A new albanerpetontid species found in amber!

 Amber secrets reveal a new species!

 

 

Last November, a paper published in the prestigious journal Science described an enigmatic fossil found in the Burmese ambers: a skull completely preserved! Not only is such a finding unique, but the authors used this material, and other previously described, to erect a new species of the mysterious amphibian group Albanerpetontidae: Yaksha perettii. This would be one of the best preserved 3D-skull of this group, and also the second species occurring in Asia. Indeed, the Asian fossil record of these tiny amphibians has been really scarce, with only some unidentified bones from Uzbekistan and a skull from Japan. Aged from early Cenomanian (about 99.6 and 93.5 million years ago), this new species would be contemporaneous of the occurrences found in central Asia.

Figure 1: A new albanerpetontid species sheds light on their peculiar feeding strategy (illustration by Stephanie Abramowicz, from Daza et al., 2020).

Named, after a mythical spirit in Eastern belief and Adolf Peretti (director of the Peretti MuseumFoundation and GemResearch Swisslab, who found the fossil), this new albanerpetontid provided lots of surprises and features that allowed paleontologist to understand better these animals now extinct. This new species is based on three specimens: the holotype (comprised of the skull), another specimen that preserved the post-cranial skeleton, and a paratype comprised of a juvenile with the cranial and post-cranial skeleton, which had been previously described as a stem Chamaeleonidae.

 

With the computed tomography, the authors were able to capture in detail the specimens and describe them, without breaking their protective amber. The holotype is the first fully articulated 3D-skull recovered from this group. It reveals the presence of epipterygoids in contact with the quadrate (making it a core element of the jaw suspension), a complete and fully articulated braincase (rarely found in this group), and, most striking, a long median hyoid entoglossal process with soft tissues attached! More soft tissues have been recovered, confirming the presence of scaly eyelids, claw sheaths and minute body scales.

The specimen exhibits large fenestrae in the roof of the cranial cavity, but this one is not homologous to the supratemporal fenestrae found in amniotes, as only the parietals participate to its structure and it opens in the adductor chamber. Thanks to this specimen, it is now known the orbital in albanerpetontids is framed by the lacrimal, the prefrontal, the frontal, the parietal and the jugal, but not by the maxilla. The holotype also provides the first complete palate, a region of the skull that was never described before. It yields large choanae separated by a narrow vomerine bar and large palatines forming independent structures. The pterygoid shape differs from the one observed in frogs and salamanders: the palatal portion meets the posterior ridge of the vomer and there is not pterygoid flange, the tapering posterior edge meeting with the medial side of the quadrate.

Figure 2: A and B, holotype and paratype of Yaksha perettii in their amber gangue; C to E, high-resolution computed tomography (HRCT) of the holotype with jaws articulated in lateral, dorsal, and ventral views (modified from Daza et al., 2020).

The other specimens confirmed the presence of four-digit manus, with curved ungual phalanges, and the tripartite composition of the pelvic girdle (the first fully articulated pelvis recovered). Most interesting is that albanerpetontids seem to have a pelvis supported by two sacral ribs, where lissamphibians have typically only one. The shape of the iliac blade, similar to that of chameleons would have allowed the legs to be angled ventrally for climbing. It also appears there is ontogenetic variation in the dentition, with juveniles having conical teeth with expanded roots and acute apex, and adults having tubular teeth with a more regular diameter between the root and the apex. The specimens also provided evidence of tooth replacement for the first time, and suggest it would slow with age.

 

With a specimen of that importance and quality, seven diagnostic characters have been used to erect the new species: (1) paired robust premaxillae with a dorsal boss, wide lateral lingual buttress, and elongate vertical suprapalatal pits; (2) posteriorly bifurcate parietals bounding cranial fenestrations anteriorly and medially; (3) triangular frontal with long broad-based internasal process, frontal anteroposterior length equal to maximum anteroposterior length of parietal, prefrontal facets extending posterior to mid-length of frontal, weakly developed mid-ventral crest, and ventrolateral crests that meet in ventral midline; (4) medium-length parietal postorbital processes sculptured in their proximal half; (5) separate prefrontal and lacrimal bones; (6) nasal excluded from narial margin; (7) trifurcate unpaired vomer; dentition showing size heterodonty anteriorly, resulting in sinuous occlusal surface; and (8) small body size.

