[N] 2006 Angolan sauropod puts Sereno’s landbridge hypothesis in doubt.
Jacobs, et al (2006) The Occurrence And Geological Setting Of Cretaceous Dinosaurs.. from Angola
During an Angolian expedition in 2005 an articulated forelimb of a sauropod dinosaur was discovered elements at Iembe near type locality of Angolasaurus in near shore marine sediments, the association of the bones and the terrigenous input into the strata indicates proximity to the paleoshoreline. Moreover, this specimen, found in sediments at or near the end of the Turonian, is probably the most precisely dated Cretaceous dinosaur in sub-Saharan Africa. The morphology of the ulna suggests that the forelimb does not belong to a titanosaurian (Mateus et al., submitted). The discovery opens the door to a new fossil field for African Cretaceous terrestrial biota.
The sauropod specimen from Iembe is interesting as far as it goes, but the authors predict that the sample of dinosaurs and other terrestrial vertebrates will improve as field work continues. For now, it is reasonable to conclude that the Iembe sauropod represents a taxon descended from sauropods in Africa at the completion of the South Atlantic Ocean and the isolation of Africa.
Thus, from a biogeographic perspective, the development of the South Atlantic has significance for dinosaurs equal to that which it has for mosasaurs, in the first case leading to restriction of faunal dispersal, in the second to a new dispersal route for marine organisms. Sereno et al. (2004) suggested that trans-Atlantic interchange, and hence a dry land passage between South America and Africa, may have existed as late as 95 Ma, based on their reckoning of the age of the abelisaurid dinosaur Rugops from the Echkar Formation, Niger.
Although they state the age as Cenomanian and give an absolute age estimate of “ca. 95 Myr ago” for the specimen (Sereno et al., 2004:2), no evidence for the age is provided. Taquet (1976), on which the dating of fossil localities in Niger appears to rely, places the Echkar Formation in the Albian.
By the Late Cenomanian, marine transgression had put an end to the deposition of the Continentale Intercalaire, of which the Echar Formation is a part. Until chronological data are brought forth to justify a Cenomanian age for Rugops, its significance for indicating trans-Atlantic interchange at 95 Ma should be questioned because that age estimate stands contrary to indications that the Atlantic was complete by Albian time (which ended at 99.6 Ma), and Niger was inundated by marine waters by Late Cenomanian time, or about at the target age of 95 Ma.