Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy

  title={Inner ear biomechanics reveals a Late Triassic origin for mammalian endothermy},
  author={Ricardo Ara{\'u}jo and Romain David and Julien Benoit and Jacqueline K. Lungmus and Alexander Stoessel and Paul M. Barrett and Jessica A Maisano and Eric G Ekdale and Maeva Judith Orliac and Zhe‐Xi Luo and Agustín G. Martinelli and Eva A. Hoffman and Christian A. Sidor and Rui M. S. Martins and Fred Spoor and Kenneth D. Angielczyk},
  pages={726 - 731}
Endothermy underpins the ecological dominance of mammals and birds in diverse environmental settings1,2. However, it is unclear when this crucial feature emerged during mammalian evolutionary history, as most of the fossil evidence is ambiguous3–17. Here we show that this key evolutionary transition can be investigated using the morphology of the endolymph-filled semicircular ducts of the inner ear, which monitor head rotations and are essential for motor coordination, navigation and spatial… 

Revisiting life history and morphological proxies for early mammaliaform metabolic rates

Availabledata suggest that metabolic rates play little role in affecting longevity within and between tetrapod classes once the effects of body size are properly accounted for, and contend that high longevity cannot be taken as a proxy for low metabolic rates.

Evolution of thermoregulation as told by ear

An analysis of fossil specimens of the inner ear helps to refine the timeframe of a key transition in vertebrate evolution — when our mammal-like ancestors began to regulate and maintain a high body

First evidence of the link between internal and external structure of the human inner ear otolith system using 3D morphometric modeling

These data provide the first evidence that external structure of the human otolith system is directly related to internal anatomy, suggesting a basic biological relationship, and create a 3D morphometric model visualizing bony and membranous structure.

The ecology and evolution of key innovations.

Diphyodont tooth replacement of Brasilodon—A Late Triassic eucynodont that challenges the time of origin of mammals

Two sets of teeth (diphyodonty) characterise extant mammals but not reptiles, as they generate many replacement sets (polyphyodonty). The transition in long‐extinct species from many sets to only two



A phenology of the evolution of endothermy in birds and mammals

  • B. Lovegrove
  • Environmental Science
    Biological reviews of the Cambridge Philosophical Society
  • 2017
Recent palaeontological data and novel physiological hypotheses now allow a timescaled reconstruction of the evolution of endothermy in birds and mammals. A three‐phase iterative model describing how

Reptile-like physiology in Early Jurassic stem-mammals

It is reported, using synchrotron X-ray tomographic imaging of incremental tooth cementum, that the Early Jurassic Morganucodon and Kuehneotherium had maximum lifespans considerably longer than comparably sized living mammals, but similar to those of reptiles, and so they likely had reptilian-level basal metabolic rates.

New tools suggest a middle Jurassic origin for mammalian endothermy

We suggest that mammalian endothermy was established amongst Middle Jurassic crown mammals, through reviewing state‐of‐the‐art fossil and living mammal studies. This is considerably later than the

Inner Ear Morphology in the Atlantic Molly Poecilia mexicana—First Detailed Microanatomical Study of the Inner Ear of a Cyprinodontiform Species

The inner ear of the cyprinodontiform freshwater fish Poecilia mexicana is studied by analyzing the position of otoliths in situ, investigating the 3D structure of sensory epithelia, and examining the orientation patterns of ciliary bundles of the sensory hair cells, while combining μ-CT analyses, scanning electron microscopy, and immunocytochemical methods.

A caseian point for the evolution of a diaphragm homologue among the earliest synapsids

The paleobiology and the respiratory apparatus of one of the oldest lineages of mammal‐like reptiles: the Caseidae is analyzed and it is deduced that a homologue of the mammalian diaphragm had already evolved about 50 Ma earlier than previously assumed.

Palaeoneurological clues to the evolution of defining mammalian soft tissue traits

The presence of a true infraorbital canal in Prozostrodontia suggests that a motile rhinarium and maxillary vibrissae were present and the complete ossification of the parietal fontanelle and the development of the cerebellum in Probainognathia may be pleiotropically linked to the appearance of mammary glands and having body hair coverage.

Neurovascular anatomy of the protostegid turtle Rhinochelys pulchriceps and comparisons of membranous and endosseous labyrinth shape in an extant turtle

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Energy Homeostasis in Monotremes

Although echidnas show very large seasonal variations in fat stores associated with hibernation there is no relationship between plasma leptin and adiposity, supporting suggestions that in evolutionary terms the anorectic effects of leptin preceded the adiposity signal.

Structural variation in the inner ears of four deep‐sea elopomorph fishes

The shape of the sensory epithelia and hair cell ciliary bundle orientation of the saccule, lagena, and utricle, the three otolithic organs associated with audition and vestibular function, are described and it is suggested that the lagena has special adaptations in these species.