However, instead of helping to resolve the phylogeny of albanerpetontid, Yaksha only brought more problematic. Indeed, phylogenetic analyses placed the new species as sister taxon of the clade comprised of the Japanese (and much older) Shirerpeton and the clade of Albanerpeton nexuosum and derived Cenozoic Albanerpeton. The main problematic of this configuration is that both Yaksha and Shirerpeton are nested within the genus Albanerpeton as currently defined, which is not allowed in systematics (one genus must only be comprised of species belonging to the same genus). However, these two genera are the only formally named representatives of Albanerpetontidae in Asia, and their diagnostic features distinguish them clearly from other Albanerpeton species. Therefore, this new species support the idea that the genus Albanerpeton require a revision and a subdivision, especially considering its temporal range over 100 Ma, and the authors support the option on restricting Albanerpeton only to the most derived species occurring in the Cenozoic.

Figure 3: Geographical distribution of the type specimens (or the main record in the case of the two forms not formally referred to a specific albanerpetontid) and a proposed dichotomous phylogeny. The red dots correspond to Albanerpeton sensu lato and the green dots to Albanerpeton sensu stricto (from Daza et al., 2020).

Last but not least, the new specimens bring more frustration when the authors try to implement it in different matrices to test the origin of the modern amphibians. Indeed, there is no strict consensus on how lissamphibian would have risen from more ancient groups (and from which group), and this question remains a highly debated topic in paleontology. Albanerpetontids, as considered closely related to lissamphibians, have been seen as a solution, but because of their fragmentary and scarce fossil record, they appear to be more source of the problem. Indeed, their relationship with other lissamphibian appears to be as variable as there are possibilities: as caudate or stem-caudate; as stem-batrachians; as the sister group of Gymnophionomorpha; or as stem-lissamphibians!

And Yaksha did not fall short on its notoriety although it helped to enhance the existing data and character coding. Four matrices were used, and they all produce different results: (1) as sister taxon to Batrachia (frogs and salamanders) within lepospondyls; (2) nested within Lissamphibia, as sister taxon of Eocaecilia (a fossil Gymnophionomorpha) and Caudata, Salentia being sister taxon of the whole clade; (3) as sister taxon of the most inclusive clade comprised of a more traditional topology, with Batrachia and Gymnophiona, and two fossil salamander taxa as stem-Lissamphibia; (4) nested in a clade comprising derived lepospondyls and lissamphibians.

Figure 4: A, Phylogenetic relationships of albanerpetontids with geographical distribution plotted against time; and B to E, Alternative positions recovered for Albanerpetontidae in relation to lissamphibians using different data matrices (modified from Daza et al., 2020).

 

Nevertheless, if phylogenetic analyses were not conclusive, this new species yield enough elements to help paleontologists to understand better the biology of this enigmatic group. As seen before, the entoglossal process of Yaksha has been found embedded in soft tissues, which have been described as remnants of the tongue pad. This peculiar characteristic is now known in chameleons, where hyoid element is attached to the base of the tongue, surrounded by collagenous sheaths and a circular accelerator muscle; and in plethodontid salamanders, in which as the tongue extends, the entire hyoid apparatus is folded into a bundle of cartilaginous rods that is projected out of the mouth again by circular protractor muscles. If the presence of the entoglossal process is first reported with Yaksha, it has been previously interpreted as a cultriform process of the parasphenoid in Celtedens megacephalus.

