Biomechanics of sauropod dinosaurs

Biomechanics is the study of the structures, motions and mechanical properties of natural organisms. It is applied in different fields to develop new instruments or devices, such as engineering, medical applications, veterinary, etc... An example is the study of the walking abilities of geckos, which brought the scientists to look at the fingers of these lovely reptiles. The fingers are covered with microscopic hairs, or spatulae, each of these hairs generates adhesion force, and the sum of all the microscopic adhesion forces is more than the weight of the animal, allowing it to climb upside down on our ceilings. This application is being developed to produce gloves able to make a man climb on the glass.

  

Here is a photograph of a gecko on a glass.

In palaeontology the biomechanics is mainly used to estimate the forces acting on the bones while the animal was alive, with the aim to reconstruct its ecological niche and as method of comparison. Biomechanics is mainly based on Finite Element Analyses. FEA is a computer process that allows the simulation of the application of a force over a 3D model of an object. The model of the bones, in the case of palaeontology, is divided into microscopic cubes then it is imported into the software. The division in cubes is necessary to allow the computer to perform simple calculations. For each cube of the model, there are six vectorial equations per instant of the simulation, and each model is composed of thousands, or even millions, of cubes. The entire process could take weeks of simulations. The output of the simulation is the stress under which the object is subjected by the force applied. When the stress surpasses the value of resistance of the material of the object, the object breaks. This entire process saves lots of costs, since different simulations can be run on the same object virtually breaking it infinite times. The use of computer simulations in palaeontology is the only way to estimate these forces, since the original material components of the bones have been replaced during fossilization, in fact, if we would use a real fossil to perform the analyses we would obtain results coinciding with the properties of the rocks which compose the fossil, with no real meaning.

Simulation of an oscillation of a beam. The brighter the color the major deformation is affecting the beam

Why should we be interested in breaking sauropod dinosaur bones?

Sauropoda is a clade of dinosaurs that evolved during the Late Triassic, surviving to the latest Cretaceous, being among the most successful animal that ever inhabited Earth. Sauropod dinosaurs are one of the most intriguing and famous dinosaurs, characterized by their long neck, tails, and enormous bodies. These animals have achieved the largest dimensions among terrestrial vertebrates (Curry & Wilson, 2005). Only a few animals have achieved dimensions comparable to little/medium-sized sauropods: some species of hadrosaurid (duck-billed) dinosaurs and a handful of species of mammals. A comparable size nowadays would be an airliner of middle dimensions, and still, the masses of airliners would be smaller than the ones of some species of sauropod dinosaurs.

Estimated masses of a moose, an elephant a Tyrannosaurus rex, and different sauropod dinosaurs compared to a Boeing airliner.

Sauropod remains have been found in every continent and they reached the greatest diversity during the Late Jurassic, when different lineages were sharing the same environments. Despite at first sight the sauropod dinosaurs may seem all similar, sharing the elongated neck, tail and round bodies supported by columnar limbs, their shapes changed a lot during their evolution and created different lineages. The most diverse group and the longest to survive have been the Titanosauria, a group of sauropod dinosaurs that evolved from the Macronaria, during the Late Jurassic and survived to the end of the Mesozoic. This group of animals has achieved the largest dimensions among terrestrial vertebrates, with estimated masses more than 50 tonnes. The Macronaria, from which descends all the titanosaurian sauropods, includes one of the most famous dinosaur: Brachiosaurus. These taxa of sauropod dinosaurs are estimated to have maintained the neck in an inclined position, between 30° and 45°. Among Macronaria have been found also the smallest sauropod dinosaurs, like Europasaurus holgeri Sander et al., 2006, a relative of Brachiosaurus that inhabited Europe during the Late Jurassic, and the littlest sauropod known, Majarosaurus dacus (von Nopcsa, 1915), an insular dwarf titanosaur that inhabited Europe during the Late Cretaceous, that is estimated to weigh around 900kg as an adult. Though the most famous group of sauropod dinosaurs may be considered the family of Diplodocidae, with Diplodocus and the renowned Brontosaurus. This family was most diverse during the Late Jurassic, but went extinct during the Early Cretaceous. The neck of these animals shows different adaptations compared to other sauropods, and it is estimated that the neck was held in a near-horizontal position, parallel to the ground, opposite to an elongated tail. The tail was elongated, counting up to 82 elements, and a joint study of engineers and paleontologists (Myrvhold & Currie, 1997) showed that the tail was able to reach supersonic speeds, hypothesizing the use as defensive weapon or sound maker device. 

