A New Reconstruction Of Multituberculate Endocranial Casts And Encephalization Quotient Of Kryptobaatar

Title

A New Reconstruction Of Multituberculate Endocranial Casts And Encephalization Quotient Of Kryptobaatar

Creator

Kielan-Jaworowska Z; Lancaster T

Publisher

Acta Palaeontologica Polonica

Date

2004
2004-04

Description

Multituberculate and eutriconodontan endocasts differ from those of primitive therian mammals in their lack of visible midbrain exposure oil the dorsal side and in having a vermis-like triangular bulge (recognized herein as the cast of a large sinus-the superior cistern) inserted between the cerebral hemispheres. As the shape and proportions of multituberculate. eutriconodontan, and Cretaceous eutherian endocasts are otherwise similar, one might speculate that the multituberculate and eutriconodontan brains did not differ essentially from those of primitive eutherian and marsupial mammals, in which the midbrain is exposed dorsally. This conclusion might have important phylogenetic implications, as multituberculates and eutriconodontans may lay closer to the therians sensu strico, than hitherto believed. We describe an endocast of the Late Cretaceous multi tuberculate Kryptobaatar, which differs from those of other multituberculates (Ptilodus, Chulsan-baatar. and Nemegtbaatar) in having unusually long olfactory bulbs and the paraflocculi elongated transversely, rather than ball-shaped. We estimate the encephalization quotient (EQ) of Kryptobaatar, using: 1) Jerison's classical equation (1) based on estimation of endocranial volume and body mass-, 2) McDermott et al.'s derived body mass estimation equation (2) using upper molar lengths; and 3) estimation of body mass based on new equations (3a, 3b, 3c, and 3d(1-9)), which we propose, using measurements of the humerus, radius, ulna, femur and tibia. In both Jerison's method and a mean of out series of derived formulae, the EQ varies around 0.71, which is higher than estimated for other multituberculate mammals. It remains an open question whether the evolutionary success of Kryptobaatar (which was a dominant mammal during the ?early Campanian on the Gobi Desert and survived until the ?late Campanian) might have been related to its relatively high EQ and well developed sensorimotor adaptations, in particular olfaction and coordinated movements.

Subject

body mass; body-weight; brain; brain structure; cistern; encephalization quotient; endocasts; evolution; Kryptobaatar; Late Cretaceous; mammals; Mongolia; multituberculata; Paleontology; phylogeny; size; superior; tooth

Identifier

n/a

Format

Journal Article or Conference Abstract Publication

URL Address

n/a

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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).

Pages

177-188

Issue

2

Volume

49

Citation

Kielan-Jaworowska Z; Lancaster T, “A New Reconstruction Of Multituberculate Endocranial Casts And Encephalization Quotient Of Kryptobaatar,” NEOMED Bibliography Database, accessed September 18, 2021, https://neomed.omeka.net/items/show/10466.

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