This new interpretation would suggest that albanerpetontids had a ballistic feeding strategy analogous to the one observed in chameleons or plethodontid salamanders. It would explain the complex and characteristic neck and jaw joints, as the curved ungual, the articulation of the hips, and the position of the orbit. Therefore, long-time thought as salamander-like amphibians, albanerpetontids would look like closer to small lizards living and waiting on trees and using their tongue to capture small invertebrates.

It is still unsure how albanerpetontid would have developed this strategy. Indeed, plethodontid salamanders are lungless, but use the hyoid apparatus for buccal pumping. Free of constrains from breathing, they develop their specialized tongue feeding strategy. However, albanerpetontids are known to be covered by scales, which would seem contradictory with a cutaneous respiration, although caecilians revealed some extent of such exchange. Maybe this constraint would explain the miniature size of albanerpetontids.

 

 

This new discovery enlightens the mysteries surrounding this enigmatic group of amphibians, but also proves more research needs to be done. Hopefully, more well-preserved specimens will be found soon!

 

More details on the original article:

Daza, J. D., E. L. Stanley, A. Bolet, A. M. Bauer, J. S. Arias, A. Čerňanský, J. J. Bevitt, P. Wagner, and S. E. Evans. 2020. Enigmatic amphibians in mid-Cretaceous amber were chameleon-like ballistic feeders. Science 370:687–691.

 

Identificação de dentes de dinossauros carnívoros

Um novo estudo analisou em detalhe os dentes dos dinossauros carnívoros e permite identificar dentes isolados, algo considerados muito difícil até agora. Este é o resultado da tese de doutoramento de Christophe Hendrickx na Universidade Nova de Lisboa.

Os dentes terópodes isolados são alguns dos fósseis de vertebrados mais comuns no registro fóssil do mesozóico e são continuamente relatados na literatura científica. Métodos quantitativos recentemente desenvolvidos melhoraram nossa capacidade de testar as afinidades de dentes isolados, mas na maioria dos estudos, os dentes são diagnosticados em caracteres qualitativos. Isso pode ser problemático porque a distribuição dos caracteres dentais dos terópodes ainda é pouco documentada e frequentemente restrita a uma linhagem. Para ajudar na identificação de dentes terópodes isolados e para avaliar com mais rigor seu potencial taxonómico e filogenético, Hendrickx et al. (2019) avaliaram as características dentárias de duas maneiras. Analisamos primeiro a distribuição de 34 caracteres dentários qualitativos em uma ampla amostra de taxa. Propriedades funcionais para cada característica dental foram incluídas para avaliar como a similaridade funcional gera homoplasias. Em seguida, compilaram uma matriz quantitativa de dados de 145 caracteres dentários para uma taxa de 97 saurísquios. Este último foi utilizado para avaliar o grau de homoplasia dos caracteres dentários qualitativos, abordar questões de sobre o valor taxonómico e bioestratigráfico dos dentes dos terópodes e explorar as principais tendências evolutivas na dentição dos terópodes.





Em conjuntos reduzidos de dados filogenéticos de Theropoda, os caracteres dentários exibem níveis mais altos de homoplasia do que os caracteres não dentários, mas ainda fornecem informações úteis de agrupamento e otimizam sinapomorfias locais de clados inferiores. Em conjuntos de dados filogenéticos mais amplos, o grau de homoplasia exibido por caracteres dentais e não dentários não é significativamente diferente. Características dentárias nas ornamentações das coroas, textura do esmalte e microestrutura dentária têm significativamente menos homoplasia do que outras características dentárias e podem ser usadas para identificar muitos taxas de terópodes no nível de 'família' ou 'subfamília', e algumas de género ou espécie. Essas características devem, portanto, ser uma prioridade para investigações que procuram classificar dentes isolados.

Estas observações melhoram a utilidade taxonômica dos dentes dos terópodes e, em alguns casos, podem ajudar a tornar os dentes isolados úteis como marcadores bioestratigráficos. Essa lista proposta de características dentárias em terópodes deve, portanto, facilitar futuros estudos sobre a paleontologia sistemática de dentes isolados.

