The development of distinct regions in the amniote vertebral column results from somite formation and Hox gene expression, with adult morphology displaying remarkable variation among lineages. Mammalian regionalization is reportedly very conservative or even constrained, but there has been no study investigating count across Amniota as a whole, undermining attempts to understand phylogenetic, ecological, developmental factors affecting variation. Here, we show that mammalian (synapsid)...

The multiple skeletal components of the skull originate asynchronously and their developmental schedule varies across amniotes. Here we present embryonic ossification sequence 134 species, covering all major groups mammals close relatives. This comprehensive data set allows reconstruction heterochronic modular evolution condition last common ancestor mammals. We show that mode (dermal or endochondral) unites bones into integrated evolutionary modules changes imposes constraints on cranial...

The phylogenetic position of turtles is the most disputed aspect in reconstruction land vertebrate tree life. This controversy has arisen after many different kinds and revisions investigations molecular morphological data. Three main hypotheses living sister-groups have resulted from them: all reptiles, crocodiles + birds or squamates tuatara. Although embryology played a major role studies phylogeny, data on developmental timing never been examined to explore test alternative hypotheses....

Sea turtles (Chelonoidea) are a charismatic group of marine reptiles that occupy range important ecological roles. However, the diversity and evolution their feeding anatomy remain incompletely known.

In the past few years, new fossil finds and novel methodological approaches have prompted intensive discussions about phylogenetic affinities of turtles rekindled debate on their ecological origin, with very distinct scenarios, such as fossoriality aquatic habitat occupation, proposed for earliest stem-turtles. While research has focused largely origin anapsid skull unique postcranial anatomy, little is known endocranial anatomy turtles. Here, we provide 3D digital reconstructions...

Staged embryonic series are important as reference for different kinds of biological studies. I summarise problems that occur when using 'staging tables' 'model organisms'. Investigations developmental processes in a broad scope taxa becoming commonplace. Beginning the 1990s, methods were developed to quantify and analyse events phylogenetic framework. The algorithms associated with these still under development, mainly due difficulties non-independent characters. Nevertheless, principle...

Abstract Using the Standard Event System (SES) to study patterns of vertebrate development, we describe a series 17 embryos pleurodire turtle Emydura subglobosa . Based on sequence heterochrony analysis including 23 tetrapod taxa, identified autapomorphic developmental shifts that characterise Testudines, Cryptodira, and Pleurodira. The main results are Testudines characterised by an late neck whereas pleurodires cryptodires show different timing mandibular process. Additionally, described...

Up to this date, no clear common reference system for muscle nomenclature in vertebrates exists due 1. human medical anatomy dominated traditions, 2. typological, 'box-like' approaches, and 3. simplifications based on the taxonomic topographical focus of respective authors. Hence, a large terminological homologisation confusion literature is recognisable, hindering evolutionary developmental analyses. In paper, comprehensive study cranial musculature presented, which more than 100 references...

Abstract Chelonioid turtles are the only surviving group of reptiles that secondarily evolved marine lifestyles during Mesozoic Early chelonioid evolution is documented by fossils their stem group, such as protostegids, which yield insights into adaptation. Neuroanatomical features commonly used to infer palaeoecology owing functional adaptation senses an organism its environment. We investigated neuroanatomy and carotid circulation early Late Cretaceous protostegid Rhinochelys pulchriceps...

The unique ability of modern turtles to retract their head and neck into the shell through a side-necked (pleurodiran) or hidden-necked (cryptodiran) motion is thought have evolved independently in crown turtles. anatomical changes that led vertebral shapes turtles, however, are still poorly understood. Here we present comprehensive geometric morphometric analyses trace turtle evolution reconstruct disparity across phylogeny. Disparity shape was high at dawn decreased after groups evolved,...

