Evolução 250: Mesolambdolophus, novo perissodátilo

(em breve)
Journal of Vertebrate Paleontology
Volume 31, Issue 4, 2011

ABSTRACT

An unusual specimen of a perissodactyl from the Bridgerian (late early to early middle Eocene) of Wyoming provides the basis for a new genus and species, Mesolambdolophus setoni. The specimen (MCZ 19585) displays an unusual combination of features: first lower premolar absent; p2 and p3 not molariform; p4 submolariform; anterior end of metalophid lingually placed, contacting metaconid; metaconid not twinned; and large hypoconulid on m3. The orientation of the metalophid excludes this specimen from Ceratomorpha, and the size and characters of this specimen exclude it from any known genus of Bridgerian perissodactyl, as well as from any other Eocene perissodactyl taxon. Including this taxon in a phylogenetic analysis of basal perissodactyls places Mesolambdolophus as sister taxon to Tapiromorpha, but we consider any assessment of the position of Mesolambdolophus tentative at best, given the limitations of analyses of basal perissodactyls currently available. The presence of a small Bridgerian ‘hippomorph’ form that is larger than Orohippus reduces the reliability of assigning isolated postcrania to Bridgerian perissodactyl taxa on the basis of size.

Evolução 249: Acristavus gagslarsoni, novo hadrossáurio sem crista

(em breve)

 

Resumo:

A new hadrosaurid dinosaur, Acristavus gagslarsoni, is here named on the basis of several autapomorphic characteristics of the frontal, postorbital, and dentary. Acristavus is a member of the newly erected clade Brachylophosaurini, which along with its other members, Brachylophosaurus and Maiasaura, constitutes the earliest hadrosaurine hadrosaurid clade. The new taxon occurred approximately 79 million years ago and has been recovered from the Two Medicine Formation of western Montana and nearly simultaneously in the Wahweap Formation of southern Utah. Corresponding with its age and relationship to the other members of the Brachylophosaurini, it is not surprising that Acristavus possesses traits seen in both Brachylophosaurus and Maiasaura, but not necessarily shared between them. One of the most interesting morphological features of Acristavus is the lack of cranial osteological ornamentation, which is in stark contrast to every other hadrosaurid dinosaur except Edmontosaurus. Combining stratigraphic and phylogenetic data from Acristavus yields support for the hypothesis that the hadrosaurid ancestor did not possess cranial ornamentation, and that the subfamilies Hadrosaurinae and Lambeosaurinae each independently developed display structures.

Genealogia 591: Geopatronyme

http://www.geopatronyme.com/index.htm

Geopatronyme é um site onde é possível buscar a distribuição geográfica de sobrenomes na França.

Evolução 248: Diodorus scytobrachion

Diodorus scytobrachion é a nova espécie de dinossauriforme descoberta no Triássico (Carniano-Noriano) do Marrocos, no Membro Irohalene da Formação Timezgadiouine. Os dinossauriformes (Dinosauriformes) constituíam um grupo de répteis primitivos anteriores aos dinossauros, dos quais podem ser os ancestrais ou parentes muito próximos destes. A nova espécie é considerada pelos seus descobridores como parente próxima do Sacisaurus, gênero brasileiro que viveu no Rio Grande do Sul, ambos classificados na família dos silessaurídeos (Silesauridae), de dieta supostamente herbívora.