An extinct deep-snouted Alligator species from the Quaternary of Thailand and comments on the evolution of crushing dentition in alligatorids.

Fossil Alligator remains from Asia are critical for tracing the enigmatic evolutionary origin of the Chinese alligator, Alligator sinensis, the only living representative of Alligatoridae outside the New World. The Asian fossil record is extremely scarce and it remains unknown whether A. sinensis is an anagenetic lineage or alternatively, extinct divergent species were once present. We provide a detailed comparative description of a morphologically highly distinct Alligator skull from the Quaternary of Thailand. Several autapomorphic characters warrant the designation of a new species. Alligator munensis sp. nov. shares obvious derived features with A. sinensis but autapomorphies imply a cladogenetic split, possibly driven by the uplift of the southeastern Tibetan plateau. The presence of enlarged posterior alveoli in Alligator munensis is most consistent with a reversal to the alligatorine ancestral condition of having crushing dentition, a morphology strikingly absent among living alligatorids. Crushing dentition has been previously considered to indicate an ecological specialisation in early alligatorines that was subsequently lost in Alligator spp. However, we argue that there is yet no evidence for crushing dentition reflecting an adaptation for a narrower niche, while opportunistic feeding, including seasonal utilisation of hard-shelled preys, is a reasonable alternative interpretation of its function.

The impact of molecular data on the phylogenetic position of the putative oldest crown crocodilian and the age of the clade.

The use of molecular data for living groups is vital for interpreting fossils, especially when morphology-only analyses retrieve problematic phylogenies for living forms. These topological discrepancies impact on the inferred phylogenetic position of many fossil taxa. In Crocodylia, morphology-based phylogenetic inferences differ fundamentally in placing Gavialis basal to all other living forms, whereas molecular data consistently unite it with crocodylids. The Cenomanian Portugalosuchus azenhae was recently described as the oldest crown crocodilian, with affinities to Gavialis, based on morphology-only analyses, thus representing a potentially important new molecular clock calibration. Here, we performed analyses incorporating DNA data into these morphological datasets, using scaffold and supermatrix (total evidence) approaches, in order to evaluate the position of basal crocodylians, including Portugalosuchus. Our analyses incorporating DNA data robustly recovered Portugalosuchus outside Crocodylia (as well as thoracosaurs, planocraniids and Borealosuchus spp.), questioning the status of Portugalosuchus as crown crocodilian and any future use as a node calibration in molecular clock studies. Finally, we discuss the impact of ambiguous fossil calibration and how, with the increasing size of phylogenomic datasets, the molecular scaffold might be an efficient (though imperfect) approximation of more rigorous but demanding supermatrix analyses.

3D skull modelling and description of a new baurusuchid (Crocodyliformes, Mesoeucrocodylia) from the Late Cretaceous (Bauru Basin) of Brazil.

Baurusuchidae is one of the most diverse groups of South American notosuchians, unambiguously recorded in Late Cretaceous deposits of Brazil and Argentina. The group is characterized by a reduced tooth formula, a lateromedially compressed rostrum, and a verticalized quadrate, representing one of the top predators of their faunas. Historically, skull morphology is the most employed tool to investigate the relationships of baurusuchids, as most of the species have been primarily based on cranial remains. The present study describes a new baurusuchid species from the Bauru Basin of Brazil, based on the first tridimensional digital reconstruction of individualized skull bones for Notosuchia, and discusses its phylogenetic position within the group. The new species differs from all the other known baurusuchids by a depression on the posterior portion of the nasal bearing a crest, an infraorbital crest of the jugal that extends until the anterior margin of the lacrimal, the dorsal surface of the frontal lacking a longitudinal crest or depression, and the lateral convexity of the squamosal prongs participating in the occipital wall. The new taxon is consistently positioned as sister to the remaining baurusuchines, with Aplestosuchus sordidus and Stratiotosuchus maxhechti, as successive sister-taxa to a monophyletic Baurusuchus (Ba. albertoi, Ba. Salgadoensis, and Ba. pachecoi). Our updated phylogenetic analysis helps to differentiate the two major Baurusuchidae lineages, Baurusuchinae and Pissarrachampsinae. Yet, the new species shares morphological features with both groups, suggesting the occurrence of "Zones of Variability" in the radiation of Baurusuchidae.

Moenkhausia lepidura (Kner, 1858) (Characiformes, Characidae): osteology and relationships / Moenkhausia lepidura (Kner, 1858) (Characiformes, Characidae): osteologia e relações de parentesco

Abstract Cladistic analysis of fishes are mostly based on osteological studies. Phylogenetic relationships within the family Characidae are poorly known in part due to the lack of anatomical studies of its members, including osteology. The present contribution aims to offer a detailed description of all bony complexes of Moenkhausia lepidura. Two remarkable morphological conditions present in the species are discussed: a bony lamella on the proximal portion of the ribs and a basal expansion of the gill rakers. A morphological survey of several species of Characidae along with available phylogenetic information of the family indicates the putative relationships of Moenkhausia lepidura with other small characids presenting bony lamella on ribs and a dark mark on the caudal fin.

Resumo Análises cladísticas morfológicas de peixes são, em grande parte, baseadas em estudos osteológicos. As relações filogenéticas em Characidae são pouco conhecidas, em parte devido à falta de estudos anatômicos de seus representantes, incluindo a osteologia. O presente estudo tem por objetivo oferecer uma descrição detalhada dos complexos ósseos de Moenkhausia lepidura. Duas condições morfológicas notáveis presentes na espécie são discutidas: uma lamela óssea na porção proximal das costelas e uma expansão basal dos rastros branquiais. Um estudo morfológico de diversas espécies de Characidae, juntamente com informações filogenéticas disponíveis na família, indica a possível relação de M. lepidura com pequenos caracídeos que apresentam lamelas ósseas nas costelas e marcas escuras na nadadeira caudal.