The telencephalon of tetrapods in evolution

Area of Science:

• Comparative neuroanatomy
• Evolutionary biology
• Developmental neuroscience

Background:

• Establishing homology between mammalian isocortex and sauropsid pallium has been challenging due to significant differences in adult brain organization.
• Previous phylogenetic analyses were inconclusive because mammals and sauropsids are sister groups, hindering discrimination between alternative homology hypotheses.

Purpose of the Study:

• To resolve conflicting theories on pallial homologies between sauropsids and mammals by incorporating embryological data.
• To propose a refined set of homologies for key telencephalic structures based on comparative embryology and phylogenetic analysis.

Main Methods:

• Comparative analysis of pallial organization incorporating early developmental (embryological) patterns.
• Phylogenetic analysis based on parsimony to validate proposed homologies.

Main Results:

• Identified homologies: Reptilian lateral cortex to mammalian piriform cortex; anterior dorsal ventricular ridge to neostriatum/ventral hyperstriatum/endopiriform nucleus; posterior dorsal ventricular ridge to archistriatum/pallial amygdala; pallial thickening to hyperstriatum/claustrum; dorsal cortex to accessory hyperstriatum/parahippocampal area/isocortex.
• These homologies suggest minor developmental changes but significant alterations in neuronal connections and independent evolution of sensory projections and pallial lamination.

Conclusions:

• Embryological data provides crucial insights for resolving complex homology debates in comparative neuroanatomy.
• The proposed homologies offer a more robust framework for understanding the evolution of the mammalian isocortex and sauropsid pallial structures.