents an ecosystem unable to sustain large-sized organisms.     

First trace and body fossil evidence of a burrowing, denning dinosaur

A fossil discovery in the mid-Cretaceous Blackleaf Formation of southwest Montana, USA, has yielded the first trace and body fossil evidence of burrowing behaviour in a dinosaur. Skeletal remains of an adult and two juveniles of Oryctodromeus cubicularis gen. et sp. nov. a new species of hypsilophodont-grade dinosaur, were found in the expanded distal chamber of a sediment-filled burrow. Correspondence between burrow and adult dimensions supports Oryctodromeus as the burrow maker. Additionally, Oryctodromeus exhibits features of the snout, shoulder girdle and pelvis consistent with digging habits while retaining cursorial hindlimb proportions. Association of adult and young within a terminal chamber provides definitive evidence of extensive parental care in the Dinosauria. As with modern vertebrate cursors that dig, burrowing in Oryctodromeus may have been an important adaptation for the rearing of young. Burrowing also represents a mechanism by which small dinosaurs may have exploited the extreme environments of polar latitudes, deserts and high mountain areas. The ability among dinosaurs to find or make shelter may contradict some scenarios of the Cretaceous-Paleogene impact event. Burrowing habits expand the known range of nonavian dinosaur behaviours and suggest that the cursorial ancestry of dinosaurs did not fully preclude the evolution of different functional regimes, such as fossoriality.     

Los Cayos Dinosaur Tracksite: An Overview on the Lower Cretaceous Ichno-Diversity of the Cameros Basin (Cornago,La Rioja Province,Spain)

The Los Cayos dinosaur tracksite is located at the eastern sector of the Cameros Basin (Cornago Township, La Rioja province), NE Spain. The sediments consist of interbedded terrigenous siliciclastics and carbonates belonging to the Enciso Group (Early Cretaceous, Aptian in age). The sedimentological and faunal evidence suggests that these sediments were deposited in a low gradient lacustrine environment. Los Cayos constitutes a relatively wide area with at least 6 localities that have yielded dinosaur tracks. More than 2,000 dinosaur tracks have been discovered to date. Medium to large theropod dinosaurs constitute about 95% of the ichnofauna. Ornithopod dinosaur tracks have been reported from only one of the outcrops (Los Cayos D). Los Cayos S has yielded theropod and sauropod tracks. One sauropod trackway shows a narrow-gauge locomotion pattern and a manus print morphology suggesting that the trackmaker was a titanosaurid, or at least a titanosauriform sauropod. Some pterosaur manus impressions, avian-like footprints of small size and possible turtle tracks complete the assemblage of one of the most impressive and best-preserved dinosaur tracksites of the European Lower Cretaceous.     

A new basal ornithopod dinosaur from the Barremian of Galve,Spain

A partially articulated postcranial skeleton of a small ornithischian dinosaur, Gideonmantellia amosanjuanae nov. gen. et sp., from the Early Cretaceous of Galve (Teruel province, Spain) is described. It was recovered in an outcrop of fluvial red clays from the Camarillas Formation, which is Barremian in age. This partial skeleton is recognised as a new ornithopod taxon by the following autapomorphies: (1) postacetabular process of the ilium with a brevis shelf that is noticeably medially expanded in its cranial part but narrow and horizontal in its caudal part; (2) rod-like prepubic process with its anterior end twisted and expanded; and (3) L-shaped first chevron. Our phylogenetic analysis indicates that Gideonmantellia represents a basal ornithopod taxon more derived than Orodromeus, the “Asian clade” (which includes Haya and others) and Hypsilophodon.     

New Insights into Non-Avian Dinosaur Reproduction and Their Evolutionary and Ecological Implications: Linking Fossil Evidence to Allometries of Extant Close Relatives

It has been hypothesized that a high reproductive output contributes to the unique gigantism in large dinosaur taxa. In order to infer more information on dinosaur reproduction, we established allometries between body mass and different reproductive traits (egg mass, clutch mass, annual clutch mass) for extant phylogenetic brackets (birds, crocodiles and tortoises) of extinct non-avian dinosaurs. Allometries were applied to nine non-avian dinosaur taxa (theropods, hadrosaurs, and sauropodomorphs) for which fossil estimates on relevant traits are currently available. We found that the reproductive traits of most dinosaurs conformed to similar-sized or scaled-up extant reptiles or birds. The reproductive traits of theropods, which are considered more bird-like, were indeed consistent with birds, while the traits of sauropodomorphs conformed better to reptiles. Reproductive traits of hadrosaurs corresponded to both reptiles and birds. Excluding Massospondylus carinatus , all dinosaurs studied had an intermediary egg to body mass relationship to reptiles and birds. In contrast, dinosaur clutch masses fitted with either the masses predicted from allometries of birds (theropods) or to the masses of reptiles (all other taxa). Theropods studied had probably one clutch per year. For sauropodomorphs and hadrosaurs, more than one clutch per year was predicted. Contrary to current hypotheses, large dinosaurs did not have exceptionally high annual egg numbers (AEN). Independent of the extant model, the estimated dinosaur AEN did not exceed 850 eggs (75,000 kg sauropod) for any of the taxa studied. This estimated maximum is probably an overestimation due to unrealistic assumptions. According to most AEN estimations, the dinosaurs studied laid less than 200 eggs per year. Only some AEN estimates obtained for medium to large sized sauropods were higher (200-400 eggs). Our results provide new (testable) hypotheses, especially for reproductive traits that are insufficiently documented or lacking from the fossil record. This contributes to the understanding of their evolution.     

First dinosaur tracks from the Arabian Peninsula

Background

The evolutionary history of Mesozoic terrestrial vertebrates from the Arabian Peninsula is virtually unknown. Despite vast exposures of rocky outcrops, only a handful of fossils have yet been described from the region. Here we report a multi-taxon dinosaur track assemblage near Madar village, 47 km north of Sana''a, Republic of Yemen. This represents the first dinosaur tracksite from the Arabian Peninsula, and the only multi-taxon dinosaur ichnosite in the Middle East.

Methodology/Findings

Measurements were taken directly from trackway impressions, following standard ichnological conventions. The presence of bipedal trackmakers is evidenced by a long series of pes imprints preserving smoothly rounded posterior margins, no evidence of a hallux, bluntly rounded digit tips and digital divarication angles characteristic of ornithopod dinosaurs. Nearby, eleven parallel quadrupedal trackways document a sauropod herd that included large and small individuals traveling together. Based on the morphology of manus impressions along with a narrow-gauged stance, the quadrupedal trackways were made by non-titanosauriform neosauropods. Additional isolated tracks and trackways of sauropod and ornithopod dinosaurs are preserved nearby.

Conclusions/Significance

Taken together, these discoveries present the most evocative window to date into the evolutionary history of dinosaurs of the Arabian Peninsula. Given the limited Mesozoic terrestrial record from the region, this discovery is of both temporal and geographic significance, and massive exposures of similarly-aged outcrops nearby offer great promise for future discoveries.