Hendrickx, C., Mateus O., Araújo R., & Choiniere J. (2019).  The distribution of dental features in non-avian theropod dinosaurs: Taxonomic potential, degree of homoplasy, and major evolutionary trends. Palaeontologia Electronica. 22(3), 1-110.
https://palaeo-electronica.org/content/2019/2806-dental-features-in-theropods

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.

Anatomia ao Quadrado

Em anatomia, o quadrado é um osso craniano existente em todos os tetrápodes e que nos mamíferos deu origem ao estribo, um dos ossículos do ouvido. Curiosamente o osso quadrado não é de forma quadrada... antes pelo contrário! A geometria tridimensional complexa, a sua posição pivotal no crânio, a importância na classificação e sistemática, a função na audição e na mecânica mandibular dão importância a este osso para a compreensão da evolução. 

Christophe Hendrickx, da FCT Universidade Nova de Lisboa, empenhou-se para esclarecer uma série de aspectos evolutivos nos terópodes usando, dentes, ossos bucais e, precisamente. o osso quadrado. O primeiro desses estudos foi publicado na PeerJ e trata da terminologia padronizada, função e anatomia em dinossauros terópodes não-avianos.

Abstract
The quadrate of reptiles and most other tetrapods plays an important morphofunctional role by allowing the articulation of the mandible with the cranium. In Theropoda, the morphology of the quadrate is particularly complex and varies importantly among different clades of non-avian theropods, therefore conferring a strong taxonomic potential. Inconsistencies in the notation and terminology used in discussions of the theropod quadrate anatomy have been noticed, including at least one instance when no less than eight different terms were given to the same structure. A standardized list of terms and notations for each quadrate anatomical entity is proposed here, with the goal of facilitating future descriptions of this important cranial bone. In addition, an overview of the literature on quadrate function and pneumaticity in non-avian theropods is presented, along with a discussion of the inferences that could be made from this research. Specifically, the quadrate of the large majority of non-avian theropods is akinetic but the diagonally oriented intercondylar sulcus of the mandibular articulation allowed both rami of the mandible to move laterally when opening the mouth in many of theropods. Pneumaticity of the quadrate is also present in most averostran clades and the pneumatic chamber—invaded by the quadrate diverticulum of the mandibular arch pneumatic system—was connected to one or several pneumatic foramina on the medial, lateral, posterior, anterior or ventral sides of the quadrate.


Hendrickx C, Araújo R, Mateus O. (2015) The non-avian theropod quadrate I: standardized terminology with an overview of the anatomy and function. PeerJ3:e1245 https://dx.doi.org/10.7717/peerj.1245

Dentes de terópodes megalossauros

Foi publicado mais um artigo (em versão final), o terceiro neste verão de 2015, sobre dentes de dinossauros carnívoros como resultado do doutoramento de Christophe Hendrickx pela Universidade NOVA de Lisboa, desta vez sobre a dentição de dinossauros terópodes megalossauros.

É um estudo baseado em dezenas de dentes da Europa, África, América do Norte, América do Sul e Ásia. O estudo inclui dentes de Torvosaurus gurneyi do Jurássico Superoor de Portugal, em exposição no Museu da Lourinhã.

Resumo no original:
Theropod teeth are particularly abundant in the fossil record and frequently reported in the literature. Yet, the dentition of many theropods has not been described comprehensively, omitting details on the denticle shape, crown ornamentations and enamel texture. This paucity of information has been particularly striking in basal clades, thus making identification of isolated teeth difficult, and taxonomic assignments uncertain. We here provide a detailed description of the dentition of Megalosauridae, and a comparison to and distinction from superficially similar teeth of all major theropod clades. Megalosaurid dinosaurs are characterized by a mesial carina facing mesiolabially in mesial teeth, centrally positioned carinae on both mesial and lateral crowns, a mesial carina terminating above the cervix, and short to well-developed interdenticular sulci between distal denticles. A discriminant analysis performed on a dataset of numerical data collected on the teeth of 62 theropod taxa reveals that megalosaurid teeth are hardly distinguishable from other theropod clades with ziphodont dentition. This study highlights the importance of detailing anatomical descriptions and providing additional morphometric data on teeth with the purpose of helping to identify isolated theropod teeth in the future.