These animals are extremely fascinating, having survived for more than 150 million years, being subjected to the pressure of natural selection and evolved in the largest terrestrial animals as well as evolved in insular dwarf forms. We, as a team, are interested to investigate how their skeleton was able to sustain such large bodies, and how the shape of the bones may have helped them be so successful in their evolutionary history.

References:

Curry Rogers, K., Ericsson, G.M., 2005. Sauropod histology. In: Curry Rogers, K.A.,Wilson, J.A. (Eds.), The Sauropods, Evolution and Paleobiology. University of California Press, Berkeley, pp. 303–326.

Lacovara, K., Lamanna, M., Ibiricu, L. et al. A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina. Sci Rep 4, 6196 (2015). https://doi.org/10.1038/srep06196

Myhrvold, N., & Currie, P. (1997). Supersonic sauropods? Tail dynamics in the diplodocids. Paleobiology, 23(4), 393-409. doi:10.1017/S0094837300019801

Sander, P., Mateus, O., Laven, T. et al. (2006). Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur. Nature 441, 739–741. https://doi.org/10.1038/nature04633

Nopcsa, F (1915). "Die Dinosaurier der siebenburgischen Landesteile Ungarns". Ungar. Geol. Reichsanst. 23: 1–26.

Photographs sources: https://upload.wikimedia.org/wikipedia/en/1/14/Gecko_on_window.jpg

https://upload.wikimedia.org/wikipedia/commons/c/cb/Beam_mode_6.gif

https://upload.wikimedia.org/wikipedia/commons/6/64/Dreadnoughtus_Mass_Comparison_%28Metric%29.jpg

Introduction to modern amphibians

Introduction to modern amphibians

Let’s talk about amphibians! When it comes to those cute, little animals, living both in water and on land, everyone has in mind the small frogs and salamanders that dwell in ponds and rivers. One can also consider the newts or the unique axolotl, an animal keeping a neotenic form. Few would include those limbless worm-like animals, the caecilians. However, if identifying amphibians may seem trivial nowadays, because of their peculiar characteristics, such as their ontogeny, the actual term “Amphibia” appears to be quite loose in systematics.

Here is the first article of a series that will present you the coolest vertebrates and all the problematic brought by this group.

Figure 1: Some example of modern amphibians. Clockwise, a South American caecilian, a fire salamander, Paedophryne amauensis (the smallest vertebrate known), a common reed frog, a Pacific newt, and an axolotl.

I)              An obscure definition for a mysterious clade: problematic in taxonomy.

First, we need to understand what an amphibian is. Amphibia comes from the Greek ἀμφίβιος (amphíbios), which “both kinds of life” or “living on both sides”. For a long time, it was used to describe animals that could reside at once in water and on land. However, taxonomic problems quickly rose with this wide application. On the one hand, it appeared that modern “amphibians” were closely related together than with any tetrapod group, forming a clade then named Lissamphibia. And on the other hand, more and more fossil taxa were identified as “amphibians”, the term referring then to any non-amniote tetrapod.

In other words, Amphibia became, sensu lato, a paraphyletic grade, including Lissamphibia, but also temnospondyls, lepospondyls, and all the stem-tetrapod taxa (which illustrate the transition from water to land, such as Ichthyostega or Acanthostega). Since then, biologists and paleontologists are not agreeing on what should be called “Amphibia”. Nonetheless, common ground can be found.

