The Endocranial Cavity of a Nonmammalian Eucynodont, Chiniquodon theotenicus, and Its Implications for the Origin of the Mammalian Brain

@inproceedings{Kemp2009TheEC,
  title={The Endocranial Cavity of a Nonmammalian Eucynodont, Chiniquodon theotenicus, and Its Implications for the Origin of the Mammalian Brain},
  author={Thomas Kemp},
  year={2009}
}
  • T. Kemp
  • Published 12 December 2009
  • Biology
ABSTRACT The braincase and endocranial cavity of a specimen of a nonmammalian eucynodont Chiniquodon is described and illustrated, and a tentative reconstruction of the gross anatomy of the brain offered. Salient features are the well-developed impression for the olfactory lobes, the extreme narrowness of the region available for the telencephalon, and the evidence for a large cerebellum. A two-step theory for the origin of the mammalian brain is proposed. The first step is represented by the… 
Endocranial Casts of Pre-Mammalian Therapsids Reveal an Unexpected Neurological Diversity at the Deep Evolutionary Root of Mammals
TLDR
This study suggests that NMT brain size falls in the upper range of the reptilian and amphibian variation, and uses micro-CT scans of the skulls of 1 Dinocephalia and 3 Biarmosuchia to enable the accurate determination of endocranial shape and size in NMT.
Reassessment of the Morphology and Paleobiology of the Therocephalian Tetracynodon Darti (Therapsida), And The Phylogenetic Relationships of Baurioidea
TLDR
The brain is strikingly plesiomorphic in many features, but generally shows features that are intermediate between gorgonopsians and cynodonts, thus clarifying this stage of the evolution of the synapsid brain.
Cranial anatomy of the early cynodont Galesaurus planiceps and the origin of mammalian endocranial characters
The cranial anatomy of the early non‐mammalian cynodont Galesaurus planiceps from the South African Karoo Basin is redescribed on the basis of a computed tomographic reconstruction of the skull.
Origin of the Lateral Wall of the Mammalian Skull: Fossils, Monotremes and Therians Revisited
TLDR
To interpret the fundamental differences in the structure and origin of the braincase sidewalls of monotremes, multituberculates, and therians, MicroCT scans of a mammaliaform, Morganucodon, and two non-mammalian cynodonts and Probainognathus were examined.
The mystery of a missing bone: revealing the orbitosphenoid in basal Epicynodontia (Cynodontia, Therapsida) through computed tomography
TLDR
Using micro-computed tomography (μCT), the internal morphology of the interorbital region that includes the rarely fossilized orbitosphenoid elements in four basal cynodonts is described.
Non-Mammalian Synapsids: The Beginning of the Mammal Line
TLDR
The anatomy of the middle ear region of the known sequence of fossil stem-group mammals—pelycosaurs, basal therapsids, and several cynodonts—is reviewed in this chapter and the interpretation offers support for the second view.
Digital cranial endocast of Riograndia guaibensis (Late Triassic, Brazil) sheds light on the evolution of the brain in non-mammalian cynodonts
TLDR
The data supports the hypothesis of the neurological evolution of the mammalian lineage starting with a trend for an increase of the olfactory bulbs, which is associated with adaptations in the nasal cavity, and suggests an initial improvement of the sensory receptor system leading to further development of the ‘superior’ structures for sensorial processing and integration.
Study of a digital cranial endocast of the non-mammaliaform cynodont Brasilitherium riograndensis (Later Triassic, Brazil) and its relevance to the evolution of the mammalian brain
TLDR
The proposition of an early evolution of the mammalian brain associated with selective pressures for better sensorial acuity is supported, especially regarding improved olfaction, which began with small Triassic mammaliamorphs.
Evidence for convergent evolution of a neocortex‐like structure in a late Permian therapsid
TLDR
The gross anatomy of the brain endocast of Kawingasaurus supports the Outgroup Hypothesis, according to which the neocortex evolved from the dorsal pallium of an amphibian‐like ancestor, which receives sensory projections from the lemnothalamic pathway.
On the development of the chondrocranium and the histological anatomy of the head in perinatal stages of marsupial mammals
TLDR
Comparative studies of chondocranial development of mammals can benefit from a solid phylogenetic framework, research on non-classical model organisms, and integration with imaging and sectional data derived from computer-tomography.
...
...

References

SHOWING 1-10 OF 55 REFERENCES
The brain of the mammal-like reptile Probainognathus jenseni (Therapsida, Cynodontia). A correlative paleo-neoneurological approach to the neocortex at the reptile-mammal transition.
TLDR
The quantitative analysis of Probainognathus' endocast, as well as those of other cynodonts, suggest that certain cynodronts of the Middle Triassic were in an advanced state toward endothermy, and the histostructure of the neocortex at this state of the evolution may have been in a proisocortical-isOCortical stage.
The endocranial cast of the advanced mammal-like reptile Therioherpeton cargnini (Therapsida-Cynodontia) from the Middle Triassic of Brazil.
TLDR
The morphology of the endocast and relative brain size of Therioherpeton cargnini are in general agreement with other features of the species that locates it as one of the more advanced cynodont toward mammalian patterns, and this may imply that the brain does not evolved more conservatively than other characters at the reptile-mammal transition.
The endocranial cast of the advanced mammal-like reptile Therioherpeton cargnini (Therapsida-Cynodontia) from the Middle Triassic of Brazil.
TLDR
The morphology of the endocast and relative brain size of Therioherpeton cargnini are in general agreement with other features of the species that locates it as one of the more advanced cynodont toward mammalian patterns, and this may imply that the brain does not evolved more conservatively than other characters at the reptile-mammal transition.
The brain of two mammal-like reptiles (Cynodontia - Therapsida).
: The endocasts of the cynodonts Massetognathus sp. and cf. Probelesodon are studied from descriptive and quantitative viewpoints. The morphology of the casts is described briefly, doing special
The brain of two mammal-like reptiles (Cynodontia - Therapsida).
The endocasts of the cynodonts Massetognathus sp. and cf. Probelesodon are studied from descriptive and quantitative viewpoints. The morphology of the casts is described briefly, doing special
Whaitsiid Therocephalia and the origin of cynodonts
TLDR
It is argued that the organization of the cynodont skull can be seen as a logical functional development from the more primitive condition, and in particular, the streptostylic nature of the jaw articulation, the enlargement of the dentary and reduction of the postdentary bones, may all be correlated with the development of a masseter muscle.
The Primitive Cynodont Procynosuchus: Functional Anatomy of the Skull and Relationships
TLDR
The anatomy of the internal nares indicates that an arrangement of Jacobson’s organ and associated nerves, blood vessels and glands comparable to that of monotremes was present and an attempt is made to interpret its anatomy in functional terms.
Description of a Cranial Endocast from the Fossil Mammal Vincelestes neuquenianus (Theriiformes) and its Relevance to the Evolution of Endocranial Characters in Therians
TLDR
This report represents the first description of an endocast from a stem therian that is near crown group Theria, a Cretaceous theriiform mammal from Argentina, and examines 21 morphological characters related to the morphology of endocasts and endocranial osteology across 19 taxa to identify potential synapomorphies for Theria.
The skull of Morganucodon
TLDR
Two species of triconodont (atherian) mammal from the Lower Jurassic are described: M. oehleri from China and M. watsoni from Wales; the systematic position of Morganucodon is discussed.
...
...