Independent Origins of Middle Ear Bones in Monotremes and Therians

  title={Independent Origins of Middle Ear Bones in Monotremes and Therians},
  author={Thomas H. Rich and James A. Hopson and Anne M. Musser and Tim Fridtjof Flannery and Pat Vickers-Rich},
  pages={910 - 914}
A dentary of the oldest known monotreme, the Early Cretaceous Teinolophos trusleri, has an internal mandibular trough, which in outgroups to mammals houses accessory jaw bones, and probable contact facets for angular, coronoid, and splenial bones. Certain of these accessory bones were detached from the mandible to become middle ear bones in mammals. Evidence that the angular (homologous with the mammalian ectotympanic) and the articular and prearticular (homologous with the mammalian malleus… 

A cranio-incudo joint as the solution to early birth in marsupials and monotremes

It is shown that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation.

Comment on "Independent Origins of Middle Ear Bones in Monotremes and Therians" (I)

The middle ear ossicles of all extant, adult members of crown-group Mammalia are homologous with a series of bones in the lower jaw of nonmammalian amniotes, suggesting that the structurally complex mammalian ear evolved independently.

Homoplasy in the Mammalian Ear

A new fossil-the dentary bone of an ancient toothed monotreme-suggests that the middle ear bones formed independently in these two mammalian lineages, providing a remarkable example of homoplastic evolution.

Transient role of the middle ear as a lower jaw support across mammals

It is shown that this vital function is carried out by the earlier developing, cartilaginous incus of the middle ear, abutting the cranial base to form a cranio-mandibular articulation.

Response to Comments on "Independent Origins of Middle Ear Bones in Monotremes and Therians"

W e stand by our assessment of the taxonomic identity of Teinolophos trusleri and maintain that this specimen shows features that support an independent evolution of the middle ear in living

A new eutriconodont mammal and evolutionary development in early mammals

A Mesozoic eutriconodont nested within crown mammals that clearly illustrates this transition: the middle ear bones are connected to the mandible via an ossified Meckel’s cartilage, adding to the evidence of homoplasy of vertebral characters in the thoraco-lumbar transition and unfused lumbar ribs among early mammals.

Tongues untied

On page 276 of this issue, Zhou et al. (1) report on a newly discovered 165-million-year-old fossil from China in which the bones of the first three pharyngeal arches are preserved and define a new taxon named Microdocodon.

On the phylogenetic position of monotremes (Mammalia, Monotremata)

The Jurassic shuotheriid Pseudotribos shows a great plesiomorphic similarity to monotremes in the structure of the pectoral girdle, with a large interclavicle immovably connected to the clavicle.

Disconnecting bones within the jaw‐otic network modules underlies mammalian middle ear evolution

The analysis allows the identification of three types of anatomical modules evolving through five evolutionary stages during the anatomical transformation of the jawbones into middle ear bones, with the ossification and degradation of Meckel's cartilage in mammals as the key ontogenetic event leading the change of anatomical modularity.

Evolutionary Development of the Middle Ear in Mesozoic Therian Mammals

A Cretaceous trechnotherian mammal with an ossified Meckel’s cartilage in the adult is reported, showing that homoplastic evolution of the DMME occurred in derived therian mammals, besides the known cases of eutriconodonts.



An Ossified Meckel's Cartilage in Two Cretaceous Mammals and Origin of the Mammalian Middle Ear

The evidence shows that brain expansion may not be the initial factor that caused the separation of postdentary bones from the dentary as middle ear ossicles during mammalian evolution.

Monotreme affinities and low-frequency hearing suggested by multituberculate ear

The discovery of a multituberculate ectotympanic bone, associated with the malleus in original life position, from two exquisitely preserved auditory regions, documents incorporation of the angular and prearticular bones into the middle ear of multituberculated mammals, favouring the hypothesized single origin of the ossicular chain in mammals.

A Chinese triconodont mammal and mosaic evolution of the mammalian skeleton

The derived pectoral girdle of this new triconodont indicates that homoplasies are as common in the postcranial skeleton as they are in the skull and dentition in the evolution of Mesozoic mammals.

The origin of egg-laying mammals

Steropodon appears to have been derived from therians before the development of tribosphenic teeth, possibly during the Jurassic period, and radically alters currently held opinion that monotremes and therians diverged at the earliest stage of mammalian evolution.

The ossified Meckel's cartilage and internal groove in Mesozoic mammaliaforms: implications to origin of the definitive mammalian middle ear

These specimens provide direct evidence for the function of the internal groove which is commonly present in the dentary of early mammals and their relatives and supports the assumption that a persistent or ossified Meckel's cartilage has been present in adults of the common ancestor of mammals.

Dual origin of tribosphenic mammals

Phylogenetic and morphometric analyses including these newly discovered taxa suggest a different interpretation: that mammals with tribosphenic molars are not monophyletic.

Haramiyids and Triassic mammalian evolution

The discovery of haramiyid dentaries, a maxilla and other skeletal remains in the Upper Triassic of East Greenland revealsHaramiyids as highly specialized mammals with a novel pattern of puncture-crushing occlusion that differs dramatically from the grinding or shearing mechanisms of other Early Mesozoic mammals.

The lower jaw of Morganucodon

The genus Morganucodon is found in Yunnan, China, in normal (non-karstic) sedimentary deposits of probable Rhaetian age; and in Wales in karstic deposits in the Carboniferous Limestone, which cannot be younger than Sinnemurian or older than Rhaetic.

New information about the skull and dentary of the Miocene platypus Obdurodon dicksoni, and a discussion of ornithorhynchid relationships.

  • A. MusserM. Archer
  • Medicine
    Philosophical transactions of the Royal Society of London. Series B, Biological sciences
  • 1998
Differences in the relative positions of cranial structures, and in the relationships of certain cranial foramina, indicate that the cranium may have become secondarily shortened in Or.