Hendrickx, C., Mateus, O., Araújo, R. 2015. The dentition of megalosaurid theropods. Acta Palaeontologica Polonica 60 (3): 627–642.  www  PDF

Este artigo já tinha sido divulgado pela APP mas sai agora em versão final.

Após o doutoramento na FCT-UNL, o Christophe está agora a fazer o pós-doutoramento na Universidade de Witwatersrand, em África do Sul.

Terminologia dentária de dinossauros terópodes

A maioria dos dinossauros carnívoros tinham dentes em forma de faca, serrilhados nas margens, com dentículos em larga medida semelhantes aos de uma faca de cozinha. Os dentes são dos elementos anatómicos mais comuns no registo fóssil porque: são fáceis de identificar, são a estrutura mais dura do corpo, eram numerosos (os répteis, peixes e anfíbios mudam de dentes continuamente ao longo da vida) e resistem facilmente à fossilização. Além disso, os dentes dão-nos pistas sobre a dieta dos animais.
Tudo isto faz com que o dentes sejam muito importantes para o estudo dos dinossauros carnívoros. Contudo, nem sempre a terminologia usada por cada autor e em cada artigo científico é consistente, e por vezes leva a alguma confusão. De forma a mitigar essa questão, Christophe Hendrickx (FCT-Univ. Nova de Lisboa) e colegas apresentam um novo estudo, publicado no Journal of Vertebrate Paleontology, propondo uma norma e padrão para a terminologia dentária em dinossauros carnívoros.

 

Hendrickx, C., Mateus O., & Araújo R. (2015).  A proposed terminology of theropod teeth (Dinosauria, Saurischia). Journal of Vertebrate Paleontology. e982797.  LINK PDF

Resumo original:
Theropod teeth are typically not described in detail, yet these abundant vertebrate fossils are not only frequently reported in the literature, but also preserve extensive anatomical information. Often in descriptions, important characters of the crown and ornamentations are omitted, and in many instances, authors do not include a description of theropod dentition at all. The paucity of information makes identification of isolated teeth difficult and taxonomic assignments uncertain. Therefore, we here propose a standardization of the anatomical and morphometric terms for tooth anatomical subunits, as well as a methodology to describe isolated teeth comprehensively. As a corollary, this study exposes the importance of detailed anatomical descriptions with the utilitarian purpose of clarifying taxonomy and identifying isolated theropod teeth.

Anatomia, Antropologia e Evolução Humana

"Anatomia, Antropologia e Evolução Humana" é o tema da palestra por Prof. Rui Diogo no dia 17 de Dezembro de 2014 na FCT- Universidade Nova de Lisboa enquadrado no Ciclo de Palestras "Geológicas às Quartas" do Departamento. de Ciências da Terra e com o apoio da FLAD, Fundação Luso Americana para o Desenvolvimento.
Apareça!

Data: 17 de Dezembro de 2014, Quarta-feira, pelas 14:30
Local: Biblioteca da Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, (GPS: 38,66267, -9,20553)

Link da palestra para site DCT

Rui Boliqueime Martins Diogo é Professor na Universidade de Howard, e diretor e patrono do Rui Diogo Lab. Rui Diogo é um excelente anatomista pelo que recebeu muitos prémios, entre eles recebeu este ano o Award for Best Anatomical Paper.
Tem numerosos artigos e livros publicados, sobretudo sobre anatomia, desde peixes a primatas. A anatomia que estuda tem implicações para a compreensão da nossa origem como primatas.