ABSTRACT The article reports on the first detailed vertebral and rib morphology of anguine taxon Pseudopus apodus using micro‐computed tomography. A comparison shows significant morphological differences vertebrae relative to those Anguis Ophisaurus. Usually, there are 55 presacral vertebrae, two sacral, 95–97 caudal vertebrae. can be defined by 23 diagnostic features concerning column. Although zygapophyseal articulation between atlas axis is well developed in limbed anguid gerrhonotine...

Abstract The origin of turtles is one the most long-lasting debates in evolutionary research. During their evolution, a series modifications changed relatively kinetic and anapsid skull into an elongated akinetic structure with unique pulley system redirecting jaw adductor musculature. These were thought to be strongly correlated functional adaptations, especially bite performance. We conducted Finite Element Analyses (FEAs) several species, including that oldest fully shelled, Triassic...

Abstract The labyrinth of the vertebrate inner ear is a sensory system that governs perception head rotations. Central hypotheses predict shape and size are related to ecological adaptations, but this under debate has rarely been tested outside mammals. We analyze evolution morphology its drivers in living fossil turtles, an understudied group underwent multiple locomotory transitions during 230 million years evolution. show turtles have unexpectedly large labyrinths evolved origin aquatic...

Abstract The complex constructions of land vertebrate skulls have inspired a number functional analyses. In the present study, we provide basic view on skull biomechanics and offer framework for more general observations using advanced modeling approaches in future. We concentrate our discussion cranial openings temporal region work out two major, feeding‐related factors that largely influence shape skull. argue (1) place where most forceful biting is conducted (2) handling resisting food...

ABSTRACT Turtles have the unparalleled ability to retract their heads and necks within shell but little is known about evolution of this trait. Extensive analysis neck mobility in turtles using radiographs, CT scans, morphometry reveals that basal possessed less relative extant relatives, although anatomical prerequisites for modern were already established. Many are able achieve hypermobility by dislocating central articulations, which raises cautions reconstructing fossil vertebrates. A...

Snakes possess a derived anatomy, characterized by limb reduction and reorganization of the skull internal organs. To understand origin snakes from an ontogenetic point view, we conducted comprehensive investigations on timing skeletal elements, based published new data, reconstructed evolution ossification sequence among squamates. We included for first time Varanus, critical taxon in phylogenetic context. There is delay onset most elements when compared to reference developmental events...

Mammals feature not only great phenotypic disparity, but also diverse growth and life history patterns, especially in maturity level at birth, ranging from altriciality to precocity. Gestation length, morphology other markers of are fundamental our understanding mammalian evolution. Based on the first synthesis embryological data study new ontogenetic series, we reconstructed estimates ancestral chronology organogenesis life-history modes placental mammals. We found that ancestor marsupial...

Abstract In recent years, paleoneurology became a very popular research field and hundreds of brain-endocasts were described. The interpretation dorsal protuberance the brain-endocast puzzled researchers for long time, so-called (cartilaginous) rider. This is mainly because technical limitations in past due to non-accessibility comparative material. Using turtles as case-study, we conducted literature review studied embryological data addition fossil extant species’ endocasts. We assessed...

The anterior end of the mammalian face is characteristically composed a semimotile nose, not upper jaw as in other tetrapods. Thus, therian nose covered ventrolaterally by "premaxilla," and osteocranium possesses only single nasal aperture because absence medial bony elements. This stands contrast to those tetrapods whom premaxilla covers rostral terminus snout, providing key understanding evolution face. Here, we show that mammals (placentals marsupials) entirely homologous amniotes;...

ABSTRACT A diagnostic feature of temnospondyls is the presence an open palate with large interpterygoid vacuities, unlike closed most other early tetrapods, in which vacuities are either slit‐like or completely absent. Attachment sites on neurocranium and palatal bones allow reconstruction a powerful m. retractor bulbi large, sheet‐like levator that formed elastic floor orbit. This muscle arrangement indicates were able to retract eyeballs through into buccal cavity, like extant frogs...