Katja Waskowa & Octavio Mateus (2017)
Dorsal rib histology of dinosaurs and a crocodylomorph from western Portugal: Skeletochronological implications on age determination and life history traits.
Comptes Rendus Palevol 16(4): 425-439
Bone histology is an important tool for uncovering life history traits of extinct animals, particularly those that lack modern analogs, such as the non-avian dinosaurs. In most studies, histological analyses preferentially focus on long bones for understanding growth rates and determining age. Here we show, by analyzing ornithischians (a stegosaur and an ornithopod), saurischians (a sauropod and a theropod), and a crocodile, rib histology is a suitable alternative. The estimated age for all sampled taxa ranges between 14 to 17 years for Lourinhanosaurus antunesi and 27 to 31 years estimated for Draconyx loureiroi. The theropod Baryonyx was skeletally mature around 23–25 years of age but showed unfused neurocentral sutures, a paedomorphic feature possibly related to aquatic locomotion. Our results show that ribs can contain a nearly complete growth record, and reveal important information about individual age, point of sexual maturity, and, in some cases, sex. Because ribs are more available than long bones, this method opens new possibilities for studying rare and incomplete fossils, including holotypes.
Jason P. Jung and Stuart S. Sumida (2017)
A juvenile of the multiple-tooth-rowed reptile Labidosaurikos (Eureptilia, Captorhinidae, Moradisaurinae) from the Lower Permian of north-central Texas.
Harvard University Museum of Comparative Zoology (MCZ) 1352 is a partial maxillary toothplate of a basal reptilian from the Lower Permian of Baylor County, north-central Texas. The specimen displays the straight rows of teeth characteristic of the subfamily Moradisaurinae (family: Captorhinidae) and is nearly identical in shape to the maxilla of Labidosaurikos meachami. Larger, more mesial individual teeth conform to the dental pattern previously determined for adults of the genus. Adults of L. meachami are known to possess six maxillary tooth rows, whereas MCZ 1352 has only five. Although only a partial specimen, it appears MCZ 1352 is most likely a juvenile specimen of L. meachmi. If correct, the comparative sizes suggest isometric growth of this element. The orientation of the lingual-most row of teeth, and the five as opposed to six maxillary tooth rows, suggest either new tooth rows may move labially during development or bone growth and remodeling occur lingually, resulting in the development of a margin of maxillary bone between the fifth row and the lingual edge.
Oladapo Akinlotan (2017)
Mineralogy and Palaeoenvironments: The Weald Basin (Early Cretaceous), Southeast England.
Depositional Record (advance online MS)
Determination of the mineralogy of sedimentary rocks is important in palaeoenvironmental interpretations, especially when outcrop and field data are insufficient or not accessible. The Lower Cretaceous Wealden facies, presented here as a case study, is one such example. Petrographic analysis of this suite of sediments reveals that the arenaceous facies are mainly quartz arenites, quartzose siltstones and lack significant feldspar. The clay minerals are illite, kaolinite, illite-montmorillonite, vermiculite and illite-smectite. The presence of quartz arenites and kaolinite suggest that the rocks were reworked from granitic and/or gneissic rocks. Directly or indirectly, the rocks may have been obtained from a stable craton. The mineral and textural maturity, together with a travel distance of ~300 km point to matured sources. A warm and humid palaeoclimate in the source areas resulted in extensive weathering.