Livro:

• Morphological Evolution, Aptations, Homoplasies, Constraints and Evolutionary Trends: Catfishes as a case study on general phylogeny and macroevolution (p. 491). Enfield, New Hampshire: Science Publishers. 2005.
• Comparative Anatomy and Phylogeny of Primate Muscles and Human Evolution
• Muscles of Vertebrates

Exemplos de artigos:
Diogo, R., Abdala, V., Lonergan, N., & Wood, B. A. (2008). From fish to modern humans–comparative anatomy, homologies and evolution of the head and neck musculature. Journal of anatomy, 213(4), 391-424.

Diogo, R. (2007). The origin of higher clades: osteology, myology, phylogeny and evolution of bony fishes and the rise of tetrapods. Science Pub Incorporated.

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Os dentes dos dinossauros carnívoros megalossauros

• 
  
• Os dentes de dinossauros carnívoros são frequentes no registo fóssil pois eram continuamente substituídos e cada animal poderia produzir dezenas de dentes ao longo da sua vida. Mas a sua forma é aparentemente semelhante ao longo de toda a linhagem pelo que tem sido difícil identificar dentes isolados. Para resolver esse desafio, o estudante de doutoramento Christophe Hendrickx está a estudar dentes de dinossauros terópodes como trabalho de dissertação na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa sob a orientação de Octávio Mateus. Um dos trabalhos é agora publicado na Acta Palaeontologica Polonica, onde os dentes dos dinossauros carnívoros megalossauros são esmiuçados. 
• 
  
  

  

  Anatomia de um dente de dinossauro terópode (Hendrickx et al., 2014)

Hendrickx, C., Mateus O. & Araújo R. (2014). The dentition of megalosaurid theropods. Acta Palaeontologica Polonica. in press,

Dente de dinossauro terópode e dentículos (Hendrickx et al., 2014)

Resumo:

Dentes de terópodes são particularmente abundantes no registro fóssil e frequentemente mencionados na literatura. No entanto, a dentição de muitos terópodes não foi descrita de forma abrangente, sendo frequentemente omitindos os detalhes sobre a forma dos dentículos, ornamentação da coroa e textura do esmalte, etc. Esta escassez de informações tem sido particularmente notável em clados basais dos dinossauros terópodes, tornando a identificação dos dentes isolados difícil, e as atribuições taxonómicas incertas. Aqui fornecemos uma descrição detalhada da dentição dos Megalosauridae e uma comparação de dentes superficialmente semelhantes de todos os principais clados de terópodes .
Os dentes de dinossauros megalossaurídeos são caracterizados por uma carina mesial projectada mesiolabialmente em dentes mais mesiais nos dentes laterais, carina mesial terminando acima do cervix, e sulcos interdenticular curtos a bem desenvolvidos entre dentículos distais. A análise discriminada realizada numa base de dados numéricos de dentes de 62 taxa de terópode revela que os dentes de megalosaurídeos são dificilmente distinguíveis de outros clados de terópodes com dentição zifodonte. Este estudo destaca a importância de detalhar descrições anatómicas e fornecendo dados morfométricos adicionais sobre os dentes, com a finalidade de ajudar a identificar os dentes terópodes isolados.

Abstract:

Theropod teeth are particularly abundant in the fossil record and frequently reported in the literature. Yet, the dentition of many theropods has not been described comprehensively, omitting details on the denticle shape, crown ornamentation and enamel texture. This paucity of information has been particularly striking in basal clades, thus making identification of isolated teeth difficult, and taxonomic assignments uncertain. We here provide a detailed description of the dentition of Megalosauridae, and a comparison to and distinction from superficially similar teeth of all major theropod clades.

Megalosaurid dinosaurs are characterized by a mesial carina facing mesiolabially in most mesial teeth, centrally positioned carinae on both most mesial and lateral crowns, a mesial carina terminating above the cervix, and short to well-developed interdenticular sulci between distal denticles. A discriminant analysis performed on a dataset of numerical data collected on the teeth of 62 theropod taxa reveals that megalosaurid teeth are hardly distinguishable from other theropod clades with ziphodont dentition. This study highlights the importance of detailing anatomical descriptions and providing additional morphometric data on teeth with the purpose of helping to identify isolated theropod teeth in the future.

