Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative ...brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relationship across species and that any deviation from this slope is due to selection on brain size. Using the largest fossil and extant dataset yet assembled, we find that shifts in allometric slope underpin major transitions in mammalian evolution and are often primarily characterized by marked changes in body size. Our results reveal that the largest-brained mammals achieved large relative brain sizes by highly divergent paths. These findings prompt a reevaluation of the traditional paradigm of relative brain size and open new opportunities to improve our understanding of the genetic and developmental mechanisms that influence brain size.
The Glen Murray fossil penguin was one of the first ancient penguins to be reported from the North Island of New Zealand when it was described in 1973. However, its significance for penguin diversity ...has remained largely unresolved since initial description. Here we show that the Glen Murray penguin exhibits two of three traits that are autapomorphic for Kairuku: the femur is very stout with a midshaft width <15% of the total femoral length and the tibiotarsus has a distinctly convex medial border in distal view. The third trait (absence of the crista medialis hypotarsi) cannot be assessed as the proximal end of the tarsometatarsus is missing. The Glen Murray penguin is most likely a distinct species that should be assigned to the genus Kairuku, although we refer it to Kairuku sp. pending the discovery of more material. Reappraisal of local stratigraphy indicates that the Glen Murray fossil penguin is from the Dunphail Siltstone member of the Glen Massey Formation and can be assigned to the lower Whaingaroan stage (34.6-29.8 Ma).
The first specimen of the new sauropod Erketu ellisoni, from the Lower Cretaceous of the eastern Gobi of Dornogov, Mongolia, is described here. The specimen comprises a well-preserved articulated ...anterior cervical series, an articulated lower hindlimb, and a sternal plate. This sauropod displays a unique combination of features including low, bifid neural spines, elongate cervical centra, and crescent-shaped sternal plates. Computed tomography imaging reveals the vertebrae were extensively invaded with pneumatic camellae. The holotype individual of Erketu was of modest mass relative to other neosauropods, but had an extremely elongate neck. Phylogenetic analysis indicates Erketu is a member of the Somphospondyli and may belong to a more exclusive clade therein.
A Phylogenomic Supertree of Birds Kimball, Rebecca T.; Oliveros, Carl H.; Wang, Ning ...
Diversity,
07/2019, Volume:
11, Issue:
7
Journal Article
Peer reviewed
Open access
It has long been appreciated that analyses of genomic data (e.g., whole genome sequencing or sequence capture) have the potential to reveal the tree of life, but it remains challenging to move from ...sequence data to a clear understanding of evolutionary history, in part due to the computational challenges of phylogenetic estimation using genome-scale data. Supertree methods solve that challenge because they facilitate a divide-and-conquer approach for large-scale phylogeny inference by integrating smaller subtrees in a computationally efficient manner. Here, we combined information from sequence capture and whole-genome phylogenies using supertree methods. However, the available phylogenomic trees had limited overlap so we used taxon-rich (but not phylogenomic) megaphylogenies to weave them together. This allowed us to construct a phylogenomic supertree, with support values, that included 707 bird species (~7% of avian species diversity). We estimated branch lengths using mitochondrial sequence data and we used these branch lengths to estimate divergence times. Our time-calibrated supertree supports radiation of all three major avian clades (Palaeognathae, Galloanseres, and Neoaves) near the Cretaceous-Paleogene (K-Pg) boundary. The approach we used will permit the continued addition of taxa to this supertree as new phylogenomic data are published, and it could be applied to other taxa as well.
Penguin feathers are highly modified in form and function, but there have been no fossils to inform their evolution. A giant penguin with feathers was recovered from the late Eocene (approximately 36 ...million years ago) of Peru. The fossil reveals that key feathering features, including undifferentiated primary wing feathers and broad body contour feather shafts, evolved early in the penguin lineage. Analyses of fossilized color-imparting melanosomes reveal that their dimensions were similar to those of non-penguin avian taxa and that the feathering may have been predominantly gray and reddish-brown. In contrast, the dark black-brown color of extant penguin feathers is generated by large, ellipsoidal melanosomes previously unknown for birds. The nanostructure of penguin feathers was thus modified after earlier macrostructural modifications of feather shape linked to aquatic flight.
Paraptenodytes antarcticus is one of the best-known and most complete fossil penguins. This taxon is so distinctive that it has traditionally been classified in its own subfamily (Sphenisciformes: ...Paraptenodytinae) separate from all living penguins (Spheniscinae). The well-preserved partial skull of P. antarcticus is one of our richest sources of data on early penguin cranial morphology. We provide an updated description of the skull of P. antarcticus in a comparative context and use this information to explore the phylogenetic relationships of this taxon. Three cladistic analyses using an osteology dataset, a larger morphological dataset (including osteological, soft tissue, behavior, and oological characters) and a combined (morphological + molecular) dataset all recover Paraptenodytes as the sister taxon to a clade including all extant penguins. The placement of Paraptenodytes outside the crown clade of extant penguins reveals the order in which many spheniscid synapomorphies were acquired and lends support to the hypothesis that modern penguins had Subantarctic ancestors.
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