Figure 2: Evolution of Amphibia taxonomy. On top, the old-fashion way, where Amphibia (dark purple) was referring to all animals living both in water and on land, and can be used in ecological context (=amphibious). On bottom, the necessity to respect taxonomy and splits the groups of stem-tetrapods (blue) and stem-amniotes (red), and where Amphibia is synonymous of Batrachomorpha, the most inclusive clade containing Lissamphibia (light purple) and their stem-taxa. Modified from Benton, 2014.

From an ecological point of view, it is still acceptable to refer to “amphibians” for animals sharing this unique way of life. However, it would require distinguishing stem-tetrapods, stem-lissamphibians, and stem-amniotes. Also, since they are not the only vertebrates to have adopted the environment of the land-water interface through Evolution (nowadays, seals and crocodiles illustrate such adaptations), some authors would rather refer to them as “amphibious taxa” (van der Valk, 2012).

And from a systematic point of view, Amphibia would now be defined to include lissamphibians and their stem-groups, which would make it synonymous of Batrachomorpha. On the same note, Lissamphibia will then be comprised by all modern taxa and their stem relatives, namely Apoda (the caecilians), Salientita (frogs), and Urodela (salamanders and newts). Some authors argue that the extinct Albanerpetontidae would also be part of Lissamphibia.

II)            An overview of Lissamphibia.

Lissamphibians are represented today by over 8,000 species (AmphibiaWeb, 2020), with a worldwide distribution with the exception of Antarctica. Although the biggest diversity is observed in tropical regions, some species extant up to the North Pole and down to Tierra del Fuego, the meridional-most point of South America. Among the most common features shared by lissamphibians are the four digits or double occipital condyles, but those characteristics are also found in non-lissamphibian fossils.

Nonetheless, molecular analysis strongly supported both the group’s monophyly and its position as sister-group of amniotes. On top of that, lissamphibians shared a set of physiological, ecological and osteological autapomorphies:

1.     they are ectotherm animals, which means they rely mostly on environment to control the heat of their temperature;

2.     their skin is rich in glands with a thin stratum corneum (the outermost layer of epidermis);

3.     their eyes are covered by an eyelid;

4.     they have a tricameral heart, with three chambers: two atria and one ventricle;

5.     their ontogeny involves a larval stage with external gills going through metamorphosis, and therefore a biphasic life-cycle;

6.     their skeleton is poorly ossified, either because of loss, reduction or fusion of the bones, notably in the skull;

7.     their gonads have large fat bodies, used as an extra source of energy;

8.     their teeth are bicuspid, usually with attached to the inner jaw (pleurodonty), where the crown and the root are not fused but connected by fibrous poorly mineralized tissue (pedicelly), giving flexibility;

9.     they have a canalis perioticus, a channel that connects the perilymphatic sac and the perilymphatic cistern in the inner ear

10.  they have a papilla amphibiorum, which is the second sense receptor in the inner ear and works within 600 to 1000 Hz range;

11.  the radius and the ulna articulate with a single enlarged, ossified structure on the humerus (radial condyle).

Figure 3: Pedicellate teeth, as represented by the three modern amphibian orders. A, the salamander Amphiuma means. B, the caecilian Gymnopis mexicanus. C, the frog Rana occipitalis. D, the leptodactylid frog Calyptocephalus gayi. From Carroll, 2009.

Among additional features, can be noted the intermaxillary glands, the short ribs and the palatal opening between the pterygoid and the parasphenoid, but those also occurred in other Paleozoic taxa, such as temnospondyls.

Next time, we’ll see the different groups that constitute Lissamphibia.

Bibliography and recommended sources

AmphibiaWeb. 2020. Browse by Family. AmphibiaWeb. Available at http://amphibiaweb.org:8000/lists/index.shtml. Accessed March 24, 2020.