Related External Link

DOI:

http://dx.doi.org/10.4202/app.00056.2013

Supplementary online material:

http://www.app.pan.pl/archive/published/SOM/appXX-Hendrickx_etal_SOM.pdf

All the figures and data, including the files for PAST:

https://drive.google.com/folderview?id=0B_-0b-kZatHidzRlTDRGdmFfbGc&usp=sharing

LINK PDF

Anatomia do peixe-lua Mola mola

Muitas vezes os paleontólogos têm de olhar para espécies recentes para compreender a anatomia das espécies fossilizadas. Por isso, hoje estive a dissecar um peixe-lua, Mola mola, pescado ontem (3.6.2013) na nossa costa.

Peixe-lua, Mola mola, anatomia interna. Foto por Octávio Mateus.

Agradecimentos ao João Pedro Correia, que forneceu o espécime, e ao Marco Marzola e Vasco Ribeiro que ajudaram na dissecação.

Saurópodes podiam ter interclavícula, um osso previamente desconhecido em dinossauros

Novo estudo levanta a possibilidade de os saurópodes terem interclavícula, um osso previamente desconhecido em dinossauros.
O estudo por uma equipa de paleontologia da Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa focou-se nos dinossauros diplodocídeos, em particular no recentemente descrito Kaatedocus., e sugere que a origem da fúrcula ("wish-bone") pode ser uma interclavícula em vez de duas clavículas fundidas.

Referência
Tschopp, E., & Mateus O. (2013).  Clavicles, interclavicles, gastralia, and sternal ribs in sauropod dinosaurs: new reports from Diplodocidae and their morphological, functional and evolutionary implications. Journal of Anatomy. 222,321-340.
LINK

Abstract
Ossified gastralia, clavicles and sternal ribs are known in a variety of reptilians, including dinosaurs. In sauropods, however, the identity of these bones is controversial. The peculiar shapes of these bones complicate their identification, which led to various differing interpretations in the past. Here we describe different elements from the chest region of diplodocids, found near Shell, Wyoming, USA. Five morphotypes are easily distinguishable: (A) elongated, relatively stout, curved elements with a spatulate and a bifurcate end resemble much the previously reported sauropod clavicles, but might actually represent interclavicles; (B) short, L-shaped elements, mostly preserved as a symmetrical pair, probably are the real clavicles, as indicated by new findings in diplodocids; (C) slender, rod-like bones with rugose ends are highly similar to elements identified as sauropod sternal ribs; (D) curved bones with wide, probably medial ends constitute the fourth morphotype, herein interpreted as gastralia; and (E) irregularly shaped elements, often with extended rugosities, are included into the fifth morphotype, tentatively identified as sternal ribs and/or intercostal elements. To our knowledge, the bones previously interpreted as sauropod clavicles were always found as single bones, which sheds doubt on the validity of their identification. Various lines of evidence presented herein suggest they might actually be interclavicles – which are single elements. This would be the first definitive evidence of interclavicles in dinosauromorphs. Previously supposed interclavicles in the early sauropodomorph Massospondylus or the theropods Oviraptor and Velociraptor were later reinterpreted as clavicles or furculae. 

Região do peito de dinossauro saurópode, com presença de clavículas e interclavícula .

Independent from their identification, the existence of the reported bones has both phylogenetic and functional significance. Their presence in non-neosauropod Eusauropoda and Flagellicaudata and probable absence in rebbachisaurs and Titanosauriformes shows a clear character polarity. This implicates that the ossification of these bones can be considered plesiomorphic for Sauropoda. The proposed presence of interclavicles in sauropods may give further support to a recent study, which finds a homology of the avian furcula with the interclavicle to be equally parsimonious to the traditional theory that furcula were formed by the fusion of the clavicles. Functional implications are the stabilizing of the chest region, which coincides with the development of elongated cervical and caudal vertebral columns or the use of the tail as defensive weapon. The loss of ossified chest bones coincides with more widely spaced limbs, and the evolution of a wide-gauge locomotor style.

