The Endocranial Cast of Indohyus (Artiodactyla, Raoellidae): The Origin of the Cetacean Brain

Title

The Endocranial Cast of Indohyus (Artiodactyla, Raoellidae): The Origin of the Cetacean Brain

Creator

Orliac MJ; Thewissen JGM

Publisher

Journal Of Mammalian Evolution

Date

2021

Description

We present the first description of the endocranial cast of the small raoellid artiodactyl Indohyus indirae. Raoellidae are sister group to Cetacea and the new morphological observations allow for outlining some of the early steps of the evolutionary history of the cetacean brain. The combination of primitive artiodactyl features and typical cetacean characters is unique about the Indohyus endocast. The fact that it presents the symplesiomorphic brain pattern observed in earliest Artiodactyla indicates that the cetacean brain derives from a very simple, plesiomorphic brain, with simple neocortical folding pattern, widely exposed midbrain, and concurrent small neocortex expansion. On the other hand, the Indohyus endocast shows characters that also occur in early cetaceans. These include modifications of the olfactory tract with narrow, elongated olfactory bulbs and peduncles, accompanied by a posterior location of the braincase in the cranium. The derived endocranial cast features of Indohyus mainly reflect changes in cranial architecture and these are most probably associated with modifications of the masticatory apparatus and a shift in diet. Indohyus meninges were very thin like in most terrestrial artiodactyls and it had no extensive rostral or lateral retia mirabilia. It however shows a branching pattern of ramification of intraosseous blood sinuses above the cerebellum that might represent the initial development of the caudal venous rete mirabile that would have colonized the endocranial cavity later on, in early archaeocetes.

Subject

Eocene; Cetacea; Brain; CT scan; Endocast

Rights

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

Format

journalArticle

Search for Full-text

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ISSN

1064-7554

NEOMED College

NEOMED College of Medicine

NEOMED Department

Department of Anatomy & Neurobiology

Update Year & Number

May 2021 List

Citation

Orliac MJ; Thewissen JGM, “The Endocranial Cast of Indohyus (Artiodactyla, Raoellidae): The Origin of the Cetacean Brain,” NEOMED Bibliography Database, accessed August 5, 2021, https://neomed.omeka.net/items/show/11648.

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