Benton, M. J. 2014. Vertebrate Palaeontology, 4th ed. John Wiley & Sons, Chichester, 480 pp.

Carroll, R. L. 2009. The Rise of Amphibians: 365 Million Years of Evolution. Johns Hopkins University Press, Baltimore, MD, 544 pp.

Schoch, R. R. 2014. Amphibian Evolution: The Life of Early Land Vertebrates. John Wiley & Sons, Oxford, 276 pp.

van der Valk, A. 2012. The Biology of Freshwater Wetlands, 2nd ed. Oxford University Press, New York City, NY, 296 pp.

Curso de Desenho de Natureza

O biólogo e ilustrador português Pedro Salgado, vencedor da quinta edição da Illustraciencia – Prémio Internacional de Ilustração Científica, com a ilustração de quatro espécies de peixes do Mediterrânico, leccionará de 28 de Setembro de 2017 a 28 de Junho de 2018, no Museu Nacional de História Natural e da Ciência, em Lisboa, o curso livre de Desenho de Natureza.

Já na sua quinta edição, destina-se ao público geral e estudantes de arte ou ciência a partir dos 16 anos, com interesse em desenho de observação e biologia, com ou sem experiência em desenho. O programa curricular genérico inclui ainda diversas saídas de campo e residências artísticas:

1.º trimestre – desenho de campo, desenho científico

Técnicas a P/B tonal (grafite, carvão, aguada monocromática) e linha (contorno, ponteado e linha cruzada). 

Demonstração, experimentação e desenvolvimento de projetos.

2.º trimestre – desenho de campo, desenho científico

Técnicas de cor (aguarela, guache, lápis de cor, técnicas mistas)

Demonstração, experimentação e desenvolvimento de projetos.

3.º trimestre – desenho de campo, desenho científico

Projetos avançados analógicos, tratamento e aplicações digitais 

Demonstração, experimentação e desenvolvimento de projetos.

Construção de portfólio.

Mais informações e inscrições em: 

http://www.museus.ulisboa.pt/pt-pt/node/1788

Portugal tem uma nova espécie de anuro actual: o sapinho-português, Pelodytes atlanticus

Portugal tem uma nova espécie de anuro actual: o sapinho-português, Pelodytes atlanticus. 

O sapinho-de-verrugas-verdes, cientificamente conhecido por Pelodytes punctatus, que se julgava ocorrer em Portugal afinal é uma espécie diferente do que se pensava até hoje. Este anuro actual que ocorre em Portugal afinal trata-se de uma nova espécie agora baptizada de Pelodytes atlanticus por Jesús Díaz-Rodriguez e colegas numa publicação de Zootaxa.

Conforme a distribuição apresentada no artigo, esta nova espécie ocorre exclusivamente em Portugal, sendo por isso, a nosso conhecimento, a única espécie de tetrápode actual endémica e exclusiva de Portugal continental.

Como os autores não sugerem um nome comum e por este sapinho ter uma distribuição restrita ao território de Portugal, sugiro, que esta espécie receba o nome vernáculo de sapinho-português!

Sapinho-português, Pelodytes atlanticus nov. sp. (Díaz-Rodriguez et al. 2017)

Distribuição de Pelodytes (transformado a partir de Díaz-Rodriguez et al. 2017)

Filogenia de Pelodytes (Díaz-Rodriguez et al. 2017)

DÍAZ-RODRÍGUEZ, J.E.S.Ú.S., GEHARA, M., MÁRQUEZ, R., VENCES, M., GONÇALVES, H., SEQUEIRA, F., MARTÍNEZ-SOLANO, I.Ñ.I.G.O. and TEJEDO, M., 2017. Integration of molecular, bioacoustical and morphological data reveals two new cryptic species of Pelodytes (Anura, Pelodytidae) from the Iberian Peninsula. Zootaxa, 4243(1), pp.1-41.

