Cranial shape and correlated characters in crocodilian evolution

Abstract

Crocodilians show a high degree of cranial variation and convergence throughout their 80 million‐year fossil record that complicates their phylogenetic reconstruction. Conflicting phylogenetic results from different data partitions and character homoplasies typify crocodilian phylogeny, and differences between molecular and morphological phylogenetic hypotheses are believed to be associated with the slender‐snout skull shape of Gavialis gangeticus and Tomistoma schlegelii. Slender‐snout skulls are one of five identified eusuchian cranial ecomorph shape categories (ESCs) thought to reflect functional or ecological specialization. This paper tested the effect of transitions among general, blunt and slender ESCs on cranial character‐state distributions in phylogeny using the concentrated changes test. In addition, ‘tree‐free’ character compatibility analysis of character independence was conducted on the morphological character matrix to determine if character correlations are observed independent of specific tree topologies. Results suggest cranial ESCs do affect cranial character‐state gains in phylogeny. Concentrated changes identify a broad suite of character‐state changes that significantly correlate with transitions to slender, general and blunt ESCs on morphological, molecular and combined‐data tree topologies, but numbers of correlated characters for each category differ according to topology. Character compatibility analysis results do not mirror the concentrated changes test results and reflect hierarchically distributed support throughout the data. As cranial ESCs affect character‐state transitions, it is possible that nonphylogenetic variables could affect inferences of crocodilian phylogeny by affecting cranial morphology.

Phylogenetic Analysis of Pelecaniformes (Aves) Based on Osteological Data: Implications for Waterbird Phylogeny and Fossil Calibration Studies

“…Limnofregata is robustly supported as the sister taxon to modern frigatebirds in the present analysis (Figure 2). The characters supporting this clade are distributed throughout the entire avian skeleton, which argues against a close relationship being erroneously inferred due to ecomorphological convergence in a particular anatomical subregion [114]. In addition, many of the characters supporting a Limnofregata / Fregata clade are preserved in multiple specimens of Limnofregata , which provides confidence that character states have been accurately assessed, and cannot be attributed to taphononomic or preparation damage of an individual specimen (e.g., the distal fenestration of manual phalanx II-1).…”

Rapid scoring of genes in microbial pan-genome-wide association studies with Scoary

“…1–1 means an isolate that is positive for both the genotype variant and the phenotype) [18, 22]. Hence, under the null hypothesis, the phenotype has been randomly assigned as either 0 or 1 with p  = 0.5 for each possible outcome irrespective of the genotype.…”

Determinants of Habitat Selection by Hatchling Australian Freshwater Crocodiles

“…More importantly, hatchlings may be more vulnerable to predation in open habitats, based on the way that our own capture rates differed among habitat types. Although hatchlings inhabiting open banks could dive more easily than in the other habitats (unimpeded by vegetation), we nonetheless found them easier to capture because they could not escape to cover (hatchling crocodilians may seek shelter when under threat [51]). Similarly, hatchlings from grassy banks were easier to catch than those in vegetation mats.…”