Myers, T. S., Tabor N. J., Jacobs L. L., & Mateus O.
(2012).
Palaeoclimate of the Late Jurassic of Portugal: Comparison with the Western United States.
Sedimentology. 59(6), 1695–1717., 2012//01/
AbstractInvestigation of the palaeoclimatic conditions associated with Upper Jurassic strata in Portugal and comparison with published palaeoclimate reconstructions of the Upper Jurassic Morrison Formation in western North America provide important insights into the conditions that allowed two of the richest terrestrial faunas of this period to flourish. Geochemical analyses and observations of palaeosol morphology in the informally named Upper Jurassic Lourinhã formation of western Portugal indicate warm and wet palaeoclimatic conditions with strongly seasonal precipitation patterns. Palaeosol profiles are dominated by carbonate accumulations and abundant shrink-swell (vertic) features that are both indicative of seasonal variation in moisture availability. The δ18OSMOW and δDSMOW values of phyllosilicates sampled from palaeosol profiles range from +22·4‰ to +22·7‰ and −53·0‰ to −37·3‰, respectively. These isotope values correspond to temperatures of formation between 32°C and 39°C ± 3°, with an average of 36°C, which suggest surface temperatures between 27°C and 34°C (average 31°C). On average, these surface temperature estimates are 1°C higher than the highest summer temperatures modelled for Late Jurassic Iberia using general circulation models. Elemental analysis of matrix material from palaeosol B-horizons provides proxy (chemical index of alteration minus potassium) estimates of mean annual precipitation ranging from 766 to 1394 mm/year, with an average of approximately 1100 mm/year. Palaeoclimatic conditions during deposition of the Lourinhã formation are broadly similar to those inferred for the Morrison Formation, except somewhat wetter. Seasonal variation in moisture availability does not seem to have negatively impacted the ability of these environments to support rich and relatively abundant faunas. The similar climate between these two Late Jurassic terrestrial ecosystems is probably one of the factors which explains the similarity of their vertebrate faunas.
Myers, T. S., Mateus O., Polcyn M. J., Vineyard D., & Jacobs L. L.
(2016).
A new chelonioid turtle from the Paleocene of Cabinda, Angola.
Annual Meeting of the Society of Vertebrate Paleontology. 194.: Journal of Vertebrate Paleontology, Program and Abstracts, 2016
AbstractWe report a new chelonioid turtle on the basis of a nearly complete skull collected in lower Paleocene, shallow marine deposits, equivalent to the offshore Landana Formation, near the town of Landana in Cabinda Province, Angola. Chelonioid material previously reported from this locality is likely referable to this new taxon. The well-preserved skull is missing the left quadrate, squamosal, and prootic, both opisthotics, and the mandible. The skull possesses a rod-like basisphenoid rostrum, which is a synapomorphy of Chelonioidea, but it differs from other chelonioid skulls in that the contact between the parietal and squamosal is absent, and the posterior palatine foramen is present. Phylogenetic analysis recovers the new taxon as a basal chelonioid. The Paleocene– Eocene strata near Landana have produced a wealth of turtle fossils, including the holotype of the pleurodire Taphrosphys congolensis. A turtle humerus collected from the Landana locality differs morphologically from the humeri of chelonioids and Taphrosphys, indicating the presence of a third taxon. Chelonioid fossil material in the Landana assemblage is rare compared to the abundant fragmentary remains of Taphrosphys that are found throughout the stratigraphic section. This disparity in abundance suggests the new chelonioid taxon preferred open marine habitats, whereas Taphrosphys frequented nearshore environments.
Muchagata, J., & Mateus O.
(2016).
Sexual display and rostral variation in extinct beaked whale, Globicetus hiberus.
XIV EAVP Meeting. 136., Haarlem, The Netherlands: XIV EAVP Meeting, Programme and Abstract Book
AbstractIberian extinct ziphiid, Globicetus hiberus, bears a peculiar large bony sphere in the rostrum, the Mesorostral Process of the Premaxillae or MPP. The MPP varies in size and shape of growth in the six specimens studied and seems to have an allometrically growth in one subgroup, but not in the other, suggesting subgroups correspond to males and females (sexual dimorphism). Even more, some rostral structures, such as the medial pad of the premaxillae seem to be associated with the specimens with lower and leaner MPP’s and ossification of the mesorostral canal by the vomer can also be of value in differentiating sex. Beaked whales are deep-diving, echolocation-user odontocetes and able to perceive bones as distinctive echoic images with their sonar; therefore the MPP may work as a secondary sexual organ (“antlers inside” hypothesis by Gol´din, 2014), a mute display structure acting as an “acoustic flag” to be perceived through echolocation by other individuals, giving information about the shape and size of the MPP.