Baleias-de-bico em nova tese em paleontologia por João Muchagata

A estrutura bizarra no crânio da baleia-de-bico extinta Globicetus hiberus levou à tese por João Muchagata integrado no Mestrado em Paleontologia da FCT-Universidade Nova de Lisboa + Universidade de Évora. Parabéns ao João Muchagata que agora é Mestre com uma classificação de 18 valores.

Data: 18 de Maio de 2016
Mestrado em Paleontologia
Dissertação: "Função, dimorfismo sexual e variação intraespecífica das estruturas rostrais bizarras na baleia-de-bico extinta Globicetus hiberus"
Júri: Doutores Carlos Ribeiro (UÉ), Mário Estevens (CM Almada) e Octávio Mateus (FCT-UNL, orientador).

Defesa de tese de João Muchagata: candidato, júri e orientadores.

Resumo: Zifídeos são odontocetes ecolocalizadores capazes de efetuar mergulhos de grande profundidade. O recentemente nomeado Globicetus hiberus do Plioceno, exibe uma peculiar e grande esfera óssea no rostro, o processo mesorostral da pré-maxila ou MPP. A origem e função do MPP é misterioso, mas algumas hipóteses são abordadas: 1. malformação, doença ou deformidade; 2. lastro; 3. luta intraespecífica; 4. reflexão e orientação do feixe de som; 5. aumento da velocidade das ondas sonoras; 6. barreira sonora; e 7. órgão sexual. Algumas hipóteses são rejeitadas (1, 2, 6), outros podem desempenhar um papel secundário (3, 4, 5) e sugerimos o órgão sexual secundário (7) como a melhor hipótese. O MPP varia de tamanho nos seis espécimes estudados. Durante a vida, o MPP cresce alométricamente nos machos, mas não nas fêmeas, o que sugere que é um caso de dimorfismo sexual. Estas baleias seriam capazes de detetar ossos como imagens ecóicas distintas, portanto, o MPP poderia funcionar como um órgão sexual secundário, a chamado hipótese das “hastes internas”.

Espinossauros de Marrocos: estudo confirma a existência de duas espécies

O dinossauro predador Spinosaurus engolia peixes como os actuais pelicanos fazem. Esta é uma das conclusões de um estudo pela Universidade Nova de Lisboa. Ossos da mandíbula destes grandes dinossauros se alimentam de peixes conhecidos como espinossauros mostram que mandíbula destes animais abria lateralmente para melhor abranger a presa, de acordo com um artigo publicado na revista PLOS ONE, por Christophe Hendrickx e Octávio Mateus da Universidade Nova de Lisboa e Museu da Lourinhã, e Eric Buffetaut, de CNRS de Paris.

Two spinosaur species feeding of fish in the Kem Kem environment of Southeastern Morocco around 100 million years ago. Artwork by Sergey Krasovskiy (http://atrox1.deviantart.com/gallery/), advised by Christophe Hendrickx, Serjoscha Evers, Andrea Cau and Scott Hartman.

O estudo revela que o alargamento lateral da mandíbula inferior foi possível em Spinosaurus graças a uma articulação solta e móvel entre as partes esquerda e direita da mandíbula. "Os Spinosaurus eram animais piscívoros muito estranhos com um crânio semelhante ao de um crocodilo com um focinho longo e estreito e dentes cónicos", explicou Octávio Mateus. "Evidências diretas indicam que estes dinossauros eram comedores de peixe, e nosso estudo mostra, pela primeira vez, que eles eram capazes de engolir grandes presas, de uma forma semelhante como nossos pelicanos que vivem", acrescentou Hendrickx.