Um osso quadrado... uma problemática bicuda!

É um osso curioso, o quadrado! Apesar do nome... não é quadrado! Nos répteis é o osso do crânio que faz a articulação com a mandíbula e por isso tem uma série de funcionalidades motoras às quais acumula funções na audição. Nos mamíferos, o quadrado transformou-se num dos ossículos de ouvido.

O estudante de doutoramento Christophe Hendrickx está a estudar a evolução do aparelho bocal do dinossauros carnívoros e dedicou muito tempo a observar o osso quadrado.
Divulga-se aqui dois resumos apresentados em congressos internacionais:

Referências
Hendrickx, C., Araújo, R. & Mateus O. (2012). The nonavian theropod quadrate: systematics usefulness, major trends and phylogenetic morphometrics analysis. : Journal of Vertebrate Paleontology, Program and Abstracts, 2012, p.110. ISSN 1937-2809 PDF

Hendrickx, C., & Mateus O. (2012). Ontogenetical changes in the quadrate of basal tetanurans.. 10 th Annual Meeting of the European Association of Vertebrate Paleontologist ¡Fundamental! . 20, 101-104. PDF


Abstract:
The quadrate in nonavian theropods is incredibly diverse morphologically; however this morphological disparity has been underestimated for taxonomic purposes. The quadrate topological homologies and anatomy, as well as the terminology, among nonavian theropod clades are reviewed. In order to evaluate the phylogenetic potential and investigate the evolutionary transformations of the quadrate, we conducted a Catalano-Goloboff phylogenetic morphometric analysis using 3 morphometric characters, a total
of 28 landmarks coded for 23 taxa, as well as a cladistic analysis using 115 discrete quadrate-related characters coded for 43 taxa. The cladistic analysis provides a fully resolved tree mirroring the current classification of nonavian theropods. The quadrate morphology by its own provides a wealth of data with strong phylogenetic signal. Several unambiguous synapomorphies support nonavian theropod relationships and the resulting consensus tree allows inference of major trends in the evolution of this bone. Important
synapomorphies include: for Abelisauridae, a lateral ramus extending to the ectocondyle; for Tetanurae, the absence of the lateral process; for Spinosauridae, a medial curvature of the ventral part of the pterygoid ramus occurring just above the mandibular articulation; for Neotetanurae, an anterior margin of the pterygoid flange formed by a roughly parabolic margin; and for Tyrannosauroidea, a semi-oval pterygoid flange shape in medial view. The Catalano-Goloboff phylogenetic morphometric analysis reveals two main morphotypes of the mandibular articulation of the quadrate linked to function. The first morphotype, characterized by an anteroposteriorly broad mandibular articulation with two ovoid/ subcircular condyles roughly subequal in size, is found in Ceratosauria, Tyrannosauroidea and Oviraptorosauria. This morphotype allows a very weak displacement of the mandible laterally. The second morphotype is characterized by an elongate and anteroposteriorly narrow mandibular articulation and a long and parabolic/sigmoid ectocondyle. Present in Megalosauroidea, Carcharodontosauridae and Dromaeosauridae, this morphotype permits the lower jaw rami to be displaced laterally when the mouth opened.

Lourinhanosaurus antunesi é um dos novos dinossauros da Procon Collecta 2011

A Collecta lançou a nova colecção de bonecos comercializados a nível mundial. O dinossauro terópode Lourinhanosaurus antunesi, exposto no Museu da Lourinhã, é uma das novidades. Este ano também é o lançamento do Miragaia longicollum, pela Carnegie Collection, baseado num esqueleto também em exposição no museu lourinhanense.

Lourinhanosaurus
© Procon CollectA

Sistema nervoso - Plexus brachialis e nervos principais dos membros posteriores