Shukang Zhang, Tzu-Ruei Yang, Zhengqi Li, and Yongguo Hu (2018)
New dinosaur egg material from Yunxian, Hubei Province, China resolves the classification of dendroolithid eggs.
Acta Palaeontologica Polonica (in press)
The oofamily Dendroolithidae is a distinct group of dinosaur eggs reported from China and Mongolia, which isÂ characterized by branched eggshell units and irregular pore canals. The ootaxonomic inferences, however, were rarely discussed until now. A colonial nesting site was recently uncovered from the Qinglongshan region, Yunxian, Hubei Province, China. More than 30 dendroolithid egg clutches outcrop on the Tumiaoling Hill, including an extremely gigantic clutch containing 77 eggs. All clutches were exposed in the Upper Cretaceous fluvial-deposited Gaogou For mation. In this study, we emend the diagnosis of the oogenus Placoolithus and assign all dendroolithid eggs from the Tumiaoling Hill to a newly emended oospecies Placoolithus tumiaolingensis that shows greatly variable eggshell microstructure. Moreover, our study also disentangles the previous vexing classification of dendroolithid eggs. We conclude that Dendroolithus tumiaolingensis, D. hongzhaiziensis, and Paradendroolithus qinglongshanensis, all of which were previously reported from Yunxian, should be assigned to the newly emended oospecies Placoolithus tumiaolingensis.
Jane P. Davidson and Michael J. Everhart (2018)
The Mystery of Elasmosaurus platyurus Cope 1868 -- Where is the Rest of the Type Specimen?
Transactions of the Kansas Academy of Science 121(3-4):335-345
As originally described by Cope (1868), the type specimen of Elasmosaurus platyurus from western Kansas included more than 100 vertebrae, portions of the skull, and the reasonably complete pectoral and pelvic girdles of what was then the largest known plesiosaur. Within four years of its discovery, however, both of the limb girdles had disappeared with no official explanation. Here we document the events leading up to the loss of important portions of this unique specimen.
Peter D. Roopnarine, K.D. Angielczyk, A.Weik & A.Dineen (2018)
Ecological persistence, incumbency and reorganization in the Karoo Basin during the Permian-Triassic transition.
Earth-Science Reviews (advance online publication)
The geological persistence of biotic assemblages and their reorganization or destruction by mass extinctions are key features of long-term macroevolutionary and macroecological patterns in the fossil record. These events affected biotic history disproportionately and left permanent imprints on global biodiversity. Here we hypothesize that the geological persistence and incumbency of paleocommunities and taxa are maintained by patterns of biotic interactions that favour the ecological persistence and stable coexistence of interacting species. Equally complex communities produced by alternative macroevolutionary histories, and hence of different functional structure, may support less stable species coexistence, and are therefore less persistent. However, alternative communities with the same functional structure as a persistent paleocommunity, but variable clade richnesses, tend to be as or more stable than observed palecommunities, thus demonstrating that geological persistence is not the result of constrained patterns, or ecological locking. Numerically modeled food webs for seven tetrapod-dominated paleocommunities spanning the traditionally-recognized Permian-Triassic boundary in the Karoo Basin of South Africa, show that incumbency before the Permian-Triassic mass extinction was maintained by a dynamically stable, community-level system of biotic interactions, thereby supporting the hypothesis. The system's structure was lost through successive extinction pulses, and replaced initially by a rich but geologically ephemeral Early Triassic fauna, which itself was replaced by a novel Middle Triassic community with renewed incumbency. The loss of persistence and incumbency, therefore, did not result simply from the extinction of species; instead the largest declines were accompanied by the addition of new species to the system in the earliest aftermath of the event. We therefore further hypothesize that ecological reorganization and evolutionary innovation in the wake of mass extinctions play key roles in the destruction of highly stable, preexisting systems of biotic interaction. In the case of the Karoo Basin paleocommunities, we estimate that a return to stable interactions, and thus incumbency, was achieved in approximately 4--17âMa.
Gabrielle Pavlovic, Michael A. Weston & Matthew R. E. Symonds (2018)
Morphology and geography predict the use of heat conservation behaviours across birds.
Functional Ecology (advance online publication)
1. Heat conservation behaviours in birds in part involve postural adjustments to regulate the area of exposed body surfaces. However, the occurrence of these behaviours across birds, and the factors that explain their use across bird species, remain poorly known.
2. We examined the occurrence of three distinctive bird behaviours â back rest (where the bill is tucked into the plumage), standing on one leg, and sitting â across 852 bird species using a Bayesian phylogenetic comparative analytical approach, examining the phylogenetic signal in, and ecological correlates of, these behaviours.
3. All three behaviours were far from ubiquitous across species: only a third to a half of species in our analysis have been confirmed to use each behaviour. The behaviours all exhibited significant phylogenetic signal indicating differential usage across clades.
4. All three behaviours were more commonly reported in bird species studied at higher latitudes. Back rest was also more often observed in species that have longer bills, relative to their body size, while standing on one leg was associated with longer relative tarsus length. Sitting behaviour was more common in heavier birds.
5. The results suggest the use of these postures is related to environment (climate) and morphology (appendage length), and therefore most likely is associated with the need to mitigate heat loss across the exposed body surfaces. However other potential functions of these postures, such as alleviating biomechanical load associated with large appendages and bodies, or the need to minimise energetic expenditure, are possible.
Oksana V. Shatkovska, Maria Ghazali, Ivan S. Mytiai & Natalia Druz (2018)
Size and shape correlation of birds' pelvis and egg: Impact of developmental mode, habitat, and phylogeny.
Journal of Morphology (advance online publication)
While eggs shapes and sizes have been subject of many studies, we still know little about factors affecting these characteristics of birds' eggs. We revealed that shapes of pelvis and egg correlated less than their respective sizes. Egg measurements (length or diameter) scaled with negative allometry against pelvis size, that is, eggs become relatively larger with decreasing pelvis size. Studied birds with altricial developmental mode had on average the smallest pelvic dimensions and the largest relative size of eggs. However, this is due to the effect of small pelvis size (and body as a whole) of most altricials. At the similar size of the pelvis, birds with altricial developmental mode had a smaller relative size of eggs than their precocial counterparts. Correlation between the shape of egg and pelvis is affected by habitat. Narrow pelvis with an elongated postacetabular region correlated with elongated eggs in diving waterfowl. In raptorial birds, the relatively wide pelvis with the shortened postacetabular region correlated with the nearly rounded shape of eggs.