Os cientistas dizem que os ossos de vários crânios também mostram a presença de duas espécies de espinossauros no Cretácico de Marrocos, há cerca de cem milhões de anos atrás. A primeira espécie foi identificada pelos paleontólogos como Spinosaurus aegyptiacus, um dinossauro semi-aquático e um dos maiores predadores terrestres. "Esta linhagem de dinossauros predadores que levou ao Spinosaurus pode ser rastreada até ao período Jurássico, tendo, gradualmente, adaptado-se a um novo estilo de vida semi-aquático", disse Eric Buffetaut, um co-autor da publicação do CNRS em França.

Spinosaurus foi recentemente considerado como um animal quadrúpede com ossos densos e pernas curtas adaptadas à natação, com base em novos materiais fósseis da mesma região de Marrocos. Hendrickx e colegas, no entanto, mostram a presença de mais de uma espécie de espinossauros nesses depósitos e lançam dúvidas sobre a precisão da reconstrução de um Spinosaurus quadrúpede de pernas curtas, o que pode ter sido baseada em elementos de vários animais distintos. "Só a descoberta de fósseis adicionais de Marrocos poderá confirmar a nossa hipótese de a presença de mais de uma espécie de espinossauros no Cretácico Superior do Norte de África", concluiu Hendrickx.

Morphology of the upper jaw bone belonging to two species of spinosaurs. Reconstruction by Christophe Hendrickx.

Publication reference: Hendrickx, C., Mateus, O. and Buffetaut, E. 2016. Morphofunctional analysis of the quadrate of Spinosauridae (Dinosauria: Theropoda) and the presence of Spinosaurus and a second spinosaurine taxon in the Cenomanian of North Africa. PLOS ONE.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144695

Supplementary information, including illustrations, are available at https://drive.google.com/open?id=0B2-1jKWHZywJeVZ5RjR2MVBFMXM

The Belgian paleontologist Dr. Christophe Hendrickx, leading author of the study. Photo taken by Octávio Mateus.

Notícias frescas... da Gronelândia

Três novos artigos científicos dão-nos notícias frescas sobre a paleontologia do Triásico da Gronelândia, resultado da expedição de 2012 e publicadas agora na Geological Society, Special Publications.

Lars Clemmensen e colegas fazem o sumário das descobertas de vertebrados e da geologia.

Resumo:
In Late Triassic (Norian–Rhaetian) times, the Jameson Land Basin lay at 40° N on the northern part of the supercontinent Pangaea. This position placed the basin in a transition zone between the relatively dry interior of the supercontinent and its more humid periphery. Sedimentation in the Jameson Land Basin took place in a lake–mudflat system and was controlled by orbitally forced variations in precipitation. Vertebrate fossils have consistently been found in these lake deposits (Fleming Fjord Formation), and include fishes, dinosaurs, amphibians, turtles, aetosaurs and pterosaurs. Furthermore, the fauna includes mammaliaform teeth and skeletal material. New vertebrate fossils were found during a joint vertebrate palaeontological and sedimentological expedition to Jameson Land in 2012. These new finds include phytosaurs, a second stem testudinatan specimen and new material of sauropodomorph dinosaurs, including osteologically immature individuals. Phytosaurs are a group of predators common in the Late Triassic, but previously unreported from Greenland. The finding includes well-preserved partial skeletons that show the occurrence of four individuals of three size classes. The new finds support a late Norian–early Rhaetian age for the Fleming Fjord Formation, and add new information on the palaeogeographical and palaeolatitudinal distribution of Late Triassic faunal provinces.

Jameson Land, na Gronelândia.

Malmos Klint na Gronbelândia (Clemmensen et al. 2015)

Geologia do Triásico da Gronbelândia (Clemmensen et al. 2015)

Pegadas de sauropodomorfos (Clemmensen et al. 2015)

Clemmensen, L.B., Milàn, J., Adolfssen, J.S., Estrup, E.J., Frobøse, N., Klein, N., Mateus, O. and Wings, O., 2015. The vertebrate-bearing Late Triassic Fleming Fjord Formation of central East Greenland revisited: stratigraphy, palaeoclimate and new palaeontological data. Geological Society, London, Special Publications, 434, pp.SP434-3. PDF

Bitten Hansen et al. (2015) abordam a descoberta de numerosos coprólitos de tubarão e outros animais do Triásico de Kap Stewart, nomeadamente a morfologia, classificação e alimentação.

Resumo:
A large collection of vertebrate coprolites from black lacustrine shales in the Late Triassic (Rhaetian–Sinemurian) Kap Stewart Formation, East Greenland is examined with regard to internal and external morphology, prey inclusions, and possible relationships to the contemporary vertebrate fauna. A number of the coprolites were mineralogically examined by X-ray diffraction (XRD), showing the primary mineral composition to be apatite, clay minerals, carbonates and, occasionally, quartz in the form of secondary mineral grains. The coprolite assemblage shows multiple sizes and morphotypes of coprolites, and different types of prey inclusions, demonstrating that the coprolite assemblage originates from a variety of different producers.

.

Localidade com coprólitos de tubarão na Gronelândia (Hansen et al., 2015)

Coprólitos de tubarão da Gronelândia (Hansen et al., 2015)

Coprólitos (Hansen et al., 2015)

Hansen, B.B., Milàn, J., Clemmensen, L.B., Adolfssen, J.S., Estrup, E.J., Klein, N., Mateus, O. and Wings, O., 2015. Coprolites from the Late Triassic Kap Stewart Formation, Jameson Land, East Greenland: morphology, classification and prey inclusions. Geological Society, London, Special Publications, 434, pp.SP434-12. PDF

Hendrik Klein e colegas anunciam a descoberta de pegadas de Brachychirotherium, normalmente atribuídas a arcossauros.

Resumo:

The Ørsted Dal Member of the Upper Triassic Fleming Fjord Formation in East Greenland is well known for its rich vertebrate fauna, represented by numerous specimens of both body and ichnofossils. In particular, the footprints of theropod dinosaurs have been described. Recently, an international expedition discovered several slabs with 100 small chirotheriid pes and manus imprints (pes length 4–4.5 cm) in siliciclastic deposits of this unit. They show strong similarities withBrachychirotherium, a characteristic Upper Triassic ichnogenus with a global distribution. A peculiar feature in the Fleming Fjord specimens is the lack of a fifth digit, even in more deeply impressed imprints. Therefore, the specimens are assigned here tentatively to cf. Brachychirotherium. Possibly, this characteristic is related to the extremely small size and early ontogenetic stage of the trackmaker. The record from Greenland is the first evidence of this morphotype from the Fleming Fjord Formation. Candidate trackmakers are crocodylian stem group archosaurs; however, a distinct correlation with known osteological taxa from this unit is not currently possible. While the occurrence of sauropodomorph plateosaurs in the bone record links the Greenland assemblage more closer to that from the Germanic Basin of central Europe, here the described footprints suggest a Pangaea-wide exchange.

Brachychirotherium (Klein et al. 2015) 

Brachychirotherium (Klein et al. 2015) 

Klein, H., Milàn, J., Clemmensen, L.B., Frobøse, N., Mateus, O., Klein, N., Adolfssen, J.S., Estrup, E.J. and Wings, O., 2015. Archosaur footprints (cf. Brachychirotherium) with unusual morphology from the Upper Triassic Fleming Fjord Formation (Norian–Rhaetian) of East Greenland. Geological Society, London, Special Publications, 434, pp.SP434-1. PDF


#Gronelândia

A vida agitada e perigosa de Allosaurus fragilis

O novo artigo publicado no PeerJ reforça a vida agitada e perigosa do dinossauro carnívoro Allosaurus fragilis.

Esqueleto original de Allosaurus fragilis

Escápula de Allosaurus fragilis

Novas perspectivas sobre o estilo de vida de Allosaurus (Dinosauria: Theropoda) com base noutro espécime com múltiplas patologias

Os terópodes (dinossauros carnívoros) adultos de grande porte são frequentemente encontrados com numerosas patologias. Um grande e quase completo, espécime provavelmente adulto de Allosaurus do Howe Stephens Quarry, Formação Morrison, Wyoming, mostra várias patologias. Ossos patológicos incluem o dentário esquerdo, duas vértebras cervicais, uma cervical e várias costelas dorsais, a escápula esquerda, o úmero esquerdo, ísquio direito, e duas falanges do pé. Estas patologias podem ser classificadas da seguinte forma: a quinta vértebra cervical, escápula, várias costelas e ísquio estão traumátizadas, e um calo na falange II-2 é traumático-infecciosa. Traumaticamente elementos fraturados expostos ao movimento frequente (por exemplo, a escápula e as costelas) mostram uma tendência a desenvolver pseudartroses em vez de calo. As patologias na quarta cervical são mais susceptíveis de serem idiopática, e no úmero esquerdo é infecciosa ou idiopática, enquanto pedal esquerdo falange IV-1 é classificada como idiopática. Com excepção do ísquio, todos os elementos patológicos traumáticas / traumáticas infecciosa mostrar evidências inequívocas de cura, o que indica que as respectivas patologias não causou a morte desse indivíduo. Alinhamento das patologias na escápula e de costelas do lado esquerdo sugere que tudo pode ter sido causado por um único evento traumático. A fratura isquiática pode ter sido fatal. A ocorrência de múltiplas patologias traumáticas novamente sublinha que terópodes de grande porte experimentou lesões frequentes durante a vida, o que indica um estilo de vida predatório activo. Sinais de infecções são escassas e restringidas localmente, indicando o sucesso na prevenção da disseminação de agentes patogénicos, como é o caso nos répteis existentes (incluindo as aves).


New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies

Abstract:
Adult large-bodied theropods are often found with numerous pathologies. A large, almost complete, probably adult Allosaurus specimen from the Howe Stephens Quarry, Morrison Formation (Late Kimmeridgian–Early Tithonian), Wyoming, shows multiple pathologies. Pathologic bones include the left dentary, two cervical vertebrae, one cervical and several dorsal ribs, the left scapula, the left humerus, right ischium, and two left pedal phalanges. These pathologies can be classified as follows: the fifth cervical vertebra, the scapula, several ribs and the ischium are traumatic, and a callus on the shaft of the left pedal phalanx II-2 is traumatic-infectious. Traumatically fractured elements exposed to frequent movement (e.g. the scapula and the ribs) show a tendency to develop pseudarthroses instead of callus healing. The pathologies in the lower jaw and a reduced flexor tubercle of the left pedal phalanx II-2 are most likely traumatic or developmental in origin. The pathologies on the fourth cervical are most likely developmental in origin or idiopathic, that on the left humerus is infectious or idiopathic, whereas left pedal phalanx IV-1 is classified as idiopathic. With exception of the ischium, all traumatic / traumatic-infectious pathologic elements show unambiguous evidences of healing, indicating that the respective pathologies did not cause the death of this individual. Alignment of the scapula and rib pathologies from the left side suggests that all may have been caused by a single traumatic event. The ischial fracture may have been fatal. The occurrence of multiple traumatic pathologies again underlines that large-bodied theropods experienced frequent injuries during life, indicating an active predatory lifestyle, and their survival perhaps supports a gregarious behavior for Allosaurus. Signs of infections are scarce and locally restricted, indicating a successful prevention of the spread of pathogens, as it is the case in extant reptiles (including birds).




Foth C, Evers S, Pabst B, Mateus O, Flisch A, Patthey M, Rauhut OWM.(2015) New insights into the lifestyle of Allosaurus (Dinosauria: Theropoda) based on another specimen with multiple pathologies. PeerJ PrePrints3:e824v1 http://dx.doi.org/10.7287/peerj.preprints.824v1